Systemic and renal actions of dopexamine and dobutamine during endotoxin shock in the rat

Noninvasive functional liver blood flow measurement: comparison between bolus dose and steady-state clearance of sorbitol in a small-rodent model

Plasma clearance of D-sorbitol, a nontoxic polyol, occurs predominantly in the liver and has been used to measure functional liver blood flow after bolus and steady- state intravenous administration. However, it is not known which of these two administration methods is superior. Therefore, plasma D-sorbitol clearance was studied in an animal model both after a bolus dose and under steady-state (SS) conditions and compared directly with liver blood flow, under normal conditions, and after the induction of endotoxin (LPS) sepsis. Adult male Wistar rats (526 +/- 38 g body wt; n = 27) were anesthetized and mechanically ventilated. Hemodynamics, hepatic arterial flow, and portal venous flow were measured. Two groups were studied, namely healthy animals that served as controls and a sepsis group that received 5 mg/kg LPS intravenously (Escherichia coli O127:B8). Each animal received either a SS infusion (0.1 mg/100 g body wt per min) or a bolus (3 mg/100 g body wt) of a 5% D-sorbitol solution intravenously in a randomized order. After the initial measurements and a 60-min pause time in between (T(1/2,sorbitol) = 9 min), a crossover was done. The hepatic clearance of D-sorbitol in the control group showed a good correlation between bolus and SS (Spearman's r = 0.7681, P = 0.0004), and both techniques correlated well with total liver blood flow (TLBF) (r = 0.7239, P = 0.0023 and r = 0.7226, P = 0.0023, respectively). Also in the sepsis group there was a good correlation between bolus and SS sorbitol clearance (r = 0.6655, P = 0.0182). In the sepsis group, only the SS clearance correlated with TLBF (r = 0.6434, P = 0.024). In conclusion, in normal and under septic conditions, hepatic clearance of D-sorbitol either by bolus or a SS infusion is comparable. In healthy animals, this also correlated well with TLBF but not in septic conditions. However, this is expected because of the changes in the liver microcirculation, shunting, and decreased hepatocyte function in sepsis.

Effects of dopamine, dopexamine and dobutamine on renal excretory function during experimental sepsis in conscious rats

BACKGROUND

Acute renal failure is a frequent complication in human sepsis. Various inotropic drugs are often used to improve central haemodynamics and renal function. The differential preservative role of the most commonly used inotropic drugs on renal function, in this condition, has previously not been extensively studied. The aim of this experimental animal study was therefore to compare the preserving effects of dopamine, dopexamine, dobutamine and saline on renal excretory function, after induction of sepsis in conscious rats.

METHOD

The effects of dopamine (DA) (2.5 micrograms.kg-1.min-1; n = 11), dopexamine (DX) (1 microgram.kg-1.min-1; n = 10), dobutamine (DB) (5 micrograms.kg-1.min-1; n = 10) and saline (n = 13) on the glomerular filtration rate (GFR), urine flow (UF), sodium excretion (SE) and fractional urinary excretion of sodium (FUENa) were studied and compared in conscious rats subjected to a 1-h infusion of live E. coli bacteria (10(9)/h).

RESULTS

In the saline-treated control group, bacteria infusion decreased GFR, UF, SE and FUENa by 31%, 53%, 51% and 36% respectively, associated with a 16% decrease in mean arterial pressure (MAP), and a 10% increase in heart rate (HR). In the post-E. coli treatment period, the fall in MAP was less pronounced with DX compared to both DB and control, while there was no difference between DX and DA. The increase in HR was most pronounced with DB. GFR decreased to a lesser extent with DX compared to DA, DB and control. UF and SE were better maintained with DX compared to DB and control, while there was no difference in FUENa between the groups.

CONCLUSION

We conclude that dopexamine, to a greater extent than dopamine and dobutamine, improves renal excretory function in experimental septic shock.

Organ blood flow and distribution of cardiac output in dopexamine- or dobutamine-treated endotoxemic rats

Endotoxemia causes a decrease of blood flow to most organs. If this could be prevented, chances of survival might improve. In endotoxemic rats, we studied the effect of a therapeutic infusion of dopexamine (dopaminergic, beta 2-adrenergic) on blood flow and percentage of the cardiac output distributed to heart, brain, hepatic artery, stomach, intestines, spleen, pancreas, kidneys, adrenals, diaphragm, skeletal muscle, and skin. Dopexamine action was compared with that of dobutamine (beta 1-adrenergic). Endotoxin shock was induced in 28 rats with infusion of 8 mg/kg Escherichia coli O127:B8 endotoxin from 0 to 60 minutes; the rats were then divided into 3 groups, which received from 60 to 135 minutes of an infusion of saline (ES; n = 10), dopexamine hydrochloride (DX, 3 x 10(-8) mol/kg.min; n = 10) or dobutamine (DB, 10(-7) mol/kg.min; n = 8). A fourth group served as time-matched controls (C, saline from 0 to 135 minutes; n = 8). In the untreated endotexemic rats, cardiac output decreased and organ blood flow decreased except in the diaphragm, heart, and brain; the percentage of the cardiac output to those organs increased. Dopexamine and dobutamine similarly improved cardiac output in endotoxemic rats. All organs benefitted to the same extent from the increased cardiac output. Therapeutic infusion of dopexamine during endotoxemia did not favor flow to any particular organ; redistribution of cardiac output changed little after administration of dopexamine, and its effects were not significantly different from those of dobutamine.