Effect of aspirin in vascular surgery in patients from a randomized clinical trial (POISE-2).

BACKGROUND: In the POISE-2 (PeriOperative ISchemic Evaluation 2) trial, perioperative aspirin did not reduce cardiovascular events, but increased major bleeding. There remains uncertainty regarding the effect of perioperative aspirin in patients undergoing vascular surgery. The aim of this substudy was to determine whether there is a subgroup effect of initiating or continuing aspirin in patients undergoing vascular surgery. METHODS: POISE-2 was a blinded, randomized trial of patients having non-cardiac surgery. Patients were assigned to perioperative aspirin or placebo. The primary outcome was a composite of death or myocardial infarction at 30 days. Secondary outcomes included: vascular occlusive complications (a composite of amputation and peripheral arterial thrombosis) and major or life-threatening bleeding. RESULTS: Of 10 010 patients in POISE-2, 603 underwent vascular surgery, 319 in the continuation and 284 in the initiation stratum. Some 272 patients had vascular surgery for occlusive disease and 265 had aneurysm surgery. The primary outcome occurred in 13·7 per cent of patients having aneurysm repair allocated to aspirin and 9·0 per cent who had placebo (hazard ratio (HR) 1·48, 95 per cent c.i. 0·71 to 3·09). Among patients who had surgery for occlusive vascular disease, 15·8 per cent allocated to aspirin and 13·6 per cent on placebo had the primary outcome (HR 1·16, 0·62 to 2·17). There was no interaction with the primary outcome for type of surgery (P = 0·294) or aspirin stratum (P = 0·623). There was no interaction for vascular occlusive complications (P = 0·413) or bleeding (P = 0·900) for vascular compared with non-vascular surgery. CONCLUSION: This study suggests that the overall POISE-2 results apply to vascular surgery. Perioperative withdrawal of chronic aspirin therapy did not increase cardiovascular or vascular occlusive complications. Registration number: NCT01082874 ( http://www.clinicaltrials.gov).

The use of transcutaneous oximetry to predict healing complications of lower limb amputations: a systematic review and meta-analysis.

OBJECTIVE: To determine the validity of transcutaneous oximetry (TcPO(2)) as a predictor of lower limb amputation healing complications. DESIGN: A systematic review and meta-analysis. METHODS: We searched five major medical databases, relevant review articles and reference lists and included all studies that evaluated TcPO(2) for its ability to predict lower limb amputation healing failure. We selected eligible articles and conducted data abstraction independently and in duplicate. RESULTS: Thirty-one studies, enrolling 1824 patients with 1960 amputations, met our inclusion criteria. Only one study reported undertaking a multivariable analysis, which demonstrated that a TcPO(2) level below 20 mmHg was an independent predictor of re-amputation occurrence (adjusted odds ratio (OR) 3.08, 95% confidence interval (CI) 1.19-7.98). Fourteen prospective cohort studies reported data that allowed for the calculation of an unadjusted relative risk of lower limb amputation healing complications leading to amputation revision associated with a TcPO(2) level below cut-offs of 10 mmHg (1.80; 95% CI 1.19-2.72), 20 mmHg (1.75; 95% CI 1.27-2.40) 30 mmHg (1.41; 95% CI 1.22-1.62) and 40 mmHg (1.24; 95% CI 1.13-1.39). CONCLUSIONS: This review suggests that TcPO(2) predicts healing complications of lower limb amputations. A value of less than 40 mmHg results in a 24% increased risk of healing complication compared to over 40 mmHg and the risk further increases as the TcPO(2) decreases. There is, however, insufficient evidence to judge whether this tool adds important information beyond clinical data or to suggest an optimal threshold value. There is a need for a large, sufficiently powered study that adjusts for appropriate clinical variables.

Diltiazem cardioplegia. A balance of risk and benefit.

Calcium channel blockers may prevent myocardial injury during cardioplegia and reperfusion. A prospective, randomized trial was instituted to evaluate the hemodynamic and myocardial metabolic recovery in 40 patients undergoing elective aorta-coronary bypass with either diltiazem in crystalloid potassium cardioplegia (n = 20) or crystalloid potassium cardioplegia (n = 20). In a preliminary trial, doses between 150 and 250 micrograms/kg reduced the period of heart block after cross-clamp removal (90 +/- 110 minutes) from that found with higher doses and improved myocardial metabolism. In the randomized trial, diltiazem cardioplegia (150 micrograms/kg) produced coronary vasodilatation during cardioplegia and produced less reactive hyperemia during reperfusion. Myocardial oxygen extraction was lower and myocardial lactate production was less after diltiazem cardioplegia during reperfusion. Tissue adenosine triphosphate and creatine phosphate concentrations were preserved better after diltiazem cardioplegia. The postoperative creatine kinase MB levels were less (p less than 0.05) after diltiazem cardioplegia, which indicated less myocardial injury. Postoperative volume loading demonstrated that systolic function (the relation between systolic blood pressure and end-systolic volume index) was depressed after diltiazem cardioplegia compared to crystalloid cardioplegia, but cardiac index was higher because afterload (mean arterial pressure) was lower and preload (end-diastolic volume index) was higher. Diltiazem cardioplegia preserved high-energy phosphates, improved postoperative myocardial metabolism, and reduced ischemic injury after elective coronary bypass. However, diltiazem was a potent negative inotrope and produced prolonged periods of electromechanical arrest. Diltiazem cardioplegia may be of value in patients with severe ischemia but should be used with caution in patients with ventricular dysfunction, and a dose-response relation must be established at each institution before clinical use.

Hemodynamic and myocardial metabolic consequences of PEEP.

The cardiac effects of positive end expiratory pressure (PEEP) were examined in 50 patients six hours after elective coronary bypass surgery. Increasing the level of PEEP from 5 to 10 to 15 cm H2O decreased cardiac index (evaluated by thermodilution), stroke index and left ventricular end diastolic volume index without a change in left ventricular ejection fraction (evaluated by nuclear ventriculography). Right ventricular end diastolic volume index remained unchanged. Coronary sinus blood flow (measured by the continuous thermodilution technique) and myocardial oxygen and lactate consumption were unchanged with the application of 15 cm H2O PEEP. In 21 patients, volume loading (250 ml [mL] of plasma) was performed at 5 cm, and again at 15 cm H2O PEEP. Volume loading produced a similar increase in cardiac volumes and cardiac index at 5 and 15 cm H2O PEEP. Right and left ventricular performance and left ventricular systolic function were not altered by PEEP (by analyses of covariance). Coronary sinus blood flow and myocardial oxygen consumption increased with volume loading at 5 and 15 cm H2O of PEEP, but myocardial lactate utilization tended to increase at 5 cm, and decrease at 15 cm H2O PEEP (p = 0.08). Of the 33 patients who underwent complete hemodynamic and metabolic measurements, 16 increased cardiac lactate utilization at 15 cm H2O PEEP and 17 decreased cardiac lactate utilization at 15 cm H2O PEEP. PEEP decreased cardiac index, perhaps by reducing left but not right ventricular volumes. Volume loading during PEEP restored cardiac index and revealed no depression in myocardial performance or systolic function. With the application of PEEP, myocardial metabolism was maintained in half the patients, but ischemic metabolism was observed in the other half.

Quantification of skeletal muscle necrosis in the lower extremities using 99Tcm pyrophosphate with single photon emission computed tomography.

No non-invasive quantitative method is currently available for measuring the amount of regional skeletal muscle necrosis in humans. A threshold method using 99Tcm pyrophosphate (PPi) with single photon emission computed tomography (SPECT) has been reported to quantify muscle necrosis successfully in a canine model. This method has been modified to measure muscle necrosis in the lower extremities of human patients. Modifications include adding background subtraction and using the contralateral unaffected lower extremity as background region. A region of interest was also manually drawn around the affected lower extremity muscle to exclude the tibia. In order to identify the group of patients with no significant necrosis and with diffuse hyperaemia, nine control subjects were studied. The variance of the counts within the pixels of the lower extremities was 132 (S.D. = 27). A variance of greater than 159 was considered as being significant for necrosis. Thirteen patients were studied. Six patients had significant muscle necrosis (462 ml, S.D. = 280 ml). All except one patient (who had a small amount of muscle necrosis) developed foot drop. Seven patients had no significant necrosis. All patients had normal ankle dorsiflexion. It is possible to quantify regional muscle necrosis using PPi with SPECT. Volume of necrosis determined by this method can also predict clinical outcome.

Laparoscopic aortic injury leading to delayed aortoenteric fistula: an alternative technique for repair.

Complications of laparoscopic procedures occur in up to 10% of cases. The most lethal complication relates to injury of major retroperitoneal vascular structures. A case of aortoenteric fistula referred to the vascular surgical service 1 month following emergency repair of laparoscopic aortic injury is presented. A technique utilizing a saphenous vein panel graft for distal aortic repair is described. Review of reported cases demonstrates that major retroperitoneal vascular injury during laparoscopy is rare, with a reported incidence of 3 to 10/10,000 procedures, and a mortality of up to 20%. Simple suture repair is the usual form of treatment, but specialized techniques are occasionally required.

Radiological intervention for the failing in situ vein bypass.

With close surveillance, deteriorating hemodynamics may signal a failing in situ bypass that can be salvaged by timely intervention. The purpose of this report is to summarize our experience with in situ bypass salvage using interventional radiology. Twenty-nine patients underwent arteriography following bypass occlusion or when an ankle/brachial index reduction of greater than 0.15 was detected between two consecutive office visits. Eighteen percutaneous transluminal dilatations were performed; one patient underwent repeat dilatation after 36 months, a second had four dilatations over 40 months. Ten significant arteriovenous fistulae were identified and were successfully embolized with 3 mm coils. One patient underwent excision of a retained valve. Six patients had initial fibrinolytic therapy for graft occlusion. The morbidity of these interventions was low; one bypass was disrupted following percutaneous transluminal dilatation but was successfully salvaged surgically. The average time from the original surgery to intervention was six months (one to 26 months); and the average follow-up after intervention was 22 months (three to 62 months) over which time patency was maintained in the majority. When a correctable problem is identified with appropriate vascular lab surveillance, interventional radiology is a useful alternative to surgery for bypass salvage.

Reducing the risk of urgent revascularization for unstable angina: a randomized clinical trial.

A prospective, randomized trial was instituted to determine whether blood cardioplegia (BC) could reduce the morbidity and mortality for patients undergoing urgent coronary bypass for unstable angina. One hundred forty patients who came to the hospital with prolonged angina at rest and who required urgent revascularization because their symptoms were resistant to medical therapy were randomized to receive BC (n = 70) or crystalloid cardioplegia (CC) (n = 70). The operative mortality rate was 2.8%, the incidence of myocardial infarction was 8.6%, the incidence of low output syndrome was 18% and morbidity (myocardial infraction or low output syndrome) was 23%. Patients who received BC had a significantly lower mortality rate (BC, 0%; CC, 5%; p less than 0.05) and incidence of myocardial infarction (BC, 4%; CC, 13.5%; p less than 0.05) or low output syndrome (BC, 10%; CC, 19%; p less than 0.05). The highest postoperative CK-MB level was less after BC (BC, 31 +/- 17 U/L; CC, 56 +/- 13 U/L; p less than 0.05). Preoperative predictors of postoperative morbidity in addition to the type of cardioplegia included the response to medical therapy, persistent ischemic electrocardiographic changes, left ventricular ejection fraction, and age. A multivariate analysis identified the type of cardioplegic protection (p = 0.008) and age (p = 0.05) as significant independent predictors of postoperative morbidity. BC reduced the risk of urgent revascularization for unstable angina.