Background and objective Low-flow anaesthesia is economical and less polluting. The purpose of this study was to determine the inspired and end-tidal desflurane concentrations during anaesthesia with a vaporizer setting maintained at 5%, during low-flow anaesthesia after 120 min with fresh gas inflows of 1.0 and 2.0 L min−1.

Methods The study was both prospective and randomized, including 56 patients (28 patients in each group) scheduled for elective surgery of an expected anaesthesia time of at least 120 min. Inspired and end-tidal concentrations of desflurane were measured during low-flow anaesthesia with fresh gas inflows of 1.0 and 2.0 L min−1. The vaporizer setting was fixed at 5% desflurane.

Results The inspired and end-tidal concentrations of desflurane in the 1.0 L min−1 group after 120 min were 4.54% vs. 4.37% (P < 0.001). In the 2.0 L min−1 group, the inspired and end-tidal concentrations of desflurane were 4.76% vs. 4.58% (P < 0.001). The estimated end-tidal/inspired ratios at 120 min of anaesthesia were 0.96 in both groups. At a fresh gas flow of 1.0 L min−1, the end-tidal concentration was 0.87 of the vaporizer setting. Increasing the fresh gas flow to 2.0 L min−1 increased the end-tidal value by 0.05.

Conclusion There is a significant difference between the inspired and end-tidal concentrations of desflurane when fresh gas inflows were 1.0 and 2.0 L min−1, but not for the ratio of inspired/end-tidal.

Summary

Ion channels regulate a diversity of physiological functions such as neuronal signalling, cardiac excitability and immune cell response. All of these systems may be affected during the conduct of general as well as local anaesthesia. Thus, the investigation of anaesthetic action on ion channels has become the focus of an increasing number of laboratory studies. Consequently, the concepts of ion channel physiology are becoming important for understanding the scientific and pharmacological basis of clinical anaesthesia. This brief guide is intended to help in understanding the increasing number of studies concerned with the effects of anaesthetic agents on ionic currents. The generation of ionic currents requires a complex molecular interplay of ions, ion channel proteins and lipid membranes. Anaesthetic agents frequently exhibit more than a single effect on ion channel function. Their effects can be described by quantifying the pharmacological alteration of ion channel activation, conductance and inactivation. Many physiological functions are directly influenced by ion channels. Pharmacological action on ion channels is thus fundamental to effects as well as side-effects of anaesthetic agents. The alteration of ion channel function by anaesthetic agents consequently determines their clinical effects.

Patients undergoing mitral valve surgery are at risk of left ventricular failure in the immediate post-operative period. In order to understand better the mechanisms of post-operative haemodynamic instability, we used transoesophageal echocardiography to assess the immediate response of the left ventricle to mitral valve replacement for mitral regurgitation or stenosis. A decrease in left ventricular preload, despite adequate filling pressures, was common to both groups and suggests the presence of diastolic dysfunction. A marked impairment in global systolic pump function was observed only in the regurgitation group and correlated with the left ventricular afterload. Transoesophageal echocardiography provides valuable information on the individual changes in left ventricular function and its determinants after mitral valve replacement that are not reflected by haemodynamic measurements.

Summary

Background and objective: The aim of this study was to investigate the quality of intra- and postoperative analgesia obtained by alfentanil compared to that produced by peripheral blockade in children.

Methods: During sevoflurane-nitrous oxide atracurium anaesthesia for minor abdominal or genito-urinary surgery, three groups of children aged 0–8 yr received 25 μg kg−1 alfentanil intravenously (n = 28), or peripheral nerve blockade using 1 mL−1 ropivacaine 0.475% (n = 24), or 12.5 μg kg−1 alfentanil intravenously with peripheral nerve blockade using 1 mL kg−1 ropivacaine 0.475% (n = 30). Changes in blood pressure and heart rate were measured during the procedures. Postoperative pain was assessed using the face, legs, activity, cry, consolability (FLACC) observational tool for quantifying pain behaviour and a numerical scale scored by nurses, doctors, parents and children.

Results: There was no significant difference in intra- or postoperative analgesic efficacy among the three groups. Patients who received alfentanil had significantly lower heart rates than those who received nerve blockade only (96.0 ± 15.6 vs. 115.9 ± 23.2 beats min−1, P < 0.001). FLACC and numerical scale scores did not differ among the groups. There were no significant differences in incidence of vomiting or use of pain medications.

Conclusions: It was concluded that a low-dose, intravenous bolus of alfentanil may be an efficient alternative to peripheral nerve blockade in controlling pain during and after minor abdominal and genito-urinary surgery.

The present study contrasted the pharmaco-economics and analgesic efficacy of intramuscular (i.m.) opioid treatment with a parenteral disposable patient-controlled analgesia (PCA) system in two groups of 20 female patients (ASA I–II, aged 35–69 years) scheduled for abdominal hysterectomy. The PCA group received a continuous infusion of 1.5 mg h−1 piritramide, a μ-opioid receptor agonist, with incremental doses of 1.5 mg (lock-out interval=15 min). The i.m. group received 0.3 mg kg−1 piritramide i.m. when requested by the patient with a minimum interval of 5 h. Pain intensity, sedation and the functional recovery of the patients were followed for 72 h post-operatively. The sum of pain intensity differences (SPID) was used as a measure of analgesic efficiency. Equipment and drug costs, and the demand on nursing time were recorded over 3 days post-operatively. The costs of PCA and i.m. therapies per patient were used to calculate the cost-benefit (cost of treatment vs. nursing time) and cost-effectiveness (cost of treatment vs. SPID) analyses. Both treatments initially provided comparable analgesia, but PCA was more efficient after 16 h and significantly reduced nursing time for pain treatment (PCA=61±4 min, i.m.=88±5 min; P<0.001). Functional recovery was not different for either treatment. Cost analysis indicated a better cost-benefit ratio for the i.m. treatment (0.35 vs. 1.1 for PCA treatment), but a similar cost-effectiveness for both treatments (PCA=1.9 Belgian Francs (BEF) unit−1 SPID; i.m.=1.7 BEF unit−1 SPID).

Background and aim Infusion of ketamine and midazolam can maintain prolonged anaesthesia, but delayed recovery is a limitation. We aimed to develop an approximation regimen for the infusion of ketamine and midazolam to obtain steady-state anaesthesia with acceptable recovery.

Methods Thirty-one patients undergoing radical cystect-omy were studied. The initial regimen was calculated from drug pharmacokinetic variables and tailored in a pilot study (15 patients) to develop the approximation regimen dosage. Anaesthesia was induced with midazolam (150μgkg−1) and ketamine (2mgkg−1). Tracheal intubation and ventilation with oxygen enriched air (FiO2 = 0.35) were facilitated by muscle relaxants. Anaesthesia was maintained by the approximation regimen doses. Routine monitoring was used for all patients, but pulmonary artery catheters were inserted in 11 patients, to obtain haemo-dynamic and oxygenation variables.

Results Steady-state anaesthesia was obtained with minimal deviations in the regimen in some patients followed by reasonable recovery.

Conclusion It is concluded that infusion of ketamine and midazolam in the approximation regimen doses can be used to maintain anaesthesia for prolonged abdominal surgery.

The cuffed oropharyngeal airway (COPA) was compared with the laryngeal mask airway (LMA) with respect to airway quality and respiratory adverse events in 140 spontaneously breathing patients undergoing procedures of duration more than 1 h. Patients were allocated randomly to receive either a COPA (n=72) or a LMA (n=68) for airway management during anaesthesia induced with propofol and maintained with sevoflurane, nitrous oxide and oxygen. Groups were similar when comparing the first-time successful insertion rates (COPA: 94.5%, LMA: 95.6%), but airway manipulations (head tilt, chin lift, jaw thrust) were reported more frequently in the COPA group, 27.8% vs. LMA, 4.4%; P=0.0005. During the post-induction apnoeic period, all patients were ventilated manually and although, mean (SD) leak pressure was lower in the COPA group (18 (4) cm H2O vs. LMA, 22 (3) cm H2O; P< 0.0001), the tidal volumes achieved did not differ in both groups: COPA, 9.5 (4) mL kg−1 vs. LMA, 10.5 (4.5) mL kg−1. The incidences of intra-operative coughing, gagging, laryngospasm, oxygen desaturation and hypercarbia were similar in both groups. Although both devices are equivalent with respect to the overall respiratory problems during spontaneous breathing anaesthesia of intermediate or prolonged duration, the LMA was associated with fewer airway quality problems, suggesting that it is more efficacious in securing the airway.

Chondronecrosis of the cricoid cartilage is a rare complication of intubation. The records of two children were reviewed. An 8-month-old girl with myelomonocytic leukaemia developed chondronecrosis 10 days after a 2-day period of ventilation. A 4-year-old girl comatose after poisoning by the histamine antagonist, alimemazine, developed chondronecrosis after a 2-day period of intubation. The complication was suspected when extubation led to dyspnoea owing to laryngeal stridor and was confirmed by direct laryngoscopy. We review the development of the condition, the causative factors, treatment and prevention.

The occurrence of a pneumothorax in a 4-week-old infant is described. The cause of the problem is believed to have been a kink in the silastic reservoir tube. The failure of the monitors to detect the event and methods of improving safety are discussed. Difficulties may occur even with familiar equipment; the value of full monitoring and constant vigilance are stressed.

Summary

Background and objective: A retrospective analysis of applicants to Specialist Registrar training posts in anaesthesia in the Wessex Region of the UK was undertaken.

Methods: Applicants whose primary medical qualification was obtained in the European Economic Area were compared to applicants whose primary medical qualification was obtained outside it. The time since qualification, the time spent in anaesthesia, the time spent in other specialities, the post currently held and the success of the application were recorded.

Results: For doctors with a primary medical qualification from outside the European Economic Area, the median time since obtaining that qualification was 12.0 yr compared with 6.0 yr for doctors qualifying within it (P = 0.0001, U-test). Thirteen out of 89 (15%) doctors whose primary medical qualification was from outside the European Economic Area and 39 out of 61 (64%) doctors whose primary medical qualification was from within it were shortlisted for interview (P = 0.0001, χ2-test). Six out of 13 (46%) shortlisted doctors from outside the European Economic Area were appointed at interview compared with 24 out of 39 (62%) shortlisted doctors who qualified within it (P = 0.33, χ2-test).

Conclusions: In the Wessex Region of the UK, applicants whose primary medical qualification is obtained within the European Economic Area are approximately four times as likely to be shortlisted than doctors qualifying outside it. However, after shortlisting, both categories are equally likely to be successful at interview.

Aprotinin has been reported to influence positively or negatively the process of ischaemia-reperfusion. However, it is a complex drug acting on platelets, neutrophils and coagulation, which may also have a direct effect by inhibiting intracellular proteases and free radical generation. The goal of this study was to determine the direct effects of aprotinin on the myocardial performances of an isolated blood perfused rabbit heart preparation after normothermic global ischaemia. Two groups of 10 hearts were studied. The control group (ischaemia) underwent 30 min of global normothermic ischaemia. In the aprotinin group, (aprotinin) 200 KUI mL−1 of aprotinin was added to the perfusate before ischaemia. Measurements were obtained at base-line, 10, 30 and 60 min after reperfusion. Normothermic ischaemia significantly decreased myocardial performance in both groups. After 60 min reperfusion, myocardial contractility significantly recovered in the aprotinin group compared with the ischaemia group. Aprotinin contributes significantly by limiting the consequences of ischaemia on myocardial performances. This effect may be due to a direct action of the drug because leucocytes and plasma proteins were removed in this preparation.

Oxygen consumption (̇Vo2) measured by indirect calorimetry (Nellcor-Puritan-Bennett 7250; Carlsbad, CA, USA) has been compared with ̇Vo2 calculated by the Fick method in 22 volume-controlled ventilated general surgical patients in the early post-operative period. For 198 pairs of measurements, ̇Vo2 Fick and ̇Vo2 indirect calorimetry correlated significantly (y=1.00x–35.8, P=0.0001, r=0.77). ̇Vo2 indirect calorimetry was 212±32 mL min−1 and ̇Vo2 Fick was 177±41 mL min−1 (P=0.0001). The bias was 35±26 mL min−1. This difference represents 16±13% of the total body ̇Vo2. ̇Vo2 calculated by the Fick method did not accurately predict ̇Vo2 measured by indirect calorimetry, and the two methods were not interchangeable. ̇Vo2 calculated by the Fick method underestimated ̇Vo2 as measured by indirect calorimetry by a systematic quantity that could be attributed, in part, to ̇Vo2 of the lung. Indirect calorimetry should be the preferred method for measuring total body ̇Vo2 in mechanically ventilated surgical patients.

A 74-year-old woman was scheduled for surgical treatment of a carpal tunnel syndrome. An intravenous (i.v.) regional anaesthetic was performed using 1% prilocaine standard technique. Three minutes after injection of the local anaesthetic mild to moderate central nervous system symptoms developed, along with tachycardia, sweating and peri-oral paraesthesia. The evolution was favourable, no convulsions or other more serious events occurred. Despite showing adequate pressure inflation the tourniquet failed to accomplish its purpose. The patient recovered well without any sequelae.

General anaesthesia for a patient with tuberous sclerosis was complicated by epilepsy. The choice of drugs was related to control of his fits and intercurrent therapy. Thiopentone, vecuronium, and nitrous oxide with isoflurane were satisfactory.

Local anaesthetics injected into the epidural space may deform the dural sac to a variable degree, thereby contributing to variability in the extent of the block. We investigated deformation of the lumbar dural sac after injection into the lumbar epidural space. The subjects were 26 patients with low-back pain who underwent lumbar epidurography and computed tomographic (CT) epidurography, of whom seven also underwent myelography and computed tomographic myelography. The epidural space was entered via the sacral hiatus in 24 patients and through the L5/S1 interspace in two patients. Ten millilitres of local anaesthetic was then injected into the epidural space followed by 20 mL of contrast medium. Computed tomographic epidurography was undertaken approximately 30 min after the epidural injection at the mid-vertebral and mid-discal levels from the first lumbar through to the first sacral vertebrae. The dural sac usually showed an oval or hexagonal shape on the transverse views at the first and second lumbar vertebral levels, and the shape of an inverted triangle below the level of the third lumbar vertebra. A median line of translucency was also observed on the postero-anterior epidurographic view in 25 of the 26 patients. This line was thought to be a manifestation of the dural deformation to the inverted triangle. Dural sac deformation usually shows a specific pattern, although there are individual variations. Dural deformability is an important consideration in any analysis of the spread of epidural block or of the changes of epidural pressure after epidural injection of local anaesthetics.