Density Spectral Array Patterns During Total Intravenous Anesthesia with Intravenous Lidocaine for Craniotomy: An Illustrative Two-Case Series.

Abstract

Purpose: Intravenous lidocaine is used as an adjuvant to total intravenous anesthesia (TIVA). To our knowledge, density spectral array (DSA) patterns during intravenous lidocaine administration in propofol-remifentanil TIVA for craniotomy have rarely been described. We present two illustrative cases for educational and hypothesis-generating purposes.

Patients and methods: Two adults underwent craniotomy for tumor resection (left cerebellopontine angle, Case 1; suprasellar, Case 2) with effect-site target-controlled infusion of propofol (Schnider model) and remifentanil (Minto model) and a bilateral scalp block. After a 1.5 mg/kg bolus, lidocaine was infused at 1.5 mg/kg/hour (Case 1) or 2 mg/kg/hour (Case 2) and stopped 30 minutes before the end of surgery. Frontal bispectral index (BIS) and DSA were recorded throughout and interpreted qualitatively at the bedside and offline.

Results: In Case 1, an alpha-delta pattern persisted during maintenance, including at the lowest targets used (propofol 1.8 mcg/mL, remifentanil 2.5 ng/mL; BIS 39-45). In Case 2, the DSA showed more pronounced delta dominance, attenuated alpha and beta activity, and intermittent burst suppression, which persisted when propofol was reduced to 1.5 mcg/mL. In both patients, transient beta-power increases were temporally associated with surgical stimulation; electromyographic contribution could not be excluded. No hemodynamic instability or adverse effect attributable to lidocaine was observed.

Conclusion: This two-patient illustrative case series demonstrates differing DSA patterns during propofol-remifentanil TIVA with two intravenous lidocaine infusion regimens. Because the observations come from different patients with multiple clinical and anesthetic confounders, no dose-response relationship or causal effect of lidocaine can be established. These hypothesis-generating observations require evaluation in controlled studies.