Heart rate response to therapeutic hypothermia in infants with hypoxic-ischaemic encephalopathy

Head cooling wrap could suppress the elevation of core temperature after cardiac surgery during forced-air warming in a pediatric intensive care unit: a randomized clinical trial

PURPOSE

The main aim of the current trial was to explore our hypothesis that cooling head wraps lower the core temperature more effectively than ice packs on the head during forced-air warming after pediatric cardiac surgeries.

METHODS

This study was a single-center Randomized Controlled Trial. Participants were children with a weight ≤ 10 kg and hyperthermia during forced-air warming after cardiac surgeries. When the core temperature reached 37.5 °C, ice packs on the head (group C) or a cooling head wrap (group H) were used as cooling devices to decrease the core temperature. The primary outcome was the core temperature. The secondary outcomes were the foot surface temperature and heart rate. We measured all outcomes every 30 min for 240 min after the patient developed hyperthermia. We conducted two-way ANOVA as a pre-planned analysis and also the Bonferroni test as a post hoc analysis.

RESULTS

Twenty patients were randomly assigned to groups C and H. The series of core temperatures in group H were significantly lower than those in group C (p < 0.0001), and post hoc analysis showed that there was no significant difference in core temperatures at T0 between the two groups and statistically significant differences in all core temperatures at T30-240 between the two groups. There was no difference between the two groups' surface temperatures and heart rates.

CONCLUSIONS

Compared to ice packs on the head, head cooling wraps more effectively suppress core temperature elevation during forced-air warming after pediatric cardiac surgery.

Time series analysis of non-invasive hemodynamic monitoring data in neonates with hypoxic-ischemic encephalopathy

Background and aims

Hemodynamic instability is common in neonates with hypoxic-ischemic encephalopathy (HIE) undergoing therapeutic hypothermia (TH). Rewarming is a critical period and non-invasive circulatory monitoring may help guide cardiovascular supportive therapy. The aim of the study was to provide a comprehensive analysis of cardiac function parameters during TH and its relation to neurodevelopmental outcome.

Methods

In a prospective, observational study, 26 neonates with moderate-severe HIE were enrolled, born between 2016 and 2019. A hemodynamic monitor based on electrical velocimetry (ICON, Osypka Medical GmbH, Berlin, Germany) was used. Heart rate (HR), stroke volume (SV), cardiac output (CO) data were recorded continuously throughout TH and rewarming. Neurological outcome was assessed at 2 years of age using the Bayley Scales of Infant Development II. edition. Favorable outcome was defined as >70 points on both the psychomotor and mental scales. Time-series analysis was used and features of cardiac function were described to perform logistic regression modeling for outcome prediction.

Results

Fourteen (54%) patients had favorable and 12 (46%) had adverse outcome. Data collection started from median [IQR] of 11.8 [7.0; 24.3] hours (h) of life and lasted until 84.0. [81.8; 87.0] h. During TH, the mean HR of the favorable outcome group was significantly lower than that of the adverse outcome group (86 ± 13/min vs. 104 ± 18/min, p = 0.01). During rewarming HR increased similarly in both groups. SV was unaffected by rewarming, and showed a slowly increasing trend. SV of the favorable outcome group was significantly higher compared to the adverse outcome group (1.55 ± 0.23 ml/kg vs. 1.29 ± 0.30 ml/kg, p = 0.035). In line with this, CO was similar in both groups (136 ± 27 ml/kg/min vs. 134 ± 36 ml/kg/min), and a significant 25% increase in CO was observed during rewarming. Based on multiple regression modeling, HR during TH was independently associated with neurological outcome (p = 0.023).

Conclusion

Based on continuous hemodynamic monitoring, patients with adverse outcome have lower SV and higher HR to achieve similar CO to patients with favorable outcome during TH. HR during hypothermia is independently associated with the neurodevelopmental outcome.

Body temperature, heart rate and long-term outcome of cooled infants: an observational study

BACKGROUND

Therapeutic hypothermia is a standard of care for neonatal encephalopathy; however, approximately one in two newborn infants fails to respond to this treatment. Recent studies have suggested potential relationships between body temperature, heart rate and the outcome of cooled infants.

METHODS

The clinical data of 756 infants registered to the Baby Cooling Registry of Japan between January 2012 and December 2016 were analysed to assess the relationship between body temperature, heart rate and adverse outcomes (death or severe impairment at 18 months corrected age).

RESULTS

A lower body temperature at admission was associated with adverse outcomes in the univariate analysis (P < 0.001), the significance of which was lost when adjusted for the severity of encephalopathy and other covariates. A higher body temperature during cooling and higher heart rate before and during cooling were associated with adverse outcomes in both univariate (all P < 0.001) and multivariate (P = 0.012, P < 0.001 and P < 0.001, respectively) analyses.

CONCLUSIONS

Severe hypoxia-ischaemia might be a common causative of faster heart rates before and during cooling and low body temperature before cooling, whereas causal relationships between slightly higher temperatures during cooling and adverse outcomes need to be elucidated in future studies.

IMPACT

In a large cohort of encephalopathic newborn infants, dual roles of body temperature to the outcome were shown; adverse outcomes were associated with a lower body temperature at admission and higher body temperature during cooling. A higher heart rate before and during cooling were associated with adverse outcomes. Severe hypoxia-ischaemia might be a common causative of faster heart rates before and during cooling and low body temperature before cooling. The exact mechanism underlying the relationship between slightly higher body temperature during cooling and adverse outcomes remains unknown, which needs to be elucidated in future studies.

Hypothermia and Cardiovascular Instability

Severely asphyxiated neonates have acute heart failure as part of their multiorgan dysfunction syndrome during the first days of life. Supporting the cardiovascular system during this phase is part of contemporary treatment and regarded as vital for limiting the neurodevelopmental injury. The decision to treat cardiovascular instability should be based on evaluation of end-organ function. Neonatologist-performed echocardiography in combination with other diagnostic modalities enables comprehensive real-time assessment. This review discusses associations between hemodynamics and adverse outcome, modalities for evaluating the hemodynamic state of the infant, and therapeutic approaches during intensive care.

System Specific Effects of Therapeutic Hypothermia with Neonatal Encephalopathy: Pearls for Clinicians

Neonatal encephalopathy (NE) is defined as a condition of impaired neurological function often caused by a peripartum event that impairs gas exchange resulting in hypoxia, hypercapnia, cerebral ischemia, and metabolic acidosis. NE is a significant cause of neonatal morbidity and mortality. Therapeutic hypothermia (TH) is the standard of care for the treatment of moderate and severe NE and has significantly improved long-term outcomes for affected infants. There are extensive systemic physiologic effects associated with TH that clinicians need to be aware of to optimize care for these infants. There is a paucity of literature that comprehensively identifies causal relationships between the physiologic and biochemical effects of TH. This can leave neonatal clinicians devoid of a comprehensive understanding of the medical management of NE. Therefore, this article seeks to help fill this gap, improve clinician knowledge base, and ultimately improve the care of infants undergoing TH.

Combination therapy with erythropoietin, magnesium sulfate and hypothermia for hypoxic-ischemic encephalopathy: an open-label pilot study to assess the safety and feasibility

BACKGROUND

Although therapeutic hypothermia improves the outcome of neonatal hypoxic-ischemic encephalopathy (HIE), its efficacy is still limited. This preliminary study evaluates the safety and feasibility of the combination therapy with erythropoietin (Epo), magnesium sulfate and hypothermia in neonates with HIE.

METHODS

A combination therapy with Epo (300 U/kg every other day for 2 weeks), magnesium sulfate (250 mg/kg for 3 days) and hypothermia was started within 6 h of birth in neonates who met the institutional criteria for hypothermia therapy. All patients received continuous infusion of dopamine. Vital signs and adverse events were recorded during the therapy. Short-term and long-term developmental outcomes were also evaluated.

RESULTS

Nine patients were included in the study. The mean age at first intervention was 3.9 h (SD, 0.5). Death, serious adverse events or changes in vital signs likely due to intervention were not observed during hospital care. All nine patients completed the therapy. At the time of hospital discharge, eight patients had established oral feeding and did not require ventilation support. Two patients had abnormal MRI findings. At 18 months of age, eight patients received a follow-up evaluation, and three of them showed signs of severe neurodevelopmental disability.

CONCLUSION

The combination therapy with 300 U/kg Epo every other day for 2 weeks, 250 mg/kg magnesium sulphate for 3 days and therapeutic hypothermia is feasible in newborn patients with HIE.

TRIAL REGISTRATION

ISRCTN33604417 retrospectively registered on 14 September 2018.

Body Temperature, Heart Rate, and Short-Term Outcome of Cooled Infants

Therapeutic hypothermia following neonatal encephalopathy is neuroprotective. However, approximately one in two cooled infants still die or develop permanent neurological impairments. Further understanding of variables associated with the effectiveness of cooling is important to improve the therapeutic regimen. To identify clinical factors associated with short-term outcomes of cooled infants, clinical data of 509 cooled infants registered to the Baby Cooling Registry of Japan between 2012 and 2014 were evaluated. Independent variables of death during the initial hospitalization and survival discharge from the cooling hospital at ≤28 days of life were assessed. Death was associated with higher Thompson scores at admission (p < 0.001); higher heart rates after 3-72 hours of cooling (p < 0.001); and higher body temperature after 24 hours of cooling (p = 0.002). Survival discharge was associated with higher 10 minutes Apgar scores (p < 0.001); higher blood pH and base excess (both p < 0.001); lower Thompson scores (at admission and after 24 hours of cooling; both p < 0.001); lower heart rates at initiating cooling (p = 0.003) and after 24 hours of cooling (p < 0.001) and lower average values after 3-72 hours of cooling (p < 0.001); higher body temperature at admission (p < 0.001); and lower body temperature after 24 hours and lower mean values after 3-72 hours of cooling (both p < 0.001). Survival discharge was best explained by higher blood pH (p < 0.05), higher body temperature at admission (p < 0.01), and lower body temperature and heart rate after 24 hours of cooling (p < 0.01 and <0.001, respectively). Lower heart rate, higher body temperature at admission, and lower body temperature during cooling were associated with favorable short-term outcomes.

Electrocardiographic and echocardiographic changes during therapeutic hypothermia in encephalopathic infants with long-term adverse outcome

AIM

To assess the electrocardiography and echocardiography changes during therapeutic hypothermia and rewarming period in encephalopathic infants with long-term adverse neurological outcome.

METHODS

Prospective multicentre longitudinal study. We included 64 consecutive infants with moderate or severe hypoxic ischaemic encephalopathy undergoing therapeutic hypothermia who had 18-24 month-outcome data. We analysed electrocardiography and heart rate changes before, during and after therapeutic hypothermia. Superior vena cava flow, left ventricular cardiac output and stroke volume were studied using echocardiography during and immediately after therapeutic hypothermia. An abnormal outcome was defined as death or moderate/severe disability at 18-24 months.

RESULTS

Neonates with higher superior vena cava flow pre-rewarming had significantly higher odds of documented long-term adverse outcome when compared to newborns with good outcome (OR 1.57; 95%CI, 1.1-1.78; p = 0.01 after adjustment). QTc and RR intervals were significantly longer at 12, 24, 36 and 48 h in infants with good outcome compared with those with adverse outcome (p < 0.001). During therapeutic hypothermia, infants with poor outcome had a higher heart rate at 12, 24, 36, 48, 60 h after birth compared with those with good outcome (p < 0.001). From 36 h on, heart rate gradually increased and RR and QTc intervals progressively shortened with values back to normal after rewarming.

CONCLUSIONS

Infants with hypoxic ischaemic encephalopathy who have adverse neurological outcome show a preferential cerebral blood flow redistribution during therapeutic hypothermia. Infants with poor outcome have higher heart rate and shorter RR and QTc intervals during therapeutic hypothermia.

Hypothermia for encephalopathy in low-income and middle-income countries: feasibility of whole-body cooling using a low-cost servo-controlled device

Although therapeutic hypothermia (TH) is the standard of care for hypoxic ischaemic encephalopathy in high-income countries, the safety and efficacy of this therapy in low-income and middle-income countries (LMICs) is unknown. We aimed to describe the feasibility of TH using a low-cost servo-controlled cooling device and the short-term outcomes of the cooled babies in LMIC.

DESIGN

We recruited babies with moderate or severe hypoxic ischaemic encephalopathy (aged <6 hours) admitted to public sector tertiary neonatal units in India over a 28-month period. We administered whole-body cooling (set core temperature 33.5°C) using a servo-controlled device for 72 hours, followed by passive rewarming. We collected the data on short-term neonatal outcomes prior to hospital discharge.

RESULTS

Eighty-two babies were included-61 (74%) had moderate and 21 (26%) had severe encephalopathy. Mean (SD) hypothermia cooling induction time was 1.7 hour (1.5) and the effective cooling time 95% (0.08). The mean (SD) hypothermia induction time was 1.7 hour (1.5 hour), core temperature during cooling was 33.4°C (0.2), rewarming rate was 0.34°C (0.16°C) per hour and the effective cooling time was 95% (8%). Twenty-five (51%) babies had gastric bleeds, 6 (12%) had pulmonary bleeds and 21 (27%) had meconium on delivery. Fifteen (18%) babies died before discharge from hospital. Heart rate more than 120 bpm during cooling (P=0.01) and gastric bleeds (P<0.001) were associated with neonatal mortality.

CONCLUSIONS

The low-cost servo-controlled cooling device maintained the core temperature well within the target range. Adequately powered clinical trials are required to establish the safety and efficacy of TH in LMICs.

CLINICAL TRIAL REGISTRATION NUMBER

NCT01760629.