Comparison 1. Vapocoolant vs placebo/no treatment.

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 Pain during cannulation	8	848	Mean Difference (IV, Random, 95% CI)	‐12.51 [‐18.67, ‐6.35]
2 Pain during cannulation by participant age	8	848	Mean Difference (IV, Random, 95% CI)	‐12.51 [‐18.67, ‐6.35]
2.1 Children	2	165	Mean Difference (IV, Random, 95% CI)	‐8.78 [‐28.56, 11.01]
2.2 Adults	6	683	Mean Difference (IV, Random, 95% CI)	‐13.64 [‐20.17, ‐7.10]
3 Pain during cannulation by vapocoolant type	8	848	Mean Difference (IV, Random, 95% CI)	‐12.51 [‐18.67, ‐6.35]
3.1 Non‐ethyl chloride	3	373	Mean Difference (IV, Random, 95% CI)	‐12.42 [‐24.58, ‐0.26]
3.2 Ethyl chloride	5	475	Mean Difference (IV, Random, 95% CI)	‐12.49 [‐20.62, ‐4.36]
4 Pain during cannulation by application time	8	848	Mean Difference (IV, Random, 95% CI)	‐12.51 [‐18.67, ‐6.35]
4.1 < 5 seconds	3	378	Mean Difference (IV, Random, 95% CI)	‐6.17 [‐19.97, 7.63]
4.2 5 to 10 seconds	5	470	Mean Difference (IV, Random, 95% CI)	‐15.89 [‐22.37, ‐9.41]
5 Pain during cannulation by clinical situation of use	8	848	Mean Difference (IV, Random, 95% CI)	‐12.51 [‐18.67, ‐6.35]
5.1 Elective	3	248	Mean Difference (IV, Random, 95% CI)	‐13.13 [‐21.72, ‐4.53]
5.2 Emergency	5	600	Mean Difference (IV, Random, 95% CI)	‐11.92 [‐21.36, ‐2.47]
6 Good pain relief during cannulation	2	281	Risk Ratio (M‐H, Fixed, 95% CI)	1.67 [1.30, 2.13]
7 Pain immediately after cannulation	1	80	Mean Difference (IV, Random, 95% CI)	‐8.0 [‐17.88, 1.88]
8 Pain at application	4	461	Mean Difference (IV, Random, 95% CI)	6.26 [2.23, 10.30]
9 No/Little pain at application	1		Risk Ratio (M‐H, Random, 95% CI)	Totals not selected
10 First attempt success	6	812	Risk Ratio (M‐H, Fixed, 95% CI)	1.00 [0.94, 1.06]
11 Adverse events	5	551	Risk Difference (M‐H, Fixed, 95% CI)	0.03 [0.00, 0.05]
12 Participant/Caregiver satisfaction (satisfied with treatment)	2	268	Risk Ratio (M‐H, Random, 95% CI)	1.31 [0.82, 2.09]