Effect of Different Loading Doses of Dexmedetomidine on Controlled Hypotension and the Incidence of Bradycardia During Rhinoplasty: A Clinical Trial

Abstract

: Controlled hypotension, with a mean arterial pressure (MAP) of 60 mmHg - 70 mmHg, provides a bloodless and visible surgical field during rhinoplasty. It has been shown that dexmedetomidine, an α2-adrenoreceptor agonist, is a suitable choice in this regard. One of the disadvantages of this drug is the possibility of severe bradycardia during infusion. Therefore, we compared lower intravenous (IV) loading doses to determine whether the hypotensive effect of the drug was preserved and the bradycardia incidence decreased. In this randomized, double-blinded clinical trial, 81 patients aged 18 to 50 years with the American Society of Anesthesiologists physical status (ASA-PS) class I and II, scheduled for rhinoplasty randomly received 1.0, 0.9, and 0.8 µg/kg (named as groups 1.0, 0.9, and 0.8, respectively) of IV dexmedetomidine before the induction of anesthesia followed by infusion (0.3 - 0.7 µg/kg/h) during operation. The patients’ heart rate (HR), MAP, the requirements for nitroglycerin (NTG) and extra fentanyl, as well as the incidence of bradycardia, were recorded. Bleeding and visibility of the surgical field were scored by the surgeon using a 6-point visual scale. MAPs, HRs, and consumption of NTG and extra fentanyl were similar in the studied groups. The surgical field was more visible and bloodless in group 1.0 compared to group 0.8 (P < 0.001); the differences were not significant between groups 1.0 and 0.9 (P = 0.605). The incidence (P = 0.027) and the severity of bradycardia (P = 0.017) were higher in the groups with higher loading doses. We concluded that dexmedetomidine is an acceptable agent to provide controlled hypotension. A loading dose of 0.9 µg/kg, but not 0.8 µg/kg, provides similar surgical field conditions as the dose of 1 µg/kg. Furthermore, despite the decrease in the incidence of bradycardia, the hypotensive effect of the drug is preserved.

Dexmedetomidine Effects on Surgical Stress Hormones

“…These results are in accordance with theory, where dexmedetomidine administration during surgery will significantly reduce MAP. [27][28][29][30] Multivariate analysis of the mean HR value showed a statistically significant decrease (p<0.001) in the therapy group compared to the control group. Exploring and testing the initial HR value data before treatment was given, the results of the two variables were not statistically significantly different (p=0.925).…”

Dexmedetomidine versus remifentanil in nasal surgery: a systematic review and meta-analysis

“…Motlagh and colleagues suggested using lower loading doses of the alpha agonist to reduce alpha stimulation of vascular smooth muscles. This approach aims to maintain optimal hypotension, ensure a clear field, and prevent life-threatening bradycardia by preserving central sympathetic outflow [ 41 ]. Rashad et al confirmed that dexmedetomidine not only maintains preferred hemodynamics but also reduces the need for postoperative analgesics and decreases the occurrence of nausea and vomiting [ 42 ].…”

“…This meta-analysis, the first of its kind for these recently used anesthetics, is subject to limitations, including a small sample size (5 trials and 302 participants), which weakens the reliability and evidence supporting the comparison of dexmedetomidine and remifentanil. Additionally, varying induction doses in the included articles, as noted by Motlagh et al [ 41 ], may lead to complications such as uncontrolled bradycardia, hypotension, or hypertension. The study emphasizes the significance of distinct protocols for the induction and maintenance of sedation for remifentanil and dexmedetomidine due to their varied half-life and peak effects.…”

Risk factors for dexmedetomidine-associated bradycardia during spinal anesthesia: A retrospective study

“…A recent study reported that the incidence of bradycardia was significantly higher when the loading dose was 1.0 mcg/kg than when it was 0.8 mcg/kg. [ 16 ] Ko et al reported that the effective loading dose of dexmedetomidine for adequate sedation is 0.86 µg/kg; however, a dose higher than 0.5 µg/kg is associated with hemodynamic instability. [ 17 ] In our study, an average loading dose of 0.7 mcg/kg was administered with a 25% incidence of bradycardia.…”