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Background
All international guidelines recommend perioperative antibiotic prophylaxis (PAB) should be routinely administered to patients undergoing cardiac surgery. However, the duration of PAB is heterogeneous and controversial.
Methods
Between 01.01.2011 and 31.12.2011, 1096 consecutive cardiac surgery patients were assigned to one of two groups receiving PAB with a second-generation cephalosporin for either 56 h (group I) or 32 h (group II). Patients’ characteristics, intraoperative data, and the in-hospital follow-up were analysed. Primary endpoint was the incidence of surgical site infection (deep and superficial sternal wound-, and vein harvesting site infection; DSWI/SSWI/VHSI). Secondary endpoints were the incidence of respiratory-, and urinary tract infection, as well as the mortality rate.
Results
615/1096 patients (56,1%) were enrolled (group I: n = 283 versus group II: n = 332). There were no significant differences with regard to patient characteristics, comorbidities, and procedure-related variables. No statistically significant differences were demonstrated concerning primary and secondary endpoints. The incidence of DSWI/SSWI/VHSI were 4/283 (1,4%), 5/283 (1,7%), and 1/283 (0,3%) in group I versus 6/332 (1,8%), 9/332 (2,7%), and 3/332 (0,9%) in group II (p = 0,76/0,59/0,63). In univariate analyses female gender, age, peripheral arterial obstructive disease, operating-time, ICU-duration, transfusion, and respiratory insufficiency were determinants for nosocomial infections (all ≤ 0,05). Subgroup analyses of these high-risk patients did not show any differences between the two regimes (all ≥ 0,05).
Conclusions
Reducing the duration of PAB from 56 h to 32 h in adult cardiac surgery patients was not associated with an increase of nosocomial infection rate, but contributes to reduce antibiotic resistance and health care costs.
Background
Mitochondrial impairment can result from myocardial ischemia reperfusion injury (IR). Despite cardioplegic arrest, IR-associated cardiodepression is a major problem in heart surgery. We determined the effect of increasing ischemia time on the respiratory chain (RC) function, the inner membrane polarization and Ca\(^{2+}\) homeostasis of rat cardiac subsarcolemmal mitochondria (SSM).
Methods
Wistar rat hearts were divided into 4 groups of stop-flow induced warm global IR using a pressure-controlled Langendorff system: 0, 15, 30 and 40 min of ischemia with 30 min of reperfusion, respectively. Myocardial contractility was determined from left ventricular pressure records (dP/dt, dPmax) with an intraventricular balloon. Following reperfusion, SSM were isolated and analyzed regarding electron transport chain (ETC) coupling by polarography (Clark-Type electrode), membrane polarization (JC1 fluorescence) and Ca2+-handling in terms of Ca\(^{2+}\)-induced swelling and Ca\(^{2+}\)-uptake/release (Calcium Green-5 N® fluorescence).
Results
LV contractility and systolic pressure during reperfusion were impaired by increasing ischemic times. Ischemia reduced ETC oxygen consumption in IR40/30 compared to IR0/30 at complex I-V (8.1 ± 1.2 vs. 18.2 ± 2.0 nmol/min) and II-IV/V (16.4 ± 2.6/14.8 ± 2.3 vs. 2.3 ± 0.6 nmol/min) in state 3 respiration (p < 0.01). Relative membrane potential revealed a distinct hyperpolarization in IR30/30 and IR40/30 (171.5 ± 17.4% and 170.9 ± 13.5%) compared to IR0/30 (p < 0.01), wearing off swiftly after CCCP-induced uncoupling. Excess mitochondrial permeability transition pore (mPTP)-gated Ca\(^{2+}\)-induced swelling was recorded in all groups and was most pronounced in IR40/30. Pyruvate addition for mPTP blocking strongly reduced SSM swelling in IR40/30 (relative AUC, ± pyruvate; IR0/30: 1.00 vs. 0.61, IR15/30: 1.68 vs. 1.00, IR30/30: 1.42 vs. 0.75, IR40/30: 1.97 vs. 0.85; p < 0.01). Ca2+-uptake remained unaffected by previous IR. Though Ca\(^{2+}\)-release was delayed for ≥30 min of ischemia (p < 0.01), Ca\(^{2+}\) retention was highest in IR15/30 (RFU; IR0/30: 6.3 ± 3.6, IR 15/30 42.9 ± 5.0, IR30/30 15.9 ± 3.8, IR40/30 11.5 ± 6.6; p ≤ 0.01 for IR15/30 against all other groups).
Conclusions
Ischemia prolongation in IR injury gradually impaired SSM in terms of respiratory chain function and Ca\(^{2+}\)-homeostasis. Membrane hyperpolarization appears to be responsible for impaired Ca2+-cycling and ETC function. Ischemia time should be considered an important factor influencing IR experimental data on subsarcolemmal mitochondria. Periods of warm global ischemia should be minimized during cardiac surgery to avoid excessive damage to SSMs.