Journal of ISSN: 2373-6437JACCOA

Anesthesia & Critical Care: Open Access
Case Report
Volume 1 Issue 4 - 2014
Apnea Test for Brain Death Diagnosis in a Patient on Extracorporeal Membrane Oxygenation
Iannuzzi M*, Marra A, De Robertis E and Servillo G
Department of Neuroscience, Odontostomathological and Reproductive Science -Federico II University Hospital, Italy
Received: July 26, 2014 | Published: September 18, 2014
*Corresponding author: Iannuzzi M, Department of Neuroscience, Odontostomathological and Reproductive Science -Federico II University Hospital–Via S. Pansini 5, 80100, Italy, Tel: 390817463542; Email: @
Citation: Iannuzzi M, Marra A, De Robertis E, Servillo G (2014) Apnea Test for Brain Death Diagnosis in a Patient on Extracorporeal Membrane Oxygenation. J Anesth Crit Care Open Access 1(4): 00020. DOI: 10.15406/jaccoa.2014.01.00020

Abstract

Background: Apnea test in most countriesis a fundamental partin Brain Death (BD) diagnosis. In patients receiving extracorporeal membrane oxygenation supportpnea test remains challenging and controversial.
Case: We report the case of a 40 yearold man receiving veno-venous Extracorporeal Membrane Oxygenation (ECMO) as a respiratory support presenting signs of brain death. Decreasing ECMO flow and gas sweep flow while the patients lungs were kept on a Continuous Positive Airway Pressure (CPAP) during the apnea test allowed the PaCO2 to increase without decreasing of PaO2.
Discussion: In order to diagnose BD apnea test must be accomplished in some countries. Carbon dioxide removal by the ECMO membrane makes CO2 rise verydifficult. Sweep gas decrease on ECMO can make CO2 rise possible but exposes patients to hypoxemia. Decreasing gas flow on the oxygenator and concomitantly inflating the lungs on a 100% oxygen CPAP allowed us to perform apnea test safely.
Conclusion: With the technique described apnea test can be safely assessed without exposing patients to hypoxemia.
Keywords: Brain death; Apnea test; Extracorporeal membrane oxygenation; Sweep gas

Abbervations

BD: Brain Death; ECMO: Extracorporeal Membrane Oxygenation; CPAP: Continuous Positive Airway Pressure; GCS: Glasgow Coma Scale

Introduction

Extracorporeal membrane oxygenation (ECMO) is increasingly used as a means of extra corporeal support to a wide variety of patients. The Extracorporeal Life Support Organisation reported that 21% of patients undergoing extracorporeal CPR were brain dead [1]. Due to carbon dioxyde removal via the oxygenator membrane apnea test remains controversial and challenging in patients on ECMO in the lack of published guidelines [2].

Case Report

A 40 year old male has been admitted to our Intensive Care Unit for respiratory failure due to suspected Guillan Barre Syndrome and concomitant interstitial pneumonia. The patient rapidly developed severe Acute Respiratory Distress Syndrome. A veno-venous ECMO with a femoral-jugular access was placed to assist oxygenation on day 3. On ECMO day 2 bilateral midriasis associated with diabetes insipidus were reported. A brain CT scan was performed and revealed massive cerebral hemorrage. Sedation was stopped for neurological assessment. Neurological examination revealed bilateral midriasis, Glasgow Coma Scale Score (GCS)=3T, absence of brainstemreflexes, electro encephalographic silence. During neurological examinationbody temperature was 36.5°C, mean arterial pressure was > 80mm Hg , heart rate was 80bpm and a nor epinephrine infusion of 0.12 mcg/kg/h was administered. No acid base and electrolyte disturbances were present. ECMO parameters were 4 L/min blood flow, 8L/min Oxygen flow with a FiO2 of 0.7. Ventilator settings were TV 650ml, Respiratory Rate 14/min, FiO2 0.7, Pplateau 30cm H2O, Peep 10cm H2O. In order to assess brain death diagnosis also an apnea test had to be performed.
During the apnea test patient was kept on a Continuous Positive Airway Pressure (CPAP) of 10cm H2O on 100% oxygen via a T- piece to sustain oxygenation [3]. ECMO blood flow was decreased to 2L/min and gas flow sweep was reduced to 0.5L/min with a FiO2 of 1.0. In line CO2 monitoring was performed during the procedure and blood gases were drawn at baseline and when EtCO2 was > 60mm Hg. The apnea test lasted 6 minutes to obtain a PaCO2 level on blood gas analysis of 64.2mm Hg. Sat O2 remained reliably stable > 90% during the procedure and light hypoxemia developed during the course of the 6 minutes apnea test. (PaO2 159 mmHg → 80 mmHg). We closely observed the patient’s chest movements, the CO2 tracing and the ventilator flow for any spontaneous breathing effort.

Discussion

Clinical assessment of brain death in Italyis made on several criteria according to current Law (Legge 29 Dic 1993n°578 / D.M. 22 Ago 1994 n° 582 / D.M.S. 11 Apr 2008). Cerebral death is defined as irreversible loss of known etiology of the functions of the whole brain, including the brainstem, associated with loss of electro encephalographic activity.
According to Italian law apnea test is a fundamental requisite in the diagnosis of brain death and cannot be substituted by anyother tes tunless it is not possible to adequately perform apnea test. A positive apnea test is defined by the absence of respiratory activity at a PaCO2 ≥ 60mm Hg. The pre requisites for a valid test are the presence of normotension, normothermia, absence of blood gas and electrolytes disturbances. There are no published guidelines for diagnosing brain death in patients with veno-venous ECMO support. Performing an apnea test in such patients can be challenging and physicians have considered it too difficult to perform [4] in a retrospective review in adult streated with ECMO at Mayo Clinic (2002-2010) found thatl oss of all brain stem reflexes was identified in three cases (3/87, 3.4%); the apnea test was not performed since it was deemed ‘‘difficult,’’leading to withdrawal of ECMO and intensive care.
When a patientis diconnected from the ventilator to perform the apnea test, poorly oxigenated blood returning from the lungs to the left heart side can cause hypoxemia. Reduction of sweep gas flow on the oxygenator can worsen hypoxemia in the above conditions before we can appreciate a valid CO2 rise for the diagnosis of brain death. The authors propose a simple and reliable method to safely guarantee oxygenation and CO2 increase according to the recommendations made by [4,5]. The authors proposed an approach based on continuous lung insufflation at a FiO2 1.0 with 10cm H2O CPAP and the lowest possible oxygenators weep flow to maintain an oxygen saturation ≥ 90% with no addition of CO2 on the oxygenator circuit. After eucapnia (35-40mm Hg) is confirmed with arterial blood gas, apnea is confirmed by absence of respiratory activity when an absolute PaCO2 > 60mm Hg is achieved. The authors wereable to perform safely the apnea test with the current methodology.
According to the Italian Law (Legge 29 Dic 1993 n° 578 / D.M. 22 Ago 1994 n° 582 / D.M.S. 11 Apr 2008) in the case apnea test cannot be safely performed a blood flow test must be performed to confirm brain death. Absence of intra cranial blood flow can be assessed by means of CT angiography, digital angiography or transcranial doppler. In the first two casesthe procedure might be hazardous because the potential organ donor must be transferred on ECMO to the radiology ward. In the case of transcranial doppler assessment 2 recordings are needed: on eat baseline which demonstrates flow and a second which demonstrates absence of flow; it is not standard practice to perform transcranial doppler in all neurologic patients at baseline.

Conclusion

In Italy apnea testing is fundamental for brain death diagnosis but is challenging in patient son ECMO. World wide it is not employed consistently on ECMO patients due to the lack of standardized and universal procedures. Timely brain death diagnosis is important for families, ICU organisation and for possible organ donation. We describe a simple, safe and accurate method of apnea testing in presumed brain dead patients during ECMO in the lack of published guidelines.

References

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  2. Wijdicks EF, Varelas PN, Gronseth GS, Greer DM (2010) Evidence-basedguidelineupdate: determining brain death in adults: report of the Quality Standards Subcommittee of the American Academy of Neurology. Neurology 74(23): 1911-1918.
  3. Levesque S, Lessard MR, Nicole PC, Langevin S, LeBlanc F, et al. (2006) Efficacy of a T-piecesystem and a continuous positive airway pressure system for apnea testing in the diagnosis of brain death. Crit Care Med 34(8): 2213-2216.
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