Table 3.

Subgroup analyses: the effect of surgery type and different dose levels of adjuvant intrathecal meperidine. ^aIncludes transurethral resection of the prostate and suprapubic prostatectomy; ^bIncludes surgery of lower limbs or abdomen and herniorrhaphy; Group I, adjuvant intrathecal meperidine ≦ 0.2 mg kg⁻¹ or ≦ 12.5 mg; Group II, adjuvant intrathecal meperdine >0.2 mg kg⁻¹ or >12.5 mg; NA, not applicable; RR, relative risk.

Subgroup	No of studies	Overall incidence of shivering				Incidence of need for rescue analgesics				Incidence of nausea				Incidence of vomiting
		RR	95% CI	I 2	P	RR	95% CI	I 2	P	RR	95% CI	I 2	P	RR	95% CI	I 2	P
Overall	28	0.31	0.24–0.40	42%	<0.00001	0.27	0.12–0.64	0%	0.003	1.84	1.29–2.64	23%	0.0009	2.23	1.23–4.02	19%	0.008
Surgery type
Caesarean section25,27–29,31,32,42,43,48,52,53,56–59	15	0.3	0.21–0.43	49%	<0.00001	0.26	0.10–0.66	0%	0.005	1.93	1.17–3.16	46%	0.009	2.6	1.16–5.85	44%	0.02
Orthopedic surgery26,30,45,46,50	5	0.3	0.14–0.63	43%	0.002	0.33	0.04–2.94	NA	0.32	3.65	0.58–23.05	34%	0.17	NA	NA	NA	NA
aUrology surgery16,44,47,55	4	0.11	0.03–0.38	0%	0.0006	0.41	0.17–0.98	NA	0.05	3.5	0.19–63.16	NA	0.4	2	0.19–21.18	NA	0.56
bOther surgery33,49,51,54	4	0.42	0.25–0.70	9%	0.0008	NA	NA	NA	NA	1.82	0.83–4.00	0%	0.14	1.96	0.36–10.71	0%	0.44
Meperidine dose
Group I16,25–32,42–46,48,49,51,52,54,56,57,59	22	0.34	0.25–0.46	47%	<0.00001	0.28	0.09–0.86	0%	0.03	1.73	1.26–2.38	0%	0.0008	2.58	1.34–4.98	0%	0.005
Group II16,25–27,33,42,47,50,53,55,58	11	0.17	0.08–0.38	0%	<0.0001	0.26	0.07–0.94	NA	0.04	1.95	1.07–3.56	40%	0.03	1.98	0.72–5.44	42%	0.19