Efficacy of ketamine in Australia ventilated intensive care unit admissions by Tom Niccol

Efficacy of ketamine in Australia mechanically ventilated intensive care unit patients with Tom Niccol: In Australian and New Zealand, mechanically ventilated patients account for about 35% of all adult patients admitted to the intensive care unit (ICU). In addition to treating the primary illness, international clinical practice guidelines emphasise five critical domains in the management of ventilated patients. These are pain assessment and management, sedation and agitation prevention, delirium assessment and treatment, rehabilitation and mobilisation, and minimising sleep disruption. Read more details on https://www.facebook.com/tom.niccol/.

Mechanically ventilated patients account for about one-third of all admissions to the intensive care unit (ICU). Ketamine has been conditionally recommended to aid with analgesia in such patients, with low quality of evidence available to support this recommendation. We aimed to perform a narrative scoping review of the current knowledge of the use of ketamine, with a specific focus on mechanically ventilated ICU patients.

One study compared an S-ketamine anaesthesia of a bolus of 1–3 mg/kg followed by infusion of 2–4 mg/kg/h versus sufentanil infusion. Five of the studies reported that racemic or S-ketamine reduced the inflammatory response after surgery as measured by plasma/serum IL-6 concentrations. This response was most pronounced in the early (within 6 hours) postoperative period. It is possible that this anti-inflammatory effect of ketamine may provide some benefit to mechanically ventilated ICU patients.

Methods: We searched MEDLINE and EMBASE for relevant articles. Bibliographies of retrieved articles were examined for references of potential relevance. We included studies that described the use of ketamine for postoperative and emergency department management of pain and in the critically unwell, mechanically ventilated population.

Although the intravenous dose required for induction of anaesthesia has been reported to be 1–4.5 mg/kg, a commonly recommended dose regime is 1.0 mg/kg followed by repeated boluses of 0.5–1.0 mg/kg if initial sedation is inadequate. A recommended dose for analgesia is an intravenous infusion of 0.27–0.75 mg/kg/h. Low dose ketamine when given as an intravenous bolus for acute postoperative pain has been defined as a subanaesthetic dose or < 1 mg/kg. Low dose ketamine, when given as an infusion, is less well defined. One review defined low dose infusion as ≤ 0.2 mg/kg/h. Alternatively, subdissociative dosing of 0.1–0.4 mg/kg/h has also been described as low dose.

Results: There are few randomised controlled trials evaluating ketamine's utility in the ICU. The evidence is predominantly retrospective and observational in nature and the results are heterogeneous. Available evidence is summarised in a descriptive manner, with a division made between high dose and low dose ketamine. Ketamine's pharmacology and use as an analgesic agent outside of the ICU is briefly discussed, followed by evidence for use in the ICU setting, with particular emphasis on analgesia, sedation and intubation. Finally, data on adverse effects including delirium, coma, haemodynamic adverse effects, raised intracranial pressure, hypersalivation and laryngospasm are presented.

High dose. There are four studies that examine the effect of ketamine infusion on ICPs. Kolenda et al, Bourgoin et al and Schmittner et al are described in Table 2. The fourth study, also by Bourgoin and colleagues, was a single-centre randomised controlled trial of 30 patients with severe traumatic brain injury which compared ketamine with sufentanil as target-controlled infusions for sedation. Both groups also received midazolam. Target plasma concentrations of ketamine and sufentanil were set and efficacy of sedation assessed. The patients had a mean age of 29 ± 11 years and 29 ± 12 years for ketamine and sufentanil respectively. Plasma concentrations were targeted and doses were not reported.

Conclusions: Ketamine is used in mechanically ventilated ICU patients with several potentially positive clinical effects. However, it has a significant side effect profile, which may limit its use in these patients. The role of low dose ketamine infusion in mechanically ventilated ICU patients is not well studied and requires investigation in high quality, prospective randomised trials.