SA2 - A Comparison of Dexmedetomidine, Nicardipine, and Labetalol for Hypotensive Anesthesia: Effects on Surgeon Visibility, Blood Loss, Hemodynamic Parameters, and Operation Time in Orthognathic Surgery

Abstract: Orthognathic surgery carries significant potential for intraoperative blood loss due to the rich vascular supply of the head and neck, which can obscure surgical field visibility and increase operative time. Hypotensive anesthesia, involving controlled reduction of mean arterial pressure to < 70 mmHg, is widely accepted to reduce blood loss and improve surgical field visibility. While multiple agents can induce hypotensive anesthesia, no consensus exists regarding optimal medication selection. This study compares three agents: labetalol (beta-blocker), nicardipine (calcium channel blocker), and dexmedetomidine (alpha-2 agonist), in the setting of orthognathic surgery.

This randomized, double-blinded, prospective trial enrolled ASA I-II patients undergoing orthognathic surgery (Le Fort I, SARPE, bilateral sagittal split osteotomy, or combination procedures) with a single surgeon at Boston Medical Center. Ninety participants were enrolled between March 2025 and January 2026 (n = 30 per group). Patients were excluded if taking home beta-blockers, calcium channel blockers, or alpha-2 agonists, with stratified randomization by surgical site (maxillary only or double jaw). The primary outcome was intraoperative surgical field visibility assessed by the blinded surgeon using Fromme score (0-5, where 0 = no bleeding and 5 = massive uncontrollable bleeding). Secondary outcomes included estimated blood loss (EBL), hemodynamic parameters (MAP, systolic blood pressure, heart rate), operation time, and adverse events. This study was approved by the Boston Medical Center Institutional Review Board (Protocol #H-43663), and written informed consent was obtained from all participants prior to enrollment.

An intention-to-treat analysis was performed. Demographic variables, surgical characteristics, and outcome measures (including Fromme score, EBL, hemodynamic parameters, and operation time) were summarized using counts and percentages for categorical variables and medians with interquartile ranges for continuous variables. Between-group differences were assessed using Fisher's exact test for categorical variables and the Kruskal-Wallis test for continuous variables. Prespecified subset analyses were performed by surgery type, use of additional intraoperative medications, and single-agent versus multi-agent study drug administration.

Of 90 enrolled participants, 85 were included in the ITT analysis (dexmedetomidine n = 28, nicardipine n = 28, labetalol n = 29); 5 were excluded as they did not receive the assigned agent. Treatment groups were well-matched at baseline with no significant differences in age, sex, ASA classification, baseline blood pressure, or surgical distribution (all P > .2). Fromme scores did not differ significantly across groups (P = .715), with the majority of patients in each arm scoring 1-2. EBL (300, 250, 350 mL; P = .379) and operative duration (238, 206, 233 min; P = .896) were comparable. Dexmedetomidine and nicardipine achieved significantly lower systolic (94.6, 95.4 vs 99.2 mmHg; P = .039) and diastolic blood pressure (52.7, 52.0 vs 55.1 mmHg; P = .024) compared to labetalol, with MAP trending lower (69.5, 69.6 vs 72.7 mmHg; P = .051). Heart rate was significantly higher with nicardipine versus dexmedetomidine and labetalol (86.3 vs 74.8 and 80.4 bpm; P = .007). Subset analyses are pending final data verification.

All three agents achieved comparable surgical field visibility, blood loss, and operative duration, supporting equivalent clinical efficacy. Dexmedetomidine and nicardipine achieved greater intraoperative blood pressure reductions, while nicardipine was associated with a significantly higher heart rate, likely reflecting reflex tachycardia secondary to vasodilation. Labetalol achieved adequate hypotension with a more moderate hemodynamic profile. These findings support individualized agent selection based on provider familiarity, patient-specific considerations, and institutional availability without compromising surgical outcomes.


References:

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