Intra-operative tachycardia is not associated with a composite of myocardial injury and mortality after noncardiac surgery: A retrospective cohort analysis.

BACKGROUND: Myocardial injury after noncardiac surgery (MINS) is a major contributor to peri-operative morbidity and mortality with a reported incidence of about 8%. Tachycardia increases myocardial oxygen demand, and decreases oxygen supply, and is therefore a potential cause of MINS. OBJECTIVE: We tested the hypothesis that there is an association between intra-operative area above a heart rate (HR) of 90 bpm and a composite of MINS and in-hospital all-cause mortality. DESIGN: Retrospective analyses. SETTING: Major tertiary care hospital, Cleveland, USA. PATIENTS: Adults having elective or nonelective noncardiac surgery and scheduled troponin monitoring during the first 3 postoperative days between 2010 and 2015. MAIN OUTCOME MEASURES: All-or-none composite of myocardial injury (MINS), defined by a peak postoperative generation 4 troponin T concentration at least 0.03 ng ml, and in-hospital all-cause mortality. RESULTS: Among 2652 eligible patients, 123 (4.6%) experienced MINS within 7 days after surgery and 6 (0.2%) died before discharge. Intra-operative area above HR more than 90 bpm was not associated with the all-or-none composite of MINS and in-hospital mortality, with an estimated odds ratio (95% confidence interval) of 0.99 (0.97 to 1.01) per 1 h bpm increase in area above HR more than 90 bpm. Secondary outcomes were also unrelated to the composite, with estimated odds ratios (98.3% confidence interval) of 0.99 (0.98 to 1.00) for area above HR more than 80, 0.98 (0.92 to 1.04) for area above HR more than 100 bpm, and 0.96 (0.88 to 1.05) for maximum HR. CONCLUSION: There was no apparent association between various measures of tachycardia and a composite of MINS and death, a result that contradicts previously reported associations between other measures of intra-operative tachycardia and MINS/mortality.

Postoperative Hypotension and Surgical Site Infections After Colorectal Surgery: A Retrospective Cohort Study.

BACKGROUND: Hypotension compromises local tissue perfusion, thereby reducing tissue oxygenation. Hypotension might thus be expected to promote infection. Hypotension on surgical wards, while usually less severe than intraoperative hypotension, is common and often prolonged. In this retrospective cohort study, we tested the hypotheses that there is an association between surgical site infections and low postoperative time-weighted average mean arterial pressure and/or postoperative minimum mean arterial pressure. METHODS: We considered patients who had colorectal surgery lasting ≥1 hour at the Cleveland Clinic between 2009 and 2013. We defined blood pressure exposures as time-weighted average (primary) and minimum mean arterial pressure (secondary) within 72 hours after surgery. We assessed associations between continuous blood pressure exposures with a composite of deep and superficial surgical site infection using separate severity-weighted average relative effect generalized estimating equations models, each using an unstructured correlation structure and adjusting for potentially confounding variables. RESULTS: A total of 5896 patients were eligible for analysis. Time-weighted mean arterial pressure and surgical site infection were not significantly associated, with an estimated odds ratio (95% CI) of 1.03 (0.99-1.08) for a 5-mm Hg decrease (P = .16). However, there was a significant inverse association between minimum postoperative mean arterial pressure and infection, with an estimated odds ratio of 1.08 (1.03-1.12) per 5-mm Hg decrease (P = .001). CONCLUSIONS: Postoperative time-weighted mean arterial pressure was not associated with surgical site infection, but lowest postoperative mean arterial pressure was. Whether the relationship is causal remains to be determined.

Association Between Intraoperative Low Blood Pressure and Development of Surgical Site Infection After Colorectal Surgery: A Retrospective Cohort Study.

OBJECTIVE: We tested the primary hypothesis that surgical site infections (SSIs) are more common in patients who had longer periods of intraoperative low blood pressure. Our secondary hypothesis was that hospitalization is prolonged in patients experiencing longer periods of critically low systolic blood pressure (SBP) and/or mean arterial pressure (MAP). BACKGROUND: Hypotension compromises local tissue perfusion, thereby reducing tissue oxygenation. Hypotension might thus be expected to promote infection, but the extent to which low blood pressure contributes remains unclear. METHODS: We considered patients who had colorectal surgery lasting at least 1 hour at the Cleveland Clinic between 2009 and 2013. The duration of hypotensive exposure and development of SSI was assessed with logistic regression; the association between hypotensive exposure and duration of hospitalization was assessed with Cox proportional hazard regression. RESULTS: A total of 2521 patients were eligible for analysis. There was no adjusted association between SBP hypotension < 80 mm Hg and SSI, with an estimated odds ratio (95% confidence interval) of 0.97 (0.81, 1.17) per 5-minute increase in SBP hypotension (P = 0.54). There was also no adjusted association between MAP hypotension time and SSI, with estimated odds ratio of 0.97 (0.81, 1.17) for a 5-minute increase in MAP hypotension < 55 mm Hg time (P = 0.71). There was no association between duration of hypotension and time to discharge. CONCLUSIONS: Intraoperative hypotension does not seem to be a clinically important predictor of SSI after colorectal surgery, probably because the outcomes are overwhelmingly determined by other baseline and surgical factors-and perhaps postoperative hypotension.