Angiotensin Blockade and General Anesthesia: So Little Known, So Far to Go

Preoperative angiotensin system inhibitor use attenuates heparin-induced hypotension in patients undergoing cardiac surgery

OBJECTIVE

Both angiotensin system inhibitor (ASI) use and heparin are associated with hypotension. This study attempted to determine whether preoperative ASI therapy affected the hemodynamic response to heparin administered to patients undergoing cardiac surgery.

DESIGN

Sixty-two patients undergoing elective cardiac surgery requiring full (300 units/kg) systemic heparinization were studied prospectively. Thirty-three patients were receiving preoperative ASI therapy, whereas 29 patients were not. Anesthetic technique and mechanical ventilation parameters were standardized. Hemodynamics were recorded at 3 time points: baseline (just before the administration of heparin), 1-minute post-heparin administration, and 4-minute post-heparin administration.

SETTING

Single university hospital.

PARTICIPANTS

Patients undergoing elective cardiac surgery.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

The 2 groups were similar regarding preoperative demographics and baseline hemodynamics. Baseline mean arterial pressure (MAP) in non-ASI patients was 82.0 mmHg, and it decreased significantly to 76.3 mmHg (1 min; p<0.05) and 70.7 mmHg (4 min; p<0.05) following heparin administration. MAP values in ASI patients were 81.9 mmHg, 81.8 mmHg, and 76.8 mmHg at baseline, 1-minute post-heparin, and 4-minute post-heparin administration, respectively (changes not significant).Within-group analysis revealed that non-ASI patients experienced significant decrease in MAP at 1-minute (-6.6%, p = 0.01) and 4-minute (-13.0%, p = 0.0011) post-heparin administration, whereas ASI patients did not (+1.9%, p = 0.52; -3.8%, p = 0.16, respectively). Between-group analysis revealed that differences in MAP values at 1 minute were significant (p = 0.03), whereas differences at 4 minutes were not significant (p = 0.05).

CONCLUSIONS

This prospective clinical study indicated that preoperative ASI therapy until the day before surgery may attenuate heparin-induced hypotension. Definitive mechanistic insight requires further clinical study.

Polypharmacy and perioperative medications in the elderly

Polypharmacy is a significant and complex problem affecting more than 40% of the geriatric population. Accurate medication histories may be difficult to obtain, but must include over-the-counter remedies as well as prescription. Physiologic changes occur with aging that predispose elderly patients to adverse drug events. At a minimum, medications with significant anticholinergic properties should be recognized and avoided in the perioperative period.