Therapeutic Hypothermia in Neonatal Hypoxic-Ischemic Encephalopathy

PURPOSE OF REVIEW

Therapeutic hypothermia reduces death or disability in term and near-term infants with moderate-severe hypoxic-ischemic encephalopathy. Nevertheless, many infants still survive with disability, despite hypothermia, supporting further research in to ways to further improve neurologic outcomes.

RECENT FINDINGS

Recent clinical and experimental studies have refined our understanding of the key parameters for hypothermic neuroprotection, including timing of initiation, depth, and duration of hypothermia, and subsequent rewarming rate. However, important knowledge gaps remain. There is encouraging clinical evidence from a small phase II trial that combined treatment of hypothermia with recombinant erythropoietin further reduces risk of disability but definitive studies are still needed. In conclusion, recent studies suggest that current protocols for therapeutic hypothermia are near-optimal, and that the key to better neurodevelopmental outcomes is earlier diagnosis and initiation of hypothermia after birth. Further research is essential to find and evaluate ways to further improve outcomes after hypoxic-ischemic encephalopathy, including add-on therapies for therapeutic hypothermia and preventing pyrexia during labor and delivery.

Neonatal encephalopathy and hypoxic-ischemic encephalopathy

Acute hypoxic-ischemic encephalopathy around the time of birth remains a major cause of death and life-long disability. The key insight that led to the modern revival of studies of neuroprotection was that, after profound asphyxia, many brain cells show initial recovery from the insult during a short "latent" phase, typically lasting approximately 6h, only to die hours to days later after a "secondary" deterioration characterized by seizures, cytotoxic edema, and progressive failure of cerebral oxidative metabolism. Studies designed around this framework showed that mild hypothermia initiated as early as possible before the onset of secondary deterioration and continued for a sufficient duration to allow the secondary deterioration to resolve is associated with potent, long-lasting neuroprotection. There is now compelling evidence from randomized controlled trials that mild to moderate induced hypothermia significantly improves survival and neurodevelopmental outcomes in infancy and mid-childhood.

Hypothermia Is Neuroprotective after Severe Hypoxic-Ischaemic Brain Injury in Neonatal Rats Pre-Exposed to PAM3CSK4

BACKGROUND

Preclinical research on the neuroprotective effect of hypothermia (HT) after perinatal asphyxia has shown variable results, depending on comorbidities and insult severity. Exposure to inflammation increases vulnerability of the neonatal brain to hypoxic-ischaemic (HI) injury, and could be one explanation for those neonates whose injury is unexpectedly severe. Gram-negative type inflammatory exposure by lipopolysaccharide administration prior to a mild HI insult results in moderate brain injury, and hypothermic neuroprotection is negated. However, the neuroprotective effect of HT is fully maintained after gram-positive type inflammatory exposure by PAM3CSK4 (PAM) pre-administration in the same HI model. Whether HT is neuroprotective in severe brain injury with gram-positive inflammatory pre-exposure has not been investigated.

METHODS

59 seven-day-old rat pups were subjected to a unilateral HI insult, with left carotid artery ligation followed by 90-min hypoxia (8% O2 at Trectal 36°C). An additional 196 pups received intraperitoneal 0.9% saline (control) or PAM1 mg/kg, 8 h before undergoing the same HI insult. After randomisation to 5 h normothermia (NT37°C) or HT32°C, pups survived 1 week before they were sacrificed by perfusion fixation. Brains were harvested for hemispheric and hippocampal area loss analyses at postnatal day 14, as well as immunostaining for neuron count in the HIP CA1 region.

RESULTS

Normothermic PAM animals (PAM-NT) had a comparable median area loss (hemispheric: 60% [95% CI 33-66]; hippocampal: 61% [95% CI 29-67]) to vehicle animals (Veh-NT) (hemispheric: 58% [95% CI 11-64]; hippocampal: 60% [95% CI 19-68]), which is defined as severe brain injury. Furthermore, mortality was low and similar in the two groups (Veh-NT 4.5% vs. PAM-NT 6.6%). HT reduced hemispheric and hippocampal injury in the Veh group by 13 and 28%, respectively (hemispheric: p = 0.048; hippocampal: p = 0.042). HT also provided neuroprotection in the PAM group, reducing hemispheric injury by 22% (p = 0.03) and hippocampal injury by 37% (p = 0.027).

CONCLUSION

In these experiments with severe brain injury, Toll-like receptor-2 triggering prior to HI injury does not have an additive injurious effect, and there is a small but significant neuroprotective effect of HT. HT appears to be neuroprotective over a continuum of injury severity in this model, and the effect size tapers off with increasing area loss. Our results indicate that gram-positive inflammatory exposure prior to HI injury does not negate the neuroprotective effect of HT in severe brain injury.

Fentanyl Induces Cerebellar Internal Granular Cell Layer Apoptosis in Healthy Newborn Pigs

Background

Opioids like fentanyl are regularly used in neonates for analgesia and sedation. So far, they have been reported to be safe and eligible to use. The cerebellum has become a focus of neurodevelopmental research within the last years, as it is known to play an important role in long-lasting motor, cognitive, and other behavioral changes. The cerebellar cortex is of major importance in the coordinative role of the cerebellum and highly vulnerable to injury and impaired growth.

Objective

This study was performed to evaluate the apoptotic effect of intravenous fentanyl infusion on the cerebellum in healthy newborn pigs.

Methods

Thirteen healthy pigs (<median 12 h old) were randomized into (1) 24 h of intravenous fentanyl at normothermia (NTFe, n = 6) or (2) non-ventilated controls at normothermia (NTCTR, n = 7). Cerebellar sections were morphologically assessed after staining with hematoxylin–eosin. In addition, paired sections were immuno-stained for cell death [Cleaved caspase-3 and terminal deoxynucleotidyl transferase-mediated deoxyuridine-triphosphate nick-end labeling (TUNEL)], and positive cells were counted in defined areas of the internal granular cell layer. In total, cells in three cerebellar gyri were counted.

Results

We found that there was an increase in cells with apoptotic morphology in the internal granular cell layer in the NTFe group. For quantification, we found a significant increase in cell death in group (1) [median (range) number of caspase-3-positive cell group (1) 8 (1–22) vs. group (2) 1 (1–6) and TUNEL-positive cells (1) 6 (1–10) vs. (2) 1 (0–4)]. In both groups, there was no difference in the number of Purkinje cells. Both groups had comparable and stable physiological parameters throughout the 24 h period.

Conclusion

Twenty-four hours of continuous intravenous fentanyl infusion increased apoptosis in the internal granular cell layer in the cerebellum of healthy newborn pigs.

Neonatal Systemic Inflammation Induces Inflammatory Reactions and Brain Apoptosis in a Pathogen-Specific Manner

BACKGROUND

After neonatal asphyxia, therapeutic hypothermia (HT) is the only proven treatment option. Although established as a neuroprotective therapy, benefit from HT has been questioned when infection is a comorbidity to hypoxic-ischaemic (HI) brain injury. Gram-negative and gram-positive species activate the immune system through different pathogen recognition receptors and subsequent immunological systems. In rodent models, gram-negative (lipopolysaccharide [LPS]) and gram-positive (PAM3CSK4 [PAM]) inflammation similarly increase neuronal vulnerability to HI. Interestingly, while LPS pre-sensitisation negates the neuroprotective effect of HT, HT is highly beneficial after PAM-sensitised HI brain injury.

OBJECTIVE

We aimed to examine whether systemic gram-positive or gram-negative inflammatory sensitisation affects juvenile rat pups per se, without an HI insult.

METHODS

Neonatal 7-day-old rats (n = 215) received intraperitoneal injections of vehicle (0.9% NaCl), LPS (0.1 mg/kg), or PAM (1 mg/kg). Core temperature and weight gain were monitored. Brain cytokine expression (IL-6, IL-1β, TNF-α, and IL-10, via PCR), apoptosis (cleaved caspase 3, via Western blots), and microglial activation (Iba1, via immunohistochemistry) were examined.

RESULTS

LPS induced an immediate drop in core temperature followed by poor weight gain, none of which were seen after PAM. Furthermore, LPS induced brain apoptosis, while PAM did not. The magnitude and temporal profile of brain cytokine expression differed between LPS- and PAM-injected animals.

CONCLUSION

These findings reveal sepsis-like conditions and neuroinflammation specific to the inflammatory stimulus (gram-positive vs. gram-negative) in the neonatal rat. They emphasise the importance of pre-clinical models being pathogen dependent, and should always be carefully tailored to their clinical scenario.

Reduced infancy and childhood epilepsy following hypothermia-treated neonatal encephalopathy

OBJECTIVE

To investigate what proportion of a regional cohort of cooled infants with neonatal encephalopathy develop epilepsy (determined by the International League Against Epilepsy [ILAE] definition and the number of antiepileptic drugs [AEDs]) up to 8 years of age.

METHODS

From 2006-2013, 151 infants with perinatal asphyxia underwent 72 h cooling. Clinical and amplitude-integrated electroencepalography (aEEG) with single-channel EEG-verified neonatal seizures were treated with AEDs. Brain magnetic resonance imaging (MRI) was assessed using a 0-11 severity score. Postneonatal seizures, epilepsy rates, and AED treatments were documented. One hundred thirty-four survivors were assessed at 18-24 months; adverse outcome was defined as death or Bayley III composite Cognition/Language or Motor scores <85 and/or severe cerebral palsy or severely reduced vision/hearing. Epilepsy rates in 103 children age 4-8 years were also documented.

RESULTS

aEEG confirmed seizures occurred precooling in 77 (57%) 151 of neonates; 48% had seizures during and/or after cooling and received AEDs. Only one infant was discharged on AEDs. At 18-24 months, one third of infants had an adverse outcome including 11% mortality. At 2 years, 8 (6%) infants had an epilepsy diagnosis (ILAE definition), of whom 3 (2%) received AEDs. Of the 103 4- to 8-year-olds, 14 (13%) had developed epilepsy, with 7 (7%) receiving AEDs. Infants/children on AEDs had higher MRI scores than those not on AEDs (median [interquartile range] 9 [8-11] vs. 2 [0-4]) and poorer outcomes. Nine (64%) of 14 children with epilepsy had cerebral palsy compared to 13 (11%) of 120 without epilepsy, and 10 (71%) of 14 children with epilepsy had adverse outcomes versus 23 (19%) of 120 survivors without epilepsy. The number of different AEDs given to control neonatal seizures, aEEG severity precooling, and MRI scores predicted childhood epilepsy.

SIGNIFICANCE

We report, in a regional cohort of infants cooled for perinatal asphyxia, 6% with epilepsy at 2 years (2% on AEDs) increasing to 13% (7% on AEDs) at early school age. These AED rates are much lower than those reported in the cooling trials, even with adjusting for our cohort's milder asphyxia. Long-term follow-up is needed to document final epilepsy rates.

Hypothermic Neuronal Rescue from Infection-Sensitised Hypoxic-Ischaemic Brain Injury Is Pathogen Dependent

Perinatal infection increases the vulnerability of the neonatal brain to hypoxic-ischaemic (HI) injury. Hypothermia treatment (HT) does not provide neuroprotection after pre-insult inflammatory sensitisation by lipopolysaccharide (LPS), a gram-negative bacterial wall constituent. However, early-onset sepsis in term babies is caused by gram-positive species in more than 90% of cases, and neuro-inflammatory responses triggered through the gram-negative route (Toll-like receptor 4, TLR-4) are different from those induced through the gram-positive route via TLR-2. Whether gram-positive septicaemia sensitises the neonatal brain to hypoxia and inhibits the neuroprotective effect of HT is unknown. Seven-day-old Wistar rats (n = 178) were subjected to intraperitoneal injections of PAM3CSK4 (1 mg/kg, a synthetic TLR-2 agonist) or vehicle (0.9% NaCl). After an 8-h delay, the left carotid artery was ligated followed by 50 min of hypoxia (8% O2) at a rectal temperature of 36°C. Pups received a 5-h treatment of normothermia (NT, 37°C) or HT (32°C) immediately after the insult. Brains were harvested after 7 days' survival for hemispheric and hippocampal area loss analyses and immunolabelling of microglia (Iba1) and hippocampal neurons (NeuN). Normothermic PAM3CSK4-injected animals showed significantly more brain injury than vehicle animals (p = 0.014). Compared to NT, HT significantly reduced injury in the PAM3CSK4-injected animals, with reduced area loss (p < 0.001), reduced microglial activation (p = 0.006), and increased neuronal rescue in the CA1 region (p < 0.001). Experimental induction of a sepsis-like condition through the gram-positive pathway sensitises the brain to HI injury. HT was highly neuroprotective after the PAM3CSK4-triggered injury, suggesting HT may be neuroprotective in the presence of a gram-positive infection. These results are in strong contrast to LPS studies where HT is not neuroprotective.

Monitoring of cerebral blood flow during hypoxia-ischemia and resuscitation in the neonatal rat using laser speckle imaging

Neonatal hypoxic-ischemic encephalopathy (HIE) is associated with alterations in cerebral blood flow (CBF) as a result of perinatal asphyxia. The extent to whichCBFchanges contribute to injury, and whether treatments that ameliorate these changes might be neuroprotective, is still unknown. Higher throughput techniques to monitorCBFchanges in rodent models ofHIEcan help elucidate the underlying pathophysiology. We developed a laser speckle imaging (LSI) technique to continuously monitorCBFin six postnatal-day 10 (P10) rats simultaneously before, during, and after unilateral hypoxia-ischemia (HI, ligation of the left carotid artery followed by hypoxia in 8% oxygen). After ligation,CBFto the ligated side fell by 30% compared to the unligated side (P < 0.0001). Hypoxia induced a bilateral 55% reduction inCBF, which was partially restored by resuscitation. Compared to resuscitation in air, resuscitation in 100% oxygen increasedCBFto the ligated side by 45% (P = 0.033). Individual variability inCBFresponse to hypoxia between animals accounted for up to 24% of the variability in hemispheric area loss to the ligated side. In both P10 and P7 models of unilateralHI, resuscitation in 100% oxygen did not affect hemispheric area loss, or hippocampalCA1 pyramidal neuron counts, after 1-week survival. ContinuousCBFmonitoring usingLSIin multiple rodents simultaneously can screen potential treatment modalities that affectCBF, and provide insight into the pathophysiology ofHI.

Xenon depresses aEEG background voltage activity whilst maintaining cardiovascular stability in sedated healthy newborn pigs

BACKGROUND

Changes in electroencephalography (EEG) voltage range are used to monitor the depth of anaesthesia, as well as predict outcome after hypoxia-ischaemia in neonates. Xenon is being investigated as a potential neuroprotectant after hypoxic-ischaemic brain injury, but the effect of Xenon on EEG parameters in children or neonates is not known. This study aimed to examine the effect of 50% inhaled Xenon on background amplitude-integrated EEG (aEEG) activity in sedated healthy newborn pigs.

METHODS

Five healthy newborn pigs, receiving intravenous fentanyl sedation, were ventilated for 24 h with 50%Xenon, 30%O2 and 20%N2 at normothermia. The upper and lower voltage-range of the aEEG was continuously monitored together with cardiovascular parameters throughout a 1 h baseline period with fentanyl sedation only, followed by 24 h of Xenon administration.

RESULTS

The median (IQR) upper and lower aEEG voltage during 1 h baseline was 48.0 μV (46.0-50.0) and 25.0 μV (23.0-26.0), respectively. The median (IQR) aEEG upper and lower voltage ranges were significantly depressed to 21.5 μV (20.0-26.5) and 12.0 μV (12.0-16.5) from 10 min after the onset of 50% Xenon administration (p=0.002). After the initial Xenon induced depression in background aEEG voltage, no further aEEG changes were seen over the following 24h of ventilation with 50% xenon under fentanyl sedation. Mean arterial blood pressure and heart rate remained stable.

CONCLUSION

Mean arterial blood pressure and heart rate were not significantly influenced by 24h Xenon ventilation. 50% Xenon rapidly depresses background aEEG voltage to a steady ~50% lower level in sedated healthy newborn pigs. Therefore, care must be taken when interpreting the background voltage in neonates also receiving Xenon.

Less severe cerebral palsy outcomes in infants treated with therapeutic hypothermia

AIM

To describe the incidence, type and severity of cerebral palsy at 24 months in a regional cohort of infants treated with whole-body therapeutic hypothermia for neonatal encephalopathy.

METHODS

Data were collected prospectively in a regional centre providing TH. Antenatal and perinatal clinical variables and severity of encephalopathy were collected. Infants were assessed at 18 months using the Bayley Scales of Infant and Toddler Development-III, and the presence and severity of CP was investigated at 24 months.

RESULTS

A total of 125 of 132 infants fulfilled entry criteria for TH trials and completed 72 h of TH. Sixteen (13%) of the 125 infants died, and eight (6%) were not available for follow-up. Eighteen infants (14%; 18% of those assessed) developed CP. Of these, 12 (67%) were classified using the Gross Motor Function Classification System, at level 1, six (33%) at level 5 and none at levels 2, 3 or 4.

CONCLUSION

Our regional clinical cohort had lower mortality and comparable rates of CP compared with historical outcomes in TH trials. In contrast to historical cohorts, only one-third of the 18 children with CP were severely affected and 12 were mildly affected, all of whom were independently ambulant by 24 months.

The effect of resuscitation in 100% oxygen on brain injury in a newborn rat model of severe hypoxic-ischaemic encephalopathy

AIM

Infants with birth asphyxia frequently require resuscitation. Current guidance is to start newborn resuscitation in 21% oxygen. However, infants with severe hypoxia-ischaemia may require prolonged resuscitation with oxygen. To date, no study has looked at the effect of resuscitation in 100% oxygen following a severe hypoxic-ischaemic insult.

METHODS

Postnatal day 7 Wistar rats underwent a severe hypoxic-ischaemic insult (modified Vannucci unilateral brain injury model) followed by immediate resuscitation in either 21% or 100% oxygen for 30 min. Seven days following the insult, negative geotaxis testing was performed in survivors, and the brains were harvested. Relative ipsilateral cortical and hippocampal area loss was assessed histologically.

RESULTS

Total area loss in the affected hemisphere and area loss within the hippocampus did not significantly differ between the two groups. The same results were seen for short-term neurological assessment. No difference was seen in weight gain between pups resuscitated in 21% and 100% oxygen.

CONCLUSION

Resuscitation in 100% oxygen does not cause a deleterious effect on brain injury following a severe hypoxic-ischaemic insult in a rat model of hypoxia-ischaemia. Further work investigating the effects of resuscitation in 100% oxygen is warranted, especially for newborn infants with severe hypoxic-ischaemic encephalopathy.

Brain imaging in cooled encephalopathic neonates does not differ between four and 11 days after birth

AIM

The optimal timing of magnetic resonance imaging (MRI) in encephalopathic infants treated with hypothermia is unknown, and this study examined whether early scans differed from later scans.

METHODS

We assessed paired MRI scans carried out on 41 cooled encephalopathic infants at a median of four and 11 days using two scoring systems: the Rutherford injury scores for the basal ganglia and thalami (BGT), white matter and the posterior limb of the internal capsule, and the Bonifacio injury scores for the BGT and watershed area.

RESULTS

Both systems produced consistent injury severity scores in 37 of 41 infants on both days, with Rutherford scores predicting poor outcome in six early scans and seven later scans (K = 0.91) and Bonifacio doing the same in seven and nine scans (K = 0.85). A white matter/watershed score of two or a BGT score of one indicated severe changes by day 11 in three infants, but lower scores did not.

CONCLUSION

Magnetic resonance imaging scans indicated that the Rutherford and Bonifacio systems produced similar scores in 37 of 41 cooled encephalopathic infants at a median of four and 11 days. Infants with an early white matter/watershed scores of two or a BGT score of one may worsen and should be rescanned.

The feasibility of using a portable xenon delivery device to permit earlier xenon ventilation with therapeutic cooling of neonates during ambulance retrieval

BACKGROUND

Therapeutic hypothermia is the standard of care after perinatal asphyxia. Preclinical studies show 50% xenon improves outcome, if started early.

METHODS

During a 32-patient study randomized between hypothermia only and hypothermia with xenon, 5 neonates were given xenon during retrieval using a closed-circuit incubator-mounted system.

RESULTS

Without xenon availability during retrieval, 50% of eligible infants exceeded the 5-hour treatment window. With the transportable system, 100% were recruited. Xenon delivery lasted 55 to 120 minutes, using 174 mL/h (117.5-193.2) (median [interquartile range]), after circuit priming (1300 mL).

CONCLUSIONS

Xenon delivery during ambulance retrieval was feasible, reduced starting delays, and used very little gas.

Hypothermia Does Not Reverse Cellular Responses Caused by Lipopolysaccharide in Neonatal Hypoxic-Ischaemic Brain Injury

INTRODUCTION

Bacterial lipopolysaccharide (LPS) injection prior to hypoxia-ischaemia significantly increases hypoxia-ischaemic brain injury in 7-day-old (P7) rats. In addition, therapeutic hypothermia (HT) is not neuroprotective in this setting. However, the mechanistic aspects of this therapeutic failure have yet to be elucidated. This study was designed to investigate the underlying cellular mechanisms in this double-hit model of infection-sensitised hypoxia-ischaemic brain injury.

MATERIAL AND METHODS

P7 rat pups were injected with either vehicle or LPS, and after a 4-hour delay were exposed to left carotid ligation followed by global hypoxia inducing a unilateral stroke-like hypoxia-ischaemic injury. Pups were randomised to the following treatments: (1) vehicle-treated pups receiving normothermia treatment (NT) (Veh-NT; n = 40), (2) LPS-treated pups receiving NT treatment (LPS-NT; n = 40), (3) vehicle-treated pups receiving HT treatment (Veh-HT; n = 38) and (4) LPS-treated pups receiving HT treatment (LPS-HT; n = 35). On postnatal day 8 or 14, Western blot analysis or immunohistochemistry was performed to examine neuronal death, apoptosis, astrogliosis and microglial activation.

RESULTS

LPS sensitisation prior to hypoxia-ischaemia significantly exacerbated apoptotic neuronal loss. NeuN, a neuronal biomarker, was significantly reduced in the LPS-NT and LPS-HT groups (p = 0.008). Caspase-3 activation was significantly increased in the LPS-sensitised groups (p < 0.001). Additionally, a significant increase in astrogliosis (glial fibrillary acidic expression, p < 0.001) was seen, as well as a trend towards increased microglial activation (Iba 1 expression, p = 0.051) in LPS-sensitised animals. Treatment with HT did not counteract these changes.

CONCLUSION

LPS-sensitised hypoxia-ischaemic brain injury in newborn rats is mediated through neuronal death, apoptosis, astrogliosis and microglial activation. In this double-hit model, treatment with HT does not ameliorate these changes.

Minimal systemic hypothermia combined with selective head cooling evaluated in a pig model of hypoxia-ischemia

BACKGROUND

Selective head cooling (SHC) with moderate hypothermia (HT) and whole-body cooling are beneficial following perinatal asphyxia. SHC with systemic normothermia (NT) or minimal HT is under-investigated, could obviate systemic complications of moderate HT, and be applicable to preterm infants. We hypothesized that minimal systemic HT with SHC following hypoxia-ischemia (HI) would be neuroprotective compared with systemic NT.

METHODS

Newborn pigs underwent global HI causing permanent brain injury before being randomized to NT (rectal temperature (Trectal) 38.5 °C) or minimal HT (Trectal 37.0 °C) with SHC (cooling cap and body wrap) for 48 h followed by 24-h NT with 72-h survival.

RESULTS

SHC did not reduce global or regional neuropathology score when correcting for insult severity or compared with a NT group matched for HI severity but increased mortality by 26%. During 48 h, the SHC mean ± SD Trectal was 37.0 ± 0.2 °C, and Tdeep brain and Tsuperficial brain were 35.0 ± 1.1 °C and 31.5 ± 1.6 °C, respectively, with stable Tbrain achieved ≥ 3 h after starting cooling.

CONCLUSION

This is the first study in newborn pigs of minimal systemic HT with SHC for 48 h and a further 24 h of NT following HI. Mortality was increased in the cooled group with no neuroprotection in survivors.

Who should we cool after perinatal asphyxia?

Three ongoing challenges have arisen after the introduction of therapeutic hypothermia (TH) as standard of care for term newborns with moderate or severe perinatal asphyxia: (i) to ensure that the correct group of infants are cooled; (ii) to optimize the delivery of TH and intensive care in relation to the severity of the encephalopathy; (iii) to systematically follow up the long-term efficacy of TH using comparable outcome data between centers and countries. This review addresses the entry criteria for TH, and discusses potential issues regarding patient selection, and management of TH: cooling mild, moderate, and very severe perinatal asphyxia, cooling longer or deeper, and/or starting with a greater delay. This includes cooling of patients outside of standard trial entry criteria, such as after postnatal collapse, premature infants, those with infection, and infants with metabolic, chromosomal or surgical diagnoses in addition to perinatal asphyxia.

Cooling neonates who do not fulfil the standard cooling criteria - short- and long-term outcomes

AIM

Therapeutic hypothermia is effective and without serious adverse effects in term infants with hypoxic-ischaemic encephalopathy. It is unknown whether other neonatal patient groups could benefit from therapeutic hypothermia. Since 2006, our centre has offered cooling to infants fulfilling the standard cooling criteria, but also to those who did not.

METHODS

Observational study with prospective data collection over a 6-year period in a regional cooling centre. Complications and outcome were compared between infants who were cooled not fulfilling the standard inclusion and exclusion criteria as set out in the CoolCap/TOBY protocol (n = 36) and infants who fulfilled the standard entry criteria (n = 129).

RESULTS

21.8% of cooled infants did not fulfil standard cooling entry criteria. This included infants cooled >6 postnatal hours, late preterm infants, and infants with postnatal collapse, major cranial haemorrhage, congenital cardiac disease and surgical conditions. Complication rates and long-term outcome did not differ significantly between the groups, apart from in infants with a major cranial haemorrhage, who had higher rates of coagulopathy and the worst outcome (80% death/disability).

CONCLUSION

Cooling can be considered for infants with neonatal encephalopathy following postnatal collapse or preterm birth, those with underlying surgical or cardiac conditions, and infants starting cooling >6 postnatal hours.