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Biomedical subjects

R M Engelman

Publications and source records attributed to R M Engelman.

At least 163 records · Page 9Linked to original sources
PubMed1983

Use of Fluosol-DA during open-heart surgery.

Cardiopulmonary bypass using a nonpulsatile pumping system and a bubble oxygenator was employed for one hour followed by one hour of recovery in nine pigs using Fluosol as the priming agent for the bypass pump. Gas exchange was found to be adequate with only a minimal decrease in arterial oxygen content and no increase in arterial CO2 content during bypass. Whole body oxygen consumption decreased slightly during bypass, which was felt to be secondary to a less than ideal blood flow of 90-100 ml/kg/min. Higher blood flows were not feasible in our animal model without significant volume expansion during perfusion. Hemodynamic data documented a significant decrease in arterial pressures and an increase in pulmonary artery pressures during the recovery phase. This was associated with a marked increase in pulmonary vascular resistance and was felt to be secondary to pulmonary congestion, the pathogenesis of which is not fully understood.

Animals↗
PubMed1982

Myocardial high-energy phosphate replenishment during ischemic arrest: aerobic versus anaerobic metabolism.

An in vivo, isolated pig heart preparation was used to study the effect of L-glutamate added to crystalloid and blood potassium cardioplegia on the myocardial high-energy phosphate compounds, adenosine triphosphate (ATP) and creatine phosphate (CP). Studies were performed during a three-hour arrest interval and during 60 minutes of reperfusion. Levels of ATP remained at or above control levels during arrest in animals receiving either unmodified blood or glutamate-enriched crystalloid cardioplegia. While glutamate significantly improved the ability of the crystalloid solution to preserve ATP during arrest, when added to blood, it contributed to a depressed ATP after a three-hour arrest. Creatine phosphate declined during arrest in all animals, but those receiving unenriched blood cardioplegia consistently had the highest levels (p less than 0.05). Addition of glutamate to crystalloid cardioplegia provided a significantly (p less than 0.05) higher level of CP at the end of three hours of arrest, which was still lower than that noted with unenriched blood. Comparable to its effect on the ATP level, when glutamate was added to blood cardioplegia, a decrease (p less than 0.05) in CP was noted after three hours of arrest. Attempts to enhance high-energy phosphate production by supplementing blood cardioplegia with L-glutamate are ineffective, while increased high-energy phosphate production results when glutamate is added to crystalloid cardioplegia. This implies that L-glutamate functions where anaerobic and not aerobic metabolism is the major component of preservation. With reperfusion, the only group of animals displaying depressed levels of ATP and CP was that receiving glutamate-enriched blood cardioplegia.

Adenosine Triphosphate↗
PubMed1982

The effect of acute coronary artery occlusion during cardioplegic arrest and reperfusion on myocardial preservation.

A study was undertaken to evaluate the effect of acute occlusion of a coronary artery during cardioplegic arrest on myocardial preservation and to elucidate the influence of reestablishment of flow versus continued occlusion during the phase of myocardial reperfusion. Coronary occlusion was simulated, and myocardial viability was determined by measuring tissue levels of adenosine triphosphate (ATP) and creatine phosphate (CP) in biopsies of the posterior left ventricular wall. Eighteen pigs were divided into three equal groups consisting of animals with (1) patent right coronary arteries during arrest and reperfusion, (2) occluded right coronary arteries during arrest and patent during reperfusion, and (3) occluded right coronary arteries during arrest and reperfusion. The results of ATP and CP measurements showed that while poorer protection was afforded during two-hour arrest when the coronary artery was occluded, the risk of damage was much greater during reperfusion. Failure to restore adequate blood flow by retention of occlusion caused a concurrent decrease in ATP and CP levels below prescribed limits of myocardial tolerance. When occlusion occurs in the clinical setting, impeding cardioplegia and reperfusion, the importance of revascularization is emphasized.

Adenosine Triphosphate↗
PubMed1982

The temperature dependence of recovery of metabolic function following hypothermic potassium cardioplegic arrest.

A study was performed to define the influence of reperfusate temperature on the recovery of high-energy phosphate compounds following hypothermic ischemic cardioplegic arrest. Two groups, each consisting of six pigs, were subjected to 1 hour of hypothermic potassium cardioplegic arrest (myocardial temperature 10 degrees to 15 degrees C). In one group, the arrest period was followed by a 30 minute period of normothermic reperfusion (37 degrees C) followed by a second hour of hypothermic cardioplegic arrest and a second 30 minute normothermic reperfusion period. The second group of pigs was reperfused after the first hour of arrest for 30 minutes with a cold blood (10 degrees to 14 degrees C) followed by an additional hour of hypothermic cardioplegic arrest and a second 30 minute hypothermic reperfusion period. Myocardial biopsy specimens for adenosine triphosphate (ATP) and creatine phosphate (CP) were obtained at the beginning of perfusion (control studies), at the end of each hour of the arrest interval, and at the end of each 30 minutes of reperfusion. The ATP and CP levels were significantly higher after normothermic reperfusion than after hypothermic reperfusion. After normothermic reperfusion the CP level exceeded control; following hypothermic reperfusion CP remained less than 70% of the control level. On the basis of these results, it is proposed that hypothermic reperfusion does not permit the same level of high-energy phosphorylation that is provided with normothermic reperfusion and may therefore adversely affect hemodynamic recovery of the heart after cardioplegic arrest.

Adenosine Triphosphate↗
PubMed1982

Fluosol cardioplegia--a method of optimizing aerobic metabolism during arrest.

Fluosol-DA cardioplegia was compared with crystalloid cardioplegia as a method of myocardial preservation during ischemic arrest. Two groups of 12 pigs each were studied using the in situ pig heart model. Each group was subjected to 2-hour hypothermic (temperature 10-15 degrees C), hyperkalemic (35 mEq/l potassium) cardioplegic arrest. One group received the standard crystalloid cardioplegic solution (PO2 142-164 mm Hg) and the other received an oxygenated Fluosol cardioplegic solution (PO2 420-510 mm Hg). Myocardial contractility (max Vce) compliance, coronary blood flow (six pigs), and adenosine triphosphate and creatine phosphate (six pigs) were measured before and after cardioplegic arrest; high-energy phosphate (adenosine triphosphate and creatine phosphate) levels were also measured during the 2-hour arrest interval. All pigs had 1 hour of normothermic reperfusion, with measurements performed every 15 minutes. The results documented significantly better high-energy phosphate levels in the Fluosol than in the crystalloid group during arrest. During reperfusion, high-energy phosphate levels were equal in both groups. Contractility and compliance were depressed equally during reperfusion in both groups and coronary blood flow showed no significant difference from control in either group. We conclude that Fluosol can support aerobic metabolism during ischemic cardioplegic arrest and preserve high-energy phosphates, but it has no metabolic or hemodynamic advantage during reperfusion.

Adenosine Triphosphate↗
PubMed1981

The optimal potassium concentration in cardioplegic solutions.

High-energy phosphates provide a sensitive index of myocardial preservation. This experiment was designed to use this index in order to assess the efficacy of various potassium concentrations in a crystalloid cardioplegic solution in protecting the myocardium during hypothermic ischemic arrest. The in vivo ischemic pig-heart model was used, measuring left ventricular levels of adenosine triphosphate (ATP) before, during, and after a two-hour arrest period and after 30 minutes of reperfusion. Thirty-eight animals were divided into seven groups of 5 to 6 animals each. Each group received a different potassium concentration in the cardioplegic solution, namely, 5, 10, 15, 20, 25, 30, and 35 mEq/L. The results were as follows: the ATP moiety was best preserved during ischemia and reperfusion in the 15 mEq/L group, while it remained significantly lower in the 5 mEq/L group. The 10, 20, 25, 30, and 35 mEq/L groups showed an intermediate range of ATP preservation. We conclude from these results that cardioplegic solutions containing 5 mEq/L of potassium seem to be inadequate for myocardial preservation during ischemic arrest; that solutions with 15 mEq/L of potassium may offer the best myocardial protection of all concentrations tested; and that solutions with potassium concentrations of 15 and 35 mEq/L are significantly better than normokalemic (5 mEq/L) cardioplegic solutions.

Adenosine Triphosphate↗
PubMed1981

Fluosol-DA: an artificial blood for total cardiopulmonary bypass.

The isolated, in situ pig heart model was used to determine if Fluosol could support myocardial function during cardiopulmonary bypass. Fourteen pigs were utilized; 7 underwent studies of myocardial metabolism (coronary blood flow and vascular resistance, myocardial oxygen consumption and extraction, lactate extraction, and adenosine triphosphate and creatine phosphate levels), and 7 underwent studies of myocardial contractility and compliance (intraventricular balloon measurements). Each study was carried out utilizing one hour of control hemic perfusion, followed by one hour of Fluosol perfusion, and followed by a third hour of a return of hemic perfusion. The results documented that in the vented, beating, nonischemic heart, myocardial metabolism and functional measurements are maintained during an hour of Fluosol perfusion. However, because of an increased level of ionized calcium during Fluosol perfusion, myocardial functional measurements document significantly increased contractility. The increased contractility is associated with an increase in anaerobic metabolism. The latter contributes to a decline in the high-energy phosphate level following a return of hemic perfusion as the heart recovers from the increased work load placed on it during Fluosol perfusion. It is concluded that here is sufficient oxygen-carrying capacity in Fluosol-DA to maintain cardiac function during perfusion in the large animal model. However, the carrier solution for the Fluosol must be adjusted to appropriate electrolyte content to avoid adverse effects on the myocardium.

Adenosine Triphosphate↗
PubMed1981

The effect of prolonged cardioplegic arrest on long-term ventricular function.

Twenty-five patients (15 coronary revascularizations and 10 valve replacements) having ischemic arrest times longer than 120 minutes (121 to 184 min) were studied by scintigraphy 7 to 27 months after operation. We sought to define if prolonged cardioplegic arrest could be correlated with late postoperative ventricular functional deterioration. Each patient had serial enzymes, EKG analyses, and a technetium pyrophosphate (PYP) scan immediately following operation to determine if an intraoperative infarct occurred which could predispose to functional deterioration. One coronary bypass patient (6.7%) suffered a perioperative myocardial infarct. After a follow-up period of 7 to 25 (mean 17.9) months, none of the 15 patients has developed recurrent angina, infarction or congestive heart failure. Comparing preoperative and late postoperative ventricular function, 3 patients (20%) had a greater than 10% fall in ejection fraction (EF) and 3 (20%) a greater than 10% rise. Mean EF (15 patients) prior to operation was 57.8 +/- 4.7% and at restudy 59.0 +/- 4.6%. One valve replacement patient (10%) suffered a perioperative infarction. After a follow-up period of 16 to 27 (mean 19.9) months, all patients continue to do well. Comparing preoperative to late postoperative ventricular function, 3 patients (30%), had a greater than 10% fall in EF and 2 (20%) a greater than 10% rise. Mean EF (10 patients) prior to operation was 60.5 +/- 5.0% and at restudy 60.1% +/- 5.8%. It is concluded that prolongation of cardioplegic arrest beyond 2 hours is well-tolerated in most patients. Routine early postoperative tests were not useful in prognosticating late functional deterioration in 4 of 6 patients not suffering a perioperative infarction, and in these patients depressed function may be secondary to myocardial fibrosis.

Coronary Disease↗
PubMed1981

Perfusion technology in the hypothyroid patient.

Cardiopulmonary bypass may, by necessity, have to be performed in patients who are frankly hypothyroid. In treating five such patients, all of whom required coronary revascularization, it was noted that fluid balance during perfusion was considerably different than that in the normal population. In order to attempt to evaluate this difference, ten consecutive euthyroid patients having revascularization and the five hypothyroid patients were compared to correlate all fluid absorbed and excreted with the duration of bypass, the serum sodium, and subsequent weight gain. Fluid intake, urine output, and retained fluid were significantly elevated in the hypothyroid as compared to the euthyroid group, while serum sodium following operation was not significantly different. While there are considerable data indicating that hypothyroidism is associated with abnormal salt and water excretion, there is no information concerning the alterations which occur during cardiopulmonary bypass. The present study indicates that hypothyroidism is associated with significant diuresis (without administration of exogenous diuretic agents during cardiopulmonary bypass). The proposed explanation for this diuresis rests with the assumption that with cardiopulmonary bypass and appropriate fluid administration, the contracted blood volume in hypothyroid patients expands acutely and a diuresis results.

Angina Pectoris↗
PubMed1981

The metabolic consequences of blood and crystalloid cardioplegia.

Twenty-seven patients undergoing elective coronary revascularization were evaluated by the following metabolic studies: coronary blood flow and vascular resistance, myocardial oxygen consumption and extraction, and lactate and potassium extraction, uptake and release. Patients were divided into two groups, 14 having crystalloid potassium (25 mEq/l) and 13 blood potassium (25 mEq/l) cardioplegic arrest. The groups were comparable in terms of preoperative demographic characteristics and the duration of cardioplegic arrest, which averaged 63.8 minutes in the crystalloid group and 65.6 minutes in the blood group. There were obvious differences in the effects of the two cardioplegic solutions during administration. Crystalloid cardioplegia had a significantly higher infusion rate and, accordingly, a lower vascular resistance, whereas blood cardioplegia provided increased oxygen use during administration. The amount of lactate released during cardioplegic infusion was greater in the crystalloid than in the blood group, while the amount of potassium absorbed by the heart was greater with blood. During reperfusion, coronary blood flow, vascular resistance and myocardial oxygen consumption were not significantly different in the two groups. The myocardial oxygen extraction, as manifested by a narrowed arteriovenous oxygen difference, was decreased compared with control in both groups during early reperfusion, and the extraction curves for both groups returned to control values by 20 minutes. Myocardial lactate release occurred in both groups during early reperfusion and there was no significant distinction between the two groups. Potassium release occurred during reperfusion in both groups, but significantly more potassium was released in the blood group than in the crystalloid group. We conclude that both methods of myocardial preservation provide adequate protection for 1 hour of ischemic arrest and nearly equal depression in oxygen use. Crystalloid cardioplegia allows greater lactate production during the arrest interval, whereas blood allows a greater potassium absorption by the heart during arrest but releases more potassium during reperfusion.

Adult↗
PubMed1979

Epicardial activation in human left anterior fascicular block.

Four patients with coronary artery disease and chronic marked left axis deviation, defined as a frontal QRS axis more negative than -45 degrees, were studied with epicardial mapping during coronary bypass surgery. All patients had normal right ventricular and inferior left ventricular epicardial breakthrough sites and activation sequence. Normal breakthrough in the basal anterolateral left ventricular epicardium was absent in all four patients. Two patients had breakthrough in the apical region of the anterolateral left ventricle. In the other two this region was activated from wave fronts emerging in the right ventricle and inferior left ventricle. The latest site of left ventricular activation was the basal segment of the anterolateral wall, a site never found to be the latest activated in our previously studied patients without conduction defects. This site was activated during or slightly after the terminal portion of the QRS complex. It is concluded that marked left axis deviation in patients with coronary artery disease reflects delayed activation of the basal anterolateral left ventricle, and is consistent with the presence of block or delay in the anterior "fascicle" of the left bundle branch.

Adult↗
PubMed1979

A technique of myocardial preservation perfusion.

We present a technique for administering cold cardioplegia that permits the pump technician to conveniently give the fluid. The method is comparable to that used in providing coronary perfusion for aortic valve procedures because it allows controlled volume flow and perfusion pressure. In addition, the technique is inherently safe from infusion of air bubbles.

Heart Arrest, Induced↗