MedWire News: Obese children lose consciousness at a significantly lower propofol dose than children with a healthy body mass index (BMI), shows research.
Olutoyin Olutoye and team, from Texas Children's Hospital in Houston, USA, say that the findings are consistent with those in adults showing that "administration of drugs based on the readily available total body weight can result in an exaggerated physiologic reaction as well as delayed awakening from anesthesia in the obese patient."
They say that other studies have addressed this problem by basing anesthetic drug dosing on ideal bodyweight or lean bodyweight, but methods of determining these in children are not established and often unreliable.
"Our study suggests that a simple bedside method for deciding what dose of propofol to use for induction of anesthesia in a child is to first establish the child's BMI percentile on readily available gender-specific growth charts," say Olutoye et al.
Based on their findings, an intravenous propofol dose of 2.0 mg/kg will be effective in 95% of children with a BMI above the 95th percentile for age and gender, whereas those with a lower BMI will require a higher dose of 3.2 mg/kg, they say.
The study included 40 obese children (BMI >95th percentile for age and gender) and 40 with a healthy weight (BMI 25-84th percentiles) who were scheduled for routine surgery. The first child received a low propofol starting dose of just 1.0 mg/kg. If the lash reflex remained after 20 seconds, the next child received a higher starting dose (0.25 mg/kg increments); if it was absent, the next was randomly assigned to receive the same or a lower dose.
The team found that 95.5% of the obese children lost consciousness with a propofol dose of 2.0 mg/kg. By contrast, they had to use a dose of 3.25 mg/kg to achieve the same effect in non-obese children. All non-obese children lost consciousness with this dose, but only 80% did so at the next-lowest dose tested, of 3.0 mg/kg.
The 95% confidence intervals for the required dose in the two groups did not overlap, which "suggests that obese children require significantly less propofol for loss of lash reflex than do their nonobese peers," the researchers write in Anesthesia and Analgesia.
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