SECTION XIV. Vascular Surgery
A Abdominal Aortic Aneurysm
1. Introduction
Surgical treatment of abdominal aortic aneurysm (AAA) may be required for atherosclerotic occlusive disease or aneurysmal dilation. These processes can involve the aorta and any of its major branches, leading to ischemia or rupture and exsanguination.
The primary event in aortic dissection is a tear in the intimal wall through which blood surges and creates a false lumen. The adventitia then separates up and/or down the aorta for various distances. Associated conditions include atherosclerosis and hypertension (which is present in 80% of these patients), Marfan’s syndrome, blunt chest trauma, pregnancy, and iatrogenic surgical injury (e.g., resulting from aortic cannulation during cardiopulmonary bypass).
Aortic dissections involving the ascending aorta are considered type A. Surgical repair is through a median sternotomy using profound hypothermia and total circulatory arrest or cardiopulmonary bypass with moderate hypothermia. Aortic dissections involving the descending aorta (i.e., beyond the origin of the left subclavian artery) are considered type B. Aneurysms can also be classified as saccular, fusiform, or dissecting. Surgical repair involves proximal and distal clamping of the aorta, opening of the aneurysm, evacuation of the thrombus, and placement of a graft. A midline transabdominal surgical approach or retroperitoneal left thoracoabdominal approach may be used.
2. Incidence
The incidence of AAAs has increased over the last 5 decades from 12.2 to 36.2 per 100,000 surgical procedures. This increase may partially be the result of the detection of asymptomatic aneurysms by noninvasive diagnostic modalities, such as computed tomography (CT), magnetic resonance imaging (MRI), and ultrasonography. The occurrence of AAAs has increased because of the increased age of the general population and the vascular changes that occur as a result of aging. Aortic aneurysms can be identified in approximately 1% to 4% of the population older than 50 years and in approximately 5% of the population older than 60 years. Aneurysms are more common in men than in women and in Caucasians than in African Americans.
The present mortality rate ranges from 1% to 11% (although most commonly estimated at 5%), as compared with the mortality rates in the 1950s of 18% to 30%. Advanced detection capabilities, earlier surgical intervention, extensive preoperative preparation, refined surgical techniques, better hemodynamic monitoring, improved anesthetic techniques, and aggressive postoperative management have all contributed to this improvement in surgical outcomes. Surgical intervention is recommended for AAAs ≥5.5 cm in diameter. Estimates of mortality resulting from ruptured AAAs vary from 35% to 94%. The 5-year mortality rate for individuals with untreated AAAs is 81%, and the 10-year mortality rate is 100% Early detection and elective surgical intervention are advisable because rupture leads to an increased incidence of mortality.
3. Diagnosis
a) Frequently, asymptomatic aneurysms are detected incidentally during routine examination or abdominal radiography. Smaller aneurysms are often undetected on routine physical examination.
b) Diagnostic techniques, such as ultrasonography, CT scan, and MRI, may identify vascular abnormalities in these patients. Such noninvasive techniques not only reveal the presence of aneurysms but also provide information about aneurysm size, vessel wall integrity, and adjacent anatomic definition.
c) Invasive techniques, including contrast-enhanced CT scan, contrast angiography, and digital subtraction angiography, can provide additional information and more detailed representations of arterial anatomy. Digital subtraction angiography is the best method of evaluating suprarenal aneurysms because this method provides superior definition of the aneurysmal relationship to the renal arteries.
ABDOMINAL AORTIC RECONSTRUCTION
1. Patient selection
a) Most patients with abdominal aneurysms, including octogenarians, are considered surgical candidates. Although advancing age contributes to an increased incidence of morbidity and mortality, age alone is not a contraindication to elective aneurysmectomies.
b) Physiologic age is more indicative than chronologic age of increased surgical risk.
c) Contraindications to elective repair include intractable angina pectoris, recent myocardial infarction, severe pulmonary dysfunction, and chronic renal insufficiency.
d) Patients with stable CAD with coronary artery stenosis of >70% requiring nonemergent AAA repair do not benefit from revascularization if beta blockade has been established.
2. Patient preparation
a) Preoperative fluid loading and restoration of intravascular volume are perhaps the most important techniques used to enhance cardiac function during abdominal aortic aneurysmectomies.
b) Reliable venous access should be secured if volume replacement is to be accomplished. Large-bore intravenous lines and central lines can be used to infuse fluids or blood.
c) Massive hemorrhage is an ever-present threat; therefore the availability of blood and blood products should be ensured. Provisions for rapid transfusion and intraoperative blood salvage should be confirmed.
3. Monitoring
a) Standard monitoring methods include electrocardiography with display of lead II for detection of dysrhythmias and the precordial V 5 lead for analysis of ischemic ST segment changes; pulse oximetry; and capnography.
b) An esophageal stethoscope allows for continuous auscultation of heart and breath sounds as well as temperature determination.
c) Placement of an indwelling urinary catheter is necessary for the continuous measurement of urinary output and renal function. Neuromuscular function is also routinely monitored.
d) Invasive blood pressure monitoring permits beat-to-beat analysis of the blood pressure, immediate identification of hemodynamic alterations related to aortic clamping, and access for blood sampling.
e) Pulmonary artery catheters can be used in abdominal aortic reconstruction for monitoring left-sided filling pressures as a guide for fluid replacement.
f) Pulmonary artery catheterization not only provides clinical indexes that reflect intravascular volume, but also facilitates calculations of stroke volume, cardiac index, and left ventricular stroke work index.
g) Myocardial ischemia can be detected by analysis of pulmonary artery catheter tracings. Some pulmonary artery catheters allow for measurement of mixed venous oxygen saturation.
h) By detecting changes in ventricular wall motion, two-dimensional transesophageal echocardiography provides a sensitive method for assessing regional myocardial perfusion. Wall motion abnormalities also occur much sooner than electrocardiographic changes during periods of reduced coronary blood flow.
i) Myocardial ischemia poses the greatest risk of mortality after abdominal aortic reconstruction. Intraoperative monitoring may enable earlier detection and intervention during ischemic cardiac events.
4. Application of aortic cross-clamp: Hemodynamic alterations
a) The hemodynamic effects of aortic cross-clamping depend on the application site along the aorta, the patient’s preoperative cardiac reserve, and the patient’s intravascular volume.
b) The most common site for cross-clamping is infrarenal because most aneurysms appear below the level of the renal arteries. Less common sites of aneurysm development are the juxtarenal and suprarenal areas.
c) When aortic cross-clamping is used, hypertension occurs above the cross-clamp and hypotension occurs below the cross-clamp. Organs proximal to the aortic occlusion may experience a redistribution of blood volume.
d) There is an absence of blood flow distal to the clamp in the pelvis and lower extremities.
e) Increases in afterload cause myocardial wall tension to increase. Mean arterial pressure (MAP) and systemic vascular resistance (SVR) also increase.
f) Cardiac output may decrease or remain unchanged. Pulmonary artery occlusion pressure (PAOP) may increase or display no change.
g) The percentages of change in cardiovascular indexes at different levels of aortic occlusion are listed in the following table.
h) Patients with ischemic heart disease or ventricular dysfunction are unable to fully compensate as a result of the hemodynamic alterations. The increased wall stress attributed to aortic cross-clamp application may contribute to decreased global ventricular function and myocardial ischemia. Clinically, these patients experience increases in PAOP in response to aortic cross-clamping. Aggressive pharmacologic intervention is required for restoration of cardiac function during this time.
5. Metabolic alterations
a) After the application of an aortic cross-clamp, the lack of blood flow to distal structures makes these tissues prone to developing hypoxia. In response to hypoxia, metabolites (e.g., lactate) accumulate.
b) The release of arachidonic acid derivatives may also contribute to the cardiac instability that is observed during aortic cross-clamping. Thromboxane A 2 synthesis, which is accelerated by the application of an aortic cross-clamp, may be responsible for the decrease in myocardial contractility and cardiac output that occurs.
c) Traction on the mesentery is a surgical maneuver used for exposing the aorta. Decreases in blood pressure and SVR, tachycardia, increased cardiac output, and facial flushing are common responses to mesenteric traction.
d) The neuroendocrine response to major surgical stress is believed to be mediated by cytokines such as interleukin 1-beta (IL-1β), interleukin-6 (IL-6), and tumor necrosis factor alpha (TNF-α), as well as plasma catecholamines and cortisol. These mediators are thought to be responsible for triggering the inflammatory response that results in increased body temperature, leukocytosis, tachycardia, tachypnea, and fluid sequestration.
6. Effects on regional circulation
a) Structures distal to the aortic clamp are underperfused during aortic cross-clamping. Renal insufficiency and renal failure have been reported to occur after abdominal aortic reconstruction.
b) Suprarenal and juxtarenal cross-clamping may be associated with a higher incidence of altered renal dynamics; however, reductions in renal blood flow can occur with any level of clamp application.
c) Infrarenal aortic cross-clamping is associated with a 38% decrease in renal blood flow and a 75% increase in renal vascular resistance. These effects may lead to acute renal failure, which is fatal in 50% to 90% of patients who have undergone aneurysmectomies.
d) Preoperative evaluation of renal function is one of the most significant predictors of postoperative renal dysfunction. Therefore, a complete evaluation of renal function is required in the preoperative period.
e) Spinal cord damage is associated with aortic occlusion. Interruption of blood flow to the greater radicular artery (artery of Adamkiewicz) in the absence of collateral blood flow has been identified as a causative factor in paraplegia.
f) The incidence of neurologic complications increases as the aortic cross-clamp is positioned in a higher or more proximal area.
g) Ischemic colon injury is a well-documented complication that is associated with abdominal aortic resections. Ischemia of the colon is most frequently attributed to manipulation of the inferior mesenteric artery, which supplies the primary blood supply to the left colon. This vessel is often sacrificed during surgery, and blood flow to the descending and sigmoid colon depends on the presence and the adequacy of the collateral vessels. Mucosal ischemia occurs in 10% of patients who undergo abdominal aortic aneurysm repair. In less than 1% of these patients, infarction of the left colon necessitates surgical intervention.
7. Aortic cross-clamp release
a) While the aorta is occluded, metabolites that are liberated as a result of anaerobic metabolism, such as serum lactate, accumulate below the aortic cross-clamp and induce vasodilation and vasomotor paralysis.
b) As the cross-clamp is released, SVR decreases, and blood is sequestered into previously dilated veins, which decreases venous return.
c) Reactive hyperemia causes transient vasodilation secondary to the presence of tissue hypoxia, the release of adenine nucleotides, and the liberation of an unnamed vasodepressor substance that acts as a myocardial depressant and a peripheral vasodilator.
d) This combination of events results in decreased preload and afterload. The hemodynamic instability that may ensue after the release of an aortic cross-clamp is called declamping shock syndrome.
e) Evidence demonstrates that venous endothelin (ET)-1 may be partially responsible for the hemodynamic alterations that accompany declamping shock syndrome. Venous ET-1 has a positive inotropic effect on the heart as well as a vasoconstricting and vasodilating action on blood vessels.
f) The most frequently observed hemodynamic responses to aortic declamping are listed in the table on p. 574.
g) The magnitude of the response to unclamping the aorta may be manipulated. Although SVR and MAP decrease, intravascular volume may influence the direction and the magnitude of change in cardiac output.
h) Restoration of circulating blood volume is paramount in the provision of circulatory stability before release of the aortic clamp.
i) The site and the duration of cross-clamp application, as well as the gradual release of the clamp, influence the magnitude of circulatory instability. Partial release of the aortic cross clamp over time frequently results in less severe hypotension.
8. Surgical approach
a) The standard approach for elective abdominal aortic reconstruction is the transperitoneal incision. The advantages of this route include exposure of infrarenal and iliac vessels, ability to inspect intraabdominal organs, and rapid closure. Unfavorable consequences associated with this approach include increased fluid losses, prolonged ileus, postoperative incisional pain, and pulmonary complications.
b) The retroperitoneal approach has gained popularity as an alternative to the standard route. Its advantages include excellent exposure (especially for juxtarenal and suprarenal aneurysms), decreased fluid losses, less incisional pain, and fewer postoperative pulmonary and intestinal complications. After implantation with a synthetic graft, the aortic adventitia is closed. In addition, the retroperitoneal approach does not elicit mesenteric traction syndrome. The reported limitations of this approach are unfamiliarity of surgeons with this technique, poor right distal renal artery exposure, and inability to inspect the integrity of the abdominal contents.
9. Management of fluid and blood loss
a) Extreme loss of extracellular fluid and blood should be expected with abdominal aortic aneurysmectomies. Evaporative losses and third spacing occur, with the magnitude of loss depending on the surgical approach, the duration of the surgery, and the experience of the surgeon.
b) Most blood loss occurs because of back bleeding from the lumbar and inferior mesenteric arteries after the vessels have been clamped and the aneurysm is opened.
c) The use of heparin also contributes to blood loss. Excessive bleeding, however, can occur at any point during surgery, and blood replacement is commonly administered during abdominal aortic resections.
d) Due to the heightened awareness of transfusion-related morbidity, the use of autologous blood has generated increasing interest. Presently, three options are available for the use of autologous transfusions: preoperative deposit, intraoperative phlebotomy and hemodilution, and intraoperative blood salvage.
10. Preoperative management
a) The presence of underlying coronary artery disease (CAD) in patients with vascular disease has been well documented. CAD is reported to occur in more than 50% of patients who require abdominal aortic reconstruction and is the single most significant risk factor influencing long-term survivability. Myocardial infarctions are responsible for 40% to 70% of all fatalities that occur after aneurysm reconstruction. In the presence of such threatening mortality rates, the extent of CAD and the subsequent functional limitations should be clearly defined and cardiac function optimized preoperatively before elective aortic vascular reconstruction is performed.
b) Advanced age, cardiac history, aberrations on physical examination, electrocardiographic abnormalities, and previous surgical procedures are identifiable factors in the cardiac risk index that contribute to cardiac complications.
c) Patients with unremarkable medical histories and normal physical examinations, exercise testing, electrocardiography, and laboratory studies have a decreased surgical risk. Currently, investigators advocate the use of coronary angiography in selected patients who have positive findings on the initial cardiac evaluation.
d) Patients with symptomatic CAD require more extensive cardiac evaluation. Dipyridamole thallium testing is perhaps one of the most reliable methods for evaluating the extent of myocardial dysfunction associated with CAD and for predicting coronary events after vascular surgery.
e) Techniques capable of evaluating left ventricular performance, such as echocardiography, are of some value in the prediction of adverse cardiac events. Ambulatory electrocardiographic monitoring has also been very successful in the identification of postoperative cardiac complications. Coronary angiography provides the most reliable definition of coronary anatomy and the extent of CAD.
f) The endpoint of any method of preoperative cardiac evaluation for aneurysmectomy is identification of functional cardiac limitations. Depending on the degree of cardiac dysfunction, preoperative optimization of cardiac function may range from simple pharmacologic manipulation to surgical intervention.
g) Hypertension, chronic obstructive pulmonary disease, diabetes mellitus, renal impairment, and carotid artery disease are frequently observed in patients with abdominal aortic aneurysms.
h) Measures should be taken to optimize organ function, because each of these disease states contributes to postoperative complications. Preoperative renal dysfunction deserves special consideration because aortic cross-clamping produces alterations in renal dynamics. The degree of preoperative renal insufficiency contributes to the extent of any postoperative renal damage.
11. Intraoperative management
a) Anesthetic selection
(1) The anesthetic selection should be based on the following objectives: provision of analgesia and amnesia, facilitation of relaxation, maintenance of hemodynamic stability, preservation of renal blood flow, and minimization of morbidity and mortality.
(2) Inhalation agents
(a) All inhalation anesthetics may depress the myocardium and cause hemodynamic instability. Therefore, high concentrations of inhalation agents in patients with moderate to severe decreased ejection fraction should not be used.
(b) Potential organ toxicity and lack of postoperative analgesia may be additional limitations to the use of these agents.
(c) Beneficial effects attributed to the use of inhalation agents include the ability to alter autonomic responses, reversibility, rapid emergence, and potentially earlier extubation.
(3) Narcotic technique
(a) A balanced technique using a combination of high-dose narcotics with nitrous oxide can be used as the anesthetic for major vascular surgery.
(b) The cardiovascular stability provided by opioids has been well documented, and this feature is especially attractive for patients with ischemic heart disease and ventricular dysfunction.
(c) Provision of intense analgesia for the initial postoperative period after major abdominal vascular surgery, via the administration of a neuraxial opioid, does not alter the combined incidence of major cardiovascular, respiratory, and renal complications.
(4) Regional anesthesia
(a) The use of epidural anesthesia for abdominal aneurysmectomies has gained renewed interest. Several benefits of epidural use include decreased preload and afterload, preserved myocardial oxygenation, reduced stress response, excellent muscle relaxation, decreased incidence of postoperative thromboembolism, and increased graft flow to the lower extremities.
(b) Hypotension may also be a significant unfavorable result of an epidural technique. In fact, this technique requires the administration of approximately 1600 to 2000 mL more intravenous fluid than is usual with general anesthetic.
(c) The controversy regarding hematoma formation after heparinization during epidural techniques is still noteworthy. Studies have shown that the simultaneous use of epidural anesthesia and low-dose heparinization rarely produces complications.
(d) Postoperative pain control is vital in order to maintain hemodynamic stability and to alleviate patient suffering. Epidural narcotics have been shown to decrease pain after major surgery.
(e) Because of the high incidence of CAD in patients presenting for abdominal aortic reconstruction, severe postoperative pain can result in increased heart rate and blood pressure, which may contribute to cardiac-related morbidity and mortality. Pain relief may decrease respiratory splinting and decrease the likelihood of hypoxemia.
(5) Combination techniques
(a) Combining anesthetic techniques for major vascular surgery is more popular than using them alone because the advantages of each technique contribute to a smoother anesthetic.
(b) A balanced technique supplemented by low-dose inhalation agents maintains cardiovascular hemodynamics and controls momentary autonomic responses to surgical stimulation.
(c) Another choice is to use epidural anesthesia combined with light general anesthesia. This provides the benefits of epidural anesthesia and the ability to provide amnesia and controlled ventilation.
b) Fluid management
(1) The maintenance of intravascular volume may be an extreme challenge during abdominal aortic resections. Controversy exists regarding whether the administration of crystalloids or colloids affects the overall incidence of morbidity and mortality.
(2) Crystalloids may be used for replacing basal and third-space losses at an approximate rate of 10 mL/kg/hr.
(3) Blood losses initially can be replaced with crystalloids at a ratio of 3:1. The combination of crystalloid and colloid administration is also acceptable.
(4) Regardless of the choice of fluid, volume replacement should be dictated by physiologic parameters. Fluid replacement should be sufficient for the maintenance of normal cardiac filling pressures, cardiac output, and urine output of 1 mL/kg/hr.
(5) Patients with limited cardiac reserve can develop congestive heart failure if hypervolemia occurs.
c) Hemodynamic alterations
(1) Hemodynamic changes are likely to occur throughout the anesthesia process.
(2) Momentary fluctuations in heart rate and blood pressure should be anticipated during induction and intubation.
(3) Preoperative replacement of fluid deficits prevents exaggerated responses to vasodilating induction agents.
(4) For patients with adequate left ventricular function, hemodynamic stability can be preserved with a “slow” induction using opioids and β-adrenergic blocking agents.
(5) Etomidate has minimal myocardial depressant effects and may be most suitable for patients with limited cardiac reserve.
(6) The response to mesenteric traction is also associated with momentary hemodynamic changes.
(7) Application of the aortic cross-clamp produces various hemodynamic responses. Patients without underlying ischemic heart disease usually demonstrate slight changes in PAOP when the aorta is occluded, requiring minimal intervention. However, patients with a history of CAD may experience an increase in PAOP and a decrease in cardiac output, indicating left ventricular decompensation.
(8) Although several different pharmacologic agents may be used, nitroglycerin appears to be the drug of choice because of its primary pharmacologic effect of decreasing preload and thereby decreasing myocardial oxygen demand.
(9) Inotropic agents, such as dopamine and dobutamine, may improve cardiac output, whereas pharmacologic agents that decrease afterload, such as sodium nitroprusside and isoflurane, may decrease SVR.
(10) The more proximal the application of the aortic cross-clamp, the greater the magnitude and the severity of these responses. Vasoactive medications should be readily available throughout the surgery.
(11) When the aortic cross-clamp is released, declamping shock syndrome may occur. Severe hypotension and reduction in cardiac output may ensue. These conditions can be prevented by volume loading and raising of the central venous pressure 3 to 5 mm Hg or raising the PAOP 3 to 4 mm Hg just before the clamp is released.
(12) If severe acidosis is present, sodium bicarbonate may be administered. Temporarily increasing minute ventilation may also be useful for the control of acidosis.
d) Renal preservation
(1) The incidence of acute renal failure after infrarenal cross-clamping is 5%, and this value increases to 13% after suprarenal cross-clamping.
(2) Mortality is four to five times greater in patients who develop acute renal failure postoperatively.
(3) Alterations in renal dynamics during intrarenal cross-clamping may continue up to 1 hour after the clamp is released. Such alterations can be profound and can extend into the postoperative period.
(4) Mechanisms for the preservation of renal function during aortic cross-clamping include improving renal and glomerular blood flow.
(5) Maintenance of cardiac output and intravascular volume is vital. Prevention of hypovolemia is the best prophylaxis against renal failure.
(6) Administration of mannitol 20 to 30 minutes before aortic clamping may help preserve renal function due to hydroxyl free-radical scavenging properties.
(7) Further intervention includes intravenous administration of low-dose dopamine at 3 to 5 mcg/kg/min, fenoldopam, and use of loop diuretics. Renal dose dopamine has not been proven to decrease the risk of postoperative renal dysfunction.
12. Postoperative considerations
a) Cardiac, respiratory, and renal failure are the most common complications observed postoperatively in patients recovering from abdominal aortic reconstruction.
b) Cardiovascular function should be closely monitored in the intensive care unit (ICU) for at least 24 hours after surgery. Maintenance of adequate blood pressure, intravascular fluid volume, and myocardial oxygenation is paramount during this period.
c) Myocardial infarction frequently contributes to postoperative morbidity and mortality. Serial cardiac enzyme analysis may be monitored.
d) Pharmacologic agents used in the treatment of hypertension should also be available.
e) Most patients require ventilatory assistance during the postoperative period. Vigilant monitoring of respiratory function is mandatory, especially when epidural catheters are used for postoperative analgesia.
f) Renal function should be continuously evaluated in the postoperative phase. Urine output should be maintained at 1 mL/kg/hr. Administration of fluid, maintenance of physiologic hemodynamics, and concurrent administration of pharmacologic agents should be considered to improve urine output.
JUXTARENAL AND SUPRARENAL AORTIC ANEURYSMS
1. Introduction
a) Although most abdominal aortic aneurysms occur below the level of the renal arteries, 2% extend proximally and involve the renal or visceral arteries.
b) Juxtarenal aneurysms are located at the level of the renal arteries, but they spare the renal artery orifice. More proximal suprarenal aneurysms include at least one of the renal arteries and may involve visceral vessels.
c) The effects of aortic cross-clamping for juxtarenal or suprarenal aneurysms are similar to those for infrarenal aortic occlusions; however, the magnitude of hemodynamic alterations increases as the aorta is clamped more proximally.
2. Anesthetic considerations
a) Preoperative preparation includes a thorough evaluation of coexisting disease, with an emphasis on cardiac function.
b) As the aorta is clamped more proximally, left ventricular afterload increases, and, consequently, myocardial ischemia is more likely to occur.
c) Diligent cardiac monitoring is necessary, and direct intraarterial blood pressure assessment, cardiac filling pressure monitoring, and transesophageal echocardiography are advocated in order to detect cardiac dysfunction and allow for immediate pharmacologic intervention.
d) Renal failure, although possible during infrarenal aortic cross-clamping, occurs more frequently as a result of suprarenal aortic occlusion. Maintaining adequate intravascular volume and administering osmotic and loop diuretics may minimize renal ischemia and dysfunction.
e) If the ischemic episode persists for longer than 45 minutes, renal cooling is suggested. Renal cooling consists of flushing the kidney with an iced electrolyte perfusate that contains heparin and glucose.
f) Paraplegia is possible when the blood supply to the spinal cord is interrupted by aortic cross-clamping at or above the level of the diaphragm.
g) Increasing the MAP or decreasing the cerebrospinal fluid (CSF) pressure may be used as a means to increase spinal cord perfusion pressure.
RUPTURED ABDOMINAL AORTIC ANEURYSM
1. Introduction
a) A high mortality rate of up to 94% is associated with a ruptured abdominal aortic aneurysm.
b) The most common symptoms of ruptured abdominal aortic aneurysms are abdominal discomfort with a pulsatile mass, back pain, decreased peripheral pulses, and hypotension.
c) Hypotension and a history of cardiac disease are two factors associated with the poorest prognosis.
d) Patients with these symptoms should be immediately transferred to the operating room for surgical exploration. When hypotension is absent, more time is available for a comprehensive CT scan to search for other causes of abdominal discomfort.
e) Once the patient arrives in the operative suite, a brief preoperative evaluation, establishing of venous access, and provisions for fluid and blood product administration can be completed.
f) Induction of anesthesia should follow the principles of trauma anesthesia. Hemodynamic stability should be the primary objective, and anesthetic induction and maintenance agents should be selected on a case-by-case basis.
g) Cardiovascular resuscitation is the anesthesia provider’s primary focus until blood loss from the proximal aorta is controlled by surgical intervention. Fluid resuscitation can begin with crystalloids, and blood products can be administered as they become available. Intraoperative blood salvage provisions should be secured.
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