Alan H. Yee

Cerebral Salt Wasting: Pathophysiology, Diagnosis, and Treatment

Cerebral salt wasting (CSW) is a syndrome of hypovolemic hyponatremia caused by natriuresis and diuresis. The mechanisms underlying CSW have not been precisely delineated, although existing evidence strongly implicates abnormal elevations in circulating natriuretic peptides. The key in diagnosis of CSW lies in distinguishing it from the more common syndrome of inappropriate secretion of antidiuretic hormone. Volume status, but not serum and urine electrolytes and osmolality, is crucial for making this distinction. Volume and sodium repletion are the goals of treatment of patients with CSW, and this can be performed using some combination of isotonic saline, hypertonic saline, and mineralocorticoids.

Pilot Randomized Trial of Outpatient Cardiac Monitoring After Cryptogenic Stroke

Background and Purpose— Observational studies indicate that outpatient cardiac monitoring detects previously undiagnosed atrial fibrillation (AF) in 5% to 20% of patients with recent stroke. However, it remains unknown whether the yield of monitoring exceeds that of routine clinical follow-up. Methods— In a pilot trial, we randomly assigned 40 patients with cryptogenic ischemic stroke or high-risk transient ischemic attack to wear a Cardionet mobile cardiac outpatient telemetry monitor for 21 days or to receive routine follow-up alone. After thorough investigation, we excluded patients with documented AF or other apparent stroke pathogenesis. We contacted patients and their physicians at 3 months and at 1 year to ascertain any diagnoses of AF or recurrent stroke or transient ischemic attack. Results— The baseline characteristics of our cohort broadly matched those of previous observational studies of monitoring after stroke. In the monitoring group, patients wore monitors for 64% of the assigned days, and 25% of patients were not compliant at all with monitoring. No patient in either study arm received a diagnosis of AF. Cardiac monitoring revealed AF in zero patients (0%; 95% confidence interval, 0%–17%), brief episodes of atrial tachycardia in 2 patients (10%; 95% confidence interval, 1%–32%), and nonsustained ventricular tachycardia in 2 patients (10%; 95% confidence interval, 1%–32%). Conclusions— In the first reported randomized trial of cardiac monitoring after cryptogenic stroke, the rate of AF detection was lower than expected, incidental arrhythmias were frequent, and compliance with monitoring was suboptimal. Our findings highlight the challenges of prospectively identifying stroke patients at risk for harboring paroxysmal AF and ensuring adequate compliance with cardiac monitoring. Clinical Trial Registration— URL: http://clinicaltrials.gov. Unique Identifier: NCT00715533

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

BACKGROUNDnSuccessful 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.nnnMETHODSnIn 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.nnnFINDINGSnWe 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).nnnINTERPRETATIONnThe 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.nnnFUNDINGnNone.

Factors influencing time to death after withdrawal of life support in neurocritical patients

Objective: Improving our ability to predict the time of death after withdrawal of life-sustaining measures (WLSM) could have a significant impact on rates of organ donation after cardiac death and allocation of appropriate medical resources. We sought to determine which pre-WLSM clinical factors were associated with earlier time to death in patients with catastrophic neurologic disease. Methods: We retrospectively analyzed all patients who underwent WLSM from 2002 to 2008 in a neurologic intensive care unit. Individuals who died within 60 minutes were compared to those who died beyond this time from the point of WLSM. Patients declared brain dead or not intubated and cases with insufficient data were excluded. Demographic, clinical, laboratory, and radiographic data were reviewed. Statistical analysis was based on multivariate logistic regression. Results: A total of 149 comatose patients satisfied our inclusion criteria. A total of 75 patients had cardiac arrest in <60 minutes; 57% were male and 52% were older than 66 years. Ischemic stroke (30%) and intraparenchymal hemorrhage (52%) were the most frequent diagnoses. Absent corneal (odds ratio [OR] = 4.24, 95% confidence interval [CI] 1.57–11.5, p = 0.005) and cough reflexes (OR = 4.46, 95% CI 1.93–10.3, p = 0.0005), extensor or absent motor response (OR = 2.83, 95% CI 1.01–7.91, p = 0.048), and an oxygenation index greater than 4.2 (OR = 3.36, 95% CI 1.33–8.5, p = 0.011) were associated with earlier death. Conclusions: Specific neurologic signs and respiratory measurements are associated with earlier death after withdrawal of life-sustaining measures in the neurologic intensive care unit. This subset of comatose patients with irreversible neurologic injury may be suitable for organ donation after cardiac death protocols. These attributes need validation in a prospective data set.

Predictors of Apnea Test Failure During Brain Death Determination

Background In a recent publication (Wijdicks et al. in Neurology 71(16):1240, 2008), apnea test safety during brain death determination was evaluated at a single tertiary care center. One major conclusion was that apnea testing was safe in hemodynamically compromised patients in most circumstances and rarely aborted. Determinants of apnea test completion failure are unknown.MethodsA–a gradients and

Neurologic Presentations of Acid-Base Imbalance, Electrolyte Abnormalities, and Endocrine Emergencies

{{P_{{{text{a}}_{{{text{O}}_{ 2} }} }} } mathord{ /{vphantom {{P_{{{text{a}}_{{{text{O}}_{ 2} }} }} } {F_{{{text{i}}_{{{text{O}}_{ 2} }} }} }}} kern-nulldelimiterspace} {F_{{{text{i}}_{{{text{O}}_{ 2} }} }} }}

Arteriovenous fistula after ventriculostomy in aneurysmal subarachnoid hemorrhage

ratios were calculated in the previously studied cohort. Arterial blood gas (ABG) values and systolic blood pressures (SBP) were recorded prior to apnea test initiation. Patients that completed the procedure during the declaration of brain death were compared to those whose studies were aborted. Statistical analysis was performed using Wilcoxon rank-sum and Fisher’s exact tests where appropriate. Aborted apnea test risk factor assessment was by logistic regression analysis.Results207 of the original 228 patients were evaluated. 10 of the 207 patients had aborted apnea tests because of hypoxemia and/or hypotension. 60% who failed the apnea test were male and were of younger age [median: 23xa0years vs. median: 47xa0years (Pxa0=xa00.02)]. A–a gradient median values for aborted and completed apnea tests were 376 and 175xa0mmHg, respectively (Pxa0=xa00.003). Neither the