PICU Primer II

PICU Primer II

Kevin M. Creamer M.D.

Pediatric Critical Care

Walter Reed AMC

The Primer Outline

♦ Physiology

– Hypoxia / Hypoxemia– ABG’s and Acidosis

– Sodium and H2O metabolism

– Hemodynamics and Cardiopulmonary interactions

♦ ICU Care

– Postoperative issues

– Mechanical Ventilation

♦ Common Problems – Head trauma– Toxicology

Postoperative Issues

♦Borrowed in part from Akron syllabus♦Know the surgery

– what can you expect from a posterior spinal fusion is different than a tracheal reconstruction

♦Know the patient– Age, PMHx, Syndromes

♦Be there when they get out of the OR

Postoperative Evaluation

♦ABC’s♦Look at the breathing pattern♦Listen to the chest--breath sounds,

stridor?♦Listen to the heart--gallop, murmur?♦Feel the pulses--strong, weak, thready?

– Cap refill?, Extremity warmth?

The Anesthesia Report

♦“History of present illness” for surgical patients– Difficulties with induction or intubation?– Drugs used during case– Regional techniques employed?– Extubation-problems?

♦Vital signs- BP, HR, RR, SaO2, temp– Patients are frequently cold!

The Anesthesia Report

♦Ventilation parameters/difficulties♦Fluids--ins and outs♦Any “events”?♦Lines and tubes

Intraoperative Fluids

♦Pediatrician: “Why do they always get so much fluid?”

♦Anesthesiologist: “Because they need it”– maintenance + replacement of “third

space” losses• “third space” losses can be 15 cc/kg/hr

+ replacement of 3 X blood loss

Anesthesia and Fluid Balance

♦General anesthesia produces vasodilation and some decrease in myocardial contractility.

♦Increased intrathoracic pressure, and stress response to surgical stimulus, may lead to increased ADH production and decreased urine output

BLOOD loss and replacement

♦Blood loss is estimated ♦Transfusion Criteria - it depends

– Check Hct, HR, UOP, pH, ongoing loss, Hemodynamics …

♦When do you need Component Tx?– after a “massive” transfusion or

( 0.75-3.0 blood volumes)

Blood Products - How much?

♦PRBCs - 4cc/kg of will Hb 1gm/dl♦Platelets - 1unit/5kg will ⇑ count by

50000♦FFP - 10 ml/kg round up/down to

closest unit♦Cryoprecipitate - 1bag/every 5-10kg

Surgeons get extremely persnickety if you transfuse THEIR patient without letting them know ahead of time!

The Surgical Report♦ Since we are not surgeons we need to know

what they anticipate and worry about– Amount of pain – Third spacing– Possible complications

♦ Their wish list:– Extubate tomorrow, MRI at midnight– Special meds: antibiotic and stress ulcer

prophylaxis

The Surgical Report

♦What to touch and not to touch?– NG, foley, chest tube, rectum, etc.

♦Check all their orders for appropriate dosing and fluids– mg/kg/dose is not in surgical vocabulary

♦Who is in Charge? (Us vs. Them)♦Surgical POC?

– Interface with surgeons before they return to the OR in AM regarding the plan

Assessment of Fluid Balance:

♦Vital signs (HR/BP)♦Urine output♦Extremity warmth, CRT♦Acid-base status♦Occasionally invasive monitoring

– Remember the Liver!

Extubation Time?

♦Adequate airway (edema? ,Leak?)♦Maintain oxygenation and ventilation ♦Neurologically able to protect the

airway and maintain adequate drive.♦Small/young infants are at increased

risk of apnea– Especially if post-conceptual age <

50weeks

Sedation and Analgesia

♦Analgesia for painful diseases and procedures

♦Compliance with controlled ventilation and routine intensive care

♦Sedation for amnesia for the periods of noxious stimuli

♦Reduce the physiologic responses to stress

Sedation and Analgesia

♦The idea of titrating drugs to effect--there is no “dose”.– Keep in mind what the “target” response is.

♦Consider Round-the-clock Tylenol for 24-48 hours as adjunct– First PR dose may be 30-40 mg/kg

♦Anesthesia service manages Epidurals♦Consider a continuous drip

Drug Morphine Fentanyl Versed Ativan

Dose 0.05- 0.1mg/kg

0.5- 1.0mcg/kg

0.05- 0.1mg/kg

0.05- 0.1mg/kg

Timing(I/S)

5-10 min /2-4 hours

5-10 min/ 1-2

hours

5-10 min /1-2 hours

5-10 min /2-4 hours

Sideeffects

BP, H, A A, CWR BP, A BP, A

Reversal Narcan 2-10 mcg/kg

Narcan 2-10mcg/kg

Flumazenil0.1-0.2 mg

Flumazenil0.1-0.2 mg

BP: hypotension, H: Histamine, A: Apnea,

CWR: chest wall rigidity

Muscle Relaxants

♦ They provide ZERO sedation/analgesia. ♦ Indications (always relative)

– Mechanical ventilation where risk of extubation is great, or risk of baro/volutrauma is high

– Procedures such as central line placement or biopsy in the intubated patient

– Intractable intracranial hypertension (IF ICP being monitored)

Problems with Blockade

♦ Fluid retention♦ Long term weakness

– continuous infusions – most commonly the steroid based NMBs – myopathy associated with Atracurium– consider using cis-Atracurium

♦ Consider Train of Four testing♦ FREQUNTLY OVERUSED

♦NEXT UP

–Mechanical ventilation

This is not the NICU!

Lesson Learned:VALI –Predisposing Factors♦High lung Volumes

– With high peak pressure and alveolar overdistension

♦Repeated alveolar collapse and reopening

♦High inspired oxygen Concentrations♦Preexisting lung injury

Slutsky Am J Resp CCM, 1999, Dreyfuss Am J Resp CCM 1998

Mechanical Ventilation

♦Do’s and Don’ts– Avoid Overdistension and High Pressure by

limiting Tv– Avoid Hyperoxic Lung damage by turning FIO2

down (Sat 90% okay)– Avoid cyclic collapse by using PEEP to recruit

FRC and keep it above Closing volume♦ Infant high risk 2° high elastic recoil and

complaint chest wall

Zone of Overdistension

Zone of Atelectasis

Open Lung Strategy

Getting Started (Parameters)

Oxygenation Ventilation (MV)

PEEP Rate

I-time (flow) Tidal Volume (P)

FIO2

Getting Started (Mode)Volume Pressure

Pro’s Preserve MV Avoid PPEasy Familiar (NICU)

Decelerating Flow

Con’s PP ?? MV??Constant flow

Constant vs. Decelerating flow

Time

F L O w

Time

F L O w

Time

P R E S S U R E

Time

P R E S S U R E

Getting Started (Settings)

♦FIO2 - 50%, if sick 100%

♦It - minimum .5 sec, older kids 1 sec♦Rate - age appropriate 15 -30 to start♦Tv - 10ml/kg to start ♦Look / Listen / Ask♦PEEP - 4cm, higher if FRC

compromised

IT and Time Constants

• The time to fill each alveolus is determined by its time constant

• TC= Resistance X Compliance

• A Short IT decreases TV, or increases PIP

Full equilibration

IE

EI

TT

TPEEPPIPTMAP

+×+×= )()(

Mechanical Ventilation

♦First hour– CXR and “Blood Gas”– Watch peak pressures as compliance

estimate• PP << 20 ideal• PP 20-30 moderately P compliance• PP >> 30 severely P compliance• PP >> 35 high risk for VALI, DO

SOMETHING

Mechanical Ventilation

♦Change Tv only for inappropriate chest rise or for elevated inspiratory pressures (Don’t WEAN Tv)

♦Sedation to allow patient - ventilator synchrony (Paralytics aren’t required)

Monitoring adjuncts

♦Pulse oximeter♦End tidal CO2 - can use for Dead space

estimate♦ABG’s and CBG’s♦Calculate Compliance, A-a gradient,

Oxygenation Index (OI), check for Autopeep

♦Graphics - PV and flow-volume loops

Equations

♦Dead Space = 1 - (EtCO2/PaCO2)

♦Static Comp. = Tv/ (Pplat- PEEP)

♦A-a gradient =

– (Pb-PH2O) x FIO2 - (PCO2/.8) - PaO2

♦ OI = (Paw x FIO2 x 100)/ PaO2

When things go wrong♦ Don’t be a DOPE♦ Hypoxemia - PEEP to ⇑ FRC, to allow FIO2

wean to < 50%♦ Elevated peak pressures - suction, adopt

Permissive hypercapnia, consider changing to pressure mode

♦ Check circuit size– an inappropriately large circuit can gobble up

lots of tidal volume

PEEP

PIP

TI

RateFlow

Pressure

TimeTI TE

PEEP

PIP

Paw (Area Under Curve )increases with increasing:PIP, PEEP, TI/TE Ratio, Rate, and

Flow

Circuit compliance

♦When using volume ventilation the ventilator circuit or tubing will stretch – Neonatal 0.35 ml / cm H2O

– Pediatric 1.4 ml / cm H2O

– Adult 2.8 ml / cm H2O

♦This means the stiffer the lung the more volume is lost in the circuit

Mechanical Ventilation

♦ First day and beyond– Watch for fluid overload

• all patients on positive pressure ventilation retain lung water

– Assist patient efforts• Pressure support or volume support• Trigger sensitivity (age and disease appropriate)

– Treat underlying condition– Feed patient

Weaning

♦ Get condition under control♦ Stop paralytics (PEEP < 8)♦ Encourage patient’s efforts

�⇓ Rate (slow then fast)– add Pressure support (2/3 ∆P)

♦ Wean PEEP and PS slowly in 1-2 cm H2O increments

♦ Wean FIO2 to 30% if possible

Signs of weaning failure

♦Increased Work of breathing– fast spontaneous RR

– small spontaneous Tv

♦Increased FIO2requirement

♦Hemodynamic compromise

Time for Extubation?

♦Think SOAP–Secretions / Sedation / Spontaneous Tv

(>5ml/kg)

–Oxygenation <35%

–Airway - Maintainable?, Leak? , Steroids?

–Pressures - PP <25, PEEP < 5

Extubation success predictors

Variable Low risk <10% High Risk >25%

VTspont

>6.5 ml/kg <3.5 ml/kg

FIO2 <.30 >.40

OI <1.4 >4.5

PIP <25 >30

Khan, CCM 1996

Special situations I

♦Obstructive Diseases– Asthma and RSV Bronchiolitis

– Watch for air trapping / breath stacking• Low rate, larger Tidal volume, long

Expiratory time• check Autopeep• preserve I-time • Consider Heliox, Ketamine, Halothane

Special situations II

♦ARDS– Limit Tv accept hypercapnia– Increase PEEP for FRC– Prone positioning�⇑ CaO2 and tolerate lower Sat %

– consider High Frequency Oscillatory Ventilation>>> Surfactant>>> Nitric Oxide

Volutrauma

0.0061215Organ failure free days

0.00155%65.7%Off Vent by 28th Day

0.00739.8%31%Death

P - value

Traditional Tv Group

Low Tv Group

Variable

861 patients 6ml/kg vs 12ml/kg Tv

ARDS Study Group, NEJM, 2000

Biotrauma

♦ RCT 44 adults with ARDS– TV 7.6 vs. 11.1

– PP 24 vs. 31 cm H2O

♦ At 36° patients in low TV group had significantly lower levels of TNF and IL-1ra in both plasma and BAL fluid

0

5

10

15

20

25

30

35

40

StandardTV

Low TV

Organ Failure

Entry

3-4 days

Ranieri, JAMA,1999; Ranieri JAMA, 2000

Organ Failure

Special situations III

♦Head Trauma– Avoid Hypercarbia (PCO2 < 35)

– Avoid Hypoxemia

– PEEP may adversely effect venous return and ⇑ ICP

– Coughing/gagging extremely bad (Use paralytics)

Special situations IV

♦HFOV Indications– ARHF with OI > 13 for 6 hours– Contraindicated in High airway

resistance, ⇑ ICP, unstable hemodynamics

♦Part of an Open lung strategy with ⇑ Mean airway pressure and Tv < dead space

HFOV vs. CMV

♦Crossover study acute hypoxemic respiratory failure in children

♦HFOV 17/29 responded, 0/17 died♦CMV 10/29 responded, 4/10 died♦X-over to HFOV 11/19 survived♦X-over to CMV 2/11 survived

Arnold, CCM 1994

Ventilation Simulator

♦Not for the weak of heart

The EndMind what you have

learned. Save you it can.

Questions?