Influence of normothermic systemic perfusion temperature on cold myocardial protection during coronary artery bypass surgery

Mild Hypothermia May Offer Some Improvement to Patients with MODS after CPB Surgery

OBJECTIVE:

To summarize the effect of mild hypothermia on function of the organs in patients with multiple organ dysfunction syndrome after cardiopulmonary bypass surgery.

METHODS:

The patients were randomly divided into two groups, northermia group (n=71) and hypothermia group (n=89). We immediately began cooling the hypothermia group when test results showed multiple organ dysfunction syndrome, meanwhile all patients of two groups were drawn blood to test blood gas, liver and kidney function, blood coagulation function, and evaluated the cardiac function using echocardiography from 12 to 36 hours. We compared the difference of intra-aortic balloon pump, extracorporeal membrane oxygenation rate and mortality within one month after intensive care unit admission.

RESULTS:

Among the 160 patients, 36 died, 10 (11.24%) patients were from the hypothermia group and 26 (36.6%) from the northermia group (P <0.05). In northermia group, 45 (63.38%) patients used intra-aortic balloon pump and 4 (5.63%), extracorporeal membrane oxygenation; in hypothermia group, 35 (39.32%) patients used intra-aortic balloon pump and 2 (2.25%), extracorporeal membrane oxygenation（ P <0.05). The patients' heart rate decreased significantly in the hypothermia group. The heart rate of hypothermia group is significantly slower than the northermia group at the 36^th hour (P <0.05). But the mean arterial pressure of hypothermia group is significantly higher than the northermia group at the 36^th hour (P <0.05). In hypothermia group, PO₂, SvO₂ and lactate were improved significantly compared to pre-cooling (P <0.05), and they were significantly better than the northermia group at the 36^th hour (P <0.05%). Prothrombin time and activated partial thromboplastin time have no significantly difference between the two groups (P >0.05). But the platelet count has significantly difference between the two groups at the 36^th hour (P <0.05). The aspartate transaminase, alanine transaminase and creatinine were improved significantly in the hypothermia group, and they were significantly better than the northermia group (P <0.05).

CONCLUSION:

Mild hypothermia is feasible and safe for patients with multiple organ dysfunction syndrome after cardiopulmonary bypass surgery.

High-Sensitivity Troponin Release Profile After Cardiac Surgery

BACKGROUND

Postoperative serum troponin levels and perioperative myocardial infarction (MI) rates correlate with mortality and morbidity following cardiac surgery. The objective of this study was to document the release profile of high sensitivity troponin T (hsTnT) following different cardiac operations.

METHODS

Patients undergoing one of five different isolated cardiac surgical procedures (eligible preoperative hsTnT <29ng/L, serum creatinine < 0.2mmol/L) were recruited prospectively. Serum hsTnT was measured at 0, 4, 6, 8, 10, 12, 24 and 72hours after the first surgical insult to myocardium, together with daily electrocardiographs.

RESULTS

There were 10 patients in the on-pump coronary artery bypass group and 5 each in the remaining groups (off-pump coronary artery bypass, open aortic valve replacement, transcutaneous aortic valve implantation and mitral valve replacement). Five additional patients were excluded due to perioperative MI or renal failure. Median [range] of peak hsTnT was 241[99-566], 64[50-136], 353[307-902], 115[112-275], and 918[604-1166] ng/L, respectively. Operations with the lowest peak hsTnT values peaked earliest (four hours) while those with highest values peaked latest (eight hours).

CONCLUSION

After cardiac surgery, the hsTnT profile peaks four to eight hours after the initial surgical insult. The magnitude and timing of the peak correlates to the expected degree of surgically-induced myocardial injury.

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).

Hypothermic versus normothermic cardiopulmonary bypass in patients with valvular heart disease

OBJECTIVE

The aim of this study was to test the hypothesis that normothermic cardiopulmonary bypass (CPB) is as effective as hypothermic CPB in terms of cardiac protection (cTnI level) and outcome in patients with valvular heart disease.

DESIGN

Prospective randomized study.

SETTING

A tertiary cardiothoracic referral center.

PARTICIPANTS

140 patients who had valvular heart disease, with/without coronary artery disease, surgically treated under CPB.

INTERVENTIONS

The patients were allocated randomly to undergo either hypothermic (temperature [T], 31 °C-32 °C) or normothermic CPB (T>36 °C).

MEASUREMENTS AND MAIN RESULTS

The primary endpoint was the dynamics of troponin I. The secondary endpoints were ventilation time, the need for inotropic support, intensive care unit (ICU) and hospital stay durations, complications, and mortality. There were no significant intergroup differences in dynamics of troponin I. Ventilation time was significantly lower in the hypothermic group (6 (5-9) and 8 (5-12); p = 0.01).

CONCLUSIONS

Normothermic CPB in patients with valvular heart disease was as effective as hypothermic perfusion in terms of myocardial protection after the surgery assessed by cTnI release. The short ventilation duration in patients who underwent hypothermic CPB needs to be confirmed in a future investigation.

Myocardial cooling with ice-slush provides no cardioprotective effects in aortic valve replacement

OBJECTIVES

Topical cooling of the heart with ice-slush has been widely used for myocardial protection. No prospective, randomized study has evaluated the effect of ice-slush on acknowledged markers (CK-MB, troponin-T) of myocardial damage during aortic valve replacement (AVR). This was the first aim of the present study. A second aim was to examine whether performing a study per se reduced myocardial damage.

DESIGN

Sixty patients undergoing AVR were receiving cold crystalloid antegrade cardioplegia every 20 min. Thirty patients were randomized to achieve additional topical cooling with ice-slush. CK-MB and troponin-T were compared between groups as well as to a group of patients undergoing AVR immediately prior to the study.

RESULTS

There were no significant differences in myocardial markers between patients with or without ice-slush. However, we found significantly higher levels of troponin-T and CK-MB in patients undergoing AVR prior to start of the study.

CONCLUSIONS

Topical cooling with ice-slush does not provide additional cardioprotective effects. Comparison with an historical cohort indicates that administration of crystalloid cardioplegia following a rigid protocol might reduce myocardial damage.

Randomized Comparison Between Normothermic and Hypothermic Cardiopulmonary Bypass in Pediatric Open-Heart Surgery

BACKGROUND

The purpose of this study is to investigate the effect of cardiopulmonary bypass (CPB) temperature on myocardial reperfusion injury, oxidative stress, and inflammatory response in pediatric open heart surgery.

METHODS

Fifty-nine children (median age 78 months; interquartile range, 39-130) undergoing correction of simple congenital heart defects were randomized to receive either hypothermic (28 degrees C) or normothermic (35-37 degrees C) CPB. Troponin I and 8-isoprostane, complement activation C3a, interleukin (IL) -6, -8, and -10, were measured preoperatively, on removal of the aortic cross clamp, 30 minutes, 6, and 24 hours postoperatively.

RESULTS

Troponin I and 8-isoprostane were significantly raised, compared to baseline, in both groups, and remained high at 24 hours. Overall, troponin I and 8-isoprostane levels were 37% and 84% higher in the hypothermic than in the normothermic group, respectively (ratio 1.37, 95% CI 1.00 to 1.88, p = 0.053 and 1.84, 95% CI 1.22 to 2.78, p = 0.0045, respectively), and there was no evidence to suggest the treatment effect changed significantly over the time points measured (p = 0.63). Adjusting for aortic cross-clamp time reduced the effect of hypothermia on troponin (p = 0.18) but not on 8-isoprostane levels (p = 0.0028). The C3a, IL-6, and IL-8 release was similar in the two groups. The IL-10 release between the groups changed over time (p = 0.059) and examining differences at individual time points highlighted a statistically significant difference at the end of the cross-clamp time (p = 0.0079).

CONCLUSIONS

Normothermic CPB is associated with reduced oxidative stress compared with hypothermic CPB, and similar myocardial reperfusion injury and whole body inflammatory response, in children undergoing open heart surgery. A larger study with clinical outcomes as primary end points is now warranted.

Topical cardiac cooling--computer simulation of myocardial temperature changes

Topical cardiac cooling (TC) is often used in cardiac surgery. We used a computer simulation to study temperature changes in the heart, especially in the right ventricular wall. A three-dimensional computer heart model, derived from Visible Human Data set, National Library of Medicine was used. The model is made from cubes, with spatial resolution of 1mm. Explicit Finite Different method and temperature diffusion equation were used to calculate new temperatures. Three different simulations were performed and simulated temperatures were drawn on a cross-section of heart model in different colors. The results show that areas not immersed into TC solution are less protected against ischemia. It is important not to rely solely on topical cooling but use appropriate method of myocardial protection technique.

Assessment of myocardial injury by troponin T in off-pump coronary artery grafting and conventional coronary artery graft surgery

PURPOSE

The present study was undertaken to assess the degree of myocardial injury, using troponin T (TnT), in off-pump coronary artery surgery (OPCAB) and in a comparable patient group undergoing conventional coronary artery graft surgery (CABG).

METHODS

Twenty-seven OPCAB and 27 CABG patients were investigated. Blood samples for TnT were taken at intubation and at 12, 24 and 72 h. Nine patients (five OPCAB, four CABG) underwent 2 h sampling for 12 h for the assessment of the TnT release profile. All patients had an electrocardiogram performed preoperatively and on the mornings of days 1 and 5 postoperatively.

RESULTS

The OPCAB group had significantly greater Canadian Heart Classification 3 patients (P = 0.003); however, other demographic data were similar between the two groups. All patients had normal TnT at initial sampling. The mean number of grafts in each group was 1.8 +/- 0.6 for OPCAB and 1.9 +/- 0.3 for CABG (P = NS). There were two new Q wave myocardial infarctions in the CABG group and none in the OPCAB group. These cases were excluded from biochemical analyses. Troponin T release was significantly less in the OPCAB group at 12 and 24 h (P < 0.001 and P = 0.03, respectively). Peak TnT release occurred at 6-8 h in both groups. Troponin T release was significantly lower in the OPCAB group at 2, 4, 6, 8, 10 and 12 h (P = 0.01, P = 0.03, P = 0.02, P = 0.02, P = 0.03 and P = 0.04, respectively). Postoperatively, the OPCAB group required less blood transfusion (P = 0.02).

CONCLUSIONS

The OPCAB group demonstrated a significantly reduced TnT release profile compared with the CABG group.

Monitoring the Hematologic Complications of Cardiopulmonary Bypass

Patients undergoing cardiopulmonary bypass (CPB) procedures have a variety of hemostatic defects that lead to bleeding and the frequent need for transfusion of allogeneic blood products. Dilution of the patient's blood volume by the extracorporeal circuit priming so lution causes depletion of platelets and coagulation factor levels. Contact of blood with the extracorporeal circuit induces a hemorrhagic diathesis through a vari ety of mechanisms. Contact activation causes the for mation of kallikrein, bradykinin, and complement acti vation, leading to a whole-body inflammatory reaction. Intrinsic coagulation is stimulated, leading to subse quent activation of the fibrinolytic system. Platelet dys function caused by the effects of the extracorporeal circuit on platelet membrane integrity and the effects of circulating platelet inhibitors have also been described. The use of high-dose heparin for CPB mitigates these effects but does not completely eliminate them. Prota mine, administered to antagonize heparin's effects, has antiplatelet properties and anticoagulant effects when given in excess. Because of the numerous hemostatic insults incurred during and after CPB, complex moni toring techniques are necessary to ensure adequate anticoagulation, adequate heparin neutralization, and normal platelet function. Coagulation monitoring has allowed more specific identification of particular distur bances of hemostasis and has been linked with a reduc tion in hemorrhagic complications after CPB. Copyright © 2001 by W.B. Saunders Company.

Hypothermia to reduce neurological damage following coronary artery bypass surgery

BACKGROUND

Coronary artery bypass surgery (CABG) may be life saving, but known side effects include neurological damage and cognitive impairment. The temperature used during cardiopulmonary bypass (CPB) may be important with regard to these adverse outcomes, where hypothermia is used as a means of neuroprotection.

OBJECTIVES

To assess the effectiveness of hypothermia during CABG in reducing neurological damage and subsequent cognitive deficits.

SEARCH STRATEGY

The Cochrane Controlled Trials Register was searched for randomised controlled trials (RCT) and this was updated by searching MEDLINE and EMBASE to December 1999 using database specific RCT filters. Reference lists of retrieved articles were searched and experts in the field were contacted.

SELECTION CRITERIA

Only RCTs were considered. All patients undergoing CABG, either first time or revisions, elective or emergency procedures, were included. Any hypothermia protocol was considered. Only trials reporting neurological outcomes were included.

DATA COLLECTION AND ANALYSIS

Studies were selected independently and data were extracted from the source papers independently by two reviewers. Authors were contacted for further information. Studies were combined with meta-analysis where appropriate, and meta-regression was used to explore heterogeneity.

MAIN RESULTS

There was a trend towards a reduction in the incidence of non fatal strokes in the hypothermic group (OR 0.68 (0.43, 1.05)). Conversely, there was a trend for the number of non stroke related perioperative deaths to be higher in the hypothermic group (OR 1.46 (0.9, 2.37)). Hypothermia had no effect on the incidence of non fatal myocardial infarction (OR 1.05 (0.81, 1.37)), but the incidence of another marker of myocardial damage, low output syndrome, was higher in the hypothermic group (OR 1.21 (0.99, 1.48). When pooling all "bad" outcomes (stroke, perioperative death, myocardial infarction, low output syndrome, intra aortic balloon pump use) there was no significant advantage of either hypothermia or normothermia (OR 1.07 (0.92, 1.24)). Only 4 of 17 trials reported neuropsychological function as an outcome.

REVIEWER'S CONCLUSIONS

This review could find no definite advantage of hypothermia over normothermia in the incidence of clinical events. Hypothermia was associated with a reduced stroke rate, but this is off set by a trend towards an increase in non stroke related perioperative mortality and myocardial damage. There is insufficient data to date to draw any conclusions about the use of mild hypothermia. Similarly, there is insufficient data to date to comment on the effect of temperature during CPB on subtle neurological deficits, and further trials are needed in these areas.