Flow Assisted Vascular Surgery

Quality Care

Transonic

FlowQ C

®

Quantitative Flow Measurementsfor Functional Assessmentduring Vascular Surgery

Flow Assisted

Vascular Surgery

Transonic Systems Inc.The Flow Measurement Specialists

FMV-Series Vascular Short Handle-Flowprobeflash

©2005 by Transonic Systems Inc.Printed in the United States of America

ISBN: 0-9744152-2-7

Transonic®, Flow-QC® and Transonic Flow-QC®

are registered trademarks of Transonic Systems Inc.

This handbook is an educational service by Transonic Systems Inc.,Cornelis J. Drost, publisher; Susan Eymann, editor. All rights reserved. Nopart of this handbook may be reproduced, stored in a retrieval system, ortransmitted in any form, or by any means, electronic, mechanical,photocopying, recording, or otherwise, without prior written permission ofTransonic Systems Inc.

Copies of this handbook may be ordered from Transonic Systems Inc. Tel: 1-800-353-FLOW (3569) (USA); 607-257-5300

Fax: 607-257-7256; Web: www.transonic.com

This handbook presents intraoperative blood flowmeasurement during vascular surgery with transit-timeultrasound flowmetry. Adequate distal outflow is tantamountto the functional success of vascular surgery and to apatient’s immediate recovery. This surgical success isfacilitated when quantitative hemodynamic effects can beconsidered during vascular surgical management.

• • •

bVASCULAR SURGERY HANDBOOK

ML-60, REV. A, 9-05TRANSONIC SYSTEMS INC.FLOW MEASUREMENT SPECIALISTS

i TRANSONIC SYSTEMS INC.FLOW MEASUREMENT SPECIALISTS

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FFllooww--AAssssiisstteedd VVaassccuullaarr SSuurrggeerryyQuantitative Flow Measurements

for Functional Assessments during Vascular Surgery

A. Introduction Surgeons’ Reports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Blood Flow Measurement during Surgery . . . . . . . . . . . . . . . . . . . . . . 2

Why Measure Flow? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

B. Measuring Flow during Vascular Surgery . . . . . . . . . . . . . . . . . . . . . . 5

C. Flow-QC® Vascular Applications . . . . . . . . . . . . . . . . . . . . . . . . . . 6

1. AV Accessa. Flow-Assisted AV Fistula Access Construction . . . . . . . . . . . . . . 7

b. Flow-Assisted AV Graft Construction . . . . . . . . . . . . . . . . . . . . . 9

c. Flow-Guided AV Access Revision . . . . . . . . . . . . . . . . . . . . . . . 11

d. Flow-QC Benefits for AV Access Surgery . . . . . . . . . . . . . . . . . 12

2. Peripheral Bypass Surgerya. Flow-Assisted Lower Extremity Bypass Surgery . . . . . . . . . . . . 13

b. Flow-Assisted Fem-Pop Surgical Approaches . . . . . . . . . . . . . 14

c. Flow-QC Benefits during Lower Extremity Bypass Surgery . . . . 17

d. Case Studies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

3. Carotid Endarterectomya. Flow-Assisted Carotid Endarterectomy . . . . . . . . . . . . . . . . . . . 19

b. Medical Note Ian Gordon, MD, PhD . . . . . . . . . . . . . . . . . . . . . . 21

c. Flow-QC Benefits during Carotid Endarterectomy . . . . . . . . . . 22

D. Frequently Asked Questions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

E. Vascular Flow References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Transonic Systems Inc.www.transonic.com

1 TRANSONIC SYSTEMS INC.FLOW MEASUREMENT SPECIALISTS


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In many surgical disciplines, blood flow (or the lack thereof) has a profound impact onsurgical success and long-term patient health. As a consequence, flow should bemeasured during such surgeries to assure the quality of surgery, and improve surgicaloutcomes.

Surgeons’ Reports “As a vascular surgeon you are continually striving to do the best possible operation tailored tothe specific findings of a particular patient. You are trying to do the best with what you’ve got.Consequently, during surgery you are constantly re-assessing its progress to try to give thepatient the best long-term result.

Any technology that you can use to provide an intraoperative assessment can be invaluable.Transonic Flow-QC intraoperative blood flow measurement is such a measurement. Themeasurements may either confirm what appears to be an acceptable surgical result, or it canalert you that there may be potential problems at a time when it can be more easily addressed.The assessment may dictate an immediate major revision or a change in the postoperativetreatment such as the addition of long-term anticoagulation.

Transonic Flow-QC provides a measurable improvement in the quality of care you can extend toyour patients. With Transonic Flow-QC you can: improve patient outcomes; reduce or delay theneed for future interventions and document surgical results.”

T. Wolvos, MD, FACS Scottsdale Healthcare, Scottsdale, AZ

"The primary aim of intraoperative volume flow measurement is to obtain information on theimmediate result of the reconstruction where a technical failure may jeopardize an otherwisesuccessful operation."

Lundell A, Bergqvist D. Intraoperative Flow Measurements in Vascular Reconstruction. Ann Chir Gynaecol

81(2):187-191, 1992

“The flow measurement is very helpful and we use it in all our cases.”

-G. Steinporsson, MD, 2000

“Intraoperative assessment of graft patency is essential for detection of potentially reversibletechnical problems prior to leaving the operating room.”

- Chun et al, Heart Surgery Forum 2(3):230-234, 1999

VASCULAR SURGERY HANDBOOK

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Blood Flow Measurement during Surgery

From a blood flow measurement perspective, we distinguish two groups ofsurgery. Blood flow measurement is implemented differently in these twocategories of surgery.

FLOW-GUIDED SURGICAL

TECHNIQUES————————————

In these surgeries, the sole purpose ofthe surgery is to correct a blood flowdeficiency (e.g., CABG, Fem-Pop bypass

surgery), or create a certain blood flowpattern (e.g.: an arterio-venous fistula).

OBJECTIVEThe primary objective of this surgerycan be expressed in terms of bloodflow, such as: “create an AV Fistula toenable hemodialysis in this patient at aflow rate of 350 ml/min,” “augmentcoronary flow to a myocardium thatrequires 40 ml/min at rest, 120 ml/minduring exercise.” One would expect thatthe surgeon starts the surgicalprocedure with a blood flow goal, andmeasures flow during surgery to confirmthat the goal has been reached.

FLOW-ASSISTED SURGICAL

TECHNIQUES—————————————

Here, the purpose of the surgery is not tocorrect a flow deficiency per se, but bloodflow will have a serious impact on thesuccess of the surgery. Examples are:intracranial aneurysm clipping surgery andcarotid endarterectomy (where even a

temporary deprivation of flow will cause intra-

operative stroke) and liver transplant surgery(where a low hepatic arterial flow, or flow

mismatch between hepatic artery and portal vein

flows can cause early organ rejection).

OBJECTIVEHere, the purpose of the surgery is not tocorrect a flow deficiency, but blood flow is acritical parameter for surgical success. Inthis instance, a flow measurement may betaken at the beginning of surgery, and careis taken during surgery to assure that thislevel of flow is preserved.

The surgical protocols listed in this manual try to shed some light on the firstquestion from a surgeon new to flow measurement, “What is a “good” flow?” or“What is a “bad” flow?” during a specific surgery.

Why Measure Flow?Different departments in the hospital, and different constituencies connected to thehospital, all view a surgeons’ task from their own perspective. The answer to “WhyMeasure Flow,” therefore, has different responses depending on who is asking thequestion.

Flow measurement provides an objective Functional Assessmentof the success of vascular surgery

In surgeries where the restoration of flow is a primary factor, flow must bemeasured. While the Technical Quality of Surgery is readily observed at theend of surgery when the patient is wheeled off to recovery and recovers fromanesthesia, the Functional Success of Surgery is more difficult to determine.It requires more intraoperative physiological measurements. Are all the graftsoperational? Is organ flow adequate? What is the patient’s long-term prognosisbased on intraoperative clinical assessments, and what treatment regimendoes this suggest?

Detection of technical error when it can be readily corrected Adequate pressure but a lower-than-expected flow often indicates a technicalerror such as a stitch that picks up the back wall of a vessel. Flowmeasurement saves the day in such instances.

Continuous Quality Improvement (CQI) A basic tenet of any quality program is that you have to measure what you wantto improve. If blood flow affects surgical success, it must be measured.

The need for functional measurement tools increases as surgeriesbecome more challenging

As surgical complexity has increased so has the need for intraoperative flowmeasurement and documentation. In procedures such as endoscopic surgery,the surgeon cannot palpate the vessel to get a qualitative assessment oftechnical adequacy of the surgical repair. More and more patients are firststented; the surgeon now needs to restore flow in the presence of failedsurgical implants. In surgeries such as partial liver transplant, flow and ratiosbetween flows are critical to surgical success.

Baseline measurements for follow-up care after surgery Intraoperative measurement of flow parameters may avoid post-surgical tests,and provide information for further patient treatment during recovery andthereafter.

Peace of Mind for the SurgeonEspecially in cases where there is risk for severe functional complications suchas intraoperative stroke, measurement and correction of factors that wouldresult in such complications, provides peace of mind to the surgeon.





ML-60, REV. A, 9-054


Avoid Re-OperationRe-Ops are costly, and not reimbursed by the patient’s insurer. Wheneverintraoperative flow measurement alerts the surgeon to a flow-limiting problem thatcan be corrected during surgery, re-operation is avoided and money is saved.

Intraoperative Training of Surgical ResidentsSurgical residents acquire their surgical proficiency as they perform more and moresurgeries. However, if errors occur, the onus falls on the Chief of Surgery. Therefore,the Chief of Surgery must demand the use of intraoperative quality measurementdevices such as flowmeters, to confirm the quality of surgical repairs and to turnresidents into lifelong learners who learn from and correct their errors.

Standard of CareAll new surgical protocols are developed using measurement and interpretation of allavailable physiological parameters. Surgeons who adopt this new surgical approachmust include measurement of those physiological parameters (unless there isauthoritative published evidence that the measurement of certain parameters can then bedropped once the surgical approach becomes mainstream).

Patients’ Rights: Documentation of Surgical SuccessHospital and surgical care is all about patients. Patients deserve the best, and nowwill often shop around for the best care. Hospitals must therefore stay on the forefrontof medical innovation and quality assurance.

Liability Insurance RequirementsIn no other industry can a repair be performed where the “shop” would not check thequality of the work before the product is delivered (e.g., electronic or car repair shop).Therefore, juries have become more and more inclined to award large damages tosurgeons who do not take the opportunity to check and document the quality of theirsurgical repair before the patient is closed. On the other side, documentation ofsurgical success is strong evidence to support the surgeon in court, and may lowermedical insurance fees.

Continuous R & DCorrelating intraoperative anatomical manipulations, which are under the control ofsurgeons, with a patient’s long-term restoration to health requires ongoing followupstudies that correlate intraoperative physiological parameters, such as blood flow,with short-term and long-term surgical outcomes.

Flow Measurements Complement Pressure MeasurementsFlow is a quintessential vital sign; pressure is a parameter that is adjusted by thebody to control flow. An abnormal blood pressure may be tolerated by the body forprolonged periods, but an abnormal blood flow will be damaging to organ health onshort notice. Pressure divided by flow is equal to organ impedance, an importantparameter for (a) detection of technical error in an anastomosis which would makethe vascular impedance look unreasonably high, (b) selection of follow-up patienttreatment regimens.



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Transonic Systems has pioneered the modern transit-time ultrasound flowmetertechnologies, based on research at Cornell University by one of the founders ofTransonic, Mr. Cornelis Drost. These modern sensors measure volume flowdirectly (milliliters per minute), not flow velocity.

Flow sensors for surgery have a convenient handle, and a probe headconfiguration that is customized for the vessel size and type of vessel. Please visitwww. transonic.com for details. The flow meter has a “FlowSound™” feature, soyou do not have to take your eyes off the surgical field while you accesssystolic/diastolic patterns of flow.

Flow measurements are easy to perform as outlined below:


➮ Vessel Preparation. Vein grafts typically require nopreparation. Internal mammary artery pedicle: clear fattissue from a 1 cm length of the pedicle before performingthe anastomosis.

➮ Select a flowprobe size for a non-constrictive fit (graft diameter between 60% - 100% of the vessel slot width.)

➮ Turn on FlowSound™.

➮ Apply sterile ultrasound gel (Aquasonic 100™, Parker Labs)to the vessel slot of the probe. This will ensure goodultrasound contact between the probe & graft.

➮ Place the probe head on the graft bending the flexibleneck as needed. Avoid placing the probe over surgicalclips or sutures.

➮ Verify quality of ultrasound contact between probe andvessel. Good ultrasound contact is indicated when theultrasound “container” in the flowmeter display is filled 50%or more.

➮ Measure flow. FlowSound is available immediately. Meanflow readings take approximately 10-15 seconds tostabilize. Press the PRINT button to document pulsatileflow. Keep probe steady until printer stops.

Accurate measurements are technique dependent.Please refer to www.transonic.com for training support.


ML-60, REV. A, 9-056Transonic Systems Inc.

www.transonic.com

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Adequate blood flow is fundamental to successful surgical outcomes.During vascular surgery, intraoperative blood flow measurement helpsto guide the intervention and identify flow-limiting problems immediatelyso that corrections can then be made while the patient is still in the OR.Applications in which flow measurements have proven useful include:

1. AV Access (pages 7-12)

Flow measurements are instructive during creation of an autogenous(fistula) or non-autogenous (graft) vascular access as well as during anintervention.

2. Peripheral Bypass Surgery (pages 13-18)

Intraoperative graft flow measurements forecast the patency of abypass and detect occlusion or technical error during peripheralbypass reconstruction.

3. Carotid Endarterectomy (pages 19-22)

Flow-QC quality control after carotid endarterectomy is recommendedsince early occlusion or embolization from the operative site mayresult in stroke.

—————————————————————————————————————————

Vascular SurgeryTRANSONIC

AV Fistulas & Grafts PROBE SIZE (mm) . . . . . . . .PROBE SERIES

radial artery . . . . . . . . . . . . . . . . . . . 2, 3 . . . . . . . . . . . . . . .-FMV or -FSBbrachial artery . . . . . . . . . . . . . . . . . 3, 4 . . . . . . . . . . . . . . .-FMV or -FSBvenous outflow of graft . . . . . . . . . . 4, 6 . . . . . . . . . . . . . . .-FMV or -FSB

Lower Extremity Bypass profunda femoris . . . . . . . . . . . . . . 8 . . . . . . . . . . . . . . . . . .-FMV or -FSBcommon femoral . . . . . . . . . . . . . . . 8, 10 . . . . . . . . . . . . . . .-FMV or -FSBpopliteal . . . . . . . . . . . . . . . . . . . . . . 4, 6 . . . . . . . . . . . . . . . .-FMV or -FSBtibial . . . . . . . . . . . . . . . . . . . . . . . . . 3, 4 . . . . . . . . . . . . . . . .-FMV or -FSB

Carotid Endarterectomycommon carotid artery . . . . . . . . . . 8, 10 . . . . . . . . . . . . . . .-FME -FMV, -FSBinternal carotid artery . . . . . . . . . . . 6 . . . . . . . . . . . . . . . . . . .-FME -FMV, -FSBexternal carotid artery . . . . . . . . . . . 6 . . . . . . . . . . . . . . . . .-FME -FMV, -FSBPruit-Inhara Shunt . . . . . . . . . . . . . . 2 . . . . . . . . . . . . . . . . . . .-XLPJavid Shunt . . . . . . . . . . . . . . . . . . . 3 . . . . . . . . . . . . . . . . .-XLJ

Abdominal renal bypass . . . . . . . . . . . . . . . . . . 4, 6 . . . . . . . . . . . . . . . .-FMV or -FSBaorta iliac shuntaorta . . . . . . . . . . . . . . . . . . . . . . . 16, 20 . . . . . . . . . . . . . .-Acommon iliac . . . . . . . . . . . . . . . . . 10, 12 . . . . . . . . . . . . . .-FMV or -FSB

portal-caval shunt . . . . . . . . . . . . . . 10, 12, 14 . . . . . . . . . . . .-FMV or -FSB spleno-renal shunt . . . . . . . . . . . . . . 10, 12, 14 . . . . . . . . . . . .-FMV or -FSB—————————————————————————————————————————

Vascular Applications and Vessel Size Guide

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Autogenous arterial venous fistulas (AVFs) are the preferred vascular access.They remain patent longer and exhibit fewer complications than AV graftsand catheters.

Measurement Steps1. Identify Vessel to Be Measured

Expose and identify the venous outflow of the AVF.

2. Select Flowprobe SizesMeasure the diameter of the vein with a gauge. Select a probe size so thatthe vein diameter is between 60% - 100% of the vessel slot width of theflowprobe.

PROBE SIZE NONRESTRICTIVE VESSEL RANGE

4 mm 3.2 - 5.3 mm6 mm 4.5 - 7.5 mm

3. Apply Flowprobe to Measure Venous Outflow: Select a site on the veinwide enough to accommodate the probe’s acoustic reflector. Apply sterileAquasonic Gel 100™ to the Flowprobe lumen to provide ultrasound couplingbetween the probe body and probe reflector. Apply the Flowprobe to thevein, bending the probe’s flexible neck segment, as necessary, so that theentire vein lies within the lumen of the probe and aligns with the probe body.Re-apply sterile gel back into the probe lumen as needed. Listen to the pitchof FlowSound™ as the Flowprobe is applied to the vessel. The higher thepitch, the greater the flow.

Fig. C1: Measuring venous outflow in an end-to sidefistula.

Fig. C2: Measuring venous outflow flow in a side-to-side fistula.

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Measurement Steps cont.

Check the Signal Quality Indicator (bucket display) on the flowmeter ’s front panelfor ultrasound acoustic contact. An acoustic error message will be displayed ifultrasound contact falls below an acceptable minimum.

VENOUS END-TO-ARTERIAL SIDE (End-to-Side) ANASTOMOSIS:When the AVF is constructed with end-to-side anastomosis, simply measurevenous outflow distal to the venous anastomosis (Fig. C1).

SIDE-TO-SIDE ANASTOMOSIS:If the anastomosis is constructed with a venous-side-to-arterial-sideanastomosis, occlude the vein (Fig. C2) proximal to the venous anastomosiswhile measuring flow distal to the anastomosis. If spasm occurs, papaverinecan be locally infiltrated along the artery and vein while flow is continuouslymonitored.

For the AVF to mature, the following guidelines have been reported.1


4. Document FlowsAfter applying a Flowprobe to a vein, wait 10-15 seconds for mean readings tostabilize. Then press the PRINT button on the flowmeter to document the phasicflow patterns for the case record. If flow is negative on the flowmeter display,press the INVERT button to change the polarity before printing the waveform.

5. Measure Potential for Steal Syndrome (Optional) With the flowprobe placed on the vein as before, measure flow with, andwithout, occlusion of the artery distal to the arterial anastomosis. The differencebetween the two readings equals flow in the distal branch of the artery. Often,the flow reading without distal occlusion will be higher than the reading withocclusion. This means that blood in the distal branch is flowing retrograde toaugment fistula flow. Vascular steal may develop in such instances. The flowlevels at which steal becomes a concern have not been documented. It isimportant to track and report these measurements so, in the future, steal can besurgically averted. (Note: Alternately, distal arterial flow may be measured directly byplacing a flowprobe on a properly cleaned distal site of the artery.)

1Johnson et al, “Prognostic value of intraoperative blood flow measurements in vascular access surgery,” Surgery124:729-38, 1998

FISTULA TYPE FAILURE WITHIN 90 DAYS(REQUIRING INTERVENTION)————————————————————————

RADIOCEPHALIC

Flow <170 ml/min 56% P=.001Flow >170 ml/min 15%

BRACHIOCEPHALIC

Flow <280 ml/min 64% P=.01Flow >280 ml/min 18%

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Fig. C4: Loop ePTFE Graft anastomosed to the sideof an artery and end of a vein.

Fig. C5: Straight ePTFE Graft anastomosed to the sideof an artery and end of a vein.

ligatedb)

ligated

b)

Figs.: Non-Autogenous Prosthetic Grafts: Loop (Figs. C3, 4) or straight (Fig. C5) PTFE grafts areconstructed with inflow from the radial or brachial artery to the cephalic vein. End-to-side anastomosesmay be used to attach the prosthetic ePTFE graft to the end of the vein and side of the artery.

Fig. C3: Loop ePTFE Graftfrom brachial artery tocephalic vein.

Direct intraoperative flow measurement on newly inserted prosthetic ePTFEgrafts is not possible due to air in the ePTFE graft walls (air blocks ultrasound

transmission). Therefore, graft outflow is measured on the vein after constructionof the arterial and venous anastomoses. (In cases where the vein has not beenligated, this flow measurement is made proximal to the anastomosis, with temporaryocclusion applied to the distal portion of the vein.)

Measurement Steps1. Identify and Prepare Vein to Be Measured

Identify the exposed segments of the venous outflow conduit for the graft.Determine the optimum site (wide enough to accommodate the probe’s acousticreflector) for applying the probe, and clean the vein at this site from fat andexcess tissue.

2. Select Flowprobe SizesEstimate the diameter of vein with a gauge. Select a probe size so that thevein diameter is will fill 60% - 100% of the vessel slot width of the probe.

NOMINAL PROBE SIZE ACCEPTABLE VESSEL RANGE

4 mm 3.2 - 5.3 mm6 mm 4.5 - 7.5 mm

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Measurement Steps cont.

3. Apply FlowprobeApply sterile Aquasonic Gel 100™ to the Flowprobe to provide ultrasoundcoupling between the probe body and probe reflector. Apply the Flowprobeto the vein, proximal to the anastomosis, bending the probe’s flexible necksegment as necessary, so that the entire vessel lies within the lumen ofthe probe and aligns with the probe body. Listen to the pitch ofFlowSound™ as the Flowprobe is applied to the vessel. The higher thepitch, the greater the flow.

Check the Signal Quality Indicator (bucket display) on the flowmeter ’s frontpanel for ultrasound acoustic contact. An acoustic error message will bedisplayed if ultrasound contact falls below an acceptable minimum.

4. Measure and Evaluate Venous Outflow With the Flowprobe positioned as under Step 3 (above), measure venousaverage flow as displayed on the flowmeter. An initial venous outflow <400 ml/min is associated with a higher rate of initial graft failure.1

As the site recovers from surgery, flow will increase to levels preferred forhemodialysis (> 600 ml/min).


5. Document FlowsAfter applying a Flowprobe to a vessel, wait 10-15 seconds for meanreadings to stabilize. Then press the PRINT button on the flowmeter todocument the phasic flow patterns for the case record. If flow is has anegative sign on the flowmeter display, press the INVERT button tochange the polarity before printing the waveform.

6. Measure Potential for Steal Syndrome (Optional) With the flowprobe placed on the vein as before, measure flow with, andwithout, occlusion of the artery distal to the arterial anastomosis. Thedifference between the two readings equals flow in the distal branch of theartery. Often, the flow reading without distal occlusion will be higher than thereading with occlusion. This means that blood in the distal branch is flowingretrograde to augment fistula flow. Vascular steal may develop in suchinstances. The flow levels at which steal becomes a concern have not beendocumented. It is important to track and report these measurements so, inthe future, steal can be surgically averted. (Note: Alternately, distal arterial flowmay be measured directly by placing a flowprobe on a properly cleaned distal site ofthe artery.)

1Johnson et al, “Prognostic value of intraoperative blood flow measurements in vascular access surgery,” Surgery124:729-38, 1998

GRAFT TYPE FAILURE WITHIN 90 DAYS(REQUIRING INTERVENTION)————————————————————————

PTFEFlow <400 ml/min 65% P=.01Flow >400 ml/min 40%

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Especially in fistulas, flow may mature to a level that imposes too much load on the heart. Flowmeasurements during surgery will confirm that“banding” of the artery reduces flow to anacceptable level.

Measurement Steps

1. Before the intervention, an AV access flow target is set,with dueconsideration of the type and location of the access, patient size, weight,gender, medical and access flow histories.

2. Measure flow through the AV access (following protocols in C1a or C1b)before the AV access revision.

3. Measure flow after revision. Compare and document the before and afterflows. Evaluate the after-flow measurement against the AV Access FlowTarget.

In the Failed AccessWhen an access has failed, direct intraoperativeflow measurements of distal outflow helps to bothguide the revision and confirm its success. Proto-cols similar to those for construction of the fistula or prosthetic graft are followed (refer to pages

7-10).

Fig. C6: Common Arm AVFistula Sites

When Access Flow is Too High



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• Intraoperative blood flow rates directly correlate to accessoutcomes including: patency, number of interventions, andmean time to interventions- The higher the intraoperative blood flow, the greater the patency

intervals.- Low flow access can be revised immediately or abandoned reducing

patient morbidity- Patients do not leave surgery with poorly functioning accesses- Eliminates unnecessary revisions

• Intraoperative blood flow measurement allows more efficientmanagement of a patient’s vascular access - minimizes the need for catheters- leads to time savings for the surgeon, OR, and patient

Measurement of blood flow is faster than waiting for a fistula or graft to mature;Revisions can be quantified on the table instead of in the dialysisunity

- Saves money for the surgeon and OR: Avoids non-reimbursable re-operation (within 30 days in the USA) for the same problem on the samepatient. The hospital and physician lose money when these arenecessary.

• Transit time ultrasound technology has a number ofadvantages over Doppler ultrasonogram- Measures volume flow directly, not velocity. No need

for additional calculations- Not dependent on particulate bodies (i.e. red blood cells)

- Not dependent on angle- Does not assume laminar flow- Diameter independent- More accurate

1Gleaned from Johnson et al, “Prognostic value of intraoperative blood flow measurements in vascular access surgery,”

Surgery 1998:124:729-38.

Lower extremity bypass surgery includes both the femoro-popliteal bypass and abdominal (iliac artery) bypass (Fig. C6 & C7).These surgeries involve restoration of flow and thus, flowmeasurement is imperative. Since there is such a wide range ofvascular disease present in individual patients, acceptable levelsof flow at the conclusion of surgery have not yet been welldocumented. In all cases, we recommend the following flowmeasurement protocol.

1. At the beginning of bypass, once the site for the graft’sdistal anastomosis has been exposed, measure the flow atthis site (Position B in Fig C-8). This is the flow that must beincreased via the graft. Note the systemic pressure. Flowat this site, in first approximation, will vary proportional tosystemic pressure.

2. After the proximal anastomosis of the graft has beenconstructed, apply a flowprobe into the graft and take ashort (10-15 sec) measurement of Free Flow through thegraft with its distal end open. This is the free flowcapacity of the graft. Flow augmentation provided bythe graft will be only a fraction of the free flow due tothe resistance of the distal vascular bed. Thismeasurement also provides a quality measurement ofthe proximal anastomosis and will confirm that thevalvulotomy in vein grafts was adequate.

3. After the distal anastomosis is complete and the graftclamp is released, flow through the graft and currentsystemic pressure are again measured. The currentgraft flow (“Bypass Flow”) is a direct measure of theflow augmentation benefit provided by the bypass surgery.

Bypass FlowFree Flow Index (FFI) = ——————

Free FlowThe Free Flow Index is likely a valuable parameter in the study oflongterm benefit of the bypass surgery. A graft into tissue with low flowimpedance such as an extracranial-intracranial (EC-IC) bypass has atarget Free Flow Index of 0.5 or higher1. In high-impedances sites ofthe lower limb with vascular disease, the Free Flow Index will besubstantially lower, and could potentially serve as an indication of theseverity of the vascular disease.

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Reference:1Amin-Hanjani, et al, “The Cut Flow Index: An Intraoperative Predictor of the Success of EC-IC Bypass forOcclusive Cerebrovascular Disease,” Neurosurgery, January 2005. (2922AH)

Fig. C6: Fem-Pop Bypass

Fig. C7: Abdominal(Iliac a) Bypass

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Surgical Approach—————————————————

After completing a lower extremity arterialbypass, flow is measured before closure ofthe wound. Generally, we measure flowimmediately after finishing the lastanastomosis of the bypass and do notreverse heparinization.

A 4 or 6 mm flowprobe is employed for thesaphenous vein, a 6 mm probe isemployed for the popliteal artery, an 8 or10 mm probe for the common femoralartery, and a 4 mm probe for tibial arteries.

Dacron grafts, which we very rarely usedistal to the common femoral artery, allowdirect measurement of flow by transit-timeprobes. Expanded PTFE grafts cannot bestudied immediately by a probe placed onthe graft, as air trapped in the graftinterstices interferes with ultrasoundtransmission, and an accuratemeasurement is not possible until this air is expelled.

Three methods, A, B, and C, are used tomeasure flow. Method A is suitable for saphenous vein or dacron grafts; andMethods B and C are useful for PTFE grafts. We frequently employ MethodC to measure the distribution of flow beyond the distal anastomosis inretrograde and antegrade directions. Method B is employed wheneverexposure of the distal vessel receiving the bypass is poor, and placement ofthe probe on both sides of the distal anastomosis is difficult. Probes withback exiting cables are easier to use when exposure is poor.

Method A: Saphenous Vein or Dacron Grafts—————————————————————

To measure flow with saphenous vein or dacron, the probe is first placed justdistal to the proximal anastomosis [Fig. C8: position A]. Flow is documented on theflowmeter’s built-in chart recorder. The presence of a hemodynamicallysignificant stenosis causing turbulence is easily detected by a characteristicartifact in the flow vs. time waveform (Fig. C9). Similarly, the distal anastomosisis studied for turbulence by placing the flowprobe on the target vessel for thebypass just distal to the distal anastomosis [Fig. C8: position B].

Fig. C8: Flow measurement sites duringlower extremity bypass.

Ian Gordon, MD, PhD, Professor, Dept. of Surgery, Univ. of CA, Irvine

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Assuming no technical problem ispresent requiring graft revision, we carryout our definitive flow measurement. Theprobe is placed on the bypass at anyconvenient position and flow ismeasured. We routinely measure flowwith the graft temporarily clamped toconfirm accurate zero flow reading. Theflow in the graft [Fgraft] is then measuredagain. In order to measure resistance offlow through the graft and into the distalrun-off vessels, we measure the pressuredrop across the graft. A 26 gauge needleconnected to a three-way stopcock andconnected by plastic extension tubing toa sterile pressure transducer (usually the

anesthetist's radial artery catheter transducer) isbrought onto the surgical field. Thebypass graft is punctured by the needleseveral cm distal to the proximal anastomosis. The mean pressure with the graft open[Popen] and with a clamp occluding the graft proximal to the needle [Pclamp] are recordedwith the assistance of the anaesthetist. After finishing the measurements, the needlehole is closed with a 6-0 suture.

The graft resistance to flow, R, is calculated as:

FgraftR = ————————

(Popen - Pclamp)

An unusually high value of R would indicate a flow obstruction within the graft(valvulae, thrombus), or at the distal anastomosis.

Method B: PTFE Femoropopliteal Bypass————————————————— In a typical PTFE femoropopliteal bypass, the graft origin is from the common femoralartery. An 8 or 10 mm probe is placed on the common femoral artery just proximal tothe bypass (Fig. C8, Position D). Flow in the common femoral artery is then measuredwith the graft open [Fopen] or clamped [Fclamp]. Net graft flow is equal to (Fopen - Fclamp).Resistance is measured as in Method A.


Fig. C9: These waveforms show a case wherea previously placed vein graft had a stenosisnear the origin. The upper waveform showsthe flow before correcting the stenosis. Thelower waveform shows the flow pattern aftercorrecting the stenosis.

Bef

ore

Afte

r

100

0

0

100 ml/min

Mean Flow in Graft 45 ml/min

Mean Flow in Graft 90 ml/min

Method A: Saphenous Vein or Dacron Grafts cont.

——————————————

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ML-60, REV. A, 9-0516

Method C ————————————————— A 4 or 6 mm probe is placed on the target vessel just distal to the distalanastomosis [Fig. C8 position B] and antegrade flow is measured with the bypassgraft open [Fao] and clamped [Fac]. To measure retrograde flow, the probe isplaced on the target vessel (Fig. C8, Position C) just proximal to the distalanastomosis and flow is measured with the graft open [Fro] and clamped [Frc].

Care needs be taken to ensure that the direction of blood flow is carefullyobserved and negative and positive signs correctly employed to accuratelymeasure flow. Net graft flow is calculated as (Fao - Fac) + (Fro - Frc). Resistance ismeasured as in Method A.

Note: Since pulse is a manifestation of pressure, not flow, an occluded graft may stillhave a distinct pulse.


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References 1 Lundell, A, Bergqvist, D., “Prediction of Early Graft Occlusion in Femoropopliteal and

Femorodistal Reconstruction by Measurement of Volume Flow with a Transit time Flowmeterand Calculation of Peripheral Resistance,” Eur Journal of Vascular Surgery 1993;7:704-709.

2 Transonic Medical Note #M1, Lower Extremity Bypass, Ian Gordon, MD, PhD3 Lundell, A., Nyborg, K., “Do Residual Arteriovenous Fistulae after In Situ Saphenous Vein

Bypass Grafting Influence Patency?” Journal of Vascular Surgery, Vol. 30, p.99-105, 1999.1903AH

4 Ihlberg, L.H.M., Alback, N.A., Lassila, R., Lepantalo, "Intraoperative Flow Predicts theDevelopment of Stenosis in Infrainguinal Vein Grafts, J Vasc Surg 2001;34:69-76. 2064AHM

• Detection of technical defects- Twisted vein grafts can be revised immediately- Patients do not leave surgery with poorly

functioning grafts- Eliminates unnecessary revisions

• Confirms reconstruction success- The higher the intraoperative blood flow,

the greater the patency intervals.

• Prognostication of bypass patency The post-reconstruction measurement can be

used as an indicator of patency.

- distal flows > 100 ml/min (fem-pop) indicates

a successful reconstruction

- distal flows < 75 ml/min indicates a high risk

of graft occlusion within the first six postoperative months

• Intraoperative blood flow measurement allow more efficientmanagement of a patient’s peripheral arterial disease.- leads to time savings for the surgeon, OR, and patient.

Measurement of blood flow is faster than angiography. - Saves money for the surgeon and OR: Avoids non-reimbursable re-

operation (within 30 days in the USA) for the same problem on the samepatient. The hospital and physician lose money when these arenecessary.

• Transit time ultrasound technology has a number of advantagesover Doppler ultrasonogram- Measures volume flow directly, not velocity. No need

for additional calculations- Not dependent on particulate bodies (i.e. red blood cells)

- Not dependent on angle- Vessel diameter independent- More accurate



Fig. C10: Waveforms showing flowbefore a fem-pop revision andafter the technical error wascorrected.

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#1. Intraoperative Flow Measurement in Peripheral Bypass SurgeryGeorg Steinpórsson, MD1

(private communication 2001)

“The flow measurements are very helpful and we use it in all our cases.”

Finding FistulasFirst of all we use flow measurement to find fistulas after we have placed an in situsaphenous vein graft. We only expose the vein proximally and distally in the beginning. Wethen place two probes on the graft. By using finger compression, we can locate the sidebranches with great accuracy. We then make an incision and ligate the branch.

Graft Flows130-150 ml/min: It is our feeling that if flow is 130-150 ml/min, the graft is going to be asuccess and I do not request an angiography. However, I usually get a duplex scan after1, 3-6, and 12 months.

<50-130 ml/min: When flow is between 50 -130 ml/min, we get an early post-op duplexscan before we request systemic anticoagulation since flow sometimes improves soonafter the operation.

<50 ml/min: If flow is less than 50 ml/min, the graft is in trouble. We look for technicalproblems with either angiography or duplex scanning. If no reason is found and the flowdoes not increase with vasodilation with papaverine, we strongly consider anticoagulationand an early post-op study.

#2 Detection of Twisted Saphenous Vein Graft during Femoropopliteal Bypass1

Procedure: A femoropopliteal bypass wasconstructed with a reversed saphenous veinfrom the deep femoral artery to the above-knee popliteal artery in the right leg.Intraoperative angiography revealed a nicedistal anastomosis with unrestricted run-offbefore flow was re-established.

Flow Measurement: Blood flow was measuredwith a 4 mm probe after flow was re-established in the vein graft. Both the meanflow value and the flow waveform indicated no flow in the graft, although blood pulseswere excellent in the proximal graft.

SVG Graft Correction: When the distal anastomoses was exposed, a severe twist of thegraft was discovered. No pulses were palpable distal to the distal anastomosis. The graftwas divided, untwisted and re-anastomosed end to end.

Followup Measurement: A followup measurement indicated a flow of 132 ml/min. The pulseat the distal anastomose was excellent and the foot was well perfused.

Fig.C11: Upper trace: Blood volume flow in afem-pop bypass after initial re-establishment ofblood flow. Lower trace: Blood volume flowafter correction for a twisted fem-pop bypass.

Reference: 1Plate, G., “The Prediction of a Twisted Saphenous Vein Graft during Femoropopliteal Bypass,” Medi-Stim Clinical Cases, September 1997.


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Carotid FlowmetryThe plaque being removed during carotidendarterectomy constitutes a resistance to flow. Onetherefore would, at first glance, expect considerablechanges in pre- and post-endarterectomy flows in thecarotid vessels. However, this is not the case in themajority of carotid surgeries. A stenosis has to be severeGrade III (over 75%) or more before it appreciably affectsthe average flow (see FAQ, page 23).

The effect of plaque removal during carotidendarterectomy on carotid flow is more subtle. Overallflow (Common Carotid Flow = Internal + External Carotidflows) may increase approximately 20% if pressurestays the same, and the distribution of flow betweenthe Internal Carotid Artery and the ExternalCarotid Artery shifts. A significant qualityimprovement can be seen in the flow profiles of allthe carotids. Before endarterectomy, the flow profilelooks very “ragged,” very noisy. After endarterectomy,the flow waveform becomes smoother, due to theremoval of flow turbulence caused by plaquenarrowing the vessel. Therefore, a print-out of thebefore- and after-waveforms is valuable to document the quality of endarter-ectomy surgery.

Generalized Surgical Protocol for Carotid Endarterectomy

1. Measure and record flows in the Common Carotid Artery, External CarotidArtery, and Internal Carotid Artery before the endarterectomy, along with thepatient’s systemic pressure with special (FME-series) perivascularprobes that will not compress the artery during their application orremoval (Fig C13).

2. Measure and record the same three flows after the endarterectomy, along with systemicpressure.

3. If pressure is the same, one would expect a slightincrease in total carotid flow, more so for a GradeIV or Grade V stenosis (see Fig D1, page 23). Theflow waveform should indicate a decrease in flowturbulence. If flow has decreased instead (to adegree not explained by a drop in systemic pressure),a technical error is indicated.


FME-Series

Handle Probe

(L-reflector)

flashFig. C13: FME-Series steam-

sterilizable handle-stylecarotid flowprobe.

Fig C12: Probe Positions andrepresentative waveforms,Pre & Post Endarterectomy

mL/

min

200

0INTERNAL CAROTID ARTERY

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ML-60, REV. A, 9-0520

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Javid / Pruitt-Inahara FlowmetryA second, very important use of the intraoperative flowmeterduring carotid endarterectomy is with temporary carotid bypassshunts. Flow to the brain is a quintessential vital sign that cannotbe compromised. Transonic manufactures a line of sterile tubingclamp-on flow sensors especially for this purpose. (The ultrasoundsignal of the standard perivascular probes is not capable of penetratingthe plastic wall of these bypass shunts.) In every case where thesurgeon finds that preservation of cerebral flow must be assuredvia a Javid or Pruitt-Inahara shunt, there it is also imperative that one measureswhether this flow preservation is really achieved. A sterile tubing flowsensor,with the flowmeter’s FlowSound™ feature, will give an instantaneous report of ablocked inflow or outflow of the shunt. Also a surgeon may be able to hear andrecognize the gradual decrease in flow that would indicate a slowly growingthrombus inside the shunt.

General Surgical Protocol for Javidand Pruit-Inahara Shunt Flowmetry

1. Place the shunt, affix the sterile tubing flowsensor onto the shunt.

2. Verify that the shunt carries adequateflow (typically: 100 ml/min or more).

3. Turn on the flowmeter’s FlowSound forcontinuous audio feedback on cerebralgraft flow adequacy.

“We shunt all our patients with a large Javidshunt and place a clamp-on sensor on theshunt to ensure that any interruption ofshunt flow is detected.”

Ian Gordon, MD, PhD, Univ. of CA, Irvine

Fig. C14: -XLSterile tubingclamp-onFlowsensor

Fig. C15: Clamp-on sensor on Javid shuntduring endarterectomy

For accurate readings with the carotid flowprobes:1. Make sure that the vessel is sitting completely within the probe/vessel

window as shown in Fig. C13. The probe must completely surround thevessel for proper acoustic transmission to occur.

2. Be careful not to pull up on the vessel once the reflector is slippedunderneath. This may distort the measurement.

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Surgical Approach—————————————————

No special adjustment in surgical technique is necessary for measurementof blood flow during carotid surgery. The sites on the carotid arteriesskeletonized by dissection for vascular clamp placement are identical asthose employed for probe placement. A 10 mm probe (sometimes an 8 mm probe

is used) is employed for the distal common carotid artery and 6 mm probes forthe origin of the internal and external carotid arteries.

The probe on the external carotid is placed just distal to the origin of thesuperior thyroid artery. We perform the pre-endarterectomy flowmeasurements immediately after administration of systemic heparin.Measurement of all three arteries only requires a few minutes.

After the first measurement, vascular clamps are placed and theendarterectomy is performed. We shunt all our patients with a large Javidshunt and place a clamp-on sensor on the shunt to ensure that anyinterruption of shunt flow is detected.

After finishing the endarterectomy, removal of all clamps, and establishinghemostasis, a repeat flow measurement is performed. Occasionally, a lowflow or turbulent flow waveform is detected indicating the presence of asignificant stenosis which requires immediate revision. As a consequence,we try not to reverse heparin with protamine until completion of the flowmeasurements.

Typical Flows Observed——————————————————————————————————

CONDUIT PRE-ENDARTERECTOMY POST-ENDARTERECTOMY

common carotid a. 287 ± 17 329 ± 18external carotid a. 126 ± 10 104 ± 8internal carotid a. 135 ± 10 178 ± 11



ReferencesGordon, I.L., Goldstein, L.J., Ceraldi, C., Weir, P., Tobis, J., Stemmer, E., “HemodynamicEffects of Serial Stenoses in an Arterial Model”, American College of Surgeons, SurgicalForum, Vol. XLII, pp. 315-319, 1991.

Gordon, I., Weil, J., Williams, R., Wilson, E., “Intraoperative Measurement of Javid ShuntFlow with Transit Time Ultrasound”, Annals of Vascular Surgery, Vol. 8, p. 571-577, 1994.

Gordon, I.L., Stemmer, E.A., Williams, R.A., Arafi, M., Wilson, S.E., “Changes in InternalCarotid Blood Flow after Carotid Endarterectomy Correlates with Preoperative Stenosis”, TheAmerican Journal of Surgery, Vol. 168, p. 127-130, 1994.

Ian Gordon, MD, PhD, Professor, Dept. of Surgery, Univ. of CA, Irvine

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• Intraoperative blood flow measurements expedite surgeryby revealing flow deficiencies which can be addressedimmediately before occlusion or embolization occurs that mayresult in perioperative stroke.- Saves money for the surgeon and OR - Detects formation of a thrombus in the shunt: clamp-on sensors clipped

around shunt tubing provide a ongoing measurement of shunt flowthroughout the course of the surgery

• Provides a Quality Control for the Endarterectomy- Higher post-endarterectomy flows provide an objective measure to the

surgeon’s subjective assessment and confirms the success of theendarterectomy

• Transit time ultrasound technology has a number ofadvantages over Doppler ultrasonogram- Measures volume flow directly, not velocity. No need for additional

calculations- Not dependent on particulate bodies (i.e. red blood cells)

- Not dependent on angle- Does not assume laminar flow- Diameter independent- More accurate

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Why shouldn’t I just continue using my pen-tip Doppler to assess flowpreservation during aneurysm clipping surgery?

The Transonic ultrasound flowmetermeasures volume flow, or flow, i.e.how much blood passes through avessel (mL/min). Doppler ultrasoundmeasures flow velocity, i.e. how fastthe blood travels (cm/sec). A classicstudy by Spencer and Reid in 1979(Fig. D1) correlated the degree ofstenosis in a vessel to changes in flowand velocity, and compiled theoreticalpredictions with observations of acarotid flow/angiography study. Jaberet al (Ann Thorac Surg 1998;66:1087-92)performed a similar study of coronarystenosis, and confirmed that theTransonic flowmeter is indeed effectivein detecting stenosis > 75%.

Comparison of Transonic volume flowsensing & Doppler velocity sensing:The Transonic flowprobe provides asensitive diagnosis of severe stenosis (redcurve in Fig. D1 above). The amount of bloodcarried by the vessel does not decreasesubstantially for Grade I and Grade II stenoses. However, flow decreases rapidly once thedegree of stenosis progresses beyond 75% of the vessel diameter. Flow at or below 20%of baseline indicates a Grade IV stenosis. A Grade V stenosis shows flow near zero.

Doppler flow velocity sensors, on the other hand, present a confusing picture. Flowvelocities within a stenosis (dark blue curve) differ from velocities in a non-stenosed portionof the vessel (light blue curve). One would thus need to scan the entire length of a vessel tosearch for a possible site of stenosis, and then assess the ratio between peak velocities atthe stenosed site and in a non-obstructed part of the vessel (Spencer, Reid, 1979). However,flow velocities within a Grade IV or V stenosis may look no different from those in a vesselwithout any stenosis!

Summary: The Transonic flow probe is an effective tool for diagnosing severe stenosis. Flowreadings below 50% of baseline should not be disregarded.

When do I take flow measurements?Depending on the surgical procedure, flows are measured in exposed vessels both beforeand after or simply after the intervention or reconstruction. If flows are measured bothbefore and after, the flows are compared and improvement in flow is recorded in thepatient’s record.

Fig. D1: Graph that demonstrates that volume flowwill decrease during a Grade II & III stenosis (75%occlusion), as flow velocity first spikes beforedropping during a Graft IV stenosis (90%occlusion). (Adapted from Spencer P, Reid, J.M.,“Quantification of Carotid Stenosis withContinuous-Wave (C-W) Doppler Ultrasound,”Stroke 1979; 10(3) 326-330.)


VASCULAR SURGERY FLOW HANDBOOK


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Time is critical. How long do Transonic flow measurements take?No other credible intraoperative flow technology provides intraoperative measurements asquickly. Measurements are instantaneous once the flowprobe is applied to the vessel. Thesurgeon never has to take his or her eyes away from the operating field. After a couple ofseconds for flows to stabilize, flow can then be documented with a eight-second chartrecorder printout. Strengths of transit time ultrasound technology include its accuracy andthe immediacy of measurement. Surgeons can know flow instantaneously withoutdisrupting the course of the surgery and can then incorporate flow data into their operativestrategy.

Do I put the probe behind the vessel? What about fistulas coming off the graft?Yes, it is necessary to position the flowprobe around the vessel so that the vessel lies fullyin the lumen of the probe and is aligned as shown in Fig. D2. Measure-ment accuracy depends on accurate alignment of the reflector to theprobe body. One surgeon reports that they use flow measurement tofind fistulas after we have placed an in situ saphenous vein graft (see

page 18).

Does the flowprobe measure direction of flow?Yes, the flowprobes measure the amount and flow in either direction. Anarrow on the side of the probe indicates positive direction of flow (Fig. D2). Flow through thesensor running in the opposite direction is displayed on the flowmeter with a minus sign (If

the meter’s “Invert” button is not engaged.)

What does transit-time ultrasound flowmetryreally measure?Using wide-beam ultrasonic illumination, transit-timeultrasound measures pulsatile and average flowvolume directly. One ultrasonic beam undergoes aphase shift in transit time proportional to the averagevelocity of the liquid times the path length over whichthis velocity is encountered. With wide-beamultrasonic illumination (Fig. D3), the receivingtransducer sums (integrates) these velocity - chordproducts over the vessel's full width and yieldsvolume flow: average velocity times the vessel'scross sectional area. Since the transit time issampled at all points across the vessel diameter,volume flow measurement is independent of the flowvelocity profile. Ultrasonic beams which cross theacoustic window without intersecting the vessel donot contribute to the volume flow integral. Volumeflow is therefore sensed by perivascular probes evenwhen the vessel is smaller than the acoustic window.

Fig. D3: A non-constrictive Transonic®

flowprobe is applied around a vesselexposed during surgery to measurevolume flow. The flowprobe consists of aprobe body which houses ultrasonictransducers and a fixed acoustic reflector.The transducers are positioned on oneside of the vessel and the reflector is fixedat a position between the two transducerson the opposite side. Ultrasound couplantprovides full ultrasound passage withinthe flowsensing window.

Vessel

Reflector

ProbeBody Transducers

Fig. D2: The vesselmust be alignedwith the body of theprobe as shown.

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Don’t some surgeons still rely on palpation to indicate flow?Each surgeon has a choice of technologies for intraoperative assessment of blood flowand vascular stenosis. Every technology can be useful for optimizing surgical outcomes incertain circumstances, and each has distinct advantages as well as disadvantages.“Pulse,” while the least expensive, is the most suspect. When there is a severe partialocclusion, the proximal pulse will increase and the distal pulse will decrease but mostanastomotic errors cannot be detected by palpation.

Do I have to use gel to get a signal?Saline can be used in many instances when the vessel to be measured lies in an enclosedpocket. There may be enough saline already in the operative field to obtain good acousticcontact between the vessel and probe. (An indicator on the Transonic flowmeter indicatesthe quality of the ultrasound signal.) If necessary, the surgeon may add a little more salineto get good contact. If the surgeon is measuring flow in a bypass at an elevated location,gel can be used.

I’m concerned about vasospasm. Will using the flowprobe causevasospasm?Transonic Perivascular Flowprobes are designed with an open lumen so that the flowprobewill not constrict the vessel during measurement and contribute to vasospasm.Administration of papaverin is also advised to avoid vasospasm.

Isn’t intraoperative angiography still considered the GoldStandard for intraoperative assessment of blood flow??Intraoperative angiography is the accepted gold standard for vascular anatomy and theinternal diameter of vessels. Its use during surgery is not universally available. It iscumbersome and time consuming, and disrupts the flow of surgery. Angiography presentsa visual image of a region of the circulatory system and is invaluable during pre-operativediagnosis of circulatory stenosis and post-operative confirmation of their obliteration, but isno substitute for an intraoperative flowmeter. (During the pre- and post-operative diagnosis, a

doctor derives flow insufficiencies more from patient’s complaints than from the angiogram.)

How much does does the equipment cost to measure flow?The cost of transonic flow measurement is a minute addition to the overall cost of thesurgical procedure. One might well ask, “How much does it cost not to measure flow?” This“cost” must also consider: a patient’s extended morbidity if the surgery is unsuccessful; the costof longer hospital stays, more post-surgical tests and possibly reoperation. It is impossible toplace a cost figure on all these savings, and the value of an objective measure for the patient’srecord that confirms the surgeon’s clinical opinion. Transonic Flow-QC is quality control: Itprovides a functional objective measure to a vascular surgical procedure



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AV AccessJohnson, C.P., Zhu, Y., Matt, C., Pelz, C., Roza, A.M.,Adams, M.B., “Prognostic Value of IntraoperativeBlood Flow Measurements in Vascular AccessSurgery,” Surgery 1998;124:729-38. (1504AH)

Won, T., Jang, J.W., Lee, S., Han, J.J., Park, YS., Ahn,J.H., "Effects of intraoperative blood flow on theearly patency of radiocephalic fistulas," Ann VascSurg 2000; 14(5): 468-72. (2411AH)

Kelber, J., Deimez, J.A., Windus, D.W., “FactorsAffecting Delivery of High-Efficiency Dialysis UsingTemporary Vascular Access,” Am J Kid Dis1993;22(1)24-29. (365AH)

Jendrisak, M.D., Anderson, C.B., “Vascular Access inPatients with Arterial Insufficiency,” Ann Surg1990;212(2) 187-193. (185AH)

Ikizler, T.A., Pupim, L.B., Brouillette, J.R., Levenhagen,D.K., Farmer, K., Hakim, R.M., Flakoll, P.J.,"Hemodialysis stimulates muscle and whole bodyprotein loss and alters substrate oxidation," AJP2002;282(1):E107-16. (2636AH)

Peripheral BypassMeyerson, S.L., Moawad, J., Loth, F., Skelly, C.L.,Bassiouny, H.S., McKinsey, J.F., Sewertz, B.L.,Schwartz, L.B., “Effective Hemodynamic Diameter:An Intrinsic Property of Vein Grafts with PredictiveValue for Patency,” J Vasc Surg 2000;31:910-917.(1503AH)

Lundell, A., Nyborg, K., “Do Residual ArteriovenousFistulae after in Situ Saphenous Vein BypassGrafting Influence Patency?” J Vasc Surg1999;30:99-105. (1903AH)

Lundell, A., Bergqvist, D., “Prediction of Early GraftOcclusion in Femoropopliteal and FemorodistalReconstruction by Measurement of Volume Flowwith a Transit Time Flowmeter and Calculation ofPeripheral Resistance," Eur J Vasc Surg1993;7: 704-9. (293AH)

Alback, A., Roth, W.D., Ihlberg, L., Biancari, F.,Kepantalo, M., "Preoperative angiographic score andintraoperative flow as predictors of the mid-termpatency of infrapopliteal bypass grafts," Eur J VascEndovasc Surg, 2000;20(5): 447-53. 2062AHM

Ihlberg, L.H.M., Alback, N.A., Lassila, R., Lepantalo,"Intraoperative Flow Predicts the Development ofStenosis in Infringuinal Vein Grafts,” JJ Vasc Surg2001;34:269-76. (2064AHM)

Blankensteijn, J.D., Gertler, J.P., Brewster, D.C.,Cambria, R.P., LaMurglia, G.M., Abbott, W.M.,“Intraoperative Determinants of InfrainguinalBypass Graft Patency: A Prospective Study,” Eur JEndovasc Surg 1995;9:375-382. (518AH)

Belkin, M., Schwartz, L.B., Donaldson, M.C., Mannick,J.A., Whittemore, A.D., “Hemodynamic Impact ofVein Graft Stenoses and Their Prediction in theVascular Laboratory,” J Vasc Surg 1997;25:1016-1022. (924AH)

Schwartz, L.B., Belkin, M., Donaldson, M.C., Knox, J.B.,Craig, D.M., Moawad, J., McKinsey, J.F., Piano, G.,Bassiouny, H.S., Whittemore, A.D., “Validation of aNew and Specific Intraoperative Measurement ofVein Graft Resistance” J Vasc Surg 1997;25:1033-1043. (925AH)

Verhelst, R., Bruneau, M., Nocolas, A-L, Frangi, R.,Khoury, G.E., Noirhomme, P., Dion, R., “Popliteal-to-Distal Bypass Grafts for Limb Salvage,” Ann VascSurg 1997; 11:505-509. (1043AH)

Carotid EndarterectomyEckstein HH, Eichbaum M, Klemm K, Doerfler A,Ringleb P, Bruckner T, Allenberg JR, "Improvment ofCarotid Blood Flow after Carotid Endarterectomy--Evalution using Intraoperative Ultrasound FlowMeasurement," Eur J Vasc Endovasc Surg 2003;25:p168-174. (2579AH)

Gordon, I.L., Stemmer, E.A., Wilson, S.E.,“Redistribution of Blood Flow after Carotid Endar-terectomy,” J Vasc Surg 1995;22:349-360. (593AH)

Gordon, I.L., Weil, J., Williams, R.A., Wilson, S.E.,“Intraoperative Measurement of Javid Shunt Flowwith Transit-Time Ultrasound,” Ann Vasc Surg1994;8(6) 571-577. (371AH)

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