Inhalative sedation with small tidal volumes under venovenous ECMO.

BACKGROUND

Inhalative sedation is an emerging method for long-term sedation in intensive care therapy. There is evidence that it is easy to control and may be beneficial compared to intravenous sedation. Yet little is known about the use in patients with compromised lung function. In this retrospective analysis, we searched files of patients receiving inhalative sedation under venovenous extracorporeal membrane oxygenator (vv-ECMO) support due to lung failure.

METHODS

After ethical approval, we performed a retrospective analysis of patients receiving vv-ECMO support and inhalative sedation in the surgical ICU in 2015. Isoflurane was administered via the AnaConDa®-system. Sedation was tested using Richmond Agitation and Sedation scale (RASS).

RESULTS

7 patients were identified. Median age was 50 years (26/70 years). All were male. Median ECMO runtime was 129 h (37/1008 h) and the survival rate was 57.9%. Dose of isoflurane was 1.7 ml/h (0.8 / 4.0 ml/h) resulting in expiratory concentrations of 0.8 Vol% (0.3/1.8 Vol%), inspiratory of 0.6 Vol% (0.1/1.4 Vol%). Higher concentrations of isoflurane were associated with increased depth of sedation (expiratory p = 0.016; inspiratory p = 0.027; averaged p = 0.015). With tidal volume below 350 ml, association was still present for expiratory and averaged concentrations of isoflurane (expiratory p = 0.031; inspiratory p = 0.082; average p = 0.039).

CONCLUSIONS

This is the first study that shows that inhalative concentrations of isoflurane are associated with depth of sedation in patients with lung failure. We were able to show that even with major impacts in lung mechanics and function targeted sedation with volatile anaesthetics is feasible and dose-response relationship appears to exist.