Regional Anesthesia, Intraneural Injection, and Nerve Injury: Beyond the Epineurium [Editorial]
Borgeat, Alain

This Editorial View accompanies the following article: Bigeleisen PE: Nerve puncture and apparent intraneural injection during ultrasound-guided axillary block do not invariably result in neurologic injury.
Anesthesiology 2006; 105:779-83.

Nerve Puncture and Apparent Intraneural Injection during Ultrasound-guided Axillary Block Does Not Invariably Result in Neurologic Injury.
Bigeleisen, Paul E. M.D.
Pain and Regional Anesthesia
Anesthesiology. 105(4):779-783, October 2006.

Background: Nerve puncture by the block needle and intraneural injection of local anesthetic are thought to be major risk factors leading to neurologic injury after peripheral nerve blocks. In this study, the author sought to determine the needle-nerve relation and location of the injectate during ultrasound-guided axillary plexus block.
Methods: Using ultrasound-guided axillary plexus block (10-MHz linear transducer, SonoSite, Bothel, WA; 22-gauge B-bevel needle, Becton Dickinson, Franklin Parks, NJ), the incidence of apparent nerve puncture and intraneural injection of local anesthetic was prospectively studied in 26 patients. To determine the onset, success rate, and any residual neurologic deficit, qualitative sensory and quantitative motor testing were performed before and 5 and 20 min after block placement. At a follow-up 6 months after the blocks, the patients were examined for any neurologic deficit.
Results: Twenty-two of 26 patients had nerve puncture of at least one nerve, and 21 of 26 patients had intraneural injection of at least one nerve. In the entire cohort, 72 of a total of 104 nerves had intraneural injection. Sensory and motor testing before and 6 months after the nerve injections were unchanged.
Conclusions: Under the conditions of this study, puncturing of the peripheral nerves and apparent intraneural injection during axillary plexus block did not lead to a neurologic injury.

Can Anesthetic Technique for Primary Breast Cancer Surgery Affect Recurrence or Metastasis?
Exadaktylos, Aristomenis K. M.D. ; Buggy, Donal J. M.D., M.Sc., D.M.E., F.R.C.P.I., F.C.A.R.C.S.I., F.R.C.A. ; Moriarty, Denis C. F.C.A.R.C.S.I. ; Mascha, Edward Ph.D. ; Sessler, Daniel I. M.D., Ph.D.
Anesthesiology. 105(4):660-664, October 2006.

Background: Regional anesthesia is known to prevent or attenuate the surgical stress response; therefore, inhibiting surgical stress by paravertebral anesthesia might attenuate perioperative factors that enhance tumor growth and spread. The authors hypothesized that breast cancer patients undergoing surgery with paravertebral anesthesia and analgesia combined with general anesthesia have a lower incidence of cancer recurrence or metastases than patients undergoing surgery with general anesthesia and patient-controlled morphine analgesia.
Methods: In this retrospective study, the authors examined the medical records of 129 consecutive patients undergoing mastectomy and axillary clearance for breast cancer between September 2001 and December 2002.
Results: Fifty patients had surgery with paravertebral anesthesia and analgesia combined with general anesthesia, and 79 patients had general anesthesia combined with postoperative morphine analgesia. The follow-up time was 32 +/- 5 months (mean +/- SD). There were no significant differences in patients or surgical details, tumor presentation, or prognostic factors. Recurrence- and metastasis-free survival was 94% (95% confidence interval, 87-100%) and 82% (74-91%) at 24 months and 94% (87-100%) and 77% (68-87%) at 36 months in the paravertebral and general anesthesia patients, respectively (P = 0.012).
Conclusions: This retrospective analysis suggests that paravertebral anesthesia and analgesia for breast cancer surgery reduces the risk of recurrence or metastasis

Recurrent Hypoxemia in Children Is Associated with Increased Analgesic Sensitivity to Opiates.
Brown, Karen A. M.D. ; Laferriere, Andre B.A. ; Lakheeram, Indrani M.D. ; Moss, Immanuela Rave M.D., Ph.D.
Anesthesiology. 105(4):665-669, October 2006.

Background: Postsurgical administration of opiates in patients with obstructive sleep apnea (OSA) has recently been linked to an increased risk for respiratory complications. The authors have attributed this association to an effect of recurrent oxygen desaturation accompanying OSA on endogenous opioid mechanisms that, in turn, alter responsiveness to subsequent administration of exogenous opiates. In a retrospective study, the authors have shown that oxygen desaturation and young age in children with OSA are correlated with a reduced opiate requirement for postoperative analgesia.
Methods: The current study was designed to test that conclusion prospectively in 22 children with OSA scheduled to undergo adenotonsillectomy. The children were stratified to those having displayed < 85% or >= 85% oxygen saturation nadir during sleep preoperatively. Using a blinded design, the children were given morphine postoperatively to achieve an identical behavioral pain score.
Results: As compared with children in the >= 85% group, the < 85% oxygen saturation nadir group required one half the total analgesic morphine dose postoperatively, indicating heightened analgesic sensitivity to morphine after recurrent hypoxemia.
Conclusions: Previous recurrent hypoxemia in OSA is associated with increased analgesic sensitivity to subsequent morphine administration. Therefore, opiate dosing in

Decrease of Functional Residual Capacity and Ventilation Homogeneity after Neuromuscular Blockade in Anesthetized Young Infants and Preschool Children.
von Ungern-Sternberg, Britta S. M.D. ; Hammer, Jurg M.D. ; Schibler, Andreas M.D. ; Frei, Franz J. M.D. ; Erb, Thomas O. M.D.
Anesthesiology. 105(4):670-675, October 2006.

Background: Based on age-dependent differences in pulmonary mechanics, the effect of neuromuscular blockade may differ in infants compared with older children. The aim of this study was to determine the impact of neuromuscular blockade and its reversal by positive end-expiratory pressure (PEEP) on functional residual capacity (FRC) and ventilation distribution in young infants and preschool children.
Methods: The authors studied 14 infants (aged 0-6 months) and 25 preschool children (aged 2-6 yr). FRC and lung clearance index were calculated. Measurements were taken (1) after intubation, (2) during neuromuscular blockade, and (3) during neuromuscular blockade plus application of PEEP (3 cm H₂O).
Results: Functional residual capacity (mean +/- SD) decreased from 21.3 +/- 4.7 ml/kg to 12.2 +/- 4.8 ml/kg (P < 0.001) during neuromuscular blockade in infants and from 25.6 +/- 5.9 ml/kg to 23.0 +/- 5.3 ml/kg (P < 0.001) in preschool children. With the application of PEEP, FRC increased to 22.3 +/- 5.9 ml/kg (P = 0.4829, compared with baseline) in infants and 28.2 +/- 5.8 ml/kg (P < 0.001) in children. The lung clearance index increased after neuromuscular blockade, whereas baseline values were regained after the application of PEEP. The changes induced by neuromuscular blockade were significantly greater in infants compared with preschool children (P < 0.001).
Conclusions: Although the use of neuromuscular blockade decreased FRC and ventilation distribution substantially in both groups, the changes were more pronounced in young infants. With PEEP, FRC increased and ventilation homogeneity was restored. These results provide a rationale to use PEEP in anesthetized, paralyzed infants and children.

Alfentanil Dosage When Inserting the Classic Laryngeal Mask Airway.
Yu, Andrea L. Y. M.B.B.S., F.A.N.Z.C.A. ; Critchley, Lester A. H. M.D., F.F.A.R.C.S.I. ; Lee, Anna Ph.D., M.P.H. ; Gin, Tony M.D., F.A.N.Z.C.A.
Anesthesiology. 105(4):684-688, October 2006.

Background: The purpose of this study was to determine an optimum dose of alfentanil, coadministered with 2.5 mg/kg propofol, when inserting a classic laryngeal mask airway.
Methods: Seventy-five adult ethnic Chinese patients with an American Society of Anesthesiologists physiologic status classification I or II and requiring anesthesia for minor surgery with a laryngeal mask were recruited. They were randomly assigned to five dosage groups: placebo or 5, 10, 15, or 20 [mu]g/kg. The study drug plus propofol were administered, and 90 s later, insertion conditions were assessed using a six-category score. The duration of apnea was recorded. A probit analysis was performed and used to estimate the ED50 and ED95 with 95% confidence intervals for each assessment.
Results: Twenty-five male and 50 female patients, aged 18-59 yr, were studied. The five groups were similar. Laryngeal mask insertion was successful in all but one alfentanil patient. Duration of apnea increased with increasing dosage of alfentanil to over 5 min (P < 0.001). Dose-responses could not be predicted for categories of resistance to mouth opening and to insertion. For the other four categories, swallowing, gagging, movement, and laryngospasm, ED50 and ED95 with confidence intervals for alfentanil could be determined.
Conclusion: The optimum dose for alfentanil, when coadministered with 2.5 mg/kg propofol, was 10 [mu]g/kg.

ACTA ANAESTHESIOLOGICA SCANDINAVICA - TOP

Fentanyl reduces desflurane-induced airway irritability following thiopental administration in children
J. Lee, Y. Oh, C. Kim, S. Kim, H. Park and H. Kim
Acta Anaesthesiologica Scandinavica Volume 50 Page 1161  - October 2006

Background: Airway irritation is a major drawback of desflurane anesthesia. This study was designed to evaluate the effect of intravenous fentanyl given before thiopental induction on airway irritation caused by a stepwise increase in desflurane in children.
Methods: Eighty children (2–8 years) were enrolled in a randomized, double-blind study. Forty received saline and 40 received 2 μg/kg of fentanyl intravenously; this was followed by thiopental sodium 5 mg/kg in both groups. Patients were assistant-ventilated with desflurane 1%, which was then increased by 1% every six breaths up to 10%. During this period, cough, secretion, excitation and apnea were graded and the desflurane concentration at which airway irritation symptoms first occurred was recorded. The results were analyzed using Pearson's chi-squared test.
Results: The incidence of typical airway irritation events was lower with fentanyl than with saline (cough, 2.5% vs. 42.5%; secretion, 27.5% vs. 82.5%; excitation, 10% vs. 82.5%; apnea, 20% vs. 65%; P < 0.05). The mean expired desflurane concentration at which the first airway irritation symptom occurred was greater with fentanyl than with saline (7.3% vs. 5.5%, P < 0.05).
Conclusions: Intravenous fentanyl in children reduces airway complications caused by desflurane.

BRITISH JOURNAL OF ANAESTHESIA - TOP

Prophylaxis of postoperative vomiting in children undergoing tonsillectomy: a systematic review and meta-analysis
C. M. Bolton, P. S. Myles, T. Nolan and J. A. Sterne
British Journal of Anaesthesia 2006 97(5):593-604

Postoperative vomiting (POV) remains one of the commonest causes of significant morbidity after tonsillectomy in children. A variety of prophylactic anti-emetic interventions have been reported, but there has only been a limited systematic review in this patient group. A systematic search was performed by using Cochrane Controlled Trials Register, MEDLINE and EMBASE to identify double-blind, randomized, placebo-controlled trials of prophylactic anti-emetic interventions in children undergoing tonsillectomy, with or without adenoidectomy. The outcome of interest was POV in the first 24 h. Summary estimates of the effect of each prophylactic anti-emetic strategy were derived using fixed effect meta-analysis. Where appropriate, dose–response effects were estimated using logistic regression and 22 articles were identified. Good evidence was found for the prophylactic anti-emetic effect of dexamethasone [odds ratio (OR) 0.23, 95% CI 0.16–0.33], and the serotinergic antagonists ondansetron (OR 0.36, 95% CI 0.29–0.46), granisetron (OR 0.11, 95% CI 0.06–0.19), tropisetron (OR 0.15, 95% CI 0.06–0.35) and dolasetron (OR 0.25, 95% CI 0.1–0.59). Metoclopramide was also found to be efficacious (OR 0.51, 95% CI 0.34–0.77). There is not sufficient evidence to suggest that dimenhydrinate, perphenazine or droperidol, in the doses studied, are efficacious, nor were gastric aspiration or acupuncture. In conclusion, dexamethasone and the anti-serotinergic agents appear to be the most effective agents for the prophylaxis for POV in children undergoing tonsillectomy.

Inspired oxygen fraction of 0.8 compared with 0.4 does not further reduce postoperative nausea and vomiting in dolasetron-treated patients undergoing laparoscopic cholecystectomy
S. N. Piper, K. D. Röhm, J. Boldt, K. L. Faust, W. H. Maleck, P. Kranke and S. W. Suttner
British Journal of Anaesthesia 2006 97(5):647-653

Background. Postoperative nausea and vomiting (PONV) is one of the most frequent complications after general anaesthesia. Single-dose antiemetic prophylaxis has limited efficacy in high-risk patients. Adding a simple potential antiemetic approach, such as increasing the inspired oxygen fraction, to the antiemetic portfolio would preserve pharmacological interventions for treatment of symptoms in the postoperative period. However, the antiemetic effect of a high inspired oxygen fraction is still discussed controversially. The aim of the study was to evaluate whether an inspired oxygen fraction of 0.8 decreases PONV in patients receiving the 5-HT3-antagonist dolasetron.
Methods. In a randomized, placebo-controlled, double-blinded trial we studied 377 patients (ASA I–III) undergoing elective laparoscopic cholecystectomy. Induction of anaesthesia was standardized, including thiopental, fentanyl and cis-atracurium. For all patients the individual risk for PONV was calculated using the Koivuranta score and all patients received 12.5 mg dolasetron i.v. before surgery. Patients were allocated randomly to one of three groups: Group A (n=125) received 80% oxygen in air, Group B (n=125) 40% oxygen in air and Group C (n=127) 40% oxygen in nitrous oxide. Postoperative nausea, postoperative vomiting (PV), or nausea, vomiting, or both (PONV) was assessed in the early (0–4 h) and overall postoperative period (0–24 h) by an anaesthesiologist unaware of patient allocation.
Results. There was a significantly lower incidence of PONV and PV in Groups A (PONV: 11.2%; PV: 3.2%) and B (PONV: 10.4%; PV: 3.2%) compared with Group C (PONV: 26.7%; PV: 13.3%), but there were no significant differences between Groups A and B.
Conclusions. An inspired oxygen fraction of 0.8 does not further decrease PONV or vomiting in dolasetron-treated patients undergoing laparoscopic cholecystectomy. The lower incidence of PONV in Groups A and B compared with Group C is most likely caused by the omission of nitrous oxide.

General anaesthesia for the cocaine abusing patient. Is it safe?
G. E. Hill, B. O. Ogunnaike and E. R. Johnson
British Journal of Anaesthesia 2006 97(5):654-657

Background. Commonly, cocaine abusing patient are scheduled for elective surgery with a positive urine test for cocaine metabolites. As many of these patients were clinically non-toxic [normal arterial pressure and heart rate, normothermic, and a normal (or unchanged from previous) ECG, including a QTc interval <500 ms], we have recently proceeded with elective surgery requiring general anaesthesia in this patient group.
Methods. Forty urine cocaine positive patients were compared with an equal number of drug-free controls in a prospective, non-randomized, blinded analysis. Intraoperative mean arterial blood pressure, ST segment analysis, heart rate and body temperature were recorded and compared.
Results. Cardiovascular stability during and after general anaesthesia in cocaine positive, non-toxic patients was not significantly different when compared with an age and ASA matched drug-free control group.
Conclusions. These results demonstrate that the non-toxic cocaine abusing patient can be administered general anaesthesia with no greater risk than comparable age and ASA matched drug-free patients.

Tracheal intubation of morbidly obese patients: LMA CTrach^TM vs direct laryngoscopy
G. Dhonneur, S. K. Ndoko, A. Yavchitz, A. Foucrier, C. Fessenmeyer, C. Pollian, X. Combes and L. Tual
British Journal of Anaesthesia 2006 97(5):742-745

Background. LMA CTrach^TM (CT), a modified version of the intubating LMA FastrachTM, allows continuous video-endoscopy of the tracheal intubation procedure. We tested the hypothesis that the CT is efficient for tracheal intubation of morbidly obese patients who are at risk of a difficult airway.
Methods. After Ethics’ Committee approval, 104 morbidly obese patients (BMI >35 kg m–2) scheduled for bariatric surgery were included in this prospective study. Patients were randomly assigned in two groups: tracheal intubation using direct laryngoscopy (DL) or the CT. Induction of anaesthesia was standardized using sufentanil, propofol and succinylcholine. Characteristics and consequences of airway management were evaluated.
Results. Preoperative characteristics of patients and consequences of anaesthesia induction on physiological variables were similar in both groups. Difficulty in facemask ventilation was similar in both groups. Tracheal intubation was successfully carried out with DL and CT. Forty-nine per cent of the patients from the CT group required laryngeal mask manipulation (ventilation and view optimization) resulting in increased duration of tracheal intubation by 57 s as compared with DL. Oxygenation was of better quality in the patients managed with CT than with DL. Blind tracheal intubation was mandatory in eight (17%) patients of the DL group, while tracheal intubation was seen in all patients of the CT group.
Conclusion. We demonstrated that the CT was an efficient airway device for ventilation and tracheal intubation in case of a difficult airway in morbidly obese patients.

CANADIAN JOURNAL OF ANESTHESIA - TOP

Epidural dexamethasone reduces postoperative pain and analgesic requirements
Siji Thomas, MD and Suhara Beevi, MD
Canadian Journal of Anesthesia 53:899-905 (2006)

Purpose: Epidural steroids may have potential advantages for providing postoperative analgesia. We therefore undertook a study to evaluate the efficacy of epidurally administered dexamethasone in reducing postoperative morphine requirements, as a measure of analgesia following laparoscopic cholecystectomy.
Methods: In a randomized, double-blind study, 94 patients undergoing laparoscopic cholecystectomy were randomly assigned to one of three groups. Group 1 (Control) patients received dexamethasone 5 mg iv with epidural injection of 0.25% bupivacaine 8 mL and normal saline 2 mL, Group 2 (D1) patients received normal saline 2 mL iv with epidural injection of 0.25% bupivacaine 8 mL and dexamethasone 5 mg in normal saline 2 mL, and Group 3 (D2) patients received normal saline 2 mL iv with epidural injection of dexamethasone 5 mg in normal saline 10 mL. After surgery, morphine 2–4 mg iv was administered as needed for analgesia. Postoperative morphine requirements, visual analogue scale (VAS) pain scores at rest and with effort, and time to first analgesic administration were recorded by a blinded observer.
Results: Total morphine consumption for the first 24 hr following surgery was lower in both epidural dexamethasone groups (D1, D2) compared to the control group (P < 0.05). The percentage reduction in morphine consumption in Group D1 was 53.9% and in Group D2 was 52.9% in the first 24 hr. Postoperatively at 12 hr, 18 hr and 24 hr, the VAS scores at rest and during effort were also lower in the epidural dexamethasone groups (D1, D2) compared to the control group (P < 0.05). The percentage reductions in VAS scores with effort at 12 hr, 18 hr and 24 hr in Group D1 were 50%, 52.9% and 50% respectively, and in Group D2 percentage reductions in pain scores with effort were 54.8%, 58.8% and 55.5% at corresponding sampling intervals.
Conclusion: Preoperative epidural administration of dexamethasone 5 mg, with or without bupivacaine, reduces postoperative pain and morphine consumption following laparoscopic cholecystectomy.

PUB MED - TOP

      
Anaesthetic drugs: linking molecular actions to clinical effects.
Grasshoff C, Drexler B, Rudolph U, Antkowiak B.
Department of Anesthesiology, Experimental Anesthesiology Section, University of Tuebingen, Schaffhausenstr. 113, D-72072 Tuebingen, Germany. christian.grasshoff@uni-tuebingen.de
Curr Pharm Des. 2006;12(28):3665-79

The use of general anaesthetics has facilitated great advantages in surgery within the last 150 years. General anaesthesia is composed of several components including analgesia, amnesia, hypnosis and immobility. To achieve these components, general anaesthetics have to act via multiple molecular targets at different anatomical sites in the central nervous system. Much of our current understanding of how anaesthetics work has been obtained within the last few years on the basis of genetic approaches, in particular knock-out or knock-in mice. Anaesthetic drugs can be grouped into volatile and intravenous anaesthetics according to their route of administration. Common volatile anaesthetics induce immobility via molecular targets in the spinal cord, including glycine receptors, GABA(A) receptors, glutamate receptors, and TREK-1 potassium channels. In contrast, intravenous anaesthetics cause immobility almost exclusively via GABA(A) receptors harbouring beta3 subunits. Hypnosis is predominantly mediated by beta3-subunit containing GABA(A) receptors in the brain, whereas beta2 subunit containing receptors, which make up more than 50% of all GABA(A) receptors in the central nervous system, mediate sedation. At clinically relevant concentrations, ketamine and nitrous oxide block NMDA receptors. Unlike all other anaesthetics in clinical use they produce analgesia. Not only desired actions of anaesthetics, but also undesired side effects are linked to certain receptors. Respiratory depression involves beta3 containing GABA(A) receptors whereas hypothermia is largely mediated by GABA(A) receptors containing beta2 subunits. These recent insights into the clinically desired and undesired actions of anaesthetic agents provide new avenues for the design of drugs with an improved side-effect profile. Such agents would be especially beneficial for the treatment of newborn children, elderly patients and patients undergoing ambulatory surgery.

Twelve years' local experience in ambulatory anaesthesia.
Lai AK, Ho V, Chow YF.
Department of Anaesthesia, Queen Elizabeth Hospital, Hong Kong. laikw2000@hotmail.com
Hong Kong Med J. 2006 Oct;12(5):339-44.

OBJECTIVES: To determine the incidence of adverse events after ambulatory anaesthesia (postoperative nausea and vomiting, postoperative pain, difficulty in movement), and to evaluate the level of satisfaction of patients with our service. DESIGN: Retrospective study with questionnaire survey.
SETTING: Tertiary referral centre, Hong Kong.
PARTICIPANTS: All patients whose duly completed questionnaires were available. MAIN OUTCOME MEASURES: Incidence of adverse events and level of patient satisfaction.
RESULTS: A total of 9197 patients underwent surgery under general anaesthesia or neuraxial blockade by anaesthetists in ambulatory settings from October 1993 to December 2005: questionnaires filled out by 8231 of these patients were analysed, whereas 549 questionnaires were lost, and 417 patients could not be contacted. The response rate was 90%; 59% of the respondents were males, 50% were younger than 15 years and 5% older than 60 years. Fifty-one percent of surgery with anaesthetists' involvement was performed under general anaesthesia and 48.9% under general anaesthesia and regional blocks and 0.1% under neuraxial blockade. There were 3.3% of patients experienced postoperative nausea and vomiting, 60.2% experienced episodes of pain between the time of discharge and the time of interview, and 46% required analgesics. Nonetheless, 80% resumed normal activities within 5 hours after anaesthesia and 97.5% resumed normal diet the following morning. Over 99% rated our service as good or excellent.
CONCLUSION: Although ambulatory anaesthesia was associated with minor adverse events, patients could resume normal diet and daily activities quickly and were satisfied with the service.

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