Elective Abdominal Aortic Reconstruction Research Articles

Extended intensive care correlates with worsening of surgical outcome after elective abdominal aortic reconstruction

The aim of this study was to evaluate the impact of extended postoperative intensive care on short- and long-term patient outcome after elective abdominal aortic surgery and to assess the risk factors for patient survival after extended intensive care unit (ICU) treatment. The data of 231 patients that underwent open or endovascular abdominal aortic surgery were retrospectively analysed with regard to extended postoperative intensive care, defined as ICU treatment for more than 24 consecutive hours. Pre- and intraoperative factors were evaluated. The endpoints of the study were postoperative complications, mortality, and long-term follow-up. Univariate and multivariate Cox proportional regression analyses were performed to identify risk factors of worse overall survival. Extended postoperative intensive care was needed in 84 patients (63 after open and 21 after endovascular surgery). The period of ICU treatment was similar in both groups. Only the wound complications (31.8% vs. 9.5%, P=0.0498; OR 4.42 [0.94-20.84]) and the rate of acute kidney injury (82.5% vs. 57.1%, P=0.0352; OR 3.55 [1.20-0.46]) were more frequent after open surgery, whereas brief reactive psychosis (38.1% vs. 14.3%, P=0.0281; OR 0.27 [0.09-0.84]) was more frequent after endovascular surgery. ICU stay of ≥8 days correlated with significantly lower survival rates compared to a shorter ICU stay (P=0.0034), independent of open or endovascular techniques. Other multivariate risk factors for worse survival were the absence of preoperative aspirin medication, a Body Mass Index (BMI) of <25, chronic renal insufficiency, and coronary artery disease. Endovascular therapy was a positive predictive factor of short ICU stay of ≤3 days. The outcome after extended intensive care following elective aortic surgery is strongly dependent on the length of ICU stay.

Investigation of Systemic and Mesenteric Inflammatory Signaling and Gut-Derived Endothelial Toxicity in Patients Undergoing High-Risk Abdominal Aortic Surgery

Evidence from animal models of trauma and hemorrhage has suggested that the gut plays an active role in the pathogenesis of systemic inflammatory responses and multiple organ dysfunction syndrome. The aim of the present study was to seek evidence for gut-derived signals in man in a group of eight patients undergoing elective abdominal aortic reconstruction, a procedure that is associated with sterile tissue injury, controlled colonic ischemia as a consequence of aortic cross-clamping, and a significant risk of developing systemic inflammation and multiple organ dysfunction syndrome. Despite the presence of a marked systemic inflammatory response (IL-6, IL-18, monocyte chemoattractant protein 1, and IL-8) and a gut-derived inflammatory signal (IL-6), we could find no evidence that gut-derived pathogen DNA was present in the central or mesenteric circulation, and we could find no evidence that either central or mesenteric plasma samples could induce apoptotic or necrotic cell death in human umbilical vein endothelial cells in vitro. Similarly, we could find no evidence of adhesion molecule upregulation in the endothelial monolayers exposed to central or mesenteric plasma sampled at any time point during surgery. There was, however, evidence of an increase in the expression of RAGE (receptor for advanced glycation end products) by endothelial cells following exposure to mesenteric venous, but not central, plasma sampled during maximum ischemia. In conclusion, during sterile tissue injury and controlled colonic ischemia-reperfusion in man, there is a marked systemic proinflammatory response, which is in part gut derived, in the absence of evidence for the presence of toxic endothelial factors or gut-derived microorganisms in the central or mesenteric circulations.

Autotransfusion in aortic surgery: the Haemocell System 350 cell saver.

Autotransfusion was performed during elective abdominal aortic reconstruction in ten patients using the recently developed Haemocell System 350. A mean of 60 per cent of total blood loss was salvaged, and during operation each patient was autotransfused 1 unit. Good preservation of cellular components, including platelets, was seen after processing with the device, which uses a vortex mixing filter for cell separation. There was no evidence of coagulopathy; mean free plasma haemoglobin levels were slightly raised (17 mg/dl) and plasma heparin concentration was negligible (0.10 units/ml) 4 h after surgery. A transient drop in plasma fibrinogen levels and the appearance of fibrin degradation products in low concentrations (mean 1.5 mg/l) were seen. Oxyhaemoglobin dissociation curves showed the salvaged red blood cells to have a normal affinity for oxygen. Renal and hepatic function remained unaltered and there were no complications attributable to autotransfusion. The device was easy to handle and a trained operator was not required.

Myocardial infarction after reconstruction of the abdominal aorta.

The records of 555 patients who underwent elective abdominal aortic reconstruction were analysed to identify risk factors predisposing to cardiac complications. Perioperative myocardial infarction occurred in 35 patients (6.3 per cent), of whom 12 (2.2 per cent) died. Using multiple logistic regression, four preoperative factors that were independently predictive for postoperative myocardial infarction were identified with the following relative risk ratios: history of transient ischaemic attacks, 5.08; raised serum creatinine level, 3.66; age > 60 years, 3.00; and angina requiring regular treatment, 2.74. A scoring system using these four factors was devised that identified 150 of the 555 patients as at high risk, and included 69 per cent of those with myocardial infarction after operation and 83 per cent of those who died. A clinical risk score is a practical first step in identifying patients at risk of myocardial infarction; it would also reduce the number of patients for whom sophisticated tests of cardiac function were necessary.

Preoperative cardiology consultation.

In a 1998 survey of New York metropolitan area anesthesiologists, surgeons, and cardiologists, the three specialties were in general agreement that important purposes of a cardiology consultation are to treat an inadequately treated cardiac condition before surgery (e.g., unstable angina or congestive heart failure [CHF]), to provide data to use in anesthesia management (e.g., ischemic threshold of tachycardia on stress test or left ventricular ejection fraction), and possibly to diagnose a medical condition before surgery (e.g., the cause of a new-onset atrial fibrillation). The yield of a cardiology consultation, in terms of new therapy or significant effect on patient management strategy prior to surgery, has, however, been reported to vary widely from 10% to more than 70%. The reasons why the consultation process often falls short of ideal are probably multifold, but may often originate from vague understanding of the consultation process. The physician initiating the consultation, whether an anesthesiologist or a surgeon, may not make it clear to the cardiologist why the consultation is being sought. In a retrospective review of 202 cardiology consultations at a university hospital, it was found that 108 just asked for an “evaluation,” 79 asked for a “clearance,” and 9 did not specifically request anything. Only six posed a specific question. As a result, the consultant often makes broadly inclusive, general remarks about perioperative management of the patient and may recommend preoperative diagnostic work-up that does not influence the patient’s outcome but prolongs the hospital stay. In this review are presented (1) the indications for cardiology consultations as implied in the American College of Cardiology–American Heart Association (ACC–AHA) guidelines on preoperative cardiac evaluation, and (2) suggestions on how the ACC–AHA guidelines may be critically applied to, and improve, the consultation process. Preoperative Cardiac Consultation Based on the ACC–AHA Guidelines The ACC–AHA guidelines on preoperative cardiac evaluation were published initially in 1996 and were also endorsed by the Society of Cardiovascular Anesthesiologists and the Society for Vascular Surgery. An updated version of the guidelines was published in 2002. The guidelines were based on the then-available literature as well as expert opinions from the disciplines of anesthesiology, cardiology, electrophysiology, vascular medicine, vascular surgery, and noninvasive cardiac testing. The guidelines provided an 8-step algorithm for stratifying the patient’s risks and triaging to either surgery or cardiac evaluation. The first three steps of the guidelines consider the urgency of the operation and the recency of cardiac evaluation and intervention. If the operation is not emergent and if there has not been recent cardiac evaluation and/or intervention with no significant interim changes, then the remainder of the guidelines are applied. Steps 4 through 7 deal with an assessment of the patient’s clinical predictors of cardiac risk, functional status, and the risk of the surgery proposed. Step 8, or noninvasive cardiac testing to further define the patient’s risk, is indicated (1) if the patient has a major clinical predictor, (2) if the patient has an intermediate clinical predictor and either has poor functional status or is undergoing a high-risk surgery, or (3) if the patient has poor functional status and is undergoing a high-risk surgery. As defined by the ACC–AHA, major clinical predictors are unstable coronary syndrome, decompensated congestive heart failure (CHF), significant arrhythmias, and severe valvular disease. Intermediate clinical predictors are mild angina pectoris, history of myocardial infarction (MI) or CHF, diabetes mellitus, and chronic renal failure with serum creatinine greater than 2 mg/dl. A high-risk surgery carries a greater than 5% perioperative risk of cardiac events such as MI, CHF, or death and is exemplified by emergent major operations, especially in the elderly, aortic, and other major vascular procedures, peripheral vascular bypass procedures, and anticipated prolonged surgical procedures associated with large fluid shifts and/or blood loss. An intermediate-risk surgery carries 1–5% perioperative risk of cardiac events and is exemplified by carotid endarterectomy, intraperitoneal and Director of Vascular Anesthesia, Department of Anesthesia & Critical Care, Beth Israel Deaconess Medical Center, and Associate Professor of Anaesthesia, Harvard Medical School.

Prediction of cardiac risk before abdominal aortic reconstruction: Comparison of a revised Goldman Cardiac Risk Index and radioisotope ejection fraction

Background: A revised Goldman Cardiac Risk Index has been suggested to identify patients at higher risk for cardiac complications in patients who undergo major noncardiac surgery. The aim of this study was to test the usefulness of this model in an independent series of patients who underwent abdominal aortic surgery and to compare the index with the multiple gated acquisition (MUGA) scan in the prediction of cardiac complications. Methods: We studied 77 patients who underwent MUGA scan before elective abdominal aortic reconstruction. The revised index was calculated for each patient after recording the following five risk factors: history of ischemic heart disease, congestive heart failure, cerebrovascular disease, insulin-dependent diabetes, and creatinine level more than 2 mg/dL. Technetium-99m MUGA scan provided information about the resting left ventricular ejection fraction (LVEF) and the presence of regional wall motion abnormalities. Results: Fourteen patients (18%) had cardiac complications develop. The index proved to be a satisfactory predictor of postoperative cardiac events (P =.008), and an abnormal LVEF failed to do so (P =.1). The presence of wall abnormalities, with or without an abnormal LVEF, predicted cardiac complications (P =.004 and P =.006). Patients with a higher index score showed a tendency to have a lower LVEF (Spearman rank correlation, r = −0.43; P <.001). Wall abnormalities, with or without an abnormal LVEF, were more frequent in patients with higher scores (P =.03 and P =.009). Combining the index with the LVEF or the wall abnormalities or both could further stratify the cardiac risk (P =.004, P =.0003 and P =.0006, with χ2 test for trend). Conclusion: For those patients who undergo elective abdominal aortic surgery, the revised Goldman Cardiac Risk Index is a simple method of evaluating cardiac risk with minimum resource implications. MUGA scan can offer additional stratification in patients judged with the index to be at high risk. (J Vasc Surg 2002;35:943-9.)

Simultaneous Gastrointestinal Surgery in Patients With Elective Abdominal Aortic Reconstruction—Invited Critique

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P6. Impact of radionuclide ventriculography prior to elective abdominal aortic reconstruction

s: Abstracts of the Twenty-Eighth Annual Meeting of The British Nuclear Medicine Society Brighton Conference Centre, 10-12 April 2000: POSTERS

A new method of predicting pulmonary capillary wedge pressure: the arterial pressure ratio.

The response of arterial blood pressure to an increase in intrathoracic pressure has been shown to be predictive of pulmonary capillary wedge pressure. We devised a new method, which we termed the arterial pressure ratio. We defined arterial pressure ratio as the ratio of systolic blood pressure of the final beat during the strain phase of the Valsalva manoeuvre to that during apnoea before the manoeuvre, and tested the accuracy of arterial pressure ratio in predicting pulmonary capillary wedge pressure. In 30 patients scheduled for elective abdominal aortic reconstruction, following induction of general anaesthesia and tracheal intubation, a 20-G catheter and pulmonary artery catheter were inserted through the radial artery and right internal jugular vein, respectively. Pulmonary capillary wedge pressure was then measured during a brief period of apnoea and the Valsalva manoeuvre was performed by application of pressure to the reservoir bag. Airway pressure was maintained at 30 cmH2O for 10 s and then released. Radial arterial pressure and airway pressure were recorded simultaneously, and arterial pressure ratio was calculated. There was a close linear correlation between arterial pressure ratio and pulmonary capillary wedge pressure (r = 0.88, p < 0.0001).

Lack of specific renal haemodynamic effects of different doses of dopamine after infrarenal aortic surgery

Dopamine is administered frequently in the operating theatre and intensive care unit patients undergoing mechanical ventilation with the aim of specifically enhancing renal blood flow. In an uncontrolled, open study, we administered sequentially different doses of dopamine (0, 2, 4, 8 and 0 microgram kg-1 min-1) during a 1-h period each. Systemic haemodynamic and renal haemodynamic variables were measured simultaneously using a pulmonary artery catheter and radiopharmaceuticals, respectively. We studied seven haemodynamically stable patients (mean age 66 yr), with a serum creatinine concentration < 160 mumol litre-1, after elective infrarenal abdominal aortic reconstruction. All patients received extradural analgesia with bupivacaine and sufentanil, and none had a previous history of heart failure. Dopamine induced a dose-dependent increase in cardiac index which returned to baseline after cessation of the dopamine infusion. Glomerular filtration rate (GFR) increased with all doses of dopamine, whereas renal blood flow (RBF) increased significantly only with the 2- and 4-microgram kg-1 min-1 doses. However, the ratio RBF/cardiac output remained unchanged with the 2- and 4-microgram kg-1 min-1 doses, but decreased with 8 micrograms kg-1 min-1 from 14 (1.5)% to 10 (1.3)%. We conclude that dopamine increased RBF and GFR as a result of an increase in cardiac output.

The potential of simple clinical information and electrocardiogram to predict mortality of primary elective abdominal aortic reconstruction

To assess the importance of simple clinical information to predict mortality after primary elective aortic reconstruction. Retrospective clinical study. Four hundred-three consecutive patients (206 with aortic occlusive disease (51%) and 197 with aneurysmal disease of the abdominal aorta (49%) who underwent primary elective aortic reconstruction during an 8 year study period. Eight potential clinical risk variables and six electrocardiogram related risk variables were studied. The predictive value for postoperative mortality was evaluated univariately for all separate variables by calculation of the odds ratio (OR). Determination of the most predictive sets of risk factors was performed by stepwise logistic regression. Five clinical risk factors showed significant odds ratio's: > 70 years (OR: 4.1), aortic aneurysm (OR: 9.0), myocardial infarction (OR: 8.6), angina pectoris (OR: 4.6), congestive heart failure (OR: 8.1), all p < 0.01. Furthermore, four electrocardiogram related factors showed significant odds ratio's: infarction pattern (OR: 4.3, p = 0.003), ischaemic changes (OR: 6.2, p < 0.001), conductance disturbances (OR: 3.2, p = 0.04), and non-sinus rhythm (OR: 6.2, p = 0.003). Stepwise logistic regression analysis demonstrated that 3 clinical risk factors (aneurysm (OR: 6.1, p = 0.02), myocardial infarction (OR: 3.7, p = 0.01), and congestive heart failure (OR: 5.3, p = 0.006)) contributed significantly to mortality. Addition of any of the electrocardiogram risk factors did not contribute to the prediction of mortality in the presence of these factors. The patients' history and clinical examination provides the most useful information for further selection of additional cardiac tests before elective primary aortic reconstruction. The additional value of the electrodiogram is somewhat overestimated.

Con: Pulmonary artery catheters are not routinely indicated in patients undergoing elective abdominal aortic reconstruction

Con: Pulmonary artery catheters are not routinely indicated in patients undergoing elective abdominal aortic reconstruction

Supraceliac aortic cross-clamping: Determinants of outcome in elective abdominal aortic reconstruction

Purpose: A 7-year experience in which 43 patients underwent supraceliac aortic cross-clamping (SC-AXC) during elective abdominal aortic reconstruction was reviewed.Methods: Operation was performed for abdominal aortic aneurysm (AAA) in 29 (68%) patients, aortoiliac occlusive disease in seven (16%), proximal anastomotic AAA in three (7%), “shaggy” aorta syndrome in three (7%), and in situ grafting of a previously ligated aorta in one (2%) patient. The indications for supraceliac control included pararenal AAA origin (25), pararenal aortic atherosclerosis (18), inflammatory AAA (2), and a short infrarenal aortic stump (1). Vital organ ischemic complications (VOICs) were defined as any major ischemic complication involving the liver, kidneys, bowel, or spinal cord.Results: The incidence of VOICs was significantly increased when concomitant renal or visceral revascularization (CRVR) was required (p = 0.002) and correlated with an increasing SC-AXC time (p = 0.015). In patients undergoing CRVR (n = 16) the perioperative mortality rate was 25%; VOICs developed in six patients and included renal failure (3), mesenteric/colonic ischemia (3), hepatic ischemia with coagulopathy (2), and spinal cord ischemia (1). In contrast, in those not requiring CRVR (n = 27), SC-AXC was well tolerated. There were no VOICs and no deaths; morbidity rate was 33%.Conclusions: The incidence of VOICs associated with the use of SC-AXC is primarily related to the level of preoperative renal or mesenteric insufficiency, the severity of pararenal aortic atherosclerosis, the extent of the operative procedure, and the duration of proximal aortic cross-clamping. In complex abdominal aortic reconstruction in which infrarenal aortic control is either not possible or deemed hazardous, SC-AXC is a safe and valuable technique for achieving proximal control.

Supraceliac aortic cross-clamping: determinants of outcome in elective abdominal aortic reconstruction.

A 7-year experience in which 43 patients underwent supraceliac aortic cross-clamping (SC-AXC) during elective abdominal aortic reconstruction was reviewed. Operation was performed for abdominal aortic aneurysm (AAA) in 29 (68%) patients, aortoiliac occlusive disease in seven (16%), proximal anastomotic AAA in three (7%), "shaggy" aorta syndrome in three (7%), and in situ grafting of a previously ligated aorta in one (2%) patient. The indications for supraceliac control included pararenal AAA origin (25), pararenal aortic atherosclerosis (18), inflammatory AAA (2), and a short infrarenal aortic stump (1). Vital organ ischemic complications (VOICs) were defined as any major ischemic complication involving the liver, kidneys, bowel, or spinal cord. The incidence of VOICs was significantly increased when concomitant renal or visceral revascularization (CRVR) was required (p = 0.002) and correlated with an increasing SC-AXC time (p = 0.015). In patients undergoing CRVR (n = 16) the perioperative mortality rate was 25%; VOICs developed in six patients and included renal failure (3), mesenteric/colonic ischemia (3), hepatic ischemia with coagulopathy (2), and spinal cord ischemia (1). In contrast, in those not requiring CRVR (n = 27), SC-AXC was well tolerated. There were no VOICs and no deaths; morbidity rate was 33%. The incidence of VOICs associated with the use of SC-AXC is primarily related to the level of preoperative renal or mesenteric insufficiency, the severity of pararenal aortic atherosclerosis, the extent of the operative procedure, and the duration of proximal aortic cross-clamping. In complex abdominal aortic reconstruction in which infrarenal aortic control is either not possible or deemed hazardous, SC-AXC is a safe and valuable technique for achieving proximal control.

Equilibrium radionuclide angiocardiography prior to elective abdominal aortic surgery

Equilibrium radionuclide angiocardiography (ERNA) was employed preoperatively in 183 patients undergoing elective abdominal aortic reconstruction to measure left ventricular ejection fraction (LVEF) and to detect abnormal regional wall movement. Abnormal ejection fractions were virtually confined to the 97 patients who had clinical, electrocardiographic or radiographic evidence of heart disease. An operative mortality of 8.7% was recorded. Major cardiac events (defined as myocardial infarction, cardiac failure or malignant ventricular arrhythmia) occurred in 15 of 86 abdominal aortic aneurysm patients (17.4%) and six of 96 (6.25%) patients with aorto-iliac occlusive disease. Patients with an abdominal aortic aneurysm and abnormal LVEF or regional wall motion abnormality were more likely to suffer a cardiac event (p less than 0.001), the event rate exceeding 60% in patients whose LVEF was less than 35%. An abnormal LVEF failed to predict a cardiac event in patients with aorto-iliac occlusive disease. While not indicated in patients lacking clinical evidence of heart disease, ERNA can refine the assessment of cardiac risk, particularly in patients with previous myocardial infarction and define a high risk group in whom aortic reconstruction should be avoided except for the most compelling of indications.

Alfentanil pharmacokinetics in patients undergoing abdominal aortic surgery

The pharmacokinetics of alfentanil, 300 micrograms.kg-1 IV, were determined in patients undergoing elective abdominal aortic reconstruction. The mean age (+/- SD) of the patients was 64.3 +/- 7.4 yr; their mean weight was 74.7 +/- 13.8 kg. Five patients underwent aneurysm repair and six had aortobifemoral grafting. Serum alfentanil concentrations were measured by gas-liquid chromatography in samples drawn at increasing intervals over a 24-hr period. A three-compartment model was fitted to the concentration versus time data. The volume of the central compartment and the volume of distribution at steady state (Vdss) were 0.44 +/- 0.022 and 0.63 +/- 0.32 L.kg-1, respectively. Total drug clearance was 6.4 = 1.9 ml.min-1.kg-1. The elimination half-time was 3.7 +/- 2.6 hr. Patient age was positively correlated with both Vdss and elimination half-time. There were no significant correlations between the pharmacokinetic variables and the duration of aortic cross-clamping, the duration of surgery, or the rate or total volume of IV fluids infused intraoperatively. In general surgical patients, the elimination half-time of alfentanil has been reported to be 1.2-2.0 hr. Although the elimination half-time of alfentanil was longer in patients undergoing abdominal aortic surgery, alfentanil was eliminated much faster than either fentanyl or sufentanil in this patient population.

The importance of plasma colloid osmotic pressure for interstitial fluid volume and fluid balance after elective abdominal vascular surgery.

The relationships between plasma colloid osmotic pressure (COPp) and interstitial fluid volume (IFV) as well as postoperative fluid balance were investigated in a prospective study involving 53 patients undergoing elective abdominal aortic reconstruction. The patients were divided into four groups according to pre- and postoperative blood replacement and fluid therapy programs whereby a continuum of postoperative COPp-values between 33 and 16 mmHg was obtained. Measurements were done before the operation and on days 1 and 4 after surgery. After surgery, COPp below 20 mmHg led to increased IFV. On day 1, COPp was linearly correlated to the total amount of fluid retained during the day of operation. A positive fluid balance of 3 L on this day ensured unchanged extracellular fluid volume (ECV). Of the 3 L, 1.5 L was insensible water loss and 1.5 L had moved into the cells. On day 4 after surgery, COPp below 22 mmHg was associated with increased plasma volume. The authors suggest that COPp be maintained above 20 mmHg after major surgery, and positive fluid balance should not exceed 5 L during the day of operation.

Preoperative coronary artery bypass grafting in patients undergoing abdominal aortic reconstruction

The effect of preoperative aortocoronary bypass grafting on the operative mortality of patients undergoing elective abdominal aortic reconstruction was examined by reviewing a series of 224 consecutive patients (1980 to 1983) (Group I) in whom selective preoperative noninvasive and invasive cardiac screening was used to identify patients with significant coronary stenoses. One patient died during cardiac catheterization. Twenty-seven patients (12 percent) underwent aortocoronary bypass grafting with one operative death (3.7 percent) and one nonfatal myocardial infarction (3.7 percent). These 26 patients subsequently underwent abdominal aortic reconstruction with no mortality and no postoperative myocardial infarction. One hundred ninety-six patients (88 percent) underwent aortic reconstruction without prior aortocoronary bypass grafting with four operative deaths (2 percent), including two fatal myocardial infarctions. The combined operative mortality for Group I patients was 2.3 percent. Three hundred twenty-six patients (Group II) who underwent abdominal aortic reconstruction at this institution from 1970 to 1976 had an 8 percent operative mortality, of which 50 percent of the deaths were due to myocardial infarctions (Group I versus Group II, p < 0.01). Selective preoperative screening for coronary artery disease in patients undergoing elective abdominal aortic reconstruction with aortocoronary bypass grafting in selected patients is safe and may help reduce the operative mortality.

Early Extubation Versus Prophylatic Ventilation in the High Risk Patient

To evaluate whether prophylactic ventilation during the early postoperative period diminishes pulmonary complications, 35 high risk, elderly patients undergoing major, elective abdominal aortic reconstruction were prospectively randomized into either an early extubation group or a prophylactic ventilation group. The 17 patients assigned to the prophylactic ventilation group received mechanical ventilation by assist/control mode until 8 a.m. of the first postoperative day. The 17 patients assigned to the early extubation group were extubated after the operation as soon as they could maintain a pH of 7.35, with a spontaneous respiratory rate of less than 30. Preoperative measurements of functional residual capacity, intrapulmonary shunt, and oxygen delivery were compared to similar measurements during the initial two postoperative days. There were no significant differences between the groups with respect to age, length of operation, duration of anesthesia, operative blood loss, intraoperative fluid administration, or number of intraoperative transfusions. Patients in the prophylactic ventilation group were ventilated for an average of 18.3 +/- 0.5 hours. Patients in the early extubation group were ventilated for an average of 3.3 +/- 0.5 hours (p < 0.0005). No patient in either group required reintubation. Intrapulmonary shunt and oxygen delivery were not significantly different between the groups at any time during the study period. There was no mortality or significant morbidity in either group. These findings suggest that in high risk surgical patients, prophylactic ventilation, per se, may not diminish respiratory complications or improve gas exchange.

Early Extubation versus Prophylactic Ventilation in the High Risk Patient

To evaluate whether prophylactic ventilation during the early postoperative period diminishes pulmonary complications, 35 high risk, elderly patients undergoing major, elective abdominal aortic reconstruction were prospectively randomized into either an early extubation group or a prophylactic ventilation group. The 17 patients assigned to the prophylactic ventilation group received mechanical ventilation by assist/control mode until 8 a.m. of the first postoperative day. The 17 patients assigned to the early extubation group were extubated after the operation as soon as they could maintain a pH of 7.35, with a spontaneous respiratory rate of less than 30. Preoperative measurements of functional residual capacity, intrapulmonary shunt, and oxygen delivery were compared to similar measurements during the initial two postoperative days. There were no significant differences between the groups with respect to age, length of operation, duration of anesthesia, operative blood loss, intraoperative fluid administration, or number of intraoperative transfusions. Patients in the prophylactic ventilation group were ventilated for an average of 18.3 ± 0.5 hours. Patients in the early extubation group were ventilated for an average of 3.3 ± 0.5 hours (p