Systemic hypertension associated with coronary artery bypass surgery

Postoperative Intensive Care Management of Aortic Repair

Vascular surgery patients have multiple comorbidities and are at high risk for perioperative complications. Aortic repair surgery has greatly evolved in recent years, with an increasing predominance of endovascular techniques (EVAR). The incidence of cardiac complications is significantly reduced with endovascular repair, but high-risk patients require postoperative ST-segment monitoring. Open aortic repair may portend a prohibitive risk of respiratory complications that could be a contraindication for surgery. This risk is greatly reduced in the case of an endovascular approach, and general anesthesia should be avoided whenever possible in the case of endovascular repair. Preoperative renal function and postoperative kidney injury are powerful determinants of short- and long-term outcome, so that preoperative risk stratification and secondary prevention are critical tasks. Intraoperative renal protection with selective renal and distal aortic perfusion is essential during open repair. EVAR has lower rates of postoperative renal failure compared to open repair, with approximately half the risk for acute kidney injury (AKI) and one-third of the risk of hemodialysis requirement. Spinal cord ischemia used to be the most distinctive and feared complication of aortic repair. The risk has significantly decreased since the beginning of aortic surgery, with advances in surgical technique and spinal protection protocols, and is lower with endovascular repair. Endovascular repair avoids extensive aortic dissection and aortic cross-clamping and is generally associated with reduced blood loss and less coagulopathy. The intensive care physician must be aware that aortic repair surgery has an impact on every organ system, and the importance of early recognition of organ failure cannot be overemphasized.

Revascularization for Coronary Artery Disease: Principle and Challenges

Coronary revascularization is the most important strategy for coronary artery disease. This review summarizes the current most prevalent approaches for coronary revascularization and discusses the evidence on the mechanisms, indications, techniques, and outcomes of these approaches. Targeting coronary thrombus, fibrinolysis is indicated for patients with diagnosed myocardial infarction and without high risk of severe hemorrhage. The development of fibrinolytic agents has improved the outcomes of ST-elevation myocardial infarction. Percutaneous coronary intervention has become the most frequently performed procedure for coronary artery disease. The evolution of stents plays an important role in the result of the procedure. Coronary artery bypass grafting is the most effective revascularization approach for stenotic coronary arteries. The choice of conduits and surgical techniques are important determinants of patient outcomes. Multidisciplinary decision-making should analyze current evidence, considering the clinical condition of patients, and determine the safety and necessity for coronary revascularization with either PCI or CABG. For coronary artery disease with more complex lesions like left main disease and multivessel disease, CABG results in more complete revascularization than PCI. Furthermore, comorbidities, such as heart failure and diabetes, are always correlated with adverse clinical events, and a routine invasive strategy should be recommended. For patients under revascularization, secondary prevention therapies are also of important value for the prevention of subsequent adverse events.

Post-carotid Endarterectomy Hypertension. Part 2: Association with Peri-operative Clinical, Anaesthetic, and Transcranial Doppler Derived Parameters

OBJECTIVE/BACKGROUND

The first paper in this series observed that pre-operative baroreceptor dysfunction and poorly controlled hypertension were independently predictive for identifying patients who went on to require treatment for post-endarterectomy hypertension (PEH). The second paper examines the influence of intra-operative patient, transcranial Doppler (TCD) ultrasound, and anaesthetic variables on the incidence of PEH.

METHODS

In total, 106 patients underwent carotid endarterectomy (CEA) under general anaesthesia. Systolic blood pressure (SBP) changes, anaesthetic and vasoactive agents, analgesia, and post-operative pain scores, as well as TCD derived changes in middle cerebral artery (MCA) velocity during surgery were recorded. Patients who met pre-existing unit criteria for treating PEH after CEA (SBP > 170 mmHg without symptoms or SBP > 160 mmHg with headache/seizure/neurological deficit) were treated according to an established and validated protocol.

RESULTS

In total, 40/106 patients (38%) required treatment for PEH following CEA (26 in theatre recovery [25%], 27 back on the vascular surgery ward [25%]), whereas seven (7%) had SBP surges > 200 mmHg on the ward. Patients requiring treatment for PEH had significantly higher pre-induction SBP (174 ± 21 mmHg vs. 153 ± 21 mmHg; p < .001), the greatest decreases in SBP after induction of anaesthesia (median decrease 100 ± 32 mmHg vs. 83 ± 24 mmHg; p = .01) and were significantly more likely to experience moderate/severe pain scores post-operatively (p = .003). Logistic regression analysis of the pre- and intra-operative data revealed that higher pre-induction mean SBP and lower pre-operative (impaired) BRS were the only independent predictors of PEH.

CONCLUSION

This analysis of intra-operative variables has demonstrated that patients with poorly controlled and/or labile hypertension at induction of general anaesthesia were those at greatest risk of requiring treatment for PEH in the post-operative period after CEA. No other variables, including use of vasopressors, treatment of hypotension, anaesthetic agents, or changes in MCA velocity after clamp release and restoration of flow were able to predict who might go on to require treatment for PEH. Identification of at-risk individuals and aggressive blood pressure control in the post-operative period remains the mainstay of treatment.

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.

Postoperative Critical Care of the Adult Cardiac Surgical Patient. Part I: Routine Postoperative Care

OBJECTIVES

Cardiac surgery, including coronary artery bypass, cardiac valve, and aortic procedures, is among the most common surgical procedures performed in the United States. Successful outcomes after cardiac surgery depend on optimum postoperative critical care. The cardiac intensivist must have a comprehensive understanding of cardiopulmonary physiology and the sequelae of cardiopulmonary bypass. In this concise review, targeted at intensivists and surgeons, we discuss the routine management of the postoperative cardiac surgical patient.

DATA SOURCE AND SYNTHESIS

Narrative review of relevant English-language peer-reviewed medical literature.

CONCLUSIONS

Critical care of the cardiac surgical patient is a complex and dynamic endeavor. Adequate fluid resuscitation, appropriate inotropic support, attention to rewarming, and ventilator management are key components. Patient safety is enhanced by experienced personnel, a structured handover between the operating room and ICU teams, and appropriate transfusion strategies.

Does high thoracic epidural analgesia with levobupivacaine preserve myocardium? A prospective randomized study

Background. Our study aimed to compare HTEA and intravenous patient-controlled analgesia (PCA) in patients undergoing coronary bypass graft surgery (CABG), based on haemodynamic parameters and myocardial functions. Materials and Methods. The study included 34 patients that were scheduled for elective CABG, who were randomly divided into 2 groups. Anesthesia was induced and maintained with total intravenous anesthesia in both groups while intravenous PCA with morphine was administered in Group 1 and infusion of levobupivacaine was administered from the beginning of the anesthesia in Group 2 by thoracic epidural catheter. Blood samples were obtained presurgically, at 6 and 24 hours after surgery for troponin I, creatinine kinase-MB (CK-MB), total antioxidant capacity, and malondialdehyde. Postoperative pain was evaluated every 4 hours until 24 hours via VAS. Results. There were significant differences in troponin I or CK-MB values between the groups at postsurgery 6 h and 24 h. Heart rate and mean arterial pressure in Group 1 were significantly higher than in Group 2 at all measurements. Cardiac index in Group 2 was significantly higher than in Group 1 at all measurements. Conclusion. Patients that underwent CABG and received HTEA had better myocardial function and perioperative haemodynamic parameters than those who did not receive HTEA.

Nicardipine versus Sodium Nitroprusside for Postcardiac Surgery Hypertension: An Evaluation of Effectiveness and Postoperative Costs

Background

Postoperative hypertension after cardiac surgery is associated with substantial morbidity. Both sodium nitroprusside (SNP) and nicardipine (NIC) are effective in its management. Outcomes data for NIC and SNP in persons undergoing cardiac surgery are limited, and there are no data characterizing the influence of drug choice on postoperative costs.

Objective

Our aim was to compare the effectiveness of NIC versus SNP in the management of hypertension after cardiac surgery and evaluate the influence of drug choice on postoperative costs.

Methods

We conducted a retrospective, cohort study using our hospital's financial and electronic medical records. Adults admitted to a cardiothoracic surgical intensive care unit after coronary artery bypass grafting (CABG) and/or valve surgery who developed hypertension requiring ≥30 minutes of NIC or SNP were included. We evaluated drug effectiveness by assessing infusion rate stability, blood pressure and heart rate, and concomitant antihypertensive agent use. Activity-based postoperative costs were compared between study groups.

Results

One hundred twelve subjects were included (NIC = 72, SNP = 40). Hypertension-related demographics were balanced between the groups. NIC was associated with improved infusion rate stability that required fewer dose changes per hour (1.2 ± 1.6) versus SNP (1.7 ± 1.8) ( P = .004). Heart rates and blood pressures did not differ significantly. The number of antihypertensive medications used before and during the NIC or SNP infusions was the same. However, persons who were prescribed SNP required significantly more medications to manage blood pressure after infusions were discontinued ( P = .001). NIC use did not significantly increase postoperative cost. NIC use may be associated with cost increases in isolated CABG but with cost savings in isolated valve or combined CABG/valve surgeries; however, these differences were not statistically significant.

Conclusions

Blood pressure was equally controlled using NIC or SNP. NIC was associated with improved infusion rate stability. Despite a higher acquisition cost, NIC did not significantly influence postoperative costs. Larger, prospective cost-effective analyses in surgical subgroups are needed.

The acute hemodynamic effects of MitraClip therapy

OBJECTIVES

The objective of this study was to evaluate the acute hemodynamic consequences of mitral valve (MV) repair with the MitraClip device (Abbott Vascular, Menlo Park, California).

BACKGROUND

Whether surgical correction of mitral regurgitation (MR) results in a low cardiac output (CO) state because of an acute increase in afterload remains controversial. The acute hemodynamic consequences of MR reduction with the MitraClip device have not been studied.

METHODS

We evaluated 107 patients with cardiac catheterization before and immediately following percutaneous MV repair with the MitraClip device. In addition, pre- and post-procedural hemodynamic parameters were studied by transthoracic echocardiography.

RESULTS

MitraClip treatment was attempted in 107 patients, and in 96 (90%) patients, a MitraClip was deployed. Successful MitraClip treatment resulted in: 1) an increase in CO from 5.0 ± 2.0 l/min to 5.7 ± 1.9 l/min (p = 0.003); 2) an increase in forward stroke volume (FSV) from 57 ± 17 ml to 65 ± 18 ml (p < 0.001); and 3) a decrease in systemic vascular resistance from 1,226 ± 481 dyn·s/cm(5) to 1,004 ± 442 dyn·s/cm(5) (p < 0.001). In addition, there was left ventricular (LV) unloading manifested by a decrease in LV end-diastolic pressure from 11.4 ± 9.0 mm Hg to 8.8 ± 5.8 mm Hg (p = 0.016) and a decrease in LV end-diastolic volume from 172 ± 37 ml to 158 ± 38 ml (p < 0.001). None of the patients developed acute post-procedural low CO state.

CONCLUSIONS

Successful MV repair with the MitraClip system results in an immediate and significant improvement in FSV, CO, and LV loading conditions. There was no evidence of a low CO state following MitraClip treatment for MR. These favorable hemodynamic effects with the MitraClip appear to reduce the risk of developing a low CO state, a complication occasionally observed after surgical MV repair for severe MR.

Postoperative Care of the Cardiac Surgical Patient

The subspecialty of interventional cardiology began in 1977. Since then, the discipline of interventional cardiology has matured rapidly, particularly with regards to ischemic heart disease. As a result, more patients are undergoing percutaneous catheter interventional therapy for ischemic heart disease and fewer patients are undergoing surgical myocardial revascularization. Those patients referred for surgical revascularization are generally older and have more complex problems. Furthermore, as the population ages more patients are referred to surgery for valvular heart disease. The result of these changes is a population of surgical patients older and sicker than previously treated.

Secondary hypertension: current diagnosis and treatment

Secondary hypertension affects a small but significant number of the hypertensive population and, unlike primary hypertension, is a potentially curable condition. The determinant for workup is dependent on the index of suspicion elicited during patient examination and treatment. Specific testing is available and must be balanced depending on the risk and cost of the workup and treatment with the benefits obtained if the secondary cause is eliminated. This article reviews common manifestations, workup, and the current treatments of the common causes of secondary hypertension.

Hypertensive crisis: hypertensive emergencies and urgencies

Hypertensive crisis is a serious condition that is associated with end-organ damage or may result in end-organ damage if left untreated. Causes of acute rises in blood pressure include medications,noncompliance, and poorly controlled chronic hypertension. Treatment of a hypertensive crisis should be tailored to each individual based on the extent of end-organ injury and comorbid conditions. Prompt and rapid reduction of blood pressure under continuous surveillance is essential in patients who have acute end-organ damage.

Intrathecal and Epidural Anesthesia and Analgesia for Cardiac Surgery

Adequate postoperative analgesia prevents unnecessary patient discomfort. It may also decrease morbidity, postoperative hospital length of stay and, thus, cost. Achieving optimal pain relief after cardiac surgery is often difficult. Many techniques are available, and all have specific advantages and disadvantages. Intrathecal and epidural techniques clearly produce reliable analgesia in patients undergoing cardiac surgery. Additional potential benefits include stress response attenuation and thoracic cardiac sympathectomy. The quality of analgesia obtained with thoracic epidural anesthetic techniques is sufficient to allow cardiac surgery to be performed in awake patients without general endotracheal anesthesia. However, applying regional anesthetic techniques to patients undergoing cardiac surgery is not without risk. Side effects of local anesthetics (hypotension) and opioids (pruritus, nausea/vomiting, urinary retention, and respiratory depression), when used in this manner, may complicate perioperative management. Increased risk of hematoma formation in this scenario has generated much of lively debate regarding the acceptable risk-benefit ratio of applying regional anesthetic techniques to patients undergoing cardiac surgery.

Hemodynamic management of patients in the first 24 hours after cardiac surgery

OBJECTIVE

To describe the physiologic alterations, evaluation, and hemodynamic management of patients in the first 24 hrs after cardiac surgery.

DESIGN

A brief review of preoperative and intraoperative events, postoperative physiology, and a discussion of the evaluation and hemodynamic management of cardiac surgery patients postoperatively based on a review of the literature, known physiology, and clinical experience.

RESULTS

After cardiac surgery, patients undergo alterations in cardiac performance related to co-morbid conditions, preoperative myocardial insults and interventions, the surgical procedure, and intraoperative management. Predictable responses evolve rapidly in the first 24 hrs after surgery. Monitoring, diagnostic regimens, and therapeutic regimens exist to address the patterns of response and occasional complications.

CONCLUSION

By understanding preoperative and intraoperative events and their evolution in the intensive care unit, clinicians can effectively manage patients who experience cardiac surgery.

Comparison of the Effects of Nicardipine and Sodium Nitroprusside for Control of Increased Blood Pressure after Coronary Artery Bypass Graft Surgery

We compared the haemodynamic effects of nicardipine and sodium nitroprusside after coronary artery bypass graft surgery. When post-surgery systolic blood pressure reached > 150 mmHg, patients were randomly given nicardipine (N group, n = 26) or sodium nitroprusside (S group, n = 21). The drugs were infused at a rate of 2 μg/kg per min for 10 min. If the target blood pressure (120-140 mmHg) was not achieved, the infusion rate was increased by 1 üg/kg per min every 10 min. Cardiac and stroke volume indices had increased significantly in the N group after 10 min and in both groups after 60 min. The infusion duration and total dose of drug were significantly lower in the N group compared with the S group. Nicardipine infusion controlled post-operative hypertension more rapidly and was superior to sodium nitroprusside in maintaining left ventricular performance immediately after drug infusion.

Blood pressure and heart rate variability changes during cardiac surgery with cardiopulmonary bypass

This study investigated patients undergoing elective cardiac surgery to evaluate the effects of cardiopulmonary bypass (CPB) on the spontaneous variability of mean arterial pressure (MAP) and heart rate (HR). Forty-one adult patients receiving different cardiovascular system drugs were included in the study. Patients were divided into three groups: no preoperative pharmacological cardiovascular treatment (n = 12), beta-blocker (BB) (n = 13), and angiotensin-converting enzyme inhibition (ACEI) (n = 16). MAP was recorded before anaesthesia until the end of surgery. MAP and HR variability was analysed in very low- (VLF), low- (LF) and high-frequency bands. The LF spectral component of MAP was observed to decrease in patients under ACEI (-92%) or BB (-87%) following induction of anaesthesia. In addition, during CPB, VLF power decreased in BB group (-67%), and LF power decreased in ACEI group (-77%). Concerning HR, VLF spectral power decreased following anaesthesia in BB group (-74%). In addition, after CPB, VLF power reached lower value in ACEI group than in BB group (P < 0.05). LF spectral power of HR showed a large decrease after CPB in ACEI group (-89%). This study showed that MAP variability did not change during CPB in patients with no preoperative pharmacological cardiovascular treatment, suggesting an unaltered vascular control of MAP. Moreover, the change in LF spectral power of MAP in ACEI and BB groups, suggests that both the renin-angiotensin and sympathetic systems participate to the genesis of LF variability of MAP.

Nicardipine versus Nitroprusside Infusion as Antihypertensive Therapy in Hypertensive Emergencies

This prospective study compared the efficacy of nicardipine and nitroprusside for treating hypertensive emergencies by measuring haemodynamic indices and serum catecholamine levels. Patients admitted to the emergency department with a hypertensive crisis and acute pulmonary oedema received intravenous infusions of nitroprusside (starting dose 1 μg/kg per min, n = 20) or nicardipine (starting dose 3 μg/kg per min, n = 20). Both groups experienced significant declines in systolic and diastolic blood pressure after treatment, but there were no significant time-dependent differences between the groups. Heart rate decreased in the nicardipine group and increased in the nitroprusside group, but neither change was significant. Respiration rate decreased and capillary oxygen saturation rate increased after treatment in both groups. Adrenaline and noradrenaline levels decreased significantly after treatment in both groups; noradrenaline levels were significantly decreased in the nicardipine-treated group compared with the nitroprusside-treated group. Injectable nicardipine is easy to use and as effective as nitroprusside for treating hypertensive crisis with acute pulmonary oedema.

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.

Risk factors for post-cardiopulmonary bypass vasoplegia in patients with preserved left ventricular function

BACKGROUND

Although vasodilatory shock (VS) is one of the main complications of cardiopulmonary bypass (CPB), its pathophysiologic basis remains unclear. The aim of this study was to identify predisposing factors for the development of VS after CPB independent of ventricular function.

METHODS

Thirty-six patients undergoing coronary artery bypass grafting who developed VS were compared with 72 control patients without post-CPB cardiogenic or vasoplegic shock, in a 2:1 case control study. Patients and controls underwent the same anesthetic protocol and were matched by age, sex, operation date, and left ventricle ejection fraction.

RESULTS

Preoperative and intraoperative patient characteristics were not significantly different between the two groups. Preoperative use of angiotensin-converting enzyme inhibitors and intravenous heparin were independent predictors for post-CPB VS by multivariate analysis (relative risk of 2.26 and 2.78, respectively). Intensive care unit stay and hospital stay were significantly longer in VS cases than controls, without any difference in early postoperative mortality.

CONCLUSIONS

The only independent risk factors for postoperative VS identified were preoperative use of angiotensin-converting enzyme inhibitors and intravenous heparin. These risk factors were independent of age, gender, anesthetic protocol, and left ventricle ejection fraction.

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.

The effect of i.v. enalaprilat in chronically treated hypertensive patients during cardiac surgery

BACKGROUND

Angiotensin-converting enzyme (ACE) inhibitors are well established as long-term antihypertensives and have also been proved useful in hypertensive emergencies. Therefore, we investigated whether intraoperative i.v. enalaprilat may reduce the incidence of perioperative hypertensive reactions in coronary artery bypass grafting (CABG).

METHODS

Thirty-eight male patients chronically treated for arterial hypertension and scheduled for CABG randomly and double-blindly received either enalaprilat 30 micrograms.kg-1 or NaCl 0.9% at the time of skin incision. Intraoperatively, increases of mean arterial pressure (MAP) > 85 mmHg or > 80 mmHg during cardiopulmonary bypass (CPB) were treated by an urapidil bolus. The total intraoperative amount of urapidil was documented for both groups. Systemic and pulmonary hemodynamics as well as the plasma levels of epinephrine, norepinephrine, arginine vasopressin and renin were measured intraoperatively and up to 2 h after admission to the intensive care unit.

RESULTS

Mean arterial pressure, cardiac index and systemic vascular resistance did not differ between the enalaprilat and the control group. Renin plasma levels significantly increased after infusion of enalaprilat and did not change in the placebo group. Catecholamine and arginine vasopressin plasma levels increased significantly during CPB and remained high in the postoperative period without any intergroup difference. The same amount of urapidil had to be given in the two groups to maintain MAP below the defined limit.

CONCLUSION

We conclude that infusing 30 micrograms.kg-1 enalaprilat in patients chronically treated for arterial hypertension does not prevent hypertensive reactions during CABG.

Basic and clinical aspects of myocardial stunning

Although the pathogenesis of myocardial stunning has not been definitively established, the two major hypotheses are that it is caused by the generation of oxygen-derived free radicals on reperfusion and by a loss of sensitivity of contractile filaments to calcium. These hypotheses are not mutually exclusive and are likely to represent different facets of the same pathophysiological cascade. For example, a burst of free radical generation after reperfusion could alter contractile filaments in a manner that renders them less responsive to calcium. Increased free radical formation could also cause cellular calcium overload, which would damage the contractile apparatus of the myocytes. There is now considerable evidence that myocardial stunning occurs clinically in various situations in which the heart is exposed to transient ischemia, such as unstable angina, acute myocardial infarction with early reperfusion, exercise-induced ischemia, cardiac surgery, and cardiac transplantation. Recognition of myocardial stunning is clinically important and may impact patient treatment. Although no ideal diagnostic technique for myocardial stunning has yet been developed, thallium-201 scintigraphy or dobutamine echocardiography are available and can be useful to identify viable myocardium with reversible wall motion abnormalities. An intriguing possibility is that so-called chronic hibernation may in fact be the result of repetitive episodes of stunning, which have a cumulative effect and cause protracted postischemic left ventricular dysfunction. A better understanding of myocardial stunning will expand our knowledge of the pathophysiology of myocardial ischemia and provide a rationale for developing new therapeutic strategies designed to prevent postischemic dysfunction.

Effect of antihypertensive agents on the arterial partial pressure of oxygen and venous admixture after cardiac surgery

OBJECTIVE

To determine whether stopping nitroglycerin and sodium nitroprusside (both vasodilators) infusions in hypertensive, postcardiac surgical patients requiring a high FIO2 improves PaO2 and venous admixture.

DESIGN

Prospective, clinical trial.

SETTING

Intensive care unit in a university-affiliated hospital.

PATIENTS

Thirty postcardiac surgical patients who, because of high FIO2 requirements, did not meet the criteria for weaning from mechanical ventilation and who were receiving infusions of nitroglycerin and/or sodium nitroprusside to control blood pressure.

INTERVENTIONS

PaO2, venous admixture, and oxygen transport data were determined at baseline using arterial and mixed venous blood gas samples and hemodynamic values from a pulmonary artery catheter. The nitroglycerin and sodium nitroprusside infusions were stopped, and intravenous boluses of labetalol were administered to maintain a target blood pressure. After the vasodilator infusions were stopped, the baseline measurements were repeated to redetermine PaO2, venous admixture, and oxygen transport values.

MEASUREMENTS AND MAIN RESULTS

Results included a mean increase in PaO2 from 79.3 +/- 15 torr (10.5 +/- 2.0 kPa) to 118.3 +/- 38 torr (15.7 +/- 5.1 kPa) and a mean decrease in venous admixture from 26.4 +/- 5.8% to 17.6 +/- 5.6% when the vasodilators were stopped. All 30 patients had an increase in PaO2 and a decrease in venous admixture. Because of the improvement in oxygenation, 28 of the 30 patients met the criteria for weaning from mechanical ventilation once nitroglycerin and sodium nitroprusside were stopped or decreased. Labetalol was well tolerated in this group of patients who had preserved ventricular function.

CONCLUSIONS

Substituting labetalol for nitroglycerin and sodium nitroprusside improves arterial oxygenation and venous admixture in hypertensive postcardiac surgical patients who require a high FIO2. This change in therapy may allow patients to be weaned from mechanical ventilation sooner.

A randomized multicenter double-blind comparison of urapidil and ketanserin in hypertensive patients after coronary artery surgery

OBJECTIVES

To compare the hemodynamic responses, safety, and efficacy of urapidil and ketanserin in hypertensive patients after coronary artery surgery.

DESIGN

Randomized double-blind study.

SETTING

Multi-institutional.

PARTICIPANTS

One hundred twenty-two patients undergoing elective coronary artery surgery.

INTERVENTIONS

When hypertension (defined as mean arterial pressure > 85 mmHg) developed within the first 2 hours after arrival in the intensive care unit, patients received urapidil (n = 62) or ketanserin (n = 60) to reach a mean arterial pressure between 65 and 75 mmHg. Urapidil was administered by repeated bolus injections (25 to 125 mg) followed by a continuous infusion of maximally 50 micrograms/kg/min. Ketanserin was administered by repeated bolus injections (10 to 50 mg) followed by a continuous infusion of maximally 4.0 micrograms/kg/min.

MEASUREMENTS AND MAIN RESULTS

A complete hemodynamic profile was determined at baseline and at 30 and 60 minutes after start of study medication. In the urapidil group, mean arterial pressure (+/-SD) decreased significantly from 100.6 +/- 12.4 mmHg at baseline to 74.6 +/- 12.1 mmHg at 30 minutes and 73.5 +/- 13.8 mmHg at 60 minutes. In the ketanserin group, mean arterial pressure decreased significantly from 98.7 +/- 10.7 mmHg at baseline to 83.5 +/- 16.8 mmHg at 30 minutes and 83.1 +/- 15.3 mmHg at 60 minutes. Between the groups, there was a significant difference in the degree of lowering mean arterial pressure at 30 and 60 minutes. Heart rate increased significantly by 5.8 +/- 12.7 (30 minutes) and 8.6 +/- 16.5 (60 minutes) beats/min in the ketanserin group. In the urapidil group, no changes in heart rate occurred. Cardiac output increased to the same extent (0.7 L/min) in both groups. Within and between the groups, there were no relevant changes in pulmonary filling pressures. The number of patients not responding adequately to the study medication (mean arterial pressure > 85 mmHg after 30 minutes despite the maximum doses of study medication) was comparable in both groups (9 [U] v 13 [K]). Adverse events attributable to the study medication occurred to a similar degree in both groups. In the patients treated with urapidil, a significantly higher incidence (32.3%) of hypotension (mean arterial pressure < or = 65 mmHg for more than 10 minutes) occurred after 60 minutes of continuous infusion.

CONCLUSIONS

In contrast to ketanserin, urapidil did not increase heart rate. Urapidil was more effective in lowering arterial blood pressure than ketanserin. However, one third of the patients treated with urapidil developed hypotension after 60 minutes of continuous infusion.

Myocardial circulatory and metabolic effects of atrial natriuretic peptide after coronary artery bypass grafting

The purpose of this study was to examine the effects of incremental infusion rates of human atrial natriuretic peptide (ANP), 25, 50, 100 ng.kg-1. min-1, on myocardial blood flow and metabolism (n = 10), and to compare the effects of ANP on these variables with those of equipotent infusion rates of sodium nitroprusside (SNP) (n = 9) 1-3 h after coronary artery bypass grafting (CABG). ANP induced a dose-dependent decrease in mean arterial blood pressure and systemic vascular resistance. There were no changes in cardiac index, heart rate, or cardiac filling pressures. ANP caused no changes in myocardial blood flow or its distribution, and caused no changes in myocardial oxygen extraction. Regional myocardial lactate uptake (RMLU) and extraction (RMLE) increased significantly (P < 0.05) at 50 ng.kg-1.min-1 (10.2 +/- 3.8 mumol/min and 8.2% +/- 3.0%, respectively) as compared to control (-1.1 +/- 3.0 mumol/min and -1.3% +/- 3.3%, respectively). RMLE and RMLU were significantly (P < 0.05) higher with ANP (5.7% +/- 2.5% and 6.8 +/- 3.7 mumol/min, respectively) compared to SNP (-1.5% +/- 2.1% and -0.1 +/- 3.7 mumol/min, respectively). We conclude that ANP has no dilatory effects on coronary vascular resistance vessels and thus lacks the potential to maldistribute flow, and that ANP improves myocardial lactate metabolism after CABG.

Effects of prostacyclin on myocardial hemodynamics and metabolism after coronary artery bypass grafting

OBJECTIVE

To study the effects of incremental infusion rates of prostacyclin on myocardial blood flow and metabolism and central hemodynamics shortly after coronary artery bypass grafting.

DESIGN

A pharmacodynamic dose-response study.

SETTING

A multi-institutional university hospital.

PARTICIPANTS

Twelve patients with two- or three-vessel coronary artery disease and with an ejection fraction greater than 0.5 were studied in the operating room after sternal closure and elective coronary artery bypass grafting.

INTERVENTIONS

Prostacyclin was administered at infusion rates of 2.5, 5, 10, and 20 ng/kg/min. Systemic and pulmonary hemodynamics and global (coronary sinus) as well as regional (great cardiac vein) myocardial blood flow and metabolic variables were measured.

MEASUREMENTS AND MAIN RESULTS

Infusion rates of 10 and 20 ng/kg/min decreased mean arterial blood pressure (13% and 21%, respectively), systemic vascular resistance (31% and 42%), and pulmonary vascular resistance (11% and 33%), increased cardiac output (28% and 37%), heart rate (9% and 13%), and stroke volume (15% and 20%), but had no effect on central filling pressures. Prostacyclin caused no changes in great cardiac vein flow or coronary sinus flow. Furthermore, prostacyclin caused no changes in regional myocardial oxygen extraction, indicating that prostacyclin did not induce direct coronary vasodilation. There were no electrocardiographic or obvious metabolic signs of myocardial ischemia during prostacyclin infusion.

CONCLUSION

Prostacyclin may be a useful afterload-reducing compound after coronary artery bypass grafting because it has no direct coronary vasodilatory effect, which minimizes the risk of myocardial ischemia.

Large-dose intrathecal morphine for coronary artery bypass grafting

Aggressive control of pain during the immediate postoperative period after cardiac surgery, associated with decreased blood catecholamine levels, may decrease morbidity and mortality. This study investigated the use of large-dose intrathecal morphine for cardiac surgery and its effect on postoperative analgesic requirements and blood catecholamine levels. Patients were randomized to receive either 4.0 mg of intrathecal morphine (Group MS) or intrathecal saline placebo (Group NS). Perioperative care was standardized and included postoperative patient-controlled analgesia. Arterial blood samples were obtained perioperatively to ascertain catecholamine levels. Patients in Group MS required significantly less postoperative intravenous morphine than patients in Group NS. Although perioperative norepinephrine and epinephrine levels in Group MS patients tended to be lower than Group NS patients, the differences were not statistically significant. In conclusion, large-dose intrathecal morphine initiates reliable postoperative analgesia but does not reliably attenuate the stress response during and after cardiac surgery.

Use of calcium channel antagonists in myocardial revascularization procedures

Calcium channel antagonists possess a number of properties that may be beneficial after revascularization procedures. Therefore, we present an overview of the use of these drugs after percutaneous intervention in the Coronary Angioplasty Versus Excisional Atherectomy Trial (CAVEAT), and compare the results in CAVEAT with those in published randomized trials. Also reviewed are the use of calcium channel antagonists to control perioperative hypertension, reduce myocardial necrosis, and prevent arrhythmias during cardiopulmonary bypass.

Sodium nitroprusside after cardiac surgery: systemic and splanchnic blood flow and oxygen transport

BACKGROUND

Vasoactive drugs may interfere with splanchnic blood flow and tissue oxygenation. Sodium nitroprusside (SNP) is widely used in the treatment of postoperative hypertension after cardiac surgery, but the effects of SNP and other vasodilators on splanchnic blood flow have not been well documented.

METHODS

The effects of SNP on systemic blood flow, oxygen transport and gastric intramucosal pH (pHi) were studied in 12 patients with arterial hypertension after coronary artery bypass grafting. In 9 of these patients, the effect on regional (splanchnic and leg) blood flow and oxygen transport was also measured. Hemodynamic and regional blood flow responses were measured before and during SNP infusion (mean 2.8 +/- 1.7 micrograms/kg/min, range 0.6-6.3 micrograms/kg/min), when the goal of the vasodilator treatment, mean arterial pressure 70-80 mmHg, had been reached.

RESULTS

SNP increased splanchnic (0.65 +/- 0.22 vs. 0.87 +/- 0.37 L.min-1.m-2, P < 0.01) and femoral blood flow (0.15 +/- 0.04 vs. 0.21 +/- 0.06 L.min-1.m-2, P < 0.05) in parallel with cardiac index (2.6 +/- 0.6 vs. 3.3 +/- 0.7 L.min-1.m-2, P < 0.01). Fractional regional blood flows did not change. Mean gastric intramucosal pH decreased slightly (7.40 +/- 0.07 vs. 7.37 +/- 0.06, P < 0.05). Both systemic (420 +/- 85 vs. 495 +/- 90 mL.min-1.m-2, P < 0.05) and femoral oxygen delivery (25 +/- 5 vs. 32 +/- 10 mL.min-1.m-2, P < 0.05) increased, but neither systemic nor regional oxygen consumption changed.

CONCLUSIONS

These results suggest that vasoregulation is well preserved during treatment of early postoperative hypertension with SNP, and that SNP has no adverse effects on splanchnic tissue oxygenation.

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.

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.

The renin-angiotensin system and angiotensin converting enzyme (ACE) inhibitors

Anaesthetists will encounter increasing numbers of patients who are receiving long-term treatment with ACE inhibitors for hypertension, congestive heart failure and prophylactically following myocardial infarction. Our understanding of the physiology and pharmacology of the renin-angiotensin system has dramatically increased in the last decade, and has led to the discovery of endogenous renin-angiotensin systems which may be physiologically more important than the better understood circulating system. There are several reports of adverse interactions between anaesthesia and ACE inhibitors, manifested as hypotension and bradycardia, which may be delayed until the postoperative period. The mechanism behind them is not understood and, as yet, no published studies have attempted to address this issue. It is possible, however, that dehydration associated with the pre-operative fast may play an important role. ACE inhibitors may, in the future, prove to be useful in the subspecialties of cardiac and vascular anaesthesia, where they might be used in an attempt to preserve cardiac function following periods of ischaemia and cardiopulmonary bypass, and to avoid renal damage following aortic cross-clamping. Meanwhile, it would seem prudent to exercise caution when anaesthetising patients taking ACE inhibitors and to be fully prepared to treat the hypotension and bradycardia which may occur.

Use of ketanserin in the treatment of hypertension following coronary artery surgery

Ketanserin, a selective S2-serotonin receptor blocker with alpha 1-adrenergic blocking effects, may be a suitable antihypertensive medication after coronary artery surgery and lacks side effects seen with other vasodilators. Fifty patients with systolic blood pressures greater than 150 mmHg after coronary artery surgery were given, in a randomized double-blind fashion, either ketanserin (K) or saline (S). Each patient received six successive boluses of 1 mL of S or 1 mL of K (5 mg) at 2-minute intervals. After the last injection, sodium nitroprusside was started whenever the systolic blood pressure exceeded 150 mmHg. In the K group, the following significant (P < 0.05) changes occurred: systolic and diastolic arterial pressure -12% and -11%, respectively; heart rate -3%; systolic and diastolic pulmonary artery pressure -5% and -6%; central venous pressure -5%; pulmonary capillary wedge pressure -5%; systemic vascular resistance -16%; pulmonary vascular resistance -8%; stroke index +6%. None of these parameters changed significantly in the S group. There was no change in pulmonary shunt fraction in either group. In the K group, five patients did not require any further antihypertensive therapy during the 120 minutes following the last bolus injection. Twenty patients needed sodium nitroprusside during this period. This occurred 37 minutes (+/- 17 min) after the last bolus. In conclusion, after coronary artery bypass surgery, K is an effective antihypertensive medication, which does not cause reflex tachycardia or an increase in pulmonary shunt fraction. Exceeding the recommended dose of 10 (or 20) mg, as done in this study, does not seem to improve effectiveness or prolong the duration of action.

Central hemodynamics and right ventricular function after coronary artery bypass surgery. A comparison of prostacyclin, sodium nitroprusside, and nitroglycerin for treatment of postcardiac surgical hypertension

The aim of this study was to compare the effects of prostacyclin on central hemodynamics and right ventricular function to the more widely used vasodilators sodium nitroprusside (SNP) and nitroglycerin (NTG), and to investigate whether prostacyclin is more selective to the pulmonary vascular bed compared to SNP and NTG after coronary artery bypass surgery. Twelve patients with two-vessel or three-vessel coronary artery disease and an ejection fraction > 0.5 were included. Hemodynamic measurements were made postoperatively in the intensive care unit using a pulmonary artery fast-response ejection fraction/volumetric thermodilution catheter. The aim was to control and maintain mean arterial blood pressure around 75 to 80 mmHg with each drug. After a 10-minute infusion of each drug at a stable infusion rate, central hemodynamic variables as well as right ventricular end-diastolic volume (RVEDV), end-systolic volume (RVESV) and ejection fraction (RVEF) were measured or derived in triplicate. The average infusion rates of SNP, NTG, and prostacyclin were 2.3 +/- 0.8 micrograms/kg/min, 12.6 +/- 6.0 micrograms/kg/min and 20.0 +/- 0.5 ng/kg/min, respectively. Cardiac output, stroke volume, RVEDV, and central filling pressures were highest for prostacyclin compared to both NTG and SNP. Systemic vascular resistance (SVR) was lowest for prostacyclin but the effects on pulmonary vascular resistance (PVR) were comparable to that of SNP. The PVR/SVR ratio was significantly lower with both SNP and NTG when compared to prostacyclin. RVEF did not differ among the three drugs.(ABSTRACT TRUNCATED AT 250 WORDS)