Summary

Risk-adjusted outcome prediction is mainly important in two separate fields. The first is quality monitoring: measuring actual versus predicted mortality in an institution allows assessment of the clinical surgical and anaesthesia performance while adjusting for the risk profile of the patients. Without risk stratification, surgeons and hospitals treating high-risk patients will appear to have worse results than others. This may prejudice referral patterns, affect the allocation of resources and even discourage the treatment of high-risk patients. The second field is that of informed consent and clinical decision-making. Risk-adjusted predicted mortality should form an important part of patient and surgeon decisions on whether or not to proceed with surgery. Clearly, no ‘perfect’ model can be produced as some aspects of mortality will always be related to risk factors not included in the model (e.g. the quality of the distal coronary artery vessels in coronary artery surgery) or due to chance happenings not related to preoperative patient characteristics (such as surgical error). An individual patient will either survive or die after cardiac surgery. Clearly, no scoring system will predict the specific outcome for every patient. However, risk stratification will inform patients and clinicians of the likely risk of death for a group of patients with a similar risk profile undergoing the proposed operation. This information is useful and should form part of the basis on which the patient and surgeon decide whether to proceed.

Summary

Background and objective: The in vitro contracture test with halothane and caffeine is the gold standard for the diagnosis of susceptibility to malignant hyperthermia (MH). However, the sensitivity of the in vitro contracture test is between 97 and 99% and its specificity is 78–94% with the consequence that false-negative as well as false-positive test results are possible. 4-Chloro-m-cresol is potentially a more specific test drug for the in vitro contracture test than halothane or caffeine. This multicentre study was designed to investigate whether an in vitro contracture test with bolus administration of 4-chloro-m-cresol can improve the accuracy of the diagnosis of susceptibility to MH.

Methods: Three hundred and fifty-two patients from 11 European MH laboratories participated in the study. The patients were first classified as MH susceptible, MH normal or MH equivocal by the in vitro contracture test according to the European MH protocol. Muscle specimens surplus to diagnostic requirements were used in this study (MH susceptible = 103 viable samples; MH equivocal = 51; MH normal = 204). 4-Chloro-m-cresol was added to achieve a concentration of 75 μmol L−1 in the tissue bath. The in vitro effects on contracture development and muscle twitch were observed for 60 min.

Results: After bolus administration of 4-chloro-m-cresol, 75 μmol L−1, 99 of 103 MH-susceptible specimens developed marked muscle contractures. In contrast, only two of 204 MH-normal specimens showed an insignificant contracture development following 4-chloro-m-cresol. From these results, a sensitivity rate of 96.1% and a specificity rate of 99.0% can be calculated for the in vitro contracture test with bolus administration of 4-chloro-m-cresol 75 μmol L−1. Forty-three patients were diagnosed as MH equivocal, but only specimens from 16 patients developed contractures in response to 4-chloro-m-cresol, indicating susceptibility to MH.

Conclusions: The in vitro contracture test with halothane and caffeine is well standardized in the European and North American test protocols. However, this conventional test method is associated with the risk of false test results. Therefore, an improvement in the diagnosis of MH is needed. Regarding the results from this multicentre study, the use of 4-chloro-m-cresol could increase the reliability of in vitro contracture testing.

Summary

Background and objective: Morbidity from subarachnoid haemorrhage is common and results from complications including myocardial dysfunction and neurogenic pulmonary oedema causing hypotension and hypoxia – both major causes of secondary brain injury. Predicting patients at risk of developing these complications may facilitate early intervention.

Methods: Using QTc dispersion to assess repolarization inhomogeneity, patients who had suffered severe acute subarachnoid haemorrhage were studied in an intensive care unit. Electrocardiograms were recorded within 24 h of ictus. Subsequent development of myocardial dysfunction was defined as a requirement for inotropes, and neurogenic pulmonary oedema as a PaO2 (kPa)/FiO2 ratio <40. Together they constituted cardiorespiratory compromise.

Results: Twenty-seven patients were recruited. QTc dispersion was greater in patients (74.1 ms, SD ± 26.1) than in controls (48.3 ms, 12.0) P < 0.0001, 95% CI 14.6, 37.0. Thirteen patients developed cardiorespiratory compromise and had greater QTc dispersion (84.5 ms, 26.2) than patients who did not develop cardiorespiratory compromise (64.5 ms, 22.7) P = 0.046, 95% CI 0.3, 39.6. There was no difference in QTc dispersion between patients who did and those who did not develop myocardial dysfunction alone. Similarly, there was no difference in QTc dispersion between patients who did and those who did not develop neurogenic pulmonary oedema alone.

Conclusions: Increased QTc dispersion is associated with the later development of cardiorespiratory compromise in poor-grade subarachnoid haemorrhage patients. QTc dispersion may be used as a marker to predict impending clinical deterioration, providing an opportunity for early intervention.

Summary

Background and objective: Isoflurane is commonly used for neurosurgery but the effects of sevoflurane on human cerebral blood flow and cerebral metabolic rate of oxygen have not been fully evaluated. We therefore assessed the effects of sevoflurane and isoflurane on global cerebral blood flow and cerebral metabolic rate of oxygen in patients without noxious stimuli or neurological disorders.

Methods: General anaesthesia was induced with midazolam (0.2 mg kg−1) and fentanyl (5 μg kg−1) in 20 ASA I patients undergoing knee joint endoscopic surgery. Epidural anaesthesia was also performed to avoid noxious stimuli during surgery. Cerebral blood flow and cerebral arteriovenous oxygen content difference was measured using the Kety–Schmidt method with 15% nitrous oxide as a tracer before and after administration of either sevoflurane or isoflurane (1.5 minimum alveolar concentration, 60 min) and cerebral metabolic rate of oxygen was then calculated.

Results: Sevoflurane and isoflurane both increased cerebral blood flow (17%, P < 0.05; 25%, P < 0.05, respectively) and decreased cerebral metabolic rate of oxygen (26%, P < 0.01; 38%, P < 0.01, respectively). There were no significant differences in cerebral blood flow and cerebral metabolic rate of oxygen between sevoflurane and isoflurane.

Conclusions: Sevoflurane and isoflurane similarly increased cerebral blood flow and decreased cerebral metabolic rate of oxygen in human beings anaesthetized with midazolam and fentanyl.

Summary

Background and objective: This study was designed to assess the conditions for endotracheal intubation or insertion of a laryngeal mask airway following an inhalational induction using 8% sevoflurane and nitrous oxide without the use of muscle relaxants or opioids.

Methods: There were two groups: 30 children had endotracheal intubation and 30 children had a laryngeal mask airway inserted. Induction of anaesthesia was accomplished using an inspiratory concentration of sevoflurane 8% in a nitrous oxide and oxygen mixture. After an end-expiratory concentration of sevoflurane of at least 4% had been reached, when the pupils were miotic and centred, the trachea was intubated or a laryngeal mask inserted. The time to loss of consciousness and successful airway management was recorded. Jaw relaxation, movements, visibility, and position of the vocal cords and vital parameters were monitored.

Results: Jaw relaxation was complete in all children. The vocal cords were completely visible in all patients of the tracheal intubation group, whereas vocal cord relaxation was incomplete in five children. Nevertheless, all children had an atraumatic intubation or insertion of the laryngeal mask without the use of a muscle relaxant. Vital signs were stable in both groups. There were no cases of restlessness and/or postoperative shivering. Four patients in the endotracheal group (13.3%) were nauseous and three (10%) vomited, while two children (6.6%) in the laryngeal mask group experienced nausea and vomiting.

Conclusions: Induction with sevoflurane in nitrous oxide and oxygen leads to fast loss of consciousness and provides ideal conditions for managing the airway without supplemental opioids or muscle relaxants. Furthermore, sevoflurane using this technique was very well tolerated, indicated by high haemodynamic stability and a reduced rate of postoperative restlessness, shivering, nausea and vomiting.

Summary

Background and objective: There are little data on nitrous oxide (N2O) concentrations in neonatal blood at delivery. We investigated the effects of the time elapsing between the induction of anaesthesia and delivery (the I–D interval) on umbilical blood N2O concentrations.

Methods: Maternal and neonatal blood N2O concentrations were measured in 27 patients undergoing Caesarean section under N2O 67% anaesthesia. The duration of N2O administration (range 2–50 min) was arbitrarily divided into three groups (each n = 9): short (2–9 min), medium (9.1–14 min) and long duration (14.1–50 min).

Results: Compared with a rapid increase in the maternal arterial N2O concentration (48.9 ± 4.7%), the umbilical venous N2O concentration (17.9 ± 8.3%) rose slowly in the short duration group, whereas the N2O concentrations became more similar (61.6 ± 4.3 and 43.2 ± 10.0%, respectively) in the long duration group. The ratio of umbilical vein to maternal artery N2O concentrations correlated with the duration of N2O anaesthesia (r = 0.739), resulting in ratios of 0.37 ± 0.18, 0.61 ± 012 and 0.70 ± 0.13 for the short, medium and long duration groups, respectively. The Apgar score at 1 min correlated inversely with the duration of anaesthesia and with the umbilical vein N2O concentration (r = −0.457 and −0.423, respectively).

Conclusions: The data suggest that placental N2O transfer during Caesarean section is time-dependent and slower compared with maternal N2O uptake. They also suggest that the Apgar score is less affected by N2O administration when the I–D interval is shorter.

Summary

Background and objective: Transurethral prostatectomy is routinely performed under spinal anaesthesia. This technique can cause hypotension, which is particularly undesirable in the elderly. The objective was to compare spinal anaesthesia for transurethral prostatectomy using hyperbaric bupivacaine 15 mg (control group) and hyperbaric bupivacaine 10 mg (limiting spread by maintaining the upright position for 15 min) and fentanyl 25 μg (fentanyl group) in terms of haemodynamic and pulmonary function.

Methods: Thirty ASA I–III patients were randomly selected and underwent spinal anaesthesia with either hyperbaric bupivacaine 15 mg (immediately positioned supine) or hyperbaric bupivacaine 10 mg (upright for 15 min) and fentanyl 25 μg.

Results: The greatest changes in mean arterial pressure (P = 0.9), ephedrine requirements (P = 0.8) and mean maximum change in forced vital capacity (P = 0.5) were similar in both groups.

Conclusions: The addition of fentanyl 25 μg to bupivacaine 10 mg and limiting the spread of the block does not improve either haemodynamic or pulmonary function compared with bupivacaine 15 mg in patients undergoing transurethral prostatectomy.

Summary

Background and objective: In a retrospective study, we examined the suitability of a departmental clinical protocol for anaesthesia induction with target-controlled infusion of propofol developed for fibreoptic intubation in spontaneously breathing patients scheduled for outpatient oral surgery at the dental clinic of the Vienna University Hospital.

Methods: Propofol was administered using target-controlled infusion (Diprifusor®) at increasing target plasma concentrations starting at 2.5 μg mL−1. After 10 min, an intravenous dose of alfentanil (5–10 μg kg−1) was given for pain reduction. After a further 2 min, the patient was evaluated for response to auditory stimulation. If unresponsive, fibreoptic intubation was performed, otherwise the target concentration was increased by 0.2 μg mL−1 every 2 min until non-responsiveness was attained.

Results: Tracheal intubation was successful in all patients without any haemodynamic instability. However, one patient required facemask ventilation for 2 min. No patient was aware of intubation. The plasma concentration required for non-responsiveness was 2.8 ± 0.4 μg mL−1 (mean ± SD).

Conclusions: When using a target-controlled infusion of propofol, fibreoptic intubation can be performed with complete amnesia of the procedure for the patient. However, assisted ventilation of the lungs may be necessary as spontaneous ventilation may cease.

Summary

Background and objective: The size of the laryngeal mask airway in children is determined by the patient's weight. However, in some instances an alternative method may be wanted. The aim was to search for a new method that would be easy to perform at the bedside.

Methods: The size of the laryngeal mask airway was determined in 183 children by choosing the laryngeal mask that best matched the combined widths of the patient's index, middle and ring fingers. The results were compared with the standard method recommended by the manufacturer's weight-related guidelines. The patients were classified in different groups depending on the laryngeal mask airway sizes determined by both methods. A kappa coefficient evaluated the agreement between both techniques.

Results: The kappa coefficient was 0.81, showing an ‘excellent agreement’ between both methods. The size was the same for both methods in 142 children (78%). The disagreement between both techniques was only of one size in the remaining 41 patients (22%). In such patients, the weight was a borderline value that would indicate a change in the size of the laryngeal mask airway using the classic method.

Conclusions: This new approach is of valid and practical use in children, particularly as an alternative in those situations where the patient's weight is unknown, such as in emergency situations or in those borderline instances where an alternative measurement would be useful.