Intraoperative hand strength as an indicator of consciousness during awake craniotomy: a prospective, observational study

Abstract

Awake craniotomy enables mapping and monitoring of brain functions. For successful procedures, rapid awakening and the precise evaluation of consciousness are required. A prospective, observational study conducted to test whether intraoperative hand strength could be a sensitive indicator of consciousness during the awake phase of awake craniotomy. Twenty-three patients who underwent awake craniotomy were included. Subtle changes of the level of consciousness were assessed by the Japan Coma Scale (JCS). The associations of hand strength on the unaffected side with the predicted plasma concentration (Cp) of propofol, the bispectral index (BIS), and the JCS were analyzed. Hand strength relative to the preoperative maximum hand strength on the unaffected side showed significant correlations with the Cp of propofol (ρ = − 0.219, p = 0.007), the BIS (ρ = 0.259, p = 0.002), and the JCS (τ = − 0.508, p = 0.001). Receiver operating characteristic curve analysis for discriminating JCS 0–1 and JCS ≥ 2 demonstrated that the area under the curve was 0.76 for hand strength, 0.78 for Cp of propofol, and 0.66 for BIS. With a cutoff value of 75% for hand strength, the sensitivity was 0.76, and the specificity was 0.67. These data demonstrated that hand strength is a useful indicator for assessing the intraoperative level of consciousness during awake craniotomy.