Cold Injury Syndrome and Neurodevelopmental Changes in Survivors

Delayed Rewarming Thrombocytopenia: A Suggested Preventable and Treatable Cause of Rewarming Deaths

The lack of a consensus of accepted prognostic factors in hypothermia suggests an additional factor has been overlooked. Delayed rewarming thrombocytopenia (DRT) is a novel candidate for such a role. At body temperature, platelets undergoing a first stage of aggregation are capable of progression to a second irreversible stage of aggregation. However, we have shown that the second stage of aggregation does not occur below 32°C and that this causes the first stage to become augmented (first-stage platelet hyperaggregation). In aggregometer studies performed below 32°C, the use of quantities of ADP that cause a marked first-stage hyperaggregation can cause an augmented second-stage activation of the platelets during rewarming (second-stage platelet hyperaggregation). In vivo, after 24 hours of hypothermia, platelets on rewarming seem to undergo second-stage hyperaggregation, from ADP released from erythrocytes, leading to life-threatening thrombocytopenia. This hyperaggregation is avoidable if heparin is given before the hypothermia or if aspirin, alcohol or platelet transfusion is given during the hypothermia before reaching 32°C on rewarming. Many of the open questions existing in this field are explained by DRT. Prevention and treatment of DRT could be of significant value in preventing rewarming deaths and some cases of rescue collapse. Performing platelet counts during rewarming will demonstrate potentially fatal thrombocytopenia and enable treatment with platelet infusions aspirin or alcohol.

Unrecognized platelet physiology is the cause of rewarming deaths in accidental hypothermia and neonatal cold injury

BACKGROUND

The lack of improvement in prognosis of accidental hypothermia and neonatal cold injury suggests that a major cause of mortality has not been appreciated.

AIM OF THE ARTICLE

To show that thrombocytopenia that deepens on rewarming under certain conditions is that missing factor.

SCIENTIFIC BASIS

Below 34 °C the first stage of aggregation is accentuated, the platelets are more sensitive to ADP and aggregation studies show an increased response "first stage hyper aggregation". We have confirmed that the irreversible second stage of platelet aggregation does not occur below 34 °C. On rewarming, the first stage of aggregation is followed by disaggregation. When platelets are warmed to 34 °C the potential exists for the platelets to undergo an irreversible second stage of aggregation "second stage platelet hyper aggregation" that can cause a further drop in platelet count and a bleeding diathesis. This only occurs if the platelets have been sufficiently primed when cold and may not be appreciated if platelet counts are not followed.

SIGNIFICANCE OF THIS DATA AND CORRELATION WITH THE LITERATURE

This thesis explains many other open questions. Why has the overall prognosis remained without improvement over the last half century? Why hypothermic cardiac surgery is free of this problem? Why the depth of hypothermia is alone not prognostic? Has following platelet counts been associated with improved prognosis? Why cardiac arrest does not affect prognosis? Why some patients die suddenly after recovering from hypothermia? Why are so many different rewarming techniques used? Why is the prognosis better in hypothermic suicide attempts? What is the pathophysiological explanation for reversible sequestration of platelets to the liver and spleen in hypothermia? Is DIC (diffuse intravascular coagulation) a problem in hypothermia? And how this new approach could improve prognosis?

CONCLUSION

Prognosis can be improved by following platelet counts during rewarming. In patients with prolonged hypothermia, this will show a life-threatening drop in such counts easily treated by platelet infusion.

Impact of Education on Hypothermia Delivery during Neonatal Transport

BACKGROUND

Moderate therapeutic hypothermia (TH) initiated within 6 h of life reduces adverse neurodevelopmental outcomes in infants after perinatal hypoxic ischaemic insult. For infants born in non-tertiary centres, TH may be initiated manually en route to a neonatal intensive care unit (NICU). However, both over- and undercooling is reported with this strategy, precluding some infants from the benefits of TH.

OBJECTIVES

To evaluate the impact of a region-wide educational programme on the safety and efficacy of manual cooling administered by the Wellington Neonatal Transport Service (NeTS).

METHODS

Clinical records of infants with hypoxic ischaemic encephalopathy (HIE) retrieved by the Wellington NeTS for TH between January 2012 and June 2017 were reviewed retrospectively. Temperature outcomes of infants retrieved before and after the education programme were compared.

RESULTS

A total of 101 infants were cooled manually by Wellington NeTS for TH during the study period. Education and training significantly reduced the rate of overcooling to ≤32.0°C (4/43 [9%] vs. 0/58, p = 0.02). However, there was no difference in the proportion of infants who achieved target rectal temperature within 6 h of life (29/43 [65%] vs. 35/58 [60%], p = 0.57).

CONCLUSIONS

Introduction of a region-wide educational programme may have improved the safety of manual cooling during neonatal transport but it had a negligible impact on its efficacy. The use of servo-controlled cooling during transport should therefore be considered to improve access to the optimal neuroprotective benefits of TH for outborn infants with HIE.

Efficacy of Selective Brain Cooling Using a Nasopharyngeal Method in Piglets

BACKGROUND

Mild hypothermia is an effective neuroprotective strategy for a variety of acute brain injuries. Cooling the nasopharynx may offer the capability to cool the brain selectively due to anatomic proximity of the internal carotid artery to the cavernous sinus. This study investigated the feasibility and efficiency of nasopharyngeal brain cooling by continuously blowing room temperature or cold air at different flow rates into the nostrils of normal newborn piglets.

METHODS

Experiments were conducted on thirty piglets (n = 30, weight = 2.7 ± 1.5 kg). Piglets were anesthetized with 1–2% isoflurane and were randomized to receive one of four different nasopharyngeal cooling treatments: I. Room temperature at a flow rate of 3–4 L min(−1) (n = 6); II. −1 ± 2 °C at a flow rate of 3–4 L min(−1) (n = 6); III. Room temperature at a flow rate of 14–15 L min(−1) (n = 6); IV. −8 ± 2 °C at a flow rate of 14–15 L min(−1) (n = 6). To control for the normal thermal regulatory response of piglets without nasopharyngeal cooling, a control group of piglets (n = 6) had their brain temperature monitored without nasopharyngeal cooling. The duration of treatment was 60 min, with additional 30 min of observation.

RESULTS

In group I, median cooling rate was 1.7 ± 0.9 °C/h by setting the flow rate of room temperature air to 3–4 L min(−1). Results of comparing different temperatures and flow rates in the nasopharyngeal cooling approach reveal that the brain temperature could be reduced rapidly at a rate of 5.5 ± 1.1 °C/h by blowing −8 ± 2 °C air at a flow rate of 14–15 L min(−1).

CONCLUSIONS

Nasopharyngeal cooling via cooled insufflated air can lower the brain temperature, with higher flows and lower temperatures of insufflated air being more effective.

A new approach to selective brain cooling by a Ranque-Hilsch vortex tube

Background

Target temperature management is the single most effective intervention and the gold standard in post-resuscitation care today. However, cooling the whole body below 33–34 °C can cause severe complications. Therefore, developing a selective brain cooling (SBC) approach which can be initiated early to induce rapid cooling and maintain the target temperature over 12–24 h before slowly rewarming brain temperature by itself alone would be advantageous. Vortex tubes are simple mechanical devices generating cold air from a stream of compressed air without applied chemical or energy. This study investigated whether blowing cooled air from a vortex tube into the nasal cavities is safe and effective to selectively reduce and maintain before slowly rewarming brain temperature back to normal temperature.

Methods

Experiments were conducted on ten juvenile pigs. Body temperature was measured using an esophageal and a rectal temperature probe while brain temperature with an intraparenchymal thermocouple probe. Cerebral blood flow (CBF) was measured with CT perfusion.

Results

Brain temperature dropped below 34 °C within 30–40 min while a brain-esophageal temperature difference greater than 3 °C was maintained over 6 h. There was no evidence of nasal or nasopharynx mucosal swelling, necrosis, or hemorrhage on MRI examination. CBF first decreased and then stabilized together with brain temperature before increasing to the baseline level during rewarming.

Conclusions

SBC was accomplished by blowing cold air from a vortex tube into the nasal cavities. Due to its portability, the method can be used continuously in resuscitated patients in both in- and out-of-hospital situations without interruption.

Rapid and selective brain cooling method using vortex tube: A feasibility study

Vortex tubes are simple mechanical devices to produce cold air from a stream of compressed air without any moving parts. The primary focus of the current study is to investigate the feasibility and efficiency of nasopharyngeal brain cooling method using a vortex tube. Experiments were conducted on 5 juvenile pigs. Nasopharygeal brain cooling was achieved by directing cooled air via a catheter in each nostril into the nasal cavities. A vortex tube was used to generate cold air using various sources of compressed air: (I) hospital medical air outlet (n = 1); (II) medical air cylinders (n = 3); and (III) scuba (diving) cylinders (n = 1). By using compressed air from a hospital medical air outlet at fixed inlet pressure of 50 PSI, maximum brain-rectal temperature gradient of -2°C was reached about 45-60 minutes by setting the flow rate of 25 L/min and temperature of -7°C at the cold air outlet. Similarly, by using medical air cylinders at fill-pressure of 2265 PSI and down regulate the inlet pressure to the vortex tube to 50 PSI, brain temperature could be reduced more rapidly by blowing -22°C ± 2°C air at a flow rate of 50 L/min; brain-body temperature gradient of -8°C was obtained about 30 minutes. Furthermore, we examined scuba cylinders as a portable source of compressed gas supply to the vortex tube. Likewise, by setting up the vortex tube to have an inlet pressure of 25 PSI and 50 L/min and -3°C at the cold air outlet, brain temperature decreased 4.5°C within 10-20 min.

Susceptibility of rat hippocampal neurons to hypothermia during development

Purpose

This study evaluated the extent of damage due to hypothermia in the mature and immature brain.

Methods

Hippocampal tissue cultures at 7 and 14 days in vitro (DIV) were used to represent the immature and mature brain, respectively. The cultures were exposed at 25℃ for 0, 10, 30, and 60 minutes (n=30 in each subgroup). Propidium iodide fluorescent images were captured 24 and 48 hours after hypothermic injury. Damaged areas of the cornu ammonis 1 (CA1), CA3, and dentate gyrus (DG) were measured using image analysis.

Results

At 7 DIV, the tissues exposed to cold injury for 60 minutes showed increased damage in CA1 (P<0.001) and CA3 (P=0.005) compared to the control group at 48 hours. Increased damage to DG was observed at 24 (P=0.008) and 48 hours (P=0.011). The 14 DIV tissues did not demonstrate any significant differences compared with the control group, except for the tissues exposed for 30 minutes in which DG showed less damage at 48 hours than the control group (P=0.048). In tissues at 7 DIV, CA1 (P=0.040) and DG (P=0.013) showed differences in the duration of cold exposure.

Conclusion

The immature brain is more vulnerable to hypothermic injury than the mature brain.

The Cultural Meaning of Children Sleeping Outdoors in Finnish Winter

Purpose: Little is known about children sleeping outdoors in a northern winter climate, although it is a common practice in northern countries. The article describes the cultural meaning of this child care practice from the viewpoint of mothers. Design: Explorative descriptive study design was adopted and unstructured interviews were processed by qualitative content analysis. Participants: Twenty-one mothers of families in northern Finland participated. Results: Family, cultural outdoor sleeping practice and northern winter environment constituted compatibility, which consisted of four generic categories: strengthening family well-being through outdoor sleeping, taking notice of security perspectives, adaptation to the northern winter environment, and cultural knowledge-building processes. Conclusions: Family well-being was strengthened through outdoor sleeping of children when all security perspectives were first taken into account. Families were adapted to the northern winter environment and cultural knowledge was built. A fit was found between families, cultural child care practice, and northern winter environment constituting a coherent whole.

Lessons learned during implementation of therapeutic hypothermia for neonatal hypoxic ischemic encephalopathy in a regional transport program in Ontario

BACKGROUND

Therapeutic hypothermia (TH) is the first intervention to consistently show improved neurological outcomes in neonates with hypoxic ischemic encephalopathy (HIE). Since the recent introduction of TH for HIE in many centres, reviews of practices during the implementation of TH in Canada have not been published.

OBJECTIVE

To determine if eligible neonates are being offered TH and to identify any barriers to the effective implementation of TH.

METHODS

A retrospective review of neonates referred to a regional tertiary centre at a gestational age of 35 weeks or more with HIE was conducted.

RESULTS

Among 41 neonates referred, 29 (71%) were eligible for TH; among eligible patients, five were moribund and excluded, and TH was initiated in 16 (67%) of the remaining 24. Reasons for not cooling in eight eligible patients included a delay in referral (n=5, median age at referral was 14 h) and a failure to recognize the severity of HIE (n=3). Among cooled patients, median times were the following: 116 min for age at referral; 80 min for time from referral to transport team arrival; and 358 min for age at initiation of cooling. Seven (44%) patients had cooling initiated after 6 h of age.

CONCLUSION

A significant proportion of eligible patients were not offered TH, and in many cooled patients, initiation of cooling was delayed beyond the recommended 6 h. For eligible patients to benefit from TH, it is imperative that all birthing centres be made aware that TH is now widely available as an important treatment option, but also that TH is a time-sensitive therapy requiring rapid identification and referral. In the region studied, for eligible patients, referring hospitals should initiate passive cooling before arrival of the transport team. Referring hospitals should be prepared to provide early, yet safe initiation of passive cooling by having the appropriate equipment, and having staff trained in the use and monitoring of rectal temperatures.

Systemic complications and hypothermia

Cooling for neonatal hypoxic-ischemic encephalopathy is a novel and promising neuroprotective therapy that requires significant understanding of how cooling affects all organ systems and interventions used to treat systemic complications of cooling in an intensive care setting. As cooling is used more widely and has been newly introduced in neonatal units, continued surveillance of its use in clinical practice is mandatory. Units offering cooling should strongly consider joining a registry (e.g. the Vermont-Oxford Neonatal Encephalopathy Registry in the USA or the TOBY Register in the UK) that facilitates benchmarking of short-term adverse effects and long-term outcomes of cooling and that supports local quality improvement efforts.

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.

A brief indicator of household energy security: associations with food security, child health, and child development in US infants and toddlers

OBJECTIVE

Household energy security has not been measured empirically or related to child health and development but is an emerging concern for clinicians and researchers as energy costs increase. The objectives of this study were to develop a clinical indicator of household energy security and assess associations with food security, health, and developmental risk in children <36 months of age.

METHODS

A cross-sectional study that used household survey and surveillance data was conducted. Caregivers were interviewed in emergency departments and primary care clinics form January 2001 through December 2006 on demographics, public assistance, food security, experience with heating/cooling and utilities, Parents Evaluation of Developmental Status, and child health. The household energy security indicator includes energy-secure, no energy problems; moderate energy insecurity, utility shutoff threatened in past year; and severe energy insecurity, heated with cooking stove, utility shutoff, or >or=1 day without heat/cooling in past year. The main outcome measures were household and child food security, child reported health status, Parents Evaluation of Developmental Status concerns, and hospitalizations.

RESULTS

Of 9721 children, 11% (n = 1043) and 23% (n = 2293) experienced moderate and severe energy insecurity, respectively. Versus children with energy security, children with moderate energy insecurity had greater odds of household food insecurity, child food insecurity, hospitalization since birth, and caregiver report of child fair/poor health, adjusted for research site and mother, child, and household characteristics. Children with severe energy insecurity had greater adjusted odds of household food insecurity, child food insecurity, caregivers reporting significant developmental concerns on the Parents Evaluation of Developmental Status scale, and report of child fair/poor health. No significant association was found between energy security and child weight for age or weight for length.

CONCLUSIONS

As household energy insecurity increases, infants and toddlers experienced increased odds of household and child food insecurity and of reported poor health, hospitalizations, and developmental risks.

A prediction score model for risk factors of mortality in neonate with pulmonary hemorrhage: the experience of single neonatal intensive care unit in Southwest China

AIM

To establish a prediction score model for mortality of neonates with pulmonary hemorrhage (PH).

METHODS

Mortality risk factors of PH were analyzed by logistic regression analysis in 244 neonates retrospectively. A prediction score model was developed according to regression coefficients of risk factors. The receiver operating characteristic curve (ROC) was also constructed and the cutoff was determined.

RESULTS

The overall mortality rate of PH was 74.59% (182/244). More patients from multiple pregnancies were found in the death group than in the survivor group (20.1% vs. 3.2%, P = 0.023). The survivor group infants had higher birth weight in average than death group infants (2,787 g vs. 2,339 g, P = 0.000). Significant differences were found between survivor and death groups in the rates of intraventricular hemorrhage (IVH) (25.8% vs. 53.8%, P = 0.000), heart failure (22.6% vs. 48.9%, P = 0.000) and sepsis (3.2% vs. 16.5%, P = 0.008). Birth weight, IVH, heart failure and sepsis were identified as independent mortality risk factors by logistic regression analysis. A score model predicting death was developed according to the regression coefficients, with a sensitivity of 0.846, a specificity of 0.661, a positive predictive value of 0.88 and a negative predictive value of 0.594 at a cutoff of 9 points. The low risk group, with a score of 9 or less, had a lower mortality rate as compared with the high risk group (40.6% vs. 88%, P = 0.000).

CONCLUSIONS

Low birth weight, IVH, heart failure and sepsis were the risk factors for mortality of PH. Those infants with a predictive score of more than 9 were at high risk for death.