1997 OPEN FORUM Abstracts
INHALED NITRIC OXIDE TO ENABLE APNEA TEST FOR THE DIAGNOSIS OF BRAIN DEATH
H. Berkenstadt, MD., E. Grimberg, RN., E. Segal, MD., A. Perel, MD., O. Nahtomi, MD. General Intensive Care Unit, Department of anesthesiology and Intensive Care, Sheba Medical Center, Sackler School of Medicine, Tel Aviv University, Tel Hashomer, Israel, 52621
The diagnosis of brain death (BD) is important to facilitate organ retrieval for transplantation and to reduce futile care. The diagnosis of BD requires performance of an apnea test (AT) at which time the patient is monitored for attempts of spontaneous ventilation while pCO2 is allowed to increase to maximally stimulate the respiratory center in the brain stem. Lack of respiratory effort when a pCO2 of 60mm Hg is reached, indicate death of the brain stem and is an essential component of the diagnosis of brain death. During the performance of AT, the patient is disconnected from the ventilator, and oxygenation is maintained by intra-tracheal insufflation of oxygen at 5-10 LPM. In some patients, severe lung injury may preclude performance of AT because of the development of severe hypoxemia upon disconnection from the ventilator. We report the case of a patient in whom the use of inhaled nitric oxide prevented hypoxemia during AT and enabled determination of BD. A 30 year old man was admitted to the intensive care unit with multiple trauma after a motor vehicle accident. His injuries included severe head trauma, Glasgow coma Score-3, lung contusion, abdominal injury and multiple fractures. The patient required significant ventilatory support to achieve adequate oxygenation and ventilation. He was managed with pressure controlled ventilation (7200, Puritan Bennett, Carlsbad, CA) FiO2-1.0, PEEP - 10 cmH2O, I:E ratio 2:1, to maintain SaO2 of 94-97%. Cardiac output and systemic blood pressure were maintained by fluid replacement, intravenous adrenaline (0.05-0.15 mcg/kg/min) and pitressin (2-4 units/hour). Twenty four hours after arrival in the intensive care unit, evaluation for BD revealed no brain stem responses. Two attempts at conventional apnea testing failed because of a rapid decline in saturation upon disconnection from the ventilator. This desaturation occurred despite continuos flow of oxygen and a CPAP of 10 cmH2O. We therefore attempted to perform an apnea test while delivering nitric oxide to the patient. The test was performed by introducing continuous flow of NO (800PPM NO in N2) into the inspiratory limb of the ventilator. The NO level was measured with an electrochemical sensor system (NOxBox, Bedfont Ltd., UK), which measures NO and NO2 concentrations. The monitor sampled intra-tracheal gas through a catheter inserted into the endotracheal tube. Following 5 minutes of stabilization, the patient was disconnected from the ventilator, and oxygen, and low flow of NO were maintained for 10 minutes. This enabled blood gases to reach levels consistent with maximal respiratory center stimulation (pCO2>60mmHg) while pO2 remained adequate (pO2>50mmHg). The performance of AP was completed and the patient declared brain dead. The patient was then connected to the ventilator, and inhalation with NO was maintained. Twelve hours later, when the patients family declined the option of organ donation, inhaled NO was withdrawn, which led to a rapid decline in PaO2. In selected patients in whom AT cannot be performed due to severe lung injury, inhaled NO may improve oxygenation, and enable brain death determination.