Interscalene Brachial Plexus Block: Can the Risk of Entering the Spinal Canal Be Reduced?: A Study of Needle Angles in Volunteers Undergoing Magnetic Resonance Imaging.
Sardesai, Anand M. F.R.C.A. ; Patel, Roger F.R.C.R. ; Denny, Nicholas M. F.R.C.A. ; Menon, David K. F.R.C.A. ; Dixon, Adrian K. F.R.C.R. ; Herrick, Martin J. F.R.C.A. ; Harrop-Griffiths, Alan W. F.R.C.A.
Anesthesiology. 105(1):9-13, July 2006.

Background: Spinal cord damage during interscalene brachial plexus block has been attributed to needle entry into the spinal canal. The purpose of this study was to identify the angles and depths of needle insertion that increase the likelihood of such an event, using the traditional classic interscalene approach and two more proximal entry points.
Method: Magnetic resonance images of the neck from 10 healthy volunteers were used to obtain the three-dimensional spatial coordinates of three skin markers and the right-sided cervical nerves at the exiting neural foramina. The distance of the intervertebral foramina from the skin markers and the angles of the needle vector and the foramina were calculated.
Results: The distance from the skin to the intervertebral foramen may be as short as 2.5 cm with the classic approach. A caudal angulation greater than 50[degrees] seemed to eliminate the risk of needle entry through the foramen.
Conclusion: With the classic approach to the interscalene block, there is a greater possibility of the needle passing through the intervertebral foramen if the needle is advanced too deeply. More proximal entry points and techniques that use a more steeply angled needle may reduce the risk of entry into the spinal space.

Cerebral State Index during Propofol Anesthesia: A Comparison with the Bispectral Index and the A-Line ARX Index.
Jensen, Erik W. Ph.D. ; Litvan, Hector M.D., Ph.D. ; Revuelta, Miren M.D. ; Rodriguez, Bernardo E. M.Sc. ; Caminal, Pere Ph.D. ; Martinez, Pablo M.Sc. ; Vereecke,
Hugo M.D  .; Struys, Michel M. R. F. M.D., Ph.D. 
Anesthesiology. 105(1):28-36, July 2006.

Background: The objective of this study was to prospectively test the Cerebral State Index designed for measuring the depth of anesthesia. The Cerebral State Index is calculated using a fuzzy logic combination of four subparameters of the electroencephalographic signal. The performance of the Cerebral State Index was compared with that of the Bispectral Index and the A-Line ARX Index.
Methods: This study applied raw data from two previously published clinical protocols. The patients in protocol 1 were given a continuous propofol infusion, 300 ml/h, until 80% of burst suppression occurred. In protocol 2, a stepwise increased target-controlled infusion of propofol was administered to patients until loss of response to noxious stimuli while the Observer's Assessment of Alertness and Sedation was registered every 4 min. The Cerebral State Index was calculated off-line from the recorded electroencephalographic data. The Spearman rank correlation coefficient between electronic indices and the effect site concentration of propofol was calculated along with the prediction probability of each index to predict the Observer's Assessment of Alertness and Sedation level.
Results: The Spearman rank correlation coefficients between the Cerebral State Index, Bispectral Index, and A-Line ARX Index and the propofol effect site concentration were -0.94, -0.89, and -0.82, respectively, in protocol 1, whereas the prediction probability values between the Cerebral State Index, Bispectral Index, and A-Line ARX Index and the Observer's Assessment of Alertness and Sedation score in protocol 2 were 0.92, 0.93, and 0.91, respectively.
Conclusion: The Cerebral State Index detects well the graduated levels of propofol anesthesia when compared with the propofol effect site concentration and the Observer's Assessment of Alertness and Sedation score.

Naloxone Reversal of Buprenorphine-induced Respiratory Depression.
van Dorp, Eveline M.D. ; Yassen, Ashraf M.Sc. ; Sarton, Elise M.D., Ph.D. ; Romberg, Raymonda M.D., Ph.D. ; Olofsen, Erik M.Sc. ; Teppema, Luc Ph.D. ; Danhof, Meindert Ph.D.; Dahan, Albert M.D., Ph.D. 
Anesthesiology. 105(1):51-57, July 2006.

Background: The objective of this investigation was to examine the ability of the opioid antagonist naloxone to reverse respiratory depression produced by the [mu]-opioid analgesic, buprenorphine, in healthy volunteers. The studies were designed in light of the claims that buprenorphine is relatively resistant to the effects of naloxone.
Methods: In a first attempt, the effect of an intravenous bolus dose of 0.8 mg naloxone was assessed on 0.2 mg buprenorphine-induced respiratory depression. Next, the effect of increasing naloxone doses (0.5-7 mg, given over 30 min) on 0.2 mg buprenorphine-induced respiratory depression was tested. Subsequently, continuous naloxone infusions were applied to reverse respiratory depression from 0.2 and 0.4 mg buprenorphine. All doses are per 70 kg. Respiration was measured against a background of constant increased end-tidal carbon dioxide concentration.
Results: An intravenous naloxone dose of 0.8 mg had no effect on respiratory depression from buprenorphine. Increasing doses of naloxone given over 30 min produced full reversal of buprenorphine effect in the dose range of 2-4 mg naloxone. Further increasing the naloxone dose (doses of 5 mg or greater) caused a decline in reversal activity. Naloxone bolus doses of 2-3 mg, followed by a continuous infusion of 4 mg/h, caused full reversal within 40-60 min of both 0.2 and 0.4 mg buprenorphine-induced respiratory depression.
Conclusions: Reversal of buprenorphine effect is possible but depends on the buprenorphine dose and the correct naloxone dose window. Because respiratory depression from buprenorphine may outlast the effects of naloxone boluses or short infusions, a continuous infusion of naloxone may be required to maintain reversal of respiratory depression.

ACTA ANAESTHESIOLOGICA SCANDINAVICA - TOP

The effect of gabapentin on post-operative pain following tonsillectomy in adults
S. Mikkelsen, K. L. Hilsted, P. J. Andersen, N.-C. Hjortsø, T. P. Enggaard, D. G. Jørgensen, M. Hansen, J. Henriksen  and J. B. Dahl
Acta Anaesthesiologica Scandinavica Volume 50 Page 809  - August 2006

Background: The aim of the present study was to investigate whether a combination of rofecoxib and gabapentin could improve pain relief and reduce opioid requirements, compared with rofecoxib alone, during the first 5 days after tonsillectomy.
Methods: In a randomized, double-blind, placebo-controlled study, 49 patients received gabapentin 1200 mg pre-operatively, followed by gabapentin 2 × 600 mg on the day of operation and gabapentin 3 × 600 mg for the next 5 days, or placebo. Both groups were given rofecoxib 50 mg daily. In the post-operative care unit, intravenous morphine was administered in doses of 2.5 mg on request. From 4 h to 5 days post-operatively, ketobemidone was offered as escape drug. Pain at rest and during swallowing, and side-effects, were assessed using a four-point verbal rating scale.
Results: As a result of the global withdrawal of rofecoxib, the study had to be terminated prematurely. This report comprises the results from 22 patients in the gabapentin group and 27 patients in the placebo group. Gabapentin reduced ketobemidone requirements during the first 24 h post-operatively [4.5 mg (standard deviation, 3.0 mg) in the placebo group vs. 2.0 mg (standard deviation, 2.0 mg) in the gabapentin group; P < 0.003]. Gabapentin induced more dizziness (P < 0.002), gait disturbance (P < 0.02) and vomiting (P < 0.05) during days 0–5 than placebo. No other statistically significant differences were observed.
Conclusion: Gabapentin reduced opioid requirements in the first 24 h after tonsillectomy. The benefits of the reduced opioid intake may be overshadowed by the drawbacks of side-effects.

Trendelenburg positioning does not prevent a decrease in cardiac output after induction of anaesthesia with propofol in children
Kardos, C. Földesi, A. Nagy, A. Sáringer, A. Kiss, G. Kiss, P. Marschalkó and M. Szabó
Acta Anaesthesiologica Scandinavica Volume 50 Page 869  - August 2006

Background and objective: Induction of anaesthesia may cause decreased cardiac output and blood pressure. Head-down tilt is often the first clinical step to treat hypotension. The objective of this randomized single centre study was to determine, with the use of impedance cardiography (ICG), whether Trendelenburg positioning modifies the haemodynamic response to propofol/fentanyl induction of anaesthesia in ASA I children.
Methods: Thirty ASA I children aged between 7 and 16 years scheduled for elective minor orthopaedic surgery were included. After intravenous induction with propofol and fentanyl in the head-down group (HDG, n = 15), 5 min of 20° head-down tilt was applied. In the supine group (SG, n = 15), no change in the supine position was made. Heart rate (HR), mean arterial blood pressure (MABP), end-tidal carbon dioxide (ETCO2), stroke volume index (SVI), cardiac index (CI), systemic vascular resistance index (SVRI) and Heather index (HI) were recorded before (B), at 3 (A3), 5 (A5) and 8 (A8) minutes after induction in each group.
Results: After induction, a significant decrease in CI, MABP, HR and HI was recorded in both groups. In the study group, significantly lower values of HR (66 vs. 78 beat/min) and higher values of SVI (42.9 vs. 40.6 ml/min/m2) were measured at A3 compared with the control group. After induction, no difference in CI and SVRI was found between the two groups.
Conclusion: The present study shows that cardiac performance is not improved by Trendelenburg positioning after propofol/fentanyl induction of anaesthesia in children.

The former preterm infant and risk of post-operative apnoea: recommendations for management
S. Walther-Larsen  and L. S. Rasmussen
Acta Anaesthesiologica Scandinavica Volume 50 Page 888  - August 2006

The preterm infant presenting for anaesthesia during the first 6 months of life is a major anaesthetic challenge. One of the most serious post-operative complications is apnoea with or without bradycardia. For this review, we conducted a search of the current literature in order to formulate a set of evidence-based clinical guidelines to help clinicians in the management of the former preterm infant to avoid post-operative apnoea. Only a small number of patients have been enrolled into prospective, randomized, controlled studies. Based on the current literature, regional anaesthesia is strongly recommended, preferably neuraxial block, but general anaesthesia is also used and in this setting, opioids and muscle relaxants should be avoided. Infants with a post-conceptual age of less than 46 weeks should be admitted for continuous monitoring for at least 12 h post-operatively. In infants with a post-conceptual age (PCA) between 46 and 60 weeks, a careful assessment of the child is mandatory and 12 h of respiratory monitoring is recommended if the patient's history reveals episodes of apnoea at home, chronic lung disease (CLD), neurological disease or anaemia. The otherwise healthy infant could be scheduled for theatre as the first patient on the list and subsequently monitored in the post-anaesthetic care unit for 6 h. The risk of apnoea in former preterm infants can be further reduced by the administration of intravenous caffeine (10 mg/kg). All of these patients should be referred to a tertiary centre for anaesthesia and surgery.

BRITISH JOURNAL OF ANAESTHESIA - TOP

Neostigmine-induced reversal of vecuronium in normal weight, overweight and obese female patients
T. Suzuki, G. Masaki and S. Ogawa
British Journal of Anaesthesia 2006 97(2):160-163

Background. The purpose of this study was to compare neostigmine-induced reversal of vecuronium in normal weight, overweight and obese female patients.
Methods. In total, 15 each of normal weight (18.5<=BMI<25), overweight (25<=BMI<30) and obese (BMI30) patients were enrolled. Anaesthesia was induced and maintained with fentanyl, propofol and nitrous oxide. Neuromuscular block was induced with vecuronium 0.1 mg kg–1 on the basis of the patient's real body weight (RBW) and was monitored using acceleromyographic train-of-four (TOF) of the adductor pollicis. All patients received neostigmine 0.04 mg kg–1 combined with atropine 0.02 mg kg–1 at 25% recovery of the first twitch (T1) of TOF and were allowed to recover to a TOF ratio of 0.9.
Results. The time from administration of vecuronium to spontaneous recovery of T1 to 25% of control was significantly longer in the obese [mean (SD, range); 68.4 (16.3, 39.8–110.8) min] and the overweight groups [49.3 (6.2, 39.8–60.8) min] as compared with the normal weight group [41.0 (9.0, 27.5–59.5) min]. The times for facilitated recovery with neostigmine to a TOF ratio of 0.7 did not differ among groups. However, the recovery to a TOF ratio of 0.9 in the obese [25.9 (6.7, 13.5–41.0) min] and the overweight groups [14.6 (7.7, 3.3–28.5) min] were significantly longer than that in the normal weight group [6.9 (2.0, 3.0–10.7) min].
Conclusions. Early reversal after neostigmine is prompt; however, recovery to a TOF ratio of 0.9 is slow in overweight and obese patients when vecuronium is dosed on the basis of the patient's RBW.

Skin conductance monitoring compared with bispectral index® monitoring to assess emergence from general anaesthesia using sevoflurane and remifentanil
T. Ledowski, M. J. Paech, H. Storm, R. Jones and S. A. Schug
British Journal of Anaesthesia 2006 97(2):187-191

Background. Changes in skin conductance have previously been reported to correlate well with plasma levels of stress hormones and awakening stimuli. In this study, monitoring of skin conductance during emergence from general anaesthesia was compared with the monitoring of bispectral index (BIS).
Methods. Twenty-five patients undergoing minor elective surgery were investigated. The number of fluctuations in mean skin conductance (NFSC), BIS and haemodynamic parameters were recorded simultaneously. The performance of the monitoring devices to predict and distinguish between the clinical states ‘steady-state anaesthesia’, ‘first reaction’ and ‘extubation’ were compared using the method of prediction probability (PK) calculation.
Results. Both monitors showed similar performance in distinguishing between ‘steady-state anaesthesia’ vs ‘first reaction’ (PK NFSC 0.89; BIS® 0.94) and ‘steady-state anaesthesia’ vs ‘extubation’ (PK NFSC 0.96; BIS® 0.96). The response times of the monitors, to indicate the likelihood of ‘first reaction’, were not significantly different.
Conclusions. NFSC, as a parameter of skin conductance, performed similarly to BIS in patients waking after a general anaesthetic.

The effect of melatonin on sedation of children undergoing magnetic resonance imaging
M. R. J. Sury and K. Fairweather
British Journal of Anaesthesia 2006 97(2):220-225 

Background. Melatonin may induce a natural sleepiness and improve predictability of sedation drugs. We have investigated its clinical value in children sedated for magnetic resonance imaging.
Methods. In a stratified randomized double-blind study, 98 children received either melatonin or placebo 10 min before they were sedated with a standard oral regimen. Children >5 and <15 kg received chloral hydrate and those 15 and <40 kg had a combination of temazepam with droperidol (T&D). The doses of melatonin were 3 and 6 mg, respectively. One observer recorded the time taken to reach criteria for deep sedation, sedation failure and other sedation-related events.
Results. In the chloral hydrate group (n=50) 50% were deeply sedated by 31 min after melatonin and 40 min after placebo (P=0.57). There were zero and 1 failures, respectively. The geometric mean time taken to reach deep sedation was 39 min in both subgroups. In the T&D group (n=48) 50% were deeply sedated by 70 min in both subgroups (two failures in each); geometric mean times were 68 and 71 min, respectively (P=0.58). Children closed their eyes slightly earlier after melatonin (respective geometric means 42 vs 48, P=0.17), and took slightly longer to achieve discharge criteria (146 vs 135, P=0.47).
Conclusion. In these doses and clinical conditions, melatonin did not contribute to sedation of children.

CANADIAN JOURNAL OF ANESTHESIA - TOP

Evidence-based clinical update: General anesthesia and the risk of delirium and postoperative cognitive dysfunction
Gregory L. Bryson, FRCPC MSc and Anna Wyand, MD
Canadian Journal of Anesthesia 53:669-677 (2006)

Purpose: The purpose of this structured, evidence-based, clinical update was to identify the best evidence comparing general and regional anesthesia and their influence on delirium or cognitive dysfunction (POCD) in the postoperative period.
Source: In June 2005 a structured search of MEDLINE from 1966 to present using OVID software was undertaken. Medical subject headings and textwords describing both delirium and POCD were employed. OVID’s Therapy (sensitivity) algorithm was used to maximize the detection of randomized trials. The bibliographies of eligible publications were hand-searched to identify trials not identified in the electronic search. Publications enrolling children were excluded. Levels of evidence and grades of recommendations were scored using Centre for Evidence Based Medicine criteria.
Principal findings: A total of 18 unique randomized controlled trials were identified: two evaluating delirium; ten evaluating POCD; and six evaluating both. Outcomes for delirium were abstracted from eight trials that enrolled 765 patients (387 regional anesthesia; 378 general anesthesia). Outcomes for POCD were identified from 16 trials that enrolled 2,708 patients (1,313 regional anesthesia; 1,395 general anesthesia). Both delirium (11–43%) and POCD (15–25%) were relatively common in trials actively seeking these outcomes. Consistent Level 2b evidence suggests no significant increase in delirium in patients receiving general anesthesia compared with those receiving regional anesthesia. Similarly, consistent Level 1 evidence indicates that exposure to general anesthesia is not significantly associated with POCD.
Conclusion: Available randomized controlled trials suggest that there is no significant difference in the incidence of delirium or POCD when general anesthesia and regional anesthesia are compared.

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