TAP Catheters Versus Intrathecal Morphine for Cesarean Section

Overview

Morphine, when given as part of spinal anesthesia, is associated high incidence of nausea and pruritus, which may affect quality of recovery. The investigators hypothesize that long-acting local anesthetic infusions via TAP catheter can provide better quality of recovery after cesarean section than spinal morphine.

This study is a prospective, open, randomized study. Subjects will be randomized using a computer-generated table of random numbers into 2 groups. The first group will receive intrathecal morphine as part of a spinal anesthetic. The second group will receive an ultrasound-guided bilateral TAP catheter at the end of the procedure, while the subject is still under the effect of spinal anesthetic. Group assignments will be sealed in sequentially numbered, opaque envelopes that would be opened by an anesthesiologist performing the cesarean section. The research nurse or one of the investigators, not involved with patient care after the subject signed written informed consent, will provide postoperative data collection. All patients will be pre-hydrated with 1000ml of Lactated Ringer's solution. They will then be brought to the OR and without premedication receive a spinal anesthetic in a sitting position. The spinal anesthetic will be administered at either L3-4 or L4-5 level with 24G Sprotte needle and contain 1.4ml of 0.75% hyperbaric bupivacaine. As per protocol, the first group would receive 0.3mg of preservative-free morphine, mixed in the same syringe. All the subjects then will be immediately placed in supine position with left uterine displacement, and supplemental oxygen 4L/min will be administered via nasal cannula for the duration of procedure. After a successful spinal anesthetic is confirmed by loss of sensation to pinprick, cesarean section will be performed. Intraoperative hypotension will be treated with IV fluids, as well as intermittent boluses of IV ephedrine or IV neosynephrine as needed to keep SBP\>100mm Hg. Intraoperative nausea will be treated with IV ondansetron as needed. At the end of the procedure, the second group will receive ultrasound guided TAP catheter using a linear 6-15MHz ultrasound probe on a portable ultrasound machine (SonoSite, Bothell, WA) as previously described (Hebbard P, 2007). Each catheter will be dosed with 20ml of Ropivacaine 0.5% at that time. Double lumen OnQ C-block pump (I-Flow, LLC, Lake Forest, CA) containing 700 ml of the Ropivacaine 0.2% will be attached to the TAP catheters in the recovery room. The time that this occurs will be recorded in the eMAR. The catheters will run at 7cc/hr/side for 50 hrs. In the recovery area, the patient will be asked to rate their pain at rest, nausea, and pruritus upon arrival and at regular intervals as per routine care. The pain will be rated on a 0 to 10 numeric rating scale (NRS), where 0 means no pain and 10 is the worst pain imaginable. Fentanyl 50 mg IV will be administered every 5 minutes to maintain an NRS pain score \<4 of 10. Nausea will be rated on a 0 to 2 scale (0 = no nausea and vomiting, 1 = mild to moderate nausea or vomiting not needing treatment, and 2 = severe nausea or vomiting needing treatment). It will be treated with 4mg IV ondansetron, if necessary. The presence of pruritus and whether the treatment is desired will be assessed on a 0 to 2 scale (0= no pruritus, 1= mild pruritus not requiring treatment, 2= moderate pruritus requiring treatment or severe pruritus). Pruritus will be treated with IV diphenhydramine 25 mg if the subject weighs less than 150lbs and 50mg if the subjects weighs more than 150lbs. Upon transfer to the maternity floor, the nurses will ask the subjects to rate their pain at rest, nausea, and pruritus as part of usual care, upon arrival and every 4 hours for 48 hours as described above. The answers will be recorded on a data collection too. For the following 48 hours, the patient will be treated as follows: nausea will be treated with 25 mg IV promethazine followed by 4mg IV ondansetron if necessary every 6 hours. Pruritus will be treated with IV/PO diphenhydramine 25 mg if the subject weighs less than 150lbs and 50mg if the subject weighs more than 150lbs every 6 hours if necessary. Pain will be treated with SQ morphine (4mg for NRS pain 3-4, 6 mg for NRS pain 4-7, 8mg for NRS pain \>7) every 4 hours as requested and 30mg IV ketorolac every 6 hours until subjects start eating. Once the subject tolerate diet, their pain will be treated with 800 mg PO ibuprofen every 6 hours and a combination of oxycodone 5mg and acetaminophen 325mg PO every 4 hours as requested (1 tab for NRS pain 4-7, 2 tabs for NRS pain \>7).