Forum. A comparison between the midline and paramedian approaches to the extradural space

A prospective, randomised study was devised to compare the midline and paramedian approaches to the extradural space in women during labour. The two approaches were equally successful with respect to catheter insertion and analgesia and had a similar incidence of complications, although the paramedian approach caused patients more discomfort. Since only 2 ml of 1% lignocaine with adrenaline were infiltrated prior to insertion of the Tuohy needle, a greater volume of the local anaesthetic may reduce the discomfort of using the paramedian approach.     

Halothane Dissolved in Fat as an Intravenous Anaesthetic to Rats

The anaesthetic properties of a halothane-in-fat solution given either as a single i.v. dose or as a continuous i.v. infusion were investigated in rats. 0.3 ml of a 5% solution of halothane in a fat emulsion was injected i.v. into 15 awake rats. At the end of the 30 s injection, all rats had collapsed from the upright position and showed no response to a firmly applied tail clamp. Breathing usually became shallow and irregular just after injection. Two rats died. In the surviving rats, movement in response to clamping of the tail reappeared after some 30 s (range 15–90 s). The rats regained the upright position after about 100 s, and appeared fully awake about 3 min (range 2–5 min) after injection. Surviving rats behaved normally after the experiment, and gained in weight. They were killed 1–29 days later. The lungs, kidneys, heart, brain and liver had a normal macroscopic and microscopic appearance. In a second set of experiments (n = 9), a 10% solution of halothane was continuously infused i.v. (3.75 (μ min^-1). The anaesthetic depth, as well as the mean arterial pressure, heart rate, respiratory rate and arterial Pco2 and Po2 were similar to values observed during inhalation of halothane in air at an inspired concentration of 1.1%. By doubling the infusion rate, MAP was reduced by 23%. It was easy to adjust anaesthetic depth by changing the infusion rate and recovery was fast.     

东莨菪碱麻醉作用与脑内单胺介质

脑室注射东莨菪碱的麻醉作用,使脑内5-羟色胺(5-HT)及5-羟吲哚乙酸(5-HIAA)显著增多。L-色氨酸负荷(400mg/kg.ip)能延长小鼠麻醉时间(P<0.01);而对氯苯丙氨酸耗竭大鼠脑内5-HT及5-HIAA后,未能消除麻醉作用。东莨菪碱还提高了大鼠中脑多巴胺含量,而去甲肾上腺含量未见明显改变。脑内5-HT系统的增强可以协同东莨菪碱的麻醉作用,但5-HT系统功能的完整性并不是这种麻醉作用的必要条件。并提示脑内M胆碱受体可能促进色胺能神经元的传递功能。     

A comparison of nalbuphine with fentanyl for postoperative pain relief following termination of pregnancy under day care anaesthesia

A double-blind investigation was undertaken to compare the efficacy of nalbuphine and fentanyl in the prevention of pain after day case termination of pregnancy. Forty patients were allocated randomly to receive nalbuphine 0.25 mg/kg or fentanyl 1.5 micrograms/kg immediately before induction of anaesthesia. The patients completed scores for pain and nausea, and performed a reaction time test to assess recovery. An observer assessed patient appearance at 1, 2 and 4 hours postoperatively. Patients who received nalbuphine had significantly lower pain scores at 1 hour (p less than 0.01) and 2 hours (p less than 0.05) and required significantly (p less than 0.05) less postoperative analgesia. No significant differences were found between the groups for incidence of nausea or for observer assessment of appearance. There was some evidence of psychomotor impairment at 2 hours in the nalbuphine group. Freedom from Controlled Drug Act regulations and improved analgesia with nalbuphine, render it more satisfactory for day case surgery than the more commonly used fentanyl.     

Nitrogen Diffusion into Closed Anesthesia Systems

Objective. In order to reduce losses of gases through plastic components and to reduce nitrogen accummulation during closed system anaesthesia we investigated either 10 sets of anaesthetic tubing made of silicon as used in standard clinical practice and 10 sets made of latex, which are not used anymore due to concerns about latex allergies. The results were compared to each one set made of conventional industrial rubber. Methods. Anaesthetic tubings were connected to ventilators with low fresh gas losses, suitable for closed system anaesthesia. For nitrogen measurements, a mass spectrometer was used.The fresh gas flow was set to exceed losses by leakages and the amount of gases, extracted from the system by the mass spectrometer. Results. Highest accumulation of nitrogen was found using tubings made of silicone. Conclusion. If closed anaesthetic systems in the future will be used in intensive care therapy or in case of long lasting procedures in which closed system anaesthesia is proceeded, materials other than silicone should be investigated to avoid regular purging of system and consecutive losses of gas mixtures.     

Sacrococcygeal local anaesthesia versus general anaesthesia for pilonidal sinus surgery: a prospective randomised trial

Sixty patients scheduled for pilonidal sinus surgery were prospectively randomly assigned to receive general anaesthesia or sacrococcygeal local anaesthesia with a newly-described technique. Patients in the general anaesthesia group spent more time in the operating theatre and recovery room than did those in the local anaesthesia group (p < 0.05). Two thirds (67%) of the patients in the local anaesthesia group left hospital on the day of surgery compared to only 17% of patients in the general anaesthesia group (p < 0.05). Visual analogue scale pain scores performed during the 3-day follow-up period favoured the local anaesthetic technique (p < 0.05). Postoperative analgesia requirements were greater in the general anaesthesia group than in the local anaesthesia group (p < 0.05). The majority of patients and surgeons expressed satisfaction with local anaesthesia. Sacrococcygeal local anaesthesia appears to be a successful alternative to general anaesthesia for pilonidal sinus surgery.     

Effect of intra-operative end-tidal carbon dioxide partial pressure on tissue oxygenation

Postsurgical infection risk is correlated with subcutaneous tissue oxygenation. Mild hypercapnia augments cutaneous perfusion. We tested the hypothesis that peripheral tissue oxygenation increases as a function of arterial PCO2 in surgical patients. Twenty patients were randomly assigned to intra-operative end tidal PCO2 of 3.99 (control) or 5.99 kPa (hypercapnia). All other anaesthetic management was per protocol. Tissue oxygen partial pressure, transcutaneous oxygen tension, cerebral oxygen saturation, and cardiac output were measured. Mean (SD) subcutaneous tissue oxygen tension was 8.39 (1.86) kPa in control and 11.84 (2.53) kPa hypercapnia patients (p = 0.014). Cerebral oxygen saturation was 55 (4)% for control vs. 68 (9)% for hypercapnia (p = 0.004). Neither cardiac index nor transcutaneous tissue oxygen tension differed significantly between the groups. Mild intra-operative hypercapnia increased subcutaneous and cerebral oxygenation. Increases in subcutaneous tissue oxygen partial pressure similar to those observed in patients assigned to hypercapnia are associated with substantial reductions in wound infection risk.     

Anaesthesia for Caesarean section: a survey in a UK region from 1992 to 2002

Data are presented for anaesthesia for Caesarean section (CS) in the South-west Thames region of the UK. The CS rate rose from 12.7% in 1987 to 24.2% in 2002. The rate of increase shows no sign of slowing. The rate of regional anaesthesia (RA) for elective CS rose from 69.4% in 1992 to 94.9% in 2002, when spinal anaesthesia was used for 86.6% of cases. This may limit the opportunities to teach other anaesthetic techniques. The rate of RA for emergency CS rose from 49.3% in 1992 to 86.7% in 2002. There is an unacceptable rate of failure of RA for both elective and emergency CS, 1.3% of RAs for elective CS and 4.9% of RAs for emergency CS were converted to general anaesthesia.     

A comparison of the effect of two anaesthetic techniques on surgical conditions during gynaecological laparoscopy

In a prospective, randomised, controlled trial, we compared the effects of two anaesthetic techniques on surgical conditions during day-case, gynaecological laparoscopic procedures in 40 female patients. Patients were allocated randomly to two groups, either to breathe spontaneously through a laryngeal mask airway or to receive a neuromuscular-blocking agent (NMB) and have the lungs ventilated via a tracheal tube. We then measured the number of attempts of Verres' needle insertion, initial intra-abdominal pressure, time to reach a steady 15 mmHg (1.97 kPa) of intra-abdominal pressure, adequacy of the pneumoperitoneum, operative view and duration of operation. We found that the initial intra-abdominal pressure was higher and the operation time shorter in the laryngeal mask group. The adequacy of the pneumoperitoneum for trocar placement was better in the NMB group. We conclude that the anaesthetic technique of spontaneously breathing through a laryngeal mask airway reduces total operation time. However surgeons should be aware of the different abdominal pressure patterns produced by each anaesthetic technique, and anaesthetists must consider the implications of the anaesthetic technique on surgical safety.