Background: Ketamine is commonly used in children in the emergency setting and while undergoing diagnostic and therapeutic interventions because of its combination of hypnotic and analgesic properties. Although studies comparing various levels of ketamine anesthesia are lacking, previous work suggests that lung mechanics might only be minimally affected by ketamine.
Methods: After approval from the Ethics Committee, anesthesia was induced with 2 mg.kg(-1) racemic ketamine followed by a continuous infusion of ketamine 2 mg.kg(-1) h(-1) (level I) in 26 children (2-6 years of age), and after 5 min, the first set of measurements was performed. Then, a second bolus of ketamine 2 mg.kg(-1) followed by ketamine 4 mg.kg(-1) h(-1) was administered (level II) and after 5 min, the second set of measurements was performed. Functional residual capacity (FRC) and lung clearance index (LCI) were calculated using a multibreath analysis by a blinded observer.
Results: Functional residual capacity and LCI did not change between the two levels (FRC 25.6 [4.3] ml.kg(-1) vs 25.5 [4.2] ml.kg(-1), P=0.769, LCI 10.5 [1.2] vs 10.3 [1.1], P=0.403). The minute ventilation was similar between the two levels of anesthesia. The University of Michigan Sedation Scale increased from 3 (3) to 4 (3-4) at the second level of ketamine anesthesia.
Conclusions: A deeper level of anesthesia induced by ketamine does not affect FRC, ventilation distribution or minute ventilation suggesting that the depth of ketamine anesthesia has a minimal effect on pulmonary function.