Antimicrobial Prophylaxis Redosing Reduces Surgical Site Infection Risk in Prolonged Duration Surgery Irrespective of Its Timing.

BACKGROUND: Long-duration surgery requires repeated administration of antimicrobial prophylaxis (amp). Amp "redosing" reduces incidence of surgical site infections (SSI) but is frequently omitted. Clinical relevance of redosing timing needs to be investigated. Here, we evaluated the effects of compliance with amp redosing and its timing on SSI incidence in prolonged duration surgery. METHODS: Data from >9000 patients undergoing visceral, trauma, or vascular surgery with elective or emergency treatment in two tertiary referral Swiss hospitals were analyzed. All patients had to receive amp preoperatively and redosing, if indicated. Antibiotics used were cefuroxime (1.5 or 3 g, if weight >80 kg), or cefuroxime and metronidazole (1.5 and 0.5 g, or 3 and 1 g doses, if weight >80 kg). Alternatively, in cases of known or suspected allergies, vancomycin (1 g), gentamicin (4 mg/Kg), and metronidazole or clindamycin (300 mg) with or without ciprofloxacin (400 mg) were used. Association of defined parameters, including wound class, ASA scores, and duration of operation, with SSI incidence was explored. RESULTS: In the whole cohort, SSI incidence significantly correlated with duration of surgery (ρ = 0.73, p = 0.031). In 593 patients undergoing >240 min long interventions, duration of surgery was the only parameter significantly (p < 0.001) associated with increased SSI risk, whereas wound class, ASA scores, treatment areas, and emergency versus elective hospital entry were not. Redosing significantly reduced SSI incidence as shown by multivariate analysis (OR 0.60, 95% CI 0.37-0.96, p = 0.034), but exact timing had no significant impact. CONCLUSIONS: Long-duration surgery associates with higher SSI incidence. Irrespective of its exact timing, amp redosing significantly decreases SSI risk.

Contractile function is preserved in unloaded hearts despite atrophic remodeling.

OBJECTIVE: Recent studies have shown that mechanically unloading a failing heart may induce reverse remodeling and functional improvement. However, these benefits may be balanced by an unloading-related remodeling including myocardial atrophy that might lead to decrease in function. Using a model of heterotopic heart transplantation, we aimed to characterize the myocardial changes induced by long-term unloading. MATERIAL AND METHODS: Macroscopic as well as cellular and functional changes were followed in normal hearts unloaded for a 3-month period. Microscopic parameters were evaluated with stereologic methodology. Myocardial contractile function was quantified with a Langendorff isolated, perfused heart technique. RESULTS: Atrophy was macroscopically obvious and accompanied by a 67% reduction of the myocyte volume and a 43% reduction of the interstitial tissue volume, thus accounting for a shift of the myocyte/connective tissue ratio in favor of noncontractile tissue. The absolute number of cardiomyocyte nuclei decreased from 64.7 +/- 5.1 x 10(7) in controls to 22.6 +/- 3.7 x 10(7) (30 days) and 21.6 +/- 3.1 x 10(7) (90 days) after unloading (P < .05). The numeric nucleic density in the unloaded myocardium, as well as the mean cardiomyocyte volume per cardiomyocyte nucleus, remained constant throughout the 90 days of observation. Functional data indicated an increase in ventricular stiffness, although contractile function was preserved, as confirmed by unaltered maximal developed pressure and increased contractility (maximum rate of left ventricular pressure development) and relaxation (minimum rate of left ventricular pressure development). CONCLUSION: Atrophic remodeling involves both the myocyte and interstitial tissue compartment. These data suggest that although there is decreased myocardial volume and increased stiffness, contractile capacity is preserved in the long-term unloaded heart.