Impact of Graded Hypothermia on Coagulation and Fibrinolysis

Effectiveness of Mild to Moderate Hypothermic Cardiopulmonary Bypass on Early Clinical Outcomes

BACKGROUND

Intraoperative hypothermia is an integral part of cardiopulmonary bypass (CPB), and a precise degree of hypothermia may improve the early clinical outcomes of cardiac surgery. Presently, there is no agreement on an accurate, advantageous temperature range for routine use in CPB. To address this issue, we conducted a retrospective observational study to compare the effects of different hypothermic temperature ranges on primary (inotropic support, blood loss, and platelet count) and secondary (ventilation support and in-hospital stay) outcomes in patients undergoing elective cardiac surgery.

METHODS

Data were retrieved from the medical database of the Cardiovascular Surgery Department, King Edward Medical University, Lahore-Pakistan (a tertiary care hospital), dating from February 2015 to December 2017. Patients were divided into mild (34 °C to 36 °C), intermediate (31 °C to 33 °C), or moderate (28 °C to 30 °C) hypothermic groups.

RESULTS

Out of 275 patients, 245 (89.09%) fit the inclusion criteria. The cohort with mild hypothermic CPB temperatures presented better clinical outcomes in terms of requiring less inotropic support, less blood loss, fewer blood transfusions, improved platelet counts, shorter in-hospital stays, and required less ventilation support, when compared with other hypothermic groups.

CONCLUSIONS

Mild hypothermic CPB (34 °C to 36 °C) may produce better clinical outcomes for cardiac surgery and improve the quality of health of cardiac patients.

Hemostatic shape memory polymer foams with improved survival in a lethal traumatic hemorrhage model

Although there are many hemostatic agents available for use on the battlefield, uncontrolled hemorrhage is still the primary cause of preventable death. Current hemostatic dressings include QuikClot® Combat Gauze (QCCG) and XStat®, which have inadequate success in reducing mortality. To address this need, a new hemostatic material was developed using shape memory polymer (SMP) foams, which demonstrate biocompatibility, rapid clotting, and shape recovery to fill the wound site. SMP foam hemostatic efficacy was examined in a lethal, noncompressible porcine liver injury model over 6 h following injury. Wounds were packed with SMP foams, XStat, or QCCG and compared in terms of time to bleeding cessation, total blood loss, and animal survival. The hemostatic material properties and in vitro blood interactions were also characterized. SMP foams decreased blood loss and active bleeding time in comparison with XStat and QCCG. Most importantly, SMP foams increased the 6 h survival rate by 50% and 37% (vs. XStat and QCCG, respectively) with significant increases in survival times. Based upon in vitro characterizations, this result is attributed to the low stiffness and shape filling capabilities of SMP foams. This study demonstrates that SMP foams have promise for improving upon current clinically available hemostatic dressings and that hemostatic material properties are important to consider in designing devices for noncompressible bleeding control. STATEMENT OF SIGNIFICANCE: Uncontrolled hemorrhage is the leading cause of preventable death on the battlefield, and it accounts for approximately 1.5 million deaths each year. New biomaterials are required for improved hemorrhage control, particularly in noncompressible wounds in the torso. Here, we compared shape memory polymer (SMP) foams with two clinical dressings, QuikClot Combat Gauze and XStat, in a pig model of lethal liver injury. SMP foam treatment reduced bleeding times and blood loss and significantly improved animal survival. After further material characterization, we determined that the improved outcomes with SMP foams are likely due to their low stiffness and controlled shape change after implantation, which enabled their delivery to the liver injuries without inducing further wound tearing. Overall, SMP foams provide a promising option for hemorrhage control.

Acute Kidney Injury After Neonatal Aortic Arch Surgery: Deep Hypothermic Circulatory Arrest Versus Moderate Hypothermia With Distal Aortic Perfusion

BACKGROUND

Acute kidney injury (AKI) is a common complication observed after neonatal aortic arch repair. We studied its incidence after procedures carried out using deep hypothermic circulatory arrest (DHCA) versus moderate hypothermia with distal aortic perfusion (MHDP), usually through the common femoral artery. In both groups, continuous regional cerebral perfusion (RCP) was used during the time required for aortic arch repair.

METHODS

A total of 125 neonates underwent aortic arch repair. Between 2007 and 2012, DHCA with RCP was used in 51 neonates. From 2013 to 2019, MHDP with RCP was performed on 74 newborns. Operative complexity was similar in both periods. Acute kidney injury was defined as a significant elevation of serum creatinine and was classified according to the neonatal modified n-KDIGO (neonatal Kidney Disease: Improving Global Outcomes) stages 1 to 3 (Kidney Disease Improving: Global Outcomes).

RESULTS

Acute kidney injury was observed in a total of 68 patients (68/125: 54.4%). In the majority (44/68: 64.7%), n-KDIGO stage 1 occurred. Stage 2 (n = 14) and stage 3 (n = 10) were observed more frequently after DHCA versus MHDP: 29.4% (15/51) versus 12.2% (9/74), P = .02. At cardiopulmonary bypass end, lactate levels were significantly higher (P = .001) after DHCA: 3.4 (2.9-4.3) mmol/L compared to 2.7 (2.3-3.7) mmol/L after MHDP. Early mortality was 12% (15/125) in the entire cohort. It was 17.6% (9/51) after DHCA versus 8.1% (6/74) after MHDP, however not statistically significant (P = .16).

CONCLUSION

Mild (stage 1) AKI occurred frequently after neonatal aortic arch repair. The use of MHDP was associated with a significantly lower incidence of moderate (stage 2) and severe (stage 3) AKI forms.

Moderate Hypothermia Modifies Coronary Hemodynamics and Endothelium-Dependent Vasodilation in a Porcine Model of Temperature Management

Background Hypothermia has been associated with therapeutic benefits including reduced mortality and better neurologic outcomes in survivors of cardiac arrest. However, undesirable side effects have been reported in patients undergoing coronary interventions. Using a large animal model of temperature management, we aimed to describe how temperature interferes with the coronary vasculature. Methods and Results Coronary hemodynamics and endothelial function were studied in 12 pigs at various core temperatures. Left circumflex coronary artery was challenged with intracoronary nitroglycerin, bradykinin, and adenosine at normothermia (38°C) and mild hypothermia (34°C), followed by either rewarming (38°C; n=6) or moderate hypothermia (MoHT; 32°C, n=6). Invasive coronary hemodynamics by Doppler wire revealed a slower coronary blood velocity at 32°C in the MoHT protocol (normothermia 20.2±11.2 cm/s versus mild hypothermia 18.7±4.3 cm/s versus MoHT 11.3±5.3 cm/s, P=0.007). MoHT time point was also associated with high values of hyperemic microvascular resistance (>3 mm Hg/cm per second) (normothermia 2.0±0.6 mm Hg/cm per second versus mild hypothermia 2.0±0.8 mm Hg/cm per second versus MoHT 3.4±1.6 mm Hg/cm per second, P=0.273). Assessment of coronary vasodilation by quantitative coronary analysis showed increased endothelium-dependent (bradykinin) vasodilation at 32°C when compared with normothermia (normothermia 6.96% change versus mild hypothermia 9.01% change versus MoHT 25.42% change, P=0.044). Results from coronary reactivity in vitro were in agreement with angiography data and established that endothelium-dependent relaxation in MoHT completely relies on NO production. Conclusions In this porcine model of temperature management, 34°C hypothermia and rewarming (38°C) did not affect coronary hemodynamics or endothelial function. However, 32°C hypothermia altered coronary vasculature physiology by slowing coronary blood flow, increasing microvascular resistance, and exacerbating endothelium-dependent vasodilatory response.

The health economic benefits of perioperative patient warming for prevention of blood loss and transfusion requirements as a consequence of inadvertent perioperative hypothermia

Active warming of patients is recommended by The National Institute for Health and Care Excellence (NICE) to prevent inadvertent perioperative hypothermia (IPH). This paper examines the cost effectiveness of one consequence of IPH, an increase in blood loss and the resulting transfusion risk. We quantified the risk and modelled two patient pathways, one with and one without warming, across two different surgery types. We were able to demonstrate the cost effectiveness of active warming based on one consequence even allowing for uncertainties in the model.

Efficacy of forced-air warming for preventing perioperative hypothermia and related complications in patients undergoing laparoscopic surgery: A randomized controlled trial

BACKGROUND

Perioperatively, unexpected hypothermia may cause adverse surgical outcomes. However, few studies have explored the efficacy of forced-air warming in patients undergoing laparoscopic surgery.

AIM/OBJECTIVE

To determine the efficacy of forced-air warming for preventing perioperative hypothermia and complications in patients undergoing laparoscopic surgery.

METHODS

A total of 127 participants undergoing laparoscopic thoracic or abdominal surgery were recruited between January and November 2015. Participants were randomly allocated to intervention (forced-air warming, n = 64) and control groups (passive insulation, n = 63). Oesophageal core temperature was measured during surgery, whilst tympanic core temperature was measured every 30 minutes preoperatively and in the postanaesthesia care unit. Levels of shivering and pain, amount of bleeding, and adverse cardiac events were measured before the transfer from the postanaesthesia care unit. The generalized estimating equation was used for data analysis.

RESULTS

The intervention group had better warming efficacy than the control group between 90 and 330 minutes during surgery. The intervention group had fewer complications than the control group in terms of intraoperative bleeding, time to rewarm to 36°C, pain levels, and shivering levels in the postanaesthesia care unit.

CONCLUSION

Forced-air warming can increase warming efficacy and reduce complications of perioperative hypothermia in patients undergoing laparoscopic surgery.

Hypothermia, pH, and Postoperative Red Blood Cell Transfusion in Massively Transfused Adult Cardiac Surgery Patients: A Retrospective Cohort Study

OBJECTIVE

To determine the relationships between hypothermia and pH at surgery end and postoperative red blood cell (RBC) transfusion in massively transfused adult cardiac surgery patients.

DESIGN

Retrospective cohort study.

SETTING

Single tertiary care, academic medical center.

PARTICIPANTS

A total of 395 adult patients having cardiac surgery with cardiopulmonary bypass who were massively transfused during an 8-year period. Patients were excluded if they did not receive an antifibrinolytic drug during surgery.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Body temperature and pH at surgery end were recorded. Postoperative RBC transfusion, a surrogate for postoperative bleeding, was the study's primary outcome. Secondary outcomes were postoperative fresh frozen plasma (FFP) transfusion, postoperative platelet transfusion, reoperation for bleeding, and mortality. Patients with hypothermia did not have more postoperative RBC transfusion (p = 0.56), but patients with acidosis or alkalosis received more RBCs after surgery (p = 0.04). There were no differences in secondary outcomes between groups. In multivariate analysis, both acidosis and alkalosis were independently associated with postoperative RBC transfusion (p = 0.01 and p < 0.0001).

CONCLUSION

Hypothermia at surgery end has no association with postoperative RBC transfusion in massively transfused cardiac surgery patients, but pH derangements are associated with increased postoperative transfusion. Thus, normalization of blood pH may be important in reducing postoperative bleeding in massively transfused cardiac surgery patients.

Plasma Glycoproteomic Study of Therapeutic Hypothermia Reveals Novel Markers Predicting Neurologic Outcome Post-cardiac Arrest

Therapeutic hypothermia (TH) is a neuroprotective treatment post-cardiac arrest but is grossly underutilized. After TH induction, traditional biomarkers and parameters can no long predict clinical outcome due to a lack of understanding of hypothermic response. Innovative approaches to better understand the clinical effect of TH will help to prognosticate outcome and expand beneficial population. Protein glycosylation is an important extracellular post-translational modification, regulating various extracellular signaling pathways. Here, we used glycoproteomics to investigate the association of plasma glycoproteins with the prognosis of TH-treated cardiac arrest patients. Using lectin affinity chromatography and mass spectrometry, we identified 640 glycoproteins in the plasma of cardiac arrest patients undergoing TH treatment, of which 23 were up-regulated and 14 were down-regulated in good outcome patients as compared with poor outcome ones. Notably, two glycoproteins with antioxidant activity, ceruloplasmin (CP) and haptoglobin (HP), were found to be associated with favorable neurologic outcome. This was further supported by ELISA assay in a large patients cohort, in which glycosylated CP and HP enriched by concanavilin A (ConA) and wheat germ agglutinin (WGA) lectins were significantly increased in patients developing good outcome (ConA-CP: p = 0.033; ConA-HP: p = 0.04; WGA-HP: p = 0.021). Furthermore, ROC analysis demonstrated the predictive potential of ConA-CP, ConA-HP, and WGA-HP (ConA-CP: AUC = 0.732, p = 0.031; ConA-HP: AUC = 0.746, p = 0.022; WGA-HP: AUC = 0.714, p = 0.046) and combination of them improved the predictive power (AUC = 0.830, p = 0.002). Our results suggested that glycosylated CP and HP as well as other glycoproteins may play critical roles in neuroprotection and serve as sensitive prognostic markers for TH treatments.

Risk factors for inadvertent hypothermia during adult living-donor liver transplantation

BACKGROUND

Hypothermia (core temperature <35°C) causes multiple physiologic disturbances, including coagulopathy and cardiac dysfunction. Patients undergoing liver transplantation are at risk of inadvertent hypothermia and might be more vulnerable to its adverse effects. We sought to identify the factors contributing to hypothermia during living-donor liver transplantation (LDLT), which have not yet been studied in depth.

METHODS

Medical records of 134 recipients who underwent adult-to-adult LDLT were reviewed. Core temperature at the following time points were taken: anesthetic induction, skin incision, start and end of the anhepatic phase, and hourly after hepatic reperfusion.

RESULTS

Of 134 recipients, 29 (21.6%) developed hypothermia during surgery. Four independent risk factors for hypothermia were identified: small body weight-to-body surface area ratio, acute hepatic failure, high Model for End-Stage Liver Disease (MELD) score, and low graft-to-recipient weight ratio. The amount of core temperature drop was positively correlated with the number of involved risk factors. Each risk factor had a respective contribution according to the operative phases: body weight-to-body surface area ratio and the MELD score for the preanhepatic phase, acute deterioration of hepatic failure for the anhepatic phase, and graft-to-recipient weight ratio was for the postreperfusion phase.

CONCLUSIONS

Hypothermia was independently associated with the recipient's morphometric characteristics, emergency of end-stage liver disease, MELD score, and graft volume. These factors showed a cumulative effect, and the role of each factor was different according to the operative phase. These results should aid in the development of an optimal thermal strategy during LDLT.

Continuous or discontinuous tranexamic acid effectively inhibits fibrinolysis in children undergoing cardiac surgery with cardiopulmonary bypass

Tranexamic acid is given continuously or discontinuously as an anti-fibrinolytic therapy during cardiac surgery, but the effects on fibrinolysis parameters remain poorly investigated. We sought to assess the effects of continuous and discontinuous tranexamic acid on fibrinolysis parameters in children undergoing cardiac surgery with cardiopulmonary bypass (CPB). Children requiring cardiac surgery or repeat surgery by sternotomy with CPB for congenital heart disease were randomized to receive either continuous or discontinuous tranexamic acid. Blood tranexamic acid, D-dimers, tissue plasminogen activator (tPA), tPA-plasminogen activator inhibitor 1 (tPA-PAI1) complexes, fibrinogen and fibrin monomers were measured and compared to values obtained from children who did not receive tranexamic acid. Tranexamic acid inhibited the CPB-induced increase in D-dimers, with a similar potency between continuous and discontinuous regimens. Time courses for tPA, fibrin monomers, and fibrinogen were also similar for both regimen, and there was a significant difference in tPA-PAI1 complex concentrations at the end of surgery, which may be related to a significantly higher tranexamic acid concentration. Continuous and discontinuous regimen are suitable for an effective inhibition of fibrinolysis in children undergoing cardiac surgery with CPB, but the continuous regimen was previously shown to be more effective to maintain stable tranexamic acid concentrations.

Permissive hypotension in bleeding trauma patients: helpful or not and when?

Severity of hemorrhage and rate of bleeding are fundamental factors in the outcomes of trauma. Intravenous administration of fluid is the basic treatment to maintain blood pressure until bleeding is controlled. The main guideline, used almost worldwide, Advanced Trauma Life Support, established by the American College of Surgeons in 1976, calls for aggressive administration of intravenous fluids, primarily crystalloid solutions. Several other guidelines, such as Prehospital Trauma Life Support, Trauma Evaluation and Management, and Advanced Trauma Operative Management, are applied according to a patient's current condition. However, the ideal strategy remains unclear. With permissive hypotension, also known as hypotensive resuscitation, fluid administration is less aggressive. The available models of permissive hypotension are based on hypotheses in hypovolemic physiology and restricted clinical trials in animals. Before these models can be used in patients, randomized, controlled clinical trials are necessary.

Comparison of two fluid warming devices for maintaining body core temperature during living donor liver transplantation: Level 1 H-1000 vs. Fluid Management System 2000

BACKGROUND

Rapid fluid warming has been a cardinal measure to maintain normothermia during fluid resuscitation of hypovolemic patients. A previous laboratory simulation study with different fluid infusion rates showed that a fluid warmer using magnetic induction is superior to a warmer using countercurrent heat exchange. We tested whether the simulation-based result is translated into the clinical liver transplantation.

METHODS

Two hundred twenty recipients who underwent living donor liver transplantation between April 2009 and October 2011 were initially screened. Seventeen recipients given a magnetic induction warmer (FMS2000) were matched 1 : 1 with those given a countercurrent heat exchange warmer (Level-1 H-1000) based on propensity score. Matched variables included age, gender, body mass index, model for end-stage liver disease score, graft size and time under anesthesia. Core temperatures were taken at predetermined time points.

RESULTS

Level-1 and FMS groups had comparable core temperature throughout the surgery from skin incision, the beginning/end of the anhepatic phase to skin closure. (P = 0.165, repeated measures ANOVA). The degree of core temperature changes within the dissection, anhepatic and postreperfusion phase were also comparable between the two groups. The minimum intraoperative core temperature was also comparable (Level 1, 35.6℃ vs. FMS, 35.4℃, P = 0.122).

CONCLUSIONS

A countercurrent heat exchange warmer and magnetic induction warmer displayed comparable function regarding the maintenance of core temperature and prevention of hypothermia during living donor liver transplantation. The applicability of the two devices in liver transplantation needs to be evaluated in various populations and clinical settings.

The pathophysiological mechanisms of the onset of death through accidental hypothermia and the presentation of "The little match girl" case

Hypothermia and death caused by hypothermia may be found in a number of fiction works, mainly in novels. In the well-known story “The Little Match Girl” by Hans Christian Andersen, one can notice that the descriptions of the phenomena occurring before the girl’s death are in fact a literary presentation of the pathophysiological mechanisms of the onset of death through accidental hypothermia. This essay presents the medical aspects of the story written by Andersen.

Effect of mild hypothermia on the coagulation-fibrinolysis system and physiological anticoagulants after cardiopulmonary resuscitation in a porcine model

The aim of this study was to evaluate the effect of mild hypothermia on the coagulation-fibrinolysis system and physiological anticoagulants after cardiopulmonary resuscitation (CPR). A total of 20 male Wuzhishan miniature pigs underwent 8 min of untreated ventricular fibrillation and CPR. Of these, 16 were successfully resuscitated and were randomized into the mild hypothermia group (MH, n = 8) or the control normothermia group (CN, n = 8). Mild hypothermia (33°C) was induced intravascularly, and this temperature was maintained for 12 h before pigs were actively rewarmed. The CN group received normothermic post-cardiac arrest (CA) care for 72 h. Four animals were in the sham operation group (SO). Blood samples were taken at baseline, and 0.5, 6, 12, 24, and 72 h after ROSC. Whole-body mild hypothermia impaired blood coagulation during cooling, but attenuated blood coagulation impairment at 72 h after ROSC. Mild hypothermia also increased serum levels of physiological anticoagulants, such as PRO C and AT-III during cooling and after rewarming, decreased EPCR and TFPI levels during cooling but not after rewarming, and inhibited fibrinolysis and platelet activation during cooling and after rewarming. Finally, mild hypothermia did not affect coagulation-fibrinolysis, physiological anticoagulants, or platelet activation during rewarming. Thus, our findings indicate that mild hypothermia exerted an anticoagulant effect during cooling, which may have inhibitory effects on microthrombus formation. Furthermore, mild hypothermia inhibited fibrinolysis and platelet activation during cooling and attenuated blood coagulation impairment after rewarming. Slow rewarming had no obvious adverse effects on blood coagulation.

Therapeutic hypothermia for brain ischemia: where have we come and where do we go?

Mild hypothermia is an established neuroprotectant in the laboratory, showing remarkable and consistent effects across multiple laboratories and models of brain injury. At the clinical level, mild hypothermia has shown benefits in patients who have experienced cardiac arrest and in some pediatric populations experiencing hypoxic brain insults. Its role, however, in stroke therapy has yet to be established. Translating preclinical data to the clinical arena presents unique challenges with regard to cooling in patients who are generally awake and may require additional therapies, such as reperfusion. We review the state of therapeutic hypothermia in ischemic and hemorrhagic stroke and provide an outlook for its role in stroke therapy.