Effective Dose of Propofol is lower in Obese Children
According to a recent study presented at the 2011 annual meeting of the American Society of Anesthesiologists, the effective dose of propofol in 95% of the patients (ED95) is significantly lower in obese children. This is because propofol is a lipophilic drug. More than 75 percent of the excess weight of obese children is comprised of fat tissue whereas only 25% is the actual or lean weight. The fat tissue interferes with the distribution of lipophilic drugs, like propofol. Any excess drug administered to obese children carries the risk of getting accumulated in the body for a longer period of time. This is particularly important in case of propofol, which reduces systemic vascular resistance and may lead to moderate to severe hypotension.
The research was led by Dr. Olutoyin A. Olutoye, staff anesthesiologist, Texas Children’s Hospital, Houston. The study was carried on 40 obese and 40 non-obese children between the ages of 3 and 17. The children were supposed to undergo ambulatory surgical procedures. Each child was administered 0 to 4.25 mg/kg of propofol. The research began with the lowest dose of propofol. If the next child lined up to receive the anesthetic agent failed to show loss of lash reflex (LOLR) with the dose, he received the next higher dose. In case he showed LOLR, he received the next lower dose. The researchers were able to find out the ideal dose requirement in each child through this procedure
It was seen that in obese children, the ED95 was significantly less as compared to non-obese children. It was 1.99 mg/kg in obese children compared to 3.183 mg/kg in non-obese children. Doctors also monitored the blood pressure of the children both before and after the administration of propofol. It was seen that obese children had a higher baseline blood pressure but the blood pressure dropped within two minutes of propofol administration. In case propofol is administered in doses more than required, it may lead to an exaggerated fall in blood pressure. Therefore, the researchers have opined that doctors should pay extra attention to the dose of propofol being administered to obese children.