Optimal propofol induction dose in morbidly obese patients: A randomized controlled trial comparing the bispectral index and lean body weight scalar

  • Yamini Subramani
  • Waleed Riad
  • Frances Chung
  • Jean Wong
Reports of Original Investigations



Propofol dosing based on total body weight (TBW) can lead to overdosing in morbidly obese (MO) patients. Our aim was to determine whether an induction dose of propofol based on a bispectral index (BIS) target is better for achieving loss of consciousness in MO patients than dosing based on lean body weight (LBW).


Sixty MO patients with a body mass index (BMI) of ≥ 40 kg·m−2 were randomized to either BIS- or LBW-based propofol dosing groups. Anesthesia was induced with a propofol infusion of 100 mg·kg−1·hr−1 to an initial target endpoint of a BIS of 50 (BIS group) or until a precalculated dose of 2.6 mg·kg−1 LBW based on the Janmahasatian equation was administered (LBW group). Induction was assessed using the observer’s assessment alertness/sedation scale (OAA/S). If an OAA/S score of 0 was not achieved, infusions continued until it reached 0. The groups were compared for the primary outcome which was the difference in the propofol doses at the initial target endpoint.


The median [interquartile range] OAA/S score at the initial target endpoint was lower in the BIS group than in the LBW group (0 [0-0] vs 1 [0-3], respectively; median difference 1, 95% confidence interval [CI] 0 to 3; P = 0.001). The number of patients requiring additional propofol doses was also higher for the LBW group [1 vs 18 patients, respectively; relative risk of requiring additional propofol 18; 95% CI 3 to 126; P = 0.001]. The mean (SD) propofol dose at the target endpoint was significantly lower in the LBW group than in the BIS group [164 (36) mg vs 225 (44) mg, respectively; mean difference 61 mg; 95% CI 41 to 83 mg; P = 0.002]. There was no difference between the two groups, however, regarding the total induction dose of propofol needed for the OAA/S to reach 0 (P = 0.07).


The induction dose of propofol based on the BIS index was different from the induction dose based on LBW in MO patients. Patients in the LBW group required additional propofol to achieve an OAA/S of 0.

Posologie optimale de propofol pour l’induction des patients obèses morbides: une étude randomisée contrôlée comparant l’indice bispectral et une échelle de poids idéal



Le dosage du propofol en fonction du poids corporel total (PCT) peut entraîner un surdosage chez les patients obèses morbides. Notre objectif était de déterminer si une dose d’induction de propofol fondée sur une cible d’indice bispectral (BIS) était plus adaptée pour obtenir une perte de conscience chez les patients obèses morbides qu’une posologie fondée sur le poids idéal.


Soixante patients obèses morbides avec un indice de masse corporel (IMC) ≥ 40 kg·m−2 ont été randomisés en groupes posologiques de propofol fondés sur le BIS ou le poids idéal. L’anesthésie a été induite à l’aide d’une perfusion de propofol de 100 mg·kg−1·h−1 jusqu’à une cible initiale de BIS de 50 (groupe BIS) ou jusqu’à ce qu’une dose pré-calculée de 2,6 mg·kg−1 de poids idéal, fondée sur la formule de Janmahasatian, soit administrée (groupe poids idéal). L’induction a été évaluée selon l’échelle de sédation OAA/S (Observer’s Assessment Alertness/Sedation Scale). Si un score de 0 sur l’échelle OAA/S n’était pas obtenu, les perfusions étaient poursuivies jusqu’à l’obtention de cette valeur. Les groupes ont été comparés par rapport au critère d’évaluation principal, soit la différence entre les doses de propofol au critère d’évaluation initial.


Le score OAA/S médian [écart interquartile] au critère d’évaluation initial était plus bas dans le groupe BIS que dans le groupe poids idéal (0 [0-0] vs 1 [0-3], respectivement; différence médiane 1, intervalle de confiance [IC] 95 % 0 à 3; P = 0,001). Le nombre de patients nécessitant des doses supplémentaires de propofol était également plus élevé dans le groupe poids idéal [1 vs 18 patients, respectivement; risque relatif d’avoir besoin de propofol supplémentaire 18; IC 95 % 3 à 126; P = 0,001]. La dose moyenne (ÉT) de propofol au critère d’évaluation initial était significativement plus basse dans le groupe poids idéal que dans le groupe BIS [164 (36) mg vs 225 (44) mg, respectivement; différence moyenne 61 mg; IC 95 % 41 à 83 mg; P = 0,002]. Aucune différence n’a toutefois été observée entre les deux groupes quant à la dose d’induction totale de propofol nécessaire pour que l’échelle OAA/S atteigne 0 (P = 0,07).


La dose d’induction de propofol fondée sur l’indice BIS était différente de celle fondée sur le poids idéal chez les patients obèses morbides. Les patients du groupe poids idéal ont eu besoin de plus de propofol pour atteindre un score de 0 sur l’échelle OAA/S.


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Copyright information

© Canadian Anesthesiologists' Society 2017

Authors and Affiliations

  • Yamini Subramani
    • 1
  • Waleed Riad
    • 2
  • Frances Chung
    • 1
  • Jean Wong
    • 1
  1. 1.Department of Anesthesia, Toronto Western HospitalUniversity Health NetworkTorontoCanada
  2. 2.Department of AnesthesiaCorniche HospitalAbu DhabiUnited Arab Emirates

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