The study flow diagram is presented in Figure 1. A total of 319 patients were evaluated for eligibility and offered enrolment in this study. Eighteen were excluded; 3 did not meet the inclusion criteria, 13 declined to participate, and 2 were excluded for other reasons. There were no failed or aborted blocks in either group. One patient in group U was lost to follow-up.
CONSORT flow diagram of the study. CONSORT indicates Consolidated Standards of Reporting Trials. Group U was short for nerve block with ultrasound guidance, group N was short for nerve block with nerve stimulation guidance, group M was for nerve block with combined guidance
The patient characteristics are presented in Table 1. There was no statistically significant difference in age, sex, weight or height among the three groups. Only one patient in group M had an ASA III status. Most of the operations were performed on the knee or ankle. There was a statistically significant difference in the operative time between group U (41.0 ± 24.21 min) and in group M (51.5 ± 30.8 min).
The primary and secondary outcomes are shown in Table 2. The incidence of LAST in all three groups was 6%. Moreover, there was a statistically significant difference in the incidence of LAST among the three groups. By multiple comparisons among the three groups, we found that the incidence of LAST in group U (12%) was significantly higher than that in group N (4%)(P = 0.037) and group M (2%)(P = 0.006). (shown in Table 4). Regarding the LPBs, the motor onset time was significantly shorter in group N (9.5 ± 3.55 s) than in group U (11.30 ± 4.94 s) and group M (11.10 ± 4.38 s) (shown in Table 2). There was no statistically significant difference in the sensory onset time or sensory and motor restoration time among the three groups. Regarding the SNBs, the motor and sensory onset time was significantly shorter in group N than in groups U and M. Meanwhile, the sensory and motor restoration time in group N was statistically significantly longer than that in groups U and M.
Detailed information of the 18 patients who developed LAST is summarized in Table 3. There were 12 patients from group U (66.7%), 4 from group N (22.2%) and 2 from group M (11.1%) who experienced LAST during the process. Most of the symptoms were CNS symptoms. None of the 18 patients developed permanent complications after correct and timely treatment. To our interest, 16 of the 18 patients were female. The age of the 18 patients ranged from 19 to 81. The shortest occurrence time was 1 min after finishing the block, and the longest occurrence time was 22 min. The shortest duration time was 3 min without any treatment. The longest duration time was 100 min due to the use of propofol.
We analysed risk factors such as age, sex, liver disease, and diabetes according to The Third American Society of Regional Anesthesia and Pain Medicine Practice Advisory on Local Anesthetic Systemic Toxicity. In the current study, 52 patients were infected with HBV, and 7 of these patients experienced LAST. As shown in Table 4, the OR of LAST for HBV infection and the female sex was 3.352(95% CI,1.233–9.108, P = 0.013) and 9.488(95% CI,2.142–42.093, P = 0.0004), respectively. However, age, needle passes, renal disease and diabetes did not increase the risk of LAST in the current study. Overall, the use of ultrasound, HBV infection and the female sex may be related to the increased incidence of LAST in the current study.
BMC Anesthesiol. 2019;19(103) © 2019 BioMed Central, Ltd.