Historical Perspective

Deliberate hypotensive anesthesia (DHA) to provide a less bloody field and better operative conditions was first proposed by Harvey Cushing in 1917 for neurosurgical procedures.⁵⁸ Since then, a spectrum of pharmacologic agents (e.g., nitroglycerine, calcium-channel blocking agents, short-acting beta-adrenergic blockers, purine compounds) and techniques have been used in a variety of combinations in an attempt to accomplish the same objectives.*

In 1950, Enderby and colleagues demonstrated the value of DHA to reduce blood loss in a series of 35 patients.78–81 Eighteen of the 35 (51%) were judged to have an excellent reduction in blood loss during deliberate hypotension, and 8 of the 35 (23%) were judged to have a moderate reduction. The authors attributed this inconsistent effectiveness to individual vascular responses to the hypotensive drugs that were used. They surmised that bleeding at the surgical site could be further minimized if the wound itself was kept uppermost (rather than dependent) through the use of operating room table positioning (e.g., reverse Trendelenburg position for head and neck procedures). Through special positioning, arterial vessels in the operative field would have less pressure, veins would drain more easily, and thus bleeding at the surgical site should be less.

One of the earliest studies to quantify reductions in blood loss with DHA was performed by Eckenhoff and Rich, who completed research in patients who were undergoing a variety of operations, including rhinoplasty, portacaval shunt, and craniotomy for aneurysm.72,73 Half of the patients underwent DHA (n = 115), and the other half (n = 116) went without hypotension. For each of the procedures, blood loss decreased by 50% or more with hypotension techniques. This was the first DHA study to measure blood loss with the use of a control group. By doing so, it greatly added to the power of the research confirming the value of DHA.

Evidence supporting the use of DHA to reduce blood loss has most commonly been found in studies of orthopedic procedures. Thompson and colleagues studied hypotensive anesthesia to reduce blood loss during total hip arthroplasty.²⁵⁵ The mean arterial pressure (MAP) of the patients (n = 30) was reduced to 50 mm Hg. The techniques used to do this included sodium nitroprusside (n = 12) and high inspired concentrations of halothane (n = 9); a control group of patients (n = 9) was normotensive. Blood loss was 1200 mL for the normotensive control subjects but only 400 mL for both hypotensive groups. No anesthesia-specific complications were seen. In 1979, Eerola and colleagues completed a controlled study of 55 patients who were undergoing total hip arthroplasty.⁷⁶ They found that the 38 patients who were given pentolinium tartrate and halothane for DHA had less blood loss. That same year, Vazeery and colleagues studied patients who were undergoing total hip replacement (n = 25). The patients were given sodium nitroprusside to lower arterial blood pressure.²⁶² They had significantly less blood loss than the control group (n = 25), which was not undergoing deliberate hypotension. The value of DHA to reduce blood loss has also been confirmed for other procedures, including craniotomy, middle-ear surgery, radical cancer operations, and a variety of head and neck surgeries.

Didier and colleagues suggested that the depression of cardiac output correlated better with a dry field than did arterial blood pressure.⁶⁶ To determine whether a decrease in MAP or cardiac output was the primary cause of the decreased blood loss, Sivarajan and colleagues studied “healthy” (American Society of Anesthesiologist I) subjects (n = 20) who were undergoing bilateral sagittal split ramus osteotomies of the mandible.²³⁹ Cardiac output decreased 37% with the use of trimethaphan, but it decreased only 27% with sodium nitroprusside. Interestingly, blood loss was similar for both groups, although cardiac output was two times greater with nitroprusside. The authors concluded that blood pressure rather than cardiac output was the primary determinant of how much blood was lost.

Techniques to Induce Deliberate Hypotensive Anesthesia

Currently, the general consensus is that most patients will have less blood loss if the MAP is decreased to 50 mm Hg to 65 mm Hg in the surgical field. It is also believed that patient positioning and attention to ventilation will significantly influence venous return and therefore play important roles in minimizing blood loss. Clinical studies have focused on the use of a variety of specific drugs and combinations of drugs to keep the arterial blood pressure at the surgical site at the level believed to significantly decrease blood loss (i.e., 50 mm Hg to 65 mm Hg).

Body positioning (e.g., reverse Trendelenburg position for head and neck procedures), the hemodynamic effects of mechanical ventilation (e.g., maintaining normal or low carbon dioxide [CO₂] levels), and changes in the heart rate and the circulatory volume are factors that can be manipulated with drugs to lower blood pressure in the surgical field to the desired level. The effective use of these physiologic maneuvers helps to decrease the dose of potentially toxic drugs that are needed to produce the preferred level of hypotension.

The ideal agents for inducing hypotension should have the following characteristics: 1) ease of administration; 2) a predictable and dose-dependent effect; 3) rapid onset; 4) rapid recovery from effects; 5) quick elimination without the production of toxic metabolites; and 6) minimal effects on blood flow to the vital organs. Many anesthetic and vasoactive drugs have been used successfully in clinical practice to induce DHA for orthognathic procedures. These agents primarily include volatile anesthetics; direct-acting vasodilating drugs; beta-adrenergic receptor–blocking drugs; and combined alpha- and beta-adrenergic receptor–blocking drugs. Examples of such agents include sodium nitroprusside, nitroglycerin, esmolol, and labetalol.

Clearly, one can decrease MAP by increasing the amount of inhaled anesthetics such as sevoflurane, isoflurane, and desflurane. Certain drugs that permit moment-to-moment controlled blood pressure are the most popular. The differences in pharmacologic properties among these agents suggest that combinations of these drugs may provide a better pharmacologic profile than could be provided by any agent used alone.²³⁴

Effects of Deliberate Hypotensive Anesthesia on Organ Function

DHA decreases arterial blood pressure by decreasing cardiac output, by decreasing systemic vascular resistance, or by decreasing a combination of the two. Cardiac output must remain sufficiently high not only to provide adequate oxygen and energy substrates to vital organ systems but also to remove metabolic waste products before any accumulation can cause tissue damage. The effect of DHA on cardiac output depends on the balance of its effects on preload, afterload, myocardial contractility, and heart rate. Homeostatic mechanisms also come into play. Other important factors include the physical condition of the specific patient, the anesthesiologist’s administration of additional drugs, and the pattern of ventilation used intraoperatively. The constant assessment of the patient’s intravascular fluid volume throughout surgery is also required to ensure optimal vital organ function.

Inadequate oxygen supply to the brain and myocardium as a result of inadequate tissue blood flow or perfusion pressure is the principal hazard of DHA, particularly with regard to the effects on cerebral metabolic homeostasis.* Studies to date have shown that the responsible use of DHA does not produce permanent changes in cerebral hemodynamics. For example, the cognitive performance of elderly patients on psychological tests given several days after total hip arthroplasty that involved DHA did not differ from their performance before surgery. The current clinical rationale for studying a lower limit for MAP (e.g., 50 mm Hg to 55 mm Hg) in normotensive patients is based on the belief that this range represents the lowest MAP at which autoregulation of the cerebral blood flow is still intact. However, for chronically hypertensive patients or for patients who are older, the curve is thought to shift to the right. In other words, a higher MAP is required in these individuals to maintain autoregulation. The partial pressure of carbon dioxide in the blood (paCO₂) is also an important consideration during DHA. This is because cerebral blood flow changes linearly with paCO₂. Whether one drug is better than another for preserving cerebral blood flow is debated.

The preservation of cardiac function is essential, but it is known to be altered by DHA techniques.^† Interestingly, cardiac function is better preserved with isoflurane than with equal hypotensive doses of halothane. Studies have shown that isoflurane is suitable for healthy patients who are undergoing DHA. Clinical studies also show that the cardiovascular effects of general anesthetic doses of propofol are similar to those of isoflurane. During deliberate hypotension, the maintenance of an oxygen supply that is sufficient for the metabolic needs of the myocardium is of primary importance. As a general rule, patients with known or suspected ischemic heart disease should not undergo DHA.

Renal blood flow normally equals 20% to 25% of cardiac output. Renal circulation is greatly influenced by autoregulatory mechanisms.61,110,159 Clinical studies suggests that normovolemic patients typically experience the rapid recovery of urine production after the discontinuation of DHA.²⁵⁵ Thompson and colleagues could find no significant changes in serum creatinine, blood urea nitrogen, or serum or urinary electrolytes for patients (n = 30) who had undergone DHA.²⁵⁵

Monitoring During Induced Deliberate Hypotensive Anesthesia

Beat-to-beat measurement of arterial blood flow is mandatory for patients who are undergoing clinically significant deliberate decreases in blood pressure. The usual practice is to insert an arterial catheter for the continuous monitoring of blood pressure. Perhaps most importantly, the catheter allows for the intermittent sampling of arterial blood for acid–base status (i.e. metabolic acidosis). It also allows for the confirmation of adequacy of oxygenation and ventilation, and for serial hematocrit measurements. Electrocardiographic monitoring is also essential for detecting signs of inadequate myocardial perfusion or oxygen delivery, such as S-T segment or rhythm changes. The correlation between end tidal CO₂ and paCO₂ is considered somewhat unreliable during hypotension. Nevertheless, capnography still provides useful information during DHA. It may also help to avoid hyperventilation and its resultant hypocapnea, which could be harmful; the decrease in paCO₂ could further reduce cerebral blood flow during moderate hypotension. Pulse oximetry and temperature monitoring should also be routinely used, and the measurement of urine output is also essential. Serum electrolyte, blood gas, and hematocrit levels should also be measured at intervals.

Complications Associated with Deliberate Hypotensive Anesthesia

The precise incidence of complications with the use of DHA is difficult to determine.19,75,41,152,179,248,253 Current data regarding non-fatal complications indicate that hypotension of 50 mm Hg to 65 mm Hg is not a risk factor for young healthy patients (American Society of Anesthesiologists [ASA] 1 and 2). Alternatively, for those individuals with underlying organ dysfunction, the use of DHA may put them at increased risk. Thus, all potential candidates should undergo a complete history and physical examination before surgery. The decision to use DHA should not be made without careful preoperative consideration of patient-specific risk factors.

Special Considerations for the Orthognathic Patient

Before beginning an orthognathic procedure, the logistics of patient positioning, the expected length of the surgery, and the confirmation of patient-specific risk factors for DHA should be discussed by the anesthesiologist and the surgeon.²⁶⁴ Better drugs, more accurate monitoring, a greater level of experience with the techniques, and the consistency of the surgical procedures themselves have permitted a higher percentage of patients to benefit from DHA.* Nevertheless, relative contraindications include a history of cerebrovascular or cardiovascular disease, renal dysfunction, liver dysfunction, peripheral vascular disease, and severe anemia. Fortunately, the orthognathic patient rarely suffers from these dysfunctions. Exceptions include older individuals who are undergoing orthognathic surgery for the treatment of obstructive sleep apnea.^228,261 Given current demographics, this is likely to represent an ever-increasing patient population (see Chapter 26).

Tranexamic Acids

Tranexamic acid is a synthetic amino acid that inhibits fibrinolysis and that has been shown to reduce blood loss and the need for blood transfusion during specific surgical procedures, including total knee arthroplasty, spine surgery, cardiac surgery, and orthognathic surgery.* It has also been used for the treatment of postoperative bleeding in anticoagulated patients after oral surgery (e.g., the extraction of teeth).^32,212 Senghore and Harris showed that a single intravenous preoperative dose of tranexamic acid was effective for preventing excessive postoperative bleeding in healthy adult patients who were undergoing third molar extraction.²³²

Choi and colleagues completed a double-blind, randomized, controlled trial to study the effects of tranexamic acid on blood loss during orthognathic surgery.⁵¹ This trial included 73 consecutive patients who were undergoing bimaxillary orthognathic osteotomies. Each study patient received either a bolus of tranexamic acid (20 mg/kg) or a placebo (normal saline) intravenously just before surgery. All patients underwent DHA in accordance with standard hospital protocol. Intraoperative blood loss, operative time, the transfusion of blood products, and perioperative hemoglobin and hematocrit levels were recorded. The total blood loss and the blood loss during the maxillary (Le Fort I) procedure were reduced significantly in the group that received tranexamic acid as compared with the control group. The difference in blood loss during maxillary surgery was 428 mL versus 643 mL. The difference in total blood loss was 878 cc versus 1257 cc. The authors concluded that the use of a preoperative intravenous bolus of tranexamic acid (20 mg/kg) reduces blood loss as compared with a placebo during bimaxillary orthognathic osteotomies.

Desmopressin

Desmopressin acetate is an analog to the naturally occurring hormone vasopressin.4,114,115,138,147,222,225,245 It enhances the vascular endothelial cell release of a number of compounds, including high multimetric von Willebrand factor, factor 7c, factor 7ag, and tissue-type plasminogen activator. Desmopressin by itself has been suggested to be the factor that is responsible for the increased hemostatic activity seen in patients with liver dysfunction and uremia. Additional observations indicate that desmopressin may improve platelet function.

Both of these hemorrhage depressors—desmopressin and tranexamic acid—have been used in combination with DHA during orthognathic surgery at the University of Göteborg Hospital since 1999. Zellin and colleagues retrospectively evaluated and compared the total perioperative blood loss for a group of patients who were assigned to either DHA or a combination of DHA and the use of both of these hemorrhage depressors (i.e., desmopressin and tranexamic acid).²⁷⁶ Thirty orthognathic patients who were consecutively operated on via a standardized Le Fort I osteotomy were assigned to either the control group (n = 15) or the treatment group (n = 15). Both groups underwent DHA. The treatment group received additional hemorrhagic depressors (i.e., both tranexamic acid and desmopressin). The mean blood loss was 740 cc in the control group and 400 cc in the treatment group. This was a statistically significant reduction in blood loss in the treatment group (1 g tranexamic acid intravenously and 0.3 µg per kilogram of body weight of desmopressin subcutaneously).

Background

For individuals who are undergoing complex orthognathic surgery (i.e., Le Fort I and sagittal split ramus osteotomies of the mandible)—often in combination with other simultaneous procedures (e.g., genioplasty, liposuction, septoplasty, inferior turbinate reduction, removal of wisdom teeth)—a preoperative doctor–patient discussion of the need for intraoperative blood replacement is not just an academic issue.92,103,107,149,163,201 Published studies indicate that individuals who are undergoing bimaxillary surgery require blood replacement in the range of 2.5% to 75%.^{15,64,138,142,148,156,200,218,223,226,235,259,274} Rummasak and colleagues retrospectively studied patients who underwent bimaxillary osteotomies (n = 208) during a 4-year timeframe from 2005 to 2009 at a single institution. The authors reviewed possible factors for intraoperative blood loss and looked for statistical significance. They documented that, with consistent anesthesia techniques, the two factors of greatest importance for blood loss were 1) the experience of the surgeon and 2) the overall operative time.²²³

Madsen and colleagues conducted a prospective study to evaluate the predictive value of the viscoelastic properties of whole blood samples collected preoperatively in relation to intraoperative blood loss in patients who were undergoing orthognathic surgery (n = 41). They concluded that, with other variables controlled for, the etiology of intraoperative bleeding can be predicted by means of preoperative thromboelastography. This is a global method that addresses the complex interplay among coagulation factors, blood platelets, and components of the fibrinolytic system. Blood platelet count, activated partial thromboplastin time, prothrombin time, plasma fibrinogen concentration, and D-dimer concentration were determined by routine methods. The authors conclude that thromboelastography results in individual patients can be used for the evaluation of bleeding risk. Further studies will be required to confirm the validity of their findings.¹⁶²

Methods to limit the need for blood replacement continue to evolve and include refinements in DHA techniques as well as in surgical management (i.e., patient selection, collaborative clinical efforts, and the efficiency of the operation and the postoperative care).¹⁰² Despite stringent donor screening criteria and the rigorous testing of every unit of blood, there remains a risk for the transmission of several pathogens.^{70,93,104,108,134,177} For viruses such as the human immunodeficiency virus (1 in 2,135,000), hepatitis B virus (1 in 205,000), and hepatitis C virus (1 in 2,000,000), this is due mainly to “window-period” donations.^34,247 The risks of newly emerging pathogens that can affect blood safety (e.g., Creutzfeldt-Jakob disease) remain unclear. There are other pathogens (e.g., cytomegalovirus, parvovirus B19) that are common in the general donor population and that may pose a risk in the immunosuppressed patient.²¹³ In addition, allogenic transfusion has been shown quantitatively to be an important contributor to postoperative infection.^94,260

The options of autogenous and donor-directed blood banking and their popularity for elective surgery are attributed to their perceived safety, to refinements in blood bank administration, and to public concern about the hazards of allogenic blood replacement.16,86,91,105,118,167,184,210,240 In at least one state (California) and one nation (Germany), the preoperative discussion of blood replacement options is mandated by law and must be documented in the medical record. Other alternatives to allogenic transfusion include acute normovolemic hemodilution, intraoperative blood salvage, and perioperative therapy with recombinant human erythropoietin (Procrit).^{35,101,136,170,173,180,230,231}

The absolute need for and actual use of blood transfusion in the practice of orthognathic surgery remains dependent on considerations that relate to total whole body oxygen delivery and its ability to meet the body’s metabolic needs.56,121,175,189 Many individual hospitals have instituted strict criteria for the transfusion of blood products.²¹⁵ Although mandated criteria may decrease the use of blood transfusions, it remains unclear if complications or delays in recovery have occurred as a result.²⁵⁰

Review of Study

Posnick and colleagues completed a retrospective study to review blood replacement practices in a consecutive series of a single surgeon’s experience with patients who all underwent, at a minimum, simultaneous Le Fort I maxillary osteotomy, bilateral sagittal split ramus osteotomies of the mandible, septoplasty, and inferior turbinate reduction procedures.²⁰² Many patients also underwent additional adjunctive procedures.

A chart review of a consecutive series of the surgeon’s patients (n = 34) who underwent elective bimaxillary orthognathic surgery (Le Fort I osteotomy and sagittal split osteotomies of the mandible) in combination with intranasal (septoplasty and inferior turbinate reduction) and often other simultaneous procedures during a 5-month time frame at a single institution was carried out (see Table 11-1). The chart review occurred at least 3 months after surgery for all patients.

Each patient was also evaluated for complications specific to the procedures that were carried out. Potential complications specific to the orthognathic procedures included infection that required the extended use of antibiotics or drainage procedures; dental injury; fibrous union; aseptic necrosis; bleeding that required secondary treatment; and oroantral, oronasal, and orocutaneous fistulas. Potential complications specific to the intranasal procedures included postoperative nasal bleeding that required packing or cauterization; the need for postoperative blood transfusion specific to nasal bleeding; the presence of septal perforation; and postoperative nasal obstruction that required additional procedures within 3 months after orthognathic surgery. Potential perioperative airway compromise was also reviewed, including the need for delayed extubation, reintubation, or tracheotomy. Potential complications specific to transfusions, including infections and autoimmune reactions, were also sought. The patient records that were reviewed included the office chart; the hospital records; and the data stored at the Red Cross (hospital) blood bank. Specific study data collected for each patient (n = 34) can be found in Table 11-1.

The study group included 15 male patients and 19 female patients. The mean age was 22 years and ranged from 13 to 65 years; the median age was 22 years. Thirteen of the 34 patients were less than 18 years old. All patients were treated with a combined orthodontic and surgical (orthognathic and intranasal) approach. The most frequent pattern of jaw deformity that was identified for the study group was asymmetric mandibular excess in 9 out of 34 patients (26%); this was followed by a cleft-craniofacial syndrome being found in 7 out of 34 patients (21%) and a long face growth pattern in 7 out of 34 patients (21%). Additional simultaneous facial procedures that were completed varied. Forty-four percent of the patients (15 out of 34) underwent the simultaneous removal of wisdom teeth. Twenty-one percent of the patients (7 out of 34) also underwent suction-assisted lipectomy of the neck. Eighty-eight percent of the patients (30 out of 34) underwent an osseous genioplasty. Eighteen percent of the patients (6 out of 34) underwent iliac (hip) bone grafting. Fifty-nine percent of the patients (20 out of 34) underwent maxillary (Le Fort I) segmentation. Six percent of the patient (2 out of 34) underwent otoplasty. For all patients, the intranasal procedures included both septoplasty (submucosal resection) and inferior turbinate reduction.

All patients were either extubated in the operating room or within the first hour after surgery while in the recovery room. No patients required overnight intubation, reintubation, or tracheotomy. With respect to complications, no patients required nasal packing or postdischarge blood transfusion. No patient required a return to the operating room for the control of bleeding or airway management.

Twenty-six of the 34 study patients (76%) elected to auto-donate (bank) blood in advance of their surgeries. Two of the 34 study patients auto-donated two units of blood, whereas 24 of the 34 auto-donated just one unit. Only one of the 26 patients that auto-donated received back her banked blood (1 out of 34 or 3% of study patients); she received just one unit of autogenous blood. One of the 34 study patients received a cross-matched anonymously donated (i.e. allogenic) unit (1 out of 34 or 3%). This patient did not elect to auto-donate blood in advance of surgery, and she received just the one unit of blood. Actual autogenous blood use within the group that banked blood was assessed to determine the proportion of discarded stored units. On the basis of the total units of blood that were pre-donated, 28 out of 29 (97%) of the stored units were not used and therefore discarded.

The records of each study patient (n = 34) were specifically reviewed for possible complications associated with the harvesting of autogenous blood and receiving a blood transfusion. Neither of the two patients who received packed red blood cells (one autogenous and the other homologous) experienced intraoperative or postoperative cardiovascular or respiratory compromise. There was no evidence of an adverse event such as an allergic reaction, a transfusion-related infection, hemolysis related to incompatible blood type, or an alteration of the immune system in either patient. According to a review of the blood bank records and discussions with the patients and their families, no complications were known to have occurred as a result of the blood-harvesting process.

Controversies in Blood Replacement for Orthognathic Surgery

Autogenous blood transfusion is the collection and then transfusion of a patient’s own blood. Allogenic blood is collected from someone other than the patient. During recent years, insights into the use of autogenous blood led to a complete revision of the National Heart, Lung and Blood Institute’s recommendations regarding the use of autogenous blood. Despite the reduction of the risk of transmitting viruses such as human immunodeficiency virus, hepatitis B virus, or hepatitis C virus, the transfusion of autogenous blood remains safer than that of allogenic blood, and it is considered appropriate for properly selected patients. However, there is still a risk of adverse reactions, bacterial contamination, and errors in the identification of the units. Directed donations (i.e., blood donations from a friend or family member) for a designated patient are not as safe as the patient’s own blood and must not be considered equivalent to an autogenous blood transfusion.

If transfusion is likely for a planned surgical procedure, there are several theoretical ways of obtaining autogenous blood, including 1) preoperative autogenous blood donation; 2) intraoperative blood salvage; and 3) acute normo-volemic hemodilution. In general, autogenous (intraoperative) blood collection techniques are considered undesirable for orthognathic surgery as a result of the associated saliva contamination. Acute normo-volemic hemodilution is the removal of blood and the simultaneous infusion of cell-free solutions to maintain intravascular volume before surgical blood loss. The removed blood is transfused during or after surgery, as needed, to maintain the desired hemoglobin levels. The use of this technique requires significant clinical expertise because of its associated physiologic consequences, and there is increased risk with DHA during orthognathic surgery.

The current recommendation of the National Heart, Lung and Blood Institute’s conference report is that autogenous blood donations are indicated for patients who are having surgical procedures for which blood is usually cross-matched.¹⁸⁵ The less likely the transfusion for a specific procedure, the more likely that donated blood will not be used. The recommendations are that patients should not be encouraged to donate blood for autogenous use during surgery unless there is a greater than 10% likelihood that they will need it. The historic literature indicates a wide range (i.e., 2.5% to 75%) with regard to the use of transfusion during bimaxillary orthognathic surgery. The review study performed by Posnick and colleagues indicated only a 6% need.²⁰² In current practice, the need for blood replacement during bimaxillary orthognathic surgery may be closer to 2%. The high-risk individual (e.g., an adult with obstructive sleep apnea and other comorbidities) can usually be recognized from the outset, and preparations can be made in advance (i.e., blood typing and cross-matching).

Unfortunately, it is not possible to give a quantitative answer to the question, “When should autogenous or allogenic blood be transfused?” Practical guidelines have been based on hemoglobin levels, but the inadequacy of this parameter is well known. In general, transfusions should be strongly considered when the patient’s hemoglobin level is at 7.0 g per liter (hematocrit = 21) or less. However, in the majority of cases, orthognathic surgery is carried out in young, healthy patients who are free of systemic disease. Thus, there is no absolute hemoglobin level that should automatically trigger a transfusion. A transfusion should be given only on the basis of sound clinical judgment.

Another common question is, “Should the indications for the use of autogenous blood transfusion differ from those for the use of allogenic blood transfusion?” If precise indications for a blood transfusion could be defined, autogenous blood would not be given more frequently than allogenic. Although the benefits of allogenic and autogenous blood transfusions are the same, the risks are not. Therefore, the risk-to-benefit ratio clearly supports the more liberal use of autogenous blood. It has been documented that patients who preoperatively donate blood are more likely to be transfused earlier and more frequently than patients who do not auto-donate. Studies have challenged the use of autologous blood donations for elective surgery, because there is the possibility of blood overcollection, the wasting of autologous units, and the costs of preparation and storage. Cohen developed an interesting mathematical model to analyze the use of preoperative autogenous blood donation.⁵³ The model clarifies how clinicians can customize autogenous blood collection for individual patients to minimize waste (i.e., the need to discard non-transfused blood).

A limited survey of hospitals in the United States determined that the fee generated by the blood bank for each unit of autologous blood that is harvested is estimated to be $255. This includes the storage and delivery of the blood to the operating room or for the disposal of the blood product (i.e., hazardous waste) if it is not used. This fee is typically paid in full by the patient’s medical insurance carrier. If the operative procedure for which the blood is donated is not covered by the patient’s medical insurance carrier, then the patient is expected to pay the fee.

A critical review of the literature and the evaluation of current clinical practice indicates that, with the effective use of DHA techniques, only a small percentage of individuals who are undergoing even complex orthognathic and intranasal surgery should require blood replacement. Close collaboration between the surgical and anesthesia teams and the recovery of patients in a safely monitored environment will continue to improve operating room and postoperative safety and to reduce blood loss and the need for transfusion in the orthognathic patient.

Head and Neck Examination

The head and neck examination of a patient who is scheduled to undergo endotracheal intubation should include his or her mouth-opening ability; the ability to protrude the lower jaw; any limitations of neck extension; the measurement of the thyromental distance; and the Mallampati test.140,164,165 These parameters cover the standard reference points to determine whether or not to expect a difficult airway. These parameters represent components of the basic head and neck airway evaluation recommended in the guidelines of the American Society of Anesthesiologists.⁶

All patients with dentofacial deformities should have documentation by the anesthesiologist of the airway examination, as stated previously. The preoperative evaluation maybe conducted in a clinic setting or immediately before surgery. It is also recommended that the evaluation document the following:

Prevention of Complications during Tracheal Intubation

According to the American Society of Anesthesiologists, four principles are central to the prevention of complications during tracheal intubation:

 Video 5

The presurgical airway evaluation by an experienced anesthesiologist provides a reasonable indication of potential intubation difficulty and should always be performed. The anesthesiologist must then make a judgment regarding whether anesthesia induction followed by direct laryngoscopy (as a first effort) followed by mask ventilation with percutaneous rescue (if direct laryngoscopy cannot be accomplished) is likely to be successful. The intrinsic limitations of the pre-anesthesia airway assessment mean that the preparation of an airway strategy for the management of unanticipated difficulties is the ultimate key to safe practice.

When the patient with a dentofacial deformity is felt to be at high risk for challenging airway management, advance planning ensures that necessary equipment and skilled personnel are available. The “difficult airway” is defined as the clinical situation in which a conventionally trained anesthesiologist experiences difficulty with face-mask ventilation of the upper airway, difficulty with tracheal intubation, or both. By definition, the difficult airway represents a combination of patient-specific factors, the specific clinical setting, and the skills of the individual practitioners.

Adequate face-mask ventilation may not be possible as a result of inadequate mask seal, excessive gas leak, or excessive resistance to the ingress or egress of gas. Difficulty with laryngoscopy is said to occur when it is not possible to visualize any portion of the vocal cords. Difficult tracheal intubation is defined as a tracheal intubation that has required multiple attempts in the presence or absence of true tracheal pathology. Failed intubation is defined as the inability to place an endotracheal tube after multiple intubation attempts.

The practical guidelines for the management of the difficult airway have been reported by the American Society of Anesthesiologists Task Force on Management of the Difficult Airway.⁶ The guidelines recommend the following: 1) a detailed evaluation of the airway; 2) a general physical examination; 3) additional patient-specific evaluations, as needed; 4) basic preparation for difficult airway management; 5) a strategy for the intubation of the difficult airway; 6) a strategy for the extubation of the difficult airway; and 7) arranging for follow-up care.

The anesthesiologist should have a preformulated strategy for the intubation of the patient with a dentofacial deformity and a difficult airway. This strategy should include the following: