Predictors and outcomes of cardiac complications following elective coronary bypass grafting.

Our objective was to determine the predictors of cardiac complications among a cohort of elective coronary artery bypass graft (CABG) surgery patients and to determine the relationship of such complications to subsequent quality of life and symptoms. A total of 248 patients were enrolled and 237 completed 6 month follow-up. The combined rate of both major and minor cardiac complications was 9.7% (n = 24). Patients in this study were evaluated preoperatively, monitored intraoperatively, followed immediately postoperatively and at 6 months. Major cardiac complications accounted for 3.6% (n = 9) and minor complications for 6% (n = 15). Using multivariable logistic regression analysis, the predictors of major cardiac complications were receiving diuretics preoperatively (p = .01) and increased time during cross-clamping (p = .006). At 6 months after surgery, 19% of the patients with postoperative cardiac complications experienced worsening of symptoms, in contrast to only 8% of those without cardiac complications (p = .03). We concluded that patients who were on preoperative diuretics and those who had longer cross-clamp times were at higher risk of cardiac complications. The majority of patients who had acute cardiac complications had improved function and symptoms at 6 months postoperatively.

Retrograde autologous priming for cardiopulmonary bypass: a safe and effective means of decreasing hemodilution and transfusion requirements.

OBJECTIVES: The obligatory hemodilution resulting from crystalloid priming of the cardiopulmonary bypass circuit represents a major risk factor for blood transfusion in cardiac operations. We therefore examined whether retrograde autologous priming of the bypass circuit would result in decreased hemodilution and red cell transfusion. METHODS: Sixty patients having first-time coronary bypass were prospectively randomized to cardiopulmonary bypass with or without retrograde autologous priming. Retrograde autologous priming was performed at the start of bypass by draining crystalloid prime from the arterial and venous lines into a recirculation bag (mean volume withdrawal: 880 +/- 150 ml). Perfusion and anesthetic techniques were otherwise identical for the two groups. The hematocrit value was maintained at a minimum of 16% and 23% during and after cardiopulmonary bypass, respectively, in all patients. Patients were well matched for all preoperative variables, including established transfusion risk factors. Subsequent hemodynamic parameters, pressor requirements, and fluid requirements were equivalent in the two groups. RESULTS: The lowest hematocrit value during cardiopulmonary bypass was 22% +/- 3% versus 20% +/- 3% in patients subjected to retrograde autologous priming and in control patients, respectively (p = 0.002). One (3%) of 30 patients subjected to retrograde autologous priming had intraoperative transfusion, and seven (23%) of 30 control patients required transfusion during the operation (p = 0.03). The number of patients receiving any homologous red cell transfusions in the two groups during the entire hospitalization was eight of 30 (27%; retrograde autologous priming) versus 16 of 30 (53%; control) (p = 0.03). CONCLUSIONS: These data suggest that retrograde autologous priming is a safe and effective means of significantly decreasing hemodilution and the number of patients requiring red cell transfusion during cardiac operations.

Cardiac operations in patients with cirrhosis.

BACKGROUND: A retrospective review was performed to determine the outcome after cardiac operations in patients with a documented history of noncardiac cirrhosis. METHODS: The charts of patients admitted to the cardiothoracic surgical service between 1990 and 1996 were reviewed, and 13 patients with a preoperative history of cirrhosis were identified. The severity of preoperative liver disease was graded according to the criteria of Child. RESULTS: Most of the cases of cirrhosis were alcohol-related. Eight patients were classified as having Child class A and 5 as having Child class B cirrhosis. One hundred percent of patients with Child class B and 25% of those with Child class A cirrhosis had major complications. The postoperative chest tube output and transfusion requirements of these patients were approximately three times higher than average. The overall perioperative mortality rate was 31%. In patients with Child class B cirrhosis, the mortality rate was 80%. No patient with Child class A cirrhosis died. Deaths were related to gastrointestinal and septic complications, and not to cardiovascular failure. CONCLUSIONS: These findings suggest that patients with minimal clinical evidence of cirrhosis can tolerate cardiopulmonary bypass and cardiac surgical procedures, whereas those with more advanced liver disease should not be offered operation.

Comprehensive multimodality blood conservation: 100 consecutive CABG operations without transfusion.

BACKGROUND: Despite the recent introduction of a number of technical and pharmacologic blood conservation measures, bleeding and allogeneic transfusion remain persistent problems in open heart surgical procedures. We hypothesized that a comprehensive multimodality blood conservation program applied algorithmically on the basis of bleeding and transfusion risk would provide a maximum, cost-effective, and safe reduction in postoperative bleeding and allogeneic blood transfusion. METHODS: One hundred consecutive patients undergoing coronary artery bypass grafting were prospectively enrolled in a risk factor-based multimodality blood conservation program (MMD group). To evaluate the relative efficacy and safety of this comprehensive approach, comparison was made with a similar group of 90 patients undergoing coronary artery bypass grafting to whom the multimodality blood conservation program was not applied but in whom an identical set of transfusion guidelines was enforced (control group). To evaluate the cost effectiveness of the multimodality program, comparison was also made between patients in the MMD group and a consecutive series of contemporaneous, diagnostic-related group-matched patients. RESULTS: One hundred consecutive patients in the MMD group underwent coronary artery bypass grafting without allogeneic transfusion. This compared favorably with the control population in whom a mean of 2.2 +/- 6.7 units of allogeneic blood was transfused per patient (34 patients [38%] received transfusion). In addition, the volume of postoperative blood loss at 12 hours in the control group was almost double that of the MMD group (660 +/- 270 mL versus 370 +/- 180 mL [p < 0.001]). Total costs for the MMD group in each of the three major diagnostic-related groups were equivalent to or significantly less than those in the consecutive series of diagnostic-related group-matched patients. CONCLUSIONS: Comprehensive risk factor-based application of multiple blood conservation measures in an optimized, integrated, and algorithmic manner can significantly decrease bleeding and need of allogeneic transfusion in coronary artery bypass grafting in a safe and cost-effective manner.

Outcome analysis of 245 CarboMedics and St. Jude valves implanted at the same institution.

BACKGROUND: Thromboembolism and valve-related death are major complications associated with prosthetic valve implants, but it is difficult to evaluate the relative incidence of these complications based on studies in which the implantation of only one valve is reported from any given institution. We therefore report the outcome of patients implanted at our institution during the same time period with either the recently released CarboMedics (CM) or the St. Jude Medical (SJ) valve prostheses. METHODS: Between October 1994 and January 1996, 245 consecutive patients received either SJ (116 patients) or CM (129 patients) valves at our institution. Follow up of these patients was 99.6% complete, for a total of 318.5 cumulative patient-years (median follow-up, 1.4 years). RESULTS: The 30-day mortality rates for SJ and CM implants were 3.4% and 3.1%, respectively. Actuarial survival and freedom from valve related mortality rates at 1.5 years for SJ and CM valves were 94%+/-2% versus 86%+/-3% (p = 0.03) and 100% versus 94%+/-2% (p = 0.005), respectively. There was no structural valve failure for either implant, but there were five thrombosed valves in the CM group and none in the SJ group (p = 0.04). All thrombosed valves were mitral (four mitral valve replacement, one aortic and mitral valve replacement). Two of the thrombosed valves were successfully explanted, whereas the three remaining patients died. Freedom from a thromboembolic event in the mitral position at 1.5 years, including thrombosed valves was 97%+/-3% and 83%+/-5% for SJ and CM valves, respectively (p = 0.04). CONCLUSIONS: The results of this study suggest that further evaluation of thromboembolic outcomes after CM compared with SJ valve implantation is warranted.

Impact of minimum hematocrit during cardiopulmonary bypass on mortality in patients undergoing coronary artery surgery.

BACKGROUND: The hematocrit on cardiopulmonary bypass (CPB) frequently falls to a low level during many cardiac surgical procedures. This study was designed to explore the impact on mortality of minimum hematocrit level achieved during the CPB after coronary artery surgery. METHODS AND RESULTS: Two thousand seven hundred thirty-eight sequential isolated coronary artery surgery patients during a 42-month period at a tertiary academic center were included in this study. Thirty-one standardized preoperative risk factors used in a multiple logistic regression revealed eight statistically significant independent predictors for postoperative mortality. Minimum hematocrit level during CPB was then added to the regression model and was found to be an independent risk factor for mortality. The entire patient population was divided into dichotomous groups using different minimum hematocrit levels on CPB for the determination of cutoff points by multiple logistic regression. After adjusting for other risk factors, the minimum hematocrit level of 14% was found to be a statistically significant cutoff point. Patients with minimum hematocrit levels < or =14% were found to have an increased probability of risk-adjusted mortality (odds ratio, 2.70; P=.002). A subgroup analysis revealed that high-risk patients with minimum hematocrit levels < or =17% were found to have a significantly increased probability of postoperative mortality (odds ratio, 2.20; P=.017). CONCLUSIONS: Minimum hematocrit level during CPB is an independent risk factor for mortality after coronary artery surgery. There is a significantly increased risk of mortality for hematocrit levels < or =14%. For high-risk patients, there is a significantly increased risk of mortality for hematocrit levels < or =17%.

Open heart operations without transfusion using a multimodality blood conservation strategy in 50 Jehovah's Witness patients: implications for a "bloodless" surgical technique.

BACKGROUND: Blood transfusion persists as an important risk of open heart operations despite the recent introduction of a variety of new pharmacologic agents and blood conservation techniques as independent therapies. A comprehensive multimodality blood conservation program was developed to minimize this risk. STUDY DESIGN: To provide a strategy for operating without transfusion, this program was prospectively applied to 50 adult patients who are Jehovah's Witnesses and have undergone open heart operation at our institution since 1992. The blood conservation program used for these patients included the use of high-dose erythropoietin (800 U/kg load, 500 U/kg every other day), aprotinin (6 million U total dose full Hammersmith regimen), "maximal" volume intraoperative autologous blood donation, intraoperative cell salvage, continuous shed blood reinfusion, and drawing as few blood specimens as possible. RESULTS: Procedures performed included first-time coronary bypass operations (n = 30) and more complex operations, including reoperations, valve replacements, and multiple valve replacements with or without coronary bypass (n = 20). Despite the absence of transfusion, the mean discharge hematocrit in these patients was greater than 30 percent, and there was no anemia-related mortality rate in this group. The overall in-hospital mortality for the group was 4 percent. A subset analysis was performed between the 30 first-time coronary bypass patients (group 1) and a control group of 30 consecutive patients who were not Jehovah's Witnesses but had undergone first-time coronary bypass during the same period (group 2). The blood conservation program described in the previous paragraph was not used in group 2 patients and specific transfusion criteria were prospectively applied. The chest tube output in group 1 patients was less than 40 percent of that for group 2 patients at all points measured after operation (p < 0.01). Postoperative hematocrit levels in group 1 were greater than those for group 2, despite the absence of red blood cell transfusion and despite a significantly lower admission hematocrit and red blood cell mass in group 1. The average length of stay and ancillary costs for the two groups were equivalent. Although group 1 and 2 patients were well matched for preoperative transfusion risk factors, none of the group 1 patients required transfusion, but 17 (57 percent) group 2 patients met transfusion criteria and received 3.0 +/- 4.8 U (mean plus or minus standard deviation) of homologous blood or blood products. CONCLUSIONS: These results suggest that even complex open heart operations can be performed without homologous transfusion by optimally applying available blood conservation techniques. More generalized application of these measures may increasingly allow "bloodless" operations in all patients.

Intraoperative autologous blood donation preserves red cell mass but does not decrease postoperative bleeding.

BACKGROUND: Postoperative bleeding and transfusion remain a source of morbidity and cost after open heart operations. The benefit of the acute removal and reinfusion of fresh autologous blood around the time of cardiopulmonary bypass-a technique known as intraoperative autologous donation (IAD)-has not been universally accepted. We sought to more clearly evaluate the effects of IAD on allogeneic transfusion and postoperative bleeding by removing, preserving, and reinfusing a calculated maximum volume of fresh autologous whole blood. METHODS: Ninety patients undergoing coronary artery bypass grafting or valvular operations were prospectively randomized to either have (IAD group) or not have (control group) calculated maximum volume IAD performed. Treatment was otherwise identical. Transfusion guidelines were uniformly applied to all patients. RESULTS: An average volume of 1,540 +/- 302 mL of fresh autologous blood was removed and reinfused in the IAD group. Postoperative hematocrits were significantly greater at 12 and 24 hours postoperatively in the IAD group versus the control group despite a significant decrease in both the percentage of patients in whom allogeneic red blood cells were transfused (17% versus 52%; p < 0.01) and the number of red blood cell units transfused per patient per group (0.28 +/- 0.66 and 1.14 +/- 1.19 units; p < 0.01). Conversely, chest tube output, incidence of excessive postoperative bleeding, postoperative prothrombin time, and platelet and coagulation factor transfusion requirement did not differ between groups. CONCLUSIONS: These results indicate that intraoperative autologous donation serves to preserve red blood cell mass. Its routine use in eligible patients is therefore justified. However, the removal and reinfusion of an individually calculated maximum volume of fresh autologous blood had no effect on postoperative bleeding or platelet and coagulation factor transfusion requirement. This lack of hemostatic effect belies the beliefs of many about the primary action of IAD, helps to delineate the optimal way in which to perform IAD, and carries implications regarding the use of allogeneic platelet and coagulation factors for the treatment of early postoperative bleeding.

Triiodothyronine therapy lowers the incidence of atrial fibrillation after cardiac operations.

BACKGROUND: Cardiopulmonary bypass results in a euthyroid sick state, and recent evidence suggests that perioperative triiodothyronine (T3) supplementation may have hemodynamic benefits. In light of the known effects of thyroid hormone on atrial electrophysiology, we investigated the effects of perioperative T3 supplementation on the incidence of postoperative arrhythmias. METHODS: One hundred forty-two patients with depressed left ventricular function (ejection fraction < 0.40) undergoing coronary artery bypass grafting were randomized to either T3 or placebo treatment groups in a prospective, double-blind fashion. Triiodothyronine was administered as a 0.8 micrograms/kg intravenous bolus at the time of aortic cross-clamp removal followed by an infusion of 0.113 micrograms.kg-1.h-1 for 6 hours. Patients were monitored for the development of arrhythmias during the first 5 postoperative days. RESULTS: The incidence of sinus tachycardia and ventricular arrhythmias were similar between groups. Triiodothyronine-treated patients had a lower incidence of atrial fibrillation (24% versus 46%; p = 0.009), and fewer required cardioversion (0 versus 6; p = 0.012) or anticoagulation (2 versus 10; p = 0.013) during hospitalization. Six patients in the T3 group versus 16 in the placebo group required antiarrhythmic therapy at discharge (p = 0.019). CONCLUSIONS: Perioperative T3 administration decreased the incidence and need for treatment of postoperative atrial fibrillation.

Cost containment in cardiac surgery: results with a critical pathway for coronary bypass surgery at the New York hospital-Cornell Medical Center.

PURPOSE: A multidisciplinary project was undertaken at The New York Hospital-Cornell Medical Center to develop critical pathways for open-heart surgery to help reduce cost, shorten hospital length of stay (LOS), and streamline patient care. METHODS: A critical pathway for elective coronary artery bypass grafting instituted on March 1, 1995, was developed through a cooperative effort involving surgeons, anesthesiologists, nurses, social workers, physical therapists, nutritionists, and patient case managers. Prospective data collected on consecutive patients forming a critical pathway group (n = 114) over a 6-month period were compared with retrospective data on consecutive patients forming a cohort group (n = 382) who underwent elective coronary artery bypass grafting in 1994. RESULTS: The critical pathway group of patients experienced a significantly shorter total hospital LOS (7.7 +/- 2.3 days vs 11.1 +/- 6 days, p < 0.0001) and shorter intensive care unit LOS (1.5 +/- 0.9 days vs 2.0 +/- 2.8 days, p < 0.0001). Direct costs were computed by use of hospital charges multiplied by the Medicare cost-to-charge ratio. Mean hospital direct cost (ancillary resources) was $1181 lower in the critical pathway group when compared with the control group (p < 0.0001). The postoperative mortality and readmission rates were similar for the two groups of patients. CONCLUSIONS: The ongoing analysis of cost, LOSs, and outcomes has made possible a process of continuous quality improvement on the cardiothoracic service in which further areas for improvement are identified and studied. The use of a critical pathway for elective coronary artery bypass grafting at our institution significantly reduced hospital LOS and direct costs while maintaining the overall quality of patient care.

Combined aprotinin and erythropoietin use for blood conservation: results with Jehovah's Witnesses.

Despite recent advances in blood conservation techniques, major risks persist for excessive bleeding and blood transfusion after open heart operations. We reviewed the records of 100 consecutive patients undergoing first-time coronary artery bypass grafting at our institution to define these risks and develop a multimodality blood conservation program based on the results. This program was subsequently applied on a prospective basis to a select group of patients who refuse blood transfusion on religious grounds (Jehovah's Witnesses [JW]) (n = 15). Encouraging initial results with coronary artery bypass grafting in this group (n = 8) led to the application of the program to more complex operations (n = 7), including repeat bypass grafting with use of the internal mammary artery, repeat mitral valve replacement, aortic and mitral valve replacement with coronary artery bypass grafting, mitral valve replacement with bypass grafting, chronic type 1 dissection repair, aortic valve replacement, and atrial septal defect repair in 1 patient each. The blood conservation program employed in these patients included the use of (1) aprotinin (full Hammersmith regimen), (2) high-dose erythropoietin, (3) "maximal"-volume intraoperative autologous blood donation, (4) low-prime cardiopulmonary bypass, (5) exclusive use of intraoperative cell salvage, and (6) continuous reinfusion of shed mediastinal blood. There were no deaths in the JW group. Thromboembolic complications consisted of a transient posterior circulation stroke in only 1 patient (dissection repair). No blood or blood products were transfused compared with the transfusion of 5.1 +/- 7.8 units (mean +/- standard deviation) in the 100 primary coronary bypass patients in whom the blood conservation program was not employed.(ABSTRACT TRUNCATED AT 250 WORDS)

Platelet-activating factor antagonism attenuates platelet and neutrophil activation and reduces myocardial injury during coronary reperfusion.

Platelet-activating factor (PAF) is known to be synthesized during tissue reperfusion and to be involved in the activation of platelets and neutrophils in inflammatory processes. The hypothesis of the present study is that PAF is central in the pathophysiology of myocardial reperfusion and that specific PAF receptor antagonism may reduce myocardial reperfusion injury. Utilizing an intact sheep model that involved a 90-min occlusion of the mid-left anterior descending coronary artery followed by 6 hr of reperfusion, a study group that received a specific PAF receptor antagonist (L-659,989, 5 mg/kg) 10 min before reperfusion was compared to a control group that received a saline placebo (n = 8 in each group). Coronary sinus platelet aggregating activity and neutrophil oxidative burst were studied by standard platelet aggregometry and the 2',7'-dichlorofluorescein flow cytometric assay, respectively. Left coronary flow and left ventricular functions measured as peak +/- dp/dt and stroke work were analyzed. The extent of myocardial infarction at the end of 6 hr of reperfusion was measured by standard histochemical stainings. The results demonstrated that platelets were hyperaggregable and that neutrophil oxidative burst was increased in the myocardial compartment during the first 3 hr of coronary reperfusion after 90 min of ischemia. The administration of the PAF antagonist immediately before reflow effectively prevented the activation of platelets and neutrophils. This was associated with significantly improved coronary reflow and ventricular function during the observed reperfusion period and with reduced myocardial infarct measured at 6 hr of reperfusion. We conclude that the use of a specific PAF receptor antagonist, L-659,989, immediately before controlled coronary reflow attenuated the activation of platelets and neutrophils that occurred during reperfusion. These anti-platelet and anti-neutrophil effects together with the inhibition of the known direct deleterious effects of PAF on the myocardium translated into improved ventricular function and reduced myocardial infarct.

A historical perspective to current review of myocardial protection in cardiac operation.

In the discussion of the 1955 landmark study on the first series of open heart operation using the cross-circulation technique, Lillehei stated that, "The solution of many difficult problems in medicine has ultimately been simple and in most cases obvious once sufficient basic knowledge has been brought to bear on the problem." Indeed, a few surgeons have provided the guiding lights in the development of cardiac operation, but it is the acquisition of basic knowledge by thousands of surgeons and basic scientists that have contributed to its goals.

The effects of warm versus cold blood cardioplegia on endothelial function, myocardial function, and energetics.

BACKGROUND: Recent interest in the use of normothermic blood cardioplegia is based on theoretical advantages over the traditional method of hypothermic myocardial protection. This study was designed to compare the effects of warm and cold blood cardioplegia on left ventricular functions and energetics and coronary responsiveness. MATERIALS AND METHODS: Two groups of mongrel dogs (n = 7 each) underwent either normothermic cardiopulmonary bypass (CPB) with continuous warm (37 degrees C) blood cardioplegia or hypothermic (26 degrees C) CPB with a single dose of cold (4 degrees C) blood cardioplegia supplemented with topical cooling during 30 minutes of aortic clamping. There was no deterioration in the endothelium-dependent and -independent coronary relaxation as tested by the infusion of acetylcholine and nitroglycerin after cardioplegic arrest for either group. At 60 minutes of reperfusion, both groups had complete recovery of left ventricular contractility as measured by the preload recruitable stroke work area derived from the measurement of the ventricular pressure (micromanometer catheter) and volume (conductance catheter) relation. The analysis of myocardial energetics in terms of the myocardial oxygen consumption-pressure volume area relation did not reveal any significant changes between the y-intercepts and the slopes of the two groups. CONCLUSIONS: For 30 minutes of aortic cross-clamp time, continuous warm cardioplegia did not provide any benefit over a single injection of cold cardioplegia in coronary endothelial and smooth muscle function, myocardial function, and energetics.

Transesophageal echocardiographic localization of an aortic valve papillary fibroelastoma during routine coronary artery bypass surgery.

Papillary fibroelastomas are rare, primary cardiac tumors most often diagnosed incidentally at autopsy. These tumors have been associated with embolism, neurologic injury, coronary ischemia and sudden death. We report a case of clinical detection of an asymptomatic aortic valve papillary fibroelastoma by transesophageal echocardiography. The mass was an incidental finding during routine coronary artery bypass surgery. This finding dictated a change in the operative approach to include resection of the aortic valve mass in addition to coronary revascularization.

Erythropoietin in cardiac surgery.

Erythropoietin is the primary growth factor for red blood cells. A glycoprotein hormone synthesized by the kidneys, erythropoietin serves to increase red blood cell production in response to tissue hypoxia. It exerts its effect by increasing the numbers of erythroid progenitor cells in the bone marrow, and by increasing the rate at which their development is accomplished. With the introduction of recombinant erythropoietin in 1987, an important pharmacological agent became available for the manipulation of erythropoiesis. While used primarily for the treatment of the anemia of renal failure, recombinant erythropoietin has also shown usefulness in treating other types of anemias in which the endogenous erythropoietin response is insufficient. Perioperative use of the drug grew as a natural extension of this, and erythropoietin has been applied to correct preoperative anemia, augment autologous blood donation, and improve postoperative red cell recovery. Analysis of these perioperative clinical studies reveals success in these areas, but it also reveals that closer attention to the physiology of the natural response, and to the pharmacology of the recombinant product, might significantly improve results. Such an improvement in efficacy is both desirable and necessary when use of the drug is viewed in the setting of today's changing health care environment. By optimizing dosing schedules and targeting the drug to those most at risk for red cell transfusion, recombinant erythropoietin will likely become an important tool in efforts to achieve the elusive goal of bloodless cardiac surgery.

The effects of amrinone versus dobutamine on myocardial mechanics and energetics after hypothermic global ischemia.

The effects on the postischemic myocardium of amrinone and dobutamine were studied in canine hearts that underwent 90 minutes of hypothermic (10 degrees C) arrested ischemia. In an isolated heart preparation cross-circulated by a support dog, left ventricular pressure-volume loops were collected under a constant afterload based on a mock circulatory system and a range of preload conditions controlled by a computerized servo volume pump. Dobutamine (0, 5, 10, 15 micrograms/kg per minute) and amrinone (0, 0.75, 1.5, 3.0 mg/kg) were tested in this order based on the weights of the support dogs in eight experiments. Changes in intrinsic myocardial contractility were analyzed as percent increases in the preload recruitable stroke work area from baselines. Dobutamine exhibited significant dose-related increases in the preload recruitable stroke work area. Amrinone did not produce significant increases in preload recruitable stroke work area at 0.75 mg/kg; amrinone's inotropic effect was equivalent to dobutamine, 5 micrograms/kg per minute at 1.5 mg/kg, and at the maximum dose (3.0 mg/kg) it was equivalent to dobutamine, 10 micrograms/kg per minute. The myocardial energetic efficiency was determined from the analysis of the myocardial oxygen consumption-pressure volume area relationship. The y intercept represents the basal metabolic oxygen requirement of the unloaded beating heart, and the slope is inversely proportional to the rate of energy conversion for increasing loading conditions. Dobutamine significantly increased the y intercepts, but it had no effects on the slopes. These changes demonstrate reduced myocardial efficiencies that are consistent with previous reports. Amrinone (0.75 and 1.50 mg/kg) did not result in change of the y intercepts and the slopes of myocardial oxygen consumption-pressure-volume area relationship from baseline conditions. The y intercept was increased with amrinone (3.0 mg/kg), although still not significantly higher than baseline and not to the extents of the dobutamine group. Dobutamine did not have any primary effect on coronary resistance, while amrinone significantly reduced coronary resistance in all loading conditions at 1.5 and 3.0 mg/kg. This study demonstrates that the inotropic effects of amrinone tested under this constant afterload preparation were lower than those of dobutamine. Amrinone has a superior profile of myocardial efficiency on the postischemic myocardium since it does not produce the oxygen-wasting effects of the traditional inotropic agents such as the beta agonists. This benefit, together with amrinone's coronary dilating effects, critically improves the supply/demand ratio that may be of importance in certain clinical situations.

Ischemic tolerance of the arrested heart during warm cardioplegia.

Normothermic blood cardioplegia has recently generated interest as an alternative method of myocardial protection during cardiopulmonary bypass (CPB) surgery. One disadvantage is the obligatory interruption of coronary flow during the distal coronary anastomosis. This study was designed to determine the safe normothermic ischemic time of the arrested and decompressed heart. Under normothermic CPB (37 degrees C), initial cardioplegic arrest was induced with 750 cc of warm (37 degrees C) hyperkalemic blood cardioplegia in 21 adult dogs. The heart then received warm blood cardioplegia either continuously (50 cc/min), every 5 min (250 cc each) or every 10 min (350 cc each) for a total equivalent ischemic time of 30 min (n = 7 in each group). Left ventricular pressure-volume (PV) loops were measured by micromanometer and conductance (volume) catheters before, at 60 and 90 min after aortic cross-clamping. Systolic function was measured as the preload recruitable stroke work area derived from the stroke work-end diastolic volume relationship, and the diastolic stiffness constant (k) was derived from the exponential diastolic PV relationship. The q5 min group sustained minor deterioration in diastolic function while its systolic function was well maintained during recovery. There were significant reductions in both the diastolic and systolic functions in the q10 min group. The maximum drops in the septal wall pH during aortic cross-clamping were 0.05 +/- 0.02 (not significant), 0.19 +/- 0.06 (P < 0.05), and 0.40 +/- 0.09 (P < 0.01) for the continuous, q5 min and q10 min groups, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)