Background: For some surgical procedures a higher sensory block is needed. How-ever, it is complicated by a higher inci-dence of hypotension, more bradycardia and nausea and a higher use of vasoactive drugs. In elderly and obstetric population complications have been attributed to the decrease in cardiac output and systemic vascular resistance, especially in a high block (above Th6). The aim of our study was to find the incidence of hypotension and bradycardia after a spinal anaesthesia in young, healthy patients. As young pa-tients compensate more, we aimed to find the difference in haemodynamic variables between the group with a high and the group with a low spinal block and the un-derlying mechanisms of hypotension. Methods: in a prospective, randomized study 44 ASA 1 patients scheduled for knee arthroscopy under spinal anaesthe-sia were randomly distributed to a high (group H) and a low (group L) spinal block group. In a group H patients were placed into horizontal, whereas in a group L in 15-degree anti-Trendelenburg posi-tion immediately after the spinal block. Haemodynamic parameters were meas-ured continuously noninvasively from 10 min before to 25 min after the spinal block using the CNAPTM device with the LiD-CORapid monitor.
Results: The differences in haemodynamic parameters between the groups were not statistically significant at all measured times despite a significant difference in the spinal block level (18.5 vs 13.3 dermato-mes above S5, p<0.001) and a significant difference in haemodynamic variables inside each group compared to the base-line value. With cardiac index (CI) as a dependent variable, a significant correla-tion between CI and stroke volume in-dex (SVI) was found (β=0.849, p<0.001) and also between CI and heart rate (HR) (β=0.573, p<0.001). In group H the inci-dence of hypotension was 35%, whereas in group L it was 10%. The same difference was seen in the use of phenylephrine be-tween the groups, however the difference was not significant.
Conclusion: In our study it was found that in young, healthy patients there are no significant differences in haemodynamic parameters and in incidence of hypoten-sion between a high and low spinal block. Young, healthy patients compensate a decrease in systemic vascular resistance caused by the spinal anaesthesia with a compensatory increase in CI resulting from an increase in SVI and HR. How-ever, a trend towards less hypotension, less bradycardia and less frequent phenyle-phrine use in a low spinal block was noted.