Thursday, October 11, 2012

Therapeutic Hypothermia: The Ultimate Brain Freeze

In the past few years, convincing data has led to the establishment of therapeutic hypothermia protocols in Emergency Departments for improved neuroprotection of sudden cardiac arrest patients.  In addition, there is some evidence of improved neurologic outcome in children who suffer prolonged submersion injury in cold water, although much of this is based on case reports.  Naturally, researchers are interested in determining whether therapeutic hypothermia is beneficial for those patients who have suffered cardiac arrest secondary to drowning.  The following are 2 articles, one review and one retrospective, highlighting recent findings from the research surrounding this topic.

This robust article covers multiple aspects of brain resuscitation including pre-hospital care, ventilatory strategies, surfactant therapy, hemodynamic support, and therapeutic hypothermia.  The following are the pertinent findings for therapeutic hypothermia:

  • Early therapies fell out of favor after evidence of increased incidence of survival with persistent vegitative state after treatment with deep and sustained hypothermia.
  • More recent evidence supports the use of moderate hypothermia after cardiac arrest (many caveats to this)
  • Mixed evidence regarding the benefit for therapeutic hypothermia for hypoxic ischemic encephalopathy in pediatrics
  • Most of the evidence for the use of therapeutic hypothermia after out of hospital arrest involves Ventricular Fibrillation arrest, which cannot be fully extrapolated to asphyxial cardiac arrest common with drowning incidents
  • Summary statement: There are no high-level evidence studies of therapeutic hypothermia in drowning. Treatment recommendations are made by extrapolation from studies of asphyxia and CA.
    • First, prevent hyperthermia in comatose victims. If hyperthermia occurs, treat it promptly. 
    • Second, consider maintaining a target core temperature of 32–34 °C for 12–72 h.  Cooling should be started as soon as possible, and re-warming should be slow, at a rate no faster than 0.5 °C/h.

This retrospective study analyzed the outcomes of 20 drowning patients treated with therapeutic hypothermia over a 4 year period.  The following were some of the key findings:
  • 20% of these patients survived with favorable neurological outcome (based on cerebral performance category score), and 70% died.  In comparison with other studies, this showed no statistical benefit from therapeutic hypothermia
  • In this study, submersion time did not appear to effect rate of survival vs death/vegetative state.
  • Negative outcomes in this study were related to prolonged ACLS, absence of motor response after 3 days, abnormal brain imaging, and abnormal lack of cortical response to evoked potential testing

While therapeutic hypothermia continues to gain support for use in Ventricular Fibrillation Cardiac Arrest patients, given the different pathophysiology of drowning induced cardiac arrest, evidence to support its standardized use is lacking.  

Thursday, October 4, 2012

Surfactant Therapy

So what about surfactant therapy?  Since a primary role of surfactant is to decrease surface tension within the lung and keep the alveoli open, it makes sense that water entering the alveoli, which results in both direct cellular damage and surfactant washout, could lead to alveolar collapse and, therefor, decreased gas exchange.  

The Handbook on Drowning, published in 2006 (most recent edition released this year), provided a review of the literature up until then, which was primarily animal models and case studies, all of which provided some evidence to consider surfactant early in the treatment course of acute lung injury due to drowning.  This entry will first cover a review article from 2008 which covers the use of surfactant in pediatric acute lung injury, and will then present 2 more case studies which have been published since that edition of The Handbook on Drowning.

This article reviews the literature on the use of surfactant for acute lung injury in the pediatric population from the last 3 decades.  Some heavy ready, but definitely provides a solid overview of what data is out there.  Here are a few of the important points based on their review:
  • Available evidence best supports the use of surfactant in ALI/ARDS secondary to direct lung injury, as opposed to indirect causes (sepsis, hypovolemic shock, non-thoracic trauma).
  • Most evidence so far from case studies.  Best clinical evidence from studies involving meconium aspiration in neonates
  • Most positive effect seen in younger populations. No long term negative effects from studies of adults or peds.  Most prevalent positive effect is rapid improvement of hypoxia.
  • Direct delivery (Endotracheal tube or bronch) more effective than aerosolized
Conclusion statement: “Exogenous surfactant therapy now is standard in the prevention and treatment of RDS in premature infants, and basic science and clinical evidence support its use in at least some patients who have lung injury associated respiratory failure as described in this article.”

Few randomized controlled trials have been done to determine the effectiveness of surfactant therapy in humans.  In addition, large population studies are scarce.  For this reason, most of the human-based evidence for its use in the drowning patient comes from case studies, two of the more recent ones are reviewed here:

This case study describes the treatment course of a 2.5 year female after prolonged submersion and pulselessness and with fairly dismal prognostic factors.  After hypoxia refractory to multiple ventilation modalities (high PEEP which resulted in pneumothorax, Nitric Oxide, and High Frequency Oscillatory Ventilation), the decision was made to administer surfactant.  The authors report a fairly quick (10 minutes) improvement in pt condition, based both on radiologic and ventilatory findings, leading to an eventual extubation and full neurological recovery.

This letter to the Editor reports on the treatment course of two pediatric patients treated in the ICU from the same submersion event.  A timecourse displaying arterial blood gas levels for both patients shows a rapid improvement shortly after surfactant administration.  In the end, one patient was extubated and had no neurologic dysfunction and one patient died of cerebral injury.

Setting the obvious weaknesses of case reports aside (primarily the lack of control of confounding factors and the small sample sizes), case reports like this do provide some evidence for considering surfactant use, especially in the pediatric population and especially when hypoxia remains despite other standard treatments.  Although the initial review article does advocate for its use early in the treatment process, there is still a large lack of high quality evidence to universally support this, nevertheless something to keep in mind.

Monday, October 1, 2012

Drowning in manure: adding insult to injury

Here is an interesting case report from Turkey published in the September issue of Pediatric Emergency Care.  It highlights the use of surfactant therapy, which has been used and studied for drowning victims for at least 2 decades, in the unusual case of a child who drowned in a pit of manure. The patient was doing fairly poorly during his ICU stay until surfactant therapy was initiated.  Obviously it is hard to tell if this therapy was the cause of improvement or just a coincidental treatment, but it definitely supports keeping this treatment in your arsenal for refractory cases.  More in depth review of surfactant therapy at a later date.

Surfactant Replacement Therapy in a Pediatric Near-Drowning Case in Manure (Ugras et al; Pediatric Emergency Care, 2012).