Invasive arterial blood pressure monitoring in an out-of-hospital setting: an observational study.

ABSTRACT

BACKGROUND: Non-invasive arterial blood pressure measurement is often inaccurate in emergency unstable patients. A study was undertaken to assess the feasibility of out-of-hospital intra-arterial catheterisation in haemodynamically unstable patients and to evaluate the correlation between invasive and non-invasive arterial pressure values. METHODS: In this prospective 2-year observational study conducted by mobile emergency medical units, the success rate of arterial catheterisation was calculated and blood pressure values measured invasively and non-invasively after successful catheterisation were compared. RESULTS: 94 patients were included. The success rate for catheterisation (44 radial access, 50 femoral access) was 86% (95% CI 79% to 93%). Bias and precision in invasive versus non-invasive comparisons were -0.1, 38 mm Hg for systolic pressure and 4.2, 27 mm Hg for diastolic pressure. Values differed by more than 20 mm Hg in over 40% of patients. Invasive measurement led to 79 changes in vasoactive treatment in 51 patients. CONCLUSION: Emergency out-of-hospital invasive arterial blood pressure monitoring in haemodynamically unstable patients is highly feasible. Discrepancies between invasive and non-invasive measurements are common and highlight the value of early out-of-hospital monitoring.