Are Estimates of MAC Reliable?

Paul, Matthias; Fisher, Dennis M.

doi:10.1097/00000542-200112000-00014

Cited by 116 publications

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“…Paul et al noted that if the initial sevoflurane value deviated greatly from the population MAC, a larger sample size was required in order to obtain the desired number of crossovers. 10 The opposite was observed in our study. For example, the initial sevoflurane value used for Group A was 2.4% and the mean MAC sevoflurane was calculated to be 2.39 ± 0.58% (Table).…”

Section: Discussioncontrasting

confidence: 82%

“…Similarly, using starting concentrations less than the population MAC yields values for mean MAC less than population MAC. 10 This source of error was unavoidable given that the effect of remifentanil on sevoflurane MAC in pediatric patients has not been studied previously and other than our own data, there was little information to guide us in determining starting sevoflurane concentrations. In using starting end-tidal sevoflurane concentrations FIGURE 2 The mean sevoflurane concentration required to prevent movement response to surgical incision in test subjects at varying infusion rates of remifentanil.…”

Section: Discussionmentioning

confidence: 84%

“…13,14 According to Paul et al, this method of determining the initial sevoflurane concentration may have introduced a bias toward the calculated mean MAC sevoflurane value. 10 They have shown that using starting concentrations larger than population MAC yields average results for mean MAC slightly greater than population MAC. Similarly, using starting concentrations less than the population MAC yields values for mean MAC less than population MAC.…”

Section: Discussionmentioning

confidence: 99%

“…10 When this study design is used, inter-individual variability of MAC is set to 20%, and four to six crossovers are used for calculation, the SD of mean MAC is typically 11%. 10 In our study, the mean MAC sevoflurane SD was 24% (five crossovers), 19% (four crossovers), and 12% (five crossovers) respectively for the 0.03 µg·kg -1 ·min -1 , 0.06 µg·kg -1 ·min -1 , and 0.12 µg·kg -1 ·min -1 groups. Paul et al have shown that the SD of mean MAC values is minimized with the use of six crossovers yet, the mean MAC value obtained using four crossovers is the same as that obtained when a greater number than four crossovers are used.…”

Section: Discussionmentioning

confidence: 99%

“…Our sample size was determined by the number of patients required in order to observe a minimum of four crossovers for each dose of remifentanil. 10 Once the response was recorded, further administration of anesthetic and analgesic agents was at the attending anesthesiologist's discretion.…”

Section: Methodsmentioning

confidence: 99%

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Remifentanil decreases sevoflurane requirements in children

Castanelli

Splinter

Clavel

2005

Can J Anesth/J Can Anesth

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Purpose:To establish the effect of increasing concentrations of remifentanil on sevoflurane requirements in children.Methods: Fifty-eight healthy patients, ASA status I-II aged two to 12 yr, undergoing abdominal wall hernia or hydrocele repairs were serially assigned to one of four test groups to receive remifentanil 0.03 µg·kg -1 ·min -1 , 0.06 µg·kg -1 ·min -1 , 0.12 µg·kg -1 ·min -1 , or 0.25 µg·kg -1 ·min -1 iv. Patients received a bolus of remifentanil 1 µg·kg -1 iv before the infusion began. End-tidal sevoflurane concentration was adjusted according to a Dixon up-and-down approach. Ten minutes after starting the remifentanil infusion, the surgical incision was made. The patient was observed for one minute from the time of incision by a solitary blinded rater for either flexion or withdrawal of one or more extremities in response to skin incision. Results:The mean minimum alveolar concentration of sevoflurane was 2.39 ± 0.58 with 0.03 µg·kg -1 ·min -1 remifentanil, 1.91 ± 0.36 with 0.06 µg·kg -1 ·min -1 remifentanil, and 0.92 ± 0.11 with 0.12 µg·kg -1 ·min -1 remifentanil. Remifentanil 0.25 µg·kg -1 ·min -1 lead to the sevoflurane being decreased to a level associated with spontaneous patient awakening.The effective dose (ED 50 ) values of sevoflurane were 2.44 [95% confidence interval (CI) 2.16-2.72], 2.00 (95% CI 1.78-2.22), and 1.18 (95% CI 0.99-1.36) for remifentanil infusion rates of 0.03 µg·kg -1 ·min -1 , 0.06 µg·kg -1 ·min -1 , and 0.12 µg·kg -1 ·min -1 respectively. Conclusion:The administration of remifentanil produced a dose-dependent decrease in the minimum alveolar concentration of sevoflurane necessary for inhibition of movement reaction in response to surgical incision. The use of remifentanil may allow for flexible analgesic control and rapid recovery in children anesthetized with sevoflurane. (IC de 95 % 1,22) et 1,18 (IC de 95 % 0,36) Objectif

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Section: Discussioncontrasting

confidence: 82%

Section: Discussionmentioning

confidence: 84%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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Remifentanil decreases sevoflurane requirements in children

Castanelli

Splinter

Clavel

2005

Can J Anesth/J Can Anesth

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Sitting position does not alter minimum alveolar concentration for desflurane

Lin

Lee

et al. 2007

Can J Anesth/J Can Anesth

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Purpose: Hypotension is a common complication of the sitting position during anesthesia, and is often counteracted by decreasing anesthetic depth, thereby exposing patients to the risk of being inadequately anesthetized. Baroreceptor unloading and the consequent sympathoexcitation, as during head up tilt, decreases pain threshold and arouses the central nervous system (CNS), whereas hypotension exerts a direct CNS depressant effect. We estimated the minimal alveolar concentration (MAC) of desflurane for immobility in patients undergoing surgery in the sitting position, in comparison to MAC desflurane for patients having a similar type of surgery in the supine position. Methods:The Dixon up-and-down method was used to evaluate the MAC for desflurane in patients undergoing cervical spine laminoplasty (n = 24) or discectomy (n = 24) in the sitting and supine positions, respectively. Logistic regression with co-variate adjustment was employed to examine if the two positions (sitting and supine) have different or share the same concentration vs response relationship for immobility. Monte Carlo simulation was used to calculate 95% confidence intervals (CI) for the MAC in each position, and to estimate the difference in MAC (delta MAC) between the sitting and supine positions. Results:Modeling both sitting [6.54% (6.50-6.66, 95% CI)] and supine [6.70 (6.55-6.81)] patients as having different MAC concentrations did not significantly improve our simplified model, which treats the two patient groups as one [6.61 (6.52-6.70), delta -2 log likelihood = 2.735, P = 0.098]. Mean delta MAC (95% CI) was -0.14 (-0.30, 0.03). Conclusion:The sitting position does not change desflurane anesthetic requirements for immobility. [6,54 % (6,66, 95 % IC)] et ceux en décubitus dorsal [6,70 (6,55-6,81)] présentent des concentrations MAC différentes, n'a pas amélioré de façon significative notre modèle simplifié, lequel considère les deux groupes de patients en tant qu'un seul groupe [6,61 (6,52-6,70), delta -2 logarithme du rapport de vraisemblance = 2,735, P = 0,098]. 30, 0,03). REPORTS OF ORIGINAL INVESTIGATIONS 523CAN J ANESTH 54: 7 www.cja-jca

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Analgesie unter der Geburt

Mc¹

2002

Der Anaesthesist

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Peripartum care of parturients has contributed a great deal to the development of modern anaesthesia during the past 150 years. The introduction of general and regional anaesthesia provided new options of relieving pain during delivery and preventing suffering. However,provision of effective labor analgesia gave and still gives rise to controversy as to whether interfering with natural events such as delivery was justifiable on a religious,moral or ideological level. A new era of obstetric pain relief was initiated when a study design was devised to define the Minimum Local Analgesic Concentration (MLAC) needed for epidural analgesia. Using the MLAC model as a scientifically based pharmacodynamic measure of analgesia, empirically developed "recipes" can be compared and validated. The importance of this clinical model will be put into a pharmacological context including issues such as the up-down sequential allocation technique, dose-response curves and differential nerve blockade.

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Are Estimates of MAC Reliable?

Abstract: Individual experiments may yield inaccurate MAC estimates. This inaccuracy is minimized as the number of crossovers increases; however, improvement diminishes as the number of crossovers exceeds six.

Cited by 116 publications

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Remifentanil decreases sevoflurane requirements in children

Remifentanil decreases sevoflurane requirements in children

Sitting position does not alter minimum alveolar concentration for desflurane

Analgesie unter der Geburt

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