Wesstrom 1979.

Methods	Random assignment to one of 4 groups initially, high end hole, high side hole, low end hole or low side hole catheter. After the first 15 months the side hole groups were dropped and the final 4 months randomization was to high or low placement of end hole catheters only.
Participants	62 term and preterm infants, requiring umbilical arterial catheterisation for medical care.
Interventions	39 infants had end hole catheters, 23 had side hole catheters.
Outcomes	Thrombosis on angiography performed at removal was the primary outcome variable. Necrotising enterocolitis not determined; clinical vascular compromise not stated.
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Adequate sequence generation?	Unclear risk	Insufficient information presented to ascertain allocation masking.
Allocation concealment?	High risk	Masking does not appear to have been attempted. Random assignment to one of 4 groups initially, high end hole, high side hole, low end hole or low side hole catheter. After the first 15 months the side hole groups were dropped and the final 4 months randomization was to high or low placement of end hole catheters only.
Blinding? All outcomes	High risk	Masking of outcome assessment was not attempted.
Incomplete outcome data addressed? All outcomes	Unclear risk	All infants appear to have been accounted for; there were nine infants among the 71 subjects for whom autopsy or angiography were not available.
Free of selective reporting?	Low risk
Free of other bias?	Unclear risk	Random assignment to one of 4 groups initially, high end hole, high side hole, low end hole or low side hole catheter. After the first 15 months the side hole groups were dropped and the final 4 months randomization was to high or low placement of end hole catheters only