Infusion Flow Research Articles

Adjustments in etoposide infusion flow rates when using controllers

Adjustments in etoposide infusion flow rates when using controllers

Gravity Cavernosometry—a Simple Diagnostic test for Cavernosal Incompetence

The papaverine test has been widely used as a diagnostic procedure in erectile impotence. However, when patients do not achieve full erection on the test, it is necessary to differentiate between insufficient inflow and excessive outflow. Gravity cavernosometry is a method designed to evaluate the pressure responses in the corpora when they are subjected to a constant infusion pressure. The infusion flow is of minor significance. The intracavernous pressure (ICP) was measured in cadavers, in psychogenically impotent patients and in patients with arteriogenic impotence, following administration of papaverine and gravity perfusion. During perfusion in cadavers and in psychogenic patients, the ICP showed values above 110 cm H2O, while in arteriogenic patients the values ranged from 30 to 141 cm H2O. In the arteriogenic group, 11/20 patients had an ICP lower than 110 during perfusion. There was no correlation between the pre-perfusion pressure and the final pressure with perfusion. Gravity cavernosometry is a simple, cost-effective and reliable method for the assessment of corporeal competence.

Adenosine diphosphate-induced aggregation of human platelets in flow through tubes. I. Measurement of concentration and size of single platelets and aggregates

A double infusion flow system and particle sizing technique were developed to study the effect of time and shear rate on adenosine diphosphate-induced platelet aggregation in Poiseuille flow. Citrated platelet-rich plasma, PRP, and 2 microM ADP were simultaneously infused into a 40-microliters cylindrical mixing chamber at a fixed flow ratio, PRP/ADP = 9:1. After rapid mixing by a rotating magnetic stirbar, the platelet suspension flowed through 1.19 or 0.76 mm i.d. polyethylene tubing for mean transit times, t, from 0.1 to 86 s, over a range of mean tube shear rate, G, from 41.9 to 1,000 s-1. Known volumes of suspension were collected into 0.5% buffered glutaraldehyde, and all particles in the volume range 1-10(5) microns 3 were counted and sized using a model ZM particle counter (Coulter Electronics Inc., Hialeah, FL) and a logarithmic amplifier. The decrease in the single platelet concentration served as an overall index of aggregation. The decrease in the total particle concentration was used to calculate the collision capture efficiency during the early stages of aggregation, and aggregate growth was followed by changes in the volume fraction of particles of successively increasing size. Preliminary results demonstrate that both collision efficiency and particle volume fraction reveal important aspects of the aggregation process not indicated by changes in the single platelet concentration alone.

Fetal cardiovascular, endocrine, and fluid responses to atrial natriuretic factor infusion

The purpose of this study was to determine the effects of atrial natriuretic factor (ANF) in the fetus and to explore the interactions among the fetal cardiovascular, endocrine, and fluid responses to ANF. In 12 chronically catheterized fetal sheep at 130 +/- 1 (SE) days gestation, ANF was infused intravenously for 30 min at 14-300 ng.min-1.kg-1. Fetal arterial plasma ANF concentration increased by 174 to 5,410 pg/ml from a preinfusion value of 163 +/- 13 pg/ml. The clearance of ANF from the circulation was 122 +/- 28 ml.min-1.kg-1 and the half-life was 0.46 +/- 0.07 min. When plasma ANF was greater than 2,000 pg/ml, fetal arterial pressure decreased, venous pressure increased transiently, and heart rate was unchanged. Plasma arginine vasopressin (AVP) concentration and plasma renin activity (PRA) increased with high ANF concentrations, while norepinephrine concentrations were unaffected. Fetal blood volume decreased in all fetuses, and urine flow increased significantly but not in every fetus. Blood and urine osmolalities did not change. On terminating the infusion, venous pressure and urine flow decreased below control, while blood volume and arterial pressure remained reduced. Plasma AVP concentration increased further, and this was accompanied by an increase in urine osmolality. Thus the most consistent effect of ANF in the fetus was a reduction in blood volume, which was independent of urine flow changes. Other cardiovascular, endocrine, and fluid responses to ANF as well as interactions among them appeared to occur largely at supraphysiological concentrations and may be secondary to the changes in blood volume.(ABSTRACT TRUNCATED AT 250 WORDS)

Experience in diagnosis and treatment of impotence caused by cavernosal leak syndrome

To delineate neural, arterial, and venous components contributing to impotence, we used a previously described noninvasive screening sequence combined with stimulation of artificial erection with papaverine injection, selective pudendal arteriography (SPA), and dynamic cavernosography (DC). Among 572 men with impotence, age range 17 to 78 years (average age 54.8 years), 26 men with potential cavernosal leaks in absence of other factors were identified; 16 underwent DC; among these five had normal cavernosal venous drainage. Eight men with abnormal cavernosal venous drainage required cavernous infusion flow rates higher than 120 ml/min to obtain erection and higher than 40 ml/min to maintain erection. Radiographic studies showed cavernosal leakage in all eight patients. Eight men, ages 39 to 61 years, underwent surgical ablation of abnormal cavernosal venous drainage. Among these, five men have had excellent results for up to 3 years. One failure was related to unrecognized penile arterial disease later shown by SPA. In two men small doses of papaverine now induce erection. We now recommend SPA before DC to rule out an arterial abnormality. Accurate identification of factors contributing to erectile failure is critical for successful treatment; in this experience candidates for correction of cavernosal leak syndrome were uncommon.

Further characterisation of the 'ileal brake' reflex in man--effect of ileal infusion of partial digests of fat, protein, and starch on jejunal motility and release of neurotensin, enteroglucagon, and peptide YY.

Previous studies have shown that ileal infusion of partially digested triglyceride inhibits jejunal motility. The partial digest used in those studies contained a mixture of glycerol, free fatty acid, mono-, di-, and triglycerides. In Part I of the present study we have separately infused emulsions containing either glycerol 3.1 g (n = 6), oleic acid 9.6 g (n = 6), triolein 10 g (n = 12), or medium chain triglycerides 10 g (n = 6) into the ileum and have recorded the effect this has on jejunal motility. Five further subjects received infusions of partial hydrolysates of corn starch 10 g and lactalbumin 7 g. Marked inhibition of jejunal pressure wave activity was seen after all three lipid infusions, per cent activity falling from a control of 37.7 (7.7) to 6.2 (2.1) and 22.4 (8.2)% 30 min after completing the oleic acid and triolein infusions respectively, and from a control value of 39.5 (4.1) to 17.7 (4.7) after MCTs (all p less than 0.05). No significant fall occurred after infusion of glycerol, protein or carbohydrate. All three lipid infusions raised plasma concentrations of neurotensin, enteroglucagon and peptide YY equally effectively, although only the rise in peptide YY correlated significantly with the inhibition of jejunal pressure wave activity (r = 0.80, n = 6, p less than 0.05). In Part II of this study six subjects received a 3 ml/min jejunal infusion of an isotonic carbohydrate saline solution followed after three hours by a similar infusion of a partial digest of lipid. During each infusion flow and transit time was measured by marker and dye dilution. Jejunal infusion of the carbohydrate-saline solution was associated with low jejunal flow, 4.7 (1.0) ml/min and a mean transit time through the 50 cm study segment of 36.5 (7.1) min. By contrast jejunal infusion of partially digested triglyceride was associated with a markedly increased flow, 9.0 (1.2) ml/min, a fall in mean transit time to 20.3 (2.6) min and significant rises in pancreaticobiliary secretions. Jejunal triglyceride also increased the incidence of prolonged high amplitude jejunal pressure waves in four of six subjects. These studies suggest that there are important differences in the jejunal response to ileal versus jejunal lipid. While long and median chain free fatty acids infused into the ileum exert an inhibitory effect on jejunal motility, when infused directly into the jejunum partially digested triglyceride accelerates transit, increases jejunal flow and subtly alters the pattern of jejunal contractions.

Normothermic rapid volume replacement in traumatic hypovolemia. A prospective analysis using a new device.

Inadequate infusion flow rates and hypothermia are significant problems encountered in managing traumatic hemorrhagic shock. The Rapid Solution Administration Set (RSAS) allows normothermic volume restoration at flow rates of up to 2200 mL/min via a single peripheral venipuncture. The RSAS was utilized in 33 consecutive multiple-trauma patients with a mean trauma score (TS) of 6.8. Admission systolic blood pressure averaged 66.9 mm Hg. A mean of 5692 mL of packed red blood cells, 5515 mL of blood products, and 12,052 mL of crystalloid solution per patient was infused within 24 hours of admission mostly via the RSAS. Mortality was 45% at 24 hours following arrival and 61% overall. The mortality was 93.8% (15/16) in patients with a TS of 5 or less and 29.4% (5/17) in patients with a TS over 5. The initial postinfusion patient temperatures averaged 35.2 degrees C. All abnormal preinfusion coagulation values normalized within 24 hours in the survivors, and no significant complications occurred with the use of the RSAS. The RSAS seems to provide an uncomplicated means of normothermic volume replacement. The 24-hour survival in potentially salvageable patients may be improved. Its use in patients with lethal injuries (TS less than or equal to 3) requires further evaluation.

Infusion Flow Rates of Whole Blood and AS-1-Preserved Erythrocytes: A Comparison

We compared the flow rates of whole blood and erythrocytes resuspended in a new preservative solution (AS-1, consisting of adenine, dextrose, mannitol, and saline) which results in an erythrocyte preparation with a hematocrit lower than that of packed erythrocytes. When 100 ml of AS-1 solution is added to erythrocytes, a hematocrit of 59 +/- 5% is consistently obtained, and the resultant product has an improved flow rate. When we compared the infusion flow rates of whole blood and AS-1-preserved erythrocytes in vitro and in vivo, we found that flow times were shorter for AS-1 erythrocytes than for whole blood in vitro and in vivo, the flow rates of AS-1 erythrocytes and whole blood when expressed per volume were similar in vivo, and the flow rate of AS-1 erythrocytes for erythrocyte mass delivery in vivo was superior to that of whole blood. Thus, we conclude that the flow rates of the two products are comparable.

Intraosseous infusion flow rates in hypovolemic “pediatric” dogs

We tested a 20-gauge, 2 1/2-inch spinal needle and a 13-gauge, 3 1/2-inch bone marrow needle with Ringer's lactate delivered by gravity and 300 mm Hg pressure in vitro and in hypovolemic puppies to ascertain in vivo intraosseous flow rates and to determine the effects of catheter size and anatomic factors on flow rate. In vitro flow was significantly faster than in vivo flow (P = .001). In vivo, mean flow rates were 11 mL/min for the 20-gauge needle and 13 mL/min for the 13-gauge needle by gravity. The mean flows by 300 mm Hg pressure for the same needles were 24 mL/min and 29 mL/min. While the in vivo flow rates were significantly greater for the 13-gauge versus the 20-gauge needle, the differences were not clinically significant (2 mL/min difference by gravity and 5 mL/min difference by pressure). The clinically comparable in vivo rates for the two needles tested indicated that the rates are dependent on flow through the bone marrow rather than the size of the needle. The data suggest that while intraosseous infusion is a rapid technique for gaining vascular access, the flow rates achieved may not be sufficient for the definitive treatment of severe hypovolemic or hemorrhagic shock alone.

The effects of dopamine infusion on regional blood flow in newborn lambs.

The purpose of this project was to investigate the effects of high rates of dopamine infusion on cardiac output and regional blood flow in the lamb. We studied eight unanesthetized newborn lambs (mean age 7 +/- 2 days) during a 15-min baseline period and while infusing dopamine at 5-, 20-, 80-, and 160 micrograms/kg/min. We measured cardiac output and mean aortic, pulmonary arterial and left atrial pressures, and organ blood flow using radionuclide-labeled microspheres at each rate of dopamine infusion. Cardiac output increased significantly with increasing rates of infusion up to 80 micrograms/kg/min but decreased at 160 micrograms/kg/min. Aortic, pulmonary arterial, and left atrial pressures increased at rates of infusion above 5 micrograms/kg/min. Blood flow to all organs was unchanged at the 5 micrograms/kg/min rate of infusion of dopamine while blood flow to the brain and heart increased at the 80 micrograms/kg/min rate of infusion and blood flow to the gut and kidney decreased. We conclude that dopamine is an effective inotropic agent in the newborn lamb but that an inotropic:afterload mismatch exists at high infusion rates. Despite an increase in cardiac output at low rates of infusion, dopamine did not selectively vasodilate the vascular bed of any organs tested. Furthermore, at high rates of infusion dopamine actually impaired blood flow to the gut and kidney.

Distribution of the increased cardiac output secondary to the vasodilating and inotropic effects of secretin

Infusion of the peptide secretin augments cardiac output due to vasodilating and inotropic properties. The aim of this investigation was to study how the increased cardiac output is distributed in the peripheral circulation. Before, during and after 15 min infusion of secretin 64 CU kg-1 h-1 flow changes in renal, carotid, femoral and the superior mesenteric arteries were measured by means of electromagnetic flowmetry in anaesthetized dogs. Cardiac output and stroke volume increased by 41 and 27%, respectively, whereas the total systemic resistance fell 35%. The LVdP/dt increased by 35%. After 5 min infusion, renal and carotid flows increased by 62 and 50%, respectively, whereas the femoral flow was only slightly elevated and the superior mesenteric flow unchanged. Both the femoral and the superior mesenteric flow gradually augmented and at the end of the infusion flow was substantially elevated in all four arteries. The study demonstrated that the increased cardiac output by secretin was distributed to all the four arteries, although a preponderance of flow to the renal circulation was indicated. This flow profile may be regarded as favourable in the management of low output conditions.

Dissociation of adenosine from metabolic regulation of coronary flow in the lamb.

The objective of these studies was to evaluate the contribution of an adenosine mechanism to metabolic regulation of coronary flow. Cardiac O2 metabolism (MVO2) was altered by changing cardiac output while aortic pressure and heart rate were held constant (paced). Ganglionic (tetraethylammonium chloride) and beta blockade (propranolol) were employed. Relationships of coronary flow to MVO2 were determined in control and alloxan diabetic animals. The latter have previously been shown to have reduced sensitivity to adenosine [Am. J. Physiol. 243 (Heart Circ. Physiol. 12): H252-H258, 1982]. In each group, responses were measured before and after adenosine receptor blockade with aminophylline (10 mg/kg). Responses to infused adenosine were also compared. A linear relationship between adenosine infusion rate and flow was found in all conditions. Aminophylline caused a 70% reduction in adenosine sensitivity in controls. In the diabetics, adenosine sensitivity was much reduced and was identical with blocked controls. A close correlation between left ventricular work and MVO2 was found in both groups. Coronary flow increased linearly with MVO2, and the slopes before and after aminophylline were identical. Myocardial O2 extraction remained unchanged. The same relationships were found in the diabetics, and responses did not differ from controls. Thus, in two conditions of sharply reduced sensitivity to exogeneous adenosine, coronary flow (and resistance) were as equally well matched to MVO2 as in controls. These data suggest that mechanisms other than, or in addition to, adenosine provide the close link between MVO2 and coronary flow with changing cardiac work loads.

Studies of the dynamic response of esophageal manometry systems.

Manometry with fluid-filled catheter systems remains an important technique to study esophageal physiology. The influence of mode of infusion, infusion flow rate, and catheter dimensions on the dynamic response and compliance of such systems was studied. To test the dynamic response, a method based on the step response was developed and applied. A pressure impulse--a step function--was produced by burning off a balloon connected to the system. The response to this well-defined impulse recorded by the system--the step response--was analyzed. The highest frequency to which the system responded satisfactorily--the limiting frequency--was calculated and used as a measure of performance. Compliance and inherent postocclusion pressure rise rate were also determined. In low-compliance systems noninfused or infused by hydraulic capillary infusion, limiting frequencies from 8 to 20 Hz were found, and this was much higher than in a high-compliance system infused by a syringe infusion pump. Smaller diameter and increased length of the manometry catheter decreased the limiting frequency. Increased infusion flow rate did not increase the limiting frequency. The step response test seems to be a simple test of dynamic response that can contribute to better understanding of problems involved in pressure recording with fluid-filled catheter systems. Well-performing fluid-filled manometry systems are adequate for esophageal manometry. Inherent postocclusion pressure rise rate is not a measure of dynamic response, and compliance is not the only determinant of performance.

Factors affecting drug delivery from a syringe-pump infusion set

In vitro testing of drug delivery via dual-lumen, small-volume i.v. extension tubing designed for use with a syringe pump was conducted. From a dual-lumen extension set with intraluminal diameters of 0.020 inch, effluent samples were collected at 5, 10, and 20 minutes after injection of a 1-mL volume of drug solution intended for delivery over 20 minutes by a syringe infusion pump. Variables were flow rate (5 or 25 mL/hr) of the primary infusion, tubing position (vertical or horizontal), and density of the drug solution (penicillin G potassium 250,000 units/mL and aminophylline 25 mg/mL represented high and low specific gravities, respectively). Each drug solution was labeled with radioactive carbon and the drug content of the effluent was analyzed by liquid scintillation. For each set of variables, samples were also tested after the tubing was flushed with 5% dextrose injection 0.2-0.6 mL. Similar procedures were followed to determine delivery of the labeled penicillin G potassium solution via a dual-lumen extension set with intraluminal diameters of 0.020 inch (for drug) and 0.060 inch (for the primary infusion); a 13-mm-diameter, 0.2 micron filter was attached to the smaller-lumen tubing. A primary infusion flow rate of 5 mL/hr and flush volumes of 0.3 and 0.6 mL were used in this study. To determine the influence of intraluminal diameter on the flush volume required for delivery of a dose of aminophylline (1-mL volume), single-lumen extension tubings with different diameters were tested. The final percentage of the drug dose delivered via the dual-lumen extension set with 0.020-inch lumens was affected only by flush volume.(ABSTRACT TRUNCATED AT 250 WORDS)

Evaluation of Blood Cardioplegia Administration Systems

Four different blood cardioplegia administration systems (CAS) were evaluated for ease of use, cooling capacity, uniformity of mixing and blood flow capability. The CAS were one single pass (SP) and three recirculating CAS (RC). Each of the RC had a different reservoir; the first a cardiotomy reservoir (CARD), the second a transfer bag, and the third the GISH system. Each CAS was primed and debubbled with crystalloid. For RC, blood was collected, potassium added, and the solution cooled to 10°C. With SP, the infusate temperature at the field was measured at different flows and oxygenator temperatures. Hematocrit and potassium were measured at the start and end of cardioplegia administration. Single pass had the least tubing, lowest priming volume and the simplest design. For RC, l0°C infusate temperature was obtained fastest with the heat exchanger at the pump outlet and slowest at the reservoir inlet. For SP, the temperature at the field increased as either the oxygenator temperature and/or the cardioplegia flow rate increased. Only RC with CARD produced nonuniform mixing (initial potassium and hematocrit compared to the end of infusion were 16 percent lower and 36 percent higher respectively). At 10°C infusate temperature, RC allowed higher flow rates than SP. The GISH administration tubing had high resistance (800 mmHg at 500 mllmin). GISH is flow-limited by resistance and SP by cooling capacity. Clinically, if oxygenator temperature and infusion flows are such that SP can be used it is preferred. Otherwise, RC with low resistance tubing and heat exchanger within the reservoir is optimal.

“Half‐Way” Venous Catheters

“Half‐way”, Secalon‐Seldy®, soft venous catheters, 40 cm long, were inserted by basilic (n = 90) and cephalic (n = 31) veins at the fossa cubiti in 121 patients (71 men and 50 women) aged between 19 and 88 years whose heights varied from 152–197 cm. The inserted catheter lengths approximated 1/5 of the patient's height. Sixty‐five per cent of 106 radiologically investigated catheter tips were located proximally in the axillary veins, and 34% distally in the subclavian veins. The duration of catheterization varied from 1 to 44 (mean 9±7) days (x ±1 s.d). Perfect function was recorded in 93 of 121 catheters. No serious, but some minor complications were registered such as temporary interruption of infusion flow with movements of the arm (n = 12), partial or total catheter occlusion (n = 16), leakage of the infusate at the insertion site (n = 1), and pain along the vein during infusion (n = 2). Five patients (4%) developed thrombophlebitis 2‐.10 days after insertion. Pull out phlebographies at catheter withdrawal (4–35 days after insertion) were performed in 36 patients. Radiological thrombi were small and similar to those recorded in another 53 phlebographies of “long‐way” brachial catheters of similar stiffness. Neither local infection nor episodes of sepsis were registered over a period of 1,081 catheter days. “Half‐way” catheters proved able to take over all the functions of both peripheral and central venous catheters, lacking the frequent complications (phlebitis and infection) of the former, and the serious mechanical complications (pneumothorax, vein perforations, and injuries of the ductus thoracicus, nerves, arteries, and heart) of the latter.

Evaluation of an extension set for intermittent intravenous drug delivery to infants

An intravenous administration set designed for delivery of drug doses to pediatric patients was tested in vitro for the effect of fluid density and flow rate on drug delivery, and delivery of drug by this extension set was compared in vivo with delivery by other methods. Gentamicin (as the sulfate salt) and penicillin G potassium were used to represent low-density and high-density drugs, respectively; a 1-mL solution of each drug, labeled with carbon 14, was tested with each of two primary infusion solutions: 0.45% sodium chloride injection and 10% dextrose injection. The drug dose was injected via a port into a piston-containing chamber from which an equivalent amount of the primary fluid was displaced. Serial samples collected from the end of the filter-containing extension set were analyzed for drug concentration using a liquid scintillation technique. In 12 infants receiving i.v. gentamicin, this delivery method was compared in a randomized crossover trial with delivery by a syringe pump and by i.v. push. Each delivery system was used on one of three consecutive days, and serum gentamicin concentrations were measured by enzyme-multiplied immunoassay. The time required for in vitro delivery of the dose was dependent on flow rate. Density of the drug solution or the primary i.v. fluid did not significantly affect drug delivery. Serum gentamicin concentrations were not significantly different for the three delivery methods, but variability of drug delivery was greatest with the pediatric extension set. This pediatric extension set provides accurate and reliable drug delivery at primary infusion flow rates slower than 10 mL/hr when the drug dosage volume is 2-3 mL or less.

Intestinal chemosensitivity.

Intestinal chemosensitivity.

Evaluating a filter device used for intermittent intravenous drug delivery to newborn infants

Injection of aminoglycosides into a filter chamber was compared with retrograde injection into i.v. tubing for delivery of intermittent drug dosages at low infusion rates in neonates. In 50 infants receiving gentamicin sulfate and 21 receiving amikacin sulfate for at least two days by retrograde i.v. infusion, peak and trough concentrations of the drugs were obtained. A subsequent dose was administered using the filter device, and peak and trough concentrations were obtained. For each infant, the difference between trough and peak concentration (delta C) was compared for the two methods. In vitro testing for gentamicin concentration was performed using the same infusion systems (10 trials for each system). For both in vivo and in vitro testing, the infusion flow rate was 10 mL/hr. For infants receiving gentamicin, delta C was greater for the filter device in 32, greater for retrograde infusion in 13, and equal in 5. The mean gentamicin delta C was significantly greater for the filter chamber method than for retrograde infusion. The in vitro studies showed significantly better gentamicin recovery with the filter device than with retrograde infusion. For amikacin, delta C was greater for the filter device in 15 infants, but the mean amikacin delta C was not significantly different for the two methods. At low flow rates commonly used in infants, the infusion system using the filter device was equal to or superior to retrograde infusion for ensuring complete delivery of intermittent drug doses.

High-volume crystalloid cardioplegia: An improved method of myocardial preservation

Controlled metabolic studies were used to gauge the relative efficacy of three cardioplegic techniques in 41 patients undergoing multiple coronary artery bypass grafts. Normal-volume (1,946 +/- 155 ml) crystalloid cardioplegia (NVCC) (14 patients) was compared to high-volume (4,961 +/- 282 ml) crystalloid cardioplegia (HVCC) (14 patients) and to blood cardioplegia (BC) (1,672 +/- 127 ml) (13 patients). Measurements of coronary blood flow, coronary vascular resistance, coronary arteriovenous oxygen difference, myocardial oxygen consumption and extraction, and myocardial lactate and potassium extraction and release were all measured in the isolated, vented, paced, beating heart, before and for 20 minutes after a 1 hour arrest interval during which revascularization was completed. Additionally, during administration of the cardioplegic solution, infusion flow rate, myocardial oxygen consumption and extraction, and lactate and potassium release and uptake were noted. The results indicate that during cardioplegic administration, myocardial oxygen consumption is 1 ml O2/min with crystalloid infusion and 2.6 ml O2/min during BC infusion. The volume of crystalloid solution administered contributed to increased oxygen utilization during HVCC compared to NVCC, whereas BC promoted the highest oxygen utilization of the three groups. Potassium absorption was nearly three times greater during BC than during crystalloid administration. During myocardial reperfusion, oxygen extraction was maintained at prearrest levels only in the HVCC group. Following both NVCC and BC, oxygen extraction was depressed during the first 5 minutes of reperfusion, and the difference between the latter two groups and HVCC was significant (p less than 0.01). The rapid recovery in normal metabolic function seen with HVCC allows early discontinuation of cardiopulmonary bypass without myocardial metabolic depression.