Summary

Subarachnoid haemorrhage due to rupture of cerebral aneurysms is a multisystem disease. Treatment of the condition in the past has relied on craniotomy and clipping of the aneurysm to prevent a recurrent haemorrhage. There is now emerging evidence to suggest that endovascular treatment of cerebral aneurysms may reduce the morbidity associated with open surgery. The anaesthetic management of interventional neuroradiology also creates new challenges due to the novel approach to treatment. Anaesthetists need to be familiar with this procedure and the management of potential complications. This review provides an overview such considerations.

Summary

Closed circuit anaesthesia was described decades ago but did not achieve wide popularity among anaesthesiologists mainly because reliable control of inspiratory gas concentrations was not possible. Recent innovations including fast gas analysers, electronically controlled dosage systems and algorithms for feedback control have made possible the development of sophisticated closed circuit ventilators designed for routine clinical practice. The main advantages comprise economic use of medical gases and volatile anaesthetics, reduction of anaesthetic gas loss into the atmosphere, improved airway acclimatization as well as estimations of oxygen consumption. This article reviews historical aspects, recent developments as well as advantages and limitations of closed system anaesthesia.

Summary

Background and objective: Awareness with postoperative recall of intraoperative events is a rare but serious complication of general anaesthesia. This survey investigated the attitude of anaesthetists in the UK to awareness and depth of anaesthesia monitoring. Methods: Questionnaires were sent to 4927 consultant anaesthetists in 285 hospitals in the UK in September 2004. The responses were recorded in an electronic database, summarized and compared with the results of studies performed in Australia and the USA. Results: The response rate was 44%. When judged against published awareness rates, anaesthetists underestimated the incidence of awareness in their own practice (median 1: 5000). One-third of respondents have dealt with patients who have experienced intraoperative recall. The majority of anaesthetists perceived awareness as a minor problem on an 11-point scale (modal score 2, median score 3, IQR 2–5). Eighty-six percent of anaesthetists considered clinical signs unreliable but 91% felt that measurement of end-tidal anaesthetic agent concentration reduces the likelihood of awareness. The majority of anaesthetists would use a monitor at least some of the time if one was available to them. Overall, the attitudes of anaesthetists in the UK, USA and Australia are remarkably similar. Conclusions: Anaesthetists tend not to view awareness as a serious problem. Although most accept that clinical signs are unreliable indicators of awareness, few believe that monitors of anaesthetic depth should be used for routine cases.

Summary

Background and objective: Derived parameters of the electroencephalogram and auditory evoked potentials can be used to determine depth of anaesthesia and sedation. However, it is not known whether any parameter can identify the occurrence of awareness in individual patients. We have compared the performance of bispectral index and a new composite index derived from auditory evoked potentials and the electroencephalogram (AAI 1.61) in predicting consciousness, explicit and implicit memory during moderate sedation with propofol. Methods: Twenty-one patients with spinal anaesthesia received intraoperatively propofol at the age-corrected C50 for loss of consciousness and were presented test words via headphones. Bispectral index and AAI 1.61 (auditory evoked potentials, AEP-Monitor2) were recorded in parallel as well as the Observer's Assessment of Alertness/Sedation-score. Postoperatively, testing for explicit and implicit memory formation was performed. Results: Bispectral index and AAI 1.61 correlated well with loss of consciousness defined by an Observer's Assessment of Alertness/Sedation-score of 2 (identical PK of 0.87), but did not allow a prediction of postoperative explicit or implicit recall. Conclusions: Both bispectral index and AAI may be indices of depth of sedation rather than indicators of memory formation, which persists during propofol sedation even after loss of consciousness.

Summary

Background and objective: To evaluate and compare the effect of two clinically available central nervous system stimulants, namely doxapram and aminophylline on arousal from sevoflurane anaesthesia and bispectral index. Methods: This randomized, double-blind, placebo-controlled, prospective study was conducted in 90 adult females, ASA I–II, scheduled for elective lower abdominal surgeries at Taipei Medical University Hospital. At 5 min before the completion of surgery, under sevoflurane anaesthesia, patients were divided into three groups to receive doxapram 1 mg kg−1, aminophylline 2 mg kg−1 or saline placebo intravenous. Standard vital signs, end-tidal CO2, end-expiratory sevoflurane concentration, bispectral index and neuromuscular blockade were measured plus clinical parameters of recovery from general anaesthesia. Results: Compared with the control group, patients receiving doxapram or aminophylline showed a similarly faster recovery from sevoflurane anaesthesia correlated with increase in bispectral index. Conclusion: Intravenous administration of doxapram 1 mg kg−1 or aminophylline 2 mg kg−1 hastened the early recovery from sevoflurane anaesthesia. The arousal effect of aminophylline and doxapram appears to be similar.

Summary

Background: Leucocytes are a pivotal component of the inflammatory cascade that results in tissue injury in a large group of disorders. Free radical production and endothelial activation promote leucocyte–endothelium interactions via endothelial expression of vascular cell adhesion molecule 1 (VCAM-1) and intercellular adhesion molecule 1 (ICAM-1) which augment these processes, particularly in the setting of reperfusion injury. Propofol has antioxidant properties which may attenuate the increased expression of these molecules that is observed. Methods: Cultured human umbilical vein endothelial cells were exposed to 20 h of hypoxia, then returned to normoxic conditions. Cells were treated with saline, Diprivan® 5 μg mL−1 or propofol 5 μg mL−1, for 4 h after reoxygenation and were examined for ICAM-1 and VCAM-1 expression. Results: Hypoxia did not increase the expression of ICAM-1/VCAM-1. ICAM-1 expression peaked 12 h after reoxygenation (21.75(0.6) vs. 9.6(1.3), P = 0.02). Propofol, but not Diprivan®, prevented this increase (8.2(2.9) vs. 21.75(0.6), P = 0.009). VCAM-1 expression peaked 24 h after reoxygenation (9.8(0.9) vs. 6.6(0.6), P = 0.03). Propofol and Diprivan® prevented this increase, with no difference between the two treatments observed (4.3(0.3) and 6.4(0.5) vs. 9.8(0.9), P = 0.001, 0.02, respectively). Conclusion: These effects are likely to be attributable to the antioxidant properties of propofol, and suggest that propofol may have a protective role in disorders where free radical mediated injury promotes leucocyte–endothelium adhesive interactions.

Summary

Background and objective: Propofol has been shown to inhibit a variety of functions of neutrophils in vitro, but there is a lack of in vivo data. To analyse the effects of propofol on neutrophil function in vivo we chose to investigate cataract surgery since it represents a small surgical procedure with minimal immunomodulatory effects induced by surgery. We sought to analyse any immunosuppressive effects of propofol after short-term administration in vivo in comparison to local anaesthesia as well as to in vitro effects of propofol. Methods: The study was designed as an open randomized trial enrolling 20 patients undergoing general or local anaesthesia. The neutrophil oxidative response and propofol plasma concentration were assessed prior, during and after anaesthesia. Neutrophil function was determined flow cytometrically based on dihydrorhodamine 123 oxidation. Results: Propofol concentrations which yielded a marked suppression in vitro did not alter the neutrophil oxidative response during cataract surgery in vivo. However, after local anaesthesia the neutrophil oxidative response declined to 37%, compared to the control response prior to anaesthesia. Conclusions: Although we could detect the well established suppression of neutrophil function by propofol in vitro it was not evident in vivo. This may be due to compensating effects on neutrophil function during surgery in vivo. The decline in the neutrophil oxidative response in the local anaesthesia group might be due to increased stress and catecholamine concentrations or a direct interaction of local anaesthetics with neutrophil intracellular signalling.

Summary

Background and objective: Measurement of central blood volumes (CBV), such as global end-diastolic volume (GEDV) and right ventricular end-diastolic volume (RVEDV) are considered appropriate estimates of intravascular volume status. However, to apply those parameters for preload assessment in mechanically ventilated patients, the influence of tidal volume (TV) and positive endexpiratory airway pressure (PEEP) on those parameters must be known. Methods: In 13 mechanically ventilated piglets, the effect of low (10 mL kg−1) and high (20 mL kg−1) TVs on CBV was investigated in absence and presence of PEEP (0 and 15 cmH2O). GEDV, RVEDV, right heart (RHEDV) and left heart end-diastolic volume (LHEDV) were measured by thermodilution. Blood flow on the descending thoracic aorta measured with an ultrasonic flow-probe served to determine stroke volume (SV). Measurements were performed during baseline conditions, after volume loading with previously extracted haemodilution blood (20 mL kg−1) and following haemorrhage (30 mL kg−1). Results: Application of PEEP decreased GEDV and SV significantly (P < 0.05). Augmenting TV did not reduce GEDV systematically, but significantly reduced SV (P < 0.05). Changes in ventilator settings only influenced RVEDV following volume loading (P < 0.05). RHEDV and LHEDV decreased following application of PEEP, but only RHEDV decreased after augmenting TV at baseline and following volume loading. Correlation of SV with parameters of CBV was r = 0.487 (P < 0.01) for GEDV, r = 0.553 (P < 0.01) for RVEDV, r = 0.596 (P < 0.01) for RHEDV and r = 0.303 (P < 0.01) for LHEDV. Conclusion: Application of PEEP decreases CBV and SV. Augmenting TV reduces SV but not CBV. There is a moderate correlation between parameters of CBV and cardiac performance.

Summary

Background and objectives: Preoperative evaluation performed by anaesthesiologists primarily aims to estimate the risk of perioperative complications and to create opportunities to optimize the patients' condition before surgery. In this study an inventory was made of the current practice of preoperative evaluation in Dutch hospitals. It was estimated how many hospitals had implemented an outpatient preoperative evaluation clinic in 2004. Subsequently, current practice was compared with the results of a previous inventory (2000). It was also evaluated to what extent the guidelines of the Dutch Health Council and the Netherlands Society of Anaesthesiology were followed. Methods: The study consisted of two phases. First, a literature research was performed and pilot interviews were constructed. The interviews were conducted face-to-face with anaesthesiologists in a sample of Dutch hospitals. Based on the results, written questionnaires were constructed. In the second phase these questionnaires were sent to all general and academic hospitals in the Netherlands. Results: In 2004, 74% of the hospitals had an outpatient preoperative evaluation clinic, compared with 50% in 2000. The percentage of hospitals with an outpatient preoperative evaluation clinic available for all elective patients increased from 20% to 52%. Conclusions: The Dutch guidelines on preoperative evaluation seem to have influenced current practice. An increase in the number of outpatient preoperative evaluation clinics was seen after the guidelines were published. The implementation of an outpatient preoperative clinic seems to warrant that anaesthesiologists are carrying out the activities prescribed by the guidelines. Most hospitals without a clinic aim to implement one in the future.

Summary

Background and objective: A randomized double-blind controlled trial was performed to determine if there was a difference in discomfort on injection between two preparations of propofol. A long-chain triglyceride preparation (LCT-propofol (Fresenius)) was compared against a medium- and long-chain triglyceride preparation (MCT/LCT-propofol (BBraun)). Methods: One hundred and twenty ASA I–II patients listed for elective procedures were consented and randomized to receive either induction agent. A standard rate of infusion was used for induction of anaesthesia and subjects were questioned about discomfort until contact was lost. Discomfort was recorded as none, mild, moderate or severe. Incidence of postoperative nausea and vomiting and anti-emetic requirements were recorded in the postanaesthetic care unit. Results: There was seen to be a 54% reduction in moderate/severe discomfort with MCT/LCT-propofol compared with LCT-propofol (P < 0.006). There was a 70% reduction in severe discomfort with MCT/LCT-propofol compared with LCT-propofol (P < 0.04). The term discomfort was used during the study because there is a wide array of unpleasant sensations felt by patients during propofol induction which are not always reported as pain. There was no significant difference in the incidence of postoperative nausea and vomiting or anti-emetic use between the two groups. Conclusions: There is a significant decrease in the incidence of discomfort with MCT/LCT-propofol compared with LCT-propofol. This difference is more marked in subjects reporting severe discomfort.