Ketamine in the Critically Ill: Our Experience of 36 Cases

INTRODUCTION: Ketamine has emerged as a novel drug for sedation in TBI patients, owing to its neuroprotective effects. A potent analgesic, with dissociative and sedative properties, ketamine has antiseizure activity, as well as it causes little change in CO(2) reactivity of intracranial pressure. Overall, it maintains cerebral perfusion pressure, while reducing cerebral metabolism, thus reinstating flow metabolism coupling to some extent. It produces sedation, amnesia and analgesia, while preserving respiratory effort, cardiovascular stability and airway reflexes. These qualities are in addition to low cost, wide availability, and a large therapeutic window. Here we present our experience of 36 cases of use of ketamine in critically ill patients admitted to our trauma intensive care unit, as part of a pilot study. METHODOLOGY: All critically ill patients aged 18–65 years admitted to the trauma intensive care unit requiring invasive mechanical ventilation were assessed for eligibility. Patients with a high sympathetic drive, shock index more than 1.0, or severe septic shock requiring more than one inotropic support were excluded. We included patients with moderate to severe traumatic brain injury, patients with history of asthma or chronic obstructive airway disease, and history of seizures requiring two or more antiepileptic drugs, among other patients fulfilling the eligibility criteria. Patients were assessed for hemodynamic changes(tachycardia, bradycardia, hypotension, hypertension), incidence of ventilator associated pneumonia, duration of mechanical ventilation and side effects like nausea, vomiting and hallucinations. Time to achieve goal RASS and time spent in goal RASS were also assessed. In addition, TBI patients underwent ICP monitoring, with an emphasis on monitoring the cerebral perfusion pressures, any signs of neuroworsening, and any need to change the established sedation regimen. RESULTS: Twenty of the thirty six patients had moderate to severe head injury requiring invasive mechanical ventilation for ICP control. Of these, eleven patients had a Marshall CT score of 2 and higher. Mean opening ICP was 26±3 mmHg among the head injured. ICP excursion with worsening NCCT findings was noted in two out of twenty patients, warranting decompressive hemicraniectomy. Two patients required change in sedation regimen owing to hypertension and tachycardia associated with rise in ICP of more than 5 mm Hg from baseline. No patients required inotropic support to maintain cerebral perfusion pressures. Of the 36 patients, five had a history of chronic smoking, three were known asthmatics on regular medication, while two patients had refractory bronchospasm on invasive mechanical ventilation not responding to other threrapies. Four patients had history of seizure disorder and required two antiepileptic agents for seizure control. Mean mechanically ventilated days were 4±1.8. Mean time taken to achieve goal RASS was 42±2.4 minutes. Time spent in goal RASS was 3±0.9 days. Two patients had hypertension significant to warrant change in sedation regime, while three patients had significant tachycardia, which settled with titration of drug. Three patients had nausea and vomiting which settled with ondansetron. No dangerous side effects were noted. CONCLUSION: Ketamine appeared to have beneficial effects on cerebral hemodynamics. Additionally, ketamine appeared to have a favorable safety profile in our patient population without significant effects on hemodynamics and agitation.