Postoperative hypertension: A comparison of diltiazem, nifedipine, and nitroprusside

Calcium Antagonists for Perioperative Blood Pressure Control

Calcium entry blockers constitute three major classes of pharmacologic agents: phenylalkylamines (eg, verapa mil), benzothiazepines (eg, diltiazem), and dihydropyri dines (eg, nifedipine). The effectiveness of all types of calcium channel blockers in the prevention and treat ment of coronary artery disease as well as chronic and acute hypertension is undisputable. Their beneficial clinical effects may be due to peripheral and coronary vasodilatation, resulting in reduction in myocardial oxy gen consumption, and an increase in myocardial oxy gen supply in addition to their antispasmodic effect and the ability to prevent intracellular calcium overload. For the management of perioperative hypertension develop ing in patients undergoing cardiac or noncardiac sur gery, the dihydropyridines appear to be especially suit able. Intravenous (IV) formulations of nifedipine, nicardipine, and isradipine have been successfully used in this setting. At the present time, nicardipine is the most widely used IV dihydropyridine. This is due to its potent afterload-reducing activity and relatively short duration of action, although its effect may increase the longer the drug is being infused. The ideal drug for perioperative blood pressure control should be one with the pharmacodynamic profile of the vascular selec tive dihydropyridines, but with an ultrashort duration of action.

Diltiazem versus Amiodarone to Prevent Atrial Fibrillation in Coronary Surgery

The prophylactic effect of amiodarone on atrial fibrillation after coronary bypass grafting with extracorporeal circulation was compared with that of diltiazem in two groups of 60 patients each. Patients were monitored continuously for 8 days. The incidence of atrial fibrillation was recorded retrospectively in a control group of 60 patients who received our standard prophylactic regimen of an oral beta blocker. The incidence of postoperative atrial fibrillation was not significantly different in the two test groups: 11.7% for the amiodarone group and 10% for the diltiazem group. The incidence of atrial fibrillation in the control group was 23.3% and the differences were marginally significant when compared to the amiodarone ( p = 0.093) and diltiazem groups ( p = 0.050). The prophylactic use of diltiazem or amiodarone is feasible and safe for patients undergoing coronary bypass, with similar rates of atrial fibrillation.

Coronary and systemic hemodynamic effects of clevidipine, an ultra-short-acting calcium antagonist, for treatment of hypertension after coronary artery surgery

BACKGROUND

The aim was to evaluate the use of clevidipine, a new vascular selective, ultra-short-acting calcium antagonist for blood pressure control after coronary artery bypass grafting (CABG).

METHODS

The effects of clevidipine on central hemodynamics, myocardial blood flow and metabolism were studied at two different phases after CABG. In phase 1 (n=13), the hypertensive phase, the effects of clevidipine were compared to those of sodium nitroprusside (SNP) when used to control postoperative hypertension. In phase 2 (n=9), the normotensive phase, a clevidipine dose-response relationship was established.

RESULTS

At a target mean arterial pressure (MAP) of 75 mmHg, systemic vascular resistance (SVR) and heart rate (HR) were lower, preload, stroke volume (SV) and pulmonary vascular resistance (PVR) were higher, while there were no differences in myocardial lactate metabolism or oxygen extraction with clevidipine compared to SNP. In the normotensive phase, clevidipine induced a dose-dependent decrease in MAP (-19%), SVR (-27%) and PVR (-15%), accompanied by an increase in SV (10%), but no reflex increase in HR or changes in cardiac preload. Clevidipine caused a direct coronary vasodilation, as indicated by a decrease in myocardial oxygen extraction from 54% to 45%. Myocardial lactate metabolism was unaffected by clevidipine. The blood clearance of clevidipine was 0.05 l x min(-1) x kg(-1), the volume of distribution at steady state was 0.08 l x kg(-1) and the initial and terminal half-lives were <1 min and 4 min, respectively.

CONCLUSIONS

Clevidipine rapidly reduced MAP and induced a systemic, pulmonary and coronary vasodilation with no effect on venous capacitance vessels or HR. Clevidipine caused no adverse effects on myocardial lactate metabolism. Clevidipine thus appears suitable to control blood pressure after CABG.

Influence of Vasodilator Drugs on Perioperative Blood Pressure

Survey results are given of the incidence and the etiology of perioperative hypertension in patients sub jected to coronary artery surgery. Over the years, numer ous types of antihypertensives have been used for intravenous administration with the aim of preventing or treating perioperative hypertension. Nitrovasodilator compounds such as sodium nitroprusside and nitroglyc erin (NTG), a few calcium antagonists (nifedipine, nicar dipine and isradipine), the short-acting β-blocker esmo lol, clonidine, and the multifactorial compounds labetalol and ketanserin are discussed in detail. Perioperatively, there is an increasing level of plasma catecholamines, causing α-adrenoceptor stimulation. This indicates that α-adrenoceptor blockade with appropriate antagonists is a logical approach for the treatment of perioperative hypertension. For this reason, the multifactorial agent urapidil, which is an α-adrenoceptor blocker and a 5-HT1A agonist, is discussed extensively.

Immediate postoperative care of cardiac surgical patients

Anesthetic care of the cardiac surgery patient is a continuum, beginning with the preoperative visit and ending when the patient is ambulatory and breathing well on the postoperative floor. Anesthesiologists are well-suited to provide postoperative care because the respiratory and cardiovascular management techniques are an extension of OR management. Attention to details is as important in the ICU as in the OR and offers the opportunity to forestall or reduce morbidity.

A comparison of prostacyclin and sodium nitroprusside for the treatment of heart failure after cardiac surgery

OBJECTIVE

To study the effects of the two vasodilators, prostacyclin and sodium nitroprusside, on central hemodynamics in heart failure after cardiac surgery.

DESIGN

Randomized cross-over study.

SETTING

Multi-institutional university hospital.

PARTICIPANTS

Ten patients.

INCLUSION CRITERIA

cardiac index less than 2.5 L/min/m2; pulmonary capillary wedge pressure greater than 15 mmHg, systemic vascular resistance index greater than 2,500 dynes.s.cm-5/m2, and treatment with inotropic support. Five patients were treated with intra-aortic balloon counterpulsation.

INTERVENTIONS

After control measurements, mean arterial pressure was decreased by 10% to 20% with each vasodilator in each patient.

MEASUREMENTS AND RESULTS

Sodium nitroprusside induced decreases in mean pulmonary arterial pressure (-21%), pulmonary capillary wedge pressure (-29%), central venous pressure (-17%), and systemic vascular resistance (-25%), and increases in cardiac output (+7%) and stroke volume (+6%) compared with control. Prostacyclin decreased mean pulmonary arterial pressure (-14%), pulmonary capillary wedge pressure (-19%), central venous pressure (-7%), and systemic (-40%) and pulmonary (-25%) vascular resistances, whereas cardiac output (+25%) and stroke volume (+22%) increased compared with control. Prostacyclin, compared with sodium nitroprusside, induced a more pronounced increase in cardiac output and stroke volume, associated with less pronounced decreases in cardiac filling pressures and more profound decreases in systemic and pulmonary vascular resistances.

CONCLUSION

Prostacyclin appears to be a useful agent, superior to sodium nitroprusside, in the treatment of postoperative heart failure in patients with normal or mildly elevated cardiac filling pressures, where vasodilator treatment is indicated.

Sodium nitroprusside: twenty years and counting

SNP remains an effective, reliable, and commonly used drug for the rapid reduction of significant arterial hypertension regardless of the etiology, for afterload reduction in the face of low CO when blood volume is normal or increased, and for intraoperative induced hypotension. After establishing indwelling arterial monitoring, an initial infusion rate of 0.3-0.5 micrograms.kg-1.min-1 is begun with titration as needed up to 2.0 micrograms.kg-1.min-1. Higher rates for brief periods of time (10 min) are acceptable. The use of alternative drugs to reduce the dose or shorten the duration of infusion should be considered when the 2.0 micrograms.kg-1.min-1 range is exceeded (Table 1). SNP should not be used by individuals unfamiliar with its potency and metabolic pathways, as the many reports of adverse reactions testify. Careful attention to infusion rates, particularly in patients at risk for depleted thiosulfate stores, is mandatory, and the use of other drugs in conjunction with or instead of SNP should always be considered. As with many therapeutic interventions, SNP requires careful administration to appropriately selected patients by a clinician who knows its inherent hazards. Despite its toxicity, SNP is popular because it is often the most (in some cases, the only) effective drug in some difficult clinical circumstances.

Intranasal delivery of cardiovascular agents: an innovative approach to cardiovascular pharmacotherapy

The intranasal administration of drugs has long been used for the topical treatment of various nasal disorders. Many features of the intranasal mucosa also make it useful for delivery of systemically active agents. It has been shown that intranasal drug administration can provide plasma drug levels similar to those observed with comparable doses of parenteral drugs. The feasibility of intranasal administration of propranolol, nifedipine, and nitroglycerin has been investigated in several small clinical studies. Intranasal propranolol has been shown to improve exercise tolerance in patients with angina pectoris. Intranasal nifedipine has been used to treat patients with perioperative hypertension and hypertensive crisis. Intranasal administration of nitroglycerin was shown to blunt the hypertensive response to endotracheal intubation. These studies and others suggest that intranasal delivery of cardiovascular drug treatment could be used in those clinical situations where a rapid or intermittent drug effect is desired and can potentially serve as an alternative to parenteral drug administration.

Vasodilators during cerebral aneurysm surgery

The objective of this review is to review the anaesthetic implications of vasoactive compounds particularly with regard to the cerebral circulation and their clinical importance for the practicing anaesthetist. Material was selected on the basis of validity and application to clinical practice and animal studies were selected only if human studies were lacking. Hypotensive drugs have been used to induce hypotension and in the treatment of intraoperative hypertension during cerebral aneurysm surgery. After subarachnoid haemorrhage, cerebral blood flow is reduced and cerebral vasoreactivity is disturbed which may lead to brain ischaemia. Also, cerebral arterial vasospasm decreases cerebral blood flow, and may lead to delayed ischaemic brain damage which is a major problem after subarachnoid haemorrhage. Recently, the use of induced hypotension has decreased although it is still useful in patients with intraoperative aneurysm rupture, giant cerebral aneurysm, fragile aneurysms and multiple cerebral aneurysms. In this review, a variety of vasodilating agents, prostaglandin E1, sodium nitroprusside, nitroglycerin, trimetaphan, adenosine, calcium antagonists, and inhalational anaesthetics, are discussed for their clinical usefulness. Sodium nitroprusside, nitroglycerin and isoflurane are the drugs of choice for induced hypotension. Prostaglandin E1, nicardipine and nitroglycerin have the advantage that they do not alter carbon dioxide reactivity. Local cerebral blood flow is increased with nitroglycerin, decreased with trimetaphan and unchanged with prostaglandin E1. Intraoperative hypertension is a dangerous complication occurring during cerebral aneurysm surgery, but its treatment in association with subarachnoid haemorrhage is complicated in cases of cerebral arterial vasospasm because fluctuations in cerebral blood flow may be exacerbated. Hypertension should be treated immediately to reduce the risk of rebleeding and intraoperative aneurysmal rupture and the choice of drugs is discussed. Although the use of induced hypotension has declined, the control of arterial blood pressure with vasoactive drugs to reduce the risk of intraoperative cerebral aneurysm rupture is a useful technique. Intraoperative hypertension should be treated immediately but the cerebral vascular effects of each vasodilator should be understood before their use as hypotensive agents.

Closed loop control of arterial hypertension following intracranial surgery using sodium nitroprusside. A comparison of intra-operative halothane or isoflurane

Forty patients were chosen at random to receive halothane or isoflurane anaesthesia during craniotomy and a comparison of the postoperative hypertensive response was made using a microcomputer-based closed-loop arterial pressure control system with sodium nitroprusside to control and assess arterial pressure during the first 6 postoperative hours. A desired target systolic pressure was chosen for each patient and the frequency of hypertension, sodium nitroprusside requirements and quality of arterial pressure control were compared between the two groups. Thirty-five patients required sodium nitroprusside. The halothane group required a median dose of 15.2 mg (range 0-72) compared to 3.4 mg (range 0-87) in the isoflurane group. This difference is not statistically significant. Quality of arterial pressure control was satisfactory in both groups. In conclusion, arterial hypertension occurs frequently following intracranial surgery and is uninfluenced by the choice of halothane or isoflurane intra-operatively. This closed-loop arterial pressure control system functioned safely and effectively in this context.

Calcium-channel blockers and anaesthesia

Verapamil was the first calcium-channel blocker (CCB). It has been used since 1962 in Europe then in Japan for its antiarrhythmic and coronary vasodilator effects. The CCB have become prominent cardiovascular drugs during the last 15 years. Many experimental and clinical studies have defined their mechanism of action, the effects of new drugs in this therapeutic class, and their indications and interactions with other drugs. Due to the large number of patients treated with CCB it is important for the anaesthetist to know the general and specific problems involved during the perioperative period, the interactions with anaesthetics and the practical use of these drugs.