Saturday, December 29, 2012

Autonomic Conflict and Cardiac Arrhythmias

‘Autonomic conflict’: a different way to die during cold water immersion?.
Authors: Michael Shattock, Michael Tipton

I had the pleasure of seeing this research presented at the World Conference on Drowning Prevention in 2011, and I think it stands as a great example of the role that applied clinical science can play on improving our understanding of drowning.  Dr Tipton has provided a wealth of knowledge and research to the field, especially involving cold water submersion.  This paper highlights the topic of "Autonomic Conflict" and its proposed role in sudden cardiac death in drowning.

Study focus: "In this review we describe a cardiac arrhtymogenic response that we believe may account for some immersion deaths but, due to its nature, largely goes unnoticed or detected.  We have termed the trigger for this response 'autonomic conflict'."

Autonomic Conflict
  • Cold shock response: thermorecptor mediated, tachycardia, gasp, hyperventilation, vasoconstriction
  • Diving response: cardiac vagal response, bradycardia
  • Contrary to classic belief of a "Yin/Yang" relationship between sympathetic and parasympathetic responses, with one being "on" while the other is "off", the authors argue the idea that the effect of both responses being "on" and "conflicting" at the same time leads with rhythm instability.
While the primary response much individuals experience is rapid heart rate due to cold shock response, other events like breath holding can cause autonomic conflict.  This is supported by studies cited in which young.healthy participants displayed higher incidence of arrhythmias during cold water submersion with breath holding.

There is also a section in the paper on abnormal QT interval response that I am still trying to wrap my head around, more to come on that.

All in all, this is a fairly complex paper that takes more focused attention than usual to get through, but it offers evidence for an interesting phenomena that likely plays an important role in drowning deaths.  Cheers to Drs Shattock and  Tipton for their continued groundbreaking work.

Shattock M, Tipton M.‘Autonomic conflict’: a different way to die during cold water immersion?.  J Physiol. 2012; 14: 3219-3230.

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).

Thursday, September 27, 2012

Resuscitation June 2012

Today I present two articles from the June 2012 issue of Resuscitation, primarily to highlight the impressive efforts of the European and Scandanavian drowning research community.  Continually, they have provided high quality epidemiological data particularly in regards to cold water submersion.

The first article by Wanscher et al, describes the treatment course and outcomes of a very unique and interesting study population.  They report on a tragic but enlightening event which can only be described as an accidental case-control study, in which 15 individuals submerged in cold water after their boat capsized.  Of these 15, 1 died from drowning during the event, 7 survived with spontaneous circulation, and 7 survived after prolonged resuscitation.  This report takes you through their inpatient evolution, beginning with an the impressively fast initiation of ECMO and ending with decryption of their long term neurocognitive outcomes.  Definitely an interesting read, more on ECMO in the future.

The next article by Claesson et al, attempts to characterize every documented drowning case responded to by its national EMS system over a 15 year span.  While the article does a good job of using what data is available to subcategorize cases based on environmental and demographical aspects, what I like most about it is its ability to show the importance of working toward the establishment of a national drowning registry to include both fatal and non-fatal incidents so that the highest quality data can be obtained.

The final article is an Editorial from the same issue which highlights some of the important points from the previously mentioned articles.  Definitely some interesting and unique data on cold water submersion survival.

Outcome of accidental hypothermia with or without circulatory arrest, Experience from the Danish Præstø Fjord boating accident (Wanscher et al; Resuscitation, 2012)

Characteristics of lifesaving from drowning as reported by the Swedish Fire and Rescue Services 1996-2010. (Claesson; Resuscitation, 2012)

Drowning: more hope for patients, less hope for guidelines (Deakin; Resuscitation, 2012)

Wednesday, September 26, 2012

Neurologic long term outcome after drowning in children

As with any disease process, the burden of a drowning incident does not stop after the acute event has been managed.  With the primary pathophysiology being hypoxic/anoxic brain injury, the long term effects and prognosis following a drowning incident can vary greatly from individual to individual based on the severity of the initial injury.  Decades of research have gone into determining prognostic indicators associated with drowning, especially in the pediatric population.

Recently, the Scandanavian Journal of Trauma published an article entitled Neurologic long term outcome after drowning in children (Suominen P, Vähätalo R).  This article reports on the findings from a review of literature to determine the following:

  1. the main factors related to the outcomes of drowned children
  2. existing evidence of long-term neurologic outcome.
Through this review, important factors which have been shown to affect survival were reported as follows: the duration of submersion, the need of advanced life support at the site of the accident, the duration of CPR, and the establishment of spontaneous breathing and circulation on arrival to the ER.  As would be expected, most of these factors can be directly related to the level of hypoxic injury experienced by the patient.

The authors also presented the findings from a series of articles which report on long-term neurologic sequelae following drowning incidents.  There was unfortunately a very large amount of variability on the quality of data and the data points available for analysis.  One data point which was affected greatly was reported submersion time, which highlights the importance of standard reporting of drowning incidents and high quality pre-hospital data collection.


Tuesday, September 25, 2012

Recent Updates

If you are fairly familiar and up-to-date with the latest in drowning resuscitation, pre-hospital, and inpatient treatment, bear with us as we present the following review articles from the pat 3 years which provide a good summary of how to approach the drowning victim in the pre-hospital and Emergency Department setting.

Drowning (Szpilman D, Bierens J, Handley A, Orlowski J; NEJM, 2012)

  • We were very excited to see the latest updates in our field highlighted in The New England Journal of Medicine, especially with the first and second authors being two individuals who have done so much to advance the drowning research community, Drs David Szpilman and Joost Bierens.  One of the most powerful aspects of this article is the inclusion of a classification algorithm for the drowning victim based on the expansive data collection done by Dr Szpilman in Brazil.  During a recent lecture to EMS professionals, I found this algorithm very helpful to help put in perspective how different clinical signs can correlate with outcome.
  • We will "toot our own horn" by posting this one, but this is a review our organization did this year in collaboration with The University of Nevada School of Medicine Emergency Medicine Department.  It's content was primarily aimed at the pre-hospital professional with a large emphasis on the importance of oxygenation in combating the effects of cerebral hypoxia on outcome.  

Since we have now provided a solid foundation, from here on out we will do our best to provide quality literature focusing in on the aspects of epidemiology, treatment, and outcomes.

Monday, September 24, 2012

2002 World Congress on Drowning Recommendations

As an inaugural post, we will start out with the landmark meeting of the World Congress on Drowning in Amsterdam in 2002.  If you are visiting this site you are probably familiar with (and may even have attended) this meeting.  During this meeting, the congress developed recommendations with the focus of standardizing the definition and reporting of drowning around the world

A quick synopsis of the recommendations:

A universal standard definition for drowning was established:

Drowning is the process of experiencing respiratory impairment from submersion/immersion in liquid.

Once it is determined a drowning incident has occurred, there are 3 possible outcomes:
  1. Morbidity
  2. No morbidity
  3. Mortality
A great article by Idris et al in 2005 outlined these recommendations and provided sample data collection sheet based on them

There are many articles which provide evidence to support the importance of establishing a standard definition for drowning, one of our favorites being by Papa et al (2005), which highlights the amount of variation present within the research world when it comes to defining  exactly what is meant by the term "drowning".