Observational study comparing non-invasive blood pressure measurement at the arm and ankle during caesarean section

Upper-arm non-invasive blood pressure measurement during caesarean section can be uncomfortable and unreliable because of movement artefact in the conscious parturient. We aimed to determine whether ankle blood pressure measurement could be used instead in this patient group by comparing concurrent arm and ankle blood pressure measured throughout elective caesarean section under regional anaesthesia in 64 term parturients. Bland-Altman analysis of mean difference (95% limits of agreement [range]) between the ankle and arm was 11.2 (-20.3 to +42.7 [-67 to +102]) mmHg for systolic arterial pressure, -0.5 (-21.0 to +19.9 [-44 to +91]) mmHg for mean arterial pressure and -3.8 (-25.3 to +17.8 [-41 to +94]) mmHg for diastolic arterial pressure. Although ankle blood pressure measurement is well tolerated and allows greater mobility of the arms than measurement from the arm, the degree of discrepancy between the two sites is unacceptable to allow routine use of ankle blood pressure measurement, especially for systolic arterial pressure. However, ankle blood pressure measurement may be a useful alternative in situations where arm blood pressure measurement is difficult or impossible.