USEFULNES AND COMPLICATION OF APNEA TEST(AT) FOR BRAIN DEATH DIAGNOSIS (BDD) IN 388 CASES

Authors: Suxo M1Previgliano IJ1, Cabezas DV2, Antik AA3, Baqué MC3, Ponteville Ch4.1 Neurocritical Care and Organ and Tissue Procuration for Trasplantation

Management Unit Hospital J. A. Fernández

2 Critical Care Unit – Hospital J. M. Ramos Mejía3Buenos Aires Trasplantation Institute

4 Cátedra de Matemática. Facultad de Farmacia y Bioquímica. UBA

Literature Search 1: Hornby K, Shemie SD, Teitelbaum J, Doig C. Variability in hospital-based brain death

guidelines in Canada. Can J Anaesth. 2006 Jun;53(6):613-9. 2: Sharpe MD, Young GB, Harris C. The apnea test for brain death determination: an

alternative approach. Neurocrit Care. 2004;1(3):363-6. 3: 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 Sep;52(3):342-5. 4: Melano R, Adum ME, Scarlatti A, Bazzano R, Araujo JL. Apnea test in diagnosis of brain

death: comparison of two methods and analysis of complications. Transplant Proc. 2002 Feb;34(1):11-2. No abstract available. PMID: 11959165 [PubMed - indexed for MEDLINE]

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6: Flowers WM Jr, Patel BR. Accuracy of clinical evaluation in the determination of brain death. South Med J. 2000 Feb;93(2):203-6.

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Objectives

Evaluate the safety of AT Evaluate AT performance in

general Intensive Care Unit Identify complications and

contraindications Analyze blood gases changes

Proceedings Hospital ICU physician identify a probable brain

death patient Hospital coordinator (if available) evaluates

prerequisites and perform neurological examination

If the patient met all of them Buenos Aires Transplant Team is called as the authority to make BDD

AT is performed by the team and if it is positive a complimentary confirmative diagnostic method is performed (EEG, SSEP, TCD) followed by a 6 hs later AT

The hour of death is the one of the first evaluation that includes the AT

Apnea test according Argentine organ donation law’s proceedings

Patient should be monitoring at least with ECG and SpO2.

Reach normocapnia with FiO2 1

Blood gases sample Disconnect ventilator and put

an O2 supplement with endotracheal catheter at 5 l/min

Search for spontaneous respiration up to 10 minutes

Blood gases sample (PCO2 >60 mmHg implies positive test)

Criteria for suspension: Hemodynamic instability Arrhythmia Desaturation

Apnea test according Argentine organ donation law’s proceedings

Alternative 1 (no blood gases availability)

Ventilate the patient with FiO2 1, tidal volume of 500 ml at a respiratory rate of 10 for 45 minutes

Disconnect ventilator and put an O2 supplement with endotracheal catheter at 5 l/min

Search for spontaneous respiration up to 10 minutes

Criteria for suspension: Hemodynamic instability Arrhythmia Desaturation

Alternative 2 Ventilate the patient with CO2

7% enriched mixture at 5l/min for 5 minutes.

Blood gases sample Disconnect ventilator and put

an O2 supplement with endotracheal catheter at 5 l/min

Search for spontaneous respiration for to 2 minutes

Blood gases sample (PCO2 >60 mmHg implies positive test)

Criteria for suspension: Hemodynamic instability Arrhythmia Desaturation

Material y method Study Design: Prospective database analysis Interventions: AT according Argentinean law protocol Data collected: Age, sex, cause of death, organ donation,

cardiac arrest (CA), AT performance by ICU physicians , blood gases, isopodous diabetes, sepsis, multiorgan failure, vasoactive and depressor drugs, mean arterial pressure and confirmative instrumental method.

Statistical analysis: Two tail Student’s test, Chi squared test, Calculation of: Sensitivity: AT positive/(True positives + False positives). Specificity: AT negative/(True negatives + False Negatives). Positive predictive value: AT positive/ (True positives + False Negatives). Negative predictive value: AT negative/ (True negatives + False Positives). Likelihood ratio for a positive test result (LR+): Sensitivity/(1 - Specificity). Likelihood ratio for a negative test result (LR-): (1 – Sensitivity)/Specificity

Results From 1/01/06 to 30/06/07 388 of probable BD

were received. These generated 353 donation process that

involved 58% of males with a mean age of 43±20 yo.

Main BD causes were: Spontaneous intraparenchimal hematoma (31%), Head injury (25%) and Subarachnoid Hemorrhage (20%).

Organ donation was achieved in 37%. CA presented in 21%. Disconnection after BDD 38% Mean temperature was 35,9ºC±1,6ºC MAP was 86,2 mmHg ± 18,7.

Results

AT wasn’t performed in 22% of the cases due to: Hemodynamic instability 39% Tiopenthal 21% Absence of prerequisites for BD 14% Hypoxemia 9% CA 9% EEG activity 7%.

Results BDD was completed in 53% 36% presented CA before evaluation

completion 14% were alive 261 AT were performed with blood

gases and 16 without. 72% (189) AT were performed with 7% CO2

technique Only 5,2% had an AT performed by ICU

physicians (only in Hospital Fernández)

Results Complications were present in 1,44%

(n=4) These were:

Cardiac arrest 0,3% (n=2) Hypoxemia 0,7% (n=2) Ventricular tachycardia 0,3% (n=1)

None of them made the corpse’s lost

Results

pH pre pH post PCO2 pre PCO2 post PO2 pre PO2 post

Median 7,36 7,11 37,99 82,33 264,28 217,35

SD 0,09 0,14 10,87 26,50 127,80 120,754

p value < 0,001 < 0,001 0,15

Changes in blood gases before and after AT

PCO2 average minute increase: 4.3 ± 2.78 mmHg/min

Results

Death Alive

AT Positive 254 0 254

AT Negative 0 23 23

254 23 277

Positive predictive value

a/(a + b) 99,8%

Negative predictive value

a/(c + d) 97,9%

Sensitivity a/(a + c) 99,8%

Specificity d/(b + d) 97,9%

LR + Sens/(1-Spec) 47,9

LR - (1-Sens)/Spec 0,002

a b

c d

Calculation proceedings according to Sackett DL, Strauss SE, Richardson WS, Rosenberg W, Haynes RB (editors) “Evidence-Based Medicine, How to Practice and Teach EBM”, Hardcourt, Edinburgh, 2000.

Results

Instrumental method

AT performed AT not performed

p value

EEG 81% 48% < 0,01

SSEP 16% 35% 0,04

TCD 12% 26% 0,04

Conclusions According to our findings AT is the ideal test

for BDD, taking into account 1976 Royal College of Medicine, 1977 Argentinean law or 1981 US Presidential Commission criteria.

When it is not possible to perform AT, complex confirmatory instrumental methods are needed.

Most of AT were performed with 7% CO2 technique and there were no differences in complication rate with the standard method.

Conclusions Complication rate is low and lower

are fatal complications. AT is not routinely performed at

the ICU. ICU physicians and hospital

coordinators should be trained in AT performing in order to accelerate BDD times.

Thank you for your atentionNo questions please!!!!