F. Michael Ameli

The role of central haemodynamic monitoring in abdominal aortic surgery. A prospective randomised study

To test the hypothesis that central haemodynamic monitoring is not necessary in all patients undergoing abdominal aortic surgery, a prospective randomised study in 40 consecutive patients undergoing elective abdominal aortic surgery was carried out. Patients with unstable angina, recent myocardial infarction (less than or equal to 6 months), and left ventricular ejection fraction (LVEF) less than 0.50 were excluded. Twenty-one patients had perioperative central haemodynamic monitoring while 19 patients had central venous pressure monitoring alone. Parameters studied included, perioperative haemodynamics and fluid balance, perioperative cardiac drug administration, operation time and clamp time, postoperative renal function, incidence of postoperative ventilation and line complications, duration of hospital and ICU stay, and 30 day postoperative outcome. Results obtained were compared with a high risk group of patients (LVEF less than 0.50) undergoing similar surgery. Statistical analysis failed to show any difference in outcome for any variable measured in either low risk group. All serious postoperative cardiac complications occurred in patients with LVEF less than 0.50 (P less than 0.0001). These data suggest that patients with LVEF greater than or equal to 0.50 are at low risk of developing postoperative cardiac complications and can be successfully managed perioperatively without the added potential risks and costs of central haemodynamic monitoring.

The Effect of Postoperative Smoking on Femoropopliteal Bypass Grafts

Effect of smoking habits on limb loss rates and cumulative patency rates of 136 arterial reconstructions performed for lower limb ischemia were analyzed in a five year follow-up retrospective study. Of 121 patients, 103 (85%) smoked before the operation and 43 of the smokers (42%) discontinued smoking postoperatively. Patients who continued to smoke more than 15 cigarettes per day (34 patients) increased the probability of losing their limb approximately five times at two years and three times at five years postoperatively, compared with nonsmokers and smokers of up to 15 cigarettes per day (87 patients) (p = 0.013). Cumulative patency rates of nonsmokers and smokers of up to five cigarettes per day (Group A, 66 patients) were not significantly influenced (p = 0.518) by preoperative symptoms (claudication versus limb salvage). However, for smokers of more than five cigarettes per day (Group B, 55 patients), at five years claudicants had a cumulative patency rate of 62.9% compared to 38.3% for limb salvage patients (p = 0.015). In group A at five years, autologous saphenous vein grafts had a cumulative patency rate of 74.2%, compared to 24% for prosthetic grafts (P = 0.013). In group B the CPR differences between autologous saphenous vein and prosthetic grafts were not significantly different (p = 0.394). Multiple interactions between smoking and variables like age, preoperative symptoms, and graft material demonstrate the complexity of the effects of smoking on cumulative patency rate and the need for sub-grouping and removal of confounding factors. In view of the adverse affects of continued smoking on postrevascularization prognosis, patients should be strongly advised to discontinue smoking.

Current indications for axillounifemoral and axillobifemoral bypass grafts

Revascularization of the lower extremities may require an axillofemoral bypass when an aortobifemoral bypass is contraindicated. Thirty-one patients underwent axillounifemoral and 59 had an axillobifemoral bypass, with a mortality rate of 9%. The indication for operation was limb salvage in 67%, intra-abdominal sepsis in 21%, and disabling claudication in 12%. Cumulative survival, patency, and limb salvage rates were determined by life-table analysis. The cumulative patency and limb salvage rates (with standard errors) at 3 years were 68% +/- 8% and 78% +/- 9%, respectively. When stratified for type of operation, axillobifemoral bypass had a superior patency rate compared with axillounifemoral bypass (log rank = 3.882, p less than 0.05). There was no significant difference when patients were stratified for diabetes (log rank = 2.213, p = no significance [NS]), operative indication (disabling claudication vs. limb salvage) (log rank = 0.0005, p = NS), or outflow (no profundaplasty vs. profundaplasty) (log rank = 2.011, p = NS). We conclude that axillofemoral bypass is a reasonable alternative for revascularization in high-risk patients or in those patients in whom a transabdominal approach is contraindicated. We recommend aggressive use of the profunda femoris artery when the superficial femoral artery is occluded to achieve optimal results.

The effect of femoral arteriography on the incidence of groin contamination and postoperative infections

A prospective study is presented on the effects of preoperative femoral arteriography on bacterial contamination and postoperative wound complications from groin incisions. Forty-four femoral reconstructive procedures (88 groin incisions) for aortoiliac disease were performed. Positive cultures occurred in 43.2% of patients and in 30.7% of the 88 incisions. There was no correlation found between the site of arteriography and positive cultures (Spearman correlation coefficient, p > .10). No correlation was found between the presence of hematoma due to arteriography and subsequent positive groin culture (Spearman correlation coefficient, p > .10). A higher incidence of positive cultures did occur for patients who had a difficult arteriographic procedure (Fishers exact test, p=.020) or whose reconstructive procedure was greater than four hours (Fischers exact test, p=.047). Seven patients had postoperative groin wound complications (15.9%), including three lymph leaks (6.8%) and four confirmed or suspected infections (9%). There were no graft infections. No correlation was found between the site of arteriography and the site of wound complication (Spearman correlation coefficient, p > .10). Neither positive culture results nor difficult arteriography nor presence of hematoma were accurate predictors of postoperative wound complications. We conclude that transfemoral arteriography does not increase the risk of complications of arterial reconstruction involving a femoral anastomosis.

A statistical assessment of the dependability of transcutaneous tissue oxygen tension measurements

Transcutaneous oxygen tension measurements (PtcO2) were obtained for subjects in two groups: peripheral vascular patients (N = 15) and disease-free controls (N = 9). Readings were taken in each of three locations, arm, knee and foot, in supine and erect positions, at fixed and random times, on each of 3 consecutive days. The dependability (the proportion of true variance in total variance) of PtcO2 measurements was evaluated using a generalizability model. The preliminary generalizability study analysis indicated that day-to-day variation of PtcO2 level was larger than within-day variation. Therefore, in order to decrease the measurement error variance one would preferably increase the number of days for measurements (nd) rather than increase the number of measurements within each day (nt). A decision study analysis was also performed which resulted in estimates of error variance and two interdependent dependability measures: dependability coefficients (DCs) and signal to noise ratios (S/Ns). PtcO2 dependability values were generally different for the two groups. Cases had high DCs and S/Ns (DC greater than or equal to 0.9, S/N greater than or equal to 9) in all location-position combinations except for arm measurements. On the other hand, controls had low and unacceptable DCs and S/Ns (DC less than 0.8, S/N less than 4) in all location-position combinations. Cases and controls had generally lower dependability values when PtcO2 ratios were analyzed. The only two ratio-position categories for which dependability values were in the acceptable range (DC greater than or equal to 0.8, S/N greater than or equal to 4) were foot/arm erect and foot/arm supine for the cases.(ABSTRACT TRUNCATED AT 250 WORDS)

Percutaneous transluminal angioplasty without anticoagulation

This paper presents the results of a retrospective study of 110 percutaneous transluminal angioplasties done over a period of two years on 110 consecutive patients. Anticoagulation or antiplatelet drugs were not used during or after percutaneous transluminal angioplasty. Life-table analysis was used to calculate success rates at one and three months following the procedure. Success rates were determined using three criteria: clinical improvement, pre- and post-percutaneous transluminal angioplasty Doppler studies, and radiographic appearance. Claudication was present in 87 (79%) patients and severe ischemia in 23 (21%) patients. Sixty-eight (62%) PCTAs were done in the iliac arteries, 35 (32%) in the femoral arteries, and 7 (6%) in the popliteal artery. The majority of patients (61%) had 50%-75% arterial stenosis and only 18% had complete occlusion. Percutaneous transluminal angioplasty in the iliac arteries had the best results with cumulative success rates of 90% and 85% at one and three months, respectively. Success rates in the femoral arteries were 83% and 79% and in the popliteal artery 71% and 57% at one and three months, respectively. None of our patients required amputation. Ten patients (9.1%) suffered the following complications within 30 days of percutaneous transluminal angioplasty: death (2), thrombosis (2), perforation (3), minor hematoma (2), and false aneurysm (1). In conclusion, we have shown that percutaneous transluminal angioplasty can be performed safely and effectively without the use of anticoagulation and its associated risks.

Ischemic damage to the spinal cord following end-to-side aortobifemoral bypass.

A patient presenting with urinary retention was found to have progressive spinal cord ischemia subsequent to an end-to-side aortobifemoral bypass for atherosclerotic disease. This serves as a vivid reminder of the possibility of this complication even in ischemic disease and that urinary retention may be the initial symptom of cord ischemia. A review of the literature on spinal cord ischemia following abdominal aortic surgery is presented.

The influence of central haemodynamics on transcutaneous oxygen (TcpO2) measurements

Transcutaneous oxygen measurements (TcpO2) have been shown to be an index of tissue perfusion and it has been suggested that the main haemodynamic variable influencing tissue perfusion is cardiac output, assuming that inspired oxygen remains constant. To investigate this hypothesis we studied 23 consecutive patients in order to identify if changes in cardiac output correlated with similar changes in TcpO2 measurements. No correlation was found to suggest that cardiac output was the main haemodynamic determinant of TcpO2 measurements.

Preoperative Dynamic Assessment of Cardiac Reserve in Patients Following Abdominal Aortic Surgery. A Probability Analysis

In order to estimate cardiac reserve preoperatively the authors studied 33 con secutive patients aged forty-four to eighty-one years (mean ± SD, 67.2 ± 7.3) scheduled for elective infrarenal abdominal aortic surgery. All patients had pul monary artery catheters inserted on the morning of surgery and had Starling curves constructed by plotting of the rate of change in cardiac output against the rate of change in pulmonary artery wedge pressure (PAWP) with a specific volume loading protocol. The slope of the curve and the PAWP, which cor responded to the maximum cardiac output (PAWPmax), were carefully noted in each patient. A deliberate effort was made perioperatively to maintain each patient on the upslope of the curve and not to exceed their estimated PAWP max. Four patients developed a major postoperative cardiac complication and 1 patient died. All complications occurred in patients with a Starling slope of < 0.035 (p = 0.0003). By utilization of this slope in a derived probability model the authors could accurately and quantitatively predict which patients were at greatest risk of developing a postoperative cardiac complication following ab dominal aortic surgery.

Intravenous Digital Subtraction Arteriography in the Evaluation of Vascular Grafts

Between 1982 and 1986 intravenous digital subtraction arteriography was used to evaluate vascular grafts in 97 patients (54 males, 43 females). Indications included recurrent symptoms, absent or diminished pulses, a drop in Doppler pressure measurements, and clinical uncertainty with respect to graft patency. Problems identified included graft stenosis, stenosis of the anastomosis or its distal vessels, false aneurysm, arteriovenous fistula and emboli. Forty-eight operations were carried out following intravenous digital subtraction arteriography, and radiographic findings were verified surgically. Twice, intravenous digital subtraction arteriography did not show significant graft findings which were discovered at surgery. Thus intravenous digital subtraction arteriography showed a sensitivity of 95.8% and specificity of 100%. Complications following intravenous digital subtraction arteriography were: two patients developed urticaria, and one superficial thrombophlebitis. There were no cases of pulmonary edema or death. In conclusion intravenous digital subtraction arteriography is very useful in the diagnosis of graft-related problems if done on a selective basis looking at graft and anastomosis site only, intravenous digital subtraction arteriography is done on an outpatient basis, has high sensitivity and specificity, good patient acceptance, is safe, fast and is less expensive than conventional arteriography.