Biomedical subjects

S E Fremes

Publications and source records attributed to S E Fremes.

At least 73 records · Page 4Linked to original sources

PubMed1991

Recent preoperative myocardial infarction increases the risk of surgery for unstable angina.

Patients with postinfarction angina undergoing surgery for unstable angina face an increased risk of operative mortality. Between January 1982 and December 1987, clinical, angiographic, and operative data was collected prospectively in 588 unstable patients with a prior myocardial infarction within 30 days of surgery (MI) and 5951 unstable patients without preoperative damage (NONMI). MI patients were characterized as being older (age greater than or equal to 70 years: MI, 19.7%; NONMI, 11.6%; p less than 0.001) and having more left ventricular dysfunction (left ventricular ejection fraction less than 40%: MI, 34.8%; NONMI, 26.4%; p less than 0.001). Semi-elective surgery was performed in 82.0% of NONMI patients while 76.9% of MI patients underwent urgent surgery. Operative mortality was increased in MI patients (MI, 11.1%; NONMI, 4.0%; p less than 0.001) which was related to the extent of preoperative MI (non-Q wave, 8.3%; Q wave, 17.5%; p less than 0.001). Stepwise logistic regression analysis identified preoperative MI as an independent risk variable of operative mortality for unstable angina. Separate multivariate analyses were performed to identify the independent predictors for MI and NONMI patients. The multivariate predictors of operative death for MI patients were left ventricular dysfunction, reoperative coronary surgery, nonuse of the internal mammary, age, transmural MI (relative risk 2.11 vs non-Q wave infarction) and left main stenosis. For NONMI patients, the independent variables were urgent operation, left ventricular dysfunction, reoperation, female gender, left main stenosis, and age. The results of this study indicate that recent preoperative MI adversely influences the surgical results in patients with unstable angina. Alternative treatment strategies are warranted for high risk patients, particularly those with transmural MIs and impaired ventricular function.

Adult↗

PubMed1991

Prolonged hypothermic cardiac storage with University of Wisconsin solution. An assessment with human cell cultures.

Hypothermic storage of cardiac allografts is routinely used for transplantation but is associated with an increased mortality when ischemic times are greater than 4 hours. The ideal storage conditions (solution and temperature) could extend the current limits of cold ischemia. Human endothelial cells and ventricular myocytes were studied to screen various solutions and temperatures for organ preservation. Four solutions (modified Euro-Collins, phosphate-buffered saline, Stanford cardioplegia, and University of Wisconsin) were evaluated. Endothelial cells were evaluated after prolonged hypothermic storage consisting of 0 degree, 4 degrees, and 8 degrees C for 36 hours, and ventricular myocytes were stored at 0 degree and 8 degrees C for 24 hours. Cell viability was determined by morphology (10 dishes per group), and trypan blue exclusion (5 dishes per group) in addition to a cell adhesion assay (endothelial cells 5 dishes per group) and adenine nucleotide analysis with high-performance liquid chromatography techniques (ventricular myocytes 5 dishes per group). Endothelial cell morphology was best preserved by University of Wisconsin solution (p less than 0.001, chi 2) and at 0 degree C (p less than 0.01, chi 2). Endothelial cells stored with University of Wisconsin solution excluded trypan blue better (1.0% +/- 0.5% cells stained, p less than 0.001. Analysis of variance [ANOVA]). Cell adhesion was poorly protected with Stanford cardioplegia (p less than 0.001, ANOVA). Myocyte morphology was preserved best with University of Wisconsin solution at 0 degree C (p less than 0.001, chi 2). According to trypan blue staining, Euro-Collins and University of Wisconsin solutions were superior to Stanford cardioplegia or phosphate-buffered solutions (p less than 0.001, ANOVA). Temperature did not influence the trypan blue results. Adenosine triphosphate was maintained best with University of Wisconsin solution at 0 degree C (p less than 0.01, ANOVA). Myocytes were more sensitive to the effects of prolonged storage compared with endothelial cells by morphologic criteria and trypan blue staining characteristics, irrespective of the shorter preservation times. University of Wisconsin solution was the most effective solution tested. Colder temperatures (0 degree to 4 degrees C) provided better protection than 8 degrees C. Myocytes were more sensitive to prolonged preservation than endothelial cells. Furthermore, the technique used appears helpful as a model of prolonged hypothermic storage and could be expanded to assess other interventions.

Adenosine Diphosphate↗

PubMed1990

Surgical repair of postinfarction ventricular septal defect.

Thirty-one patients underwent repair of postinfarction ventricular septal defect (VSD) from 1980 to 1989. All patients were in New York Heart Association functional class IV, and 15 of them were in cardiogenic shock when operated on. Coronary arteriography was performed in all patients before surgery: nine had one-vessel, 11 had two-vessel, and 11 had three-vessel disease. The VSD was anterior in 15 patients and posterior in 16. The operative technique evolved over the years from a fairly extensive infarctectomy and reconstruction of the septum and right and left ventricular walls with a double Dacron patch, to minimal or no infarctectomy and closure of the VSD by excluding the infarcted muscle from the left ventricular cavity. This is accomplished by suturing a single patch of bovine pericardium to healthy endocardium surrounding the infarcted muscle. The right ventricle is left intact. Overall mortality was 10%, with three operative deaths. All deaths occurred in patients in cardiogenic shock who had three-vessel coronary artery disease. Thus, the mortality for patients in shock was 20%, and the mortality for patients with three-vessel disease was 27%. The operative mortality for patients with posterior VSD was twice as high as in patients with anterior VSD. However, univariate analysis of various clinical, hemodynamic, and operative variables indicated that only three-vessel disease was predictive of operative mortality. Because the number of patients was small and the overall operative mortality relatively low, the results of this analysis may not be valid.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗

PubMed1990

Single lung transplantation and closure of patent ductus arteriosus for Eisenmenger's syndrome. Toronto Lung Transplant Group.

A case report of the first single lung transplantation and closure of a patent ductus arteriosus for Eisenmenger's syndrome is presented. The operation was performed on Sept. 28, 1988. The patient was extubated on postoperative day 8, discharged from the intensive care unit on postoperative day 13, and discharged from the hospital on postoperative day 43, free of symptoms and without supplementary oxygen. Subsequent symptoms of dyspnea, presyncope, and fatigue recurred in association with subvalvular right ventricular outflow tract obstruction. Symptomatic improvement occurred gradually in association with reduction of the outflow tract obstruction. The patient is in New York Heart Association class I-II 12 months after the operation. The rationale, methods, and management of this patient are discussed, as well as the potential for application of this operation in similar settings.

Adult↗

PubMed1989

Valvular surgery in the elderly.

In previous studies from this university, advanced age was identified as an independent predictor of operative mortality for valvular surgery. Therefore, between January 1982 and December 1986, early results were compared in 469 patients greater than 70 years old (Old; 74.0 +/- 3.4 years, mean +/- SD) and in 2,040 patients less than 70 years old (Young; 53.7 +/- 12.1 years). Patients underwent single- or multiple-valve repair or replacement with or without concomitant coronary artery bypass surgery. Data consisting of 31 clinical and angiographic variables were collected prospectively and were analyzed by univariate and multivariate statistics. Old patients were characterized by having more frequent left ventricular dysfunction (left ventricular ejection fraction less than 40%: Old, 33.5%; Young, 22.4%; p less than 0.001), coronary artery disease (Old, 54.5%; Young, 24.2%; p less than 0.001), and urgent surgery (Old, 15.6%; Young, 11.8%; p = 0.02). Aortic valve procedures (Old, 59.7%; Young, 40.1%; p less than 0.001) and concomitant coronary artery bypass surgery (Old, 46.4%; Young, 20.3%; p less than 0.001) were performed more commonly in the Old patient. Operative mortality occurred in 10.0% of Old patients compared with 5.6% of Young patients (p less than 0.001), and major morbidity (low-output syndrome, perioperative myocardial infarction, intra-aortic balloon pump counterpulsation, and stroke) occurred significantly more frequently (p less than 0.001) in the Old. Stepwise logistic regression identified that urgent operation (p = 0.002), mitral or double-valve surgery (p = 0.004), coronary artery disease especially when not treated by bypass surgery (p = 0.02), female gender (p = 0.02), and left ventricular dysfunction (p = 0.05) independently predicted operative death in the Old population. The significant predictors of mortality in the Young patient were urgent operation (p less than 0.001), New York Heart Association class IV (p less than 0.001), associated tricuspid valve disease (p = 0.002), decreased left ventricular function (p = 0.01), valvular re-replacement (p = 0.02), and increasing age (p = 0.03). The predicted probability of operative mortality in Old patients ranged between 0.9 +/- 0.5% and 76 +/- 16%. Elderly patients in good risk categories should be offered surgical intervention for correction of valvular lesions. Alternative therapy may be indicated in patients with multiple risk factors.

Age Factors↗

PubMed1988

Decreased postoperative myocardial fatty acid oxidation.

Myocardial substrate preferences following cardioplegic arrest for coronary bypass surgery have not been established. Fatty acids are believed to be the major fuel source for aerobic metabolism. Following cardioplegic arrest arterial fatty acid levels are elevated and myocardial fatty acid accumulation without oxidation may contribute to reperfusion injury. Perioperative fatty acid metabolism was evaluated in 18 patients undergoing elective coronary bypass surgery who were randomized to receive either blood (n = 11) or crystalloid (n = 7) cardioplegia. Palmitate labeled with 14carbon was infused perioperatively and arterial and coronary sinus blood samples were obtained to calculate myocardial fatty acid extraction and oxidation before and after cardioplegic arrest. Lactate and glycerol were released from the heart during both blood and crystalloid cardioplegia, suggesting ischemic glycolysis and lipolysis. Myocardial oxygen consumption was depressed and the myocardial consumptions of lactate, glucose, and fatty acids were minimal during the first 60 min after aortic clamp removal in both groups despite high arterial concentrations. Fatty acid oxidation was minimal after blood cardioplegia and was not found after crystalloid cardioplegia. Fatty acids were extracted by the heart, but were not aerobically metabolized following cardioplegic arrest. Myocardial fatty acid accumulation without oxidation may have been deleterious. The inability of the heart to oxidize exogenous fatty acids may reflect altered myocardial exogenous substrate preferences during reperfusion following coronary bypass surgery.

Cardioplegic Solutions↗

PubMed1987

Right ventricular function: a comparison between blood and crystalloid cardioplegia.

Blood cardioplegia resulted in better left ventricular (LV) function than crystalloid cardioplegia after elective coronary artery bypass operations. However, most methods of cardioplegic delivery may not adequately cool and protect the right ventricle, and right ventricular (RV) dysfunction may limit hemodynamic recovery. Therefore, RV and LV temperatures were measured intraoperatively and RV and LV function were evaluated postoperatively in 80 patients with double-vessel or triple-vessel coronary artery disease who were randomized to receive either blood cardioplegia or crystalloid cardioplegia. Myocardial performance, systolic function, and diastolic function were assessed with nuclear ventriculography by evaluating the response to volume loading. Preoperatively the groups were similar. Intraoperatively, blood cardioplegia resulted in significantly warmer LV and RV temperatures (left ventricle: 15.5 degrees +/- 0.2 degrees C with blood cardioplegia and 12.6 degrees +/- 0.3 degrees C with crystalloid cardioplegia [p less than .0001]; right ventricle: 18.3 degrees +/- 0.3 degrees C with blood cardioplegia and 15.1 degrees +/- 0.3 degrees C with crystalloid cardioplegia [p less than .0001]). Postoperatively, blood cardioplegia resulted in better LV performance (higher LV stroke work index at a similar LV end-diastolic volume index [EDVI]) (p = .01), better LV systolic function (similar systolic blood pressures at smaller LV end-systolic volume indexes [ESVI]), (p = .04), and improved LV diastolic function (lower left atrial pressures at similar LVEDVIs) (p = .03).(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Pressure↗

PubMed1987

Transient biventricular dysfunction following coronary bypass surgery with potassium cardioplegia.

Although myocardial revascularization relieves anginal symptoms, the effect on ventricular function remains controversial. Sixty-six patients undergoing elective coronary bypass surgery with normal right and left ventricular function were studied 1 month preoperatively (PRE), 3-5 hours perioperatively (PERI) and 3-5 months postoperatively (POST). Nuclear ventriculograms were employed to calculate right and left ventricular ejection fractions (RVEF, LVEF), end diastolic volume indices (RVEDVI, LVEDVI) and end systolic volume indices (RVESVI, LVESVI). Cardiac index (CI), stroke index (SI) and an approximation of left ventricular stroke work index (LVSWI) were also calculated from the scintigraphic data. Right and left ventricular ejection fractions were lower perioperatively (PRE:RVEF 37 +/- 2.5, LVEF 61 +/- 3; PERI:RVEF 32 +/- 3, LVEF 51 +/- 4; POST:RVEF 35 +/- 3, LVEF 56 +/- 4%, p less than 0.01 by analysis of variance, ANOVA) despite lower end diastolic volume indices perioperatively, (p less than 0.05 by ANOVA). The ratio of systolic blood pressure to LVESVI was significantly lower PERI than PRE or POST, (p less than 0.01 by ANOVA). SI, LVSWI, LVEF and RVEF were lower perioperatively at any level of LVEDVI or RVEDVI (p less than 0.01 by paired analyses of covariance), suggesting transient depression of right and left ventricular performance perioperatively. Right ventricular recovery was incomplete 4 months postoperatively. The patients were able to exercise longer at higher workloads postoperatively (p less than 0.01 by ANOVA). Chest pain resulted in discontinuation of exercise in 57% of patients PRE but only 5% POST (p less than 0.01), even though all patients were receiving full medical therapy preoperatively and no therapy postoperatively. Myocardial revascularization provided symptomatic relief and increased work capacity. However, right and left ventricular function were transiently depressed in the early perioperative period.

Coronary Artery Bypass↗

PubMed1987

Cardiac release of prostacyclin and thromboxane A2 during coronary revascularization.

Cardiac surgery stimulates the systemic synthesis of prostacyclin and thromboxane A2, but the cardiac release of these prostanoids has been reported infrequently. Fifty-four patients undergoing elective coronary artery bypass had coronary sinus catheters inserted to evaluate the cardiac release of the stable metabolites of prostacyclin (6-keto-prostaglandin F1 alpha) and thromboxane A2 (thromboxane B2). Arterial concentrations of 6-keto-prostaglandin F1 alpha and thromboxane B2 were elevated after cardiac cannulation and during cardiopulmonary bypass. The cardiac release of 6-keto-prostaglandin F1 alpha was observed after cannulation and during, but not after, cardiopulmonary bypass. Cardiac thromboxane B2 release was detected after cross-clamp release and persisted during the early postoperative period when cardiac 6-keto-prostaglandin F1 alpha release was no longer detectable. Cardiopulmonary bypass stimulated the systemic production of thromboxane and prostacyclin. The cardiac release of thromboxane was unopposed by cardiac prostacyclin production in the early postoperative period and may contribute to reperfusion injury.

6-Ketoprostaglandin F1 alpha↗

PubMed1986

Late postoperative ventricular function after blood and crystalloid cardioplegia.

Although blood cardioplegia preserves perioperative ventricular function better than crystalloid cardioplegia, late results are uncertain. Nuclear ventriculograms were used to assess ventricular function in 47 patients undergoing coronary bypass surgery who were randomly assigned to receive blood (23 patients) or crystalloid cardioplegia (24 patients). Data were acquired at rest and during maximal exercise (bicycle ergometer) 1 month before surgery (PRE), 5 months after surgery (POST), and perioperatively at rest 3 to 5 hr after operation (PERI). Perioperatively, blood cardioplegia decreased ischemic injury (less elevation in creatine kinase-MB fraction and aspartate aminotransferase; p less than .05), preserved ventricular performance (lower stroke work index at higher left ventricular end-diastolic volume index after crystalloid than blood cardioplegia; p = .02 by analysis of covariance [ANOCOVA]) and preserved systolic function (higher left ventricular end-systolic volume index [LVESVI] at similar systolic blood pressure after crystalloid than blood cardioplegia; p = .02 by ANOCOVA). Postoperatively, resting ventricular performance and systolic function were not different with blood and crystalloid cardioplegia and were similar to preoperative measurements. Postoperatively, the response to exercise was similar between the two groups and was improved compared with that at PRE. Postoperative systolic function at exercise was similar between the two groups but was better than that at PRE (higher systolic blood pressure at similar LVESVI; p = .01 by ANOCOVA). The type of cardioplegic solution influenced perioperative but not late postoperative function after elective coronary artery bypass surgery.

Blood↗

PubMed1986

Reducing the risk of urgent revascularization for unstable angina: a randomized clinical trial.

A prospective, randomized trial was instituted to determine whether blood cardioplegia (BC) could reduce the morbidity and mortality for patients undergoing urgent coronary bypass for unstable angina. One hundred forty patients who came to the hospital with prolonged angina at rest and who required urgent revascularization because their symptoms were resistant to medical therapy were randomized to receive BC (n = 70) or crystalloid cardioplegia (CC) (n = 70). The operative mortality rate was 2.8%, the incidence of myocardial infarction was 8.6%, the incidence of low output syndrome was 18% and morbidity (myocardial infraction or low output syndrome) was 23%. Patients who received BC had a significantly lower mortality rate (BC, 0%; CC, 5%; p less than 0.05) and incidence of myocardial infarction (BC, 4%; CC, 13.5%; p less than 0.05) or low output syndrome (BC, 10%; CC, 19%; p less than 0.05). The highest postoperative CK-MB level was less after BC (BC, 31 +/- 17 U/L; CC, 56 +/- 13 U/L; p less than 0.05). Preoperative predictors of postoperative morbidity in addition to the type of cardioplegia included the response to medical therapy, persistent ischemic electrocardiographic changes, left ventricular ejection fraction, and age. A multivariate analysis identified the type of cardioplegic protection (p = 0.008) and age (p = 0.05) as significant independent predictors of postoperative morbidity. BC reduced the risk of urgent revascularization for unstable angina.

Age Factors↗

PubMed1986

Diltiazem cardioplegia. A balance of risk and benefit.

Calcium channel blockers may prevent myocardial injury during cardioplegia and reperfusion. A prospective, randomized trial was instituted to evaluate the hemodynamic and myocardial metabolic recovery in 40 patients undergoing elective aorta-coronary bypass with either diltiazem in crystalloid potassium cardioplegia (n = 20) or crystalloid potassium cardioplegia (n = 20). In a preliminary trial, doses between 150 and 250 micrograms/kg reduced the period of heart block after cross-clamp removal (90 +/- 110 minutes) from that found with higher doses and improved myocardial metabolism. In the randomized trial, diltiazem cardioplegia (150 micrograms/kg) produced coronary vasodilatation during cardioplegia and produced less reactive hyperemia during reperfusion. Myocardial oxygen extraction was lower and myocardial lactate production was less after diltiazem cardioplegia during reperfusion. Tissue adenosine triphosphate and creatine phosphate concentrations were preserved better after diltiazem cardioplegia. The postoperative creatine kinase MB levels were less (p less than 0.05) after diltiazem cardioplegia, which indicated less myocardial injury. Postoperative volume loading demonstrated that systolic function (the relation between systolic blood pressure and end-systolic volume index) was depressed after diltiazem cardioplegia compared to crystalloid cardioplegia, but cardiac index was higher because afterload (mean arterial pressure) was lower and preload (end-diastolic volume index) was higher. Diltiazem cardioplegia preserved high-energy phosphates, improved postoperative myocardial metabolism, and reduced ischemic injury after elective coronary bypass. However, diltiazem was a potent negative inotrope and produced prolonged periods of electromechanical arrest. Diltiazem cardioplegia may be of value in patients with severe ischemia but should be used with caution in patients with ventricular dysfunction, and a dose-response relation must be established at each institution before clinical use.

Benzazepines↗

PubMed1986

Accelerated myocardial metabolic recovery with terminal warm blood cardioplegia.

Although blood cardioplegia provides excellent protection, myocardial metabolic recovery is delayed. To evaluate the benefits of a terminal warm cardioplegic infusion after cold blood cardioplegia, we performed a prospective randomized trial in 20 patients undergoing elective coronary bypass grafting. Eleven patients received cold blood cardioplegia and nine patients received cold blood cardioplegia and warm blood cardioplegia before cross-clamp removal (hot shot). The hot shot provided oxygen and removed excess lactate from the arrested heart. After the hot shot lactate was extracted by the heart and tissue adenosine triphosphate and glycogen concentrations were preserved. Atrial pacing and volume loading 3 and 4 hours postoperatively decreased myocardial lactate extraction after cold blood cardioplegia but increased lactate extraction after the hot shot. Left atrial pressures were higher at similar end-diastolic volumes (by nuclear ventriculography), which suggested decreased diastolic compliance after cold blood cardioplegia. Terminal warm blood cardioplegia accelerated myocardial metabolic recovery, preserved high-energy phosphates, improved the metabolic response to postoperative hemodynamic stresses, and reduced left atrial pressures.

Adenosine Triphosphate↗

PubMed1986

Can the results of contemporary aortic valve replacement be improved?

Although the results of contemporary aortic valve replacement are excellent, cardiac surgeons must identify the factors that predict postoperative morbidity and mortality to develop alternative strategies for high-risk patients. Two hundred seventy-seven consecutive patients undergoing isolated aortic valve replacement between 1982 and 1984 were evaluated. Thirty-seven clinical and 13 preoperative hemodynamic variables were analyzed by univariate and multivariate statistics to determine the risk factors for postoperative morbidity and mortality. The operative mortality was 3%, the incidence of a postoperative low output syndrome was 12%, and the incidence of a perioperative myocardial infarction was 5%. A multivariate, logistic regression analysis found that age was the only the only independent predictor of mortality. Three factors independently predicted postoperative low output syndrome: age, the presence of coronary artery disease, and the peak systolic gradient in patients with aortic stenosis. Patients with aortic stenosis had a higher incidence of postoperative ventricular dysfunction (17%) than those with mixed valvular disease (9%) or aortic regurgitation (5%). Perioperative myocardial infarction was predicted by the extent of coronary artery disease. The incidence of perioperative myocardial infarction was higher in patients with triple-vessel coronary artery disease (13%) and those with left main stenosis (18%) than in patients with single- or double-vessel disease (4%) or those without coronary artery disease (4%). Because of the higher risk of aortic valve replacement in older patients, the risk-benefit ratio of the operation must be carefully assessed in the elderly. Improved methods of myocardial protection may reduce the risks for patients with aortic stenosis and symptomatic triple-vessel coronary artery disease.

Adult↗

PubMed1985

A comparison of nitroglycerin and nitroprusside: I. Treatment of postoperative hypertension.

Nitroglycerin improves perfusion to ischemic myocardial regions and therefore has theoretical advantages over sodium nitroprusside to treat hypertension (mean arterial pressure [MAP] greater than 95 mm Hg) following coronary bypass operation. Thirty-three hypertensive patients were randomized to an initial infusion of either nitroglycerin or nitroprusside in a crossover trial designed to reduce MAP to 85 mm Hg. Thermodilution cardiac output measurements permitted calculation of left ventricular stroke work index (LVSWI), and nuclear ventriculograms permitted estimation of left ventricular ejection fraction, left ventricular end-diastolic volume index (LVEDVI), and left ventricular end-systolic volume index (LVESVI). Coronary sinus blood flow was measured by the continuous thermodilution technique, and arterial and coronary sinus lactate measurements permitted calculation of myocardial lactate flux (MVL). Both nitroglycerin and nitroprusside reduced MAP (-25 +/- 12 mm Hg and -20 +/- 10 mm Hg, respectively; not significant [NS]). Nitroglycerin reduced LVSWI more than did nitroprusside (-15 +/- 13 gm-m/m2 and -7 +/- 9 gm-m/m2, respectively; p less than 0.01). Both agents increased left ventricular ejection fraction (nitroglycerin, +8 +/- 8%, and nitroprusside, +10 +/- 7%; NS), and decreased LVEDVI (-20 +/- 22 ml/m2 and -11 +/- 17 ml/m2, respectively; NS) and LVESVI (-13 +/- 14 ml/m2 and -10 +/- 12 ml/m2, respectively; NS). Coronary sinus blood flow decreased with both drugs (NS), but MVL increased with nitroglycerin (+0.02 +/- 0.14 mmol/min) and decreased with nitroprusside (-0.02 +/- 0.02 mmol/min) (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiac Output↗

PubMed1985

A comparison of nitroglycerin and nitroprusside: II. The effects of volume loading.

The treatment of postoperative hypertension with nitroglycerin or nitroprusside reduces cardiac filling, and volume loading is required to maintain hemodynamic and metabolic stability. Postoperative hypertension (mean arterial pressure greater than 95 mm Hg) developed in 33 patients who were randomized to an initial infusion of nitroglycerin or nitroprusside in a crossover trial. Volume loading (a rapid infusion of 250 to 500 ml of colloid to raise the left atrial pressure 2 to 4 mm Hg) was instituted prior to hypertension and again following the crossover trial during the infusion of nitroglycerin (11 patients) and nitroprusside (13 patients). Volume loading increased left ventricular end-diastolic volume index (LVEDVI) as documented by nuclear ventriculography, cardiac index (CI), and left ventricular stroke work index (LVSWI). Although CI was higher (p less than 0.01) with nitroprusside at any level of LVEDVI, myocardial performance (the relation between LVSWI and LVEDVI) was not different. Diastolic compliance (the relation between left atrial pressure and LVEDVI) was increased (p less than 0.01) with nitroglycerin. Myocardial metabolism was assessed by calculating myocardial lactate flux (MVL), the product of myocardial lactate extraction and coronary sinus blood flow by the thermodilution technique. Volume loading increased MVL during nitroglycerin therapy and decreased (p less than 0.01) MVL during nitroprusside therapy. Volume loading restored preload and increased CI with both nitroglycerin and nitroprusside. Only nitroglycerin improved myocardial lactate utilization. Nitroglycerin is the preferred vasodilator when ischemia is suspected after coronary bypass operations.

Cardiac Volume↗

PubMed1985

Hemodynamic and myocardial metabolic consequences of PEEP.

The cardiac effects of positive end expiratory pressure (PEEP) were examined in 50 patients six hours after elective coronary bypass surgery. Increasing the level of PEEP from 5 to 10 to 15 cm H2O decreased cardiac index (evaluated by thermodilution), stroke index and left ventricular end diastolic volume index without a change in left ventricular ejection fraction (evaluated by nuclear ventriculography). Right ventricular end diastolic volume index remained unchanged. Coronary sinus blood flow (measured by the continuous thermodilution technique) and myocardial oxygen and lactate consumption were unchanged with the application of 15 cm H2O PEEP. In 21 patients, volume loading (250 ml [mL] of plasma) was performed at 5 cm, and again at 15 cm H2O PEEP. Volume loading produced a similar increase in cardiac volumes and cardiac index at 5 and 15 cm H2O PEEP. Right and left ventricular performance and left ventricular systolic function were not altered by PEEP (by analyses of covariance). Coronary sinus blood flow and myocardial oxygen consumption increased with volume loading at 5 and 15 cm H2O of PEEP, but myocardial lactate utilization tended to increase at 5 cm, and decrease at 15 cm H2O PEEP (p = 0.08). Of the 33 patients who underwent complete hemodynamic and metabolic measurements, 16 increased cardiac lactate utilization at 15 cm H2O PEEP and 17 decreased cardiac lactate utilization at 15 cm H2O PEEP. PEEP decreased cardiac index, perhaps by reducing left but not right ventricular volumes. Volume loading during PEEP restored cardiac index and revealed no depression in myocardial performance or systolic function. With the application of PEEP, myocardial metabolism was maintained in half the patients, but ischemic metabolism was observed in the other half.

Blood Pressure↗

PubMed1985

Myocardial metabolism and ventricular function following cold potassium cardioplegia.

Transient alterations in myocardial metabolism and ventricular function were observed after elective coronary bypass grafting despite apparently adequate intraoperative protection with cold potassium cardioplegia. Ninety patients had serial hemodynamic measurements and coronary sinus catheters inserted. Thirty-three patients had thermodilution coronary sinus flow catheters inserted to measure coronary sinus blood flow and to evaluate the myocardial utilization of oxygen and lactate. Nuclear ventriculograms were performed in 43 patients to assess ventricular function. Cardiac index fell after discontinuation of cardiopulmonary bypass and then rose between 2 and 24 hours postoperatively. Myocardial oxygen consumption steadily increased during this period. Myocardial lactate production reverted to lactate extraction 30 minutes after reperfusion. Reactive hyperemia was present during the first 10 minutes after cross-clamp release, and coronary sinus blood flow increased gradually during the first 24 hours postoperatively. The response to the stress of volume loading (the infusion of 250 to 500 ml of a colloid solution) and atrial pacing (at a rate of 110 beats/min) was evaluated 2 to 4 hours postoperatively (EARLY) and between 4 to 6 hours postoperatively (LATE). Volume loading resulted in a decrease in lactate extraction EARLY and an increase LATE (EARLY: -0.07 +/- 0.35 mmol/L; LATE: 0.08 +/- 0.32 mmol/L, mean +/- standard deviation not significant). Atrial pacing resulted in a decrease in lactate extraction EARLY and an increase LATE (EARLY: -0.11 +/- 0.34 mmol/L; LATE: 0.14 +/- 0.36 mmol/L, p less than 0.05). Diastolic compliance (the relation between the end-diastolic volume index) decreased between EARLY and LATE. Systolic function (the relation between the systolic blood pressure and the end-systolic volume index) and myocardial performance (the relation between the left ventricular stroke work index and the end-diastolic volume index) were unchanged. Ejection fraction correlated inversely with the end-diastolic volume index and did not represent an independent index of contractility. After elective coronary bypass grafting and cold crystalloid cardioplegia, myocardial metabolism recovered slowly. Hemodynamic stresses should be avoided in the early postoperative period to prevent progressive ischemic injury.

Adult↗