Arterial catheter placement more difficult in women

Critically ill patients often require frequent monitoring of blood gases and the arterial blood required for these analyses is most conveniently sampled via an indwelling arterial catheter; arterial catheterization also provides the means for continuous monitoring of blood pressure. 

Of all the invasive procedures that critically ill patients are likely to require, placement of an arterial catheter is one of the most common, and one that can be challenging and not always successful. The reasons for failure to place an arterial catheter were the object of a recently published clinical study conducted at a New York teaching hospital. 

During a 4-month study period, 92 attempts at placing an arterial line, to either the femoral or radial artery of 72 ICU patients requiring catheterization, were studied in detail. First-time failure occurred in 26 of 92 (28.3 %) attempts. In 19 of these 26 failures, a second or third attempt resulted in successful placement of a further eight arterial lines, but the procedure had to be abandoned in a total of 18 of the 92 attempts. 

Of many possible patient and operator factors that might be associated with failure examined, just two proved significant. They were patient gender and blood pressure. Of all 56 attempts in female patients, 24 (42.9 %) failed. Only two of 36 (5.6 %) attempts in male patients failed. 

Blood pressure was significantly lower among patients whose catheterization failed compared with blood pressure of those who were successfully catheterized. The failure rate was higher for attempts on the femoral artery than for attempts on the radial artery, but this difference did not reach statistical significance. Patient factors such as age, BMI, level of consciousness, etc. 

were not found to be predictive of failure. Similarly, operator seniority and degree of emergency for procedure were not, as might be expected, predictive of failure. The authors speculate that the reason for the strikingly high failure rate among women may be due to the relative small size of female arteries. 

Reduced ability to detect a pulse in those with hypotension is thought to be a possible explanation for the increased failure rate among patients with reduced blood pressure.