INTRODUCTION: Apnea testing (AT) is the standard for clinical diagnosis of brain death. Intensivists must be prepared to perform AT as part of routine Intensive care Unit (ICU) duties. The safety of AT has been a topic of debate with the most common complications observed being hypotension, hypoxemia and acidosis. We describe a case of bilateral tension pneumothoraces during AT.
CASE PRESENTATION: A 57 year old woman with past medical history of hypertension, fibromyalgia and hypothyroidism was brought to the hospital unresponsive and intubated. Initial neuro imaging was consistent with global anoxia revealing bilaterally symmetrical basal ganglia and occipital infarcts apparently secondary to fentanyl overdose. She progressively deteriorated over the following 12 hours until brainstem reflexes were absent. American Academy of Neurology pre-requisites for apnea testing were met, including euvolemia, core temperature > 36.5 degrees and normotension. Formal AT was initiated. The patient was removed from ventilator and a 12 french oxygen catheter was placed at the level of the carina within the lumen of a 7.0 millimeter endotracheal tube (ETT). After 4 minutes of observed apnea, hypotension and desaturation ensued followed by obvious subcutaneous air in the thorax and head necessitating termination of AT. Chest X-ray confirmed bilateral tension pneumothoraces and subcutaneous emphysema treated with thoracostomy. Cerebral blood flow testing performed immediately after thoracostomy confirmed brain death.
DISCUSSION: Tension Pneumothorax is an extremely rare complication encountered during AT. Predictors for its development should be identified to limit potential life threatening complications. Wijdicks et al(1) reviewed 228 cases of AT and no pneumothoraces were described. Saposnik et al(2) identified acidosis as a risk factor for developing complications during AT. The patient described here had no apparent risk factors and had normal hemodynamic and acid-base status prior to AT. Review of the AT in this case revealed that the oxygen tubing was likely not moving freely within the smaller lumen ETT (7 millimeter) nor was gas noted to be venting from the ETT. We suspect that a snug fit between oxygen tubing and ETT did not allow sufficient venting of oxygen flow in this case precipitating the pneumothoraces.
CONCLUSIONS: ETT luminal diameter, oxygen tubing outer diameter and depth of placement should be shown careful attention in AT. Vigilance with respect to presence of adequate residual ETT lumen to allow ventilation with oxygen flow rates set at physiologic minute volumes, and preferably, review and standardization of these parameters by prospective studies will lessen the risk of pneumothoraces during AT.
Reference #1 Wijdicks EF, Rabinstein AA, Manno EM, Atkinson JD. Pronouncing brain death: Contemporary practice and safety of the apnea test. Neurology. 2008 Oct 14;71(16):1240-4
Reference #2 Saposnik G, Rizzo G, Vega A, Sabbatiello R, Deluca JL. Problems associated with the apnea test in the diagnosis of brain death. Neurol India 2004;52:342-5
DISCLOSURE: The following authors have nothing to disclose: Naveed Hasan, David Landsberg
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