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ARTICLES: E. Al Thenayan, M. Savard, M. Sharpe, L. Norton, and B. Young Predictors of poor neurologic outcome after induced mild hypothermia following cardiac arrest Neurology 2008; 71: 1535-1537 [Abstract] [Full text] [PDF]

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Predictors of poor neurologic outcome after induced mild hypothermia following cardiac arrest

William D. Freeman, Kevin M Barrett MD, M.Sc., Michelle L. Biewend MD, Margaret M Johnson M.D., Gavin D. Divertie M.D., James F. Meschia M.D.   (6 February 2009)

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G. Bryan Young, MD, FAAN   (6 February 2009)

Predictors of poor neurologic outcome after induced mild hypothermia following cardiac arrest 6 February 2009
William D. Freeman, Mayo Clinic Florida 4500 San Pablo Road, Jacksonville, Florida 32224, Kevin M Barrett MD, M.Sc., Michelle L. Biewend MD, Margaret M Johnson M.D., Gavin D. Divertie M.D., James F. Meschia M.D. Send Correspondence to journal: Re: Predictors of poor neurologic outcome after induced mild hypothermia following cardiac arrest freeman.william1{at}mayo.edu William D. Freeman, et al.	We read the article by Thenayan et al. with great interest. The authors address the challenge of predicting outcomes in patients receiving hypothermia post-arrest. [1] Review of 282 medical records identified 37 eligible patients. They found absent pupillary light reactivity, absent corneal reflexes, and myoclonus status epilepticus at 72 hours had a false positive rate (FPR) of 0% for regaining future awareness. Two of 14 patients with motor response no better than extension regained consciousness at day 3, giving a FPR of 14 percent. Outcomes were not provided for patients without these clinical findings. At our clinic, 25 patients received mild induced hypothermia after cardiac arrest. These patients were retrospectively identified from 259 arrest patients seen over a 27-month period. At hospital discharge, recovery of awareness was achieved in 28% (7/25). Six patients died within 72 hours of arrest. Five patients with absent pupillary light response (FPR 0%) and eight patients with motor response no better than extension (FPR 0%) never recovered awareness at 72 hours. However, those patients with preserved pupillary light response and motor responses better than extension at 72 hours post-arrest had variable outcomes. Fifty percent (7/14) of patients with preserved pupillary reflexes and 36% (4/11) with preserved motor responses died or remained vegetative. Thenayan et al.’s results suggest a cautious interpretation of motor responses in post-arrest patients that are cooled. Potential confounders include: lingering sedation or neuromuscular blockade despite intact train of four response [2-3]; differences in methods of assessment of motor response between examiners [4]; or the development of critical illness polyneuropathy/myopathy or some other neurologic cause of lack of motor response.[5] Larger, prospective studies are needed to re-assess the validity of traditional clinical outcome predictors in patients treated with hypothermia. Identification of good outcome predictors is imperative. Traditional clinical parameters appear helpful when absent, however heterogeneous outcomes are apparent when bulbar and motor responses are preserved. Early, non-clinical surrogates such as neuroimaging, including functional studies, and serum markers need to be incorporated into future studies. Multivariable prognostication models have been useful in other clinical states and also need to be explored in this clinical setting. Finally, patients ineligible for hypothermia or those that awaken shortly after resuscitation should not be excluded from future prognostication and intervention studies. Further understanding of the more subtle cognitive sequelae of anoxia that are not captured by currently used outcome scales is necessary as these patients may be amenable to intervention. References 1. Al Thenayan E, Savard M, Sharpe M, Norton L, Young B. Predictors of poor neurologic outcome after induced mild hypothermia following cardiac arrest. Neurology 2008;71:1535-1537. 2. Eikermann M, Gerwig M, Hasselmann C, Fiedler G, Peters J. Impaired neuromuscular transmission after recovery of the train-of-four ratio. Acta Anaesthesiol Scand 2007;51:226-234. 3. Eikermann M, Koch G, Gerwig M, et al. Muscle force and fatigue in patients with sepsis and multiorgan failure. Intensive Care Med 2006;32:1627–1631. 4. Wijdicks EF. Temporomandibular joint compression in coma. Neurology 1996;46:1774. 5. Bolton CF. Neuromuscular manifestations of critical illness. Muscle Nerve 2005;32:140-163. Disclosure: The authors report no disclosures.
Reply from the author 6 February 2009
G. Bryan Young, MD, FAAN, University of Western Ontario Room B10-106, University Hospital, 339 Windermere Rd., London, ON, Canada N6A 5A5 Send Correspondence to journal: Re: Reply from the author bryan.young{at}lhsc.on.ca G. Bryan Young, MD, FAAN	We thank Dr. Freeman and his colleagues for their interest and their observations on a series of cardiac arrest patients treated with hypothermia. Neither their series nor ours is very large and it is difficult to draw firm conclusions. However, none of the confounders that they mention apply to our series. We felt it was important to publish our findings because two patients with motor responses no better than extension after day 3 regained the ability to follow commands. A longer period, at least to day 6, appears to be indicated before relying on the motor response in hypothermia-treated patients. We agree that further research is needed on the prognosis of patients who are initially comatose after resuscitation from cardiac arrest (including those treated with the hypothermic protocol and others) to better define prognostic criteria for a range of outcomes. Disclosure: The author reports no disclosures.