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Prediction of potential for organ donation after cardiac death in patients in neurocritical state: a prospective observational study

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Summary

Background

Successful donation of organs after cardiac death (DCD) requires identification of patients who will die within 60 min of withdrawal of life-sustaining treatment (WLST). We aimed to validate a straightforward model to predict the likelihood of death within 60 min of WLST in patients with irreversible brain injury.

Methods

In this multicentre, observational study, we prospectively enrolled consecutive comatose patients with irreversible brain injury undergoing WLST at six medical centres in the USA and the Netherlands. We assessed four clinical characteristics (corneal reflex, cough reflex, best motor response, and oxygenation index) as predictor variables, which were selected on the basis of previous findings. We excluded patients who had brain death or were not intubated. The primary endpoint was death within 60 min of WLST. We used univariate and multivariable logistic regression analyses to assess associations with predictor variables. Points attributed to each variable were summed to create a predictive score for cardiac death in patients in neurocritical state (the DCD-N score). We assessed performance of the score using area under the curve analysis.

Findings

We included 178 patients, 82 (46%) of whom died within 60 min of WLST. Absent corneal reflexes (odds ratio [OR] 2·67, 95% CI 1·19–6·01; p=0·0173; 1 point), absent cough reflex (4·16, 1·79–9·70; p=0·0009; 2 points), extensor or absent motor responses (2·99, 1·22–7·34; p=0·0168; 1 point), and an oxygenation index score of more than 3·0 (2·31, 1·10–4·88; p=0·0276; 1 point) were predictive of death within 60 min of WLST. 59 of 82 patients who died within 60 min of WLST had DCD-N scores of 3 or more (72% sensitivity), and 75 of 96 of those who did not die within this interval had scores of 0–2 (78% specificity); taking into account the prevalence of death within 60 min in this population, a score of 3 or more was translated into a 74% chance of death within 60 min (positive predictive value) and a score of 0–2 translated into a 77% chance of survival beyond 60 min (negative predictive value).

Interpretation

The DCD-N score can be used to predict potential candidates for DCD in patients with non-survivable brain injury. However, this score needs to be tested specifically in a cohort of potential donors participating in DCD protocols.

Funding

None.

Introduction

Donation after cardiac death (DCD) protocols allow families of patients who are dying but not brain dead to donate organs. Such protocols have been implemented in many countries and might reduce the shortage of available organs for transplantation.1 After withdrawal of life-sustaining treatment (WLST), DCD allows organ procurement in an operating room after irreversible cessation of respiration and circulation has been declared.2 Although such donation contributes an increasing proportion of viable organs for transplantation, identification of appropriate candidates is a restricting factor.

Patients with catastrophic, irreversible brain injury who do not meet criteria for brain death are the most frequent candidates for DCD,3, 4, 5 but about half of these patients continue to breathe and maintain circulation for more than 60 min after WLST.6 The success of DCD relies on identification of patients who are most likely to die within 60 min of WLST. Prolongation of the withdrawal phase of warm ischaemia time (ie, the time between WLST and end of cardiopulmonary function) beyond 60 min can compromise organ function.2, 7 Thus, most DCD protocols do not continue with organ retrieval if the patient is still alive 60 min after WLST.8 However, good outcomes have been reported with organ transplants (particularly kidneys) retrieved after up to 4 h of warm ischaemia.9, 10

Available scores used by organ-procurement organisations to estimate the time to death after WLST, such as the Wisconsin criteria3 or the United Network for Organ Sharing (UNOS) criteria,4 include little information about the neurological status of the patient before WLST. Calculation of these scores requires temporary disconnection of the patient from the mechanical ventilator and the scores are tailored to assess the degree of pulmonary and circulatory support. These variables might be of less prognostic value in patients with catastrophic neurological injury who have not progressed to brain death than in patients with major non-neurological injury. This notion was reinforced by our previous analysis6 in which several respiratory and haemodynamic parameters were associated with death within 60 min of WLST on univariate analyses, but not on the multivariable analysis that included elements of a neurological examination. This single-centre study6 of 149 patients who were in coma with irreversible brain injury suggested that, after WLST, four clinical variables were associated with death within 60 min of extubation: absent corneal reflex, absent cough reflex, extensor or absent motor response, and higher oxygenation index. These associations were confirmed subsequently in a smaller, independent cohort.11

To further validate this approach, we undertook a prospective study to produce a new model to predict death within 60 min of WLST in patients with catastrophic cerebral damage, which was based on the previously described clinical variables. We aimed to develop a practical score for assessment of potential candidates for DCD.

Section snippets

Study design and participants

In this multicentre, observational study, we prospectively obtained data from consecutive adult, comatose patients with irreversible brain damage who underwent WLST at the intensive care units of six participating centres in the USA and the Netherlands. We enrolled patients in the study if anticipated death was attributable directly to severe brain injury (eg, massive head trauma, intracranial haemorrhage, ischaemic stroke with malignant oedema, or anoxic damage after cardiorespiratory arrest).

Results

Between March 30, 2010, and April 1, 2011, we assessed 178 patients. Table 1 summarises baseline characteristics of our study population. We enrolled 70 patients at the Mayo Clinic in Rochester (MN, USA), 39 at the Erasmus MC University Medical Center in Rotterdam (Netherlands), 30 at the University of Cincinnati (OH, USA), 17 at the Mayo Clinic in Jacksonville (FL, USA), 12 at Washington University in St Louis (MO, USA), and ten at the University of California, San Francisco (CA, USA).

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Discussion

When the decision to proceed with WLST is reached, medical teams in many countries contact local organ-procurement organisations to address the possibility of organ donation. In these situations, reliable identification of appropriate DCD candidates is essential for all concerned. Because catastrophic brain injury is the most common cause of death in patients who might be suitable for DCD, such methods should be especially applicable to patients in neurocritical state. In this study, we

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