Effect of therapeutic hypothermia in neonates with hypoxic-ischemic encephalopathy on platelet function

Introduction of a Warming Bundle to Reduce Hypothermia in Neonatal Surgical Patients

INTRODUCTION

Hypothermia in the neonatal surgical population has been linked with significant morbidity and mortality. Our goal was to decrease intra and postoperative hypothermia.

INTERVENTION

In November 2021, a radiant warmer and hat were included along with standard warming methods prior to the start of General Surgery procedures to minimize episodes of hypothermia.

PRIMARY OUTCOME

Core body temperature was measured pre, intra and post-operatively.

METHODS

Data were prospectively collected from electronic medical records from July 2021 to March 2023. A retrospective analysis was performed. Hypothermia was defined as a temperature <36.5C. Control charts were created to analyze the effect of interventions.

RESULTS

A total of 277 procedures were identified; 226 abdominal procedures, 31 thoracic, 14 skin/soft tissue and 6 anorectal. The median post-natal age was 36.1 weeks (IQR: 33.2-39.2), with a pre-surgical weight of 2.3 kg (IQR: 1.6-3.0) and operative duration of 181 min (IQR: 125-214). Hat and warmer data were unavailable for 59 procedures, both hat and warmer were used for 51 % procedures, hat alone for 29 %, warmer alone for 10 % and neither for 10 % of procedures. Over time there was a significant increase in hat utilization while warmer usage was unchanged. There was a significant increase in the mean lowest intra-operative temperature and decrease in proportion of hypothermic patients intra-operatively and post-operatively.

CONCLUSIONS

The inclusion of a radiant warmer and hat decreased the proportion of hypothermic patients during and after surgery. Further studies are necessary to analyze the impact on surgical outcomes.

LEVEL OF EVIDENCE

III.

Hemostasis in Neonates with Perinatal Hypoxia—Laboratory Approach: A Systematic Review

Birth asphyxia, with an estimated prevalence of 1 to 6 per 1,000 live births, may lead to multiorgan dysfunction due to impaired oxygen and/or blood supply to various organ systems, including the hemostatic system. Coagulopathy, a common complication of perinatal asphyxia, has been described since the 1960s. The aim of this study was to systematically review the literature for records on the use of hemostasis tests in the evaluation of coagulation disorders, in neonates who had suffered from perinatal hypoxia or asphyxia. We identified published studies by searching PubMed and Scopus, up until April 2022. The literature search retrieved 37 articles fulfilling the inclusion criteria of the review. According to the bibliography, thrombocytopenia is commonly associated with perinatal hypoxia/asphyxia. The thrombocytopenia is usually described as mild and platelets return to normal levels by the 10th day of life. Additionally, hypoxic neonates usually present with a hypocoagulable profile, as reflected by the prolongation of standard coagulation tests, including prothrombin time, activated partial thromboplastin time, and international normalized ratio, findings commonly associated with disseminated intravascular coagulation, and by the reduction of the levels of the physiologic inhibition of coagulation system. A few studies thus far using ROTEM/TEG in hypoxic neonates have come to the same conclusion as well; hypoxic newborns seem to be characterized by a hypocoagulable profile compared with healthy neonates. It should be emphasized, however, that standard coagulation tests provide only a rough estimation of the true bleeding or thrombotic risk of hypoxic neonates. On the contrary, viscoelastic methods seem to be more precise in the early detection of hemostasis disorders in the neonatal population. However, until now, there was uncertainty as to the most appropriate coagulation assays for diagnosis and management of coagulation derangement in neonates with perinatal hypoxia indicating the need for further research on this field.

Effect of Therapeutic Hypothermia Treatment on Acute Phase Reactants

Objective In our study, we aimed to examine the effect of therapeutic hypothermia treatment on C-reactive protein (CRP) and interleukin-6 (IL-6) in infants with hypoxic ischemic encephalopathy (HIE).

Methods The data of the patients with the diagnosis of HIE we followed up in our unit between 2017 and 2018 were analyzed retrospectively. Patients who died during follow-up and patients with proven septicemia at the time of examination were excluded from the study. The routine CRP and IL-6 values ​​of the patients included in the study were compared before and after hypothermia treatment.

Results Therapeutic hypothermia treatment applied for 72 hours was found to cause a statistically significant increase in CRP after treatment when compared with the values ​​measured before treatment (0.6 (0.2–1.9) before and median (P25–75), and after treatment 7.5 (4–18) and median (P25–75) mg/L, p=0.00). While IL-6 was found to be high in the early period due to the effect of hypoxia, it was found to be low after hypothermia treatment (80.5 (40–200) median (P25–75) – 32 (18–50) median (P25–75) pg/ml, p=0.131). While the white blood cell count was high before hypothermia treatment due to hypoxia, it was found to be low after treatment (24600 (19600–30100) median (P25–75) –11300 (8800–14200) median (P25–75)/µL, p=0.001).

Conclusion White blood cells and IL-6 can be found to be high due to hypoxia without infection, and CRP can be found to be high after therapeutic hypothermia treatment without infection. The effect of hypoxia and hypothermia should be considered when evaluating acute phase reactants.

Haematological issues in neonates with neonatal encephalopathy treated with hypothermia

Neonatal encephalopathy (NE) is associated with abnormality of neurological function and involves multiorgan dysfunction. There are long-term complications such as cerebral palsy and developmental delay. Cardiac, renal, neurological and other organ dysfunctions are well described. Haematological dysfunction is relatively common and includes anaemia, thrombocytopenia, monocyte and neutrophil activation, hypofibrinogenemia and coagulopathy. There is a lack of consensus definitions of hematological parameters and optimal levels for intervention due to the lack of interventional studies in term neonates and the lack of knowledge of the optimal values during therapeutic hypothermia. However, derangements in hematological values are also associated with neurodevelopmental outcomes. This article outlines the different hematological complications associated with NE and therapeutic hypothermia and suggests a framework for management.

Complications During Therapeutic Hypothermia After Perinatal Asphyxia: A Comparison with Trial Data

Complications of therapeutic hypothermia (HT) after perinatal asphyxia of a cohort of infants were compared with complications reported in the Cochrane review. The occurrence during moderate HT of bradycardia, arrhythmia, hypotension, use of inotropes, pulmonary hypertension requiring NO inhalation, air leak syndrome, elevated liver enzymes, necrotizing enterocolitis, sepsis, oliguria, thrombocytopenia, coagulopathy, and electrolyte disturbances was assessed in 168 infants with therapeutic HT following perinatal asphyxia and compared to the incidence of complications published previously in the Cochrane review. In our cohort, mortality and adverse neurodevelopmental outcome were 31% and 6%, respectively, and not different from previously published studies. Nine out of 12 complications occurred more often in our cohort, one complication (oliguria) less often compared to previous results. The incidence of bradycardia and subcutaneous fat necrosis was not significantly different from previous reports. Complications during therapeutic HT in our cohort of infants occurred more often than reported previously. A detailed evaluation of possible complications is relevant for optimal monitoring during therapeutic HT.

Neonatal Platelet Function

Similarly to the development of the plasma coagulation system, which matures during the early weeks and months of life, age-dependent mechanisms and developmental changes influence platelet production and function in neonates. Platelet function testing on cord blood and peripheral blood demonstrates a generalized platelet hyporeactivity, during the first days of life. This reactivity reaches normal adult levels between the fifth and ninth day of life. The persistence of hyporeactivity after the tenth day of life might indeed suggest a platelet disorder.

Effect of temperature on thromboelastography and implications for clinical use in newborns undergoing therapeutic hypothermia

BACKGROUND

Encephalopathic neonates undergoing therapeutic hypothermia have increased risk for coagulopathy secondary to perinatal asphyxia and effects of cooling on the coagulation enzyme cascade. Thromboelastography (TEG) allows for a comprehensive assessment of coagulation that can be regulated for temperature. TEG has not been previously evaluated in newborns undergoing hypothermia treatment.

METHODS

Encephalopathic neonates treated with systemic hypothermia were enrolled in this prospective observational study. Daily blood specimens were collected for standard coagulation tests and platelet counts during hypothermia and after rewarming. Concurrent TEG assays were performed at 33.5 and 37.0 °C for comparison.

RESULTS

A total of 48 paired TEGs from 24 subjects were performed. Forty percent of the subjects were males, the mean (± SD) birth weight was 3.2 ± 0.7 kg, and the mean gestational age was 38.4 ± 1.4 wk. TEG results differed significantly between assays performed at 37.0 vs. 33.5 °C, indicating more impaired coagulation at 33.5 °C. TEG parameters clot kinetics, angle, maximum amplitude (MA), and coagulation index were significantly associated with clinical bleeding (P < 0.05). These remained significant (except for MA) after controlling for transfusion therapy.

CONCLUSION

TEG results are affected by temperature, consistent with the known association of hypothermia with coagulopathy. Several TEG parameters are predictive of clinical bleeding in newborns undergoing hypothermia. Selected cutpoints to predict bleeding risk are temperature dependent.

Cooling for newborns with hypoxic ischaemic encephalopathy

BACKGROUND

Newborn animal studies and pilot studies in humans suggest that mild hypothermia following peripartum hypoxia-ischaemia in newborn infants may reduce neurological sequelae without adverse effects.

OBJECTIVES

To determine the effect of therapeutic hypothermia in encephalopathic asphyxiated newborn infants on mortality, long-term neurodevelopmental disability and clinically important side effects.

SEARCH METHODS

We used the standard search strategy of the Cochrane Neonatal Review Group as outlined in The Cochrane Library (Issue 2, 2007). Randomised controlled trials evaluating therapeutic hypothermia in term and late preterm newborns with hypoxic ischaemic encephalopathy were identified by searching the Oxford Database of Perinatal Trials, the Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library, 2007, Issue 2), MEDLINE (1966 to June 2007), previous reviews including cross-references, abstracts, conferences, symposia proceedings, expert informants and journal handsearching. We updated this search in May 2012.

SELECTION CRITERIA

We included randomised controlled trials comparing the use of therapeutic hypothermia with standard care in encephalopathic term or late preterm infants with evidence of peripartum asphyxia and without recognisable major congenital anomalies. The primary outcome measure was death or long-term major neurodevelopmental disability. Other outcomes included adverse effects of cooling and 'early' indicators of neurodevelopmental outcome.

DATA COLLECTION AND ANALYSIS

Four review authors independently selected, assessed the quality of and extracted data from the included studies. Study authors were contacted for further information. Meta-analyses were performed using risk ratios (RR) and risk differences (RD) for dichotomous data, and weighted mean difference for continuous data with 95% confidence intervals (CI).

MAIN RESULTS

We included 11 randomised controlled trials in this updated review, comprising 1505 term and late preterm infants with moderate/severe encephalopathy and evidence of intrapartum asphyxia. Therapeutic hypothermia resulted in a statistically significant and clinically important reduction in the combined outcome of mortality or major neurodevelopmental disability to 18 months of age (typical RR 0.75 (95% CI 0.68 to 0.83); typical RD -0.15, 95% CI -0.20 to -0.10); number needed to treat for an additional beneficial outcome (NNTB) 7 (95% CI 5 to 10) (8 studies, 1344 infants). Cooling also resulted in statistically significant reductions in mortality (typical RR 0.75 (95% CI 0.64 to 0.88), typical RD -0.09 (95% CI -0.13 to -0.04); NNTB 11 (95% CI 8 to 25) (11 studies, 1468 infants) and in neurodevelopmental disability in survivors (typical RR 0.77 (95% CI 0.63 to 0.94), typical RD -0.13 (95% CI -0.19 to -0.07); NNTB 8 (95% CI 5 to 14) (8 studies, 917 infants). Some adverse effects of hypothermia included an increase sinus bradycardia and a significant increase in thrombocytopenia.

AUTHORS' CONCLUSIONS

There is evidence from the 11 randomised controlled trials included in this systematic review (N = 1505 infants) that therapeutic hypothermia is beneficial in term and late preterm newborns with hypoxic ischaemic encephalopathy. Cooling reduces mortality without increasing major disability in survivors. The benefits of cooling on survival and neurodevelopment outweigh the short-term adverse effects. Hypothermia should be instituted in term and late preterm infants with moderate-to-severe hypoxic ischaemic encephalopathy if identified before six hours of age. Further trials to determine the appropriate techniques of cooling, including refinement of patient selection, duration of cooling and method of providing therapeutic hypothermia, will refine our understanding of this intervention.

Delayed neurovascular dysfunction is alleviated by hydrogen in asphyxiated newborn pigs

BACKGROUND

The neurovascular unit encompasses the functional interactions of cerebrovascular and brain parenchymal cells necessary for the metabolic homeostasis of neurons. Previous studies indicated marked but only transient (1-4 h) reactive oxygen species-dependent neurovascular dysfunction in newborn pigs after severe hypoxic/ischemic (H/I) stress contributing to the neuronal injury after birth asphyxia.

OBJECTIVES

Our major purpose was to determine if neurovascular dysfunction would also occur later, at 24 h after a milder H/I stress. We also tested if the putative hydroxyl radical scavenger hydrogen (H2) exerted neurovascular protection.

METHODS

Anesthetized, ventilated piglets were assigned to three groups of 9 animals: time control, asphyxia/reventilation with air, and asphyxia/reventilation with air +2.1% H2 for 4 h. Asphyxia was induced by suspending ventilation for 8 min. Cerebrovascular reactivity (CR) of pial arterioles was determined using closed cranial window/intravital microscopy 24 h after asphyxia to the endothelium-dependent cerebrovascular stimulus hypercapnia, the neuronal function-dependent stimulus N-methyl-D-aspartate (NMDA), norepinephrine, and sodium nitroprusside. The brains were subjected to histopathology.

RESULTS

Hemodynamic parameters, blood gases, and core temperature did not differ significantly among the experimental groups. In the early reventilation period, the recovery of electroencephalographic activity was significantly better in H2-treated animals. Asphyxia/reventilation severely attenuated CR to hypercapnia and NMDA; however, reactivity to norepinephrine and sodium nitroprusside were unaltered. H2 fully or partially preserved CR to hypercapnia or NMDA, respectively. Histopathology revealed modest neuroprotection afforded by H2.

CONCLUSIONS

Severe stimulus-selective delayed neurovascular dysfunction develops and persists even after mild H/I stress. H2 alleviates this delayed neurovascular dysfunction that can contribute to its neuroprotective effect.

Cardiac biomarkers as indicators of hemodynamic adaptation during postasphyxial hypothermia treatment

BACKGROUND

Little is known about the effects of hypothermia on the cardiovascular system in term newborns with neonatal encephalopathy.

OBJECTIVES

To evaluate whether mild hypothermia for neonatal encephalopathy is cardioprotective as indicated by the cardiac biomarkers cardiac troponin I (cTnI) and B-type natriuretic peptide (BNP).

METHODS

This was an observational cohort study of infants treated for perinatal asphyxia. In infants, mild total body hypothermia treatment of 33.5°C during 72 h was initiated (n = 20). Samples of cTnI and BNP were collected before the start of hypothermia, at 24 and 48 h after birth, and after rewarming (84 h). BNP and cTnI values were then compared with BNP and cTnI values of asphyxiated infants not treated with hypothermia (n = 28).

RESULTS

No differences were found between the groups in clinical patient characteristics or inotropic support. The hypothermia-treated patients seemed to be clinically more affected (5-min Apgar score, p < 0.05; umbilical artery pH, p = 0.08), but showed similar encephalopathy scores. Significantly lower values for BNP were found in hypothermia- compared to nonhypothermia-treated infants at 48 h and at normothermia after rewarming [144 pmol/l (95-286) vs. 75 pmol/l (45-143), 182 pmol/l (73-341) vs. 43 pmol/l (24-163)]. No differences were found for cTnI concentrations between both groups.

CONCLUSIONS

The raised, but similar, cTnI values between hypothermia- and nonhypothermia-treated infants indicate similar myocardial damage in both groups. The lower BNP levels during hypothermia treatment suggest that hypothermia after perinatal asphyxia exerts a beneficial effect on cardiac function.

Cooling for newborns with hypoxic ischaemic encephalopathy

BACKGROUND

Newborn animal and human pilot studies suggest that mild hypothermia following peripartum hypoxia-ischaemia in newborn infants may reduce neurological sequelae, without adverse effects.

OBJECTIVES

To determine whether therapeutic hypothermia in encephalopathic asphyxiated newborn infants reduces mortality and long-term neurodevelopmental disability, without clinically important side effects.

SEARCH STRATEGY

The standard search strategy of the Neonatal Review Group as outlined in the Cochrane Library (Issue 2, 2003) was used. Randomised controlled trials evaluating therapeutic hypothermia in term newborns with hypoxic ischaemic encephalopathy were identified by searching the Oxford Database of Perinatal Trials, the Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library Issue Issue 2, 2003), MEDLINE (1966 to July 2003), previous reviews including cross-references, abstracts, conferences, symposia proceedings, expert informants and journal hand searching.

SELECTION CRITERIA

Randomised controlled trials comparing the use of therapeutic hypothermia with normothermia in encephalopathic newborn infants with evidence of peripartum asphyxia and without recognisable major congenital anomalies were included. The primary outcome measure was death or long-term major neurodevelopmental disability. Other outcomes included adverse effects of cooling and 'early' indicators of neurodevelopmental outcome.

DATA COLLECTION AND ANALYSIS

Three reviewers independently selected, assessed the quality of and extracted data from the included studies. Authors were contacted for further information. Meta-analyses were performed using relative risk and risk difference for dichotomous data, and weighted mean difference for continuous data with 95% confidence intervals.

MAIN RESULTS

Two randomised controlled trials were included in this review, comprising 50 term infants with moderate/ severe encephalopathy and evidence of intrapartum asphyxia. There was no significant effect of therapeutic hypothermia on the combined outcome of death or major neurodevelopmental disability in survivors followed. No adverse effects of hypothermia on short term medical outcomes or on some 'early' indicators of neurodevelopmental outcome were detected.

REVIEWER'S CONCLUSIONS

Although two small randomised controlled trials demonstrated neither evidence of benefit or harm, current evidence is inadequate to assess either safety or efficacy of therapeutic hypothermia in newborn infants with hypoxic ischaemic encephalopathy. Therapeutic hypothermia for encephalopathic asphyxiated newborn infants should be further evaluated in well designed randomised controlled trials.