Patients with end-stage renal failure scheduled for surgical creation of an arteriovenous fistula for haemodialysis are at risk of developing serious cardiovascular postanaesthetic complications . Brachial plexus block has been shown to improve blood flow through the vascular access and seems to be a suitable technique for this operation with minimal alteration in systemic homoeostasis . Ropivacaine is a long-lasting amide local anaesthetic. Its efficacy may be compared to bupivacaine but cardiovascular and central nervous system side-effects occur less frequently . The onset time, duration of action and success rate of peripheral nerve blockade are commonly used as efficacy parameters when different local anaesthetics are compared. Similarly the stability of haemodynamic and respiratory parameters during anaesthesia is widely considered to be an indicator of safety of anaesthesia. The aim of this prospective study was to compare supraclavicular brachial plexus block with 0.75% ropivacaine and 0.5% bupivacaine for the creation of vascular access in patients with end-stage renal failure.
With Ethics Committee approval we studied 50 ASA II-III patients scheduled for creation of an arteriovenous fistula for haemodialysis. Patients with coagulopathy, local skin infection and allergy to local anaesthetics were excluded. The patients were randomly allocated into two equal groups. In Group 1 (14 males and 11 females, mean age 58 ± 15 yr) a supraclavicular brachial plexus block was performed using 30 mL of plain 0.5% bupivacaine and in Group 2 (15 males and 10 females, mean age 55 ± 14 yr) the same block was performed using 30 mL of plain 0.75% ropivacaine. Nerve blockade was placed by means of a nerve stimulator (Stimuplex Dig RC, B. Braun, Germany). The onset of sensory and motor block was evaluated every 5 min until surgical anaesthesia was achieved and every hour after the end of surgery until the complete regression of the regional blockade. An ice test was performed to assess a sensory blockade. Complete temperature insensitivity was defined as a loss of temperature sensation in the area of the planned operation. Surgical anaesthesia was achieved when the patient showed complete loss of temperature sensation in the surgical field with the concomitant inability to elevate the operated limb. The onset of sensory and motor blockade was measured as the time from the completion of the injection of local anaesthetic to the achievement of surgical block. The duration of sensory or motor blockade was measured as the time from surgical anaesthesia to the return of sensation of temperature and patient's ability to elevate the limb. Heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP), oxygen saturation and respiratory rate were recorded every 5 min. Maximal and minimal values of these parameters were taken for statistical analysis. Patients and surgeons also evaluated the quality of anaesthesia after the procedure with a 4-point verbal rating scale score (very good, good, satisfactory, unsatisfactory). After testing for normal distribution with the Kolmogorov-Smirnov test, patient data were analysed using the t-test. Because of the small number of patients in both groups (<30) the results were confirmed using the U-test. Gender distribution was analysed with the χ2-test. Results are expressed as the mean and standard deviation (SD), standard error of mean (SEM) or percentage. P < 0.05 was considered as statistically significant.
The two groups were comparable with respect to age, gender and demographic data. Sufficient block was achieved in the majority of patients. There were four failed blocks in the study. Two patients in Group 1 and two patients in Group 2 required supplemental analgesia and were excluded from the statisitical analysis. The onset time of sensory blockade was 22.4 ± 7.3 min in Group 1 and 19.7 ± 5.9 min in Group 2. The duration time of sensory block was 8.8 ± 3.2 h in Group 1 and 7.5 ± 2.6 h in Group 2. The time required to achieve motor blockade was 33.7 ± 10.1 min in Group 1 and 34.1 ± 12.6 min in Group 2. The only difference was found in the duration of motor block; in Group 1 it was 9.5 ± 3.2 h and in Group 2 7.6 ± 3.1 h (P < 0.05) (Fig. 1). The mean values of maximal and minimal BP, HR, oxygen saturation and respiratory rate are shown in Table 1. The minimal value of DBP in Group 2 was significantly higher than in Group 1 (Fig. 2). The quality of anaesthesia in both groups in all cases was classified by the surgeons as ‘very good’. Patients' opinions were found to be similar. In Group 1, the quality of anaesthesia was described as ‘very good’ in 19 patients and ‘good’ in 4 patients compared to 17 and 6 patients, respectively in Group 2 (P > 0.05). No side-effects were observed.
Bupivacaine remains the most commonly used long-acting local anaesthetic. Ropivacaine with its fast onset, long duration and minimal toxicity profile offers an alternative to bupivacaine for long-acting nerve block. The results of our study suggest that 0.5% bupivacaine and 0.75% ropivacaine both provide a similar onset time of sensory and motor blockade. The duration of sensory blockade was also comparable between groups but the recovery time of motor blockade was significantly quicker when ropivacaine was used. Klein and colleagues compared the activity of 0.75% ropivacaine, 0.5% ropivacaine and 0.5% bupivacaine for brachial plexus block and found no difference in their clinical effect. The authors claimed that 0.75% ropivacaine did not cause a faster onset of sensory blockade or better anaelgesia as they had expected . McGlade and colleagues compared brachial plexus block with the use of 0.5% plain solutions of ropivacaine and bupivacaine. They noted that the quality of anaesthesia was similar, however the motor blockade lasted statistically longer when bupivacaine was used . Raeder and colleagues showed that 0.75% ropivacaine used for axillary block resulted in better anaesthesia when compared with the same volume of 0.5% bupivacaine. However the onset and the duration of the blockade were similar in both groups . We observed, in both groups of patients, good haemodynamic and respiratory stability. Higher values of minimal DBP in the group of patients where ropivacaine was administered may account for local vasoconstrictive activity of the anaesthetic . No adverse effects requiring intervention were noted. Pere and colleagues compared the pharmacokinetic profile of ropivacaine for brachial plexus blockade in healthy patients with patients suffering from uraemia and showed that even high doses of ropivacaine were well tolerated by patients with renal failure .
We conclude that there is no clinically important difference between using 0.75% ropivacaine and 0.5% bupivacaine for supraclavicular brachial plexus block when considering such efficacy parameters as the onset and the duration time of nerve blockade and the quality of analgesia. The minimal cardiovascular toxicity of ropivacaine may offer an advantage in patients with end-stage renal failure.
H. D. Misiolek
H. J. Kucia
M. M. Werszner
J. W. Karpe
*Department of Anaesthesiology and Intensive Therapy, Silesian School of Medicine, Zabrze, Silesia, Poland
†Department of Internal Diseases, Nephrology and Diabetology, Silesian School of Medicine, Zabrze, Silesia, Poland
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