title: Circadian effects on neural blockade of intrathecal hyperbaric bupivacaine.
abstract: BACKGROUND
  Circadian variations in the absorption, distribution, protein binding, elimination and metabolism of drugs account for many of the administration-time-dependent differences in their pharmacokinetics. The aim of this study is to determine whether the time of intrathecal injection influences spinal anesthesia.
  
  
  METHODS
  Ninety patients scheduled for orthopedic surgery were randomly assigned to three groups. Each group received spinal anesthesia with 0.5% bupivacaine 10 mg at different times; group AM (8 am to 12:00), group Noon (12:00 to 4:00 pm) and group PM (4:00 pm to 8:00 pm). Sensory and motor blockade were assessed by pinprick and a four-point modified Bromage scale. Time to first postoperative analgesic requirement and side effects such as hypotension, bradycardia, nausea, and shivering were recorded.
  
  
  RESULTS
  No significant differences were found among the three groups in peak sensory blockade, duration of motor block to Bromage 1 or side effects, but time to first postoperative analgesic requirement (P = 0.008), and recovery time of S1 sensation to pinprick were significantly prolonged in group Noon compared with the other groups (P = 0.03).
  
  
  CONCLUSIONS
  The tine of administration of spinal local anesthetics influences the duration of local anesthesia.
authors.affiliation: Department of Anesthesiology and Pain Medicine, Wonkwang University School of Medicine, Iksan, Korea.
authors.forename: Cheol
authors.initials: C
authors.lastname: Lee
authors.forename: Deok Hwa
authors.initials: DH
authors.lastname: Choi
authors.forename: Soo Uk
authors.initials: SU
authors.lastname: Chae