Body habitus does not influence spread of sensory blockade after the intrathecal injection of a hypobaric solution in term parturients

Abstract

Purpose: To determine if the extent of sensory blockade after the intrathecal injection of hypobaric fentanyl (25 μg) and bupicavaine (2.5 mg) in the sitting position in term parturients is influenced by body habitus. Methods: A prospective observational study in 245 term parturients who received intrathecal fentanyl and bupivacaine plus an epidural test dose to initiate labour analgesia at an academic university hospital. The highest sensory blockade to ice and pinprick was determined at 15 and 30 min after the intrathecal injection. Correlations between sensory blockade and parturient height, weight and body mass index (BMI) were determined. Results: There was no association between highest sensory blockade and parturients' height. Increasing weight and BMI were associated with increased cephalad sensory blockade at 15 min, but not at 30 min. The estimated difference in sensory level between women at the extremes of BMI, based on our linear regression model, was less than one dermatome. Conclusion: Height did not influence the extent of sensory analgesia after initiation of intrathecal labour analgesia using a hypobaric solution injected with the parturient in the sitting position. Weight and BMI were associated with a non-clinically significant increase in the cephalic spread of analgesia, suggesting that dose adjustments based on body habitus in this population are not necessary.