Femoral artery cannulation for monitoring in critically ill children: prospective study. Seventy-seven attempted percutaneous femoral artery cannulations were prospectively evaluated in 74 children. Artery cannulation was successfully accomplished in 73 (95%) cases and lasted for a mean of 6 days. Sixty percent of the catheters were inserted on the first attempt. Fifty-two (71%) patients weighed less than 10 kg and 55 (75%) patients were less than 12 months old. Fifty-one (70%) patients received inotropic support at the time of cannulation, and 27 (37%) eventually died from causes unrelated to catheter insertion. There was one episode each of line-associated infection and transient distal ischemia not resulting in tissue loss, and two episodes of catheter malfunction. In eight (11%) patients, signs of distal vascular insufficiency developed shortly catheter placement and resolved after catheter removal. The development of this complication correlated significantly (p less than .05) with younger age (5.5 vs. 22.3 months). We conclude that femoral artery cannulation has a high degree of success in very small, critically ill children. It should be considered an acceptable alternative to small-vessel cannulation when the latter is not technically achievable, or in the unstable patient where rapid establishment of reliable arterial access is necessary. 