Norepinephrine-induced blood pressure increase to pre-shock levels worsens regional flow distribution in porcine septic shock

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Septic shock is characterized by hypotension, persisting after fluid replacement and requiring vasopressors. Mean arterial pressure (MAP) as endpoint of treatment providing adequate regional perfusion is unclear. In an acute endotoxic shock model, norepinephrine was used to reverse hypotension in seven fluid-resuscitated pigs, anesthetized with α-chloralose and equipped with flow probes around the portal vein and renal artery, renal and jejunal mucosal laser Doppler flowmetry and jejunal tonometry. MAP was increased by 10 and 20 mmHg above the shock level with norepinephrine. Seven shocked, fluid-resuscitated only animals served as control. Measurements were performed before 2 h-endotoxin infusion and at the end of each increased MAP level. Raising MAP with norepinephrine by 10 mmHg increased significantly cardiac output, systemic oxygen extraction, portal vein blood flow, improved metabolic balance and tended to restore renal and jejunal mucosal flows to pre-shock levels. Increasing MAP by 20 mmHg further increased cardiac output and oxygen delivery but reduced portal vein blood flow and tended to decrease renal and jejunal mucosal flows. In conclusion, using nor-epinephrine to increase MAP by 10 mmHg in volume-resuscitated, acutely septic animals improved systemic and regional perfusion. Higher MAP increase did not add any benefit despite an enhanced cardiac output.