Calcium-channel blockers and anaesthesia

Continuing versus withholding angiotensin receptor blocker (ARB)/calcium channel blocker (CCB) combination tablets during perioperative periods in patients undergoing minor surgery: a single-blinded randomized controlled trial

Purpose

This trial was conducted to compare effects of continuing versus withholding single-pill combination tablets consisting of angiotensin receptor blockers (ARBs) and calcium channel blockers (CCBs) on perioperative hemodynamics and clinical outcomes.

Methods

Patients undergoing minor abdominal or urological surgery (n = 106) were randomly assigned to Group C, in which ARB/CCB combination tablets were continued until surgery, or Group W, in which they were withheld within 24 h of surgery. Perioperative hemodynamics and clinical outcomes were compared between the Groups.

Results

The incidence of hypotension during anesthesia requiring repeated treatment with vasoconstrictors was higher in Group C than Group W (p = 0.0052). Blood pressure during anesthesia was generally lower in Group C than Group W (p < 0.05) despite significantly more doses of ephedrine and phenylephrine administrated in Group C (p = 0.0246 and p = 0.0327, respectively). The incidence of postoperative hypertension did not differ between Groups (p = 0.3793). Estimated glomerular filtration rate (eGFR) on the preoperative day did not differ between Groups (p = 0.7045), while eGFR was slightly lower in Group C than Group W on the first and third postoperative days (p = 0.0400 and p = 0.0088, respectively), although clinically relevant acute kidney injury did not develop.

Conclusions

Continuing ARB/CCB combination tablets preoperatively in patients undergoing minor surgery increased the incidence of hypotension during anesthesia, increased requirements of vasoconstrictors to treat hypotension, and might deteriorate postoperative renal function, albeit slightly. These results suggest that withholding ARB/CCB tablets preoperatively is preferable to continuing them.

Clinical trial registration

This trial is registered with the Japan Registry of Clinical Trials (jRCT) at Japanese Ministry of Health, Labour, and Welfare (Trial ID: jRCT1031190027).

Optimal perioperative management of arterial blood pressure

Perioperative blood pressure management is a key factor of patient care for anesthetists, as perioperative hemodynamic instability is associated with cardiovascular complications. Hypertension is an independent predictive factor of cardiac adverse events in noncardiac surgery. Intraoperative hypotension is one of the most encountered factors associated with death related to anesthesia. In the preoperative setting, the majority of antihypertensive medications should be continued until surgery. Only renin-angiotensin system antagonists may be stopped. Hypertension, especially in the case of mild to moderate hypertension, is not a cause for delaying surgery. During the intraoperative period, anesthesia leads to hypotension. Hypotension episodes should be promptly treated by intravenous vasopressors, and according to their etiology. In the postoperative setting, hypertension predominates. Continuation of antihypertensive medications and postoperative care may be insufficient. In these cases, intravenous antihypertensive treatments are used to control blood pressure elevation.

Nicardipine: applications in anesthesia practice

Nicardipine is the first intravenously administered dihydropyridine calcium channel blocker. Its primary physiologic actions include vasodilatation with limited effects on the inotropic and dromotropic function of the myocardium. Nicardipine has been used to control blood pressure intraoperatively in response to tracheal intubation and in the postoperative period. Various patient populations have been included such as major vascular and cardiovascular surgery. It has also been used as an agent for controlled hypotension. Preliminary experience suggests that nicardipine provides safe and effective control of perioperative blood pressure. The basic pharmacology and physiology of the most recently released calcium channel antagonist, nicardipine, is reviewed, and its applications in clinical anesthesia and interaction with other anesthetic drugs are discussed.

Systemic vasomotor interaction between nicardipine and hypocapnic alkalosis in man

The effects of hypocapnic alkalosis on the vasodilating action of nicardipine were studied in 6 patients after cerebral arterial aneurysm surgery. Each patient served as his/her own control during the 6 steps of the study. T0: baseline; T1: hypocapnic alkalosis alone (PaCO2: 3.5 kPa); T2: hypocapnic alkalosis and bolus injection of nicardipine (30 micrograms.kg-1 i.v.); T3: hypocapnic alkalosis and continuous 60 min infusion of nicardipine (0.5 microgram.kg-1.min-1), T4: determination of the infusion rate required to neutralize the effect of hypocapnic alkalosis; T5: same continuous dose of nicardipine as in T4 but reversal of hypocapnic alkalosis. Hypocapnic alkalosis alone caused a significant increase in the systemic vascular resistance index by 20% (T1). The bolus injection of nicardipine reversed this first effect (T2). The continuous infusion of nicardipine in T3 was insufficient to cancel the haemodynamic effect of hypocapnic alkalosis. During T4 the plasma levels required to neutralize completely the effect of hypocapnic alkalosis were twice those at T3. Normalization of the PaCO2 in step T5 induced a significant fall in the systemic vascular resistance index by 27.5% as compared with T0. In this study hypocapnic alkalosis modified the relationship between plasma levels of nicardipine and its expected vasoactive effects. This interaction was reversible.