Relationship of protamine dosing with postoperative complications of carotid endarterectomy.

Protamine sulfate (PS) neutralization of heparin (HEP) given during carotid endarterectomy (CEA) has been previously associated with an increased postoperative stroke rate. Dosing regimens of PS have varied in previous studies. The accuracy of PS dosing and its effect on postoperative complications was analyzed. The medical records of all patients undergoing elective CEAs from January 1993 to June 1996 in our institution were reviewed. A hematoma was defined as either an event requiring return to the operating room or when repeatedly identified in the medical record. The accuracy of dosing PS was determined utilizing a formula calculating the logarithmic exponential decay of HEP, which determined the residual HEP at the time of PS dosing. An ideal PS dose was then calculated and compared to the dose given. Statistical analyses was performed using a Fisher's exact test as well as the Student's t-test. Four hundred-seven CEAs were performed in 365 patients. There were 10/407 (2.5%) postoperative strokes (STROKE) and 11/407 (2.7%) hematomas, 3 of which required reoperation. Results indicate that (1) the administration of PS significantly reduced the incidence of postoperative hematoma; (2) there appears to be an association between the administration of PS and STROKE; (3) the inaccuracy in dosing PS appears to be based on a decision to dose PS to the total HEP given rather than the residual HEP on board at the time of neutralization. The effect of PS overdosing is unclear, but it may play a role in STROKE.

Perioperative predictors of colonic ischemia after ruptured abdominal aortic aneurysm.

PURPOSE: Colonic ischemia and colonic resection occur frequently after ruptured abdominal aortic aneurysm (rAAA). The purpose of this study was to identify the perioperative risk factors that might help to determine earlier in the postoperative period which patients are at risk for colonic ischemia and colonic resection. METHODS: The medical records of the 43 patients who underwent repair of rAAA from January 1989 to November 1997 were reviewed. The data were reviewed for the following factors: acidosis, pressor agents, lactate levels, guaiac status, cardiac index, coagulopathy, early postoperative bowel movement, the lowest intraoperative pH level, the temperature at the conclusion of the case, the location and duration of aortic cross clamping, the amount of fluid boluses administered after surgery, the amount of packed red blood cells administered during the case, and the average systolic blood pressure at admission and during surgery. Univariate analysis was performed with Fisher exact test, chi2 test, and Student t test. Multivariate analyses also were performed with the variables that were found to be significant on the univariate analysis. RESULTS: Thirteen of the 43 patients (30. 2%) had colonic ischemia, and seven of the 13 underwent colonic resection (53.8%). The overall mortality rate was 51.2% (22/43) five of the deaths were intraoperative and excluded from the study. In a comparison of the patients who had colonic ischemia with those who did not, statistically significant differences were found in the following variables: average systolic blood pressure at admission 90 mm Hg or less, hypotension of more than 30 minutes' duration, temperature less than 35 degreesC, pH less than 7.3, fluid boluses administered after surgery 5 L or more, and packed red blood cells 6 units or more. Multivariate analysis indicated that the number of these variables present correlated significantly with the positive predicted probability of colonic ischemia occurring. No patient with two factors or fewer had an ischemic bowel, and the positive predictive probability of colonic ischemia for those patients with six factors was 80%. CONCLUSION: The results of this study show that: (1) colonic ischemia after rAAA may be predicted with the presence of two or more specific perioperative factors, (2) the lack of a guaiac-positive bowel movement may be misleading for the early diagnosis of colonic ischemia, and (3) more than 50% of the patients with colonic ischemia will require a colonic resection. We recommend that any patient with rAAA with more than two perioperative factors undergo sigmoidoscopy every 12 hours after surgery for 48 hours to rule out colonic ischemia without waiting for early or guaiac-positive bowel movement.

Is preoperative cardiac evaluation for abdominal aortic aneurysm repair necessary?

PURPOSE: It is reported that 25% to 50% of patients with abdominal aortic aneurysms (AAA) have severe coronary artery disease (CAD) and should undergo an aggressive cardiac workup before AAA repair. In contrast, it has been our policy that patients referred for AAA repairs undergo no cardiac testing before surgery. METHODS: This report reviews the last 113 consecutive patients who underwent elective AAA repair by the senior author using this policy. Seventy-four patients (group A) had only an electrocardiogram before surgery. The remaining 39 patients (group B) were referred having already had additional testing that included a thallium stress test (n = 20), echocardiogram (n = 18), multiple gated acquisition (MUGA) scan (n = 3), cardiac catheterization (n = 8), or some combination of these. RESULTS: There was no statistical difference between group A and group B with regard to age, sex, tobacco use or history of coronary artery disease, diabetes mellitus, stroke (CVA), hypertension, peripheral vascular disease, or chronic obstructive pulmonary disease. Group B more commonly had a history of myocardial infarction (41% vs 19%, p < 0.03) and congestive heart failure (23% vs 7%, p < 0.03). During surgery there was no significant differences in blood loss, transfusion requirements, or operative times. There were no myocardial infarctions in group A and two (5.1%) in group B, which was not significantly different. Other complications, such as CVA, renal failure, pulmonary failure, pneumonia, wound infection, and hemorrhage, were not significantly different between the two groups. Postoperative hospital stay was not significantly different. There were three deaths in the entire series (2.7%), and only one in group B was cardiac-related in a patient with known end-stage cardiac disease and a symptomatic 8 cm AAA. CONCLUSIONS: These data indicate that most patients with AAA can safely undergo repair with no cardiac workup and that cardiac workup before AAA repair contributes little information that impacts on treatment or final clinical outcome. We conclude that cardiac testing in preparation for AAA repair is not usually necessary and that intraoperative hemodynamic management may be the most important variable in determining outcome.

Laparoscopic-assisted abdominal aortic aneurysm repair.

Since the advent of laparoscopy, the sweeping changes seen in general surgery have not been paralleled in vascular surgery. There have been case reports of laparoscopic-assisted aortobifemoral bypass for occlusive disease. Because aneurysmal disease comprises the majority of aortic surgery, we pursued animal and cadaveric feasibility studies for laparoscopic-assisted abdominal aortic aneurysm (AAA) repair. We present a case report of the first clinical case performed under Institutional Review Board protocol using this technique. The patient was a 62-year-old male with a 6-cm infrarenal AAA. After obtaining a pneumoperitoneum, a modified fish retractor was used to exclude the bowel. Ten 11-mm ports provided access to laparoscopically dissect the neck of the aneurysm and the iliac vessels. Then, a 10-cm minilaparotomy was performed and standard vascular clamps were inserted via the port incisions. Standard aneurysmorraphy was performed with a polytetrafluoroethylene (PTFE) tube graft. Laparoscopy conferred three major benefits: better visualization of the aneurysm neck, less bowel manipulation, and avoidance of hypothermia. This case report illustrates the feasibility of laparoscopic-assisted aneurysm repair. Controlled human studies will define the role of laparoscopy in AAA surgery.

Hemodialysis graft salvage.

Hemodialysis access procedures account for a large percentage of patients undergoing surgical treatment. Salvage procedures are frequently used to extend the life of a thrombosed graft and thereby maximize the limited available access sites. Factors that may influence the success of salvage procedures, as well as the financial risk to benefit comparison, may be of increasing importance in the era of aggressive medical cost containment. The charts of 70 patients who underwent 116 thrombectomies or revisions of polytetrafluoroethylene (PTFE) hemodialysis arteriovenous grafts of the upper extremity for thrombosis were retrospectively analyzed. Patency of salvaged grafts by life-table analysis was 75.0 percent at two days, 45.0 percent at 30 days, 18.0 percent at 120 days and 2.5 percent at one year. Patency was 59 and 25 percent for revised grafts at 30 and 120 days, respectively, versus 30 and 10 percent at the same time intervals for thrombectomized grafts only. Minimum combined operative and hospital costs were $4,350 per salvage attempt. Salvage patency of PTFE dialysis grafts of the upper extremity was dismal, especially when thrombectomy alone was used. No specific patient factors were predictive of patency interval. Based upon these results, we cannot continue to recommend graft thrombectomy alone for thrombosed dialysis grafts. Because the poor results with graft revision as well, placement of a new graft without any attempt at salvage may be the best therapeutic and cost-effective option.

Hypothermia and bleeding during abdominal aortic aneurysm repair.

Patients undergoing abdominal aortic aneurysm repair routinely have a depressed core body temperature during surgery, and hypothermia is known to cause abnormalities in coagulation. This study was designed to determine whether platelet function is altered as a result of hypothermia or heparin during abdominal aortic aneurysm repair. Ten patients scheduled for abdominal aortic aneurysm surgery were prospectively studied. Bleeding times and temperature were measured every hour beginning preoperatively. Each patient was heparinized intraoperatively, and the effects reversed with protamine sulfate prior to closure. Despite efforts to keep the patients warm, all of them developed hypothermia (mean lowest core temperature 34.8 +/- 0.7 degrees C). A significant linear relationship between the change in core temperature and the change in bleeding time was demonstrated. In 7 of 10 cases the greatest change in bleeding time occurred when patients experienced the lowest mean core temperature and not when they were heparinized. These data suggest that hypothermia has a marked effect on platelet function during abdominal aortic aneurysm repair. Although heparin can cause abnormalities in platelet function, hypothermia may be a more important role in inhibiting normal platelet function. By preventing severe hypothermia (< 35 degree C), excessive bleeding associated with abdominal aortic aneurysm repair may be minimized without the concomitant risk of blood product transfusion.