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Three Part Question

In [comatose adults patients presenting to the emergency department following asphyxia] does [therapeutic hypothermia] improve [neurologic outcome]?

Clinical Scenario

A 34-year-old woman is discovered hanging from a noose around her neck. When a family member discovers her, she is in respiratory arrest and comatose. The paramedics provide artificial ventilation. After several minutes, the patient\'s breathing returns but she remains unconscious. On arrival at the emergency department, she is haemodynamically stable, normothermic and unresponsive. You are aware of the evidence for therapeutic hypothermia following return of spontaneous circulation for a cardiac arrest associated with a shockable rhythm. Given the potential neuroprotective effect of therapeutic hypothermia, you wonder whether a superior neurological outcome can also be obtained in comatose patients following asphyxia.

Search Strategy

No Best BET was identified on this topic.

Medline (1946 to May week 3, 2013), Embase (1980 to 2013 week 20) and the Cochrane library were searched for relevant articles using the Ovid interface

(exp Therapeutic Hypothermia/or therapeutic hypothermia.mp.) and (exp Asphyxia/or asphyxia.mp. or exp Drowning/or drowning.mp. or exp Submersion/or submersion.mp. or exp Hanging/or hanging.mp. or exp Carbon Monoxide Poisoning/or carbon monoxide poisoning.mp.)

Cochrane library: hypothermia

Search Outcome

Altogether 90 papers were found in Medline, 290 in Embase and 27 in Cochrane. No further papers were found by scanning the references of relevant papers. No randomised controlled trials were found. Several case reports are presented in the medical literature using therapeutic hypothermia with good neurological outcome in drowning or hanging. Four relevant papers are summarised in the table

Relevant Paper(s)

Author, date and country	Patient group	Study type (level of evidence)	Outcomes	Key results	Study Weaknesses
Borgquist and Friberg, 2009 Sweden	13 comatose after near-hanging including 3 patients with cardiac arrest. Total of 6 treated with therapeutic hypothermia.	Retrospective cohort study from 2006 to 2009 in two hospital	Cerebral performance category scale (CPC)	Global survival with good neurological outcome (CPC = 1 or 2): 9/13 (69%), with therapeutic hypothermia 6/6 (100%)	Small retrospective study Outcome based on chart review only No standardised protocol for therapeutic hypothermia Application of therapeutic hypothermia not randomised
Baldursdottir et al. 2010 Iceland	14 comatose patients after asphyxia (3 drowning, 8 hanging, 3 carbon monoxide intoxication and 1 methane poisoning) who all received therapeutic hypothermia. 9/14 with cardiac arrest.	Single center retrospective cohort study from 2002 to 2009	Cerebral performance category scale (CPC)	Global survival with good neurological outcome (CPC = 1 or 2): 9/14 (65%)	Small retrospective study Heterogeneous group of asphyxial injury No control group
Lee et al 2011 Republic of Korea	25 unconscious survivors after near-hanging with 16 cardiac arrest. 13 of the 16 patients after cardiac arrest received therapeutic hypothermia.	Single center retrospective cohort study from 2006 to 2010	Cerebral performance category scale (CPC)	Global survival with good neurological outcome: (CPC = 1 or 2): 1/16 (7.7%) after cardiac arrest despite therapeutic hypothermia in 13 of these 16 patients	Small single-centre retrospective cohort study Application of therapeutic hypothermia not randomised No information about the patients in that hospital treated without therapeutic hypothermia
Choi et al. 2012 Republic of Korea	20 unconscious patients with cardiac arrest after near-drowning who all received therapeutic hypothermia.	Single center retrospective cohort study from 2005 to 2008	Cerebral performance category scale (CPC)	Global survival with good neurologic outcome (CPC = 1 or 2): 4/20 (20%)	Small single center retrospective cohort study, Application of therapeutic hypothermia not randomized, No information about the patients in that hospital treated without therapeutic hypothermia

Comment(s)

There is evidence that therapeutic hypothermia is of benefit to undifferentiated patients with spontaneous return of circulation following cardiac arrest (Arrich et al, 2009). The neuroprotective effects of therapeutic hypothermia are therefore theoretically advantageous in comatose patients following asphyxia. However, all the studies included in this review were small retrospective cohorts without any randomisation for the application of therapeutic hypothermia. The majority of patients studied had been resuscitated from cardiac arrest. The clinical outcome was mostly assessed by review of medical charts only. Only one study presented a comparison between the outcome of patients treated with therapeutic hypothermia and those who did not received therapeutic hypothermia. Three of the four included studies reported what appear to be good outcomes following the use of therapeutic hypothermia. However, as these data are observational in nature (and largely without any comparison to a control group) they should be interpreted with caution. We found no data confirming the improvement of the neurological prognosis using therapeutic hypothermia after near-hanging or near-drowning. A large, multicentre, prospective randomised trial would be required to evaluate definitively the potential benefit or harm of this treatment.

Editor Comment

CPC, cerebral performance category scale.

Clinical Bottom Line

Evidence for the use of therapeutic hypothermia in patients who are comatose following asphyxia is very limited, which precludes an evidence-based recommendation. A large, multicentre randomised controlled trial is necessary to answer this question. Our review has therefore highlighted an important area for further research.

References

1. Borgquist O, Friberg H. Therapeutic hypothermia for comatose survivors after near-hanging - A retrospective analysis. Resuscitation 2009;80:210–12.
2. Baldursdottir S, Sigvaldason K, Karason S, et al. Induced hypothermia in comatose survivors of asphyxia: a case series of 14 consecutive cases. Acta Anaesthesiol Scand 2010;54:821–6.
3. Lee BK, Jeung KW, Lee HY, et al Outcomes of therapeutic hypothermia in unconscious patients after near-hanging. Emerg Med 2011;29:748–52.
4. Choi SP, Youn CS, Park KN, et al. Therapeutic hypothermia in adult cardiac arrest because of drowning. Acta Anaesthesiologica Scandinavica 2012;56:116–23.