Summary

The management of thyroid-associated eye disease is reviewed with particular reference to surgical management and its implications for anaesthetists. Experience from a unit undertaking such surgery is presented.

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Background and objective: The aromatic alcohol most closely resembling the aromatic tail of lidocaine is 2,6-dimethylphenol. This agent is as potent as lidocaine in blocking voltage-operated sodium channels. The aim of this study was to show the effect of halogenation in the para-position on the potency of this compound to block voltage-operated sodium channels. Methods: Insertion of the halogen chloride into the para-position of the molecule 2,6-dimethylphenol yielded 2,6-dimethyl-4-chlorophenol. Block of sodium currents by this compound was studied using heterologously expressed voltage-operated rat neuronal (rat IIa) sodium channels. Results: 2,6-dimethyl-4-chlorophenol reversibly suppressed depolarization-induced whole-cell sodium inward currents. The ECR50 for block of resting channels at a hyperpolarized holding potential (−150 mV) was 127 μmol, the Hill coefficient nH 1.7. Membrane depolarization inducing either fast or slow-inactivation strongly increased the blocking potency. This is an important feature of a local-anaesthetic-like action. The estimated half-maximum effect concentration for the fast-inactivated channel state ECI50 was 28 μmol, the Hill coefficient nH 3.8. When 20–30% of channels were slow-inactivated using long (2.5 s) prepulses, followed by a 10 ms repolarization period to allow recovery from fast inactivation, the IC50 at −100 mV holding potential was reduced to 53 μmol. Conclusion: These results, which show that 2,6-dimethyl-4-chlorophenol blocks voltage-operated sodium channels in a lidocaine-like manner while having a several fold higher potency than the non-halogenated parent compound, highlight a potentially meaningful principle of increasing the sodium channel blocking potency of phenol derivatives.

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Background and objective: The glutamate-nitric oxide-cyclic guanosine monophosphate pathway has been identified as a potential target for anaesthetic agents. However, mice deficient in neuronal nitric oxide synthase have a similar susceptibility to volatile anaesthetic agents to wild-type mice and are not affected by non-isoform selective inhibitors. We hypothesized that the neuronal nitric oxide synthase selective inhibitor, 7-nitroindazole, would also reduce the propofol requirements in wild-type mice but would have no effect in neuronal nitric oxide synthase knockout mice. Methods: We determined the time to loss of righting reflex, time to painful stimulus and time to regaining the righting reflex in neuronal nitric oxide synthase knockout and wild-type mice following the intraperitoneal injection of propofol in untreated, 7-nitroindazole and vehicle only treated animals (n = 6 per group). Propofol (200 mg kg−1) resulted in loss of righting reflex in the untreated and vehicle only groups but was lethal in 7-nitroindazole pre-treated mice, requiring a reduced dose of propofol (100 mg kg−1). Results: 7-nitroindazole pre-treatment significantly reduced the loss of righting reflex (P < 0.001) in both wild-type and knockout mice when compared to untreated and vehicle only pre-treated animals, but had no effect on time to painful stimulus or regaining of the righting reflex. 7-nitroindazole reduced the propofol requirements in knockout mice to the same extent as in wild-type animals. Conclusions: Propofol exerts its anaesthetic effects at least partially via the glutamate-nitric oxide-cyclic guanosine monophosphate pathway. The neuronal nitric oxide synthase knockout mice are sensitive to neuronal nitric oxide synthase selective inhibition suggesting that compensatory pathways in neuronal nitric oxide synthase knockout mice exist.

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Background: The suggested induction dose of methohexital for electroconvulsive therapy (ECT) varies widely influencing efficacy of ECT and safety of anaesthesia. Bispectral index (BIS), a monitor of consciousness, may be useful to assure adequate hypnosis with optimized methohexital dose. Methods: Patients with medically resistant major depression (ICD10), scheduled for multiple ECT's, were studied. Depth of anaesthesia was BIS controlled. ECT was not performed until BIS dropped below 50. Initially anaesthesia was induced with methohexital 1.0 mg kg−1, and stepwise reduced by 0.1 mg kg−1 during consecutive treatments. If BIS did not drop below 50, the methohexital was supplemented by further boluses of 0.5 mg kg−1, until the desired level of hypnosis was reached. The adequacy of the anaesthetic recommendation for methohexital (1.0–1.5 mg kg−1) as well as the psychiatric recommendation (0.75–1 mg kg−1) was investigated. Results: One-hundred and nine ECT's in 14 patients were studied. The recommended anaesthetic dose (1.0–1.5 mg kg−1) was inadequate in 40% of the treatments, with 12% exceeding 1.5 mg kg−1, and 28% below 1.0 mg kg−1. Psychiatric recommendation (0.75–1.0 mg kg−1) was inadequate in 49%, with 39% exceeding 1.0 mg kg−1 and 10% undershooting at 0.75 mg kg−1. Conclusions: Methohexital for ECT showed a great variability, exceeding as well as undershooting the dosage recommendations widely. BIS monitoring may be useful to secure adequate hypnosis during muscle relaxation and treatment and may optimize ECT efficacy.

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Background and objective: The cerebral state index (CSI™) derived from a new small handheld electroencephalogram monitor was studied during routine day surgical anaesthesia titrated according to the bispectral index (BIS™). The objective was to determine the degree of agreement between the two monitors. Methods: Anaesthesia was induced with propofol and fentanyl (0.1 mg) in 38 patients undergoing general anaesthesia for routine day-surgery. Maintenance anaesthesia (sevoflurane (20/38), desflurane (10/38) or propofol (8/38)) titrated by BIS XP (Aspect Medical, Natwick, MA, USA) and BIS and CSI (cerebral State Monitor, Danmeter; Odense, Denmark) index values were recorded every minute. No patient received muscle relaxation. Observer's Assessment of Alertness/Sedation rating scale was used to assess level of sedation. Results: Pair-wise recordings (914) of CSI and BIS were collected. The indices showed similar pattern and decreased with increasing level of sedation, however with large ranges for each level of sedation. Median indices were similar during surgery (BIS: 50 (14–89); CSI: 51 (7–88)) and both indices increased (P < 0.01) when minor movements occurred (BIS 65 (40–83); CSI 67 (40–89)). During maintenance of anaesthesia CSI > 20% from BIS-index in 24% of readings, and on rare occasions CSI indices deviated >100% from the BIS reading. When BIS < 40, CSI decreased slower than BIS and with wider spreading. Conclusions: When used for day-surgery anaesthesia without muscle relaxation, CSI and BIS show similar patterns and numerical values but with the incidence of occasionally large discrepancies between pair-wise readings. Which monitor is the more dependable remains to be established and cannot be implied from this initial explorative study.

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Background and objectives: This study was designed to investigate whether single epidural droperidol or continuous epidural droperidol inhibit pruritus and postoperative nausea and vomiting induced by postoperative continuous epidural fentanyl administration, and to identify the optimal method of administering epidural droperidol. Methods: 120 ASA I–II patients undergoing subtotal gastrectomy with general anaesthesia combined with epidural anaesthesia were randomly allocated into three groups: control (no droperidol), single injection (droperidol 2.5 mg) and continuous group (droperidol 2.5 mg 2 day−1). Postoperatively the frequency and severity of pruritus and postoperative nausea and vomiting in all groups were compared during 48 h. Results: The frequency and severity of pruritus was significantly lower in both single injection and continuous groups than control group after epidural fentanyl administration (P < 0.05). The frequency and severity of postoperative nausea and vomiting was significantly lower in single injection group than control group after epidural fentanyl administration (P < 0.05). Conclusion: Epidural continuous droperidol is effective for reducing pruritus, and single epidural droperidol injection is effective for reducing pruritus and postoperative nausea and vomiting induced by postoperative continuous epidural fentanyl analgesia.

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Background and objective: Data on the effectiveness of cyclooxygenase 2 inhibitors in postoperative pain therapy vary widely. We tested in a prospective, placebo-controlled, randomized, double-blind trial the hypotheses that perioperative (i.e. preoperative and postoperative) administration of the cyclooxygenase 2 inhibitor rofecoxib decreases pain scores and morphine consumption after spine, breast and orthopaedic surgery. Methods: Five hundred and forty patients scheduled for spine, breast or orthopaedic surgery were randomly assigned to receive in combination with postoperative morphine via patient controlled analgesia pump for 4 days either rofecoxib 50 mg administered perioperatively, rofecoxib 50 mg administered only postoperatively, or placebo. Primary outcome criteria were pain score at rest (numeric rating scale 0–4) and morphine consumption. Results: Perioperative rofecoxib significantly decreased pain score 0 (0–1) vs. 1 (0–2) (median (interquartile range)), and morphine consumption 18 (6–33) vs. 22.5 (12–38) compared with placebo. In contrast, rofecoxib when administered only postoperatively did not significantly improve analgesic effects or side-effects at time of assessment of the main criteria (24 h after skin closure), but during the follow-up period at 48 h and 72 h after skin closure pain scores and morphine consumption were improved compared to placebo. The analgesic effects of rofecoxib were independent from the type of surgery. Conclusions: Perioperative administration of the cyclooxygenase 2 inhibitor rofecoxib decreases pain scores and morphine consumption after orthopaedic, breast and spine surgery. However, the benefit of preoperative administration of the cyclooxygenase 2 inhibitor seems to be only moderate, suggesting that early postoperative administration may be a useful alternative approach. There is no evidence that the type of surgery influences analgesic effects of cyclooxygenase 2 inhibitors.

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Background and objective: Preoperative anxiety is a challenging concept in the preoperative care of patients. The hypothesis of this study was that the doctors are able to estimate their patients' preoperative anxiety. Methods: A prospective clinical trial was performed on 67 adult patients and 26 paired anaesthetists and surgeons. The patients filled out two separate visual analogue scales for anxiety for the planned anaesthesia and surgery. After that the ‘anxiety subscale’ of the Hospital Anxiety and Depression's Scale was completed and a list of fearsome items was presented as the patients were asked to choose two conditions they considered the most frightening. Finally the patients were asked to select one or more items from a list of things, which they considered likely to relieve their preoperative anxiety. Similarly, the participating doctors were asked to estimate their patients' anxiety, guess their fearful conditions and their anxiety-relieving requests. Results: Median scores for anxiety as estimated with visual analogue scales by anaesthetists, surgeons and patients for anaesthesia were 34, 36 and 6, respectively; and for surgery 53, 47 and 9, respectively. The anxiety subscale of the Hospital Anxiety and Depression's Scale 8.9 ± 4.2, 8.6 ± 4.6 and 6.5 ± 4.5 (mean ± SD), respectively. Doctors' scores were significantly higher than the patients' scores (P < 0.05). Thus, the anaesthetists and the surgeons were unable to estimate their patients anxiety on any of the scales used (Kendall's τ < 0.25; P < 0.05). The proportion of correct estimation of the fearsome items was 20% for both the anaesthetists and the surgeons. Conclusions: Both anaesthetists and surgeons overestimated their patients' preoperative anxiety by a wide margin and poorly predicted their patients' feared conditions and their desire for relief of anxiety.

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Background and objective: We compared the laryngeal mask airway (LMA™) and the laryngeal tube (LT®) with the newly introduced perilaryngeal airway (CobraPLA®, PLA) with regard to haemodynamic responses induced by airway insertion, clinical performance and occurrence of postoperative sore throat after short surgical procedures. Methods: After premedication, 90 ASA I–II patients awaiting short surgical procedures were randomized to receive, LMA, LT or PLA. Anaesthesia was induced with intravenous propofol (2.5 mg kg−1) and mivacurium (0.2 mg kg−1). Number of attempts, time of insertion of the device, any other unwanted effect, mean aterial pressure, heart rate, oxygen saturation and end-tidal carbon dioxide were recorded. At the end of surgery, the cuff of the device was immediately deflated and the airway device was removed. The device was examined and noted for the presence of visible blood. Patients were asked to rate their throat soreness, dysphonia and dysphagia 1 and 24 h postoperatively. Results: There were no differences in haemodynamic variables. Insertion times for the devices were similar (LMA: 20 ± 11 s, LT: 19 ± 14 s and PLA: 21 ± 12 s.) The success rates at first insertion were lower in the (LMA group (57%) when compared with the PLA (97%, P < 0.05). The number and type of airway interventions for achieving an effective airway were similar. When the airways were removed 50% of the PLA devices had positive blood traces, while only 17% of the LMA and LT devices had positive blood traces (P < 0.01). Fifty percent of the patients suffered from a sore throat in the PLA group, which was significantly higher than in the LMA and LT groups (P < 0.05). Conclusion: We conclude that haemodynamic, ventilation and oxygenation variables throughout the surgery were similar with, LMA, LT and PLA, but LT and PLA were easier to insert; LMA and LT caused less mucosal trauma.

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Background and objectives: The On-Line Electronic Help (OLEH) is a point-of-care information system for anaesthesia providers prepared by the European Society of Anaesthesiologists. In this preliminary study the effect of the OLEH availability on the incidence of knowledge-based errors during the management of case scenarios and participants' subjective evaluation of the OLEH were evaluated. Methods: After a short training session, 48 anaesthesiologists (24 junior residents, 12 senior residents and 12 board-certified) were presented randomly with six computer screen-based case scenarios with, and six without, the option of using the OLEH. Two reviewers evaluated the answers independently according to preconfigured guidelines. Results: The availability of the OLEH was associated with higher scores in 11 of the 12 scenarios, and with a decrease in the incidence of critical errors in 10 scenarios. Time to task completion was increased in one scenario only when the OLEH was used. The degree of professional experience was associated with better scores in five of the scenarios and with a reduced occurrence of critical errors in three scenarios. Forty-two out of 48 participants stated that finding information in the OLEH software was easy and that the system was helpful in managing the scenarios. Conclusions: This preliminary study demonstrates the potential value of the OLEH in decreasing the number of knowledge-based errors made by anaesthesiologists. According to the encouraging results, the OLEH system is currently under evaluation using full-scale simulation scenarios in an operating room environment.

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Background and objective: The level of performance in junior and senior anaesthetists was investigated after 24-h shift working and on-call duties. Methods: Pre- and post-duty psychomotor function, influence on response time, cognitive function and well-being in 23 individuals (13 junior and 12 senior anaesthetists) was assessed before and after 24-h in-house on-call duty. Subjective perception of tiredness and concentration abilities was estimated by applying a visual analogue scale. Results: The self-assessed tiredness prior to duty was high in both age groups and significantly increased in senior anaesthetists after night duty (P = 0.01). Post-duty impairment of concentration abilities was reported in both groups. Comparing results from pre- and post-duty psychometric testing showed a comparable decline in junior and senior anaesthetists as well. Assessment of burnout showed a significant lack of personal accomplishment in junior anaesthetists as compared to their older colleagues (P = 0.038). Senior anaesthetists judged their contribution to patient well-being significantly higher than did their younger colleagues (P = 0.035). Conclusions: Although tiredness and subjective impairment of concentration abilities was high in senior anaesthetists after 24-h in-house on-call duty, performance assessed by psychometric testing does not support the hypothesis that senior colleague's performance cannot keep up with routine hospital shift work.

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Background and objectives: Supplemental oxygen is commonly given via nasal cannulae in spontaneously breathing patients. Our modified nasal cannula with a clamp between the nasal prongs can provide O2 via one nostril and CO2 can be sampled through the other one. We have studied whether this cannula can provide oxygenation similar to a standard cannula without affecting end-tidal CO2 monitoring. Methods: Eighty-six patients were studied during spinal anaesthesia and sedation. In 15 patients, arterial blood was sampled while O2 was delivered at flow rates of 0, 2 and 4L min−1, with or without clamping between the prongs of our modified nasal cannula. In the remaining 71 patients, arterial O2 was measured while using our modified nasal cannula with the clamp applied. End-tidal CO2 was recorded on a capnograph and the correlation between end-tidal and arterial values with our modified nasal cannula was investigated. Results: No end-tidal CO2 waveforms were found with oxygen flow greater than 2L min−1 without clamping between the prongs. With clamping there was a significant correlation (r = 0.83) between arterial and end-tidal CO2. A Bland–Altman analysis revealed a bias of 0.49 kPa with precision of ±0.76 kPa. Arterial oxygenation was not affected by our modified nasal prongs with clamp as compared to the standard cannula. Conclusion: Our modified nasal cannula can provide continuous monitoring of end-tidal CO2 without affecting oxygen delivery in sedated, spontaneously breathing patients.