Abstract

BACKGROUND
While the combination therapy of morphine and benzodiazepine has been recommended as a standard therapy for sedation and analgesia in patients with mechanical ventilation, morphine can suppress respiratory center, and also decrease blood pressure and bowel movement. Because ketamine has analgesic and sedative effects compatible to morphine without depression of the cardiovascular and respiratory systems in addition to the preservation of bowel activity, ketamine may substitute morphine. However, it has not well known such potential advantages of ketamine in patients with mechanical ventilation.
METHODS
Thirty eight patients (male:female=30:8, age=62.6 +/- 11.7 years) with mechanical ventilation were randomized as ketamine and morphine group (n=21 vs. n=17). There was no significant differences in sex, age and APACHE III score at the initiation of mechanical ventilation (ketamine group, morphine group: 79.4 +/- 2.0, 82.0 +/- 20.6). The study duration was 24 h after drug administration and minimum dose, which maintains ventilator-patient synchrony or the status of Ramsay score 3, was used. Ramsay sedation score, hemodynamic variables, respiratory and arterial blood gas variables, and bowel sound were measured at every 4 h. Arterial blood gas analysis was checked at 0, 4, and 24 h.
RESULTS
1) There were no significant differences in Ramsay sedation score and other hemodynamic, respiratory, and arterial blood gas variables in each group. The dose of combined midazolam was not different between two groups (ketamine vs. morphine; 52.1 +/- 11.9 vs. 46.7 +/- 15.1 mg/d; p=0.23). 2) The cases with decreased mean arterial pressure over 25% of the baseline shortly after the drug administration less frequently observed in ketamine group, although the difference did not reach statistical significance (n=2, 9.5% vs. n=5, 29.4%; p=0.12). 3) Bowel movement reduction at 4 h after the drug administration was less in ketamine group (n=1, 4.8% vs. n=6, 35.3%, p=0.03). The difference was not observed at 8 h. 4) Cost of the drug for 24 h was more expensive in ketamine group (dose & cost; 688 506 mg/d & 25,891 7,743 won vs. 40 +/- 18 mg/d, 15,814 +/- 4,853 won; p<0.001).
CONCLUSIONS
Considering the advantages in the hemodynamics and bowel movement, ketamine may substitute morphine for the sedation of patients with mechanical ventilation, if indicated.

• Keywords: Ketamine;Morphine;Mechanical ventilation;Sedation;