Ketamine and midazolam mixture versus ketamine for analgesia/sedation in polytrauma patients with asthma

Introduction

Ketamine and midazolam are among the most frequently used anesthetic agents. The other area of application is ICU. Bronchodilating properties of ketamine are well established. Unfortunately, ketamine exerts some side effects. Many researchers use benzodiazepines to cover these undesirable effects.

Study design

A prospective controlled study.

Setting

A general ICU.

Objective

To prove efficacy of ketamine and midazolam as an alternative for analgesia/sedation in asthma patients after polytrauma.

Methods

Using a model of Jahangir and colleagues [1], 14 patients with multiple injuries and history of asthma were included during their ICU stay (nine spontaneously breathing, five mechanically ventilated). Patients were randomised into two groups. Group 1 patients received an infusion of ketamine and midazolam. The two drugs were mixed in one syringe (50 mg ketamine and 5 mg midazolam). The mean rate of infusion for ketamine was 150–250 ng/kg/hour and for midazolam was 0.015–0.03 ng/kg/hour. Midazolam was added to eliminate the side effects of ketamine and for sedation. Group 2 patients received an infusion of ketamine only (0.2–0.4 mg/kg/hour). The following parameters of haemodynamics and ventilation were monitored: heart rate, mean arterial pressure, respiratory rate, arterial and end-expiratory PO₂, arterial PO₂, transcutaneous oxygen saturation SpO₂, pulmonary compliance and resistance (in ventilated patients), and subjective perception of pain using the visual analogue scale (VAS 1–10 points), Ramsey sedation scale (wake and sleep levels), and rate of appearance of side effects. Ketamine in a mixture with midazolam led to insignificant changes in hemodynamics and only in group 2 patients were more significant changes noted (tachycardia and mild hypertension). Respiratory function remained well maintained except in some group 2 patients, where mild hyperventilation was noted. We documented an increase in respiratory compliance and a reduction in pulmonary resistance. Midazolam helped to prevent side effects after ketamine administration but after prolonged infusion of midazolam there were signs of an accumulation and an increase in doses was necessary. The VAS score (between 1 and 6) was almost similar in both groups. The Ramsey scale score was also similar (conscious level 3) but with some cases of agitation in group 2 patients.

Conclusions

Ketamine and midazolam as a mixture are a good alternative for analgesia/sedation in patients with asthma after multiple injuries. We consider higher doses are needed for better patient comfort.