A randomized study of the systemic effects of warm heart surgery.

The technique of warm heart surgery is defined as continuous warm blood cardioplegia and normothermic cardiopulmonary bypass. Although the systemic effects of traditional myocardial protection are well known, the effects of warm heart surgery are not. In a prospective trial, 204 patients undergoing coronary artery bypass grafting were randomized to the warm heart surgery technique (normothermic group) or traditional intermittent cold blood cardioplegia and cardiopulmonary bypass (hypothermic group). The groups had similar heparin sodium requirement, activated clotting times, urine output, hematocrit, and blood product utilization. There were no differences in hemodynamics immediately after cardiopulmonary bypass. The normothermic patients had a higher incidence of spontaneous defibrillation at cross-clamp removal (84%) than the hypothermic patients (33%) (p less than 0.01). An increase in the flow rate of low K+ cardioplegia was necessary to eradicate electrical activity during aortic occlusion more often in the normothermic patients (20%) than in the hypothermic patients (3%) (p less than 0.01). When low K+ cardioplegia was ineffective, high K+ cardioplegia was necessary to eradicate electrical activity in 31% of the normothermic patients compared with 10% of the hypothermic patients (p less than 0.05). The total cardioplegia volume delivered to the normothermic group (4.7 +/- 1.9 L) was higher than that delivered to the hypothermic group (2.6 +/- 0.8 L) (p less than 0.01). Although urine output was similar in both groups, the serum K+ levels were higher in the normothermic group (5.7 +/- 0.8 mmol/L) than in the hypothermic group (5.3 +/- 0.8 mmol/L) (p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)     

The efficiency of intermittent antegrade warm blood cardioplegia

We studied the effects of modified Calafiore technique that is intermittent antegrade warm blood cardioplegia including potassium solution and oxygenated with normothermic cardiopulmonary bypass. From January 1996 to March 1997, 45 patients who had undergone elective coronary artery bypass grafting were assigned retrospectively to two groups. Warm group: 25 patients received intermittent antegrade warm blood cardioplegia with normothermic cardiopulmonary bypass. Cold group: 20 patients received intermittent antegrade cold blood cardioplegia with slight hypothermic cardiopulmonary bypass. Preoperative variables were similar in both groups. The rate of sinus rebeating after aorta declamping with DC was lower in warm group than in cold group [warm group 2/25 (8%) versus cold group 8/20 (40%); P < 0.05]. The levels of CK and CK-MB were significantly lower in warm group than in cold group on postoperative day 0. On postoperative day 0 and day 1, the dosage of cathecholamines were significantly less for the warm group than in the cold group. Perioperative events of IABP, PMI and neurological dysfunction were not statistically different. These results show that intermittent antegrade warm blood cardioplegia is a safe and effective method for myocardial protection. But it requires further assessment.     

冷血心脏停搏液及低温心室颤动法在冠状动脉旁路移植术中心肌保护的效果

目的　评价冷血心脏停搏液和低温心室颤动法在冠状动脉旁路移植术 (CABG)中心肌保护的临床效果。方法　根据不同的心肌保护方法 ,将 2 0 13例患者分为两组 ,冷血心脏停搏液组 :5 96例采用冷血心脏停搏液保护心肌 ;低温心室颤动组 :1417例采用低温心室颤动法保护心肌。两组均为单纯、择期 CABG手术 ,观察心肺转流术(CPB)时间 ,升主动脉阻断时间 ,ICU监护期 ,住院死亡率 ,主动脉内气囊泵 (IABP)使用率 ,中枢神经系统并发症及肾功能衰竭发生率。　结果　术中冷血心脏停搏液组与低温心室颤动组旁路移植血管支数无差异 ,冷血心脏停搏液组CPB时间、升主动脉阻断时间明显长于低温心室颤动组 (P<0 .0 1)。术后 ICU监护期、中枢神经系统和肾功能衰竭并发症及术后住院死亡率两组间无差异。　结论　单纯、择期 CABG手术患者 ,低温心室颤动法仍是一种安全、有效的心肌保护方法 ,其临床效果可能优于冷血心脏停搏液法。     

Protection of the hypertrophied pig myocardium. A comparison of crystalloid, blood, and Fluosol-DA cardioplegia during prolonged aortic clamping

The myocardial protective effects of crystalloid, blood, and Fluosol-DA-20% cardioplegia were compared by subjecting hypertrophied pig hearts to 3 hours of hypothermic (10 degrees to 15 degrees C), hyperkalemic (20 mEq/L) cardioplegic arrest and 1 hour of normothermic reperfusion. Left ventricular hypertrophy was created in piglets by banding of the ascending aorta, with increase of the left ventricular weight-body weight ratio from 3.01 +/- 0.2 gm/kg (control adult pigs) to 5.50 +/- 0.2 gm/kg (p less than 0.001). An in vivo isolated heart preparation was established in 39 grown banded pigs, which were divided into three groups to receive aerated crystalloid (oxygen tension 141 +/- 4 mm Hg), oxygenated blood (oxygen tension 584 +/- 41 mm Hg), or oxygenated Fluosol-DA-20% (oxygen tension 586 +/- 25 mm Hg) cardioplegic solutions. The use of crystalloid cardioplegia was associated with the following: a low cardioplegia-coronary sinus oxygen content difference (0.6 +/- 0.1 vol%), progressive depletion of myocardial creatine phosphate and adenosine triphosphate during cardioplegic arrest, minimal recovery of developed pressure (16% +/- 8%) and its first derivative (12% +/- 7%), and marked structural deterioration during reperfusion. Enhanced oxygen uptake during cardioplegic infusions was observed with blood cardioplegia (5.0 +/- 0.3 vol%), along with excellent preservation of high-energy phosphate stores and significantly improved postischemic left ventricular performance (developed pressure, 54% +/- 4%; first derivative of left ventricular pressure, 50% +/- 5%). The best results were obtained with Fluosol-DA-20% cardioplegia. This produced a high cardioplegia-coronary sinus oxygen content difference (5.8 +/- 0.1 vol%), effectively sustained myocardial creatine phosphate and adenosine triphosphate concentrations during the extended interval of arrest, and ensured the greatest hemodynamic recovery (developed pressure, 81% +/- 6%, first derivative of left ventricular pressure, 80% +/- 10%) and the least adverse morphologic alterations during reperfusion. It is concluded that oxygenated Fluosol-DA-20% cardioplegia is superior to oxygenated blood and especially aerated crystalloid cardioplegia in protecting the hypertrophied pig myocardium during prolonged aortic clamping.     

The effects of using a leukocyte removal filter during cold blood cardioplegia

During myocardial ischemia, neutrophils and platelets exert negative effects on the myocardium. In this study, we used a leukocyte removal filter during cardioplegia, and investigated its effect on myocardial damage during reperfusion by measuring the plasma levels of granulocyte components, platelet components, and cardiac enzymes [creatinine phosphokinase (CK) and creatinine phosphokinase myocardial band (CK-MB)] in 24 patients who underwent cardiopulmonary bypass. The patients were divided into two groups of 12 according to whether or not a filter was placed in the cardioplegic route. Blood samples were drawn directly from the coronary sinus before aortic cross clamping, and at 1, 5, and 15 min after declamping. Group F, which had the filter, showed better cardiac enzyme and lipid peroxidation results than group N, which did not. The results of this study suggest that the application of a filter during cold blood cardioplegia may reduce myocardial damage.     

Warm heart surgery

Hypothermia is widely acknowledged to be the fundamental component of myocardial protection during cardiac operations. Although it prolongs the period of ischemic arrest by reducing oxygen demands, hypothermia is associated with a number of major disadvantages, including its detrimental effects on enzymatic function, energy generation, and cellular integrity. We hypothesized that the ideal protected state of the heart would be electromechanically arrested and perfused with blood, that is, aerobic arrest. Under these conditions the fundamental need for hypothermia becomes questionable. We have developed a novel approach to myocardial protection during cardiac operations based on these concepts, in which the chemically arrested heart is perfused continuously with blood and maintained at 37 degrees C. In 121 consecutive coronary bypass procedures we have compared this approach with a historical cohort of 133 consecutive patients treated with hypothermic cardioplegia. Perioperative myocardial infarction was significantly less prevalent (1.7% versus 6.8%; p less than 0.05) in the warm cardioplegic group, as was the use of the intraaortic balloon pump (0.9% versus 9.0%; p less than 0.005) and the prevalence of low output syndrome (13.5% versus 3.3%; p less than 0.005). Cardiac output immediately after bypass was significantly higher than before bypass (3.1 +/- 0.9 versus 4.9 +/- 1.0 L/min; p less than 0.001) only in the warm cardioplegia group. Furthermore, the heartbeat in 99.2% of patients treated with continuous warm cardioplegia converted to normal sinus rhythm spontaneously after removal of the aortic crossclamp compared with only 10.5% of the hypothermic group. The time from removal of the aortic crossclamp to discontinuation of cardiopulmonary bypass (i.e., reperfusion time) was significantly shorter in the warm cardioplegia group (11 +/- 4.3 versus 27 +/- 5.6 minutes; p less than 0.001). Our results suggest that continuous normothermic blood cardioplegia is safe and effective. Conceptually, this represents a new approach to the problem of maintaining excellent myocardial preservation during cardiac operations.     

Hemodynamic and hormonal responses to hypothermic and normothermic cardiopulmonary bypass.

Normothermic cardiopulmonary bypass (CPB) is used in cardiac surgery at some institutions. To compare hemodynamic and hormonal responses to hypothermic (29 degrees C) and normothermic nonpulsatile CPB, 20 adults undergoing coronary artery bypass graft and/or aortic valve replacement were studied. Hemodynamic measurements and plasma hormone concentrations were obtained from preinduction to the third postoperative hour. The two groups were given similar amounts of anesthetics and vasodilators. Systemic vascular resistance increased only during hypothermic CPB, and heart rate was higher at the end of hypothermic CPB. Postoperative central venous pressure and pulmonary capillary wedge pressure were lower after hypothermic CPB. Oxygen consumption decreased by 45% during hypothermic CPB, did not change during normothermic CPB, but increased similarly in the two groups after surgery; mixed venous oxygen saturation (SvO2) was significantly lower during normothermic CPB. Urine output and composition were similar in the two groups. In both groups, plasma epinephrine, norepinephrine, renin activity, and arginine vasopressin concentrations increased during and after CPB. However, epinephrine, norepinephrine, and dopamine were 200%, 202%, and 165% higher during normothermic CPB than during hypothermic CPB, respectively. Dopamine and prolactin increased significantly during normothermic but not hypothermic CPB. Atrial natriuretic peptide increased at the end of CPB and total thyroxine decreased during and after CPB, with no difference between groups. This study suggests that higher systemic vascular resistance during hypothermic CPB is not caused by hormonal changes, but might be caused by other factors such as greater blood viscosity. A higher perfusion index during normothermic CPB might have allowed higher SvO2.     

Cerebral oxygenation is better during mild hypothermic than normothermic cardiopulmonary bypass

PURPOSE: Normothermic cardiopulmonary bypass (CPB) has been recently used in cardiac surgery. However, there is a controversy whether there is a difference in incidence of neurological disorder after coronary artery bypass graft (CABG) surgery between normothermic CPB and mild hypothermic CPB. In this study, we assessed the effects of normothermia and mild hypothermia (32 degrees C) during CPB on jugular oxygen saturation (SjvO2). METHODS: Twenty patients scheduled for elective CABG surgery were divided into two groups. Group 1 (n = 10) underwent normothermic (>35 degrees C) CPB, and Group 2 (n = 10) underwent mild hypothermic (32 degrees C) CPB. Alpha-stat blood gas regulation was applied. After inducing anesthesia, a 4.0 French fibre optic oximetry oxygen saturation catheter was inserted into the right jugular bulb to monitor SjvO2 continuously throughout anesthesia and surgery. RESULTS: The SjvO2 in the normothermic group was decreased at 20 (41.5+/-2.4%) and 40 min (43.8+/-2.8%) after the onset of CPB compared with control (53.9+/-5.4%, P<0.05). However, there was no change in SjvO2 in the mild hypothermic group during the study. No changes in jugular venous-arterial differences of lactate or creatine phosphokinase isoenzyme BB were observed in two groups during the study. CONCLUSIONS: Cerebral oxygenation, as assessed by SjvO2 was increased during mild hypothermic CPB than during normothermic CPB.     

Superior hepatic mitochondrial oxidation-reduction state in normothermic cardiopulmonary bypass

OBJECTIVE: This study is the first comparative investigation of hepatic blood flow and oxygen metabolism during normothermic and hypothermic cardiopulmonary bypass. METHODS: Twenty-four patients undergoing coronary bypass operations were randomly divided into 2 groups according to their perfusion temperatures, either normothermia (36 degrees C) or hypothermia (30 degrees C). The clearance of indocyanine green was measured at 3 points. Arterial and hepatic venous ketone body ratios (an index of mitochondrial redox potential) and hepatic venous saturation were measured. RESULTS: Hepatic blood flow in both groups was identical before, during, and after cardiopulmonary bypass (normothermia, 499 +/- 111, 479 +/- 139, and 563 +/- 182 mL/min, respectively; hypothermia, 476 +/- 156, 491 +/- 147, and 560 +/- 202 mL/min, respectively). The hepatic venous saturation levels were significantly lower during cardiopulmonary bypass in the normothermic group (normothermia, 41% +/- 13%; hypothermia, 61% +/- 18%; P <.01), indicating a higher level of oxygen extraction use. The arterial ketone body ratio in the hypothermic group decreased severely after the onset of cardiopulmonary bypass (P <.01) and did not return to its subnormal value (>0.7) until the second postoperative day. However, the reduction in arterial ketone body ratio was less severe in the normothermic group. The difference in hepatic venous ketone body ratios was more obvious, and the hepatic venous ketone body ratios in the normothermic group were statistically superior to those of the hypothermic group throughout the course (P <.05-.01). CONCLUSIONS: Normothermic cardiopulmonary bypass provides adequate liver perfusion and results in a better hepatic mitochondrial redox potential than hypothermic cardiopulmonary bypass. Because arterial ketone body ratios reflect hepatic energy potential, normothermia was considered to be physiologically more advantageous for hepatic function.     

Core and skin surface temperature course after normothermic and hypothermic cardiopulmonary bypass and its impact on extubation time

BACKGROUND AND OBJECTIVE: Cardiopulmonary bypass is associated with temperature pertubations that influence extubation time. Common extubation criteria demand a minimum value of core temperature only. The aim of this prospective study was to test the hypothesis that changes in core and skin surface temperature are related to extubation time in patients following normothermic and hypothermic cardiopulmonary bypass. METHODS: Forty patients undergoing cardiac surgery were studied; 28 patients had normothermic cardiopulmonary bypass (nasopharyngeal temperature >35.5 degrees C) and 12 had hypothermic cardiopulmonary bypass (28-34 degrees C). In the intensive care unit, urinary bladder temperature and skin surface temperature gradient (forearm temperature minus fingertip temperature: >0 degrees C = vasoconstriction, < or =0 degrees C = vasodilatation) were measured at 30-min intervals for 10 h postoperatively. At the same intervals, the patients were evaluated for extubation according to common extubation criteria. RESULTS: On arrival in the intensive care unit the mean urinary bladder temperature was 36.8 +/- 0.5 degrees C in the normothermic group and 36.4+/-0.3 degrees C in the hypothermic group (P = 0.014). The skin surface temperature gradient indicated severe vasoconstriction in the both groups. The shift from vasoconstriction to vasodilatation was faster in normothermic cardiopulmonary bypass patients (138+/-65 min) than in patients after hypothermic cardiopulmonary bypass (186+/-61 min, P = 0.034). There was a linear relation between the time to reach a skin surface temperature gradient = 0 degrees C and extubation time (r2 = 0.56, normothermic group; r2 = 0.82, hypothermic group). CONCLUSIONS: The transition from peripheral vasoconstriction to vasodilatation is related to extubation time in patients following cardiac surgery under normothermic as well as hypothermic cardiopulmonary bypass.     

Ultrastructural myocardial preservation during coronary artery surgery: a controlled, prospective, randomized study in humans

Potassium cardioplegia was compared with normothermic, intermittent ischemic arrest in 30 patients undergoing multiple coronary artery bypass grafts. Group 1 comprised 15 patients in whom cold potassium cardioplegia with St. Thomas' Hospital solution was used. In Group 2 were 15 patients who underwent intermittent ischemic arrest during the construction of the distal anastomoses. Two myocardial transmural left ventricular biopsies were done in each patient. There was no operative mortality. Electron microscopical examination showed normal myocardial ultrastructure in both groups. In particular, mitochondria were well preserved in all samples. The postoperative electrocardiogram demonstrated a new Q wave in 1 patient in Group 2 whose level of the myocardial isoenzyme of creatine phosphokinase (CPK-MB) was within the normal range. The peak CPK-MB release in Group 1 was 23.2 +/- 20.1 IU and in Group 2, 19.9 +/- 15.1 IU. This difference was not statistically significant. The mean period of anoxic arrest in Group 1 was 49.5 +/- 15 minutes and in Group 2, 25.5 +/- 8 minutes (p less than 0.001). Total cardiopulmonary bypass time in Group 1 was 114.5 +/- 20 minutes and in Group 2, 90.2 +/- 16 minutes (p less than 0.01). It is concluded that both techniques can preserve myocardial subcellular architecture during multiple coronary artery bypass grafting in patients with normal left ventricular function.     

Neutrophil depletion reduces myocardial reperfusion morbidity

BACKGROUND: We tested the hypothesis that depletion of neutrophil leukocytes from the cardioplegic and the initial myocardial reperfusion perfusates reduces clinical indices of reperfusion injury in patients undergoing elective coronary artery bypass. METHODS: We studied 160 consecutive patients who underwent standard coronary revascularization with cardiopulmonary bypass. Patients with recent myocardial infarction or coronary angioplasty were excluded. Cold blood cardioplegia was used. Just before aortic unclamping, the hearts were perfused retrograde with 250 mL of normothermic cardioplegic solution and 750 mL of blood (pump perfusate). Patients were randomly assigned to two groups. In 80 patients (treated), neutrophils and platelets were removed from all cardiac perfusate during aortic crossclamping with leukocyte filtration. In the remaining 80 patients (control group), leukocyte filtration was not used. RESULTS: There was no significant difference between groups in age, sex, severity of disease, and number of bypass grafts implanted. Treated patients showed lower prevalence of low cardiac index and reperfusion ventricular fibrillation and lower levels of creatinine kinase MB isoenzyme and troponin I early postoperatively (p < 0.05). CONCLUSIONS: Neutrophil-filtered blood cardioplegia/reperfusion significantly reduced clinical and biochemical indices of myocardial reperfusion injury after elective coronary revascularization with cardiopulmonary bypass.     

Effects of systemic hypothermia on myocardial metabolism and coronary blood flow in the fibrillating heart.

Ventricular fibrillation during normothermic cardiopulmonary bypass is deleterious to the myocardium. This study was undertaken to determine if moderate systemic hypothermia would protect the myocardium during ventricular fibrillation. Fourteen mongrel dogs were subjected to 1 hour, 15 minutes of total cardiopulmonary bypass. Ventricular fibrillation was induced by a continuous electrical alternating current applied at the beginning of bypass and lasting for 1 hour. Six animals were maintained at normothermia (Group I), and eight were cooled to 30 degrees C. for 1 hour (Group II). The hypothermic group (Group II) demonstrated lower myocardial oxygen consumption and metabolism, decreased coronary blood flow, and less myocardial lactate production during ventricular fibrillation than did Group I. It is concluded that hypothermia does offer some protection, although not complete, against the deleterious effects of ventricular fibrillation described previously.     

Retrograde coronary sinus perfusion prevents infarct extension during intraoperative global ischemic arrest

To determine whether continuous infusion of cardioplegia retrograde through the coronary sinus could improve the salvage of infarcting myocardium, 54 pigs were utilized in a region at risk model. All hearts underwent 30 minutes of reversible coronary artery occlusion, and were divided into six groups. Group 1 served as controls and underwent two hours of coronary reflow without global ischemic arrest. The remaining five groups were subjected to 45 minutes of cardioplegia-induced hypothermic arrest followed by two hours of normothermic reflow. Group 2 had a single infusion of crystalloid cardioplegia, and Group 3 received an oxygenated perfluorocarbon cardioplegic solution initially and again after 20 minutes of ischemia. After initial cardiac arrest with crystalloid cardioplegia, all hearts in Groups 4, 5, and 6 underwent a continuous infusion of a cardioplegic solution retrograde through the coronary sinus. Group 4 received a nonoxygenated crystalloid cardioplegic solution, Group 5 received an oxygenated crystalloid cardioplegic solution, and Group 6 received an oxygenated perfluorocarbon cardioplegic solution. With results expressed as the percent of infarcted myocardium within the region at risk, Group 2 hearts, which received only antegrade cardioplegia, had a mean infarct size of 44.8 +/- 6.3%, a 2.2-fold increase over controls (p less than 0.05). While antegrade delivery of oxygenated perfluorocarbon cardioplegia (Group 3) and coronary sinus perfusion with nonoxygenated crystalloid cardioplegia (Group 4) limited infarct size to 33.6 +/- 4.7% and 35.3 +/- 5.4%, respectively, only oxygenated cardioplegia delivered retrograde through the coronary sinus (Groups 5 and 6) completely prevented infarct extension during global ischemic arrest.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of warm heart surgery on perioperative management of patients undergoing urgent cardiac surgery.

The anesthetic management and outcome data were examined in a retrospective case-controlled study that compared a conventional hypothermic cardioplegic technique with the recently described method of warm heart surgery, in patients undergoing urgent cardiac surgery. Hypothermic continuous oxygenated blood crystalloid cardioplegia with systemic hypothermia was used for 37 patients who underwent cardiac surgery by the same surgeon over a 16-month period from July 1986 (group 1), whereas normothermic continuous oxygenated blood crystalloid cardioplegia with systemic normothermia was used on 56 patients over the following 16-month period until March 1990 (group 2). The groups were similar in terms of age, sex, ASA status, NYHA classification, and preoperative left ventricular function. Defibrillation following cardiopulmonary bypass was required in only 3.6% of the warm heart surgery patients (group 2) compared with 83.8% in group 1 (P less than 0.0001), and use of warm heart surgery (group 2) eliminated the need for rewarming. There was a trend towards a reduced incidence of myocardial infarction (19% in group 1 vs 9% in group 2), low cardiac output syndrome (40% vs 29%), and use of the intraaortic balloon pump (16% vs 9%) in warm heart surgery patients, but these differences did not reach statistical significance. There were no differences between the two groups in terms of anesthetic drug usage, total heparin or protamine doses, blood loss, transfusion requirements, or duration of ICU stay.(ABSTRACT TRUNCATED AT 250 WORDS)     

Acadesine (AICA-riboside) improves postischemic cardiac recovery.

To test if acadesine (5-aminoimidazole-4-carboxamide riboside), a purine precursor, has cardioprotective effects, 16 dogs were placed on total cardiopulmonary bypass and subjected to global myocardial ischemia. Hemodynamic recovery was compared between a control (n = 8) group receiving standard cardioplegia and an acadesine (n = 8) group pretreated with intravenous acadesine (2.5 mg.kg-1.min-1 for 5 minutes, then 0.5 mg.kg-1.min-1) before ischemia, during ischemia, and until 10 minutes after removal of the aortic cross-clamp. Additionally, in the acadesine group the cardioplegia also contained 20 mumol/L acadesine. While the dogs were on cardiopulmonary bypass, global warm myocardial ischemia was induced by aortic cross-clamping for 5 minutes under normothermic conditions to simulate an angioplasty accident. Five minutes after aortic cross-clamping, hypothermic cardioplegia (30 mL/kg) was administered. The left anterior descending coronary artery was occluded before the first infusion of cardioplegia to simulate poor cardioplegia delivery that can occur during an emergency coronary artery bypass procedure after an angioplasty accident. The left anterior descending artery occlusion was released, and additional cardioplegia (15 mL/kg) infusions were made every 30 minutes thereafter during 120 minutes of cardioplegic ischemia. Thirty minutes after reperfusion, all animals in both groups were weaned from bypass and recovery data were obtained to compare with baseline preischemic values. There were no significant differences in heart rate, left atrial pressure, or systemic vascular resistance between groups after weaning from bypass. Peak developed pressure recovered to 79% +/- 19% (mean +/- standard deviation) of baseline in the acadesine group compared with 56% +/- 22% in the control group (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)     

Myocardial protection during heart surgery. An experimental evaluation of normothermic and hypothermic cardioplegia.

Heart surgery with hypothermic cardioplegia during normothermic bypass is sometimes complicated by rewarming of the myocardium caused by collateral flow of arterial blood. This problem is particularly evident in surgery of congenital malformations. The present work is a comparative study in dogs on 3 methods of avoiding the rewarming problem. In the first group, the heart was kept cold and the warm blood was drained off from the left atrium. In the second group, total body hypothermia to the level desired was used and in the third group, normothermic cardioplegia was induced (Cardioplegin) in normothermic animals. In the two latter groups, the undesired temperature gradient between heart and body was eliminated. Evaluation of the differences was made by means of ventricular function determinations. Local, hypothermic cardioplegia showed the best postoperative function (69%) followed by the total body cooling which was fully acceptable (41%). Normothermic cardioplegia after the same duration of arrest showed a too low myocardial performance (20%).     

Warm Heart Surgery Eliminates Diaphragmatic Paralysis

Since January 1992, we adopted a new method of myocardial protection: warm blood cardioplegia with continuous ante-retrograde combined delivery during normothermic cardiopulmonary bypass, (CPB) instead of cold blood intermittent cardioplegia plus topical ice slush in hypothermic CPB. We have compared postoperative chest X-rays of 50 patients who underwent elective coronary artery bypass with normothermic CPB to postoperative chest X-rays, of 50 patients operated upon with hypothermia. In the cold group transitory diaphragmatic paralysis, as well as pleural effusions and thoracentesis related to the hypothermia, and topical cooling, were statistically increased over that of the warm group. The data suggest that topical cooling with slush ice is responsible for phrenic nerve injury and that warm heart surgery has no associated incidence of diaphragmatic injury.     

Continuous measurement of intramyocardial pH: correlation to functional recovery following normothermic and hypothermic global ischemia

The continuous measurement of intramyocardial pH was used to follow the progression of ischemia and was correlated to the recovery of left ventricular function following normothermic (38 degrees C) and hypothermic (25 degrees C) global ischemia. New miniature myocardial transducers, which incorporate fiberoptic technology and dual pH- and temperature-sensing capability, were placed into the left ventricular free wall and septum of 52 sheep undergoing cardiopulmonary bypass. Left ventricular stroke work as a function of mean left atrial pressure curves were generated before and after cardiopulmonary bypass by volume loading with whole blood. Functional recovery was determined by the ratio of the integrals of the preischemic and postischemic function curves. Control sheep (N = 11) did not undergo ischemia. Three groups (N = 41) underwent aortic cross-clamping until pH reached 7.0, 6.8, or 6.6. The preischemic myocardial pH averaged 7.42 +/- 0.01. Following both normothermic and hypothermic global ischemia, no significant difference was demonstrated in recovery of function between control (pH 7.4) and pH 7.0 groups at either temperature. However, recovery of function of the pH 6.8 and pH 6.6 groups was significantly decreased (p less than 0.01) versus control and pH 7.0 groups at both temperatures. No significant difference in recovery of function was demonstrated at any pH level when normothermic versus hypothermic groups were compared. However, hypothermia provided increased time (p less than 0.001) before each level of function was reached with a slower rate of change of pH (p less than 0.01) compared with the corresponding same pH group in sheep undergoing normothermic (38 degrees C) cardiopulmonary bypass.(ABSTRACT TRUNCATED AT 250 WORDS)     

Comparative study of hypothermic circulatory arrest and normothermic distal perfusion for thoracoabdominal aortic aneurysm repair

BACKGROUND: Hypothermic bypass with circulatory arrest for thoracoabdominal aortic aneurysm (TAAA) repair is employed for its protective effect on spinal cord function and because it avoids clamping the diseased aorta. However, organ dysfunction caused by reperfusion injury as well as bleeding tendencies due to deep hypothermia have been described. In this paper we compared the efficacies of the hypothermic and normothermic operations. METHODS: Between February 1996 and June 2000, 28 patients underwent thoracoabdominal aortic repair. Twenty-three patients were men, 5 were women, and the median age was 55.3 (range 23 to 75 years). Fourteen patients had aortic dissection, and 7 had Marfan syndrome. Fourteen patients required reconstruction of visceral arteries. Twelve patients underwent TAAA repair under deep hypothermic circulatory arrest (H group), and 15 under normothermic distal perfusion (N group), while 1 patient underwent a simple clamp procedure. Perioperative data and early outcomes were compared between groups. RESULTS: The overall 30-day mortality rate was 0%, but 3 patients (25.0%) in II group, and 1 patient (6.3%) in N group died during hospital stay. Operation time and bypass time were longer in H group than N group (operative time 793 min vs. 481 min (p < 0.05): cardiopulmonary bypass (CPB) time 255 min vs. 102 min (p < 0.05). Also, more intraoperative bleeding was found in H group than in N group (3,506 ml vs. 1,220 ml). Spinal cord neurologic deficit did not occur in either group. Respiratory failure occurred in 3 patients (25.0%) in H group and one (6.3%) in N group. Renal failure occurred in 3 (25.0%) in H group, and none in N group. CONCLUSION: Early and mid-term outcome of TAAA repair was almost satisfactory and without neurospiral complications. The deep hypothermic operation is more likely to induce postoperative respiratory and renal dysfunction than the normothermic operation. TAAA repair using deep hypothermic circulatory arrest should be limited to patients with TAAA involving the distal arch or a severely calcified aortic wall.