Less fentanyl requirement by enteral methadone decreases mechanical ventilation duration and intensive care unit length of stay

Abstract

ObjectivesTo characterize an experimental model of pulmonary embolism by studying hemodynamics, lung mechanics and histopathologic derangements caused by pulmonary microembolism in pigs. To identify lung alterations after embolism that may be similar to those evidenced in pulmonary inflammatory conditions. Materials and methods Ten Large White pigs (weight 35-42 kg) were instrumented with arterial and pulmonary catheters, and pulmonary embolism was induced in five pigs by injection of polystyrene microspheres (diameter ~300 µM), in order to obtain a pulmonary mean arterial pressure of twice the baseline value. Five other animals injected with saline served as controls. Hemodynamic and respiratory data were collected and pressure x volume curves of the respiratory system were performed by a quasi-static low flow method. Animals were followed for 12 hours, and after death lung fragments were dissected and sent to pathology. Results Pulmonary embolism induced a significant reduction in stroke volume (71 ± 18 ml/min/bpm pre vs 36 ± 9 ml/min/bpm post, P < 0.05), an increase in pulmonary mean arterial pressure (27 ± 4 mmHg pre vs 39 ± 6 mmHg post, P < 0.05) and pulmonary vascular resistance (193 ± 122 mmHg/l/min pre vs 451 ± 149 mmHg/l/min post, P < 0.05). Respiratory dysfunction was evidenced by significant reductions in the PaO 2 /FiO 2 ratio (480 ± 50 pre vs 159 ± 55 post, P < 0.05), the dynamic lung compliance (27 ± 6 ml/cmH 2 O pre vs 19 ± 5 ml/cmH 2 O post, P < 0.05), the increase in dead space ventilation (20 ± 4 pre vs 47 ± 20 post, P < 0.05) and, the shift of pressure x volume curves to the right, with reduction in pulmonary hysteresis. Pathology depicted inflammatory neutrophil infiltrates, alveolar edema, collapse and hemorrhagic infarctions. Conclusion This model of embolism is associated with cardiovascular dysfunction, as well as respiratory injury characterized by a decrease in oxygenation, lung compliance and hysteresis. Pathology findings were similar to those verified in inflammatory pulmonary injury conditions. This model may be useful to study pathophysiology, as well as pharmacologic and ventilatory interventions useful to treat pulmonary embolism. P6 Hemodynamic and metabolic features of a porcine systemic low flow state modelObjective To describe a new experimental systemic low flow state model induced by cardiac tamponade. Methods Ten Large White pigs (43 ± 5 kg) were instrumented with arterial and pulmonary catheters, cystostomy and splenectomy, and a latex balloon was inserted anterior to the heart. Pigs were randomized to a shock group or a control group. The shock group had the balloon inflated with 620 ± 344 ml to keep the mean arterial blood pressure at 45-55 mmHg (mean = 49 ± 4 mmHg) for 1 hour. Hemodynamic data were collected and shown as the mean ± SD. Two-way ANOVA was used with Bonferroni's correction. Results During shock, the SvO 2 was 34 ± 8%, the heart rate was 173 ± 36 bpm, and the stroke volume was 18 ± 12 ml/min/beat. After shock, see Table 1. Conclusion In our model, transient...

Impact of Early Methadone Initiation in Critically Injured Burn Patients

“…15 To our knowledge, there are limited published data describing the role of methadone in the ICU. Wanzuita et al 16 assessed the ability of methadone to reduce fentanyl requirements in 16 patients and found a significant decrease in length of hospitalization (13 days vs 27 days; P < .02) and mechanical ventilation duration (4 days vs 20 days; P < .05). The same authors later presented a prospective, randomized, double-blind study involving patients fulfilling criteria for mechanical ventilation weaning and receiving prolonged infusions of fentanyl and found no significant difference in length of stay or mechanical ventilation duration.…”