Normothermic techniques during open heart operations

Normothermic versus hypothermic cardiopulmonary bypass in children undergoing open heart surgery (thermic-2): study protocol for a randomized controlled trial

Background

During open heart surgery, patients are connected to a heart-lung bypass machine that pumps blood around the body (“perfusion”) while the heart is stopped. Typically the blood is cooled during this procedure (“hypothermia”) and warmed to normal body temperature once the operation has been completed. The main rationale for “whole body cooling” is to protect organs such as the brain, kidneys, lungs, and heart from injury during bypass by reducing the body’s metabolic rate and decreasing oxygen consumption. However, hypothermic perfusion also has disadvantages that can contribute toward an extended postoperative hospital stay. Research in adults and small randomized controlled trials in children suggest some benefits to keeping the blood at normal body temperature throughout surgery (“normothermia”). However, the two techniques have not been extensively compared in children.

Objective

The Thermic-2 study will test the hypothesis that the whole body inflammatory response to the nonphysiological bypass and its detrimental effects on different organ functions may be attenuated by maintaining the body at 35°C-37°C (normothermic) rather than 28°C (hypothermic) during pediatric complex open heart surgery.

Methods

This is a single-center, randomized controlled trial comparing the effectiveness and acceptability of normothermic versus hypothermic bypass in 141 children with congenital heart disease undergoing open heart surgery. Children having scheduled surgery to repair a heart defect not requiring deep hypothermic circulatory arrest represent the target study population. The co-primary clinical outcomes are duration of inotropic support, intubation time, and postoperative hospital stay. Secondary outcomes are in-hospital mortality and morbidity, blood loss and transfusion requirements, pre- and post-operative echocardiographic findings, routine blood gas and blood test results, renal function, cerebral function, regional oxygen saturation of blood in the cerebral cortex, assessment of genomic expression changes in cardiac tissue biopsies, and neuropsychological development.

Results

A total of 141 patients have been successfully randomized over 2 years and 10 months and are now being followed-up for 1 year. Results will be published in 2015.

Conclusions

We believe this to be the first large pragmatic study comparing clinical outcomes during normothermic versus hypothermic bypass in complex open heart surgery in children. It is expected that this work will provide important information to improve strategies of cardiopulmonary bypass perfusion and therefore decrease the inevitable organ damage that occurs during nonphysiological body perfusion.

Trial Registration

ISRCTN Registry: ISRCTN93129502, http://www.isrctn.com/ISRCTN93129502 (Archived by WebCitation at http://www.webcitation.org/6Yf5VSyyG).

Successful treatment of accidental air embolism in warm heart surgery

Normothermic cardiopulmonary bypass has recently been proposed as a superior technique for maintaining body metabolism. However, its use remains controversial since the degree of cerebral protection provided might be inferior to that conferred by conventional hypothermic techniques. We report a case of accidental massive air embolism during coronary artery bypass surgery under normothermia, which was successfully managed with induced hypothermia at 20 degrees C and retrograde cerebral perfusion.

Comparing dual-stream and standard cardiopulmonary bypass in pigs

BACKGROUND

Dual-stream (DS) and standard cardiopulmonary bypass (CPB) were compared.

METHODS

A DS catheter inserted into the distal ascending aorta across the arch pumps blood through an upper lumen (maximum 2.25 L/min) directed by a bloodstreaming baffle toward the arch vessels. A separate lower lumen pumps blood (maximum 3.75 L/min) into the aorta caudad to the inflated baffle. The baffle is flat and horizontal along the catheter. When the baffle is collapsed the heart or both lumens may perfuse all organs. For 30 minutes 8 randomized CPB pigs had corporeal cooling to 32 degrees C and for 30 minutes had rewarming to 36 degrees C. Eight randomized DS pigs had 25 degrees C upper lumen cooling for 60 minutes. Lower lumen blood flow was streamed at 32 degrees C for 30 minutes, then rewarmed to 36 degrees C for 30 minutes.

RESULTS

The change in relative lower lumen to brain blood flow as determined by brain-counted microspheres (15 micron) injected into the ascending aorta was less for DS brains than controls during full flow (DS 63.4+/-129.5 versus CPB 2,585.4+/-250.8, p < 0.001), and when injected into the ejecting-heart left atrium just after weaning off only lower lumen blood flow (DS 250.8+/-297.3 versus CPB 1,159.1+/-782.3, p < 0.001). DS brain temperatures were lower at an equal pump-off core temperature of 36 degrees C+/-0.5 degrees C (DS 31.6 degrees C+/-3.2 degrees C versus CPB 36.5 degrees C+/-1.7 degrees C, p < 0.025). Jugular O2 saturations were not different.

CONCLUSIONS

DS-CPB prioritizes pump-filtered separate cold blood flow to the brain over a blood-streaming baffle to wash away potentially surgery related air and particulate matter arising from the heart or ascending aorta.

Combined Surgery for cardiac and carotid disease: management and results of a rational approach

OBJECTIVES

The aim of the present study was to apply a rational plan for simultaneous cardiac and carotid surgery in high-risk patients.

MATERIALS AND METHODS

A consecutive series of 89 patients with coexisting severe cardiac and carotid disease were operated on during a 5-year period with routinary carotid shunting, moderate hypothermia and balanced anaesthesia. The combined surgical procedures were coronary artery by-pass grafts (CABG) + carotid endarterectomy (CEA) in 81 patients, CABG + CEA + aortic valve replacement (AVR) in four patients, and four cases of CEA + AVR. RESSULTS: Two deaths (2%), three acute myocardial infarctions (3%) and one (1%) major stroke occurred in five patients during the perioperative (30 days) period for a combined rate of death and/or disabling stroke of 3%. There were five reversible neurological deficits. Carotid and aortic mean clamping times were 9 and 60 min respectively. Patients were discharged after a mean length of stay in Intensive Care Unit (ICU) of 131 h and 7 days of hospitalisation post-ICU.

CONCLUSIONS

Based on our results, combined interventions of CEA and CABG can be performed with an acceptable morbidity and mortality when severe carotid stenosis is associated with advanced, symptomatic cardiac disease. The management of these patients needs careful and appropriate pre-intra and post-operative assessment and timing aimed to reduce the ischaemic injuries, both cardiac and cerebral, especially during CBP time.

Thromboelastography-guided transfusion algorithm reduces transfusions in complex cardiac surgery

Transfusion therapy after cardiac surgery is empirically guided, partly due to a lack of specific point-of-care hemostasis monitors. In a randomized, blinded, prospective trial, we studied cardiac surgical patients at moderate to high risk of transfusion. Patients were randomly assigned to either a thromboelastography (TEG)-guided transfusion algorithm (n = 53) or routine transfusion therapy (n = 52) for intervention after cardiopulmonary bypass. Coagulation tests, TEG variables, mediastinal tube drainage, and transfusions were compared at multiple time points. There were no demographic or hemostatic test result differences between groups, and all patients were given prophylactic antifibrinolytic therapy. Intraoperative transfusion rates did not differ, but there were significantly fewer postoperative and total transfusions in the TEG group. The proportion of patients receiving fresh-frozen plasma (FFP) was 4 of 53 in the TEG group compared with 16 of 52 in the control group (P < 0.002). Patients receiving platelets were 7 of 53 in the TEG group compared with 15 of 52 in the control group (P < 0.05). Patients in the TEG group also received less volume of FFP (36 +/- 142 vs 217 +/- 463 mL; P < 0.04). Mediastinal tube drainage was not statistically different 6, 12, or 24 h postoperatively. Point-of-care coagulation monitoring using TEG resulted in fewer transfusions in the postoperative period. We conclude that the reduction in transfusions may have been due to improved hemostasis in these patients who had earlier and specific identification of the hemostasis abnormality and thus received more appropriate intraoperative transfusion therapy. These data support the use of TEG in an algorithm to guide transfusion therapy in complex cardiac surgery.

IMPLICATIONS

Transfusion of allogeneic blood products is common during complex cardiac surgical procedures. In a prospective, randomized trial, we compared a transfusion algorithm using point-of-care coagulation testing with routine laboratory testing, and found the algorithm to be effective in reducing transfusion requirements.

Thromboelastography-guided transfusion algorithm reduces transfusions in complex cardiac surgery

Transfusion therapy after cardiac surgery is empirically guided, partly due to a lack of specific point-of-care hemostasis monitors. In a randomized, blinded, prospective trial, we studied cardiac surgical patients at moderate to high risk of transfusion. Patients were randomly assigned to either a thromboelastography (TEG)-guided transfusion algorithm (n = 53) or routine transfusion therapy (n = 52) for intervention after cardiopulmonary bypass. Coagulation tests, TEG variables, mediastinal tube drainage, and transfusions were compared at multiple time points. There were no demographic or hemostatic test result differences between groups, and all patients were given prophylactic antifibrinolytic therapy. Intraoperative transfusion rates did not differ, but there were significantly fewer postoperative and total transfusions in the TEG group. The proportion of patients receiving fresh-frozen plasma (FFP) was 4 of 53 in the TEG group compared with 16 of 52 in the control group (P < 0.002). Patients receiving platelets were 7 of 53 in the TEG group compared with 15 of 52 in the control group (P < 0.05). Patients in the TEG group also received less volume of FFP (36 +/- 142 vs 217 +/- 463 mL; P < 0.04). Mediastinal tube drainage was not statistically different 6, 12, or 24 h postoperatively. Point-of-care coagulation monitoring using TEG resulted in fewer transfusions in the postoperative period. We conclude that the reduction in transfusions may have been due to improved hemostasis in these patients who had earlier and specific identification of the hemostasis abnormality and thus received more appropriate intraoperative transfusion therapy. These data support the use of TEG in an algorithm to guide transfusion therapy in complex cardiac surgery.

IMPLICATIONS

Transfusion of allogeneic blood products is common during complex cardiac surgical procedures. In a prospective, randomized trial, we compared a transfusion algorithm using point-of-care coagulation testing with routine laboratory testing, and found the algorithm to be effective in reducing transfusion requirements.

The effect of three different doses of tranexamic acid on blood loss after cardiac surgery with mild systemic hypothermia (32 degrees C)

OBJECTIVE

Prophylactic administration of tranexamic acid (TA), an antifibrinolytic agent, decreases bleeding after cardiac surgery with systemic hypothermia (25 degrees C to 29 degrees C). Warmer systemic temperatures during cardiopulmonary bypass (CPB) may reduce bleeding and thus alter the requirement for TA. The effect of three different doses of TA on bleeding after cardiac surgery with mild systemic hypothermia (32 degrees C) is evaluated.

DESIGN

Double-blind, prospective, randomized study.

SETTING

University hospital.

PARTICIPANTS

One hundred fifty adult patients undergoing aortocoronary bypass or valvular cardiac surgery.

INTERVENTIONS

Patients received TA, 50 (n = 50), 100 (n = 50), or 150 (n = 50) mg/kg intravenously before CPB with mild systemic hypothermia.

MEASUREMENTS AND MAIN RESULTS

Blood loss through chest drains over 6, 12, and 24 hours after surgery and total hemoglobin loss were measured. Autotransfused blood, transfused banked blood and blood products, and coagulation profiles were measured. Analysis of variance on log-transformed data for blood loss and confidence intervals (CIs) of 0.95 were calculated and transformed to milliliters of blood. No patient was re-explored for bleeding. Blood loss at 6 hours was statistically greater in the 50-mg/kg group compared with the other two groups (p = 0.03; p = 0.02). Total hemoglobin loss was statistically greater in the 50-mg/kg group compared with the 150-mg/kg group (p = 0.04). There was no statistical difference in blood tranfusion rate or coagulation profiles among the three groups. However, preoperative hemoglobin level was statistically lower in the 150-mg/kg group compared with the other two groups (p = 0.01).

CONCLUSION

Of the three doses of TA studied, the most efficacious and cost-effective dose to reduce bleeding after cardiac surgery with mild hypothermic systemic perfusion is 100 mg/kg.

Intermittent antegrade tepid versus cold blood cardioplegia in elective myocardial revascularization

BACKGROUND

The ideal temperature for blood cardioplegia administration remains controversial.

METHODS

Fifty-two patients who required elective myocardial revascularization were prospectively randomized to receive intermittent antegrade tepid (29 degrees C; group T, 25 patients) or cold (4 degrees C; group C, 27 patients) blood cardioplegia.

RESULTS

The two cohorts were similar with respect to all preoperative and intraoperative variables. The mean septal temperature was higher in group T (T, 29.6 degrees +/- 1.1 degrees C versus 17.5 degrees +/- 3.0 degrees C; p < 0.0001). After reperfusion, group T exhibited significantly greater lactate and acid release despite similar levels of oxygen extraction (p < 0.05). The creatine kinase-MB isoenzyme release was significantly lower in group T (764 +/- 89 versus 1,120 +/- 141 U x h/L; p < 0.04). Hearts protected with tepid cardioplegia demonstrated significantly increased ejection fraction with volume loading, improvement in left ventricular function at 12 hours, and decreased need for postoperative inotropic support (p < 0.05). The frequency of ventricular defibrillation after cross-clamp removal was lower in this cohort (p < 0.05). There were no hospital deaths, and both groups had similar postoperative courses.

CONCLUSIONS

Intermittent antegrade tepid blood cardioplegia is a safe and efficacious method of myocardial protection and demonstrates advantages when compared with cold blood cardioplegia in elective myocardial revascularization.

[Early recovery after valvular heart surgery]

There have been published not a few reports concerning the early recovery from heart surgery. But most of them were restricted in CABG cases. We report our efforts and its results about the early recovery from valvular heart surgery. To make a contribution to the early recovery we have made some efforts since 1995, including normothermic perfusion, low-dose fentanyl and introduction of terminal warm blood cardioplegia. As the results, the tracheal intubation period was shortened from 12.6 +/- 5.3 (hour) to 6.7 +/- 4.1. The number of the cases who had tracheal extubation in the operative day increased from 27% to 84%. The postoperative cardiac function was satisfactory and there were no abdominal or neurologic disturbances among the patients those who were entered into the early recovery protocol. We obtained satisfied early recovery in safe after valvular heart surgery.