Summary of findings 3. Ultrasound guidance versus landmark method for peripheral venous cannulation in adults classed as easy.

Patient or population: adults undergoing peripheral venous cannulation classed as easya Settings: emergency department Intervention: USG Comparison: LM
Outcomes	Anticipated absolute effects* (95% CI)		Relative effect (95% CI)	No. of participants (studies)	Certainty of the evidence (GRADE)	Comments
	Risk with LM	Risk with USG
First‐pass success of cannulation Follow‐up: immediately after the procedure	966 per 1000	859 per 1000 (821 to 908)	RR 0.89 (0.85 to 0.94)	596 (1 RCT)	⊕⊕⊕⊕ High
Overall success of cannulation Follow‐up: immediately after the procedure	See comment	‐	‐	‐	‐	None of the studies included easy participants
Pain NRS: from 0 to 10, where 10 is maximum pain Follow‐up: immediately after the procedure	The mean pain score was 2.30	MD 0.60 higher (0.17 higher to 1.03 higher)		596 (1 RCT)	⊕⊕⊕⊝ Moderateb
Procedure time for first‐pass cannulation (seconds) Follow‐up: immediately after the procedure	The mean procedure time for first‐pass cannulation was 89.7 seconds	MD 94.8 seconds longer (81.2 longer to 108.5 longer)		596 (1 RCT)	⊕⊕⊕⊕ High
Number of cannulation attempts Follow‐up: immediately after the procedure	See comment	‐	‐	‐	‐	None of the studies included easy participants
Patient satisfaction NRS from 0 to 10 or 4‐step Likert scale The higher the score, the higher the level of satisfaction Follow‐up: immediately after the procedure	See comment	‐	‐	‐	‐	None of the studies included easy participants
Overall complications Follow‐up: immediately after the procedure	17 per 1000	43 per 1000 (15 to 118)	RR 2.48 (0.90 to 6.87)	596 (1 RCT)	⊕⊕⊕⊝ Moderatec
*The risk in the intervention group (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI). CI: confidence interval; LM: landmark; NRS: numeric rating scale; RCTs: randomised controlled trials; RR: risk ratio; USG: ultrasound guidance
GRADE Working Group grades of evidence High certainty: We are very confident that the true effect lies close to that of the estimate of the effect. Moderate certainty: We are moderately confident in the effect estimate: the true effect is likely to be close to the estimate of the effect, but there is a possibility that it is substantially different. Low certainty: Our confidence in the effect estimate is limited: the true effect may be substantially different from the estimate of the effect. Very low certainty: We have very little confidence in the effect estimate: the true effect is likely to be substantially different from the estimate of effect.

^aParticipants were classified according to the original studies' definitions.
^bWe downgraded by one level to moderate certainty due to risk of bias concerns (lack of blinding of the outcome assessors).
^cWe downgraded by one level to moderate certainty due to imprecision.