Methods A total of 102 primiparae were selected from January 30, 2017 to January 10, 2018 in Shenzhen Baoan Maternal and Child Health Hospital. The 120 primiparae were randomly divided into two groups: observation group (n=52) and control group (n=50) by digits table method. The two groups were treated with continuous epidural anesthesia for labor analgesia, and the local anesthetics used in the two groups were the same, but the temperature of local anethetics were different. The local anesthetics in the control group were at room temperature (24 ℃), while the local anesthetics in the observation group were preheated to human body temperature (37 ℃). The analgesic effects and adverse reactions were observed in the two groups. The body temperatures and visual analogue scale (VAS) scores were compared at different time points before and after analgesia between the two groups by the variance analysis of repeated measurement data. Incidences of fever, chills, hypotension, nausea and vomiting, pruritus and total adverse reactions were compared by chi-square test or continuity correction of chi-square test. The procedures followed in this study was in accordance with the ethical standards established by the Human Beings Test Committee of Shenzhen Baoan District Maternal and Child Health Hospital, and was approved by the committee (Approval No. QKTLL-2017-04-11). And the clinical research informed consent form was signed with each primipara.
Results ①There were no significant differences between two groups in the age, body weight, length of dilatation of cervix before analgesia and body temperature at admission (P>0.05). ②The onset time of analgesia in observation group was (11.0±1.3) min, which was obviously shorter than (13.1±2.0) min of control group, and the difference was statistically significant (t=6.559, P<0.001). ③The VAS scores of 5 min before analgesia and 15 min, 30 min after analgesia in observation group were (9.30±0.42) points, (2.02±0.12) points, and (1.16±0.13) points, respectively, and in control group were (9.23±0.57) points, (23.15±0.38) points, and (2.84±0.27) points, respectively. The compared results of VAS scores before and after analgesia between two groups showed that there was an interaction between the treatment measures and the time factor (Ftreatment×time=32.187, P<0.001). The results of further analysis by fixing the time factor showed that there was no significant difference in the VAS score between the two groups 5 min before analgesia (P>0.05), while 15 and 30 min after analgesia, the VAS scores in the observation group both were significantly lower than those in the control group, and the differences were statistically significant (t=20.415, 40.281; P<0.001). And the results of further analysis by fixing the treatment measures factor showed that there were significant differences in VAS scores before and after analgesia both in the observation group and the control group (F=16.324, 12.338; P<0.001). ④ The compared results of body temperatures before and after analgesia showed that there was no interaction between the treatment measures and the time factor (Ftreatment×time=0.699, P=0.307). There was no significant difference in body temperature at the time of 5 min before analgesia, 1 h and 2 h after analgesia (F time=0.287, P=0.715). There was no significant difference in the body temperature between the two groups (Ftreatment=0.365, P=0.644). ⑤The incidences of chill, hypotension and total adverse reactions in observation group were 1.9% (1/52), 3.8% (2/52), 15.4% (8/52) respectively, which were significantly lower than those in control group 16.0% (8/50), 18.0% (9/50), 50.0% (25/50), and all the differences were statistically significant (χ2=4.651, P=0.031; χ2=5.307, P=0.021; χ2=13.956, P<0.001).
Conclusions Preheating local anesthetics to human body temperature during labor can shorten the onset time of analgesia, improve the analgesic effect, and reduce the risk of adverse reactions.