Key result
Alpha receptor blockade during positive end-expiratory pressure caused alarming decreases in mean arterial pressure and regional blood flows in pigs receiving low fluids, which was partially mitigated by higher fluid administration.
Why the study?
Does alpha adrenergic blockade alter central hemodynamics and regional blood flows during positive pressure ventilation in pigs?
Does alpha adrenergic blockade alter central hemodynamics and regional blood flows during positive pressure ventilation in pigs?
Alpha-adrenergic blockade during positive pressure ventilation severely compromises hemodynamics and regional blood flow, which is only partially mitigated by higher fluid administration.
Answers are grounded in this paper and cite their sources.
Alpha blockade during PEEP may impair hemodynamics in low-volume states; leaves open translation to human positive-pressure ventilation.
The effects of alpha receptor blockade on cardiac output distribution in pigs were studied. Recordings were made during spontaneous breathing (SB), during ventilator treatment with 8 Pa positive end-expiratory pressure (8 PEEP), after alpha blockade during SB (SB-alpha) and at 8 PEEP (8 PEEP-alpha). The microsphere method was used for blood flow determinations. The animals received either 5 ml.kg-1.h-1 (Group A) or 10 ml.kg-1.h-1 (Group B) of fluids. In Group A on SB-alpha, CO was maintained due to tachycardia but mean arterial pressure (MAP) decreased, renal blood flow and urine production decreased. At 8 PEEP-alpha, CO decreased despite increased heart rate (HR), MAP decreased alarmingly, renal blood flow decreased, urine production ceased and cerebral blood flow decreased, reflecting failing autoregulation. In Group B, CO increased during SB-alpha, SVR decreased, myocardial blood flow increased and organ blood flows were otherwise unchanged. At 8 PEEP-alpha, MAP, SVR, renal, pancreatic and splenic blood flows decreased in Group B. Gastric, intestinal and muscular blood flows were unchanged at 8 PEEP-alpha in Group B which is interpreted as an effect of the alpha blockade. In both groups peripheral arterio-venous shunting increased after alpha blockade.
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Feuk et al. (1987) studied Positive pressure ventilation. Alpha receptor blockade vs. Baseline (without alpha blockade) was evaluated on Cardiac output distribution, central haemodynamics, and regional blood flows. Alpha receptor blockade during positive end-expiratory pressure caused alarming decreases in mean arterial pressure and regional blood flows in pigs receiving low fluids, which was partially mitigated by higher fluid administration.
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