Incidence and predictors of postoperative deep vein thrombosis in cardiac surgery in the era of aggressive thromboprophylaxis.

BACKGROUND: Deep venous thrombosis (DVT) is a well-known complication of surgery but its significance in cardiac surgery is not well defined. We reviewed the results of a prospective observational protocol for repeated postoperative lower extremity duplex venous scans (DVS) screening starting on postoperative day 3-4 through hospital discharge. METHODS: A total of 1,070 (88%) of the 1,219 overall unique adult cardiac surgery patients at our institution (August 2005 to December 2007) underwent DVS screening. The 149 exclusions included 15 due to early death (1.2%); 39 with a history of preoperative DVT (3.2%) and 93 missed patients (7.6%). All patients underwent maximally aggressive thromboprophylaxis as stipulated by the American College of Chest Physicians Evidence-Based Clinical Practice Guidelines (8th Edition), and complemented with postoperative clopidogrel in coronary artery bypass grafting patients. RESULTS: A positive DVS (within 30 days of surgery) for at least 1 lower extremity DVT was observed in 139 of 1,070 eligible patients (DVT: 13.0%). Incidence of DVT was similar in coronary artery bypass grafting (118 of 948; 12.4%) and valve (33 of 237; 13.9%) patients. Hemorrhagic complication requiring reexploration occurred in only 19 patients (1.8%) despite thromboprophylaxis. The DVT cohort showed significantly worse operative (in-hospital or <30 days) mortality (DVT: 9 [6.5% vs no DVT: 16 [1.7%];] p < 0.003), postoperative hospital stay (14.4 +/- 12.9 vs 8.3 +/- 7.3 days; p < 0.001), and 30-day hospital readmissions (20.9% vs 10.3%; p = 0.001). Multivariate logistic regression predictors for developing DVT were increased age (odds ratio [OR; 95% confidence interval = 1.24 (1.07 to 1.41) per 10-year increments]), blood transfusion (OR = 2.24 [1.49 to 3.39]), initial time on the ventilator/prolonged mechanical ventilation (OR = 1.02 [1.01 to 1.04] per 10-hour increments), and need for reintubation (OR = 2.57 [1.48 to 4.47]). CONCLUSIONS: A considerable number (13%) of cardiac surgery patients develop otherwise silent DVT despite maximal thromboprophylaxis. Aggressive mechanical and pharmacologic thromboprophylaxis in this population appears safe and indicated. Whether routine postoperative DVS screening alters patients' outcomes and is cost effective remains undefined, but should be considered in case of a complicated-prolonged postoperative course.

Myocardial protection of insulin and potassium in a porcine ischemia-reperfusion model.

BACKGROUND: We previously evaluated cardioprotective effects of glucose-insulin-potassium (GIK) in a porcine ischemia-reperfusion model; our results showed less myocardial pH decrease during ischemia and reperfusion and faster normalization of ATP and glucose during reperfusion. The proposed protective mechanism was facilitation of glucose transport for myocardial metabolism. The objective of this study was to assess the impact of insulin-potassium (IK) alone on myocardial metabolism. METHODS: Male swine received continuous infusion of IK (IK group, n = 10), GIK (GIK group, n = 10), or standard lactated Ringer's (LR) solution (controls, n = 10). Induction of 20 minutes of ischemia in the left anterior descending (LAD) artery distribution was followed by 20 minutes of reperfusion. Real-time biosensors recorded pH and glucose levels in ischemic and nonischemic beds. Myocardial biopsies in the distribution of the LAD assessed ATP levels. Groups were compared using the Kruskal-Wallis and Mann-Whitney tests. RESULTS: Real-time data are presented as percent change from baseline. At less than 10 minutes of ischemia, the average pH change was less for the IK group than the LR group (0.03% +/- 0.21% vs -2.06% +/- 1.23%; P = .001), and the pH change in the IK group was similar to the GIK group. After 10 minutes of ischemia and during the first 10 minutes of reperfusion, the IK group experienced pH changes that were similar to the LR group. Biopsies after 20 minutes of ischemia and 20 minutes of reperfusion showed less of a decline in ATP levels for the IK group compared to the LR group. Glucose at all time points demonstrated no statistically significant differences. CONCLUSION: IK infusion alone demonstrates cardioprotective effects during early ischemia; however, compared to GIK infusion after 20 minutes of ischemia and reperfusion, myocardial pH and glucose levels were not sustained. Although insulin may facilitate glucose transport during ischemia, additional glucose in combination with IK enhances myocardial protection during reperfusion. This finding suggests that GIK enhancement during acute ischemia-reperfusion may improve myocardial protection.