Vecuronium pharmacokinetics and pharmacodynamics during hypothermic cardiopulmonary bypass in infants and children

On-Site Medical Management of Avalanche Victims-A Narrative Review

Avalanche accidents are common in mountain regions and approximately 100 fatalities are counted in Europe each year. The average mortality rate is about 25% and survival chances are mainly determined by the degree and duration of avalanche burial, the patency of the airway, the presence of an air pocket, snow characteristics, and the severity of traumatic injuries. The most common cause of death in completely buried avalanche victims is asphyxia followed by trauma. Hypothermia accounts for a minority of deaths; however, hypothermic cardiac arrest has a favorable prognosis and prolonged resuscitation and extracorporeal rewarming are indicated. In this article, we give an overview on the pathophysiology and on-site management of avalanche victims.

Accidental hypothermia-an update : The content of this review is endorsed by the International Commission for Mountain Emergency Medicine (ICAR MEDCOM)

BACKGROUND

This paper provides an up-to-date review of the management and outcome of accidental hypothermia patients with and without cardiac arrest.

METHODS

The authors reviewed the relevant literature in their specialist field. Summaries were merged, discussed and approved to produce this narrative review.

RESULTS

The hospital use of minimally-invasive rewarming for non-arrested, otherwise healthy, patients with primary hypothermia and stable vital signs has the potential to substantially decrease morbidity and mortality for these patients. Extracorporeal life support (ECLS) has revolutionised the management of hypothermic cardiac arrest, with survival rates approaching 100 % in some cases. Hypothermic patients with risk factors for imminent cardiac arrest (temperature <28 °C, ventricular arrhythmia, systolic blood pressure <90 mmHg), and those who have already arrested, should be transferred directly to an ECLS-centre. Cardiac arrest patients should receive continuous cardiopulmonary resuscitation (CPR) during transfer. If prolonged transport is required or terrain is difficult, mechanical CPR can be helpful. Delayed or intermittent CPR may be appropriate in hypothermic arrest when continuous CPR is impossible. Modern post-resuscitation care should be implemented following hypothermic arrest. Structured protocols should be in place to optimise pre-hospital triage, transport and treatment as well as in-hospital management, including detailed criteria and protocols for the use of ECLS and post-resuscitation care.

CONCLUSIONS

Based on new evidence, additional clinical experience and clearer management guidelines and documentation, the treatment of accidental hypothermia has been refined. ECLS has substantially improved survival and is the treatment of choice in the patient with unstable circulation or cardiac arrest.

Management of neonatal morbidities during hypothermia treatment

Although the primary goal of therapeutic hypothermia is to improve the neurodevelopmental outcome in asphyxiated infants, optimal management of the full range of multi-organ system complications typically presented by such infants during cooling treatment is necessary for improvement of the overall outcome. For this reason, adequate knowledge of how cooling affects all organ systems of asphyxiated infants with multi-organ hypoxic-ischemic injury is essential. Adequate diagnostic resources, readily available subspecialty consultant services and trained multidisciplinary staff to monitor and manage multi-organ system complications in asphyxiated infants during therapeutic cooling must be ensured during implementation of a cooling program. As therapeutic hypothermia is being used more widely, centers should consider participation in national or international benchmarking of outcomes and short-term adverse events during cooling to facilitate continuous quality improvement efforts.

The impact of extracorporeal life support and hypothermia on drug disposition in critically ill infants and children

Extracorporeal membrane oxygenation (ECMO) support is an established lifesaving therapy for potentially reversible respiratory or cardiac failure. In 10% of all pediatric patients receiving ECMO, ECMO therapy is initiated during or after cardiopulmonary resuscitation. Therapeutic hypothermia is frequently used in children after cardiac arrest, despite the lack of randomized controlled trials that show its efficacy. Hypothermia is frequently used in children and neonates during cardiopulmonary bypass (CPB). By combining data from pharmacokinetic studies in children on ECMO and CPB and during hypothermia, this review elucidates the possible effects of hypothermia during ECMO on drug disposition.

[Neuroprotection with hypothermia in the newborn with hypoxic-ischaemic encephalopathy. Standard guidelines for its clinical application]

Standardisation of hypothermia as a treatment for perinatal hypoxic-ischaemic encephalopathy is supported by current scientific evidence. The following document was prepared by the authors on request of the Spanish Society of Neonatology and is intended to be a guide for the proper implementation of this therapy. We discuss the difficulties that may arise when moving from the strict framework of clinical trials to clinical daily care: early recognition of clinical encephalopathy, inclusion and exclusion criteria, hypothermia during transport, type of hypothermia (selective head or systemic cooling) and side effects of therapy. The availability of hypothermia therapy has changed the prognosis of children with hypoxic-ischaemic encephalopathy and our choices of therapeutic support. In this sense, it is especially important to be aware of the changes in the predictive value of the neurological examination and the electroencephalographic recording in cooled infants. In order to improve neuroprotection with hypothermia we need earlier recognition of to recognise earlier the infants that may benefit from cooling. Biomarkers of brain injury could help us in the selection of these patients. Every single infant treated with hypothermia must be included in a follow up program in order to assess neurodevelopmental outcome.

Cisatracurium pharmacokinetics and pharmacodynamics during hypothermic cardiopulmonary bypass in infants and children

BACKGROUND

Hypothermia potentiates neuromuscular blockade in adults during cardiopulmonary bypass (CPB) but the pediatric literature is sparse. Temperature-dependent Hoffman degradation of cisatracurium may allow reduction in infusion rate (IR) during hypothermia. The effect of hypothermic CPB on the pharmacokinetics (PK) and pharmacodynamics (PD) of cisatracurium has not been described in children.

METHODS AND MATERIALS

Using neuromuscular monitoring with a Datex Relaxograph, cisatracurium IR was adjusted to obtain a pseudo-steady state during each phase of surgery (pre-CPB, CPB, post-CPB). Paired samples were taken at each phase. Cisatracurium plasma concentrations (Cpss) were determined by HPLC. Core and skin temperatures were recorded.

RESULTS

Data from ten infants were analyzed: Group 1: mean 33.6°C; Group 2: mean 21.9°C. To maintain T1% between 5% and 10% in Group 2, the IR was decreased by a mean of 89% (P < 0.001). IR was not significantly different in Group 1. Post-CPB IR approximated pre-CPB rates in both groups. During CPB, Cpss fell by 27% in Group 1 and by 50% in Group 2 (P = 0.039). Post-CPB Cpss was not significantly different to pre-CPB in either group. Clearance did not change significantly in Group 1 but fell significantly in Group 2 during CPB (P = 0.002). Clearance post-CPB was unchanged from pre-CPB.

CONCLUSIONS

Cisatracurium IR may be decreased by around 60% during CPB with moderate hypothermia but can be maintained at baseline during mild hypothermia.

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.

Serum gentamicin concentrations in encephalopathic infants are not affected by therapeutic hypothermia

OBJECTIVE

Mild hypothermia for 72 hours is neuroprotective in newborns with moderate or severe hypoxic-ischemic encephalopathy. A core temperature of 33.5 degrees C might reduce drug clearance leading to potential toxicity. Gentamicin is nephrotoxic and ototoxic at high serum concentrations. No study has investigated the influence of 72 hours of hypothermia on serum gentamicin concentrations (SGCs) in children of any age. We aimed to compare the SGCs in encephalopathic infants who underwent intensive care with therapeutic hypothermia or normothermia.

METHODS

Data were collected retrospectively from 2 NICUs in Bristol, United Kingdom, that offered cooling therapy within clinical trials since 1998. Eligible infants (n = 55) developed grade 2/3 encephalopathy after birth and fulfilled the entry criteria defined in the CoolCap trial. Encephalopathic infants with similar demographic values were either nursed under normothermia or 72 h-hypothermia. Once-daily gentamicin dosage (4-5 mg/kg) was administered, and trough SGC was recorded with corresponding creatinine concentrations. The time and number of omitted drug doses were noted.

RESULTS

Mean trough SGC (pre-second dose) and mean plasma creatinine concentrations for both treatment groups were similar (gentamicin: 2.19 +/- 1.7 [hypothermia] and 2.30 +/- 2.0 [normothermia] mg/L; creatinine: 115.6 +/- 42.8 [hypothermia] and 121.0 +/- 45.1 [normothermia] mumol/L). Forty percent of the trough SGCs in both groups were above the recommended trough concentration of 2.0 mg/L. A significant correlation (r(2) = 0.36) was found between high SGCs and impaired renal function assessed by raised plasma creatinine levels regardless of treatment options.

CONCLUSIONS

Our data confirm that impaired renal function is strongly associated with high SGCs. Reduced body temperatures do not affect the clearance of gentamicin.

Supportive care during neuroprotective hypothermia in the term newborn: adverse effects and their prevention

Hypothermia as neuroprotective treatment requires significant knowledge of how temperature affects all organ systems and interventions used in intensive care. Education and training in resuscitation, including avoidance of hyperthermia, early diagnosis of eligible infants, and initiation of early cooling followed by safe transport of cooled infants to the cooling center seems to be an optimal approach. This article suggests clinical management and shows examples of potential adverse effects of clinical hypothermia. The practical cooling recommendations suggested herein are therefore likely to develop and change over time as more experience is gained.

Effect of Therapeutic Moderate Hypothermia on Multi-drug Resistance Protein 1-Mediated Transepithelial Transport of Drugs

To clarify the effect of therapeutic moderate hypothermia on drug distribution, transepithelial transport via multi-drug resistance protein 1 (MDR1) (also called P-glycoprotein or ABCB1) was evaluated at various temperatures in vitro using LLC-GA5-COL150 cells, which were established by transfecting human MDR1 complementary deoxyribonucleic acid into kidney epithelial LLC-PK(1) cells and express MDR1 on the apical membrane. MDR1 is expressed in the blood-brain barrier to limit drug distribution to the brain by exporting exogenous substances including calcium blockers and antiarrhythmic drugs. Digoxin was used as a typical substrate, as well as the non-substrate tetracycline and paracellular marker inulin. MDR1-mediated transport of digoxin decreased at lower temperatures. Transport of tetracycline also decreased at lower temperatures, probably due to changes in membrane fluidity. However, no change was found at over 32 degrees C, suggesting that passive diffusion does not change during moderate hypothermia. The distribution of MDR1 substrates should be considered during hypothermic conditions, as the clinical outcome could be affected.