The aim of this work was to establish the correlation between different rates of continuous infusion of propofol and the alterations that might occur with the physiologic parameters most commonly measured by the anesthesiologists.

Twenty-four adult dogs were randomly divided into 3 groups (P2, P4, P8). All animals were induced with propofol (10 mg/kg/IV), followed immediately by the continuous infusion of the agent: 0.2 mg/kg/min (P2), 0.4 mg/kg/min (P4) and 0.8 mg/kg/min (P8). The heart rate (HR), systolic, diastolic and mean arterial pressures (SAP, DAP and MAP), electrocardiography (ECG), respiratory rate (RR), and body temperature (T) were measured before any drug administration (M0) and 10, 20, 30, 40 and 50 minutes after the start of the continuous infusion of propofol. The numerical data were submitted to Analysis of Variance (p<0.05).

The HR showed differences among groups at M20 (P2: 91 ± 14,92; P4: 113 ± 17,18; P8: 120 ± 14,84), M30 (P2: 89 ± 13,79; P4: 110 ± 14,3; P8: 114 ± 10,9), and M40 (P2: 88± 17,3; P4: 103 ± 16; P8: 109 ± 8,2), which could be justified because P2 demonstrated minor reduction of MAP. There is no need of HR increasing to establish the cardiac output, and consequently, to maintain the AP.

We could observe a reduction of SAP about 26,9% to P2, 23,6% to P4 and 30,6% to P8; of PAP about 36,2 % to P2; 38,1% to P4 and 52,7% to P8; and of MAP about 32% to P2, 26,3% to P4 and 38,4% to P8. These reductions could be related to the decrease of peripheral vascular resistance. These minor values of arterial pressure were observed in P8 and the highest was observed in P2. This fact could be because pressure reduction is promoted by dose-dependent.

It was possible to observe, in all groups, a reduction of RR after the beginning of the infusion, with better efficiency to groups with higher doses.

It was possible to conclude that the decrease observed in SAP, DAP, MAP and RR are dependent on the propofol infusion rate.