Influence of adrenergic drugs and volume loading on mean systemic filling pressure in non-septic and septic sheep.

OBJECTIVES: To outline the single and combined effects of adrenergic drugs and volume loading on mean systemic filling pressure (P msa ) in septic and non-septic sheep. METHODS: P msa was calculated based on cardiac output and the arterial and central venous pressures on 22 occasions during each of 44 experiments in non-septic and septic sheep. A bolus intravenous infusion of 20-25 mL/kg of crystalloid fluid was given together with continuous administration of phenylephrine, norepinephrine, isoprenaline, or dopamine during 150 min. Six non-septic and 5 septic sheep served as controls. RESULTS: P msa attained similar baseline values in the non-septic and septic sheep when no vasopressor was given (17.1 vs. 16.8 mmHg). The non-septic groups that received vasopressor showed higher P msa while the baseline values were generally lower in the septic sheep. Fluid loading effectively increased P msa in all groups except in the dopamine group with sepsis. Phenylephrine combined with fluid most effectively achieved and maintained a high P msa during sepsis. However, the average P msa during the 2.5-h experiment was 23% lower in the septic sheep (P = 0.007); this difference was mainly due to gradually decreasing P msa after volume loading in the noradrenaline group and to low P msa in dopamine-treated animals. CONCLUSION: P msa was lower during early sepsis than in the non-septic state but remained reasonably well preserved after fluid had been infused. The vasopressors exerted only a modest effect on P msa during sepsis.