Intrathecal Hydromorphone for Labor Analgesia

This study will investigate the dose of hydromorphone which will relieve the pain of women in
labor when delivered directly in the area around the spinal cord (i.e., intrathecal
injection). The primary objective is to determine the dose of intrathecal hydromorphone that
results in a pain score of less than 4 out of 10 thirty minutes after intrathecal injection
in 50% of women. Secondary objectives include determining this dose at five and ten minutes
after injection. Thirty women admitted to labor and delivery for planned vaginal delivery
desiring epidural placement will be consented for the study. The starting dose of intrathecal
hydromorphone will be 6 mcg. The up-and-down sequential allocation method of statistical
analysis will be used, meaning that each subsequent dose will be dependent upon the result
obtained from the prior dose - ergo, if the initial subject has pain relief, the second
subject will receive 4 mcg (2 mcg less), but if the initial subject does not have pain
relief, the second subject will receive 8 mcg (2 mcg more) of hydromorphone.

After the intrathecal injection is given and the epidural is placed, visual analogue pain
scores will be assessed 60 minutes following injection. A pain score of less than three will
be a positive result. A pain score of three or greater will be a negative result. Blood
pressure, heart rate, arterial oxygen saturation, fetal heart rate, and any side effects will
also be assessed.