Do fluid administration and reduction in norepinephrine dose improve global and splanchnic haemodynamics?

We studied global and splanchnic haemodynamics in patients with septic shock, while reducing norepinephrine doses by progressive fluid loading administration. Ten patients (six female, four male, aged 39-86 yr, mean 61 yr) were assessed using a transpulmonary thermo-dye dilution technique to measure cardiac output, intrathoracic blood volume and total blood volume. Splanchnic blood flow was measured by the steady state indocyanine green technique using a hepatic venous catheter. Gastric mucosal blood flow was estimated by regional carbon dioxide tension (PRCO2). Hydroxyethylstarch was infused in two stages while maintaining mean arterial pressure, allowing a reduction in norepinephrine dose from 0.54 to 0.33 to 0.21 microgram kg-1 min-1. Mean (SD) heart rate significantly decreased, from 104 (13) to 94 (15) beats min-1. Total blood volume index (mean (SD)) increased from 2650 (638) to 3655 (885) ml m-2, intrathoracic blood volume index from 888 (204) to 1050 (248) ml m-2 and cardiac index from 3.6 (1.0) to 4.0 (0.9) litres min-1 m-2. Splanchnic blood flow did not change significantly--either absolute (from 0.81 to 0.98 litres min-1 m-2) or fractional (from 22.3% to 23.9%). Gastric mucosal (PRCO2) increased from 7.5 (2.5) to 9.0 (2.8) kPa. The PCO2 gap, i.e. the difference between regional and end-tidal PCO2, increased from 3.1 (2.5) to 4.0 (2.9) kPa. Marked individual variation in responses suggests that norepinephrine dose reduction by fluid loading in patients with stabilized septic shock does not necessarily increase global or splanchnic blood flow.