HYPNOTIC AND ANAESTHETIC ACTION OF THIOPENTONE AND MIDAZOLAM ALONE AND IN COMBINATION

This study examined the interaction between i.v. administeredmidazolam and thiopentone on the loss of response to verbalcommand ("hypnosis") and the loss of response to transcutaneouselectrical stimulation of the ulnar nerve ("anaesthesia") inpatients presenting for minor elective surgery. Dose-responsecurves for thiopentone and midazolam individually and in combinationwere determined using the two end-points in 300 unpremedicatedpatients. For hypnosis a highly significant (P < 0.001) supraaddictive(synergistic) interaction was found, the combination having1.8 times the expected potency of the individual agents. Althoughmidazolam failed to produce anaesthesia in the dose range used,the dose of thiopentone required to produce anaesthesia wasreduced by 50% in the presence of midazolam. The mechanism ofinteraction and the potential role of benzodiazepine-barbituratecombinations are discussed and the observed synergistic anaesthesiainteraction is used to explain the potentially dangerous combinationof benzodiazepines with other potent CNS depressants such asbarbiturates and alcohol. ^*Present address: Prince of Wales Hospital, Shatin, Hong Kong.     

THIOPENTONE AND ETOMIDATE CONCENTRATIONS IN MATERNAL AND UMBILICAL PLASMA, AND IN COLOSTRUM

We have measured concentrations of etomidate and thiopentonein maternal plasma, umbilical venous plasma and colostrum afterinduction of anaesthesia in 40 patients undergoing Caesareansection. Mean plasma etomidate concentration declined rapidly(1242.0 ng ml^–1 at 5 min, 434.0 ng mt1 at 15 min, 64.2ng ml^–1 at 30 min, 7.0 ng ml^–1 at 60 min and undetectable2 h after the injection). Mean plasma concentrations of thiopentonedeclined more slowly (6.09 µg ml^–1 at 5 min, 2.64µg ml^–1 at 2 h, 1.35 ng ml^–1 at 4 h, 0.86ng ml^–1 at 9 h and 0.59 ng ml^–1 at 12.h). Mean umbilicalvenous thiopentone concentration was 4.72 µg ml^–1.whereas the thiopentone concentration in the maternal sampleat 5 min was 6.09 g ml^–1, giving an umbilical.maternalvein ratio of 1:1.3. Mean umbilical etomidate concentrationwas 51.7 ng ml^–1 and the corresponding maternal vein sample(5 min) was 1242.0 ng ml^–1 (P < 0.001), giving an umbilical:maternal vein ratio of 1:24. Mean concetrations of thioptonein colostrum were 1.98 µg mt^–1 at 30 min, 0.91 gmt1 at 4 h and 0.59 µg ml^–1 at 9 h, colostrum .plasmaratios at 4 h and 9 h being 0.67 and 0.68, respectively. Meanconcentrations of etomidate in colostrum were 79.2 ng ml^–1at 30 min and 16.3 ng ml^–1 at 2 h. being undetectableat 4 h. The colostrum:plasma etomidate concentration ratio was1.2 at 30 min. We conclude that, although plasma and colostrumconcentrations of thiopentone and etomidate declined rapidly,the decrease was faster with etomidate.     

RESPIRATORY AND HYPNOTIC EFFECTS OF NITRAZEPAM, DIAZEPAM AND PENTOBARBITONE AND THEIR SOLVENTS IN THE RABBIT AND THE MOUSE

Nitrazepam and diazepam only cause significant depression ofrespiratory rate and loss or righting reflex, in mice, at lethaldoses. In sub-lethal doses they induce a stage of deep but rousablesleep which is quite distinct from the intermittent dozing ofcontrol mice and the comatose state of mice injected with pentobarbitone.However, the respiratory effects of nitrazepam and diazepamin high doses in mice and low doses in rabbits are modifiedby the presence of solvent. Furthermore the solvent itself causesa loss of righting reflex in mice and the lethal dose of nitrazepamand diazepam is greatly reduced when the drugs are administeredin solvent     

OBSERVATIONS OF BLOOD LACTATE AND PYRUVATE LEVELS AND EXCESS LACTATE PRODUCTION DURING AND AFTER ANAESTHESIA WITH AND WITHOUT HYPERVENTILATION

Arterial blood levels of lactate and pyruvate and the productionof excess lactate were studied in two groups of patients. Onegroup of ten patients was anaesthetized with <1 per centhalothane, nitrous oxide and oxygen and allowed to breathe spontaneously.The second group of twelve patients was anaesthetized with nitrousoxide and oxygen, and additional trichloroethylene or papaveretum,and deliberately hyperventilated. No significant changes werefound in lactate or pyruvate during anaesthesia in the firstgroup, but there was a significant increase in the lactate:pyruvate ratio half an hour after recovery from the anaesthetic.Significant excess lactate production occurred during anaesthesiain the second group after hyperventilation had been in progressfor half an hour. The excess lactate increased after 1 hourof hyperventilation and further increases were found half anhour after recovery from the anaesthetic. These findings arediscussed in relation to the observed changes in blood-gas levelsand acid-base balance and to the current knowledge of carbohydratemetabolism.     

VENTILATION AND GAS EXCHANGE DURING ANAESTHESIA AND SURGERY IN SPONTANEOUSLY BREATHING INFANTS AND CHILDREN

Minute ventilation (VE) (mlmin^–1), respiratory frequency(f), mixed expired carbon dioxide fraction (FCO₂ and end-tidalcarbon dioxide concentration E'CO₂) (%) were measured, and alveolarventilation (VA), deadspace (VD), deadspace/tidal volume ratio(VD/VT) and carbon dioxide output (VCO₂) calculated in 58 anaesthetized,spontaneously breathing infants and children weighing 2.8–20.5kg.Although minute volumes varied, tidal volume correlated wellwith weight (r = 0.83), with a mean tidal volume (± ISD)of 5.2±1.2mlkg^–1. It was concluded that, by theuse of mean VT + ISD (approximated to 6 ml kg^–1) the freshgas flow in mlmin^–1 should be set at 2.5x6xkgxf(15xkgxf)to avoid rebreathing in various T-piece systems in anaesthetized,intubated and spontaneously breathing infants up to a body weightof 20 kg. End-tidal carbon dioxide concentration was lower inyounger patients who were premedicated with atropine alone thanin the older ones who received opioid premedication also. Respiratoryfrequency, VD/VT and total VD per minute were higher in theyounger age group, which explained the finding of a high VEin relation to VCO₂ for these patients. This inefficiency ofventilation emphasizes the need to minimize apparatus deadspacein breathing systems used for small infants. ^*Department of Anaesthesia, University Hospital, S-22185 Lund,Sweden. Department of Anaesthesia, St George's Hospital, Blackshaw Road,London SW17.     

STRESS AND AROUSAL CIRCADIAN RHYTHMS IN SMOKERS AND NON-SMOKERS WORKING DAY AND NIGHT SHIFTS

Twenty smokers and twenty non-smokers completed a brief Mood State Questionnaire every 2 hours, over one day shift and one night shift. The subjects comprised male police officers and factory workers, aged 23–57 years. Cigarette smokers reported significantly higher stress levels than non-smokers on both day and night shifts (p<0.05). This confirms previous findings that smokers are often more stressed than non-smokers. Stress levels varied over time within each shift (p<0.001), but the circadian patterns did not differ between smokers and non-smokers. Thus smoking did not alter circadian mood rhythms, nor did it facilitate stress control. Self-rated levels of arousal showed the archetypal inverted-U pattern over time in both smokers and non-smokers. There was no difference in mean arousal levels between subgroups, indicating that cigarettes did not lead to greater alertness. The shift×time interaction was significant for both stress (p<0.001) and arousal (p<0.003), indicating different circadian rhythms during the day shift and the night shift. Finally, while smokers consumed slightly more cigarettes during the night shift than day shift (22.3, 19.4 respectively, p<0.05), mean stress and arousal levels did not differ between shifts. The implications of these findings for smoking behaviour are discussed. © 1997 by John Wiley & Sons, Ltd.     

多发、复杂肝内胆管结石的诊治

目的探讨多发性、复杂性肝内胆管结石的诊治方法。方法对我院近8年来的23例多发复杂性肝内胆管结石的病人诊治经验结合文献进行分析。结果这些病例手术后残留结石率高达65．2％,比一般的肝内胆管结石术后残留率30．36％高得多,且严重并发症发生并死亡率高达17．4％。结论多发、复杂性的肝内胆管结石病人的诊治是长期来难以突破的重大临床问题,术前的“个体化”诊疗方案和术式选择是提高疗效的关键。     

OXYGEN CONSUMPTION AND CARBON DIOXIDE ELIMINATION IN INFANTS AND CHILDREN DURING ANAESTHESIA AND SURGERY

Oxygen consumption (VO₂, ml min^–1) and carbon dioxideelimination (VCO₂, ml min^–1), minute ventilation (VE),tidal volume (VT), rate of ventilation (f) and end-tidal carbondioxide concentration (E' _co2 %) were measured in 38 infantsand children (body weights 3.6–25 kg). Four children (bodyweight < 5 kg) had congenital heart malformations and werestudied during controlled mechanical ventilation, where-as theremainder (n = 34) who were healthy, breathed spontaneously.Anaesthesia was maintained with oxygen in air (Fl_O2 0.45) andhalothane through a non-rebreathing circuit. Minute ventilationwas measured by pneumo-tachography, E'_CO2 with an in-line infra-redcarbon dioxide meter and gas concentrations with a mass spectrometer.There were no differences in VO₂ and VCO₂ between children withand without heart disease. VO₂ was related to body weight bythe equation: VO₂ = 5.0xkg+19.8 (r = 0.94) and VCO₂ to bodyweight by the equation: VCO₂ = 4.8xkg+6.4 (r = 0.94). Therewere no differences between VO₂ or VCO₂ before and after thestart of surgery. In 11 of 21 patients weighing less than 10kg, a reduced VCO₂ was noted, giving respiratory quotients ofless than 0.7. It is speculated that this age-dependent variationof VCO₂ may result from partial inhibition of lipolysis in brownadipose tissue produced by halothane.     

胆囊腺瘤及癌变的诊断与治疗

目的　探讨胆囊腺瘤的诊治和腺瘤癌变的高危因素。方法　回顾性分析 2 4例胆囊腺瘤的临床资料。结果　胆囊腺瘤无特殊临床表现 ,B超是发现胆囊腺瘤的主要方法。 2 4例中腺瘤 14例 ,腺瘤癌变 10例 ,癌变率为 4 1.7%。腺瘤癌变组平均病程 (4 7.0± 36 .2 8月 )、肿瘤直径 (2 4 .6 0± 13.2 3mm )均显著高于腺瘤组 (11.2 9± 8.83月 / 12 .14± 6 .36 mm ) (P<0 .0 1) ;且腺瘤癌变组均为广基肿瘤 (10 0 % ) ,多合并胆囊结石 (70 % )、慢性胆囊炎 (90 % ) (P<0 .0 5 )。结论　胆囊腺瘤有较高癌变率。对 5 0岁以上 ,病程大于 2年 ,合并胆囊结石 ,慢性胆囊炎的患者 ,发现直径大于 12 mm的广基胆囊腺瘤 ,应积极手术治疗。