ATLS guidelines overestimate systolic blood pressure

The advanced trauma life support (ATLS) course teaches that systolic blood pressure can be estimated from whether radial (>80 mm Hg), femoral (70-80), or carotid (60-70) pulses are palpable. To assess whether this teaching is accurate Deakin and Low (p 673) measured blood pressure through invasive arterial monitoring in 20 patients with hypovolaemic shock while a blinded observer palpated the radial, femoral, and carotid pulses. The radial pulse always disappeared before the femoral pulse, which always disappeared before the carotid pulse, but most patients in each of these groups had an actual blood pressure lower than that predicted by the course guidelines. The guidelines therefore underestimate the degree of hypovolaemia.