title: Chronological Changes in Ropivacaine Concentration and Analgesic Effects Between Transversus Abdominis Plane Block and Rectus Sheath Block.
abstract: OBJECTIVE
  Transversus abdominis plane block (TAPB) and rectus sheath block (RSB) are popular methods of controlling postoperative pain. Chronological changes in blood concentrations of local anesthetics have not been described, although a large amount of local anesthetic is required to block these compartments. We postulated that blood concentrations of anesthetics would peak earlier during TAPB than RSB (primary end point). Secondary end points were elapsed time from block until first postoperative rescue analgesia and affected dermatomes.
  
  
  METHODS
  This prospective, randomized study included 22 patients scheduled for laparoscopic ovarian surgery under general anesthesia. The patients were randomized to receive either a bilateral single-shot TAPB or a bilateral RSB (15 mL of 0.5% ropivacaine per side). Arterial blood was sampled 10, 20, 30, 45, 60, 90, and 120 minutes after ropivacaine administration. This trial was registered at the UMIN-Clinical Trials Registry (UMIN000012133) before patient recruitment.
  
  
  RESULTS
  Arterial ropivacaine levels after block peaked earlier in the TAPB than in RSB [Tmax: 35 (12) vs 53 (16) minutes; P = 0.02], whereas peak ropivacaine concentrations did not significantly differ between the groups [Cmax: 1.83 (0.41) vs 1.79 (0.33) μg/mL; P = 0.54]. Peak ropivacaine concentrations exceeded 2.2 μg/mL in 1 and 2 patients in the RSB and TAPB groups, respectively, although symptoms of local anesthetic systemic toxicity were not evident in any of them. The median [interquartile range] duration of analgesia was significantly longer for TAPB than RSB (421 [335-536] vs 196 [168-277] minutes; P = 0.01).
  
  
  CONCLUSIONS
  Peak ropivacaine concentrations were comparable during TAPB and RSB, but peaked earlier during TAPB. Although 150 mg of ropivacaine remained effective significantly longer during TAPB than RSB during laparoscopic surgery, this dose could cause local anesthetic systemic toxicity. The analgesic effects of blocks with less ropivacaine should be assessed.
authors.affiliation: From the Department of Anesthesiology, Sapporo Medical University School of Medicine, Sapporo, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Murouchi
authors.forename: Soshi
authors.initials: S
authors.lastname: Iwasaki
authors.forename: Michiaki
authors.initials: M
authors.lastname: Yamakage
mesh_terms: D000009:Abdominal Muscles / Q000098:blood supply / Q000187:drug effects; D000328:Adult; D000577:Amides / Q000008:administration & dosage*; D000779:Anesthetics, Local / Q000008:administration & dosage*; D001340:Autonomic Nerve Block / Q000379:methods*; D005260:Female; D006801:Humans; D010535:Laparoscopy / Q000009:adverse effects*; D010051:Ovarian Neoplasms / Q000175:diagnosis / Q000601:surgery; D010149:Postoperative Pain / Q000175:diagnosis / Q000209:etiology / Q000517:prevention & control*; D011446:Prospective Studies; D017568:Rectus Abdominis / Q000098:blood supply / Q000187:drug effects; D000077212:Ropivacaine; D016896:Treatment Outcome; D055815:Young Adult
chemical_list: D000577:Amides; D000779:Anesthetics, Local; D000077212:Ropivacaine