What Is the Driving Performance of Ambulatory Surgical Patients after General Anesthesia?
Chung, Frances F.R.C.P.C.; Kayumov, Leonid Ph.D.; Sinclair, David R. M.D.; Edward, Reginald F.F.A.R.C.S.I.; Moller, Henry J. M.D., F.R.C.A.; Shapiro, Colin M. M.D.
Anesthesiology. 103(5):951-956, November 2005

Background: Ambulatory surgical patients are advised to refrain from driving for 24 h postoperatively. However, currently there is no strong evidence to show that driving skills and alertness have resumed in patients by 24 h after general anesthesia. The purpose of this study was to determine whether impaired driver alertness had been restored to normal by 2 and 24 h after general anesthesia in patients who underwent ambulatory surgery.
Methods: Twenty patients who underwent left knee arthroscopic surgery were studied. Their driving simulation performance, electroencephalographically verified parameters of sleepiness, subjective assessment of sleepiness, fatigue, alertness, and pain were measured preoperatively and 2 and 24 h postoperatively. The same measurements were performed in a matched control group of 20 healthy individuals.
Results: Preoperatively, patients had significantly higher attention lapses and lower alertness levels versus normal controls. Significantly impaired driving skills and alertness, including longer reaction time, higher occurrence of attention lapses, and microsleep intrusions, were found 2 h postoperatively versus preoperatively. No significantly differences were found in any driving performance parameters or electroencephalographically verified parameters 24 h postoperatively versus preoperatively.
Conclusions: Patients showed lower alertness levels and impaired driving skills preoperatively and 2 h postoperatively. Based on driving simulation performance and subjective assessments, patients are safe to drive 24 h after general anesthesia.

Continuous Peripheral Nerve Blocks in Hospital Wards after Orthopedic Surgery: A Multicenter Prospective Analysis of the Quality of Postoperative Analgesia and Complications in 1,416 Patients.
Capdevila, Xavier M.D., Ph.D.; Pirat, Philippe M.D.; Bringuier, Sophie Pharm.D. ; Gaertner, Elisabeth M.D.; Singelyn, Francois M.D., Ph.D.; Bernard, Nathalie M.D.  Choquet, Olivier M.D.; Bouaziz, Herve M.D., Ph.D.; Bonnet, Francis M.D., Ph.D.;  the French Study Group on Continuous Peripheral Nerve Blocks 
Anesthesiology. 103(5):1035-1045, November 2005

Background: Continuous peripheral nerve block (CPNB) is the technique of choice for postoperative analgesia after painful orthopedic surgery. However, the incidence of neurologic and infectious adverse events in the postoperative period are not well established. This issue was the aim of the study.
Methods: Patients scheduled to undergo orthopedic surgery performed with a CPNB were prospectively included during 1 yr in a multicenter study. Efficacy of postoperative analgesia, bacteriologic cultures of the catheter, and acute neurologic and infectious adverse events were evaluated after surgery in 1,416 patients at arrival in the postanesthesia care unit, at hour 1, and every 24 h up to day 5. Risk factors for adverse events were determined using logistic regression.
Results: The median duration of CPNB was 56 h. Both general anesthesia and CPNB were performed in 73.6% of the patients. Postoperative analgesia was effective in 96.3%, but an increase in pain scores was noted at hour 24 (P = 0.01). Hypoesthesia or numbness occurred in 3% and 2.2%, respectively, and paresthesia occurred in 1.5%. Three neural lesions (0.21%) were noted after continuous femoral nerve block. Two of these patients were anesthetized during block procedure. Nerve damage completely resolved 36 h to 10 weeks later. Cultures from 28.7% of the catheters were positive. Three percent of patients had local inflammatory signs. The bacterial species most frequently found were coagulase-negative staphylococcus (61%) and gram-negative bacillus (21.6%). A Staphylococcus aureus psoas abscess (0.07%) was reported in one diabetic woman. Independent risk factors for paresthesia/dysesthesia were postoperative monitoring in intensive care, age less than 40 yr, and use of bupivacaine. Risk factors for local inflammation/infection were postoperative monitoring in intensive care, catheter duration greater than 48 h, male sex, and absence of antibiotic prophylaxis.
Conclusion: CPNB is an effective technique for postoperative analgesia. Minor incidents and bacterial colonization of catheters are frequent, with no adverse clinical consequences in the large majority of cases. Major neurologic and infectious adverse events are rare.

Investigation of Implicit Memory during Isoflurane Anesthesia for Elective Surgery Using the Process Dissociation Procedure.
Iselin-Chaves, Irene A. M.D.; Willems, Sylvie J. Ph.D.; Jermann, Francoise C. Dipl. Psych.; Forster, Alain M.D.; Adam, Stephane R. Ph.D.; Van der Linden, Martial Ph.D.
Anesthesiology. 103(5):925-933, November 2005

Background: This prospective study evaluated memory function during general anesthesia for elective surgery and its relation to depth of hypnotic state. The authors also compared memory function in anesthetized and nonanesthetized subjects.
Methods: Words were played for 70 min via headphones to 48 patients (aged 18-70 yr) after induction of general anesthesia for elective surgery. Patients were unpremedicated, and the anesthetic regimen was free. The Bispectral Index (BIS) was recorded throughout the study. Within 36 h after the word presentation, memory was assessed using an auditory word stem completion test with inclusion and exclusion instructions. Memory performance and the contribution of explicit and implicit memory were calculated using the process dissociation procedure. The authors applied the same memory task to a control group of nonanesthetized subjects.
Results: Forty-seven patients received isoflurane, and one patient received propofol for anesthesia. The mean (+/- SD) BIS was 49 +/- 9. There was evidence of memory for words presented during light (BIS 61-80) and adequate anesthesia (BIS 41-60) but not during deep anesthesia (BIS 21-40). The process dissociation procedure showed a significant implicit memory contribution but not reliable explicit memory contribution (mean explicit memory scores 0.05 +/- 0.14, 0.04 +/- 0.09, and 0.05 +/- 0.14; mean automatic influence scores 0.14 +/- 0.12, 0.17 +/- 0.17, and 0.18 +/- 0.21 at BIS 21-40, 41-60, and 61-80, respectively). Compared with anesthetized patients, the memory performance of nonanesthetized subjects was better, with a higher contribution by explicit memory and a comparable contribution by implicit memory.
Conclusion: During general anesthesia for elective surgery, implicit memory persists even in adequate hypnotic states, to a comparable degree as in nonanesthetized subjects.

Detection of Consciousness by Electroencephalogram and Auditory Evoked Potentials.
Schneider, Gerhard M.D.; Hollweck, Regina M.Sc.; Ningler, Michael M.Sc.; Stockmanns, Gudrun Ph.D.; Kochs, Eberhard F. M.D.
Anesthesiology. 103(5):934-943, November 2005

Background: A set of electroencephalographic and auditory evoked potential (AEP) parameters should be identified that allows separation of consciousness from unconsciousness (reflected by responsiveness/unresponsiveness to command).
Methods: Forty unpremedicated patients received anesthesia with remifentanil and either sevoflurane or propofol. With remifentanil infusion (0.2 [mu]g [middle dot] kg-1 [middle dot] min-1), patients were asked every 30 s to squeeze the investigator's hand. Sevoflurane or propofol was given until loss of consciousness. After intubation, propofol or sevoflurane was stopped until patients followed the command (return of consciousness). Thereafter, propofol or sevoflurane was started again (loss of consciousness), and surgery was performed. Return of consciousness was observed after surgery. The electroencephalogram and AEP from immediately before and after the transitions were selected. Logistic regression was calculated to identify models for the separation between consciousness and unconsciousness. For the top 10 models, 1,000-fold cross-validation was performed. Backward variable selection was applied to identify a minimal model. Prediction probability was calculated. The digitized electroencephalogram was replayed, and the Bispectral Index was measured and accordingly analyzed.
Results: The best full model (prediction probability 0.89) contained 15 AEP and 4 electroencephalographic parameters. The best minimal model (prediction probability 0.87) contained 2 AEP and 2 electroencephalographic parameters (median frequency of the amplitude spectrum from 8-30 Hz and approximate entropy). The prediction probability of the Bispectral Index was 0.737.
Conclusions: A combination of electroencephalographic and AEP parameters can be used to differentiate between consciousness and unconsciousness even in a very challenging data set. The minimal model contains a combination of AEP and electroencephalographic parameters and has a higher prediction probability than Bispectral Index for the separation between consciousness and unconsciousness.

ACTA ANAESTHESIOLOGICA SCANDINAVICA - VOLVER ARRIBA

None available.

 

BRITISH JOURNAL OF ANAESTHESIA - TOP

Onset and duration of mivacurium-induced neuromuscular block in patients with Duchenne muscular dystrophy
J. Schmidt, T. Muenster, S. Wick, J. Forst and H. J. Schmitt
British Journal of Anaesthesia 2005 95(6):769-772

 

Background. To determine the response to mivacurium, we prospectively studied onset time and complete spontaneous recovery from mivacurium-induced neuromuscular block in patients with Duchenne muscular dystrophy (DMD).
Methods. Twelve boys with DMD, age 5–14 yr, seven of them wheelchair-bound, ASA II–III, and 12 age- and sex-matched controls (ASA I) were enrolled in the study. Anaesthesia was induced with fentanyl 2–3 µg kg^–1 and propofol 3–4 mg kg^–1 titrated to effect, and maintained by continuous i.v. infusion of propofol 8–12 mg kg^–1 and remifentanil as required. The lungs were ventilated with oxygen in air. Neuromuscular transmission was assessed by acceleromyography using train-of-four (TOF) stimulation every 15 s. After baseline readings, a single dose of mivacurium 0.2 mg kg^–1 was given. The following variables were recorded: (i) lag time; (ii) onset time; (iii) peak effect; (iv) recovery of first twitch from the TOF response to 10, 25 and 90% (T₁₀, T₂₅, T₉₀) relative to baseline; (v) recovery index (time between 25 and 75% recovery of first twitch); and (vi) recovery time (time between 25% recovery of first twitch and recovery of TOF ratio to 90%). For comparison between the groups the Mann–Whitney U-test was applied.
Results. There were no differences between the groups in lag time, onset time and peak effect. However, all recorded recovery indices were significantly (P<0.05) prolonged in the DMD group. The median (range) for time points T₁₀, T₂₅ and T₉₀ in the DMD and control group was 12.0 (8–16) vs 8.4 (5–15) min, 14.1 (9–20) vs 10.5 (7–17) min and 26.9 (15–40) vs 15.9 (12–23) min, respectively. The recovery index and recovery time were similarly prolonged in the DMD group.

Conclusions. These results support the assumption that mivacurium-induced neuromuscular block is prolonged in patients with DMD.

 

 

A randomized non-crossover study comparing the ProSeal^TM and Classic^TM laryngeal mask airway in anaesthetized children
M. Lopez-Gil, J. Brimacombe and G. Garcia
British Journal of Anaesthesia 2005 95(6):827-830

 

Background. We tested the hypothesis that ease of insertion, oropharyngeal leak pressure, fibreoptic position, gastric insufflation, and the frequency of mucosal trauma differ between the ProSeal laryngeal mask airway (PLMA) and the classic laryngeal mask airway (cLMA) in anaesthetized children. For the PLMA, we also assessed the ease of gastric tube placement via the PLMA drain tube and measure residual gastric volume.

Methods. 240 consecutive ASA I–III children aged 1–16 yr were randomized for airway management with the ProSeal or cLMA.

Results. The time taken to provide an effective airway, the number of insertion attempts, fibreoptic position of the airway tube and frequency of mucosal trauma were similar, but oropharyngeal leak pressure was higher (33 vs 26 cm H₂O, P<0.0001) and gastric insufflation less common (0 vs 6%, P<0.01) for the PLMA. Gastric tube insertion was successful at the first attempt in 106 of 120, and at the second attempt in 14 of 120. The mean (SD; range) value for residual gastric volume was 2.2 (5.9; 0–30) ml. There were no differences in performance among sizes for the PLMA and the cLMA.

Conclusions. We conclude that ease of insertion, fibreoptic position, and frequency of mucosal trauma are similar for the PLMA and cLMA in children, but oropharyngeal leak pressure is higher and gastric insufflation less common for the PLMA. Gastric tube insertion has a high success rate, provided the PLMA is correctly positioned.

 

Use of the ProSeal^TM laryngeal mask airway for pressure-controlled ventilation with and without positive end-expiratory pressure in paediatric patients: a randomized, controlled study
K. Goldmann, C. Roettger and H. Wulf

British Journal of Anaesthesia 2005 95(6):831-834

 

Background. Tracheal intubation and positive end-expiratory pressure (PEEP) are frequently used in children to avoid airway closure and atelectasis during general anaesthesia. Also, the laryngeal mask airway (LMA) is frequently used. However, one of the limitations with its use in children is that its low-pressure seal is often inadequate for positive pressure ventilation with PEEP. The ProSeal^TM LMA (PLMA) has been shown to form a more effective seal than the Classic^TM LMA. The ability to apply PEEP with the PLMA might improve gas exchange during positive pressure ventilation in children when the LMA is used.

Methods. Twenty anaesthetized, non-paralysed children aged 55 (range 27–89) months, weighing 18 (SD 3) kg, were randomly allocated into two groups. Anaesthesia management and positive pressure ventilation were standardized. Size 2 and 2.5 PLMA were used. Artificial ventilation in Group I was with pressure controlled ventilation (PCV) and PEEP=5 cm H₂O, in Group II with PCV without PEEP. A FiO₂ = 1.0 was used for 20 min during induction of anaesthesia. Sixty minutes after induction of anaesthesia an arterial blood gas sample was taken under a FiO₂ = 0.3.

Results. Groups were comparable with respect to demographic data.  PaO₂ in Group I [22.1 (1.6) kPa] was significantly (P=0.001) higher than in Group II [19.2 (1.7) kPa].

Conclusions. The PLMA can be used for PCV with PEEP in paediatric patients. Application of PEEP improves gas exchange.

CANADIAN JOURNAL OF ANESTHESIA - TOP

Communication between anesthesiologists, patients and the anesthesia team: a descriptive study of induction and emergence
Andrew F. Smith, MRCP (UK), FRCA, Catherine Pope, PhD, Dawn Goodwin, PhD and Maggie Mort, PhD
Canadian Journal of Anesthesia 52:915-920 (2005)

 

Purpose: Although the importance of communication skills in anesthetic practice is increasingly recognized, formal communication skills training has hitherto dealt only with limited aspects of this professional activity. We aimed to document and analyze the informally-learned communication that takes place between anesthesia personnel and patients at induction of and emergence from general anesthesia.

Methods: We adopted an ethnographic approach based principally on observation of anesthesia personnel at work in the operating theatres with subsequent analysis of observation transcripts.

Results: We noted three main styles of communication on induction, commonly combined in a single induction. In order of frequency, these were: (1) descriptive, where the anesthesiologists explained to the patient what he/she might expect to feel; (2) functional, which seemed designed to help anesthesiologists maintain physiological stability or assess the changing depth of anesthesia and (3) evocative, which referred to images or metaphors. Although the talk we have described is nominally directed at the patient, it also signifies to other members of the anesthetic team how induction is progressing. The team may also contribute to the communication behaviour depending on the context. Communication on emergence usually focused on establishing that the patient was awake.

Conclusion: Communication at induction and emergence tends to fall into specific patterns with different emphases but similar functions. This communication work is shared across the anesthetic team. Further work could usefully explore the relationship between communication styles and team performance or indicators of patient safety or well-being.

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Tolerance of Laparoscopy and Thoracoscopy in Neonates
Marie-Pierre Guibal, Jean-Charles Picaud and René-Benoit Galifer, Nicolas Kalfa, Hossein Allal, Olivier Raux, Manuel Lopez, Dominique Forgues
Pediatrics. 2005 Dec;116(6):e785-91

Objectives. Video-surgery in neonates is recent. Data on the respiratory, hemodynamic, and thermic effects during the first month of life are still sparse. This study aimed to evaluate the tolerance of video-surgery in neonates and to determine the risk factors of per-operative complications.
Methods. From 1994 to 2004, 49 neonates (mean age: 11 days; weight: 3285 g) underwent 50 video-surgical procedures. Indications for laparoscopy were duodenal atresias, volvulus with malrotation, pyloric stenosis, gastroesophageal reflux, cystic lymphangiomas, ovarian cysts, biliary atresia, and congenital diaphragmatic hernias; indications for thoracoscopy were esophageal atresias and tracheoesophageal fistula.
Results. Median operative time was 79 minutes. Mean insufflation pressure was 6.7 mm Hg (range: 3–13). Oxygen saturation decreased, especially with thoracic insufflation or high-pressure pneumoperitoneum. Systolic arterial pressure, which decreased in 20% of the patients, was controlled easily with vascular expansion. Thermic loss (mean postoperative temperature: 35.6°C) was proportional to the duration of insufflation. No surgical incident was noted. Ten anesthetic incidents occurred (20%), 3 of which required temporary or definitive interruption of insufflation (O2 saturation <70%). Risk factors for an incident were low preoperative temperature, high variation of end-tidal pressure of CO2, surgical time >100 minutes, thoracic insufflation, and a high oxygen or vascular expansion requirement at the beginning of insufflation.
Conclusion. The neonate's high sensitivity to insufflation is an important limiting factor of video-surgery. The described profile of the neonate at risk may help to reduce the frequency of adverse effects of this technique and improve its tolerance.

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