Comparison of Mucosal Pressures Induced by Cuffs of Different Airway Devices.
Ulrich-Pur, Herbert M.D.; Hrska, Franz M.D.; Krafft, Peter M.D. et al..  Anesthesiology. 104(5):933-938, May 2006.

Background: High pressures exerted by balloons and cuffs of conventional endotracheal tubes, the Combitube(R) (Tyco Healthcare Nellcor Mallinckrodt, Pleasanton, CA), the EasyTube(R) (Teleflex Ruesch, Kernen, Germany), the Laryngeal Mask Airway^[TM] (LMA North America, San Diego, CA), the Intubating Laryngeal Mask Airway^[TM] (Fastrach(R); LMA North America), the ProSeal^[TM] (LMA North America), and the Laryngeal Tube (LT; VBM Medizintechnik, Sulz, Germany) may traumatize the pharyngeal mucosa. The aim of this study was to compare pressures exerted on the pharyngeal, tracheal, and esophageal mucosa by different devices designed for securing the patient's airways.
Methods: Nineteen fresh cadavers were included. To measure mucosal pressures, microchip sensors were fixed on the anterior, lateral, and posterior surfaces of the proximal balloon and the distal cuff of the investigated devices. Depending on the respective airway device, the cuff volume was increased in 10-ml increments at the proximal balloon starting from 0 to a maximum of 100 ml, and in 2-ml increments at the distal cuff starting from 0 up to 12 ml.
Results: Tracheal mucosal pressures were significantly higher using the Combitube(R) compared with the endotracheal tube and the EasyTube(R). Maximal esophageal pressures were significantly higher using the EasyTube(R) compared with the Combitube(R). Using cuff volumes according to the manufacturers' guidelines, we found the highest pharyngeal pressures with the Intubating Laryngeal Mask Airway^[TM] versus all other devices. At maximal volumes, the Laryngeal Mask Airway^[TM], the Intubating Laryngeal Mask Airway^[TM], and the ProSeal^[TM] induced significantly higher pharyngeal pressures compared with all other devices. Using a pharyngeal cuff volume of 40 ml, the Intubating Laryngeal Mask Airway^[TM]] followed by the Laryngeal Mask Airway^[TM] exerted significantly higher pressures compared with the other devices.
Conclusions: Although some devices exhibit a somewhat higher mucosal pressure when compared with others, the authors believe that the observed differences of the cuff pressures do not suggest a clinically relevant danger, because the investigated devices, except the endotracheal tubes, are not intended for prolonged use.

Geographic Regional Differences in Rocuronium Bromide Dose-Response Relation and Time Course of Action: An Overlooked Factor in Determining Recommended Dosage.
Dahaba, Ashraf A. M.D., Ph.D., M.Sc. ; Perelman, Seth I. M.D. ; Moskowitz, David M. M.D. et al. 
Anesthesiology. 104(5):950-953, May 2006.

Background: Geographic location is not acknowledged as a stratifying factor that can directly affect drug potency, because drugs are still licensed with the same recommended dose for different geographic regions. The aim of the current study was to compare the potency and duration of action of rocuronium bromide in 54 patients in three countries with different life habits, diet, and ambient conditions, namely white Austrians, white North Americans, and Han Chinese in China.
Methods: Neuromuscular block of six consecutive 50-[µ]g/kg rocuronium incremental doses followed by 300 [µ]g/kg was evaluated using the Relaxometer mechanomyograph (Groningen University, Groningen, Holland). Dose-response curves were created using log-dose-probit transformation. The authors compared rocuronium bromide ED50, ED90, and ED95 (effective doses required for 50%, 90%, and 95% first twitch depression, respectively) as well as Dur25 and Dur0.8 (times from last incremental dose administration until 25% first twitch and 0.8 train-of-four ratio recovery, respectively) in patients of the three countries.
Results: Rocuronium ED50, ED90, and ED95 were significantly higher in Austrian patients (258 +/- 68, 530 +/- 159, and 598 +/- 189 [µ]g/kg) and Chinese patients (201 +/- 59, 413 +/- 107, and 475 +/- 155 [µ]g/kg) compared with American patients (148 +/- 48, 316 +/- 116, and 362 +/- 149 [µ]g/kg, respectively). Dur25 and Dur0.8 were significantly shorter in Austrian patients (22.3 +/- 5.5 and 36.9 +/- 12.8 min) and Chinese patients (30.4 +/- 7.5 and 45.7 +/- 15.9 min) compared with American patients (36.7 +/- 8.5 and 56.2 +/- 16.7 min, respectively).
Conclusions: The authors demonstrated a significant difference in rocuronium potency and duration of action among patients in the three countries. Larger studies are required for determining dosage recommendations for different geographic regions.

Effect of Postoperative Experiences on Willingness to Pay to Avoid Postoperative Pain, Nausea, and Vomiting.
van den Bosch, Jolanda E. M.Sc. ; Bonsel, Gouke J. M.D., Ph.D. ; Moons, Karel G. Ph.D. ; Kalkman, Cor J. M.D., Ph.D. 
Anesthesiology. 104(5):1033-1039, May 2006.

Background: The authors assessed the willingness to pay (WTP) for "perfect" prophylactic antiemetics and analgesics in patients who were scheduled to undergo surgery during general anesthesia. Furthermore, they determined whether postoperative experiences of pain and nausea and vomiting (PONV) changed patients' WTP.
Methods: Data were collected alongside a randomized clinical trial that investigated the incidence of PONV in patients anesthetized with either inhalation anesthesia or total intravenous anesthesia. A subset of 808 consecutive patients participating in the trial completed WTP questionnaires 1 day before and 2 weeks after surgery. The outcome measure was the maximum amount of money that patients were willing to pay for "perfect" antiemetics and analgesics. Preoperative WTP and individual WTP changes after surgery were analyzed in relation to baseline characteristics and postoperative pain and PONV experiences.
Results: Prevention of postoperative pain was valued higher than prevention of PONV. The median preoperative WTP for analgesics was US $35 (interquartile range, $7-69) vs. US $17 (interquartile range, $7-69) for antiemetics. Individual WTP changes for antiemetics were not related to PONV experience, whereas severe postoperative pain (numerical rating score >= 8) was associated with an increase in the WTP for analgesics.
Conclusions: Severe postoperative pain experiences increased patients' WTP for analgesics, but PONV did not increase WTP for antiemetics. The elicited WTP values were lower than those reported in previous studies, which is possibly related to differences in market culture or patients' attitudes toward postoperative pain, nausea, and vomiting.

CME Practice Guidelines for the Perioperative Management of Patients with Obstructive Sleep Apnea: A Report by the American Society of Anesthesiologists Task Force on Perioperative Management of Patients with Obstructive Sleep Apnea.
Anesthesiology: Volume 104(5) May 2006 pp 1081-1093

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BRITISH JOURNAL OF ANAESTHESIA - TOP

Acute toxic effects of ‘Ecstasy’ (MDMA) and related compounds: overview of pathophysiology and clinical management
A. P. Hall and J. A. Henry
British Journal of Anaesthesia 2006 96(6):678-685

Since the late 1980s ‘Ecstasy’ (3,4-methylenedioxymethamphetamine, MDMA) has become established as a popular recreational drug in western Europe. The UK National Criminal Intelligence Service estimates that 0.5–2 million tablets are consumed weekly in Britain. It has been reported that 4.5% of young adults (15–34 yr) in the UK have used MDMA in the previous 12 months. Clinically important toxic effects have been reported, including fatalities. While the phenomenon of hyperpyrexia and multi-organ failure is now relatively well known, other serious effects have become apparent more recently. Patients with acute MDMA toxicity may present to doctors working in Anaesthesia, Intensive Care and Emergency Medicine. A broad knowledge of these pathologies and their treatment is necessary for anyone working in an acute medical speciality. An overview of MDMA pharmacology and acute toxicity will be given followed by a plan for clinical management.

Dexmedetomidine vs midazolam for monitored anaesthesia care during cataract surgery
J. A. Alhashemi
British Journal of Anaesthesia 2006 96(6):722-726

Background. Cataract surgery is commonly performed under local anaesthesia with midazolam sedation. Dexmedetomidine, a sedative-analgesic, is devoid of respiratory depressant effects, and its use in cataract surgery has not been reported. This double-blind study compared the use of dexmedetomidine and midazolam in patients undergoing cataract surgery.
Methods. Forty-four patients undergoing cataract surgery under peribulbar anaesthesia randomly received either i.v. dexmedetomidine 1 µg kg^-1 over 10 min; followed by 0.1–0.7 µg kg^-1 h^-1 i.v. infusion (Group D), or midazolam 20 µg kg^-1 i.v.; followed by 0.5 mg i.v. boluses as required (Group M). Sedation was titrated to a Ramsay sedation score of 3. Mean arterial pressure (MAP), heart rate (HR), readiness for recovery room discharge (time to Aldrete score of 10), and patients' and surgeons' satisfaction (on a scale of 1–7) were determined.
Results. MAP and HR were lower in Group D compared with Group M [86 (SE 3) vs 102 (3) mm Hg and 65 (2) vs 72 (2) beats min^-1, respectively] (P<0.05). Group D patients had slightly higher satisfaction with sedation [median (IQR): 6 (6–7) vs 6 (5–7), P<0.05], but delayed readiness for discharge [45 (36–54) vs 21 (10–32) min, P<0.01] compared with patients in Group M. Surgeons' satisfaction was comparable in both groups [5 (4–6) vs 5 (4–6)].
Conclusion. Compared with midazolam, dexmedetomidine does not appear to be suitable for sedation in patients undergoing cataract surgery. While there was a slightly better subjective patient satisfaction, it was accompanied by relative cardiovascular depression and delayed recovery room discharge.

Ondansetron does not reduce the shivering threshold in healthy volunteers
R. Komatsu, M. Orhan-Sungur, J. In, T. Podranski, T. Bouillon, R. Lauber, S. Rohrbach and D. Sessler
British Journal of Anaesthesia 2006 96(6):732-737

Background. Ondansetron, a serotonin-3 receptor antagonist, reduces postoperative shivering. Drugs that reduce shivering usually impair central thermoregulatory control, and may thus be useful for preventing shivering during induction of therapeutic hypothermia. We determined, therefore, whether ondansetron reduces the major autonomic thermoregulatory response thresholds (triggering core temperatures) in humans.
Methods. Control (placebo) and ondansetron infusions at the target plasma concentration of 250 ng ml–1 were studied in healthy volunteers on two different days. Each day, skin and core temperatures were increased to provoke sweating; then reduced to elicit peripheral vasoconstriction and shivering. We determined the core-temperature sweating, vasoconstriction and shivering thresholds after compensating for changes in mean-skin temperature. Data were analysed using t-tests and presented as means (SDs); P<0.05 was taken as significant.
Results. Ondensetron plasma concentrations were 278 (57), 234 (55) and 243 (58) ng ml–1 at the sweating, vasoconstriction and shivering thresholds, respectively; these corresponded to ~50 mg of ondansetron which is approximately 10 times the dose used for postoperative nausea and vomiting. Ondansetron did not change the sweating (control 37.4 (0.4)°C, ondansetron 37.6 (0.3)°C, P=0.16), vasoconstriction (37.0 (0.5)°C vs 37.1 (0.3)°C; P=0.70), or shivering threshold (36.3 (0.5)°C vs 36.3 (0.6)°C; P=0.76). No sedation was observed on either study day.
Conclusions. Ondansetron appears to have little potential for facilitating induction of therapeutic hypothermia.

Emergence delirium in adults in the post-anaesthesia care unit
C. Lepousé, C. A. Lautner, L. Liu, P. Gomis and A. Leon
British Journal of Anaesthesia 2006 96(6):747-753

Background. Emergence delirium in the post-anaesthesia care unit (PACU) is poorly understood. The goal of this prospective study was to determine frequency and risk factors of emergence delirium in adults after general anaesthesia.
Methods. In this prospective study, 1359 consecutive patients were included. Contextual risk factors and occurrence of delirium according to the Riker sedation scale were documented. Groups were defined for the analysis according to the occurrence or not of agitation, then after exclusion of patients with preoperative anxiety and neuroleptics, or both, and antidepressants or benzodiazepines treatments.
Results. Sixty-four (4.7%) patients developed delirium in the PACU, which can go from thrashing to violent behaviour and removal of tubes and catheters. Preoperative anxiety was not found to be a risk factor. Preoperative medication by benzodiazepines (OR=1.910, 95% CI=1.101–3.315, P=0.021), breast surgery (OR=5.190, 95% CI=1.422–18.947, P=0.013), abdominal surgery (OR=3.206, 95% CI=1.262–8.143, P=0.014), and long duration of surgery increased the risk of delirium (OR=1.005, 95% CI=1.002–1.008, P=0.001), while a previous history of illness and long-term treatment by antidepressants decreased the risk (respectively, OR=0.544, 95% CI=0.315–0.939, P=0.029 and OR=0.245, 95% CI=0.084–0.710, P=0.010).
Conclusions. Preoperative benzodiazepines, breast and abdominal surgery and surgery of long duration are risk factors for emergence delirium.

Nitrous oxide does not change the incidence of postoperative delirium or cognitive decline in elderly surgical patients
J. M. Leung, L. P. Sands, L. E. Vaurio and Y. Wang
British Journal of Anaesthesia 2006 96(6):754-760

Background. Postoperative delirium and cognitive decline are common in elderly surgical patients after non-cardiac surgery. Despite this prevalence and clinical importance, no specific aetiological factor has been identified for postoperative delirium and cognitive decline. In experimental setting in a rat model, nitrous oxide (N₂O) produces neurotoxic effect at high concentrations and in an age-dependent manner. Whether this neurotoxic response may be observed clinically has not been previously determined. We hypothesized that in the elderly patients undergoing non-cardiac surgery, exposure to N₂O resulted in an increased incidence of postoperative delirium than would be expected for patients not receiving N₂O.
Methods. Patients who were > 65 yr of age, undergoing non-cardiac surgery and requiring general anaesthesia were randomized to receive an inhalational agent and either N₂O with oxygen or oxygen alone. A structured interview was conducted before operation and for the first two postoperative days to determine the presence of delirium using the Confusion Assessment Method.
Results. A total of 228 patients were studied with a mean (range) age of 73.9 (65–95) yr. After operation, 43.8% of patients developed delirium. By multivariate logistic regression, age [odds ratio (OR) 1.07; 95% confidence interval (CI) 1.02–1.26], dependence on performing one or more independent activities of daily living (OR 1.54; 95% CI 1.01–2.35), use of patient-controlled analgesia for postoperative pain control (OR 3.75; 95% CI 1.27–11.01) and postoperative use of benzodiazepine (OR 2.29; 95% CI 1.21–4.36) were independently associated with an increased risk for postoperative delirium. In contrast, the use of N₂O had no association with postoperative delirium.
Conclusions. Exposure to N₂O resulted in an equal incidence of postoperative delirium when compared with no exposure to N₂O.

Emergence and recovery in children after desflurane and isoflurane anaesthesia: effect of anaesthetic duration
G. R. Nordmann, J. A. Read, S. M. Sale, P. A. Stoddart and A. R. Wolf
British Journal of Anaesthesia 2006 96(6):779-785

Background. We hypothesized that increasing duration of inhalation anaesthesia is associated with slower emergence and recovery in children, and that this effect would be less marked with desflurane in comparison with isoflurane.
Methods. Fifty-four infants and children assigned in groups according to age and expected length of operation were prospectively randomized to receive either isoflurane (I) or desflurane (D) for anaesthesia. After standard induction, the anaesthesia was maintained using an age-related 1.0 minimum alveolar concentration (MAC) equivalent for either agent in air and oxygen. Local analgesia was used as appropriate. End-tidal volatile agent concentration was recorded until extubation. Clinical evaluation of recovery was made by observers, blinded to group allocation.
Results. For patients <4 yr of age, the median (95% CI) times in minutes to first movement [5.27 (D), 9.22 (I)], eye opening [9.42(D), 13.3(I)] and extubation [7.18 (D), 12.5 (I)] were significantly shorter (P<0.05) for desflurane. In the group >4 yr of age, the median (95% CI) times in minutes to first movement [4.42 (D), 11.6 (I)], eye opening [8.55(D), 18.0(I)] and extubation [7.08 (D), 16.7 (I)] were significantly shorter (P<0.001) for desflurane. Times to leave recovery were not significantly different for the group <4 yr of age, but were significantly shorter for desflurane in the group >4 yr of age (P<0.01). The isoflurane, but not desflurane, had a time-dependent effect on arousal. There were no significant differences in incidence of airway irritation or emergence delirium between the two agents.
Conclusions. The rate of recovery in children after exposure to desflurane was faster than those patients receiving isoflurane; recovery from desflurane, but not isoflurane, was relatively unaffected by the duration of anaesthesia.

CANADIAN JOURNAL OF ANESTHESIA - TOP

Anesthesiologist-controlled versus patient-controlled propofol sedation for shockwave lithotripsy
Jamal A. Alhashemi, MBBS MSC FRCPC FCCP and Abdullah M. Kaki, MBBS FRCPC
Canadian Journal of Anesthesia 53:449-455 (2006)

Purpose: To compare anesthesiologist-controlled sedation (ACS) with patient-controlled sedation (PCS), with respect to propofol requirements, sedation, and recovery, in patients undergoing extracorporeal shockwave lithotripsy for urinary calculi.
Methods: Sixty-four patients were randomized, in this double-blind study, to receive propofol sedation according to one of two regimens: infusion of 200 µg·kg^-1 ·min^-1 for ten minutes reduced thereafter to 50–150 µg·kg^-1 ·min^-1 titrated by an anesthesiologist, according to patient response (group ACS), or propofol administered by patient-controlled analgesia (bolus dose 300 µg·kg^-1, lockout interval three minutes, no basal infusion), (group PCS). All patients received midazolam 10 µg·kg^-1 iv and fentanyl 1 µg·kg^-1 iv preoperatively, followed by fentanyl infused at a rate of 0.5 µg·kg^-1 ·hr^-1 throughout the procedure. Sedation and analgesia were assessed using the A-line ARX index and visual analogue scale, respectively. Psychomotor recovery and readiness for recovery room discharge were assessed using the Trieger dot test and postanesthesia discharge score, respectively. Patient satisfaction was assessed on a seven-point scale (1–7).
Results: In comparison to group PCS, patients in group ACS received more propofol (398 ± 162 mg vs 199 ± 68 mg, P < 0.001), were more sedated (A-line ARX index: 35 ± 16 vs 73 ± 16, P < 0.001), experienced less pain (visual analogue scale: 0 ± 0 vs 3 ± 1, P < 0.001), and were more satisfied (median [Q1, Q3]: 7 [7, 7] vs 6 [6, 7], P < 0.001). In contrast, patients in group PCS had faster psychomotor recovery (Trieger dot test median [Q1, Q3]: 8 [4, 16] vs 16 [12, 26] dots missed, P = 0.002) and achieved postanesthesia discharge score 9 earlier (median [Q1, Q3]: 40 [35, 60] vs 88 [75, 100] min, P < 0.001) compared with group ACS.
Conclusion: In comparison to PCS for patients undergoing extracorporeal shockwave lithotripsy, propofol/fentanyl ACS is associated with increased propofol administration, deeper sedation levels, and greater patient comfort. However, ACS is associated with slower recovery and a longer time to meet discharge criteria, when compared to PCS.

Preoperative gabapentin for postoperative analgesia: a meta-analysis
Rachael K. Seib, MA and James E. Paul, MD MSc FRCPC
Canadian Journal of Anesthesia 53:461-469 (2006)

Purpose: Gabapentin’s role in the treatment of chronic neuropathic pain is well known. What is less well established is its role for managing postoperative pain. In order to clarify whether gabapentin’s utility in acute pain control is more than just theoretical, we conducted a meta-analysis of all randomized trials that addressed gabapentin’s role in acute postoperative pain control. We specifically addressed whether gabapentin reduces pain scores, analgesia consumption, and/or analgesia-related side effects in the first 24 hr following surgery.
Source: We identified eight placebo-controlled, randomized controlled trials and conducted a meta-analysis using the primary outcomes of pain scores, total analgesia consumption, and side effects over a 24-hr period.
Principle findings: Patients who received gabapentin preoperatively reported significantly lower pain scores (–11.9 at rest and –11.0 with movement on a 100-point visual analogue scale) and opioid consumption (–14.7 mg of morphine in 24 hr) with no difference in the incidence of side effects.
Conclusion: Although gabapentin given preoperatively decreases pain scores and analgesic consumption in the first 24 hr after surgery, the clinical significance of this finding has yet to be determined. This meta-analysis could not demonstrate a significant reduction in the incidence of side effects. Due to the small numbers enrolled in the studies, larger randomized control trials are warranted.

PUB MED - TOP

      
Bispectral index-guided desflurane and propofol anesthesia in ambulatory arthroscopy: comparison of recovery and discharge profiles.
Camci, E., K. Koltka, et al. (2006).
J Anesth 20(2): 149-52.

In this prospective, randomized study we compared the recovery profiles of bispectral index (BIS)-guided anesthesia regimens with desflurane or propofol in ambulatory arthroscopy. Fifty ASA I-II adult patients who underwent knee arthroscopy were randomized to receive desflurane (D) or propofol (P) infusion accompanied by remifentanil and nitrous oxide during maintenance, titrated to maintain a bispectral index value between 50 and 60. Initial awakening, fast-track eligibility, and home readiness as well as intraoperative hemodynamics, were compared. The groups did not differ with respect to demographics, duration of operation, or intraoperative vital signs. Although the times for initial awakening parameters were shorter in group D, the differences between the groups were not significant. The time needed for the White fast-track score to reach 12 was shorter in group P than group D (9 +/- 3.5 min vs 12.5 +/- 5.3 min). However, home readiness did not differ significantly between the groups. Desflurane is an alternative to propofol for BIS-guided ambulatory anesthesia. Using desflurane in combination with opioid analgesics blunted its rapid emergence characteristics, and the higher frequency of emetic symptoms with desflurane diminished the success of its fast-track eligibility.            

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