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 objectives: The primary objective of sedation in the critically ill patient is to achieve security and comfort. The routine use of standardized and validated sedation scales and monitors are needed. The Richmond agitation sedation scale has been used but some patients cannot be evaluated with subjective assessment tools such as the Richmond agitation sedation scale because they lack motor responsiveness due to therapeutic paralysis or because they are receiving deep sedation. We aimed to assess the correlation of bispectral index with Richmond agitation sedation scale during dexmedetomidine sedation and evaluate the use of the bispectral index in monitoring the levels of sedation in intensive care patients. Methods: This was a single centre, prospective, clinical study. Eleven mechanically-ventilated critically ill patients, aged 17–82 (50.09 ± 17.76; mean ± SD) yr, 3 males and 8 females, APACHE II score 12.63 ± 3.90, SOFA score 3.27 ± 1.73 were enrolled in the study. Patients received a dexmedetomidine infusion of 1 μg kg−1 over 10 min followed by a maintenance infusion of 0.5 μg kg−1 h−1 for 8 h. Sedation was assessed using the Richmond agitation sedation scale and bispectral index monitoring. Heart rate, blood pressure, respiratory rate and SPO2 were monitored. Wilcoxon signed rank sum test and Spearman's rank correlation analysis were used for statistical analysis. Results: The variation of Richmond agitation sedation scale score was between 0.9 and −1.7 bispectral index varied from 65 to 75. Significant correlations between Richmond agitation sedation scale and bispectral index values were found in this study. (r = 0.900; P = 0.0001) Conclusions: Richmond agitation sedation scale levels significantly correlated with bispectral index values during dexmedetomidine sedation in critically ill patients requiring mechanical ventilation in the intensive care unit.

Summary

Background and objective: Sedation is commonly used to facilitate diagnostic procedures in children. The aim of our study was to investigate sedation in children using propofol alone or combined with fentanyl or midazolam with regard to efficacy, adverse reactions or side-effects related to the drugs, ease of operation for the endoscopist, and time to discharge from the post-anaesthesia care unit. Methods: We prospectively studied 240 children, aged 1–12 yr of age, undergoing endoscopic procedures of the upper gastrointestinal tract. The patients were given an oral premedication with midazolam (0.5 mg kg−1) and were then randomly allocated to one of the three study groups: propofol alone (Group P), propofol with fentanyl 1 μg kg−1 (Group PF) or propofol with midazolam 0.1 mg kg−1 (Group PM). Additional doses of propofol given during the procedure were recorded. Adequacy of sedation and ease of procedure (easy, adequate, impossible) were evaluated by the endoscopist, who was blinded as to the drugs used. Results: The duration of the procedure and the recovery period were similar in the three groups. The number of patients requiring supplemental doses of propofol to permit safe completion of gastroscopy was 31 in Group P (=39%; eight of these required two additional doses), 14 in Group PM (=18%), and 11 in Group PF (=13%) (P < 0.05). There was a lower incidence of adverse events in Group PM and in Group PF than in Group P (P < 0.05). Conclusions: Propofol in combination with fentanyl or midazolam gives better sedation and ease of endoscopy than propofol alone.

Background and objective: Cardiovascular and mental stress in dental patients with phobias about dentistry may be reduced by propofol sedation. We tested the hypothesis that even low doses of propofol may have effects on body temperatures in male volunteers.

Methods: Six healthy male volunteers were given propofol over 28 min with the following infusion rates: 8 mg kg−1 h−1 for the first 3 min, 4 mg kg−1 h−1 for the next 10 min, and 2 mg kg−1 h−1 for the final 15 min. Body temperatures were measured at five locations: tympanic membrane, forehead, forearm, dorsum of the hand and fingertip. Thermoregulatory vasoconstriction was evaluated using the forearm minus fingertip temperature gradient.

Results: Tympanic membrane and forehead temperatures began to decrease at 10 and 20 min, respectively, after the start of the propofol infusion, and reached a minimum at 30 min (tympanic −0.5 ± 0.2°C) and 40 min (forehead −0.6 ± 0.2°C), respectively. Peripheral skin temperatures showed an increase between 10 and 30 min in the forearm and fingertip and between 20 and 30 min in the dorsum of the hand. After 30 min, a decrease in peripheral skin temperatures was observed. The forearm minus fingertip temperature gradient changed from negative to positive after 40 min, and increased continuously thereafter (baseline −0.3 ± 0.4°C, 90 min: 6.5 ± 1.6°C).

Conclusions: A low dose of propofol impairs tonic thermoregulatory vasoconstriction and induces heat redistribution from the core to the periphery.

Background and objective The use of tension-free tape in the vagina is a relatively new surgical procedure for the treatment of urinary incontinence. Traditionally, the procedure is carried out using local anaesthesia and sedation. We aimed to assess the quality of anaesthesia obtained during insertion of tension-free vaginal tape using local anaesthetic infiltration and intravenous conscious sedation.

Methods Twenty-four patients were studied using intravenous midazolam, fentanyl and infiltration with 0.5% prilocaine and epinephrine. Visual analogue scores before operation were used to assess anxiety. The digit symbol substitution test was used before and after surgery to assess psychomotor recovery, and amnesia for the procedure was assessed by means of picture recall. A nurse, anaesthetist and surgeon independently assessed quality of anaesthesia based on vocalization, facial expression, movement and co-operation with incontinence testing.

Results The nurse, anaesthetist and surgeon reported good or excellent conditions in 18, 14 and 22 cases, respectively. There was no significant psychomotor impairment using the digit symbol substitution test, with mean (standard deviation) preoperative and postoperative scores of 22 (8) and 21 (7) correctly matched symbol digit pairs. There was a significant correlation between preoperative anxiety and intraoperative fentanyl requirement (r=0.48, P < 0.05).

Conclusion Satisfactory anaesthetic conditions can be achieved for the insertion of tension-free vaginal tape using local anaesthesia with sedation.

Background and objective Variability in blink duration was examined to see whether it was sensitive to sevoflurane sedation at 0.05 and 0.1 minimum alveolar concentration (MAC).

Methods Blinks were measured with an infrared transducer in eight subjects. Sedation was scored using a visual analogue scale (VAS).

Results At baseline, 0.05 and 0.1 MAC sevoflurane, respectively, the overall median value of blink duration and its interquartile range were 95 (80–110) ms, 198 (163–245) ms and 210 (130–980) ms. The median percentage of blinks exceeding 500 ms was 0% (0–0.7%), 33.3% (25.5–34.7%) and 25% (15.7–63.3%) respectively. Values during 0.05 and 0.1 MAC sevoflurane were significantly different from baseline (P < 0.035) but not from each other. Baseline visual analogue scales showed large intersubject variability. Compared with baseline, VAS scores were higher at 0.05 MAC (P < 0.035) but not at 0.1 MAC. After discontinuing sevoflurane, median blink duration returned to baseline with a recovery half-life of 2.6 min (R2 = 0.95).

Conclusion Blink duration is a sensitive measure of sevoflurane sedation even at 0.05 MAC.

Local anaesthesia combined with conscious sedation is becoming a popular technique for implantation of cardioverter-defibrillator devices. Propofol was given to provide loss of consciousness during defibrillation shock administration, for induced ventricular fibrillation testing. Propofol was found to decrease QT interval and QT dispersion in two patients with idiopathic prolonged QT interval and QT dispersion. The findings of the procedure are reported.

We performed a prospective, randomized study comparing the efficacy and safety of remifentanil, propofol or both for conscious sedation during eye surgery under retrobulbar blockade. Forty-five unpremedicated patients were assigned to receive remifentanil (group R) (n=15, mean dosage: 0.05±0.03 μg kg−1 min−1), propofol (group P) (n=15, 1.5±0.5 mg kg−1 h−1) or a combination (group RP) (n=15, R: 0.03±0.01 μg kg−1 min−1; P: 0.7±0.2 mg kg−1 h−1). Haemodynamic responses were comparable among all groups. Minimum values for respiratory rate were lower in R patients (R: 7 vs. P and RP: 10 breaths min−1). Peri-operative blood gas analysis showed differences in maximum carbon dioxide tensions (R: 51.5 vs. P: 48.3 vs. RP: 45.5 mmHg) and decrease in minimum pH values (R: −0.06 vs. P: −0.0 vs. RP: −0.01). All group P patients reported mild to intense pain during retrobulbar block, while 53% of the group R patients were free from pain. In group RP, 60% of patients experienced no pain and the remaining 40% reported mild pain only. Remifentanil, applied as the sole agent, provided superior pain relief and patient comfort when compared with propofol, but produced greater respiratory depression and postoperative nausea. The combination of remifentanil and propofol provided haemodynamic stability, adequate spontaneous respiration and pain relief, with a low risk of untoward side effects.

Hypoventilation as a consequence of deep intravenous sedation is the most frequently reported cause of cardiac arrest during upper gastrointestinal endoscopy (UGIE). Haemodynamic stress can contribute to myocardial ischaemia; therefore, this study was designed to observe prospectively the cardio-respiratory changes during UGIE using either midazolam or propofol for conscious sedation. Thirty-four patients, aged 50 years and older, ASA physical status I–III, scheduled for elective UGIE with sedation, were studied. Oxygen saturation, heart rate, non-invasive blood pressure and Holter ECG were recorded continuously starting 15 min before sedation until 15 min after the endoscopy. In addition, plasma catecholamine concentrations were determined. The results of this study are consistent with previous reports that cardiopulmonary events may occur during endoscopy, with or without sedation. Both midazolam and propofol sedation may provide some protection against haemodynamic stress in response to insertion and manipulation of the endoscope, but sedation can also contribute to the occurrence of hypoxaemia.

Septal surgery (submucous resection and septoplasty) has been performed as a day-case procedure routinely under general anaesthesia and local anaesthesia with sedation at the Ipswich Hospitalsince 1992. The outcome of the day-case septal surgery over a period of 18 months has been audited. A total of 95 cases were operated on of which 48 were under general anaesthesia (GA) and 47 under local anaesthesia (LA) with sedation using midazolam intravenously. The bleeding rate and overnight admission rate were 10.5 and 11.4 percent respectively. The bleeding rate was the same in both GA and LA groups. The combination of local anaesthesia and sedation has been foundto be safe, effective and acceptable to patients. It is concluded that septal surgery is suitable as a day procedure and that local anaesthesia combined with sedation has a definite place ifcarried out properly.