Treatment of term infants with head cooling and mild systemic hypothermia (35.0 degrees C and 34.5 degrees C) after perinatal asphyxia

Hypothermia: a systematic review and meta-analysis of clinical trials

Hypothermia is a potential neuroprotective intervention to treat neonatal post-asphyxial (hypoxic-ischemic) encephalopathy (HIE). In this meta-analysis of 13 clinical trials published to date, therapeutic hypothermia was associated with a highly reproducible reduction in the risk of the combined outcome of mortality or moderate-to-severe neurodevelopmental disability in childhood. This improvement was internally consistent, as shown by significant reductions in the individual risk for death, moderate-to-severe neurodevelopmental disability, severe cerebral palsy, cognitive delay, and psychomotor delay. Patients in the hypothermia group had higher incidences of arrhythmia and thrombocytopenia; however, these were not clinically important. This analysis supports the use of hypothermia in reducing the risk of the mortality or moderate-to-severe neurodevelopmental disability in infants with moderate HIE.

Selective head cooling with mild systemic hypothermia after neonatal hypoxic-ischemic encephalopathy: a multicenter randomized controlled trial in China

OBJECTIVE

To investigate the efficacy and safety of selective head cooling with mild systemic hypothermia in hypoxic-ischemic encephalopathy (HIE) in newborn infants.

STUDY DESIGN

Infants with HIE were randomly assigned to the selective head cooling or control group. Selective head cooling was initiated within 6 hours after birth to a nasopharyngeal temperature of 34 degrees+/-0.2 degrees C and rectal temperature of 34.5 degrees to 35.0 degrees C for 72 hours. Rectal temperature was maintained at 36.0 degrees to 37.5 degrees C in the control group. Neurodevelopmental outcome was assessed at 18 months of age. The primary outcome was a combined end point of death and severe disability.

RESULTS

One hundred ninety-four infants were available for analysis (100 and 94 infants in the selective head cooling and control group, respectively). For the selective head cooling and control groups, respectively, the combined outcome of death and severe disability was 31% and 49% (OR: 0.47; 95% CI: 0.26-0.84; P=.01), the mortality rate was 20% and 29% (OR:0.62; 95% CI: 0.32-1.20; P=.16), and the severe disability rate was 14% (11/80) and 28% (19/67) (OR: 0.40; 95% CI: 0.17-0.92; P=.01).

CONCLUSIONS

Selective head cooling combined with mild systemic hypothermia for 72 hours may significantly decrease the combined outcome of severe disability and death, as well as severe disability.

Therapeutic hypothermia for neonatal hypoxic ischaemic encephalopathy

There is now a strong evidence base supporting therapeutic hypothermia for infants with moderate or severe neonatal hypoxic ischaemic encephalopathy. Experimental and clinical data indicate that induced hypothermia reduces cerebral hypoxic ischaemic injury and randomized clinical trials in newborns with hypoxic ischaemic encephalopathy confirm improved neurological outcomes and survival at 18 months of age with therapeutic hypothermia. Studies are on-going to confirm whether these benefits are maintained in later childhood. Efforts are now focused on optimal implementation of therapeutic hypothermia in clinical practice: training in the assessment of severity of encephalopathy; initiation and maintenance of hypothermia before admission to a cooling facility; care of the infant during cooling; and appropriate investigation and follow-up are crucial for optimizing neurological outcomes. The establishment of registries of infants with hypoxic ischaemic encephalopathy and audit are important for guiding clinical practice.

State of the science: hypoxic ischemic encephalopathy and hypothermic intervention for neonates

Perinatal asphyxia and resulting hypoxic ischemic encephalopathy (HIE) occur in 1 to 3 per 1000 births in the United States. Induced hypothermia as an intervention for asphyxiated infants offers promising results in reducing neurodevelopmental disabilities in surviving infants. Induced hypothermia and selective head cooling are effective interventions for asphyxiated infants that minimize continued neuronal damage and decrease neurodevelopmental disability at 18 months of age. Identification of affected infants immediately after delivery and transfer to a facility that provides this therapy is necessary to maximize the potential of this intervention. Standardization of hypothermia protocols within neonatal intensive care units is essential for providing hypothermia as a treatment of HIE in infants. This article explores the pathophysiology of HIE, identifying infants at risk for HIE as a result of perinatal asphyxia, the use of hypothermic intervention for compromised infants, and barriers to the implementation of treatment.

Sepsis-Related Mortality of Very Low Birth Weight Brazilian Infants: The Role of Pseudomonas aeruginosa

The aim of this study is to identify risk factors for sepsis-related mortality in low birth weight (<1500 g) infants. We performed retrospective cohort study to investigate risk factors for sepsis-related mortality in all neonates birth weight <1500 g admitted to Level III neonatal intensive care unit, Brazil, April 2001/September 2004. Of the 203 cases, 71 (35%) had sepsis. Of those, gram-positive was identified in 52/87 blood cultures (59.8%), the most common Coagulase-negative Staphylococcus (31/87; 35.5%). Gram-negative was present in 29 of the 87 positive blood cultures (33.3%), with Pseudomonas aeruginosa (8/87; 9.1%), the most frequent agent. Overall 21 of 71 infants with sepsis (29.6%) died. Risk factors for sepsis-related mortality were gestational age </=28 weeks, birth weight </=1000 g (9.6 times more often than birth weight >1000 g), five-minute Apgar </=7, gram-negative sepsis, mechanical ventilation (6.7 times higher than no use), and intravascular catheter. Sepsis-related mortality was due, mainly, to Pseudomonas aeruginosa; birth weight </=1000 g and mechanical ventilation were strong sepsis-related mortality predictors.

Therapeutic hypothermia: applications in pediatric cardiac arrest

There is a rich history for the use of therapeutic hypothermia after cardiac arrest in neonatology and pediatrics. Laboratory reports date back to 1824 in experimental perinatal asphyxia. Similarly, clinical reports in pediatric cold water drowning victims represented key initiating work in the field. The application of therapeutic hypothermia in pediatric drowning victims represented some of the seminal clinical use of this modality in modern neurointensive care. Uncontrolled application (too deep and too long) and unique facets of asphyxial cardiac arrest in children (a very difficult insult to affect any benefit) likely combined to result in abandonment of therapeutic hypothermia in the mid to late 1980s. Important studies in perinatal medicine have built upon the landmark clinical trials in adults, and are once again bringing therapeutic hypothermia into standard care for pediatrics. Although more work is needed, particularly in the use of mild therapeutic hypothermia in children, there is a strong possibility that this important therapy will ultimately have broad applications after cardiac arrest and central nervous system (CNS) insults in the pediatric arena.

Post-cardiac arrest syndrome: Epidemiology, pathophysiology, treatment, and prognostication: A scientific statement from the International Liaison Committee on Resuscitation; the American Heart Association Emergency Cardiovascular Care Committee; the Council on Cardiovascular Surgery and Anesthesia; the Council on Cardiopulmonary, Perioperative, and Critical Care; the Council on Clinical Cardiology; the Council on Stroke (Part 1)

AIM OF THE REVIEW

To review the epidemiology, pathophysiology, treatment and prognostication in relation to the post-cardiac arrest syndrome.

METHODS

Relevant articles were identified using PubMed, EMBASE and an American Heart Association EndNote master resuscitation reference library, supplemented by hand searches of key papers. Writing groups comprising international experts were assigned to each section. Drafts of the document were circulated to all authors for comment and amendment.

RESULTS

The 4 key components of post-cardiac arrest syndrome were identified as (1) post-cardiac arrest brain injury, (2) post-cardiac arrest myocardial dysfunction, (3) systemic ischaemia/reperfusion response, and (4) persistent precipitating pathology.

CONCLUSIONS

A growing body of knowledge suggests that the individual components of the postcardiac arrest syndrome are potentially treatable.

Hypothermia therapy after pediatric cardiac arrest

BACKGROUND

Hypothermia therapy improves mortality and functional outcome after cardiac arrest and birth asphyxia in adults and newborns. The effect of hypothermia therapy in infants and children with cardiac arrest is unknown.

METHODS AND RESULTS

A 2-year, retrospective, 5-center study was conducted, and 222 patients with cardiac arrest were identified. Seventy-nine (35.6%) of these patients met eligibility criteria for the study (age >40 weeks postconception and <18 years, cardiac arrest >3 minutes in duration, survival for > or = 12 hours after return of circulation, and no birth asphyxia). Twenty-nine (36.7%) of these 79 patients received hypothermia therapy and were cooled to 33.7+/-1.3 degrees C for 20.8+/-11.9 hours. Hypothermia therapy was associated with higher mortality (P=0.009), greater duration of cardiac arrest (P=0.005), more resuscitative interventions (P<0.001), higher postresuscitation lactate levels (P<0.001), and use of extracorporeal membrane oxygenation (P<0.001). When adjustment was made for duration of cardiac arrest, use of extracorporeal membrane oxygenation, and propensity scores by use of a logistic regression model, no statistically significant differences in mortality were found (P=0.502) between patients treated with hypothermia therapy and those treated with normothermia. Also, no differences in hypothermia-related adverse events were found between groups.

CONCLUSIONS

Hypothermia therapy was used in resuscitation scenarios that are associated with greater risk of poor outcome. In an adjusted analysis, the effectiveness of hypothermia therapy was neither supported nor refuted. A randomized controlled trial is needed to rigorously evaluate the benefits and harms of hypothermia therapy after pediatric cardiac arrest.

Does head cooling with mild systemic hypothermia affect requirement for blood pressure support?

OBJECTIVE

Our goal was to evaluate whether head cooling with mild systemic hypothermia for neonatal encephalopathy is associated with greater requirement for volume or inotrope support.

PATIENTS AND METHODS

We studied term infants (>/=36 weeks) with moderate-to-severe neonatal encephalopathy plus abnormal amplitude integrated electroencephalography, randomly assigned to head cooling for 72 hours starting within 6 hours of birth, with the rectal temperature maintained at 34.5 degrees C +/- 0.5 degrees C (n = 112), or conventional care (n = 118).

DESIGN

This was a multicenter randomized, controlled study (the CoolCap trial). The primary outcome was the time relationship between mean arterial blood pressure and subsequent administration of inotropes or volume administration.

RESULTS

Pooled data from 0 to 76 hours after randomization revealed no difference in mean arterial blood pressure between groups and significantly lower mean heart rate during cooling. The use of inotropes or volume was related to preceding mean arterial blood pressure and not to treatment group in the first 24 hours. In contrast, from 24 to 76 hours, there was no effect of mean arterial blood pressure, but there was an overall reduction in pressure support over time and significantly more frequent pressure support in the cooled group than in controls.

CONCLUSIONS

Mild systemic hypothermia did not affect arterial blood pressure or initial treatment with inotropes or volume in infants with moderate-to-severe encephalopathy but was associated with an apparent change in physician behavior, with slower withdrawal of therapy in cooled infants.

Advanced neuroimaging techniques for the term newborn with encephalopathy

Neonatal encephalopathy is associated with a high risk of morbidity and mortality in the neonatal period and of long-term neurodevelopmental disability in survivors. Advanced magnetic resonance techniques now play a major role in the clinical care of newborns with encephalopathy and in research addressing this important condition. From conventional magnetic resonance imaging, typical patterns of injury have been defined in neonatal encephalopathy. When applied in contemporary cohorts of newborns with encephalopathy, the patterns of brain injury on magnetic resonance imaging distinguish risk factors, clinical presentation, and risk of abnormal outcome. Advanced magnetic resonance techniques such as magnetic resonance spectroscopy, diffusion-weighted imaging, and diffusion tensor imaging provide novel perspectives on neonatal brain metabolism, microstructure, and connectivity. With the application of these imaging tools, it is increasingly apparent that brain injury commonly occurs at or near the time of birth and evolves over the first weeks of life. These observations have complemented findings from trials of emerging strategies of brain protection, such as hypothermia. Application of these advanced magnetic resonance techniques may enable the earliest possible identification of newborns at risk of neurodevelopmental impairment, thereby ensuring appropriate follow-up with rehabilitation and psychoeducational resources.

Thermoregulatory management for mild therapeutic hypothermia

In recent years the use of mild therapeutic hypothermia as a means of neuroprotection has become an important concept for treatment after cerebral ischemic hypoxic injury. Mild therapeutic hypothermia has been shown to improve outcome after out-of-hospital cardiac arrest, and many studies suggest a beneficial effect of mild therapeutic hypothermia on patient outcome after traumatic brain injury, cerebrovascular damage and neonatal asphyxia. This review article explores the numerous possibilities and methods for the induction of mild therapeutic hypothermia, reviews thermoregulatory management during maintenance and discusses associated risks and complications.

Hypothermia for hypoxic-ischemic encephalopathy

We are entering an era in which hypothermia will be used in combination with other novel neuroprotective interventions. The targeting of multiple sites in the cascade leading to brain injury may prove to be a more effective treatment strategy after hypoxic-ischemic encephalopathy in newborn infants than hypothermia alone.

Prognostic value of electroencephalograms in asphyxiated newborns treated with hypothermia

Previous studies described how early electroencephalogram patterns in neonatal hypoxic-ischemic encephalopathy seem to correlate with the severity of the clinical picture and provide prognostic information. This study evaluated whether electroencephalograms of newborns with severe perinatal hypoxic-ischemic encephalopathy, treated with hypothermia, provide information on clinical outcomes. Twenty-three newborns treated with hypothermia underwent electroencephalogram monitoring within 48 hours of age, and were enrolled in a follow-up with sequential electroencephalogram and neurologic controls (at ages 1 week, 1 month, 3-6 months, and 1 year). An inactive electroencephalogram pattern in the first 48 hours of age was associated with death or major neurologic sequelae. At age 1 week, a low-voltage, continuous pattern indicated a worse prognostic value when compared with other patterns. The persistence of electroencephalogram abnormalities at age 1 month was associated with a higher risk of neurologic sequelae. Background electroencephalogram abnormalities, detected in the first days of life after hypoxic-ischemic encephalopathy, can provide prognostic information, even in patients treated with hypothermia. After 1 month of age, the information on clinical outcomes provided by electroencephalograms usually decreases because of the natural trend toward electroencephalogram normalization.

Traumatic brain injury in children: recent advances in management

To define and discuss new developments in the field of pediatric traumatic brain injury (TBI). Review of several recent key studies on therapy since publication of the first U.S. traumatic brain injury guidelines in 2003. In addition, we discuss new developments in the use of biomarkers of brain injury in TBI diagnosis and also discuss recent advances in bedside neuromonitoring that may be helpful in the setting of pediatric brain injury. Important new information on optimal cerebral perfusion pressure management, cerebrospinal fluid drainage, decompressive craniectomy, hypothermia, biomarkers of brain injury along with advances in neuromonitoring are presented. The 2003 guidelines have stimulated important new research. This is reshaping bedside care.

Post-cardiac arrest syndrome: epidemiology, pathophysiology, treatment, and prognostication. A Scientific Statement from the International Liaison Committee on Resuscitation; the American Heart Association Emergency Cardiovascular Care Committee; the Council on Cardiovascular Surgery and Anesthesia; the Council on Cardiopulmonary, Perioperative, and Critical Care; the Council on Clinical Cardiology; the Council on Stroke

AIM OF THE REVIEW

To review the epidemiology, pathophysiology, treatment and prognostication in relation to the post-cardiac arrest syndrome.

METHODS

Relevant articles were identified using PubMed, EMBASE and an American Heart Association EndNote master resuscitation reference library, supplemented by hand searches of key papers. Writing groups comprising international experts were assigned to each section. Drafts of the document were circulated to all authors for comment and amendment.

RESULTS

The 4 key components of post-cardiac arrest syndrome were identified as (1) post-cardiac arrest brain injury, (2) post-cardiac arrest myocardial dysfunction, (3) systemic ischaemia/reperfusion response, and (4) persistent precipitating pathology.

CONCLUSIONS

A growing body of knowledge suggests that the individual components of the post-cardiac arrest syndrome are potentially treatable.

Outcomes of safety and effectiveness in a multicenter randomized, controlled trial of whole-body hypothermia for neonatal hypoxic-ischemic encephalopathy

BACKGROUND

Whole-body hypothermia reduced the frequency of death or moderate/severe disabilities in neonates with hypoxic-ischemic encephalopathy in a randomized, controlled multicenter trial.

OBJECTIVE

Our goal was to evaluate outcomes of safety and effectiveness of hypothermia in infants up to 18 to 22 months of age.

DESIGN/METHODS

A priori outcomes were evaluated between hypothermia (n = 102) and control (n = 106) groups.

RESULTS

Encephalopathy attributable to causes other than hypoxia-ischemia at birth was not noted. Inotropic support (hypothermia, 59% of infants; control, 56% of infants) was similar during the 72-hour study intervention period in both groups. Need for blood transfusions (hypothermia, 24%; control, 24%), platelet transfusions (hypothermia, 20%; control, 12%), and volume expanders (hypothermia, 54%; control, 49%) was similar in the 2 groups. Among infants with persistent pulmonary hypertension (hypothermia, 25%; control, 22%), nitric-oxide use (hypothermia, 68%; control, 57%) and placement on extracorporeal membrane oxygenation (hypothermia, 4%; control, 9%) was similar between the 2 groups. Non-central nervous system organ dysfunctions occurred with similar frequency in the hypothermia (74%) and control (73%) groups. Rehospitalization occurred among 27% of the infants in the hypothermia group and 42% of infants in the control group. At 18 months, the hypothermia group had 24 deaths, 19 severe disabilities, and 2 moderate disabilities, whereas the control group had 38 deaths, 25 severe disabilities, and 1 moderate disability. Growth parameters were similar between survivors. No adverse outcomes were noted among infants receiving hypothermia with transient reduction of temperature below a target of 33.5 degrees C at initiation of cooling. There was a trend in reduction of frequency of all outcomes in the hypothermia group compared with the control group in both moderate and severe encephalopathy categories.

CONCLUSIONS

Although not powered to test these secondary outcomes, whole-body hypothermia in infants with encephalopathy was safe and was associated with a consistent trend for decreasing frequency of each of the components of disability.

Induced hypothermia and fever control for prevention and treatment of neurological injuries

Increasing evidence suggests that induction of mild hypothermia (32-35 degrees C) in the first hours after an ischaemic event can prevent or mitigate permanent injuries. This effect has been shown most clearly for postanoxic brain injury, but could also apply to other organs such as the heart and kidneys. Hypothermia has also been used as a treatment for traumatic brain injury, stroke, hepatic encephalopathy, myocardial infarction, and other indications. Hypothermia is a highly promising treatment in neurocritical care; thus, physicians caring for patients with neurological injuries, both in and outside the intensive care unit, are likely to be confronted with questions about temperature management more frequently. This Review discusses the available evidence for use of controlled hypothermia, and also deals with fever control. Besides discussing the evidence, the aim is to provide information to help guide treatments more effectively with regard to timing, depth, duration, and effective management of side-effects. In particular, the rate of rewarming seems to be an important factor in establishing successful use of hypothermia in the treatment of neurological injuries.

Use of induced hypothermia for neuroprotection: indications and application

Therapeutic temperature regulation has become an exciting field of interest. Mild-to-moderate hypothermia is a safe and feasible management strategy for neuroprotection and control of intracranial pressure in neurological catastrophies such as traumatic brain injury, subarachnoid and intracerebral hemorrhage, and large hemispheric stroke. Fever is associated with worse neurological outcome in patients with brain injury, normothermia may be of benefit in this patient population. The efficacy of mild-to-moderate hypothermia has been proven for neuroprotection after cardiac arrest with ventricular fibrillation as initial rhythm, and after neonatal asphyxia. Application of hypothermia and fever control in neurocritical care, available cooling technologies and systemic effects and complications of hypothermia will be discussed.

Biopterin in the acute phase of hypoxia-ischemia in a neonatal pig model

To clarify the participation of inducible NOS (iNOS) in the hypoxia-ischemia, we examined iNOS and its tetrahydrobiopterin co-factor in the cerebral cortex and plasma in a newborn-piglet model. We also investigated the role of hypothermia in iNOS expression and biopterin production. Male newborn piglets were ventilated 6% oxygen for 45 min. Their common carotid arteries were clamped during hypoxia. Then they were resuscitated with 30% oxygen (HI group). Piglets of the hypothermia group were treated as the HI group and their body was cooled to 35.5 degrees C after hypoxic-ischemic insults. Sham-treated piglets were also reserved. In the HI group, iNOS was present in neurons and macrophages of the cerebral cortex 12h after the insult. The concentrations of nitrite and nitrate were elevated in the cerebral cortex 12h after hypoxic-ischemic insults but the biopterin level was unchanged. The plasma biopterin concentration after the insult (377.9+/-78.7 nM) was five times higher than before the insult (80.1+/-4.3 nM); this level peaked 4h after the insult (604.8+/-200.9 nM) and only slightly decreased after 12h (445.9+/-57.8 nM). In the hypothermia group, no iNOS expression was observed 12h after the insult. The plasma biopterin concentration after the insult (464.2+/-92.3 nM) was similar to that in the HI group, but was suppressed by 4h of hypothermia (229.3+/-106.8 nM). In this study, neuronal iNOS expression and increase of NO production were found in the acute phase of hypoxia-ischemia. Brain biopterin did not increase in hypoxia-ischemia although plasma biopterin was five-fold elevated. The discrepancy may also affect hypoxic-ischemic organ damage.

CoolSim: using industrial modeling techniques to examine the impact of selective head cooling in a model of perinatal regionalization

OBJECTIVE

A selective head-cooling device for the treatment of moderate to severe hypoxic-ischemic encephalopathy has been approved by the Food and Drug Administration for use in the United States. To reflect the complexity of health care delivery at the systems level, we used the industrial modeling technique of discrete event simulation to analyze the impact of various deployment strategies for selective head cooling and its partner technology, amplitude-integrated electroencephalography.

METHODS

We modeled the course through the perinatal system of all births in Massachusetts over a 1-year period. Cohort and care characteristics were drawn from existing databases. Results of a recently published trial were used to estimate the effects of selective head cooling. One thousand cohort replications were conducted to assess uncertainty. Several policy alternatives were examined, including no use of selective head cooling and scenarios that altered the number and placement of selective head-cooling and amplitude-integrated electroencephalography units throughout the state. Patient-level outcome and cost data were assessed.

RESULTS

For all scenarios tested, the use of amplitude-integrated electroencephalography/selective head cooling resulted in better outcomes at lower cost. However, substantial differences in transfer rates, failure-to-cool rates, and total costs were seen across scenarios. Optimal decision-making regarding the number and placement of devices led to a 16% improvement in cost savings and a 10-fold decrease in failure-to-cool rates, compared with other deployment scenarios. These results were insensitive to significant changes in model inputs.

CONCLUSIONS

On the basis of currently available data, the package of amplitude-integrated electroencephalography and selective head cooling seems to be an economically desirable intervention. Quantifiable techniques to assess system-wide technology performance provide a powerful approach to informing decisions regarding the structure and function of health care systems.

Safety of deep hypothermia in treating neonatal asphyxia

BACKGROUND

Several studies have demonstrated the efficiency and safety of mild hypothermia (33 degrees C) used for treating moderate encephalopathy. In animal models, deep hypothermia proved to be neuroprotective.

OBJECTIVES

To determine the safety of whole-body deep hypothermia between 30 and 33 degrees C in moderate-severe hypoxic-ischemic encephalopathy in newborn term infants.

METHODS

Mortality rates, incidence of brain damage detected by magnetic resonance imaging (MRI) and neurological outcomes of 39 term asphyxiated infants were retrospectively compared. A first group of patients (control group C) was treated with routine standard methods, a second group (MH) was treated with mild whole-body hypothermia (32-34 degrees C) and a third group (DH) was treated with deep whole-body hypothermia (30-33 degrees C), for 72 h. Mean arterial pH, basic excess (BE) and lactic acid in the blood were measured. Laboratory and clinical side effects of hypothermia were investigated. A conventional brain MRI was performed after the second week of life.

RESULTS

39 term asphyxiated newborns were enrolled in the study: 11 in group C, 10 in group MH, and 18 in group DH. During the first 72 h, disseminated intravascular coagulation was recorded in 2 cases (18%) in group C, pulmonary hypertension in 2 patients (20%) in group MH, and pneumonia in 3 cases (16%) in group DH. Severe cerebral lesions and poor neurological outcome were observed in 4 cases (36%) in group C, 1 case (10%) in group MH, and 1 case (5%) in group DH. A statistically significant difference in brain damage and major clinical neurological abnormalities was observed between group C and groups MH and DH, whereas no differences were demonstrated between asphyxiated infants treated with mild or deep hypothermia.

CONCLUSIONS

The results support the safety of deep hypothermia. Further studies are needed to confirm these results and the neuroprotective effect of this approach.

Bench to bedside strategies for optimizing neuroprotection following perinatal hypoxia-ischaemia in high and low resource settings

BACKGROUND

Therapeutic hypothermia gathers impetus in the developed world as a safe and effective therapy for term asphyxial encephalopathy. Although many questions still remain about the optimal application of hypothermic neuroprotection it is difficult to ignore the developing world where the prevalence of asphyxial encephalopathy is much higher. Experimental studies to optimize high tech cooling need to run in parallel with trials to determine the possible benefits of therapeutic hypothermia in low resource settings.

METHODS

We used a validated newborn piglet model of transient HI to determine (i) whether optimal neuroprotection occurs at different temperatures in the cortical and deep grey matter; (ii) the effect of body size on regional brain temperature under normothermia and hypothermia; (iii) the effect of insult severity on the therapeutic window duration; (iv) whether cooling using a water bottle is feasible. In this model hypoxia-ischaemia is induced by reversible occlusion of the common carotid arteries by remotely controlled vascular occluders and simultaneous reduction in the inspired oxygen fraction to 0.12. Intensive care can be administered to the piglet maintaining metabolic and physiological homeostasis throughout the experiment, and cerebral energy metabolism is monitored continuously providing quantitative measures of the HI insult, latent phase and secondary energy failure using phosphorus-31 ((31)P) magnetic resonance spectroscopy (MRS).

RESULTS

(i) The optimal temperature for cooling was lower in the cortex than deep grey matter. (ii) Cerebral temperatures were body-weight dependent: a smaller body weight led to a lower brain temperature especially with selective head cooling. (iii) Latent-phase duration is inversely related to insult severity. (iv) Low tech, simple cooling methods using a water bottle can induce and maintain moderate hypothermia.

CONCLUSIONS

Small shifts in brain temperature critically influence the survival of neuronal cells and body size critically influences brain-temperature gradients - smaller subjects have a larger surface area to brain volume and hence more heat is lost. The clinical implication is that smaller infants may require higher cap or body temperatures to avoid detrimental effects of over-zealous cooling. Latent-phase brevity may explain less effective neuroprotection following severe HI in some clinical studies. "Tailored" treatments which take into account individual and regional characteristics may increase the effectiveness of therapeutic hypothermia in the developed world. Low tech cooling methods using water bottles may be feasible although adequate staffing and monitoring would be required.

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 STRATEGY

The standard search strategy of the Neonatal Review Group as outlined in The Cochrane Library (Issue 2, 2007) 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 2, 2007), MEDLINE (1966 to June 2007), 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 standard care 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 review authors 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

Eight randomised controlled trials were included in this review, comprising 638 term 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 0.76 (95% CI 0.65, 0.89), typical RD -0.15 (95% CI -0.24, -0.07), NNT 7 (95% CI 4, 14)]. Cooling also resulted in statistically significant reductions in mortality [typical RR 0.74 (95% CI 0.58, 0.94), typical RD -0.09 (95% CI -0.16, -0.02), NNT 11 (95% CI 6, 50)] and in neurodevelopmental disability in survivors [typical RR 0.68 (95% CI 0.51, 0.92), typical RD -0.13 (95% CI -0.23, -0.03), NNT 8 (95% CI 4, 33)]. Some adverse effects of hypothermia included an increase in the need for inotrope support of borderline significance and a significant increase in thrombocytopaenia.

AUTHORS' CONCLUSIONS

There is evidence from the eight randomised controlled trials included in this systematic review (n = 638) that therapeutic hypothermia is beneficial to term 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. However, this review comprises an analysis based on less than half of all infants currently known to be randomised into eligible trials of cooling. Incorporation of data from ongoing and completed randomised trials (n = 829) will be important to clarify the effectiveness of cooling and to provide more information on the safety of therapeutic hypothermia, but could also alter these conclusions. Further trials to determine the appropriate method of providing therapeutic hypothermia, including comparison of whole body with selective head cooling with mild systemic hypothermia, are required.

Head cooling for neonatal encephalopathy: the state of the art

The possibility that hypothermia started during or after resuscitation at birth might reduce brain damage and cerebral palsy has tantalized clinicians for a long time. The key insight was that transient severe hypoxia-ischemia can precipitate a complex biochemical cascade leading to delayed neuronal loss. There is now strong experimental and clinical evidence that mild to moderate cooling can interrupt this cascade, and improve the number of infants surviving without disability in the medium term. The key remaining issues are to finding better ways of identifying babies who are most likely to benefit, to define the optimal mode and conditions of hypothermia and to find ways to further improve the effectiveness of treatment.

A systematic review of cooling for neuroprotection in neonates with hypoxic ischemic encephalopathy - are we there yet?

BACKGROUND

The objective of this study was to systematically review randomized trials assessing therapeutic hypothermia as a treatment for term neonates with hypoxic ischemic encephalopathy.

METHODS

The Cochrane Central Register of Controlled Trials, MEDLINE, EMBASE, CINAHL databases, reference lists of identified studies, and proceedings of the Pediatric Academic Societies were searched in July 2006. Randomized trials assessing the effect of therapeutic hypothermia by either selective head cooling or whole body cooling in term neonates were eligible for inclusion in the meta-analysis. The primary outcome was death or neurodevelopmental disability at >or= 18 months.

RESULTS

Five trials involving 552 neonates were included in the analysis. Cooling techniques and the definition and severity of neurodevelopmental disability differed between studies. Overall, there is evidence of a significant effect of therapeutic hypothermia on the primary composite outcome of death or disability (RR: 0.78, 95% CI: 0.66, 0.92, NNT: 8, 95% CI: 5, 20) as well as on the single outcomes of mortality (RR: 0.75, 95% CI: 0.59, 0.96) and neurodevelopmental disability at 18 to 22 months (RR: 0.72, 95% CI: 0.53, 0.98). Adverse effects include benign sinus bradycardia (RR: 7.42, 95% CI: 2.52, 21.87) and thrombocytopenia (RR: 1.47, 95% CI: 1.07, 2.03, NNH: 8) without deleterious consequences.

CONCLUSION

In general, therapeutic hypothermia seems to have a beneficial effect on the outcome of term neonates with moderate to severe hypoxic ischemic encephalopathy. Despite the methodological differences between trials, wide confidence intervals, and the lack of follow-up data beyond the second year of life, the consistency of the results is encouraging. Further research is necessary to minimize the uncertainty regarding efficacy and safety of any specific technique of cooling for any specific population.

Neuronal apoptosis following cerebral ischaemia: pathophysiology and possible therapeutic implications

PURPOSE OF REVIEW

Neuronal apoptosis following cerebral ischaemia has become an issue of extraordinary scientific interest in the past decade. Besides necrosis, this highly relevant pathomechanism has been shown to be markedly involved in the pathogenesis of delayed postischaemic neuronal damage. As a result, a variety of possible neuroprotective strategies and therapeutic options subsequent to cerebral ischaemia have emerged. This article provides an overview of the pathophysiologic mechanisms underlying delayed neuronal apoptotic degeneration after cerebral ischaemia. Based on these facts, selected therapeutic implications are discussed in detail.

RECENT FINDINGS

Recent findings from experimental studies have demonstrated a new therapeutic neuroprotective potential of pharmaceutical blockade of death-inducing ligands (e.g. Fas/CD95 ligand), enhancement of survival signal transduction with endogenous ligands (e.g. erythropoietin) and therapeutically modulating the balance between intracellular anti- and proapoptotic Bcl proteins with intriguing molecular techniques after cerebral ischaemia.

SUMMARY

Neuronal apoptosis is highly relevant in the pathophysiology of neurodegenerative disorders, neurotrauma and cerebral ischaemia/reperfusion. Within the past few years, a variety of therapeutic strategies have emerged based on our increasing knowledge of the pathophysiology of apoptosis. Whereas inhibition of single factors in apoptotic cascades (e.g. proteases) has produced rather unsatisfying results, new opportunities have emerged at the molecular level due to advances in molecular medicine. These approaches offer promising opportunities for neuroprotective therapeutic strategies subsequent to cerebral ischaemia. It is tempting to speculate that a combination ('cocktail') of these antiapoptotic interventions might even increase their neuroprotective potential.

Determinants of outcomes after head cooling for neonatal encephalopathy

OBJECTIVE

The goal of this study was to evaluate the role of factors that may determine the efficacy of treatment with delayed head cooling and mild systemic hypothermia for neonatal encephalopathy.

METHODS

A total of 218 term infants with moderate to severe neonatal encephalopathy plus abnormal amplitude-integrated electroencephalographic recordings, assigned randomly to head cooling for 72 hours, starting within 6 hours after birth (with the rectal temperature maintained at 34.5 +/- 0.5 degrees C), or conventional care, were studied. Death or severe disability at 18 months of age was assessed in a multicenter, randomized, controlled study (the CoolCap trial).

RESULTS

Treatment, lower encephalopathy grade, lower birth weight, greater amplitude-integrated electroencephalographic amplitude, absence of seizures, and higher Apgar score, but not gender or gestational age, were associated significantly with better outcomes. In a multivariate analysis, each of the individually predictive factors except for Apgar score remained predictive. There was a significant interaction between treatment and birth weight, categorized as > or =25th or <25th percentile for term, such that larger infants showed a lower frequency of favorable outcomes in the control group but greater improvement with cooling. For larger infants, the number needed to treat was 3.8. Pyrexia (> or =38 degrees C) in control infants was associated with adverse outcomes. Although there was a small correlation with birth weight, the adverse effect of greater birth weight in control infants remained significant after adjustment for pyrexia and severity of encephalopathy.

CONCLUSIONS

Outcomes after hypothermic treatment were strongly influenced by the severity of neonatal encephalopathy. The protective effect of hypothermia was greater in larger infants.

Targeted brain hypothermia induced by an interstitial cooling device in human neck: theoretical analyses

In this study, the feasibility of a newly developed interstitial cooling device inserted into the neck muscle and placed on the surface of the common carotid artery is evaluated. A combination of vascular model and continuum model is developed to simulate the temperature fields in both the neck and brain regions. Parametric studies are conducted to test the sensitivity of various factors on the temperature distribution. It has been shown that the length of the device, temperature of the device, and the tissue gap between the device and the blood vessel are the dominant factors that determine the effectiveness of this cooling approach. Under the current design parameters, the device is capable of inducing a temperature drop of 2.8 degrees C along the common carotid artery and it results in a total of 90 W of heat carried away from the arterial blood. Although the degree of the cooling in the arterial blood is inversely proportional to the blood flow rate of the arteries, the total heat loss from the arterial blood does not vary significantly if the blood flow rate changes during the cooling. After the cold arterial blood is supplied to the brain hemisphere, temperature reduction in the brain tissue is almost uniform and up to 3.1 degrees C temperature drop is achieved within 1 hour. In addition to the possible benefits of brain hypothermia for stroke or head injury patients, the device has the potential to control fever as well as to improve patients' outcome during open neck and head surgery.

Brief update on animal models of hypoxic-ischemic encephalopathy and neonatal stroke

The discovery of safe and effective therapies for perinatal hypoxia ischemia (HI) and stroke remains an unmet goal of neonatal-perinatal medicine. Because of the many developmental and functional differences between the neonatal brain and the adult brain, the ability to extrapolate adult data to the neonatal condition is very limited. For this reason, it is incumbent on scientists in the field of neonatal brain injury to address the questions of therapeutic efficacy of an array of potential therapies in a developmentally appropriate model. Toward that end, a number of new models of neonatal HI and stroke have been introduced recently. Additionally, some of the established models have been adapted to different species and different ages, giving scientists a greater choice of models for the study of neonatal HI and stroke. Many of these models are now also being used for functional and behavioral testing, an absolute necessity for preclinical therapeutic trials. This review focuses primarily on the newly developed models, recent adaptations to established models, and the studies of functional outcome that have been published since 2000.

Cooling produces minimal neuropathology in neocortex and hippocampus

Cooling is a potential treatment for several neurological diseases. We have examined rodent and cat neocortex, cooled to 5 and 3 degrees C, respectively, to identify a lower limit for safely cooling brain. Rat neocortex, intermittently cooled with a thermoelectric device for 2 h, showed no signs of neuronal injury after cresyl violet or TUNEL staining. Neurons were also preserved in cat cortex cooled for up to 2 h daily for 10 months. Cooled rat and cat cortex showed glial proliferation, but this was also observed in sham-operated rat cortex. When hippocampal slices from mice expressing the Green Fluorescent Protein (GFP) in neurons were cooled to 5 degrees C, but not higher temperatures, we saw reversible dendritic beading and spine loss after 15-30 min. While there may be biochemical and functional alterations in brain cooled as low as 5 degrees C, the neuropathological consequences of brain cooling appear to be insignificant.

Effects of selective brain cooling in patients with severe traumatic brain injury: a preliminary study

We prospectively investigated non-invasive selective brain cooling (SBC) in patients with severe traumatic brain injury. Sixty-six in-patients were randomized into three groups. In one group, brain temperature was maintained at 33 - 35 degrees C by cooling the head and neck (SBC); in a second group, mild systemic hypothermia (MSH; rectal temperature 33 - 35 degrees C) was produced with a cooling blanket; and a control group was not exposed to hypothermia. Natural rewarming began after 3 days. Mean intracranial pressure 24, 48 or 72 h after injury was significantly lower in the SBC group than in the control group. Mean serum superoxide dismutase levels on Days 3 and 7 after injury in the SBC and MSH groups were significantly higher than in the control group. The percentage of patients with a good neurological outcome 2 years after injury was 72.7%, 57.1% and 34.8% in the SBC, MSH and control groups, respectively. Complications were managed without severe sequelae. Non-invasive SBC was safe and effective.

Hypothermic neuroprotection

The possibility that hypothermia during or after resuscitation from asphyxia at birth, or cardiac arrest in adults, might reduce evolving damage has tantalized clinicians for a very long time. It is now known that severe hypoxia-ischemia may not necessarily cause immediate cell death, but can precipitate a complex biochemical cascade leading to the delayed neuronal loss. Clinically and experimentally, the key phases of injury include a latent phase after reperfusion, with initial recovery of cerebral energy metabolism but EEG suppression, followed by a secondary phase characterized by accumulation of cytotoxins, seizures, cytotoxic edema, and failure of cerebral oxidative metabolism starting 6 to 15 h post insult. Although many of the secondary processes can be injurious, they appear to be primarily epiphenomena of the 'execution' phase of cell death. Studies designed around this conceptual framework have shown that moderate cerebral hypothermia initiated as early as possible before the onset of secondary deterioration, and continued for a sufficient duration in relation to the severity of the cerebral injury, has been associated with potent, long-lasting neuroprotection in both adult and perinatal species. Two large controlled trials, one of head cooling with mild hypothermia, and one of moderate whole body cooling have demonstrated that post resuscitation cooling is generally safe in intensive care, and reduces death or disability at 18 months of age after neonatal encephalopathy. These studies, however, show that only a subset of babies seemed to benefit. The challenge for the future is to find ways of improving the effectiveness of treatment.

The International Liaison Committee on Resuscitation (ILCOR) consensus on science with treatment recommendations for pediatric and neonatal patients: pediatric basic and advanced life support

This publication contains the pediatric and neonatal sections of the 2005 International Consensus on Cardiopulmonary Resuscitation and Emergency Cardiovascular Care Science With Treatment Recommendations (COSTR). The consensus process that produced this document was sponsored by the International Liaison Committee on Resuscitation (ILCOR). ILCOR was formed in 1993 and consists of representatives of resuscitation councils from all over the world. Its mission is to identify and review international science and knowledge relevant to cardiopulmonary resuscitation (CPR) and emergency cardiovascular care (ECC) and to generate consensus on treatment recommendations. ECC includes all responses necessary to treat life-threatening cardiovascular and respiratory events. The COSTR document presents international consensus statements on the science of resuscitation. ILCOR member organizations are each publishing resuscitation guidelines that are consistent with the science in this consensus document, but they also take into consideration geographic, economic, and system differences in practice and the regional availability of medical devices and drugs. The American Heart Association (AHA) pediatric and the American Academy of Pediatrics/AHA neonatal sections of the resuscitation guidelines are reprinted in this issue of Pediatrics (see pages e978-e988). The 2005 evidence evaluation process began shortly after publication of the 2000 International Guidelines for CPR and ECC. The process included topic identification, expert topic review, discussion and debate at 6 international meetings, further review, and debate within ILCOR member organizations and ultimate approval by the member organizations, an Editorial Board, and peer reviewers. The complete COSTR document was published simultaneously in Circulation (International Liaison Committee on Resuscitation. 2005 International Consensus on Cardiopulmonary Resuscitation and Emergency Cardiovascular Care Science With Treatment Recommendations. Circulation. 2005;112(suppl):73-90) and Resuscitation (International Liaison Committee on Resuscitation. 2005 International Consensus Conference on Cardiopulmonary Resuscitation and Emergency Cardiovascular Care Science With Treatment Recommendations. Resuscitation. 2005;67:271-291). Readers are encouraged to review the 2005 COSTR document in its entirety. It can be accessed through the CPR and ECC link at the AHA Web site: www.americanheart.org. The complete publication represents the largest evaluation of resuscitation literature ever published and contains electronic links to more detailed information about the international collaborative process. To organize the evidence evaluation, ILCOR representatives established 6 task forces: basic life support, advanced life support, acute coronary syndromes, pediatric life support, neonatal life support, and an interdisciplinary task force to consider overlapping topics such as educational issues. The AHA established additional task forces on stroke and, in collaboration with the American Red Cross, a task force on first aid. Each task force identified topics requiring evaluation and appointed international experts to review them. A detailed worksheet template was created to help the experts document their literature review, evaluate studies, determine levels of evidence, develop treatment recommendations, and disclose conflicts of interest. Two evidence evaluation experts reviewed all worksheets and assisted the worksheet reviewers to ensure that the worksheets met a consistently high standard. A total of 281 experts completed 403 worksheets on 275 topics, reviewing more than 22000 published studies. In December 2004 the evidence review and summary portions of the evidence evaluation worksheets, with worksheet author conflict of interest statements, were posted on the Internet at www.C2005.org, where readers can continue to access them. Journal advertisements and e-mails invited public comment. Two hundred forty-nine worksheet authors (141 from the United States and 108 from 17 other countries) and additional invited experts and reviewers attended the 2005 International Consensus Conference for presentation, discussion, and debate of the evidence. All 380 participants at the conference received electronic copies of the worksheets. Internet access was available to all conference participants during the conference to facilitate real-time verification of the literature. Expert reviewers presented topics in plenary, concurrent, and poster conference sessions with strict adherence to a novel and rigorous conflict of interest process. Presenters and participants then debated the evidence, conclusions, and draft summary statements. Wording of science statements and treatment recommendations was refined after further review by ILCOR member organizations and the international editorial board. This format ensured that the final document represented a truly international consensus process. The COSTR manuscript was ultimately approved by all ILCOR member organizations and by an international editorial board. The AHA Science Advisory and Coordinating Committee and the editor of Circulation obtained peer reviews of this document before it was accepted for publication. The most important changes in recommendations for pediatric resuscitation since the last ILCOR review in 2000 include: Increased emphasis on performing high quality CPR: "Push hard, push fast, minimize interruptions of chest compression; allow full chest recoil, and don't provide excessive ventilation" Recommended chest compression-ventilation ratio: For lone rescuers with victims of all ages: 30:2 For health care providers performing 2-rescuer CPR for infants and children: 15:2 (except 3:1 for neonates) Either a 2- or 1-hand technique is acceptable for chest compressions in children Use of 1 shock followed by immediate CPR is recommended for each defibrillation attempt, instead of 3 stacked shocks Biphasic shocks with an automated external defibrillator (AED) are acceptable for children 1 year of age. Attenuated shocks using child cables or activation of a key or switch are recommended in children <8 years old. Routine use of high-dose intravenous (IV) epinephrine is no longer recommended. Intravascular (IV and intraosseous) route of drug administration is preferred to the endotracheal route. Cuffed endotracheal tubes can be used in infants and children provided correct tube size and cuff inflation pressure are used. Exhaled CO2 detection is recommended for confirmation of endotracheal tube placement. Consider induced hypothermia for 12 to 24 hours in patients who remain comatose following resuscitation. Some of the most important changes in recommendations for neonatal resuscitation since the last ILCOR review in 2000 include less emphasis on using 100% oxygen when initiating resuscitation, de-emphasis of the need for routine intrapartum oropharyngeal and nasopharyngeal suctioning for infants born to mothers with meconium staining of amniotic fluid, proven value of occlusive wrapping of very low birth weight infants <28 weeks' gestation to reduce heat loss, preference for the IV versus the endotracheal route for epinephrine, and an increased emphasis on parental autonomy at the threshold of viability. The scientific evidence supporting these recommendations is summarized in the neonatal document (see pages e978-e988).

Therapeutic hypothermia for stroke: do new outfits change an old friend?

Clinically significant neuroprotection for the brain continues to be an elusive quest. All attempts at developing effective pharmacologic agents have failed in clinical trials. Hypothermia has been thought to confer protection after brain injury for many years, but has recently regained interest as a neuroprotectant for focal ischemic stroke in the basic science and clinical literature. The failure to develop safe and efficacious pharmacologic agents along with promising clinical data on the efficacy of hypothermia for cardiac arrest patients have raised a great interest in hypothermia as a neuroprotectant for ischemic stroke. As a clinically meaningful neuroprotectant for stroke, hypothermia confers several theoretical advantages over pharmacologic agents. A major problem with neuroprotectant therapy is instituting therapy within a narrow time window. This obstacle may be easier for hypothermia to overcome as emergency medical service personnel can theoretically initiate it in the field. Additionally, pharmacologic agents are usually restricted to one aspect of the pathophysiologic cascade triggered by focal ischemia, whereas hypothermia acts on several of these pathways simultaneously. The recent advances and future directions in the utilization of hypothermia as a potential therapy for focal ischemic stroke are reviewed.

Brain injury in the infant: the old, the new, and the uncertain

Although neonatal brain injury occurs most frequently after a perinatal hypoxic-ischemic insult, recently studies have noted that variable causes such as metabolic and reperfusion events can result in, or aggravate, a brain insult. Current data suggest that about 2 to 5 of 1,000 live births in the United States and more so in developing countries experience a brain injury Approximately 20% to 40% of infants who survive the brain injury develop significant neurological and developmental impairments. The resulting impact on the child, family, and society presents a formidable challenge to health care professionals. Although several important insights have been gained in the last several years about the epidemiology, diagnosis, and mechanism of brain injury, management remains mostly a cocktail of controversial trials. This article provides a comprehensive review of the pathology, clinical manifestations, and timely management of infants with brain injury.

Hemodynamics among neonates with hypoxic-ischemic encephalopathy during whole-body hypothermia and passive rewarming

OBJECTIVE

To assess changes in cardiac performance, with Doppler echocardiography, among newborns with hypoxic-ischemic encephalopathy during mild therapeutic hypothermia and during rewarming.

METHODS

For 7 asphyxiated neonates (birth weight: 1840-3850 g; umbilical artery pH: 6.70-6.95) who received mild whole-body hypothermia, the following hemodynamic parameters were determined immediately before rewarming (33 degrees C) and during passive rewarming (35 degrees C and 37 degrees C): heart rate, systolic and diastolic blood pressure, core and peripheral temperatures, left ventricular ejection time, mean velocity of aortic flow, stroke volume, and cardiac output.

RESULTS

Heart rate decreased during hypothermia. Bradycardia, with heart rates below 80 beats per minute, did not occur. The median difference between core and peripheral temperatures decreased from 2.0 degrees C (range: 0-6.2 degrees C) during hypothermia to 0.7 degrees C (range: 0.4-1.9 degrees C) at normothermia. Cardiac output was reduced to 67% and stroke volume to 77% of the posthypothermic level. The median heart rate was 129 beats per minute before rewarming and increased to 148 beats per minute during complete rewarming. Before and during passive rewarming, hypotension was not observed. Before, during, and at the end of rewarming, the following parameters increased: mean velocity of aortic flow (median: 44, 55, and 58 cm/second, respectively), stroke volume (median: 1.42, 1.55, and 1.94 mL/kg, respectively), and cardiac output (median: 169, 216, and 254 mL/kg per minute, respectively). Left ventricular ejection time remained unchanged.

CONCLUSIONS

Whole-body hypothermia resulted in reduced cardiac output, which reached normal levels at the end of passive rewarming, at normothermia. Physiologic cardiovascular mechanisms seemed to be intact to provide sufficient tissue perfusion, with normal blood lactate levels.

Therapeutic hypothermia following perinatal asphyxia

Well constructed and carefully analysed trials of hypothermic neural rescue therapy for infants with neonatal encephalopathy have recently been reported. The data suggest that either selective head cooling or total body cooling reduces the combined chance of death or disability after birth asphyxia. However, as there are still unanswered questions about these treatments, many may still feel that further data are needed before health care policy can be changed to make cooling the standard of care for all babies with suspected birth asphyxia.

Modest hypothermia as a neuroprotective strategy in high-risk term infants

This article briefly reviews the pathogenesis of hypoxic-ischemic cerebral injury, the experimental data, and clinical studies that have evaluated the potential therapeutic benefit of modest selective or whole body hypothermia in reducing the subsequent development of irreversible brain injury without untoward side effects. Data are insufficient to recommend routine use of either modest selective or whole body hypothermia after resuscitation of infants with suspected asphyxia. Further clinical trials are needed to determine which infants would benefit most and which method of cooling would be most effective.

Mild hypothermia via selective head cooling as neuroprotective therapy in term neonates with perinatal asphyxia: an experience from a single neonatal intensive care unit

OBJECTIVE

The objective of this study was to determine the efficacy of mild hypothermia via selective head cooling as a neuroprotective therapy in term infants with perinatal asphyxia.

STUDY DESIGN

Full-term newborns who had 5 min Apgar scores <6, first arterial blood gas pH<7.10 or BD>15 mEq/l, and with the clinical signs of encephalopathy were enrolled within 6 h after birth. Patients were randomized to receive mild hypothermia treatment via selective head cooling for a total of 72 h or receive routine treatment as a control. Brain hypoxic-ischemic injury was quantified based on the head computed tomographic scan (CT scan) at postnatal age 5-7 days and a Neonatal Behavioral Neurological Assessment (NBNA) score at 7-10 days of life.

RESULTS

A total of 58 patients (30 hypothermia, 28 control) completed the study. Hypothermia was well tolerated in this study and attenuated the hypoxic-ischemic brain injury due to perinatal asphyxia. Head CT scan demonstrated moderate to severe hypoxic-ischemic changes in only 4/30 cases from the hypothermic group. In contrast, 18/28 cases in the control group showed moderate to severe hypoxic-ischemic changes (chi (2)=15.97, P<0.01). Brain hypothermia also significantly improved the NBNA score (32+/-2 in the hypothermic group vs 28+/-3 in the control group, P<0.01).

CONCLUSIONS

Our results suggest that selective head cooling may be used as a neuroprotective therapy in term neonates with perinatal asphyxia. A long-term follow-up study is needed to further validate the results of this study.