John C. Fenwick

Diastolic filling in human severe sepsis: an echocardiographic study.

OBJECTIVE To determine if nonsurvivors have a more abnormal pattern of left ventricular relaxation than survivors with severe sepsis. DESIGN Prospective, observational, cohort study. SETTING Intensive care unit in a university-affiliated tertiary care hospital. PATIENTS Twenty-four adults with severe sepsis. INTERVENTIONS None. MEASUREMENTS AND MAIN RESULTS Baseline clinical and hemodynamic variables, Acute Physiology and Chronic Health Evaluation (APACHE) II scores and Doppler echocardiographic mitral inflow pattern (analyzed for normalized peak early filling rate [E/VTI, systolic volumes/sec], deceleration time [msec], and early to atrial filling velocity ratio [E/A]). There were seven deaths. The patients did not differ in baseline demographics, inotropic infusions, hemodynamic measurements or ventilatory settings or variables. Nonsurvivors had a more abnormal pattern of left ventricular relaxation (E/VTI, 4.7 [range 3.8 to 5.8] vs. 5.8 [range 3.8 to 8.9], p= .04; deceleration time, 235 [range 209 to 367] vs. 182 [range 155 to 255], p = .002). E/A showed a nonsignificant trend in the same direction (0.9 [range 0.8 to 1.6] vs. 1.2 [range 0.7 to 1.9], p = .12). In a multivariate analysis, deceleration time (p< .004) and APACHE II score (p < .02) were the only independent predictors of mortality. CONCLUSION Severe sepsis nonsurvivors have a more abnormal echocardiographic pattern of left ventricular relaxation than survivors.

Severity of illness and risk of death associated with pulmonary artery catheter use

ObjectiveTo examine the association between the use of the pulmonary artery catheter and mortality rate in critically ill patients with a higher vs. a lower severity of illness. DesignObservational cohort study. SettingA tertiary care university teaching hospital from March 1988 to March 1998. PatientsA total of 7,310 critically ill adult patients. InterventionsNone. Measurements and Main ResultsThe main outcome measure was hospital mortality rate, controlled by multivariable logistic regression within four patient groups based on severity of illness. Cutoffs for severity of illness were chosen based on Acute Physiology and Chronic Health Evaluation (APACHE) II score 25th percentiles. Logistic regression analysis demonstrated no increased risk of death associated with exposure to the pulmonary artery catheter in the population as a whole. The associated odds ratio of hospital death for the entire cohort was 1.05 (95% confidence interval, 0.92–1.21). Subgroup analysis of severity of illness revealed the highest risk of death to be associated with the lowest APACHE II score quartile vs. a decreased associated mortality rate with the highest APACHE II score quartile after adjustment with multivariable logistic regression (APACHE II <18: odds ratio, 2.47, 95% confidence interval, 1.27–4.81; APACHE II 18–24: odds ratio, 1.64, 95% confidence interval, 1.24–2.17; APACHE II 25–31: odds ratio, 1.00, 95% confidence interval, 0.80–1.24; APACHE II >31: odds ratio, 0.80, 95% confidence interval, 0.64–1.00). ConclusionsThe use of the pulmonary artery catheter may decrease mortality rate in the most severely ill while increasing it in a population with a lower severity of illness. These findings underscore the necessity of examining the effect of severity of illness in future randomized controlled trials.

Increased concentrations of plasma lactate predict pathologic dependence of oxygen consumption on oxygen delivery in patients with adult respiratory distress syndrome

Abstract We asked whether increasing systemic oxygen delivery by blood transfusion could identify pathologic dependence of oxygen consumption on oxygen delivery in patients who have adult respiratory distress syndrome (ARDS) with and without increased concentrations of plasma lactate. Twenty-four ARDS patients were divided into normal (n = 11, lactate ≤ 1.8 mmol/L) and increased (n = 13, lactate > 1.8 mmol/L) plasma lactate groups. After transfusion of two units of packed red blood cells, oxygen delivery index increased significantly in both the normal and increased plasma lactate groups. In the increased plasma lactate group, this was associated with a significant increase in oxygen consumption index and an unchanged oxygen extraction ratio. In contrast, in the normal plasma lactate group, oxygen consumption index did not change from the baseline value and the oxygen extraction ratio decreased significantly. We conclude that increasing systemic oxygen delivery by blood transfusion identifies pathologic dependence of oxygen consumption on oxygen delivery in patients who have ARDS and increased concentrations of plasma lactate.

Blood transfusion as a cause of leucocytosis in critically ill patients

The diagnosis of infection in the intensive care unit is confounded by the presence of non-infectious causes of leucocytosis. Unless such causes are recognised, time and effort will be spent on unnecessary investigations and treatments. In a prospective study we have shown that the transfusion of blood frequently (45/50 patients) causes an acute leucocytosis in such patients. This effect was not seen in 8 patients who received plasma. Blood transfusion should be added to the list of non-infectious causes of leucocytosis in the critically ill.

Acute quadriparesis in an asthmatic treated with atracurium

An 18-yr-old male asthmatic was paralyzed with atracurium for a period of seven days to facilitate mechanical pulmonary ventilation. After withdrawal of the muscle relaxant, train-of-four neuromuscular monitoring demonstrated rapid recovery of normal function. Three days later he developed acute quadriparesis without respiratory compromise. Electrophysiological studies showed normal conduction velocities, low compound muscle action potential amplitudes and evidence of denervation. Most cases of post-ventilatory weakness in the ICU involve the use of vecuronium and pancuronium. It has been suggested that the steroid nucleus in these muscle relaxants may be responsible. Our patient developed generalised weakness after treatment with atracurium, a benzylisoquinolinium muscle relaxant. Thus, it appears that the steroid nucleus of vecuronium and pancuronium is not essential in causing post-ventilatory weakness.RésuméUn asthmatique de 18 ans est curarisè à l’atracurium pendant sept jours pour la ventilation mécanique. Après l’arrêt du myo-relaxant, la fonction neuromusculaire telle qu’évaluée au train-de-quatre récupère rapidement. Trois jours plus tard, le patient devient subitement quadriplégique sans atteinte respiratoire. A l’électrophysiologie, les vélocités de conduction sont normales, les composantes des potentiels d’action sont de faible amplitude et la dénervation est évidente. A l’unité de soins intensifs, la majorité des cas de faiblesse ventilatoire survient avec le vécu-ronium et le pancuronium. La cause du problème est ordinairement attribuée au noyau stéroïde de ces relaxants. Dans le cas présent, la faiblesse généralisée est survenue après un traitement à l’atracurium qui est dérivé du benzylisoquinolinium. Il ne semble donc pas que le noyau stéroïde du vécu-ronium et du pancuronium puisse être considéré comme le facteur essentiel de la faiblesse post-ventilatoire.

Number of deaths by neurological criteria, and organ and tissue donation rates at three critical care centres in Canada

PurposeComparative organ donation rates are expressed per million population and by this measurement, Canada lags behind other countries. These estimates do not account for differing demographics and health patterns of populations which can result in different rates of death by neurological criteria and subsequent donation rates. We sought to measure directly the number of deaths by neurological criteria, the associated donation rates, and the reasons for the differences.MethodsA prospective evaluation of deaths by neurological and cardiorespiratory criteria in the critical care areas of three major adult Canadian tertiary care centres over a seven month period was undertaken. Patients were assessed for eligibility for organ and tissue donation and ultimate disposition.ResultsAnnualized rates of death by neurological criteria varied from 2.3%-7.5% (8.6-28 patients) of all deaths. Conversion to actual donors ranged from 20-86%, with family refusal rates accounting for most of this variation. There were only three cases of suspected death by neurological criteria where a complete examination was not performed.ConclusionsThere is substantial geographic variability in the rate of neurological death and actual organ donation rates in these Canadian tertiary care centres. These variations are principally related to regional differences in demographics of brain injury, referral patterns and donation consent rates, rather than lack of identification of potential donors.RésuméObjectifLes taux comparatifs de don d’organe sont donnés par million d’individus et, suivant cette mesure, le taux canadien est inférieur à celui d’autres pays. Ces taux n’expliquent pas la variété des données démographiques et des modèles de soins des populations pouvant fournir différents taux de mort neurologique et de don subséquent. Nous voulions évaluer directement le nombre de morts neurologiques, les taux de don associé et les raisons des différences.MéthodeUne évaluation prospective des morts neurologiques et cardiorespiratoires, survenues au cours d’une période de sept mois dans trois grands centres tertiaires canadiens pour adultes, a été entreprise. Les patients ont été évalués en fonction de l’admissibilité au don d’organe et de tissu, et de leurs dernières volontés.RésultatsLe taux de mort neurologique annualisé variait de 2,3 % - 7,5 % (8,6 - 28 patients) de tous les décès. La conversion des taux en donneurs réels allait de 20 à 86 %, le refus des familles comptant le plus dans cette variation. Il n’y a eu que trois cas de mort neurologique présumée où un examen complet n’avait pas été fait.ConclusionLe taux de mort neurologique et le taux réel de don d’organes varient beaucoup dans les centres canadiens étudiés. C’est surtout lié aux différences régionales de données démographiques sur les lésions cérébrales, de manières de diriger les patients vers les services et de taux de consentement au don plutôt qu’au défaut de reconnaître les donneurs potentiels.