Ketamine for procedural pain relief in newborn infants

Aim-To assess the suitability of ketamine for relief of pain caused by tracheal suction during ventilator treatment in newborn infants. Study design-In a randomised, double blind, cross over trial, 16 newborn infants received placebo or 0,5, 1, or 2 mg/kg ketamine as two minute infusions in random order five minutes before four separate endotracheal suctions, with intervals of at least 12 hours. Results-Mean (SD) plasma ketamine concentration increased linearly with the dose (103 (49), 189 (75), and 379 (97) ng/ml after 0.5, 1, and 2 mg/kg respectively). Heart rate decreased significantly only after 2 mg/kg ketamine (-7 (10) beats/min, p = 0.029 v placebo). The increases in heart rate, arterial blood pressure, and pain score in response to tracheal suction during the placebo phase (11 (23) beats/ min, p = 0.065; 6 (7) mm Hg, p = 0.004; 3.5 (interquartile range (IQR) 2.75-5) points, p = 0.001) were not attenuated by 0.5 or 2 mg/kg ketamine. However, 1 mg/kg ketamine attenuated the increase in pain score (1 (IQR 0.75-4.25) points, p = 0.043 v placebo), but not in heart rate (7 (23) beats/min) or blood pressure (7 (9) mm Hg). Conclusion-None of the doses of ketamine attenuated the changes in heart rate or blood pressure caused by suction, and only with a dose of 1 mg/kg was the suction induced pain moderately reduced. Thus infusion of ketamine at the doses used appears to be an ineffective method of relieving the pain caused by endotracheal suction.