Impact of ketamine on dynamic compliance and airway resistance of sedated and mechanically ventilated ICU patients

Effects of Ketamine Infusion on Breathing and Encephalography in Spontaneously Breathing ICU Patients

BACKGROUND

Preclinical studies suggest that ketamine stimulates breathing. We investigated whether adding a ketamine infusion at low and high doses to propofol sedation improves inspiratory flow and enhances sedation in spontaneously breathing critically ill patients.

METHODS

In this prospective interventional study, twelve intubated, spontaneously breathing patients received ketamine infusions at 5 mcg/kg/min, followed by 10 mcg/kg/min for 1 h each. Airway flow, pressure, and esophageal pressure were recorded during a spontaneous breathing trial (SBT) at baseline, and during the SBT conducted at the end of each ketamine infusion regimen. SBT consisted of one-minute breathing with zero end-expiratory pressure and no pressure support. Changes in inspiratory flow at the pre-specified time points were assessed as the primary outcome. Ketamine-induced change in beta-gamma electroencephalogram power was the key secondary endpoint. We also analyzed changes in other ventilatory parameters respiratory timing, and resistive and elastic inspiratory work of breathing.

RESULTS

Ketamine infusion of 5 and 10 mcg/kg/min increased inspiratory flow (median, IQR) from 0.36 (0.29-0.46) L/s at baseline to 0.47 (0.32-0.57) L/s and 0.44 (0.33-0.58) L/s, respectively (p = .013). Resistive work of breathing decreased from 0.4 (0.1-0.6) J/l at baseline to 0.2 (0.1-0.3) J/l after ketamine 10 mcg/kg/min (p = .042), while elastic work of breathing remained unchanged. Electroencephalogram beta-gamma power (19-44 Hz) increased compared to baseline (p < .01).

CONCLUSIONS

In intubated, spontaneously breathing patients receiving a constant rate of propofol, ketamine increased inspiratory flow, reduced inspiratory work of breathing, and was associated with an "activated" electroencephalographic pattern. These characteristics might facilitate weaning from mechanical ventilation.

Remifentanil, ketamine, and fospropofol: a review of alterative continuous infusion agents for sedation in the critically ill

Sedation and analgesia are integral aspects in the care of critically ill patients admitted to the intensive care unit. In recent years, many of the commonly used sedative agents in the United States have experienced manufacturing and sterility issues leading to decreased availability. In addition, current practice has shifted to providing lighter levels of sedation as clinicians have gained a better understanding of the consequences of prolonged deep sedation. Benzodiazepines have fallen out of favor due to findings including increased delirium and duration of mechanical ventilation. Alterations in end-organ function in critically ill patients may also lead to varied responses to commonly used sedatives. With numerous factors impacting choice of sedation in the intensive care unit, fospropofol, ketamine, and remifentanil have been considered potential alternatives to standard therapy. The purpose of this review was to discuss strategies for the safe and effective use of fospropofol, ketamine, and remifentanil for continuous intravenous sedation in critically ill patients.