Comparison of blood pressure measurements on the upper and lower extremities during spinal anesthesia

Introduction: During spinal anesthesia, measurement of blood pressure is often obtained
by an indirect method using an inflatable cuff on the upper arm. The relationship between
the blood pressure measurements at the two sites in patients undergoing spinal anesthesia is
unclear. This study was designed to evaluate the difference observed in systolic blood
pressure (SBP) taken from the upper limb (UL) and the lower limb (LL) in patients under
spinal anesthesia in lower abdomen surgery.
Methods: In this descriptive-analytic study, 62 males undergoing lower abdomen surgery
were selected. The blood pressure cuff was placed on the right arm, the right leg, the left
arm and the left leg, respectively. Before and then 10 and 25 minutes after spinal
anesthesia, the systolic blood pressure (SBP) readings was taken by finger palpation from
the 4 limbs using the manual mercury sphygmomanometer. The data were analyzed using
paired t-test and ANOVA.
Results: We found that SBP reading taken from the legs before and 10 minutes after
spinal anesthesia were significantly higher than arms pressures (P<0.001). The SBP in
the legs in 25 minutes after spinal anesthesia showed more decline compared with the
arms. There was no significant difference in SBP between upper and lower limbs in all the
times.
Conclusion: The blood pressure of the lower limb was higher than the upper limb. In cases
that could not be detect the blood pressure from upper limb, we can measure it from lower
limb. It is recommended to take a single blood pressure reading of arm before anesthesia
and then use the lower limb for evaluating the difference between the two sites.