Administration of General Anesthesia for Outpatient Orthognathic Surgical Procedures

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J Oral Maxillofac Surg69:798-807, 2011

Administration of General Anesthesiafor Outpatient Orthognathic

Surgical ProceduresCharles F. Cangemi, Jr, DDS, MS*

The administration of anesthesia has shifted away from the traditional hospital setting to an enormous increasein the use of outpatient facilities. The development of short-acting anesthetics, advances in surgical tech-niques, and paradigm shifts accepting targeted hospital admission and preoperative testing have allowed theacceptance of outpatient anesthesia for a wide variety of surgical procedures, including orthognathicprocedures. Furthermore, the cost savings associated with office-based surgery and the declining insurancecoverage for procedures such as orthognathic surgery have helped to increase the demand for surgery in thissetting. The administration of anesthesia for orthognathic surgery in an outpatient setting requires preoper-ative preparation, preoperative patient assessment and selection, use of short-acting anesthetic agents andtechniques, presence of emergency drugs and equipment, appropriate recovery protocols and staff, and thepresence of adequate caregivers upon home discharge. Anesthetic techniques and agents allowing multipleorthognathic procedures to be performed in the outpatient setting are described.© 2011 American Association of Oral and Maxillofacial Surgeons

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arious factors favor outpatient surgery, includingisks associated with long hospital stays, such as nos-comial infection. It is estimated that there are 1.7illion hospital-associated infections that result in

pproximately 99,000 deaths annually.1 Currently,ore than 65% of surgeries are now performed in the

utpatient setting.2 Although the infection rate in theoutpatient setting is not completely established,length of stay is a principal factor in that risk.

In the early 1970s, outpatient anesthesia for medi-cal procedures was virtually nonexistent. Oral andmaxillofacial surgeons and dentists who provided out-patient anesthesia services were criticized by some inthe hospital community who believed that all patientswho received general anesthesia needed an extensivearray of preoperative screening tests and needed to stayin the hospital overnight. Patients routinely were admit-ted to the hospital the night before their surgery. Fromthe 1970s on, a number of studies were performed thatchallenged typical presurgical workup practices andhospital protocols. In 1981, a study by Wood and Hoe-

*Private Practice, Dental Anesthesiology, Charlotte, NC.

Address correspondence and reprint requests to Dr Cangemi, Jr:

University Oral and Maxillofacial Surgery Anesthesiology, 411 Billing-

sley Rd, Suite 105, Charlotte, NC 28211; e-mail: [email protected]

© 2011 American Association of Oral and Maxillofacial Surgeons

278-2391/11/6903-0025$36.00/0

aoi:10.1016/j.joms.2009.07.047

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kelman1,3 found no differences in complications in chil-ren regardless of whether they received a screeninghest roentgenogram. Other screening tests receivedimilar scrutiny with similar outcomes concerning theirecessity (or lack thereof). For example, Narr et al4

found that preoperative laboratory testing of more than3,000 patients did not provide any patient benefit. In astudy of 1,500 patients, Olsen et al5 found no differencesn morbidity between the control group or the grouphat underwent screening tests. As the evidence againsthe requirement of routine preoperative ECG, labora-ory testing, chest radiographs, and so forth has becomevident, routine testing of all patients has been sup-lanted with targeted testing based on the preoperativevaluation, patient age, and planned procedure.As cost savings were realized from elimination of

nnecessary preoperative screening tests, other ac-epted rules were challenged, such as the necessity totay overnight in the hospital after surgery, or evenhe necessity of admission the night before to ensureompliance with the directive of nothing by mouth.or hospital surgeries for which admission is antici-ated, it is now common for patients to be admittedn the day of surgery rather than on the previousight. Currently, 20% to 30% of surgeries are morningdmissions.6 As it has become apparent that theseost-saving changes in care have not resulted in in-reases in morbidity or mortality, the concept of safe,onvenient ambulatory surgery has become standard

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CHARLES F. CANGEMI, JR 799

Dentistry has an impressive record in all aspects ofanesthesia and is setting the standard with the provi-sion of outpatient orthognathic surgeries. Both theAmerican Dental Association and the American Med-ical Association credit the discovery of anesthesia tothe dental profession. Dr Horace Wells is creditedwith this discovery in 1844, with formal recognitionby the American Dental Association in 1864 and theAmerican Medical Association in 1870.

Historically, medical anesthesiologists were trainedto treat patients who would remain in the hospital fora long period after surgery. As the trend toward moreoutpatient surgery has increased, the anesthesia com-munity has improved the ability to provide anesthesiafor shorter postoperative stays. Because a majority oforal and maxillofacial surgery is performed on anoutpatient basis, the dental profession has always hadan incredible level of training and experience in themanagement of anesthesia in this setting. Currently,there are two categories of dentists who are eligibleby training and licensure to administer general anes-thesia: namely, oral and maxillofacial surgeons anddentist-anesthesiologists. The author is a dentist-anes-thesiologist who performs all anesthesia services formajor surgeries, such as orthognathic surgeries, majorbone grafting procedures, and cosmetic proceduresin an outpatient surgical setting. Dentist-anesthesiol-ogists are dentists who complete a comprehensive,hospital-based anesthesiology residency and aretrained in all areas of anesthesiology. They provideadult and pediatric anesthesia for a wide variety ofmedical specialties, including very large and challeng-ing cases such as transplant surgery, as well as forseverely medically compromised patients. As dentists,they have specialized knowledge of the proceduresperformed, the times needed for particular treat-ments, as well as a knowledge of relative post opera-tive discomfort and specific needs associated with theprocedures performed. Finally, many dentist-anesthesi-ologists are able to mobilize their equipment and trans-form virtually any dental office into a state-of-the-artoperating room, providing adult and pediatric anesthe-sia to the dental community. The safety of anestheticsprovided by dentist-anesthesiologists and oral and max-illofacial surgeons is very well documented, and morbid-ity and mortality are lower than hospital estimates.7

General Concepts for OutpatientOrthognathic Surgery

Successful outpatient surgery requires proper pa-tient selection, an appropriate surgical facility, all nec-essary surgical and anesthetic equipment, anesthesiadrugs and supplies, an emergency response protocol

facility needs to be of appropriate size to accommo-date the equipment and personnel required for theprocedure. A backup generator is encouraged in therare event of power failure. Anesthetic monitorsshould have battery backup, and a nonpowered emer-gency backup suction is required. A backup monitorshould always be available in case of monitor failure.Backup laryngoscopes, batteries, and bulbs should beimmediately available. Consideration of the possibilityof a difficult airway should always be considered, andlaryngeal mask airways, oral and nasal airways, andequipment for an emergency surgical airway shouldalso be immediately available. A portable oxygen sup-ply as well as a full array of nasotracheal tubes in adultand child sizes need to be present. The use of short-acting inhalational agents, ultra–short-acting narcot-ics, and proper techniques for rapid emergence andrecovery should be used to expedite patient dis-charge. Hypotensive anesthesia must be provided tominimize blood loss, and all appropriate anestheticdrugs, emergency drugs, antiemetics, and suppliesmust be maintained at levels that ensure that noshortage can occur. Miscellaneous supplies, such asanesthesia circuits, masks, circuit filters, intravenoussupplies, needles, and syringes must also be main-tained at appropriate levels and organized in a way toallow immediate procurement. Finally, because trig-gering agents are used, the possibility of a malignanthyperthermia episode must be considered, and dan-trolene sodium and sterile water must be stocked andimmediately available, along with a new circuit andCO2 absorber, should a crisis occur. Staff must beppropriately trained as to their role in an emergency,nd all anesthesia equipment should be checked dailyefore anesthesia and surgery. Appropriate recoveryacilities and monitors need to be present, includinghe provision of oxygen, suction, backup suction, andest room facilities, with recovery staff trained inppropriate monitoring and discharge criteria.

Patient Selection andPreoperative Evaluation

Because some patients are not well suited to out-patient surgery, all patients who are to have outpa-tient general anesthesia for a major surgical procedurein our surgical suite are evaluated for suitability in thissetting. The medical history is thoroughly reviewed, ahistory and physical examination are performed, andany necessary testing is completed. Questionabledrug allergies may result in referral for specific allergytesting or avoidance of the offending agent with asuitable alternative available. The anesthesiologistmay supply any drug to the physician performing thetesting if there is a question of allergy to a planned

800 ANESTHESIA FOR OUTPATIENT ORTHOGNATHIC SURGERY

necessary, consultations such as a cardiology workupand echocardiograms will be completed before sur-gery. Each patient will be assigned an American Soci-ety of Anesthesiologists physical status classification.All patients undergo a comprehensive physical exam-ination, including auscultation of cardiovascular andrespiratory systems. The airway is assessed, with aMallampati classification placed directly on the pa-tient’s anesthesia record. The age, weight, height,psychological assessment, airway status, physical sta-tus, and planned procedure are all considered in thedetermination of the appropriate anesthesia setting.Preoperative anesthesia and surgical information isextensively reviewed with the patient, and parent(s)or legal guardian as appropriate.

Certain patients are not appropriate candidates foroutpatient surgery. Patients who may likely have adifficult airway, such as those with limited opening,high Mallampati classification, limited cervical rangeof motion, or significant obesity must be evaluated todetermine whether management in the outpatientsetting is appropriate. Patients who are an ASA 3 orthose who have a significant history of chronic ob-structive pulmonary disease or other conditions thatmay require a delayed extubation or prolonged recov-ery are not suitable for the outpatient setting. Patientswith eating disorders, such as anorexia nervosa,should not have surgery performed in the outpatientsetting because of anesthetic concerns of hypoten-sion, bradycardia, hypovolemia, decreased plasmaproteins, and electrolyte disturbances that can lead toconduction abnormalities. The cardiovascular statusand functional status of the patient must be consid-ered, and all patients must be able to perform activi-ties requiring at least 4 metabolic equivalents for aer-

FIGURE 1. Hawk anesthesia machine with InVivo Research (Or-lando, FL) M12 patient monitor.

Charles F. Cangemi, Jr. Anesthesia For Outpatient OrthognathicSurgery. J Oral Maxillofac Surg 2011.

obic activity (Mets). The mental status of the patient,

and the ability to reasonably cope with the postoper-ative sensations of numbness, sore throat, and post-operative oozing, as well as the ability to follow post-operative directions, must all be considered. Inaddition, the ability of the caregivers of the patient tomanage the first night appropriately as well as toaccurately administer medications, such as narcoticsand antiemetics, needs to be considered to ensurethat the immediate home care is appropriate and safefor the patient. Appropriate patient selection helps toensure a smooth recovery and to limit after-hours callsfor routine postoperative events and sensations.

ANESTHESIA EQUIPMENT OPTIONS

The selection of anesthesia equipment is largely afunction of personal preference and space limitations.Although there is a large selection of full-sized anes-thesia machines available for purchase, their large sizeand weight may make them inconvenient or unsuit-able in the outpatient setting. Since most of the vol-ume of an anesthesia machine consists of storage andwasted space and is not integral to the function of theunit, it is possible to produce machines of very com-pact size and light weight. The author uses a Hawk(Anmedic, Galgbacksvagen, Sweden) tabletop anes-thesia machine (Fig 1). When viewed next to theauthor, the small size is quite apparent (Fig 2). Thecompact size allows excellent space use, and the unitcan be placed on a counter, allowing ease of cabinetand counter placement while allowing the use of afull featured anesthesia machine. Currently, all porta-ble compact anesthesia machines allow only one va-porizer to be mounted at a time, so if an operatorwants to use two or more different inhaled agents, thevaporizer must be switched, unlike full sized unitsthat can house two or three vaporizers depending on

FIGURE 2. Anesthesia machine with anesthesiologist. Note com-pact size and small footprint of machine.

Charles F. Cangemi, Jr. Anesthesia For Outpatient Orthognathic

CHARLES F. CANGEMI, JR 801

model. Vaporizers can be changed literally in sec-onds, however, so this limitation is trivial. As theagent sevoflurane can be used in mask inductions andhas desirable blood:gas solubility characteristics, theauthor prefers this agent for adult and child anesthe-sia. There are a number of options and brands ofmonitors, and most units can be equipped with end-tidal carbon dioxide and agent monitoring withoutincreasing their size. Monitors should have a batterybackup in the event of compete power failure, as wellas a printer to record ECG strips and to record vitalsigns, although vital signs should be charted on theanesthesia record rather than as a printout attached tothe record. Portable anesthesia machines are poweredby oxygen pressure and do not require electricity ex-cept if a ventilator is used. Finally, as a gas sampling linemust attach to the anesthesia circuit and must lead tothe input on the monitor, it is helpful if the machine andmonitor are in close proximity to each other. A com-plete anesthesia setup can be assembled using an ex-tremely small footprint, enabling a compact, fully func-tioning anesthesia delivery system.

Anesthesia Protocol: Technical andPharmacological Considerations

After confirming the NPO status and evaluation of therespiratory and cardiovascular systems, the progressionof the anesthesia, surgery, wake up, and recovery arereviewed with the patient. Emphasis is placed on thesensations encountered upon awakening after surgery,such as numb lips, sore throat, drowsiness, and thenecessity of suctioning and drinking in the recoveryarea. Any last-minute questions or fears of the patient areaddressed, and then the patient is escorted to a dressingroom to change into a surgical gown. The patient is thenescorted to the operating room.

MONITORING

Monitoring includes noninvasive blood pressure,pulse, pulse oximetry, skin temperature, electrocardio-gram, end-tidal carbon dioxide, and agent monitoring.Vital signs are recorded every 5 min throughout theprocedure. The elbows and ankles are padded withfoam to prevent pressure injury. Intravenous access isestablished and anesthesia induction is begun after pre-oxygenation. The anesthesiologist monitors the patientcontinuously through the entire procedure and emer-gence, and escorts the patient to the recovery roomafter appropriate recovery from anesthesia emergence.

INDUCTION

For a patient of reasonable preoperative anxiety,preoxygenation is performed and then induction isperformed via the intravenous route. For somewhat

nously while preoxygenation is occurring. For exces-sively fearful patients, administration of oxygen, ni-trous oxide, and sevoflurane is performed either to asedative level for intravenous placement, or a fullmask induction is performed, if warranted by theanxiety level of the patient. If a mask induction isperformed, the anesthesiologist will maintain the air-way while other anesthesia personnel or one of thesurgeons starts the intravenous line. Induction thencontinues with a narcotic, typically fentanyl initiallyfollowed by the start of a remifentanil infusion, andpropofol. Intubation may involve muscle relaxers, al-though a paralyzing agent is usually not required.Many patients, adults, and especially children, do notrequire muscle paralysis if the induction is accom-plished optimally. Paralysis is accomplished using ve-curonium if this is deemed necessary. Other agentssuch as succinylcholine or rocuronium can be used,but the author prefers vecuronium because of itsintermediate duration of action, rapid onset, and easeof titration in keeping patients paralyzed throughoutthe case. Succinylcholine is a malignant hyperthermiatriggering agent and has a number of undesirable sideeffects despite its classification as the drug of choicefor laryngospasm. Adverse effects with succinylcho-line include cardiac dysrhythmias such as sinus bra-dycardia, junctional rhythm, and sinus arrest. Theseare more likely to occur if a second dose is adminis-tered approximately 5 min after the initial dose. Otheradverse effects include hyperkalemia, fasciculation,muscle myalgia, increased intraocular pressure, in-creased intragastric pressure, increased intracranialpressure, and masseter muscle trismus. Nondepolar-izing muscle relaxants are generally preferred duringinduction and in maintenance of paralysis based onthe aforementioned concerns. The patient is manuallyventilated with oxygen, and intubation is then per-formed. All agents should be labeled and placed in alogical, orderly fashion (Fig 3).

AIRWAY MANAGEMENT

A number of steps are quickly performed at theintubation phase of the anesthetic. Before induction,the proper-sized endotracheal tube is determined.The nasal airway is sprayed with a vasoconstrictiveagent such as phenylephrine 1% spray, and the nos-trils are gently dilated with lidocaine lubricated nasalairways. A yankauer suction is always immediatelyavailable. A nonelectric backup suction is also imme-diately available. The endotracheal tube is warmed toimprove malleability and is gently passed through thenostril into the pharynx, and laryngoscopy is per-formed. As the anesthesiologist performs laryngos-copy, one of the surgeons provides cricoid pressureas needed until the tube is passed through the vocal

802 ANESTHESIA FOR OUTPATIENT ORTHOGNATHIC SURGERY

alization of the vocal cords typically allows passageinto the trachea without the necessity of Magills for-ceps. The cuff is inflated as appropriate, and properplacement is confirmed with a combination of auscul-tation, capnography, visual confirmation, presence ofchest rise, and water vapor appearing in the tube asthe patient exhales. The circuit is attached with filtersadjacent to the endotracheal tube and also to theanesthesia machine to ensure the avoidance of cross-contamination. An endotracheal tube extender is alsoattached. The endotracheal tube is secured at theappropriate depth by the surgical team to preventdislodgement, and the eyes are protected with oph-thalmic ointment and Tegaderm (3M, St. Paul, MN)coverage to prevent corneal abrasions (Fig 4).

The possibility of a difficult airway must always beconsidered and appropriate measures taken preoper-atively to ensure proper management should the needarise. Oral tubes should be immediately available inaddition to the standard nasal tubes should a differentendotracheal tube be necessary. One size larger andsmaller nasal endotracheal tubes should be immedi-ately available. A full airway setup tray is always avail-able next to the patient, and includes two function-ing laryngoscopes, checked preoperatively, an assort-ment of Macintosh and Miller blades, a Rusch View-max laryngoscope blade (Rusch, Teleflex Medical,

Syringe Placement

Paralysis reversal Epinephrine (Neostigmine and glycopyrrolate) Lidocaine Promethazine

Antibiotic Ondansetron

Phenylephrine Dexamethasone Vecuronium Succinylcholine Atropine Labetalol Meperidine or morphine Propofol Fentanyl Glycopyrrolate Midazolam

FIGURE 3. Authors syringe setup and placement for orthognathicprocedures.

Charles F. Cangemi, Jr. Anesthesia For Outpatient Orthognathic

Research Triangle Park, NC), oral and nasal airways,large and small Magills forceps, phenylephrine nasalspray, and lidocaine lubricant for the endotrachealtube and nasal airway (Fig 5). The emergency airwaykit should be stocked with spare batteries, an articu-lating laryngoscope, spare bulbs, emergency laryngealmask airways, emergency airways such as EsophagealTracheal Combitubes (Tyco-Kendall, Mansfield, MA)and King Systems LT-1 tubes (King Systems, Nobles-ville, IN), adult and child Viewmax laryngoscopeblades (Rusch), Endotrol endotracheal tubes (Covi-dien-Nellcor, Boulder, CO), and Parker Flex-it Direc-tional stylets (Parker Medical, Highlands Ranch, CO),should the airway prove difficult. Adult and childRusch Quicktrach (Rusch) kits are in close proximityif needed in the most severe airway emergency.

FIGURE 4. Patient intubated with eye protection and ET tubesecured.

Charles F. Cangemi, Jr. Anesthesia For Outpatient OrthognathicSurgery. J Oral Maxillofac Surg 2011.

FIGURE 5. Airway/IV tray setup. Note multiple laryngoscopes/blades, airways, and Magills forceps.

Charles F. Cangemi, Jr. Anesthesia For Outpatient Orthognathic

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The American Society of Anesthesiologists (ASA)Task Force on Management of the Difficult Airwaydefines a difficult airway as one with which a conven-tionally trained anesthesiologist has difficulty withmask ventilation, intubation, or both. Patients with adifficult airway are not always correctly identifiedpreoperatively. In a study by Langeron et al,8 difficultmask ventilation was correctly predicted among1,502 patients studied by anesthesiologists only 17%of the time. It has been reported by Caplan et al9 that34% of 1,541 liability claims were caused by adverserespiratory episodes. Inadequate ventilation (38%),esophageal intubation (18%), and difficult trachealintubation (17%) accounted for 75% of these undesir-able events. In the ASA closed claims study, this wasthe largest source of unfavorable outcomes. Difficultairway management begins with the analysis of riskfactors to help in predicting a difficult airway andfamiliarity with a number of advanced techniques andaids to manage this potential complication.

A number of factors can help predict a difficult air-way. Patients with a severe class II malocclusion, athyromental distance less than 6 cm (typically mandib-ular deficient, with a short, muscular neck), obesity,limited mandibular mobility, limited atlanto-occipitaljoint extension (normal is 35 degrees), a high archedpalate associated with a long, narrow maxilla, and a highMallampati class (3 or 4) are all at increased risk for adifficult airway. The Mallampati classification was devel-oped by Dr S. Rao Mallampati10 and has shown a signif-icant correlation of the airway class and the degree ofdifficulty of glottic exposure by direct visual laryngos-copy. Modification of the original Mallampati classifica-tion by Samsoon and Young11 has added a fourth clas-sification in which the view of the soft palate iscompletely masked by the tongue and only the hardpalate is visible. Dr Mallampati reports that in his ownpractice he uses four steps in his airway evaluation12: 1)

allampati classification, 2) thyromental distance, 3)obility of joints, and 4) observation of the head, both

rontally and in profile. Respiratory events are the largestource of anesthesia-related unfavorable outcomes, andhe incidence of failed intubations is estimated at 0.05%o 0.35%. As most airway-related mishaps occur becausehe difficulty of the situation was not properly antici-ated,13 the combination of thorough preoperative as-

sessment and backup plans cannot be overemphasized.

MAINTENANCE PHASE/AGENTS USED FORRAPID EMERGENCE

The development of short-acting anesthetics hasdecreased recovery times and enabled use of ambula-tory surgery for a greater number and wider variety ofsurgeries. The administration of the anesthetic mustbe performed with the goal of rapid emergence and

routinely executed. The selection of agents for induc-tion, paralysis, and maintenance are critical to therapid emergence and recovery required for successfulmultiple outpatient surgery.

The goal of induction is to quickly and safely inducegeneral anesthesia, passing through stage 2 withoutcomplications such as laryngospasm and to produceconditions optimal for rapid endotracheal intubation.Traditionally, the principal induction agent has been amember of the barbiturate class, such as sodium thio-pental at a dose of 3 to 5 mg/kg, or methohexital 1 to1.5 mg/kg. Barbiturates produce a number of predict-able, characteristic physiologic effects, includingdose-dependent respiratory depression, decreased ce-rebral metabolic requirements (CMRO2), lower intra-ranial pressure, decreases in cardiac output, sys-emic arterial pressure and peripheral vascularesistance, and increased heart rate.14 Large doses orrolonged infusions of barbiturates can result in sat-ration of their redistribution stores, resulting in pro-

onged recovery times.15 As with other intravenousypnotics, barbiturates have a rapid redistribution,ollowed by a much slower elimination. When he-atic enzyme systems are not saturated with a drug,he rate of elimination decreases according to firstrder kinetics; the elimination decreases as an expo-ential function of the drug’s plasma concentration.owever, with higher doses or prolonged administra-

ion, these hepatic enzyme systems can become sat-rated with elimination, becoming independent ofrug concentration (zero-order kinetics) and relyingn metabolic clearance, thus prolonging recovery.16

Furthermore, barbiturates possess much longer elim-ination half-lives than propofol. The elimination half-life of propofol is 1 to 3 hours, whereas that ofthiopental is 10 to 12 hours and that of methohexitalis 6 to 8 hours. Barbiturates possess no antiemeticproperties and can produce other undesirable effects,such as an increase in heart rate and hypertensionduring administration.17

The introduction of propofol has caused a tremen-dous decline in the use of barbiturates and has be-come the most widely used anesthesia inductionagent. Ideal pharmacokinetic and pharmacodynamicproperties make propofol the sedative/hypnotic drugof choice for general anesthesia. Propofol exhibitsrapid blood:brain equilibration after a bolus injection.The context sensitive half-time of a drug is the timerequired for the drug’s plasma concentration to fall50% after termination of an infusion that maintained aconstant plasma concentration.18 The context sensi-tive half-time of propofol is less than 15 min forinfusions lasting less than 5 to 6 h.19 This remainselatively constant, unlike with drugs such as etomi-ate and methohexital, which increase with infusion

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804 ANESTHESIA FOR OUTPATIENT ORTHOGNATHIC SURGERY

agent that has an antiemetic effect. It is primarilycleared by biotransformation in the liver, and its clear-ance is actually higher than hepatic blood flow. Witha rapid onset of 60 to 90 s and the desirable pharma-codynamic property of clear-headedness upon awak-ening, it satisfies most criteria as a near perfect induc-tion agent. Propofol can be used in a total intravenousanesthesia technique (TIVA), using a narcotic to bal-ance the anesthesia, resulting in a decreased amountof propofol necessary to maintain general anesthesia.Loss of consciousness occurs with propofol with aplasma concentration of approximately 3.5 �g/mL,

ut in the presence of moderate levels of opioids thatevel can be decreased to as low as 1 �g/mL.20 Theoal of achieving rapid emergence from anesthesiafter maintenance is generally accomplished with aombination of propofol induction, intravenous ul-ra–short-acting narcotic administration (remifentanil)nd low-dose sevoflurane.

Anesthesia MaintenanceThe development of the ultra–short-acting narcotic

emifentanil has helped advance the concept of am-ulatory anesthesia featuring rapid emergence andecovery. Remifentanil has many desirable qualitieshat render it an ideal agent for use in outpatient oralurgery. A remifentanil infusion in association withropofol and inhalational sevoflurane creates a bal-nced technique for orthognathic surgical cases per-ormed in an office environment. Remifentanil is anltra–short-acting intravenous opioid administered bycontinuous infusion. It is chemically related to the

entanyl family of short-acting phenylpiperidin deriv-tives but possesses a unique ester structure. As aelective mu opioid receptor agonist, it produces an-lgesia, sedation, and respiratory depression.21 It isnique among narcotics in that it is rapidly metabo-

ized by nonspecific esterases in plasma and tissue,hich accounts for its short duration of action. The

ontext-sensitive half-time of remifentanil is 3.65 minnd is independent of its duration of infusion.16 Other

opioids can reach a saturation of redistribution sites,resulting in prolonged time for plasma levels to de-crease when the infusion is stopped. With remifenta-nil, this saturation does not occur, regardless of thelength of time the drug is infused. Therefore, its useon a lengthy case will not result in a prolonged recov-ery. Remifentanil, when compared with fentanyl inoutpatient third molar surgery, resulted in improvedpostoperative emergence. Remifentanil allowed a fa-ster return to consciousness, shorter recovery time, ashorter reported duration of feeling the drug effects,and a significantly shorter time to return of baselineTrieger test scores, and patients rated the quality oftheir anesthetic higher.22 Patients with pseudocholin-

he rate of remifentanil metabolism, and recovery isot affected. Remifentanil dosage requirements de-rease with advancing age. Electroencephalographicnalysis indicates that the opioid requirement in thelderly can be as little as one-third of that requiredith a younger individual to achieve the same anes-

hetic effect.23,24 Current guidelines recommend theremifentanil dose should be decreased by one-half forpatients by the age of 50 yrs compared with a patientof 21 yrs.25 Generally, remifentanil is used at an infu-sion rate of 0.01 to 0.1 �g/kg/min for sedation, and0.1 to 1 �g/kg/min for general anesthesia cases. Theprotocol established for orthognathic surgery casestypically administers remifentanil in the 0.1 to 0.15�g/kg/min range in conjunction with sevoflurane0.8% to 1.2% range. A summary of the general anes-thesia technique is provided in Table 1.

SHORT-ACTING INHALATIONAL AGENTS

Properties of ideal inhalational agents include rapidinduction and emergence, maintenance of cardiovas-cular stability, and a relative absence of detrimentalside effects. Inhalational agents provide an opportu-nity to achieve a mask induction for children or adultspossessing elevated anxiety. Sevoflurane is the pri-mary inhalational gas used for general anesthesia in anoffice setting whether it is for major surgical cases orpediatric needs. Sevoflurane is administered in se-lected inductions and maintenance, in conjunctionwith remifentanil. Sevoflurane is the preferred inhala-tional agent based on the principle of anesthetic sol-ubility. Solubility of inhaled agents is stated as parti-tion coefficients that define the distribution ratiobetween two phases with identical partial pressures.Blood:gas partition coefficients and tissue:blood par-tition coefficients are commonly referenced and canhelp to predict speed of induction and wakeup froma particular agent. A higher blood:gas coefficient cor-relates with a greater amount of agent that must bedissolved in the blood before the partial pressure ofthe agent in the lungs equilibrates with that of thebrain. Therefore, an agent with a lower coefficient ispreferred for speed of induction and emergence. Theblood gas coefficients for common inhaled agents areas follows: nitrous oxide 0.46, desflurane 0.42, sev-oflurane 0.68, isoflurane 1.4, and halothane 2.4.26 Onthis basis, agents such as halothane and isoflurane canbe expected to have a longer equilibration and alonger emergence from anesthesia after they are dis-continued. This issue is not as critical for short-anes-thesia cases, but as the duration of the anestheticbecomes longer, agents with higher solubility yield asignificantly longer recovery. Recovery from desflu-rane or sevoflurane anesthesia occurs almost twice asrapidly as recovery from halothane or isoflurane.27

With the use of lower dosages of inhaled agents and a

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remifentanil infusion, recovery from anesthesia canbe relatively rapid, enabling multiple cases to be ac-complished in a single day.

HYPOTENSIVE ANESTHESIA

Another technique routinely used in outpatient or-thognathic surgery is hypotensive anesthesia to helpcontrol the amount of bleeding and to provide thesurgeons with a more desirable surgical field. Thereare a number of ways to induce deliberate hypoten-sion during the maintenance phase of anesthesia.These include increasing the concentration of volatileanesthetics, or administering drugs from several dif-ferent pharmacological classes such as labetalol (�-

locker), sodium nitroprusside (direct relaxer ofmooth muscle via generation of nitric oxide), nitro-lycerin (capacitance vessel dilator), trimethaphansympathetic ganglia blocker), and esmolol (�-locker). The mean arterial pressure lower limit is 55o 60 mm Hg to ensure preservation of cerebral andenal blood flow.

Because no drug is devoid of side effects, these muste considered in the choice of technique for deliberateypotensive anesthesia. Sodium nitroprusside must beiven by infusion and can produce rebound hyperten-

Table 1. ANESTHESIA TECHNIQUE SUMMARY

Preoperative history and physical, preoperative equipmentPatient preparation-monitor placement, determination of p

nesthesia induction after preoxygenation� Midazolam sedation (1-5 mg; 0.025-0.1 mg/kg)� Fentanyl 50-200 ug (2-3 ug/kg)� Start remifentanil infusion(0.1-0.2 ug/kg/min)� Propofol induction (2-2.5 mg/kg)� If paralysis is desired, administer vecuronium (0.08� Ventilate with 100% oxygen, place oral or nasal air

Intubation- warm endotracheal tube, spray nasal passages with v- dilate nasal passages with lidocaine lubricated nasal- intubate, with backup laryngoscopes, fiberoptic blad

available- inflate cuff, connect circuit filter and connector- confirm proper placement by capnography, ausculta

exhales- start sevoflurane at 2%

Maintenance- maintain remifentanil infusion, reduce sevoflu- Initial hypotensive anesthesia utilizing remifentanil in- Administer steroid (typically dexamethasone 8 mg)- Administer antibiotic- Monitor neuromuscular blockade via train-of-four rat

Emergence- discontinue inhaled anesthetic and remifentanil infus- reverse muscle paralysis as necessary using neostigm- administer ondansetron 4 mg (0.1 mg/kg for children- perform orogastric suction, remove headwrap, rinse- extubate awake, administer 100% oxygen via facema

Charles F. Cangemi, Jr. Anesthesia For Outpatient Orthognathic

ion, cyanide and thiocyanate toxicity, intracranial hy-

ertension, blood coagulation abnormalities, increasedulmonary shunting, and myocardial, hepatic, and skel-tal muscle oxygen depletion.28 Nitroglycerin also muste administered by continuous intravenous infusion. It

s adsorbed by plastic and must be administered from alass bottle or from a high-density polyethylene syringe.t can also cause pulmonary shunting, increased cerebrallood volume, and brain swelling.29 Trimethaphan

blocks sympathetic ganglia, which produces vessel re-laxation, decreasing arterial blood pressure. It can re-lease histamine, causing bronchospasm, and can in-crease intracranial pressure.

Esmolol is a �1 selective blocker with a half-life ofpproximately 9 min. Given by bolus, this very shortalf-life makes multiple administration mandatory, limit-

ng operator desire to choose this agent. Esmolol andabetalol have the benefit of avoiding dilation of theerebral vessels, do not increase heart rate, do not causeebound hypertension, and produce no toxic metabo-ites.30 Labetalol blocks �1, �2, and �1 receptors. Theratio of � to � blockade is 1:7 when given intravenously.This receptor blockage combination produces a de-crease in peripheral vascular resistance and arterialblood pressure. The blood pressure decrease is not metwith reflex tachycardia and cerebral blood flow, and

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806 ANESTHESIA FOR OUTPATIENT ORTHOGNATHIC SURGERY

duration of effect of 2 to 4 hours and ease of adminis-tration by boluses of 5 to 20 mg, labetalol is easilytitrated and an extremely useful agent in hypotensiveanesthesia production in the outpatient setting.

Orthognathic surgery usually does not produce rapidmoment-to-moment blood pressure changes; there is nomajor arterial clamping, and the procedure is not likelyto cause sudden cardiovascular changes, fluid shifts, orrapid episodes of major blood loss. For these reasons,and because patients undergoing outpatient surgery arecarefully screened and do not have severe pre-existingcardiovascular disease or hemodynamic instability, thereis no need for an arterial line placement to monitorblood pressure. Furthermore, if the anesthesiologist orsurgeon desires the immediate beat-to-beat arterialblood pressure without the risks of arterial line place-ment, noninvasive continuous blood pressure monitor-ing with the T-Line® Tensymeter® (Tensys Medical, SanDiego, CA) has been shown to provide pressures asaccurately as invasive radial artery monitoring.32

EMERGENCE

Sevoflurane and remifentanil should be discontin-ued as the surgical procedure nears completion withapproximately 10 min remaining. The rapid reversalof these agents allows decreasing anesthetic depthwhile closure is completed, dressings placed, anddrapes removed. Longer-acting parenteral narcoticscan be administered slowly to a titrated dose as thepatient’s pain perception will increase quickly afterthe remifentanil is discontinued.

Prevention of Postoperative Nauseaand VomitingA number of techniques and agents are used to help

prevent postoperative nausea and vomiting (PONV).Higher-risk patients include female patients, non-smokers, and patients with a history of motion sick-ness or postoperative nausea and vomiting. Orogas-tric suction may be helpful after throat pack removalto evacuate stomach contents, and ondansetron canbe administered to help prevent nausea and vomiting.The adult dose of 4 to 8 mg or pediatric dosing of 50to 100 �g/kg is given near the end of surgery formaximum effectiveness. Dexamethasone given tocontrol postoperative edema is also effective in pre-vention of PONV. Agents that bind to the 5-HT3 re-eptor in the chemoreceptor trigger zone (CTZ), suchs ondansetron, are beneficial in prevention of PONV.ack of adequate hydration also increases this risk.lthough antihistamines are also useful in this regard,

heir disadvantages, including sedation, urinary reten-ion, blurred vision, and delayed recovery room dis-harge, typically limit their use in the outpatient set-ing. Benzamides such as metoclopramide block D2

receptors in the gastrointestinal tract and in the

chemoreceptor trigger zone. Metoclopramide in-creases lower esophageal sphincter tone and en-hances gastric motility, although studies on the effi-cacy for control of nausea have been mixed in theirconfirmation of clinical effectiveness. A meta-analysiscomparing metoclopramide with droperidol and on-dansetron concluded that it was inferior to each drugfor PONV prevention in adults and children.33 Foradult patients who received general anesthesia andexperienced postoperative nausea and vomiting, on-dansetron at a dose of 4 mg was superior to metoclo-pramide 10 mg in providing complete control of theevent and was associated with greater patient satis-faction.34 Phenothiazines, such as promethazine,

lock D2 receptors in the CTZ and are effective in therevention and treatment of PONV. However, be-ause of their sedating properties, their use in theutpatient setting is better served as a drug of backup

f the initial prevention fails. The butyrophenone dro-eridol, which is a strong D2 receptor antagonist, is aotent antiemetic and has been used extensively innesthesia. In December 2001, the Food and Drugdministration issued a Blackbox warning stating thatroperidol use has been associated with QT segmentrolongation and torsades de pointes and has resulted

n fatal arrhythmias. Although this is being chal-enged, the recommendation that all patients have a2-lead electrocardiogram before droperidol adminis-ration, to ensure than men do not have a QT intervalreater than 440 ms and that women do not have aT interval greater than 450 ms, and to then beonitored for 2 to 3 h after administration, has greatly

urtailed the use of this drug. The combination of ateroid and ondansetron administered intraopera-ively, combined with postoperative Phenergan if re-uired, is a typical regimen for preventing nauseand/or vomiting.

RECOVERY

Patients are encouraged to drink fluids in recoveryand repeatedly undergo suctioning as necessary tohelp prevent ingestion of blood that has oozed fromintraoral surgery sites. This combination of pharma-cologic agents, combined with close recovery super-vision, allows a rapid recovery with minimal instancesof postoperative nausea and vomiting.

In the recovery area, the patient is placed in a verycomfortable reclining chair. Monitors are attached, in-cluding those for electrocardiography, pulse monitor-ing, and pulse oximetry. A warm blanket is provided ifthe patient desires. Vital signs are recorded in the recov-ery section of the anesthesia record in 15-min intervals.The patient is kept well suctioned, and the recoverynurse helps the patient start oral intake of clear liquids.The Modified postanesthesia Discharge Scoring (PADS)

CHARLES F. CANGEMI, JR 807

simplified system measures vital signs, ambulation, nau-sea and vomiting, pain, and surgical bleeding. All itemsare graded as 0, 1, or 2, with a value of 2 being the mostdesirable score in each category. For example, a painscore of 2 represents minimal pain, a score of 1 ismoderate pain, and a score of 0 represents severe pain.Out of a perfect score of 10, a score of 9 or 10 isrequired for discharge. Recovery requirements for dis-charge include stable appropriate vital signs, control ofnausea and vomiting, appropriate pain control, appro-priate mental status, adequate hemostasis, ability todrink, ability to ambulate suitable for home discharge,presence of appropriate caregivers for discharge, andpatient agreement of discharge readiness.

When recovery parameters are met, the patient’sescort(s) is brought back to the recovery area andpostoperative and postanesthetic instructions areagain reviewed. Written postoperative instructionsare also provided, which include a number for after-hours calls should they be necessary. Escorts are in-structed to drive their car to the rear exit where therecovery room is located, and the patient is escortedvia a wheelchair to the car for transport home.

In conclusion, surgical advances and the develop-ment of superior, short-acting anesthesia agents haveresulted in the administration of orthognathic surgeryroutinely in an office-based environment. With carefulanesthesia administration, a thorough understandingof the surgical procedures, and proficiency in titrationand rapid anesthesia emergence techniques, outpa-tient anesthesia can be efficiently achieved.

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