Apnea testing for the diagnosis of brain death

Neurologische Universitätsklinik, Erlangen, Germany.
Acta Neurologica Scandinavica (Impact Factor: 2.4). 01/2006; 112(6):358-69. DOI: 10.1111/j.1600-0404.2005.00527.x
Source: PubMed


A review is given on various methods, preconditions and pitfalls of apnea testing for the diagnosis of brain death.
An extensive medical data base search was implemented by information gathered from books and our own experience with more than 2000 apnea tests.
While testing for apnea (AT) is considered indispensable worldwide, recommendations and handling differ. Rather than relying on elapsed time, a specific target value for the partial arterial pressure of carbon dioxide (PaCO2) should be aimed at being the maximum physiological stimulus for respiration. Methodological points are elaborated upon in detail for apneic oxygenation and hypoventilation.
AT is an indispensable element of diagnosing brain death. Although with proper handling and adequate precautions AT is safe, it should be performed as a last resort. An international agreement on target values for the PaCO2 is desirable.

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    • "While some countries, such as the U.S., Canada, and Germany, set the target PaCO2 level at 60 mmHg, other countries such as Korea, the U.K., Switzerland, and Portugal set 50 mmHg as the target PaCO2 level. These differences are not meaningful from a medical standpoint, given that the optimal level for sufficiently stimulating the respiratory center is unknown [14]. However, based on the difference in target PaCO2, we expect to be able to reduce the duration of the apnea test more effectively in Korea than in other countries. "
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    ABSTRACT: Background The apnea test (AT) is essential to confirming the diagnosis of brain death, but critical complications can occur if the AT is maintained over a long period. To minimize the AT period, we used end-tidal carbon dioxide (ETCO2) monitoring because ETCO2 is closely correlated with partial pressure of arterial carbon dioxide (PaCO2). The aim of the present study is to evaluate the usefulness of ETCO2 monitoring during apnea testing. Methods We reviewed 61 patients who were pronounced brain dead at our hospital from July 2009 to December 2012. The subjects were divided into two groups: the N-group, in which capnography was not used, and the C-group, in which capnography was used to monitor ETCO2. In the C-group, whenever arterial blood was sampled, the PaCO2 - ETCO2 gradients were calculated and the ventilator setting adjusted to maintain normocapnia prior to apnea testing. Results Twenty-eight subjects in the N-group and twenty-nine subjects in the C-group were included. The gender ratio, age, and cause of brain death were not different between the two groups. Prior to the AT, the normocapnia ratio was higher in the C-group than in the N-group. During the AT, the total test period was shorter in the C-group. Moreover, systolic blood pressure increased in the C-group and decreased in the N-group during apnea testing. Conclusions ETCO2 monitoring during AT allows the PaCO2 level to be predicted, which reduces the duration of the test and stabilizes systolic blood pressure. Thus, with ETCO2 monitoring, the AT can be fast and safe.
    Full-text · Article · Sep 2014 · Korean journal of anesthesiology
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    • "Other variables Levésque et al. 2006). In the hypoventilation and CPAP methods the patient is not disconnected from mechanical ventilator but minute ventilation volue is reduced to a very low level such as 0.5 - 2 L min −1 (Lang and Heckmann 2005) or ventilation mode is changed to CPAP mode with 100% O 2 (Levésque et al. 2006), respectively. Apneic oxygenation is still widely accepted method for AT and described as follows in the guideline of AAN; ventilatory assistance is discontinued and 6 L min −1 100% O 2 is delivered into the trachea via an O 2 catheter optionally placed " at the level of the carina " while waiting for spontaneous respiratory movements (The Quality Standards Subcommittee of the American Academy of Neurology 1995). "
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    ABSTRACT: Apneic oxygenation is an apnea testing method in the diagnosis of brain death. In this method, oxygen (O2) is delivered into the trachea via an O2 catheter (O2C). However, barotrauma may develop during O2 insufflation into the trachea. Oxygen catheter diameters, O2 catheter tip position in the trachea, and O2 flow rate have been proposed as causes of barotrauma. This study was designed to highlight the airway pressure changes during apneic oxygenation in a model consisting of an anesthesia bag, which was connected to a pressure transducer and to an endotracheal tube (ETT). The pressure of the system was monitored while delivering O2 continuously to the system through O2C of different diameters, which were placed in the ETT. Tested variables were ETT/O2C ratio, O2C tip position in ETT (proximal 1/3 of the ETT, mid point of the ETT, and distal 1/3 of the ETT) and O2 flow rate (6, 8, and 10 L min(-1)). The increase in the airway pressure significantly correlated with O2C tip position in ETT (p = 0.017). ETT/O2C ratio smaller than 1.75 caused significantly high airway pressures (p < 0.05). The pressure was significantly higher at the flow rate of 10 L min(-1) O2 compared with the flow rate of 6 L min(-1) O2 (p < 0.01). Thus, ETT/O2C ratio, O2C tip position in ETT and O2 flow rate are the important factors that determine the airway pressure in the trachea during O2 insufflation. In conclusion, overlooked mechanical factors dangerously increase airway pressure during apnea testing.
    Full-text · Article · Mar 2007 · The Tohoku Journal of Experimental Medicine
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    ABSTRACT: Nella storia della trapiantologia il rene ha svolto sicuramente un ruolo di pioniere. I primi tentativi di impianto, i primi successi e i primi programmi di applicazione clinica su casistiche numerose hanno visto infatti il trapianto renale sempre all'avanguardia. Il trapianto da donatore vivente, essendo stato la prima forma di trapianto renale con risultati clinici incoraggianti in epoche in cui le conoscenze delle barriere immunologiche risultavano primordiali, ha sicuramente avuto un ruolo di sostanziale promotore per ulteriori ricerche immunologiche, chirurgiche e nefrologiche. Anche ai giorni nostri comunque, il trapianto renale da donatore vivente continua a mantenere una sua pecu- liare validità clinica: esaurito il ruolo di pioniere, il trapianto renale da vivente non ha, in altri termini, perso valore come procedura terapeutica e fertile campo di ricerca medica. La persistente carenza di organi da trapiantare, al di là di possibili miglioramen- ti legislativi, continua inoltre ad imporre fonti alternative al cadavere per le donazioni e sotto questo aspetto il rene, organo pari, rappresenta ovviamente un caso del tutto perculiare nel campo dei trapianti. Un ulteriore ed importante addentellato della procedura di trapianto con dotazione da vivente è costituito dal particolare principio etico-morale richiesto in ogni scelta decisionale, sia medica che umana. L'intento del presente lavoro è stato quello di ana- lizzare la nostra ormai ventennale casistica di trapianto renale per trarne considerazioni retrospettive ed elementi utili, in prospettiva, per il miglioramento del programma.
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