Acute hypertension immediately after coronary artery surgery

Pharmacological Review of Postoperative Hypertension

Postoperative hypertension is an acute, transient increase in blood pressure that develops within 30 to 90 minutes following a surgical procedure and typically lasts for 4 to 8 hours after surgery. It is defined as a systolic blood pressure greater than 160 mm Hg or a diastolic blood pressure greater than 90 mm Hg. The increase in blood pressure is primarily due to increased systemic vascular resistance brought about by reflex changes in humoral factors, including increased levels of catecholamines, renin, and serotonin as well as alterations in baroreceptor function and carotid reflexes. Potential complications of untreated postoperative hypertension include depressed left ventricular performance, increased myocardial oxygen demand resulting in ischemic episodes, cerebrovascular accidents, arrhythmias, and suture line disruption and bleeding. Despite longstanding recognition that high blood pressure is a frequent complication after surgery, formal guidelines for the treatment of postoperative hypertension have not been developed. Postoperative hypertension is a pathophysiological state that requires rapid assessment and appropriate treatment. Several pharmacologic agents are available to achieve and maintain normotension after surgery, including nitrovasodilators (nitroglycerin and sodium nitroprusside), adrenergic blocking agents, and dihydroperidine calcium channel antagonists. Angiotensin-converting enzyme inhibitors and fenoldopam also have been used. Each has its own distinct mechanism of action and adverse effect profile. In cardiac surgery, nicardipine is as effective as nitrovasodilators and offers coronary selectivity. In patients who are hypertensive after neurosurgical procedures, avoid direct-acting vasodilators, which may exacerbate increased intracranial pressure; β-adrenergic receptor antagonists and ACEIs are the preferred agents in these patients. More data are needed to define roles and benefits of fenoldopam in managing postoperative hypertension.

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.

Nitroglycerin and sodium nitroprusside: potential contributors to postoperative bleeding?

Postoperative bleeding is common in patients undergoing cardiac surgery with cardiopulmonary bypass. Most cases of severe postoperative bleeding not due to incomplete surgical hemostasis are related to acquired transient platelet dysfunction mediated by platelet activation during contact with the synthetic surfaces of the cardiopulmonary bypass equipment. Antihypertensive agents nitroglycerin and sodium nitroprusside have been shown to have platelet inhibitory properties, yet the clinical consequence in terms of postoperative bleeding has been little studied. Knowing that cardiopulmonary bypass causes platelet dysfunction, it is prudent for physicians to be aware of the additional platelet inhibition caused by these commonly used antihypertensive agents.

Clevidipine in the treatment of perioperative hypertension: assessing safety events in the ECLIPSE trials

Clevidipine is an arterial, selective, dihydropyridine calcium channel blocker with an ultrashort half-life. In this prospective, randomized, open-label, parallel-comparison trial series, the safety and efficacy of intravenous clevidipine with nitroglycerin, sodium nitroprusside and nicardipine in hypertensive patients during cardiac surgery were compared. No differences in the incidences of myocardial infarction, stroke or renal dysfunction were observed between treatment groups. Mortality was similar between the clevidipine-nitrogylcerine- and clevidipine-nicardipine-treated groups, whereas mortality appeared to be greater in the sodium nitroprusside group compared to clevidipine (p = 0.04 in a univariant analysis). Clevidipine was significantly more effective in blood pressure control compared with nitroglycerin (p = 0.0006) or sodium nitroprusside (p = 0.003) and was associated with fewer blood pressure excursions compared with nicardipine as a predetermined blood pressure range was narrowed.

The ECLIPSE trials: comparative studies of clevidipine to nitroglycerin, sodium nitroprusside, and nicardipine for acute hypertension treatment in cardiac surgery patients

BACKGROUND

Acute hypertension during cardiac surgery can be difficult to manage and may adversely affect patient outcomes. Clevidipine is a novel, rapidly acting dihydropyridine L-type calcium channel blocker with an ultrashort half-life that decreases arterial blood pressure (BP). The Evaluation of CLevidipine In the Perioperative Treatment of Hypertension Assessing Safety Events trial (ECLIPSE) was performed to compare the safety and efficacy of clevidipine (CLV) with nitroglycerin (NTG), sodium nitroprusside (SNP), and nicardipine (NIC) in the treatment of perioperative acute hypertension in patients undergoing cardiac surgery.

METHODS

We analyzed data from three prospective, randomized, open-label, parallel comparison studies of CLV to NTG or SNP perioperatively, or NIC postoperatively in patients undergoing cardiac surgery at 61 medical centers. Of the 1964 patients enrolled, 1512 met postrandomization inclusion criteria of requiring acute treatment of hypertension based on clinical criteria. The patients were randomized 1:1 for each of the three parallel comparator treatment groups. The primary outcome was the incidence of death, myocardial infarction, stroke or renal dysfunction at 30 days. Adequacy and precision of BP control was evaluated and is reported as a secondary outcome.

RESULTS

There was no difference in the incidence of myocardial infarction, stroke or renal dysfunction for CLV-treated patients compared with the other treatment groups. There was no difference in mortality rates between the CLV, NTG or NIC groups. Mortality was significantly higher, though, for SNP-treated patients compared with CLV-treated patients (P=0.04). CLV was more effective compared with NTG (P=0.0006) or SNP (P=0.003) in maintaining BP within the prespecified BP range. CLV was equivalent to NIC in keeping patients within a prespecified BP range; however, when BP range was narrowed, CLV was associated with fewer BP excursions beyond these BP limits compared with NIC.

CONCLUSIONS

CLV is a safe and effective treatment for acute hypertension in patients undergoing cardiac surgery.

Exploring an Optimum Intra/Postoperative Management Strategy for Acute Hypertension in the Cardiac Surgery Patient

An estimated 50% of patients undergoing routine cardiac surgery require intravenous antihypertensive therapy to manage life-threatening arterial bleeding, myocardial ischemia, or cardiac failure in the perioperative period. Managing hypertension in this setting can be challenging because of the need to reduce blood pressure while maintaining adequate end organ perfusion. Hypotensive episodes can increase the risk of cardiac complications and end organ hypoperfusion, particularly in patients whose underlying cardiovascular disease has altered autoregulation of blood flow. To decrease the risk of hypertensive or hypotensive episodes, blood pressure is monitored continuously, and short-acting intravenous antihypertensive agents are administered in an effort to target a mean arterial pressure generally within 20% of the patient's baseline value. Efforts to optimize end organ perfusion and avoid recognized adverse drug effects may influence the choice of antihypertensive agents. The ideal agent for postoperative hypertension should have a rapid onset of action, be highly vascular selective, and be rapidly reversible. In addition, it should be safe, with little risk of overshoot hypotension or adverse drug reaction. Precise management of arterial pressure in the perioperative period has the potential to improve clinical outcome by avoiding hypotensive episodes, ensuring adequate end organ perfusion, decreasing the risk of adverse drug effects, and serving as a bridge to definitive long-term therapy for essential hypertension.

Comparison of clevidipine with sodium nitroprusside in the control of blood pressure after coronary artery surgery

BACKGROUND AND OBJECTIVE

We set out to compare the efficacy of clevidipine and sodium nitroprusside infusions in the control of blood pressure and the haemodynamic changes they produce in hypertensive patients after operation for elective coronary bypass grafting.

METHODS

Thirty patients were randomly allocated to receive either clevidipine or sodium nitroprusside after their mean arterial pressure (MAP) had reached > 90 mmHg for at least 10 min in the postoperative period. The MAP was continuously measured and related to time. Thus, the efficacy of the drugs in controlling arterial pressure could be inversely related to the total area under the MAP-time curve outside a target MAP range of 70-80 mmHg normalized per hour (AUC(MAP) mmHg min h(-1)). Haemodynamic variables and the number of dose-rate adjustments required to maintain MAP were also studied.

RESULTS

There was no statistically significant difference in the efficacy (AUC(MAP) mmHg min h(-1)) of clevidipine (106 +/- 25 mmHg min h(-1)) compared with sodium nitroprusside (101 +/- 28 mmHg min h(-1)). Nor was any significant difference found in the total number of dose adjustments required to control MAP within the target range. The heart rate in patients receiving clevidipine increased less than in those given sodium nitroprusside. Stroke volume, central venous pressure and pulmonary artery pressure were significantly reduced upon administration of sodium nitroprusside but not of clevidipine.

CONCLUSIONS

There was no significant difference between clevidipine and sodium nitroprusside in their efficacy in controlling MAP. The haemodynamic changes, including tachycardia, were less pronounced with clevidipine than with sodium nitroprusside.

[Comparison of nicardipine and isradipine in hypertension following coronary artery bypass graft]

OBJECTIVE

Compare the efficacy of isradipine to that of nicardipine for the control of arterial hypertension following coronary artery bypass graft (CABG).

STUDY DESIGN

Clinical prospective, randomised study.

MATERIAL AND METHODS

40 patients ASA II or III, mean age 66 +/- 8 years, scheduled for elective CABG were included. If the mean arterial pressure (MAP) was > or = 100 mmHg within the first six post operative hours, the patients were included and randomly attributed to either one of the 2 groups: Gr I (n = 20) received nicardipine, Gr II (n = 20) received isradipine in bolus then in continuous perfusion. HR, MAP, MPAP, CVP, PCWP, CI, SVRI, PVRI and SVI were recorded at: T0 before administration of drugs, T1 = 2 min after the first bolus. T2 when MAP reached 85 +/- 5 mmHg. T3, T4, T5, T6, T7 and T8 at 5, 10, 30, 60, 90 and 120 min after the continuous perfusion. T9 before stopping the perfusion.

RESULTS

No significant changes in HR, CVP, PCWP, MPAP or PVRI at any time in both groups. Significant increase in CI at T2 in both groups. Reduction of MAP at T2 was more important (-27%) in Gr I compared to that in Gr II (-22%). This was mainly due to a significant decrease in SVRI.

CONCLUSION

Isradipine is effective in the treatment of arterial hypertension following CABG. However there is not any significant beneficial effect of isradipine over nicardipine.

Pharmacokinetics and pulmonary extraction of clevidipine, a new vasodilating ultrashort-acting dihydropyridine, during cardiopulmonary bypass

Clevidipine is a new vascular-selective, calcium channel antagonist of the dihydropyridine type with an ester side chain susceptible to esterase metabolism. In healthy volunteers, it has high clearance (0.069 litres min-1 kg-1) with a small volume of distribution at steady state (0.19 litres kg-1). The half-lives of the two initial rapid phases, accounting for approximately 95% of the area under the curve after an i.v. bolus, are 0.7 and 2.3 min, respectively. The aims of this study were to determine the pharmacokinetics and the pulmonary extraction ratio of clevidipine in patients undergoing cardiac surgery. Seventeen patients received clevidipine as an i.v. infusion before cardiopulmonary bypass (CPB), and eight of these patients were also given clevidipine during hypothermic CPB. Mixed venous and arterial blood samples were taken for pharmacokinetic analysis and calculation of pulmonary extraction ratio. A two-compartment pharmacokinetic model with zero-order input was used to describe the pharmacokinetics of clevidipine before and during CPB. Virtually identical concentrations in mixed venous and arterial blood suggest negligible pulmonary metabolism of clevidipine. The total blood clearance of clevidipine is extremely high (0.055 litres min-1 kg-1). During CPB, clearance of clevidipine was significantly reduced, to 0.03 litres min-1 kg-1 (P < 0.005), probably as a consequence of reduced body temperature.

Treatment of hypertension in the perioperative patient

OBJECTIVE

To review studies and drug therapy relating to the treatment of hypertension in perioperative patients.

DATA SOURCES

Articles were selected from a MEDLINE search (1966-August 1998), and several textbooks on hypertension and surgery were reviewed. In addition, bibliographies of all articles and textbook chapters were studied for articles not found in the computerized searches.

STUDY SELECTION

Clinical studies involving hypertension in the perioperative setting were included. The initial search was limited to studies conducted in humans and published in English.

DATA EXTRACTION

Information regarding drug therapy was reviewed and guidelines were constructed for managing surgical patients with acute blood pressure elevations.

DATA SYNTHESIS

Although nitroprusside and nitroglycerin, with their short onset of action and duration of effect, are indicated for hypertensive emergencies, a variety of agents are available for hypertensive urgencies. An algorithm that can be used as a template for the development of intrainstitutional guidelines is provided.

CONCLUSIONS

Due to the scarcity of comparative trials, decisions involving agents for the treatment of perioperative hypertension must often be made based on combined efficacy, toxicity, cost, and convenience considerations.

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.

Effects of adenosine infusion on systolic and diastolic left ventricular function after coronary artery bypass surgery: evaluation by computer-assisted quantitative 2-D and Doppler echocardiography

The effects of adenosine on central hemodynamics, ST-segment changes, and left ventricular (LV) systolic and diastolic function, determined by transesophageal 2-D and Doppler echocardiography, were investigated in 20 patients shortly after coronary surgery. After control measurements, adenosine was infused at incremental infusion rates (30, 60, and 120 micrograms.kg-1.min-1). Adenosine caused dose-dependent increases in heart rate (68.0 +/- 11.2-74.0 +/- 15.7 bpm), cardiac output (3.23 +/- 0.76-4.17 +/- 0.67 L/min), and stroke volume (48.8 +/- 12.5-56.7 L/min), and stroke volume (48.8 +/- 12.5-56.7 mL), decreases in arterial pressure (84.8 +/- 16.6-63.3 +/- 15.2 mm Hg), and systemic and pulmonary vascular resistances (1994 +/- 510-1106 +/- 309 and 209 +/- 54-116 +/- 58 dyne.s.cm-5, respectively), but no changes in cardiac filling pressures. The mean ST segment was slightly but significantly depressed by adenosine (from 0.003 to 0.019 mV). Analysis of LV wall motion showed that adenosine caused no changes in the global area ejection fraction (GAEF), the segmental area ejection fraction (SAEF), or in the SAEF/GAEF ratio, indicating that no regional wall motion abnormalities appeared. Maximum early and late diastolic flow rates (Emax, Amax), determined by mitral Doppler analysis, increased (from 30.1 +/- 14.8 to 40.1 +/- 24.1 and from 37.8 +/- 15.7 to 46.4 +/- 31.3 cm/s, respectively), as did the deceleration slope of the early diastolic filling (from -151 +/- 67 to -210 +/- 107 cm/s-2), whereas no changes were found in the ratio between Emax and Amax, the deceleration time of early diastolic filling, or the velocity time integrals of early or late diastolic filling.(ABSTRACT TRUNCATED AT 250 WORDS)

Thoracic epidural analgesia in aortocoronary bypass surgery. I: Haemodynamic effects

Tachycardia and hypertension may cause myocardial ischaemia in patients with coronary heart disease going through major surgery. Thoracic epidural analgesia (TEA) has been reported to be beneficial in this situation. The haemodynamic effects of TEA in aortocoronary bypass surgery were investigated in 30 male patients < 65 years old and with ejection fraction > 0.5. They were randomized into 3 groups: the high dose fentanyl (HF) group receiving high-dose fentanyl (55 micrograms.kg-1) anaesthesia, the HF+TEA group receiving the same fentanyl dose+TEA with 10 ml bupivacaine 5 mg.ml-1 followed by 4 ml every hour, and the low dose fentanyl (LF) + TEA group receiving low-dose fentanyl (15 micrograms.kg-1) anaesthesia+TEA. Haemodynamic parameters, the use of vasoactive and inotropic drugs and fluid balance were followed during the operation and for 20 h postoperatively. Before bypass the only significant difference between groups was a higher mean pulmonary arterial pressure in the HF+TEA group and a lower systemic vascular resistance (SVR) in the LF+TEA group, both compared to the HF group. 89% of epidural group patients needed small doses of ephedrine whereas more HF group patients were given nitroglycerine. During bypass SVR and mean arterial pressure (MAP) were significantly higher and pump flow lower in the HF group compared to the LF+TEA group. More ketanserin to HF group patients and methoxamine to epidural group patients were given. After bypass heart rate increased in all groups. Lower MAP 0.5 h after bypass and higher filling pressures in the early post bypass period in the epidural groups, most pronounced in the HF+TEA group, were noted.(ABSTRACT TRUNCATED AT 250 WORDS)

Thoracic epidural analgesia in aortocoronary bypass surgery. II: Effects on the endocrine metabolic response

Thoracic epidural analgesia (TEA) may offer haemodynamic benefits for patients with coronary heart disease going through major surgery. This may-in part-be secondary to an effect on the endocrine and metabolic response to surgery. We therefore investigated the effect of TEA on the endocrine metabolic response to aortocoronary bypass surgery (ACBS). Thirty male patients (age < 65 years, ejection fraction > 0.5) were randomized into 3 groups; the HF group receiving a high dose fentanyl (55 micrograms.kg-1) anaesthesia, the HF+TEA group with the same fentanyl dose+TEA with 10 ml bupivacain 5 mg.ml-1, followed by 4 ml every hour, and the LF+TEA group receiving fentanyl 15 micrograms.kg-1 + TEA. Adrenalin, noradrenalin, systemic vascular resistance (SVR), glucose, cortisol, lactate and free fatty acids were followed during the operation and for 20 h postoperatively. A significant increase in adrenalin, noradrenalin and SVR was found in the HF group whereas this increase was blocked in both epidural groups. An increase in glucose and cortisol was noticed in all groups, but the increase was delayed in the epidural groups. Our results suggest that a more effective blockade of the stress response during ACBS is obtained when TEA is added to general anaesthesia than with high dose fentanyl anaesthesia alone.

Effects of atrial natriuretic peptide on renal function after cardiac surgery and in cyclosporine-treated heart transplant recipients

The study investigated the effects of intravenous infusion of atrial natriuretic peptide (human ANP 99-126) on renal function and central hemodynamics after coronary artery bypass grafting (CABG), and the ability of ANP to reverse the acute nephrotoxic effects of cyclosporine after heart transplantation. Ten patients with an EF > 0.5 and normal renal function were studied 2 to 4 hours after CABG surgery. Furthermore, six heart transplant recipients receiving cyclosporine for immunosuppression who developed renal dysfunction 2 to 4 days after transplantation were studied. Standard urinary clearance of 51Cr-EDTA and PAH was used to study the effects of ANP on glomerular filtration rate (GFR) and renal blood flow (RBF). Baseline measurements were first performed during two 30-minute periods. Incremental infusion rates of ANP were then administered for three consecutive 30-minute periods (25, 50, and 100 ng/kg/min), followed by two 30-minute post-ANP control periods. Marked increases in urinary flow (UF), GFR, filtration fraction (FF), and fractional urinary excretion of Na+ were observed in the CABG patients with increasing doses of ANP, while RBF was unchanged. Mean arterial pressure decreased by around 15% at the highest ANP dose. In the heart transplant recipients, baseline GFR was markedly reduced compared to pretransplantation values (-65%). UF, GFR, and RBF increased 240%, 69%, and 53%, respectively, while renal vascular resistance decreased 45% during the highest dose of ANP infused. At this ANP dose level, circulating ANP concentrations were sixfold to eightfold higher than the preinfusion control level.(ABSTRACT TRUNCATED AT 250 WORDS)

The role of serotonin blockers in cardiac anesthesia

In the complex setting of cardiac surgery and cardiopulmonary bypass, several potent mediators are released that by interacting may cause clinical syndromes like coronary ischemia, systemic hypertension, pulmonary hypertension, and renal failure. One of the mediators is serotonin, released from aggregating platelets, and causing vasoconstriction by activating S2-serotonergic receptors, particularly in patients with an impaired endothelial function, as in atherosclerosis. The most important available specific S2-serotonergic receptor antagonist is ketanserin. If administered during or after cardiac surgery, ketanserin lowers systemic and pulmonary blood pressure, and improves peripheral and pulmonary perfusion without causing reflex tachycardia or an increase in pulmonary shunt fraction.

Multicenter trial of automated nitroprusside infusion for postoperative hypertension. Titrator Multicenter Study Group

Hypertension is common after a cardiac operation and may result in postoperative hemorrhagic and other complications. Most often this problem has been treated using manually controlled doses of intravenous sodium nitroprusside. To evaluate the clinical impact of an automated closed-loop administration system on patients after cardiotomy, a prospective trial was conducted at nine clinical centers. Patients with hypertension were managed by either manual nitroprusside titration (n = 532) or a closed-loop automated titration system (n = 557). Patient groups were not significantly different in age, weight, or height. Moreover, the types of surgical procedures were comparable: primary coronary artery bypass grafting, 59.2% and 58.9%, manual group versus automated group; repeat coronary artery bypass grafting, 10.5% and 8.6%, respectively; valve procedures, 11.3% and 15.1%, respectively; and other cardiac procedures, 19.0% and 17.4%, respectively (all p = not significant). The automated group showed a significant reduction in the number of hypertensive episodes per patient (1.8 +/- 0.2 versus 0.6 +/- 0.07; p = 0.0001. At the same time, the number of hypotensive episodes per patient was reduced with automated closed-loop titration (0.40 +/- 0.05 versus 0.30 +/- 0.03; p = 0.02). Chest tube drainage (866 +/- 37 mL versus 693 +/- 23 mL [mean +/- standard error of the mean]; p = 0.0001), percentage of patients receiving transfusion (40.0% versus 33.0%; p = 0.02), and total amount transfused (2.4 +/- 0.12 units versus 2.0 +/- 0.10 units; p = 0.0003) were all reduced significantly by the use of an automated titration system.(ABSTRACT TRUNCATED AT 250 WORDS)

Does propranolol alter the vascular response to phenylephrine before or during halothane anaesthesia in patients with coronary artery disease?

Preoperative beta-adrenergic blockade with propranolol, by allowing unopposed alpha-adrenergic stimulation in response to stress, has been suggested as a factor contributing to hypertension following coronary artery bypass surgery (CABG). Thus, one might expect to find an exaggerated haemodynamic response to phenylephrine (PHE), an alpha 1 agonist. To study this, the cardiovascular response to PHE infusion at 30, 40, and 50 microgram.min-1 prior to and during halothane anaesthesia was measured before surgical stimulation during elective CABG in patients taking chronic propranolol therapy and compared with that of patients not taking any cardiovascular medications. Chronic propranolol therapy did not alter the haemodynamic response to PHE, before or during halothane anaesthesia, and the incidence of postoperative hypertension requiring vasodilator therapy was the same for both groups.

Haemodynamic effects of ketanserin following coronary artery bypass grafting

The haemodynamic effects of ketanserin were studied consecutively in seventeen patients in the intensive care unit following coronary artery bypass grafting. Hypertensive patients (Group 1, systolic blood pressure (SBP) greater than or equal to 150 mmHg following discontinuation of nitroprusside, n = 10) received intravenous ketanserin 10 mg and infusion of 0.1 mg.kg-1.hr-1 with additional boluses as required to maintain SBP less than or equal to 130 mmHg for one hour. Non-hypertensive patients (Group 2, SBP less than 150 mmHg, n = 7) received a 5 mg bolus and the same infusion. Ketanserin significantly decreased arterial blood pressure (P less than 0.001) in all patients in Group 1. Heart rate was decreased but not significantly. Cardiac index, systemic and pulmonary vascular resistance and pulmonary shunt fraction were not significantly altered from pre-ketanserin values when blood pressure was controlled with nitroprusside. Normotensive patients in Group 2 did not show any undesirable hypotension or significant haemodynamic changes. Mean nitroprusside dose requirements following ketanserin therapy were significantly reduced by 91.6% in Group 1 and 78.4% in Group 2 (P less than 0.05). Ketanserin is effective in treating hypertension following coronary artery bypass grafting with an advantage of lack of reflex tachycardia.

Efficacy and safety of intravenous nicardipine in the control of postoperative hypertension. IV Nicardipine Study Group

In a double-blind, randomized, multicenter study, the efficacy and safety of intravenous (IV) nicardipine was compared with placebo in the control of postoperative hypertension in cardiac and noncardiac surgical patients. One hundred twenty-two patients (17 cardiac and 105 noncardiac surgery) met the entry criteria (systolic BP greater than or equal to 140 mm Hg or diastolic BP greater than or equal to 95 mm Hg) and were randomized (3:2) to receive IV nicardipine (n = 71) or placebo (n = 51). Therapeutic response (greater than or equal to 15 percent reduction in BP from baseline) was achieved in 94 percent of patients treated with IV nicardipine vs 12 percent with placebo (p less than 0.001). The mean response time and infusion rate for IV nicardipine were 11.5 (+/- 0.8) minutes and 12.8 (+/- 0.3) mg/h, respectively. The magnitude of BP reduction was similar in both cardiac and noncardiac postsurgical patients. Blood pressure control was sustained with minimal dose adjustments of IV nicardipine (3.0 +/- 0.2 mg/h) during a prolonged maintenance infusion period of 6.8 +/- 0.5 h. A reflex mean increase in heart rate of 5 bpm was seen in patients treated with IV nicardipine. Sixteen patients (15 noncardiac and one cardiac surgery) had a sustained heart rate of greater than 100 bpm, with a mean increase of 24 bpm from the baseline. In all these patients except three, tachycardia was resolved while receiving nicardipine. None of these patients who had development of tachycardia during nicardipine therapy had exhibited ST segment changes indicative of ischemia. One patient with tachycardia at baseline had exhibited ST segment depression (3 to 4 mm) during nicardipine treatment, which was resolved following discontinuation of nicardipine therapy and application of nitroglycerin (Nitropaste). Hemodynamic evaluation revealed that IV nicardipine significantly decreased mean arterial pressure, systemic vascular resistance, and significantly increased cardiac index with no change in heart rate. These hemodynamic changes were similar in cardiac and noncardiac surgical patients. Adverse experiences reported with IV nicardipine included hypotension (4.5 percent), tachycardia (2.7 percent), and nausea/vomiting (4.5 percent). In the placebo group, the incidence of adverse experience was 6 percent, with an equal distribution of hypotension (2 percent), nausea/vomiting (2 percent), and headache (2 percent). No clinically important changes in laboratory variables related to IV nicardipine were reported. In conclusion, these findings indicate that nicardipine, a titratable intravenous calcium channel blocker, can rapidly and effectively control postoperative hypertension in cardiac and noncardiac surgical patients.

Labetalol for the control of elevated blood pressure following coronary artery bypass grafting

In a multicenter study, the efficacy and safety of intravenous (IV) labetalol for the control of elevated blood pressure were studied in the intensive care unit (ICU) in 65 patients within 4 hours following coronary artery bypass grafting (CABG). Patients with pre-existing ventricular dysfunction, bradycardia, bronchospastic disease, or postoperative complications were excluded. All patients were monitored with a thermodilution pulmonary artery catheter. Entry criteria were a systolic blood pressure (SBP) greater than 140 mm Hg or diastolic blood pressure (DBP) greater than 90 mm Hg for at least five minutes. Intravenous labetalol was loaded incrementally (5, 10, 20, and 40 mg at 10-minute intervals) to a maximum cumulative dose of 75 mg, until either SBP decreased 10% or DBP decreased 10% and was less than 90 mm Hg. Responders were entered into a 6-hour maintenance period, and received 5 to 40 mg of IV labetalol every 10 minutes as needed for blood pressure control. Hemodynamic data and temperature were recorded at baseline, just before each dose of labetalol during the loading period, and at the end of the maintenance period. Alternative therapy was given in the case of nonresponse or adverse events. Intravenous labetalol successfully controlled post-CABG hypertension in 55 of 65 patients (85%); of these, 46 responded to 35 mg or less. Although 28 patients required no further labetalol in the maintenance period, in the others dosage varied from 5 to 400 mg. Reductions in SBP and DBP were associated with moderate reductions in pulse pressure (SBP-DBP) and heart rate (HR). Cardiac index decreased by 18.5%, with a 12.5% decrease in stroke index and 8.1% decrease in HR. Systemic vascular resistance did not increase significantly. Four patients (6%) developed hypotension related to IV labetalol. There was one death due to perioperative myocardial infarction, which was unrelated to labetalol use. The mechanism of action of IV labetalol in controlling hypertension after CABG surgery seems to be moderate negative inotropy and chronotropy. Its alpha-blocking effects seem to be important in preventing reflex vasoconstriction. This is directly opposite to the primary vasodilator effect found when IV labetalol is used to control nonsurgical hypertension. Because of these actions, labetalol should be avoided or used with caution in patients with preoperative and postoperative cardiac dysfunction. In patients with normal left ventricular function, IV labetalol appears to be a safe, effective agent in controlling post-CABG hypertension, with the added potential benefit of enhanced myocardial oxygen balance.

Serotonin and acute cardiovascular disorders

In this survey the possible role of serotonin in such acute disorders as systemic and pulmonary hypertension following cardiac surgery is discussed. Although platelets are activated during cardiopulmonary bypass, the increase in serotonin plasma levels is limited because the serotonin released is taken up by normal platelets and endothelial cells. This does not imply that serotonin is not involved in the origin of systemic hypertension during and after cardiac surgery, because subthreshold or threshold doses of this amine amplify the vasoconstrictive effect of, for example, epinephrine and norepinephrine, the levels of which are significantly elevated under these circumstances. That serotonin plays a role through its amplifying effect is supported by the finding that ketanserin, a specific S2-serotonergic receptor antagonist with alpha 1-adrenergic receptor blocking properties, effectively lowers arterial blood pressure in patients with systemic postoperative hypertension by combined blockade of these receptors. The compound is also effective in the treatment of pulmonary hypertension after valve replacement, indicating that serotonin plays a role in the origin of this disorder. This idea is supported by the experimental finding that serotonin induces pulmonary hypertension. It is an interesting observation that, unlike such compounds as nitroprusside, ketanserin does not affect intrapulmonary shunting in patients with systemic hypertension and even reduces the intrapulmonary shunt fraction in patients with pulmonary hypertension. These findings indicate that this compound dilates the resistance vessels in well-ventilated, but not in poorly ventilated areas, and may dilate constricted bronchi.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison among manual, computer-assisted, and closed-loop control of blood pressure after cardiac surgery

Forty-five patients who required vasodilator therapy for systemic arterial hypertension following cardiac surgery were randomly allocated to receive: (1) manual control of a sodium nitroprusside (SNP) infusion; (2) computer-assisted control where the nurse was provided with a color graphical display of performance; or (3) automatic closed-loop control. Limits of acceptable systolic pressure were prescribed for each patient, and the percentage time spent outside these limits was calculated for each patient. The closed-loop computer system (CLCS) produced significantly better control than either manual or computer-assisted systems for the time spent outside the prescribed limits (P less than 0.001), and better control for the time spent outside the limits +/- 10 mmHg (manual P less than 0.001; assisted P less than 0.01). While the CLCS proved more satisfactory than manual control for the limits +/- 20 mmHg and +/- 30 mmHg (+/- 20 mmHg P less than 0.001; +/- 30 mmHg P less than 0.01), there was no significant difference in the quality of control between the CLCS and computer-assisted systems for these limits. The results suggest that the quality of blood pressure control achieved by nurses can be improved by providing them with a clear graphical display of their performance. Better control of blood pressure should reduce the adverse effects of hypotension and hypertension following cardiac surgery.

Microcomputer-controlled administration of vasodilators following cardiac surgery: technical considerations

Hypertension in the early postoperative period after cardiopulmonary bypass is associated with increased morbidity, and is commonly managed by the infusion of short-acting vasodilators. Automatic arterial blood pressure control by closed-loop infusion has been shown to be superior to manual control in several studies. The investigators have developed a closed-loop arterial pressure control system based on the Atari 1040ST microcomputer (Atari, Sunnyvale, CA). The program uses a proportional-integral-derivative control algorithm, developed from that described by Sheppard and his colleagues. The arterial waveform is sampled digitally, and the waveform analysis routine incorporates several artifact detection and rejection functions. Additional safety features are provided in the computer-infusion pump subroutine, which cause alarms to be activated if computer-pump communication fails to occur within a specified time period. A novel feature of this system is the clinical staff's use of a "mouse" to enter data and control the program, which makes keyboard skills unnecessary. This system is in routine service in the cardiac intensive care unit (CICU), both for direct clinical use and for research into various aspects of arterial pressure control, and has proved to be acceptable to the clinical staff.

Development and evaluation of a dual-pump microcomputer-based closed-loop arterial pressure control system

Hypertension after cardiac surgery is common and is associated with increased morbidity. It is usually managed by the infusion of short acting vasodilators. The use of a closed-loop computer system to control the infusion of a vasodilator has been shown to compare favourably with manual control. We have developed a closed-loop system for the ATARI 1040ST microcomputer to control arterial pressure by the simultaneous infusion of two vasodilators. The control program is based on a proportional-integral-derivative algorithm which has been adapted to allow control of two IMED 929 infusion pumps from one RS-232 port. All communication between the user and computer is carried out with a 'mouse', thus increasing acceptability of the system to ward staff. Cardiovascular data are collected on-line from the patient monitor via a custom-built analogue to digital convertor. This system was used to study glyceryl trinitrate and sodium nitroprusside in 24 patients requiring vasodilators after cardiopulmonary bypass. The study showed that in 14 of the patients hypertension was controlled by GTN alone and 10 required supplementary SNP. We have demonstrated that this dual-pump automatic arterial pressure control system is a satisfactory and safe method of administering two vasodilators simultaneously. It is suitable for both routine clinical and research uses.

Automatic control of arterial pressure after cardiac surgery. Evaluation of a microcomputer-based control system using glyceryl trinitrate and sodium nitroprusside

Arterial hypertension after cardiac surgery is common and is associated with increased morbidity. Glyceryl trinitrate may be a more suitable agent for control of hypertension than sodium nitroprusside. We have developed a closed-loop system for the Atari 1040ST microcomputer to control arterial pressure by the simultaneous infusion of two vasodilators under computer control. Use of this system with glyceryl trinitrate and sodium nitroprusside in 24 patients who required vasodilators after cardiopulmonary bypass, revealed that hypertension was controlled by glyceryl trinitrate alone in 14 of the patients and 10 required supplementary sodium nitroprusside. The results suggest that glyceryl trinitrate is a suitable agent for control of hypertension after cardiac surgery in the majority of patients. They also show that a sizeable minority required additional sodium nitroprusside, and that an automated 'dual pump' system is a satisfactory method of administering two vasodilators in this way.

Effect of preoperative renin-angiotensin system blockade on hypertension following coronary surgery

Renin-angiotensin system activation is suspected of being involved in postcoronary surgery hypertension, but appears to be useful in maintaining blood pressure during anesthesia and cardiopulmonary bypass. To clarify these points, 19 patients were compared: ten as a control group and nine who received captopril during two days before surgery. Anesthesia was the same for the two groups, and cardiopulmonary bypass ensured nonpulsatile flow rates. Anesthesia induced a slight decrease in the mean arterial blood pressure of the treated group (91.1 +/- 3.3 mm Hg to 83.3 +/- 3.9 mm Hg), which did not occur in the control group (89.9 +/- 5.8 mm Hg to 89.7 +/- 4.9 mm Hg). During cardiopulmonary bypass, the mean arterial blood pressure was maintained at comparable levels in the two groups (65.6 +/- 3.5 mm Hg in the control group, 72.6 +/- 3.0 mm Hg in the treated group), with same pump flow rates. After cardiopulmonary bypass, the mean arterial blood pressure returned nearly to prebypass values. Postoperatively, three patients in the control group and four in the treated group developed hypertension. Thus, preoperative renin-angiotensin system blockade by a converting-enzyme inhibitor did not impair blood pressure regulation during anesthesia and cardiopulmonary bypass, but failed to prevent hypertension following coronary surgery.

Postoperative ventilatory and circulatory effects of heating after aortocoronary bypass surgery. Postoperative external heat supply

The effects of postoperative external heat supply on shivering, oxygen uptake, carbon dioxide production, ventilatory requirements and haemodynamic variables were studied postoperatively after aortocoronary bypass surgery in 24 men with stable angina pectoris. After hypothermic cardiopulmonary bypass (CPB) at 25 degrees C, the patients were rewarmed to a nasopharyngeal temperature of at least 38 degrees C, resulting in a rectal temperature of about 34 degrees C before termination of CPB. Twelve patients, forming the control group, were given no other external heat supply. In another group (n = 12), the "radiant heat supply group", additional external heat was provided postoperatively, the main source of which was a thermal ceiling supplemented with heated, humidified respiratory gases. In this latter group the postoperative rewarming was accomplished earlier and was converted into a mainly passive process. Shivering, oxygen uptake, CO2 production and ventilation volumes were significantly reduced compared with the control group. Cardiac index and stroke index were higher and systemic oxygen extraction was lower in the radiant heat supply group. Postoperative hypertension and vasoconstriction were greatly decreased, suggesting that residual hypothermia is an important cause of the postoperative vasoconstriction.

Influence of ketanserin pretreatment on the haemodynamic responses to sternotomy

The effect of intravenous ketanserin on the pressor response to sternotomy was studied in 36 patients undergoing coronary artery surgery. Two doses of the drug (10 mg and 20 mg) were compared with a placebo injection of saline. After induction of anaesthesia, haemodynamic variables were measured until the institution of cardiopulmonary bypass. Plasma and platelet 5-hydroxyindoles and 5-hydroxytryptamine were measured in a subset of 13 patients. Ketanserin induced a dose-dependent amelioration of the pressor response to sternotomy. Plasma 5-hydroxyindoles and platelet 5-hydroxytryptamine levels did not correlate with clinical response. The increased effectiveness of the higher dose of ketanserin may be due to an effect other than serotonin antagonism.

Clonidine and the sympatico-adrenal response to coronary artery by-pass surgery

Clonidine was administered intravenously in an attempt to limit sympatico-adrenal activity and thereby reduce the incidence of arterial hypertension associated with coronary artery by-pass graft surgery (CABG). Forty patients scheduled for CABG were assigned to two groups. Twenty patients received clonidine 4 micrograms kg-1 before surgery, 2 micrograms kg-1 after cardiopulmonary by-pass and 1 microgram kg-1 when the skin was sutured. The other 20 patients served as controls. All patients were anesthetized with fentanyl, droperidol, nitrous oxide and alcuronium. During surgery 5 min after sternotomy, mean arterial pressure was 13 mmHg lower (P less than 0.01) in the clonidine group, while after operation the difference between the groups was negligible. Both during and after surgery the plasma catecholamine concentrations were significantly lower in the clonidine group (P less than 0.01). The greatest difference between the groups was seen 90 min after operation, when plasma noradrenaline and plasma adrenaline concentrations in the clonidine group were less than 1/3 of those in the control group (P less than 0.01). As judged by catecholamine concentrations clonidine was effective in attenuating sympatico-adrenal hyperactivity during and after surgery. Postoperative arterial hypertension was not reduced, however, and it is concluded that other factors besides sympatico-adrenal hyperactivity must be important.

Pathophysiology of hypertension following coronary artery bypass surgery: an experimental dog model for postoperative hypertension

Immediate postoperative hypertension has been reported to occur during the first 3-6 h in 30%-75% of patients who have undergone aortocoronary bypass operations. Although some causes and potential predisposing factors of this type of hypertension have been cited, the mechanisms involved still remain unclear. Some studies have implicated the involvement of nerve reflexes originating from the heart, great vessels, and coronary arteries, but they do not explain the exact role of such impulses. The paucity of data in humans is, needless to say, due primarily to the invasive nature of the experimental procedure. To further our knowledge on the involvement of nerve reflexes as a factor in initiating immediate postoperative hypertension, we used a dog model and devised a modified form of surgery by inserting a soft catheter into the left coronary artery to form a stenosis; we measured several factors usually involved in hypertension. We succeeded in performing this modified form of surgery in 10 of 81 dogs. Our model showed that the mean aortic pressure significantly increased from 81 +/- 5.5 to 102 +/- 7.0 mmHg (P less than 0.05), systemic vascular resistance from 7604 +/- 833 to 9648 +/- 1101 dyn.s.cm-5 (P less than 0.05), and plasma noradrenaline levels from 0.45 +/- 0.092 to 0.51 +/- 0.087 ng/ml (P less than 0.01) immediately after restoration of blood flow to the distal area behind the stenosis. These dynamic and humoral characteristics are similar to ones documented in current clinical reports. To our knowledge, this is the first experimental animal model of hypertension after coronary artery bypass graft surgery.

Cardiac receptors: their function in health and disease

Cardiac receptors include both mechanically and chemically sensitive receptors located in atria and in ventricles. Atrial receptors innervated by myelinated vagal afferent fibers reflexly regulate heart rate and intravascular volume. On the other hand, stimulation of ventricular receptors can cause either reflex bradycardia and hypotension or, alternatively, excitation of the cardiovascular system. The former response is mediated by vagal afferents, whereas the latter is mediated by sympathetic (spinal) afferents. Under normal circumstances, cardiac receptors sense changes in wall motion or diastolic pressure and perhaps provide a fine tuning of the cardiovascular system. However, under certain pathological conditions such as coronary ischemia, which cause release of substances such as bradykinin and prostaglandins, there is an exaggerated response of the ventricular receptors. Because these receptors cause a reflex depression of the cardiovascular system and, in particular, induce renal vasodilation, they may protect the heart and kidney by lessening myocardial oxygen requirements and by increasing renal blood flow. In the situation of heart failure both atrial and ventricular receptors are reset and therefore provide for an exaggerated neurohumoral discharge. Finally, patients with aortic stenosis may demonstrate a paradoxical vasodilation and syncope during exercise when there likely is excessive stimulation of left ventricular receptors by the high transmural pressure.

Pulsatile vs. non-pulsatile flow during cardiopulmonary bypass. A comparison of early postoperative changes

The aim of the study was to evaluate possible haemodynamic and metabolic effects of pulsatile flow in cardiopulmonary bypass. The subjects were 20 patients undergoing coronary artery bypass grafting. They had no complicating diseases. Ten consecutive patients with pulsatile perfusion were compared with ten consecutive patients with non-pulsatile perfusion. The haemodynamic parameters, chest X-rays, fluid balance and changes in circulating thrombocytes were unaffected by adding pulsatile flow to cardiopulmonary bypass. The arterial-venous oxygen content difference and intrapulmonary shunting were also unaffected. Whole-body oxygen consumption was higher in the pulsatile group immediately after bypass, but subsequently there were no differences. The haemoglobin and haematocrit values were higher in the non-pulsatile group two hours postoperatively, but did not differ in the rest of the observation period. The clinical course was similar in the two groups.

[Sodium nitroprusside and coronary surgery]

The anti-hypertensive properties of sodium nitroprusside have been tested in 20 patients undergoing coronary arterial surgery. Were measured the arterial pressure, heart rate, mean right atrial pressure and mean left atrial pressure. The cardiac output, systemic vascular resistance and left ventricular stroke work index were deduced. A dose of 0.8 to 3 micrograms . kg-1 . min-1 sodium nitroprusside was given at the start of surgery, and immediately afterwards. The results showed a decrease of the systemic vascular resistance, a significant drop of arterial pressure, and a significant increase of heart rate as well as a tendency for the cardiac output to fall, probably because of insufficient vascular filing. When the mean left atrial pressure was kept at 14.8 +/- 3 mmHg (1.97 +/- 0.40 kPa), and left ventricular stroke work index fell, whilst cardiac output increased. Sodium nitroprusside seemed to be useful in coronary arterial surgery if used with care.

Changes in peripheral vascular and cardiac sympathetic activity before and after coronary artery bypass surgery: interrelationships with hemodynamic alterations

The plasma catecholamine levels obtained simultaneously from radial artery (A), pulmonary artery (MV), brachial vein (PV), and coronary sinus (CS) were measured concurrent with hemodynamic determinations during coronary artery bypass graft (CABG) operations. Arterial catecholamine levels decreased after induction of anesthesia and increased after sternotomy; changes in veno-arterial norepinephrine (NE) differences ([PV-A]ne, [MV-A]ne, and [CS-A]ne) were of the same magnitude and direction, suggesting that NE release from various organs was of the same extent. After operation, arterial NE increased further, but the veno-arterial NE differences were in striking contrast; [PV-A]ne became markedly positive, whereas [CS-A]ne became markedly negative, indicating that NE release from extremity peripheral vasculature increased markedly while cardiac NE release decreased. These differential changes in regional sympathetic activity appear to be related to postoperative hypertension (HT) and low cardiac output (CO). There were close relationships of changes in [MV-A]ne to mean arterial pressure (r = 0.78, p less than 0.001) and systemic vascular resistance (r = 0.62, p less than 0.010, suggesting that the sympathetic nervous system plays an important role in CABG perioperative hemodynamic alterations.

Systemic arterial hypertension associated with cardiac surgery

Significant hypertension can develop in 15 to 40 percent of patients undergoing various types of cardiac surgery. These hypertensive episodes can occur at almost any time before, during or after open or closed chest operations. The various hypertensions encountered in this context do not form a homogeneous entity; they are nt due to the same causes and do not necessarily develop by the same mechanisms. Their frequency and seriousness have been demonstrated by reports from many centers: hence, the urgent need for accurate definition of their various types to allow correct identification and therapy. A classification based on well defined clinical events is therefore proposed and possible mechanisms for the more common types of hypertension are reviewed. Prophylactic measures nclude reassurance, attention to details of anesthesia and maintenance of preoperative antihypertensive therapy when indicated; for patients with coronary artery disease, preventive nitrate therapy as well as prompt attention to chest pain is essential. Both general and specific antihypertensive measures to control the more common types of hypertension complicating cardiac surgery are outlined.

Hypertension following coronary artery bypass surgery. Role of preoperative propranolol therapy

Over a 9-month period, the incidence and characteristics of hypertension following coronary artery bypass surgery were studied in a group of 52 patients. Hypertension occurred in 61% of the patients and was characterized by an increase in arterial blood pressure of 35 +/- 2 mm Hg mean +/- SEM during the early postoperative period. Preoperative blood pressures and hemodynamic variables were similar in those who developed hypertension of those who remained normotensive. Ninety-four percent of those who developed hypertension as compared to only 40% of those who remained normotensive received propranolol during the 24 hours preceding surgery (x2 = 15.4; p less than 0.001). Maximal blood pressures during the first 5 hours following the termination of cardiopulmonary bypass were significantly positively correlated with preoperative propranolol dosage (p less than 0.01). Hypertension was not associated with significant changes in plasma renin activity or angiotensin II levels, but concomitant plasma catecholamine concentrations were elevated significantly (p less than 0.005). However, a similar rise in plasma catecholamine concentrations was found in those who remained normotensive. Hypertension was associated with an increase in systemic vascular resistance (p less than 0.001) and left ventricular stroke work index (p less than 0.05), and a fall in stroke volume (p less than 0.005) and cardiac index (p less than 0.001). These studies suggest that hypertension following coronary artery bypass surgery is common, results from an increase in systemic vascular resistance, is not renin-angiotensin mediated, and may, in part, be related to preoperative propranolol administration.

Myocardial performance early after aorto-coronary bypass surgery and the influence of nitroprusside infusion

The central and peripheral circulation were studied in 12 patients after aortocoronary bypass surgery. During the initial 5 h after termination of cardiopulmonary bypass, the oesophageal temperature rose from 36.5 degrees C to 39.4 degrees C, concomitant with cutaneous vasoconstriction and an increase in systemic vascular resistance (SVR) and mean arterial blood pressure (MABP). The oxygen uptake index (Vo2I) increased by 57% during the rewarming period. The cardiac index (CI), which was constant at 2.8 l.min-1.m-2, was too low to satisfy this oxygen demand and the arterio-venous oxygen content difference (AVDo2) increased to 3.0 mmol . l-1 by the 3rd hour. After 5 h, SVR had decreased and cutaneous vasodilation began. Vo2I and AVDo2 decreased. The postoperative myocardial function was moderately impaired and deteriorated after the cutaneous vasodilation. Twelve patients were given an infusion of sodium nitroprusside during the postoperative period (0.25--2.5 micrograms . kg-1 . min-1). The rewarming pattern was not influenced by this infusion, but the initial increases in MABP and SVR were eliminated. The myocardial performance was better in the nitroprusside group. CI was significantly higher than in the control group (3.5 l.min-1.m-2) and AVDo2 remained normal.