The effect of Trendelenburg position, lactated Ringer's solution and 6% hydroxyethyl starch solution on cardiac output after spinal anesthesia.

BACKGROUND

The aim of our study was to evaluate the effects of Trendelenburg position, infusion of 6% hydroxyetyl starch solution or lactated Ringer's solution on changes in cardiac output (CO) after spinal anesthesia in patients older than 50 yr.

METHODS

Seventy patients scheduled for lower extremity orthopedic surgery under spinal anesthesia were allocated randomly to one of the three treatment groups. In the Trendelenburg group, the patients were placed in the Trendelenburg position immediately after the spinal block for 10 min. In the hydroxyethyl starch group and the lactated Ringer's group, the patients received an infusion of 500 mL of 6% hydroxyethyl starch solution or 1000 mL of lactated Ringer's solution over 20 min after the spinal block. CO was measured continuously from 15 min before until 30 min after spinal anesthesia using the impedance cardiography method and arterial blood pressure with an automated device. P < 0.05 was considered statistically significant.

RESULTS

The differences among treatment groups in CO were not statistically significant. Differences in the CO changes from baseline over time were significant. In the Trendelenburg group, CO did not change while the patient was in the Trendelenburg position. In the hydroxyethyl starch group, CO increased significantly after the block and remained significantly increased until the end of measurements. In the lactated Ringer's group, CO increased significantly 10 and 20 min after the block but, after stopping the infusion, CO started to decrease.

CONCLUSIONS

Our study demonstrated that a decrease in CO after spinal anesthesia is prevented by placing the patient in the Trendelenburg position, or infusion of either lactated Ringer's solution or 6% hydroxyetyl starch solution. Although the effects of the infusion of the lactated Ringer's solution are transient, the effects of the infusion of 6% hydroxyethyl starch solution are extended beyond the time the infusion.