Regional citrate anticoagulation in continuous venovenous hemodiafiltration.

Over the past several years, continuous venovenous hemodiafiltration (CVVHDF) using pump-driven devices has gained wide acceptance as a form of renal replacement therapy for critically ill patients with acute renal failure. More recently, regional citrate anticoagulation has proven useful as a method of anticoagulating CVVHDF circuits, particularly in those patients at high risk for bleeding. However, an easy and convenient method for guiding the dose of citrate infusion has not previously been described. We describe the use of an algorithm using posthemofilter levels of ionized calcium to guide the dose of administered regional citrate on the survival time and urea and creatinine clearances of 24 Hospal AN69HF hemofilters. Nine patients with acute and chronic renal failure requiring CVVHDF were studied. The median filter survival time when using the postfilter ionized calcium algorithm was 3.4 days, with a survival probability of 46% (95% confidence interval [CI], 17 to 71). Random-effects linear regression analysis did not show a significant decline in blood-side urea clearance (P = 0.041) or creatinine clearance (P = 0. 308). Moreover, definite bleeding complications occurred with an incidence rate of 0.045/person-day on citrate anticoagulation (95% CI, 0.006 to 0.16), and occult bleeding occurred with an incidence rate of 0.091/person-day on citrate anticoagulation (95% CI, 0.03 to 0.23). Guiding regional citrate anticoagulation through the use of posthemofilter ionized calcium levels is a safe and effective method of prolonging filter life during CVVHDF.

Energy expenditure associated with CPAP and T-piece spontaneous ventilatory trials. Changes following prolonged mechanical ventilation.

The use of portable metabolic carts to assess energy expenditure (EE) by measuring oxygen consumption (VO2) and carbon dioxide production (VCO2) has recently been applied to patients undergoing weaning from mechanical ventilation. The VO2 and EE can be used to estimate changes in the work of breathing (WOB) associated with different weaning strategies. The purpose of this study was to use VO2 and EE to assess changes in the WOB when assisted mechanical ventilation (AMV) was replaced with two spontaneous ventilatory trial (SVT) techniques: continuous positive airway pressure (CPAP) and T-piece. Nine difficult-to-wean patients were studied during the initial weaning period following 26 +/- 18 days (mean +/- SD) of mechanical ventilatory support. The VO2 and EE during all AMV were 296 +/- 75 ml/min and 2069 +/- 519 kcal/day, respectively. Compared to the baseline AMV levels, during CPAP overall VO2 and EE increased 14 percent and 13 percent, respectively, and during T-piece overall VO2 and EE increased 20 percent and 19 percent, respectively. Respiration rate (f) increased and tidal volume (VT) decreased during both SVTs compared to AMV although no significant change in minute ventilation was seen. The WOB, as judged from changes in VO2, was only 5 percent higher during T-piece compared to CPAP; however, patients tolerated an average of only 141 +/- 45 min on T-piece vs 165 +/- 29 minutes on CPAP. We conclude that during the initial weaning stages in patients who have received prolonged mechanical ventilatory support, the WOB associated with SVTs is increased compared to AMV but that the WOB associated with T-piece is not significantly greater than that for CPAP.

Loss of brainstem and pupillary reflexes in amoxapine overdose: a case report.

A case of severe Amoxapine overdose which presented with unusual neurologic signs and from which a complete recovery was attained is discussed.

Shock: an overview of pathophysiology and general treatment goals.

The shock syndromes continue to pose major problems for ICU physicians. Effective management is based on an appreciation of ten basic concepts that have evolved from both research and practical experience over the last 20 years. Despite advances in understanding and treatment, mortality continues to be related to the condition underlying the shock process.

Assisted ventilation in patients with preexisting cardiopulmonary disease. The effect on systemic oxygen consumption, oxygen transport, and tissue perfusion variables.

We have evaluated systemic oxygen consumption (VO2), systemic oxygen transport, and tissue perfusion variables in 30 patients with preexisting cardiac and underlying pulmonary disease during continuous positive-pressure ventilation and positive end-expiratory pressure [PEEP], during intermittent mandatory ventilation (IMV and PEEP), and during spontaneous ventilation (continuous positive airway pressure [CPAP]), with end-expiratory pressure held constant during all ventilatory modes. Using radionuclide angiography together with invasive determinations of pressure and flow, we also measured left and right ventricular ejection fractions and calculated the end-systolic (ESVI) and end-diastolic (EDVI) volume indices of both ventricles. We found that oxygen transport was significantly greater during CPAP (583 +/- 172 ml/min/M2)(mean +/- SD) than during either IMV and PEEP (543 +/- 151 ml/min/sq; p less than 0.01) or CPPV and PEEP (526 +/- 159 ml/min/M2; p less than 0.01); however, we found no significant change in systemic VO2 with conversion from CPPV and PEEP to CPAP. The increase in oxygen transport was related to a greater cardiac index and, more specifically, to a higher heart rate during CPAP (CPAP, 106 +/- 16 beats per minute; CPPV and PEEP, 97 +/- 14 beats per minute) (p less than 0.01). Enhanced oxygen transport during CPAP was also associated with an increase in mixed venous oxygenation and a decrease in arterial lactate. Although neither the mean left ventricular EDVI nor ESVI changed from CPPV and PEEP to CPAP, the mean pulmonary capillary wedge pressure increased (CPPV and PEEP, 12 +/- 5 mm Hg; CPAP, 14 +/- 7 mm Hg) (p less than 0.01), suggesting the possibility of a decrease in left ventricular compliance with the spontaneous ventilatory mode. This study suggests that in the absence of ventilatory failure, spontaneous ventilation provides for better systemic oxygen transport and overall tissue perfusion than either controlled ventilation or IMV; however, this benefit of enhanced oxygen delivery with spontaneous ventilation may potentially be offset by a decrease in left ventricular compliance.