Compliance with the CONSORT checklist in obstetric anaesthesia randomised controlled trials

The Consolidated Standards for Reporting of Trials (CONSORT) checklist is an evidence-based approach to help improve the quality of reporting randomised controlled trials. The purpose of this study was to determine how closely randomised controlled trials in obstetric anaesthesia adhere to the CONSORT checklist. We retrieved all randomised controlled trials pertaining to the practice of obstetric anaesthesia and summarised in Obstetric Anesthesia Digest between March 2001 and December 2002 and compared the quality of reporting to the CONSORT checklist. The median number of correctly described CONSORT items was 65% (range 36% to 100%). Information pertaining to randomisation, blinding of the assessors, sample size calculation, reliability of measurements and reporting of the analysis were often omitted. It is difficult to determine the value and quality of many obstetric anaesthesia clinical trials because journal editors do not insist that this important information is made available to readers. Both clinicians and clinical researchers would benefit from uniform reporting of randomised trials in a manner that allows rapid data retrieval and easy assessment for relevance and quality.     

A case of extensive block with the combined spinal-epidural technique during labour

The increasing use of combined spinal-epidural analgesia in obstetric practice has arisen from a desire to achieve a rapid onset of analgesia while reducing the intensity of the motor block. Although the procedure has an excellent safety profile, as with any technique there are potential problems. Difficulty in assessing the position of the epidural catheter after establishment of the spinal blockade may lead to an abnormally extensive block when a full-strength local anaesthetic solution is used. We present a case in which the use of 0.5% bupivacaine to top-up the epidural component of a combined spinal-epidural resulted in a total spinal block. The possible causes of this complication are discussed.     

Hip flexion and lumbar puncture: a radiological study

When lumbar puncture is performed in the sitting position, the patient's thighs are usually at an angle of approximately 90 degrees to the trunk, whereas in the lateral position, hip flexion is employed by flexing the patient's knees to the chest. We measured the presumed but hitherto unquantified widening of lumbar interspinous spaces resulting from hip flexion. Lumbar spine lateral radiographs were taken in volunteers in the sitting position with and without hip flexion, and interspinous space width was measured and compared. Mean lumbar interspinous space width at L2-3, L3-4 and L4-5 increased by 7%, 11% and 21%, respectively, with the hips flexed. Hip flexion in the sitting position will anatomically optimise lumbar interspinous space width for needle passage, and statistically significant increases in space width have been demonstrated increasing progressively from L2-3 to L4-5.     

False-positive epidural catheter aspiration tests in needle through needle combined spinal-epidural anaesthesia

We describe two separate episodes of free aspiration of clear fluid through epidural catheters during needle-through-needle combined spinal-epidural anaesthesia in the lateral position. Although both catheters were assumed to have been located intrathecally, both subsequently gave negative test doses and were used as epidural catheters. In the second patient, the position of the catheter was investigated using contrast spiral computerised tomography scanning, which showed epidural contrast spread only. This is the first time such an occurrence has been recognised, and we consider its significance for catheter site confirmation testing in combined spinal-epidural anaesthesia.     

Acupuncture versus ondansetron in the prevention of postoperative vomiting. A study of children undergoing dental surgery

This study compares the anti-emetic effect of acupuncture with that of ondansetron and a placebo. Ninety children undergoing dental treatment under general anaesthesia were randomly allocated to one of the three equal groups, to receive acupuncture needle insertion, intravenous ondansetron 0.15 mg x kg(-1) or a placebo. Parental satisfaction scores and the incidence of emetic episodes were recorded. A significant difference was found in the number of patients who vomited and the total number of the emetic episodes when comparing the two treatment groups with the placebo group (p < 0.0001). A significant difference was also found between the treatment groups and the placebo group with respect to parental satisfaction score (p < 0.03). We conclude that traditional Chinese acupuncture is a valid non-pharmacological alternative anti-emetic treatment that can be recommended as a prophylactic technique in children undergoing dental surgery under general anaesthesia.     

Speed of collapse of the non-ventilated lung during single-lung ventilation for thoracoscopic surgery: the effect of transient increases in pleural pressure on the venting of gas from the non-ventilated lung

A study of 10 anaesthetised patients placed in the lateral position for thoracoscopic surgery assessed whether transient increases in pleural pressure on the side of the non-ventilated lung might increase the speed at which gas vents from that lung. The transient increases in pleural pressure were generated by the mediastinal displacement that occurs with each inspiratory phase of positive pressure ventilation of the dependent lung. When combined with a unidirectional valve allowing gas to flow out of the non-ventilated lung, and a second valve allowing ambient airflow into, but not out of, the thoracic cavity via an initial thoracoscopy access site, this mediastinal displacement could conceivably serve to 'pump' gas out of the non-ventilated lung. Using the four different combinations of valve inclusion or omission, the volume of gas that vented from the non-ventilated lung into a measuring spirometer was recorded during a 120-s measurement sequence. It was found that the speed of venting was not increased by the transient increases in pleural pressure, and that in all but one of a total of 34 measurement sequences, venting had ceased by the end of the sequence. Gas venting was a mean (SD) of 85.5 (11.9)% complete in 25 s (five breaths), and 96.6 (6.1)% complete in 60 s. This prompt partial lung collapse very likely reflected the passive elastic recoil of the lung, while the failure of transient increases in pleural pressure to result in ongoing venting of gas was probably a consequence of airways closure as the lung collapsed. It is concluded that techniques that aim to speed lung collapse by increasing pleural pressure are unlikely to be effective.     

The effect of nitrous oxide on the inhibition of somatosensory evoked potentials by sevoflurane in children

Inhalational anaesthetics inhibit somatosensory evoked potentials. The present study examined the effect of nitrous oxide in anaesthetic mixture with sevoflurane on the somatosensory evoked potential in children. Forty-five patients aged between 6 months and 6 years undergoing club foot surgery were studied to verify the influence of sevoflurane alone (21 patients) and sevoflurane with nitrous oxide (24 patients) on the somatosensory evoked potential. Fractional inspired concentration of nitrous oxide and fractional end-tidal (alveolar) sevoflurane were measured to estimate the multiples and submultiples of the minimal alveolar concentration (age corrected). The somatosensory evoked potential signals were obtained by stimulation of the median nerve. Nitrous oxide (FI = 0.63 +/- 2.5) with sevoflurane caused more reduction in the amplitude of somatosensory evoked potential waves and a greater increase in the latency of somatosensory evoked potential waves in comparison with sevoflurane alone. The results show that it is possible to obtain the inhibition of somatosensory evoked potential with smaller concentrations of sevoflurane, when it is used with nitrous oxide.     

Increased extracellular glutamate in rat prefrontal cortex: movement artifact contribution

Extracellular glutamate levels were measured by microdialysis in the prefrontal cortex (PFC) of anaesthetised rats in response to a short, experimenter-provoked mechanical movement of the animal head. Movement caused significant, nerve impulse-independent elevations of glutamate levels (maximum increase, 300+/-30% of baseline). This study reveals a possible artifact in the measurement of extracellular glutamate concentrations by microdialysis and suggests that, in awake animals, treatments associated with stimulation of motor activity can cause non-specific efflux of glutamate in the PFC.     

Halothane-Relaxant Anaesthesia in Elderly Patients

Twenty-three elderly patients, scheduled for elective cholecystectomy, were studied during halothane-relaxant anaesthesia. Anaesthesia was induced with thiopentone and maintained with halothane in 12 patients, six of whom had also received premedication. Eleven patients were anaesthetized with halothane, without thiopentone induction and with no premedication. Measurements of central haemodynamics were performed awake and during anaesthesia at end-tidal halothane concentrations of 0.5 and 1.0%; at the lower concentration, measurements were also made after addition of nitrous oxide. Premedication and thiopentone had no influence on the subsequent halothane anaesthesia. Halothane caused reductions of cardiac index, mean arterial blood pressure and oxygen uptake. However, neither right atrial nor pulmonary capillary venous pressure increased and the arterio-venous oxygen content difference decreased. These findings differ from those made by others in younger subjects and are probably attributable to a dose-dependent reduction in systemic vascular resistance. The addition of nitrous oxide had only minor effects on central circulation. The results suggest that the age of the patients influences their reaction to halothane anaesthesia.