Therapeutic approaches to postoperative ischemia. The Study of Perioperative Ischemia Research Group

The Effects of Surgery on Plasma/Serum Vitamin C Concentrations: A Systematic Review and Meta-Analysis

Vitamin C (ascorbic acid) is a water soluble vitamin with an array of biological functions. A number of proposed factors contribute to the vitamin’s plasma bioavailability and ability to exert optimal functionality. The aim of this review was to systematically assess plasma vitamin C levels post-surgery compared with pre-surgery/ the magnitude and timeframe of potential changes in concentration. We searched the PUBMED, SCOPUS, SciSearch and the Cochrane Library databases between 1970 to April 2020 for relevant research papers. Prospective studies, control groups and true placebo groups derived from controlled trials that reported means and standard deviations of plasma vitamin C concentrations pre and post operatively were included into the meta-analysis. Data were grouped into short-term (≤7 days) and long term (> 7 days) post-operative follow-up. 23 of 31 studies involving 642 patients included in the systematic review were suitable for meta-analysis. Pooled data from the meta-analysis revealed a mean depletion of plasma vitamin C concentration of -17.99 µmol/L (39% depletion) (CI = -22.81, -13.17) (trial arms = 25, n = 565, p < 0.001) during the first post-operative week and -18.80 µmol/L (21% depletion) (-25.04, -12.56) (trial arms = 6, n = 166, p < 0.001) 2-3 months post-operatively. Subgroup analyses revealed that these depletions occurred following different types of surgery, however, high heterogeneity was observed amongst trials assessing concentration change during the first post-operative week. Overall, our results warrant larger, long term investigations of changes in post-operative plasma vitamin C concentrations and their potential effects on clinical symptomology.

Perioperative use of beta-blocker in noncardiac surgery: a multicenter educational intervention to achieve best practice guidelines

Perioperative cardiac ischemia and infarction are important causes of morbidity and mortality in patients undergoing noncardiac surgery. There is now significant evidence that the use of prophylactic beta-adrenergic antagonists among selected patients at risk for perioperative cardiovascular complications is associated with a reduction in myocardial ischemia and cardiac events. Furthermore, consensus guidelines have incorporated the findings of recent studies and provide recommendations for the appropriate utilization of beta-adrenergic antagonists among selected patients. Despite these guidelines, it is unknown to what extent these recommendations have become translated into clinical practice. After measuring perioperative beta-blocker use among participating hospitals within the New York Presbyterian Health Network, we developed a multicenter educational intervention to improve the overall utilization of beta-adrenergic prophylactic therapy in accordance with best practice guidelines. The literature supporting the development of this intervention is presented in this paper, along with the tools that are currently being used for decision support across an academic healthcare network.

Intercurrent drug therapy and perioperative cardiovascular mortality in elective and urgent/emergency surgical patientst

The Oxford Record Linkage Study (ORLS; an epidemiological database) was used to examine relationships between intercurrent cardiovascular drug therapy and cardiac death within 30 days of elective or emergency/urgent surgery under general anaesthesia. Cases identified from the ORLS were paired with matched control patients. Clinical details were obtained from the patients' medical notes. In elective surgical patients, there was no effect of beta-adrenoceptor or calcium entry channel blockade, diuretics or digoxin on cardiac death after adjusting for confounding variables. Use of nitrates was associated with an odds ratio of 4.79 [95% confidence interval (CI) 1.01-22.72] for cardiac death after adjustment for confounding by a history of angina and residual age difference. In emergency/urgent patients, there were significant univariate associations with cardiac death for intercurrent use of angiotensin converting enzyme (ACE) inhibitors (odds ratio 1.18) and diuretics (odds ratio 4.95; 95% CI 1.82-13.46). However, neither maintained significance after adjustment for the confounding effect of cardiac failure. We conclude that, with the possible exception of the use of nitrates in elective surgical patients, chronic intercurrent drug treatment alone does not significantly affect the odds of cardiac death within 30 days of surgery.

Postoperative prophylactic administration of beta-adrenergic blockers in patients at risk for myocardial ischemia

Perioperative myocardial ischemia (MI) is associated with postoperative cardiac morbidity. Postoperative sympatholysis may reduce the incidence of MI. This study evaluated such a reduction postoperatively with the administration of prophylactic beta-blockers in patients undergoing elective total knee arthroplasty with epidural anesthesia and postoperative epidural analgesia. One hundred seven patients were preoperatively randomized into two groups, control and beta-blockers, who received postoperative esmolol infusions on the day of surgery and metoprolol for the next 48 h to maintain a heart rate less than 80 bpm. Patients were followed for ST segment depression by using a Holter monitor and adverse cardiac outcomes. Postoperative electrocardiographic ischemia was significantly more prevalent in the control group compared with the beta-blocker group during esmolol blockade (0 of 52 vs 4 of 55; P = 0.04) and tended to be more common in the control group the next two days (8 of 55 vs 3 of 52; P = 0.135). In addition, the number of ischemic events (control, 50; beta-blockers, 16) and total ischemic time (control, 709 min; beta-blocker, 236 min) were also significantly different from the control group. Myocardial infarctions and cardiac events were more common in the control group, but these differences were not significant. Our results suggest that the use of prophylactic beta-blocker therapy may reduce the incidence of postoperative MI.

IMPLICATIONS

Prophylactic beta adrenergic blockade administered after elective total knee arthroplasty was associated with a reduced prevalence and duration of postoperative myocardial ischemia detected with Holter monitoring.

Role of the sodium-hydrogen exchanger in ischemia-reperfusion injury in diabetes

Ischemic heart disease is a significant problem in the diabetic population. Animal models of diabetes show a paradoxical resistance to ischemic challenge. The present treatise will discuss the mechanics involved and the central role that Na+-H+ exchanger plays in this response to ischemic-reperfusion injury.