Acta anaesthesiologica Sinica最新文献

Background: The aim of this study was to investigate the anesthetic and analgesic effects of subanesthetic concentration of nitrous oxide and to compare these effects with halothane and fentanyl.

Methods: The antinociceptive effects were assessed in male Sprague-Dawley rats by behavioral responses to phasic and tonic nociceptive stimulations and biochemical index of pain, formalin-induced Fos-like immunoreactivity (Fos-LI), in spinal cord dorsal horn. Neurological functions (proprioception, mental status and motor function) were monitored to determine whether or not behavioral responses were impaired by anesthetic action of the treatment. Four groups of rats treated with: (1) saline, (2) 75% nitrous oxide (0.5 MAC), (3) 0.5% halothane (0.5 MAC) and (4) fentanyl 100 micrograms/kg were subject either to graded intensity of CO2 laser stimulation (phasic pain) or s.c. injection of 50 microliters 2.5% formalin (tonic pain) in two separate studies. All rats in the tonic pain study were killed for immunohistochemistry at 60 min after formalin injection. Maximal counts of Fos-LI labelled neurons in rat spinal cord dorsal horn were compared according to the laminar distribution.

Results: We found that all rats exhibited normal righting reflexes regardless of whatever treatment. Nitrous oxide and halothane greatly impaired mental status and motor function, indicating that both agents could induce a modest degree of sedation and paresis at subanesthetic concentrations. Fentanyl increased the threshold level to noxious thermal stimulation, and reduced the formalin-induced licking/biting behaviors and the number of Fos-LI labelled neurons which are predominantly found in the neck of the dorsal horn. Nitrous oxide and halothane increased the thermal nociceptive threshold, suppressed licking/biting behavior in both early and late phases of the formalin test. Unlike fentanyl, nitrous oxide and halothane failed to suppress c-fos expression. The extent and pattern of nitrous oxide-induced antinociception was identical to halothane, which is known to have little or no analgesic effect. The lack of attenuated biochemical response to tonic pain stimulation may suggest that nitrous oxide fails to suppress spinal sensitization despite its potent inhibition on behavioral hyperalgesia.

Conclusions: These findings suggest that, at the spinal level, subanesthetic concentration of nitrous oxide greatly attenuates nociceptive behaviors mainly due to a non-selective suppression of behavioral responses that are commonly associated with inhalation anesthetic drugs.

Complications arising from hysteroscopy are relatively rare events. They occur more frequently with operative hysteroscopy than with diagnostic hysteroscopy. Hysteroscopic procedures, which are alternatives to hysterectomy for surgical treatment of menorrhagia and uterine fibroids, place women to run the risk of intravasation of uterine distention fluid. Excessive intravasation can entail fluid overload, pulmonary edema, congestive heart failure, and electrolyte imbalances. The prerequisite for treatment of hysteroscopic fluid overload is knowing the nature of the intravasation fluid and it should be promptly treated to prevent neurological sequelae. Almost all serious complications of operative hysteroscopy can be avoided if proper precautions are taken and close communication is maintained between the gynecologic surgeon, the anesthesiologist, and nursing staff. Here, we present two cases of fluid overload with acute pulmonary edema and electrolyte imbalance from hysteroscopy with different distention media.

Background: An analgesic with a long-lasting effect is particularly desirable to patients suffering from long-standing pain. The aim of this study was to evaluate the antinociceptive effect and duration of action of an oily dosage form of nalbuphine base and to see whether its effect could last longer compared with nalbuphine HCl.

Methods: Male New Zealand White rabbits (n = 6 in each group) were used. Two studies were carried out. In study 1, we evaluated the antinociceptive effect of intramuscular nalbuphine HCl (in saline) with dosages of 25, 50, and 100 mumol/kg. In study 2, we evaluated the antinociceptive effects of intramuscular nalbuphine base (in sesame oil) with dosages of 100, 200, and 400 mumol/kg. In these studies, the vehicles (saline or sesame oil) were used as controls. A paw pressure test was used to detect the antinociceptive effect of the testing drugs.

Results: We found that nalbuphine HCl 25, 50 and 100 mumol/kg produced a dose-related antinociceptive effect with durations of action of 1, 1, and 1.3 h, respectively. Nalbuphine base 100, 200 and 400 mumol/kg also produced a dose-related antinociceptive effect but with longer durations of action of 8, 24, and 48 h, respectively. On an equimolar basis (100 mumol/kg), nalbuphine base produced a 6-fold increase in the duration of action than did nalbuphine HCl.

Conclusions: We conclude that intramuscular nalbuphine base produced a relatively longer duration of action than did intramuscular nalbuphine HCl.

Background: Insufficient education and limited clinical practice on the part of physicians may contribute to the undertreatment of cancer pain in Taiwan. To address these concerns, a survey among physicians and fifth-year medical students relevant to cancer pain management (CPM) was carried out in a medical school and its principal teaching hospital.

Methods: A questionnaire on CPM was sent to 97 physicians and 78 fifth-year medical students (equivalent to the third-year medical students in the United States). The same questionnaire was delivered again to these 78 fifth-year medical students after they had completed a modified curriculum of anesthesiology with a 4-hour course on introduction to clinical pharmacology of CPM.

Results: The physicians knowledgeable on pain (physicians of anesthesiology, hematology-oncology, or radiation oncology), physicians unfamiliar with pain (outside of anesthesiology, hematology-oncology, or radiation oncology), and the 5th-yr medical students took similar negative attitudes (24-92%, 33-89%, and 23-94%) toward the optimal use of analgesics for CPM. As compared, the mean score on knowledge of prescribing opioids of pain-knowledgeable physicians was 3.60, the highest of all as against 2.61 of other physicians and 2.54 of 5th-yr medical students. On attitudes toward prescribing opioids, both pain-knowledgeable physicians and other physicians scored a higher means, respectively of 3.52 and 2.91 as opposed to 2.68 of 5th-yr medical students, the lowest of all. However, seniority or length of clinical practice did not improve knowledge or affect attitudes toward CPM. In addition, this 4-hour course did enable the 5th-yr medical students to take a more positive attitude toward and become more knowledgeable on CPM than pain-knowledgeable physicians, as a comparison was made.

Conclusions: The effect of accumulation of clinical experience and seniority of clinical practice on CPM was limited among general physicians, except for clinical specialty on anesthesiology, hematology-oncology, or radiation oncology. In Taiwan, the knowledge of and positive attitude toward CPM could only be conveyed to physicians through undergraduate, post graduate or on-job education.

Background: Although propofol has been widely used the uncertainties about its pharmacokinetics and pharmacodynamics are still in existence especially on acute infusion model. This study was designed to observe the changes of the arterial and superior vena cava blood concentrations of propofol during cardiopulmonary bypass and to see whichever site is more appropriate for pharmacodynamic studies of propofol.

Methods: Eight patients undergoing cardiopulmonary bypass were infused rapidly with propofol. Samples were collected concurrently from bypass arterial side (Ca) and superior vena cava (Cv) side at 0, 0.5, 1, 1.5, 2, 5, 10, 20, 30, and 40 minutes after infusion and analyzed with high pressure liquid chromatography (HPLC). Arterial blood pressure was also recorded at the same time.

Results: After administration, the concentration at Ca side was significantly higher than that at the corresponding Cv side from 0.5 to 5 min. The concentration at Ca side peaked at 0.5 min, then decreased rapidly and crossed the Cv curve at approximately 10 min. Thereafter Cv side concentration was slightly higher than that of Ca side. The mean arterial blood pressure decreased significantly from 1 to 20 min after injection. The change in Cv side was significantly consistent with the blood pressure change in the distribution phase (r = 0.78, r2 = 0.61 P < 0.001) (0 to 5 min).

Conclusions: There was a significant arteriovenous concentration difference of propofol after a rapid infusion in the cardiopulmonary bypass model. The hypotensive effect of propofol in the distribution phase can be predicted better on Cv side.

Malfunction of either inspiratory or expiratory check valve in a breathing circuit system may allow carbon dioxide (CO2) rebreathing and result in hypercapnia. The subsequent increase of PaCO2 may entail increased sympathetic activity which in turn causes serious problems such as tachyarrhythmia and myocardial ischemia, particularly in patients who have history of coronary artery disease (CAD). Here, we report an incident of rupture of the inspiratory valve in the breathing circuit which happened to a patient during induction of general anesthesia and eventuated in markedly heightened end-tidal CO2 (EtCO2) of the patient. The recognition, related complications and management of the inspiratory valve malfunction are discussed.

Although esophageal perforation after transesophageal echocardiographic (TEE) examination is rare yet the occurrence of this life-threatening complication is increasing. We report an unusual esophageal perforation occurring 4 days after coronary artery bypass graft surgery and Bentall's procedure. The perforation was due to inadvertent injury of the esophagus that was deformed and distorted by a large calcified lymph node in the mediastinum during intraoperative TEE instrumentation. We suggest that careful preoperative radiological examination of the mediastinum should be done to recognize the anatomical pathology in patient whose routine chest X-ray has disclosed a large calcified lymph node in the mediastinum, if he happens to undergo TEE, so as to avoid disastrous esophageal perforation.