The Effects of Height and Weight Adjusted Dose of Local Anesthetic.
Condition: Complications; Cesarean Section; Hypotension
MeSH terms: Hypotension
Study type: Interventional

Summary: 
      At our centre a conventional dose of 12 mg of hyperbaric bupivacaine in combination with a
      short acting opioid fentanyl (to increase block density) and a long acting opioid morphine
      (to provide post-operative pain relief ) is used for spinal anesthesia for cesarean
      section.However, larger doses of local anesthetic drug when used in caesarean section
      commonly cause low blood pressure and requires drugs (vasopressors) to treat it. In our study
      the investigators will standardize the doses of both opioids (fentanyl/morphine) and adjust
      the dose of local anesthetic (bupivacaine) based on the patients height and weight .One of
      the obvious challenges anesthesiologists face is providing adequate anesthesia to the patient
      whilst minimizing harmful side effects. Our primary concern is the low blood pressure as an
      effect of the spinal anesthetic as it is harmful to both mother and the baby. The
      investigators propose that the extent of surgical anesthetic block, which is dependent on
      height and weight in our adjusted dose group, will provide adequate anesthesia for surgery
      and minimise maternal low blood pressure.
    

Detailed description: 
      Study design is prospective, randomized, double blind, placebo controlled.

      Patients presenting for elective cesarean section under neuraxial block and meeting inclusion
      criteria will be randomized to two groups:

      Group 1: Fixed dose group: Bupivacaine 12 mg, Fentanyl 15 mcg, Morphine 100 mcg Group 2:
      Height and weight adjusted bupivacaine dose, fentanyl 15 mcg, morphine 100 mcg Patients are
      fasted as per Canadian guidelines prior to the procedure. All patients have an IV cannula
      inserted,baseline vitals recorded and routine blood work checked prior to blockade. Routine
      monitoring (as per Canadian Anesthesia Society (CAS) guidelines) occur during and after the
      procedure. This includes pulse oximetry (SpO2), ECG and non-invasive blood pressure (NIBP).
      NIBP monitoring occurs every two minutes for the first 20 minutes post spinal and every 5
      minutes thereafter. Oxygen via Hudson mask or nasal prongs is available if required.

      Spinal anesthetic is performed with standard doses of drugs and the level of sensory block is
      tested with ice. Motor block is tested with Bromage scale just before prepping and draping.
      Once deemed adequate, surgery begins. During surgery, phenylephrine/ephedrine is given to
      maintain blood pressure as necessary. After surgery, patients are monitored in a recovery
      area until fit to be transferred to their rooms. If patient reports extreme discomfort or
      sharp pain during the surgery,conversion to general anesthetic is as per the discretion of
      the attending anesthesiologist.
    

Intervention name(s): Phenylephrine
Intervention type(s): Drug
Intervention description(s): 100 mcg of phenylephrine or 5 mg ephedrine given as deemed necessary for treating episodes of hypotension.
Other intervention name(s): Ephedrine
Intervention MeSH terms: Phenylephrine; Oxymetazoline; Ephedrine
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Double (Participant, Investigator)
Primary purpose: Prevention