Abstract
Background. For some surgical proce-dures a higher sensory block is needed. However, it is complicated by a higher in-cidence 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 American Society of Anaesthe-siologists (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.
Highlights
Patients have higher decreases in systemic vascular resistance during spinal anaesthesia compared to young patients, [24,25] some authors consider it as the main mechanism of hypotension in elderly, [26] besides this, in the aged heart there is less of a compensatory increase in heart rate and contractility, a compensatory increase in cardiac output is smaller than in young adults or there is even a decrease in CO
The level of sensory block was significantly higher in group H compared to group L (18.5 (95%cardiac index (CI) 17.9-19.1) vs 13.3 (95%CI 12.7-13.9) dermatomes above S5, p
In young, healthy patients no significant difference was found in haemodynamic parameters between a group with a high and a group with a low level of sensory block using the same dose of hyperbaric bupivacaine
Summary
Spinal anaesthesia is a safe and routinely used anaesthetic technique, it is related to various haemodynamic changes in the patient, most commonly hypotension. [1,2] The incidence of hypotension with a higher spinal block (Th7 or higher) appears to be as high as 60% or even more in elderly and obstetric population. [3,4,5] Hypotension may precede cardiac events [6] and increase 1-year postoperative mortality [7] many studies have focused on the prevention of hypotension due to spinal anaesthesia. [8] The underlying mechanism is the preganglionic sympathetic block and preserved or even increased parasympathetic nerve activity, [9] leading to a decreased systemic vascular resistance (SVR) and venodilatation, which causes a peripheral venous pooling of blood. [30] Based on the above literature, we came to a conclusion that there is a lack of studies that would examine the haemodynamic changes during spinal anaesthesia in healthy, younger subjects, which could provide the data for a better insight into the mechanisms of hypotension and would support the efforts to prevent it This is the first study in young healthy nonobstetric patients that compares a high to low spinal block with the same dose of hyperbaric local anaesthetic using the continuous non-invasive recording of haemodynamic parameters. In our study it was found that in young, healthy patients there are no significant differences in haemodynamic parameters and in incidence of hypotension between a high and low spinal block.
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