Optimizing apnea testing to determine brain death

Excerpt

The final step in the diagnostic process to establish a diagnosis of brain death (BD) in a potential organ donor (POD) with catastrophic brain injury is the apnea test (AT). The whole brain death concept, which is adhered to in most countries, dictates that apnea is the final and most definitive proof of total loss of brain function including the brain stem. This situation is then legally representative of a deceased patient, in spite of intact cardiac function, which allows subsequent organ procurement because this would not be ethically and legally acceptable in a patient considered still “alive”. However, the apnea test, which aims to establish apnea in spite of a significant rise of CO₂ in the blood (which would always trigger respiratory effort in neurologically intact persons without medical suppression of breathing), cannot always be completed due to the fact that hemodynamic instability and/or desaturation may ensue due to interruption of mechanical ventilation and inadequate oxygenation in apnea. To minimize the risk of hypoxia and the subsequent need for interruption of the AT, a common practice is to apply the oxygen-diffusion method (i.e. apneic oxygenation) during the apnea period, after adequate pre-oxygenation. This method has a very high success rate with very low percentages of desaturations that require abortion of the AT [1]. …