Ventilatory and blood gas changes during laparoscopy with local anesthesia DAVID R. BROWN, M.D., F.A.C.A. JOHN I. FISHBURNE, M.D., F.A.C.A., F.A.C.O.G. V. 0. ROBERSON, M.D. JARASLAV F. HULKA, M.D., F.A.C.O.G. Chapel Hill, North Carolina A study was performed on a series of healthy patients undergoing laparoscopy for tubal ligation with local anesthesia in a non-operating room setting. Ventilatory parameters, blood gas, pH, blood pressure, and pulse were monitored. The results revealed that no adverse effect on hemoglobin saturation or carbon dioxide exchange were found when fentanyl alone was used as a supplementary analgesic. An occasional vagal reflex was observed, and it is recommended that an intravenous line be established in the event that pharmacologic intervention should become necessary. Nitrous oxide produced less discomfort than carbon dioxide as the inflation gas with this minimal analgesia. IN RECENT YEARS, laparoscopy for diagnostic proce- dures and tubal ligation has become a clinically useful procedure. Because of the shortage of hospital beds and ancillary personnel required for in-hospital care and general anesthesia, a study was undertaken to determine the safety of outpatient laparoscopy with local anesthesia in a non-operating room setting. The study, which was performed in the clinical research unit of the North Carolina Memorial Hospital, was designed to simulate the outpatient clinic environment and was carried out on healthy patients with local anesthesia supplemented by a short-acting narcotic analgesic. Ventilation, carbon dioxide exchange, blood gases, and pH were studied with reference to the safety of the procedure. Methods The subjects were 15 women, Class I (ASA), between 21 and 42 years of age who were chosen at random. All were advised of the study, and informed consent was From the Departments of Anesthesiology and Obstetrics-Gynecology, School of Medicine, University of North Carolina. · Received for publication December 18, 1974. Revised May 12, 1975. Accepted May 22, 1975. Reprint requests: Dr. David R. Brown, Department of Anesthesiology, University of North Carolina, School of Medicine, Chapel Hill, North Carolina 27514. 741 obtained. Prior to the procedure, each patient had a medical examination, complete blood count, urinalysis, and Papanicolaou smear which were within normal limits. The outpatients presented to the Clinical Research Unit after fasting and without premedication. An in- travenous line was established. After Allen's 1 test to evaluate patency of the collateral circulation to the hand, a percutaneous arterial catheter (20 gauge) was inserted into a radial artery with local anesthesia. This was connected to a pressure transducer and used for blood pressure and pulse recording as well as arterial blood gas and pH sampling (Fig. 1). Minute ventilation CVE), tidal volume (VT), respira- tory rate (f), and vital capacity (VC) were determined by electronic integration of air flow, measured with a pneumotachograph* and a differential pressure trans- ducer.t The pneumotachograph was calibrated over a wide range with known volumes of room air. The per cent of expired carbon dioxide was continuously sampled at the patient's mouthpiece and measured with an infra-red carbon dioxide analyzer.; End tidal Po 2 (PETo 2 ) was measured in samples of gas taken from the mouthpiece with the use of the synchronous pulse generator method described by Roberson and associates. 2 The patients breathed *Fleish No. 3, Instrumentation Associates, Inc., 17 W. 60th St., New York, New York 10023. tSanborn 270. tGodart capnograph, Instrumentation Associates, Inc.