The Effect of Dexmedetomidine on Middle Ear Pressure

Effect of dexmedetomidine on hemodynamic responses to tracheal intubation: A meta-analysis with meta-regression and trial sequential analysis

STUDY OBJECTIVE

An uncontrolled adrenergic response during tracheal intubation may lead to life-threatening complications. Dexmedetomidine binds to α2-receptors and may attenuate this response. The primary aim of our meta-analysis is to investigate dexmedetomidine efficacy in attenuating sympathetic response to tracheal intubation, compared with placebo or no dexmedetomidine, in terms of heart rate and blood pressure at intubation.

DESIGN

Meta-analysis with meta-regression and trial sequential analysis.

SETTING

Systematic search from inception until December 1, 2020 in the following databases: Pubmed, Scopus, the Cochrane Central Register of Controlled Trials, EMBASE and Google Scholar.

INTERVENTIONS

All randomized controlled trials investigating intravenous dexmedetomidine as premedication in adult patients undergoing tracheal intubation were included in our study. Studies were included without any language or publication date restriction. A trial sequential analysis and a post-hoc meta-regression were performed on the main outcomes.

MEASUREMENTS

Hemodynamic parameters and heart rate at tracheal intubation, dose of anesthetic needed for induction of anesthesia, total anesthetic requirement throughout the operative procedure, postoperative pain and percentage of patients requiring analgesics at 24 postoperative hours, postoperative nausea and vomiting, intraoperative and postoperative bradycardia, hypotension, dizziness, shivering and/or respiratory depression.

MAIN RESULTS

Ninety-nine included studies randomized 6833 patients. During laryngoscopy, all hemodynamic parameters were significantly greater in the no dexmedetomidine group. In particular, in the dexmedetomidine group, systolic blood pressure differed by -21.8 mm Hg (95% CI -26.6 to -17.1, p-value < 0.001, I² 97%), mean arterial pressure by -12.8 mm Hg (95% CI -15.6 to -10.0, p-value < 0.001, I² 98%), and heart rate by -16.9 bpm (95% CI -19.8 to -13.9, p-value < 0.001, I² 98%).

CONCLUSIONS

Patients receiving premedication with dexmedetomidine for tracheal intubation, compared with no dexmedetomidine, have a lower blood pressure and heart rate, however, the risk of bradycardia and hypotension is relevant and its use during daily practice should be cautiously evaluated for each patient.

Dexmedetomidine infusion during middle ear surgery under general anaesthesia to provide oligaemic surgical field: A prospective study

Background and Aims:

Middle ear surgery requires bloodless surgical field for better operating conditions, deep level of anaesthesia and rapid emergence. Recent studies suggest that α2 agonists could provide desired surgical field, sedation and analgesia. The present study was aimed to evaluate the clinical effects of dexmedetomidine infusion as anaesthetic adjuvant during middle ear surgery using operating microscope.

Methods:

Sixty four adult patients aged 18-58 years, American Society of Anaesthesiologists Grades I and II, of both gender were randomised into two comparable equal groups of 32 patients each for middle ear surgery under general anaesthesia with standard anaesthetic technique. After induction of general anaesthesia, patients of Group I were given dexmedetomidine infusion of 0.5 μg/kg/h and patients of Group II were given placebo infusion of normal saline. Isoflurane concentration was titrated to achieve a systolic blood pressure 30% below the baseline value. All patients were assessed intra-operatively for bleeding at surgical field, haemodynamic changes, awakening time and post-operative recovery.

Results:

Statistically significant reduction was observed in the required percentage of isoflurane (0.8 ± 0.6%) to maintain the systolic blood pressure 30% below the baseline values in patients receiving dexmedetomidine infusion when compared to those receiving placebo infusion (1.6 ± 0.7%). Patients receiving dexmedetomidine infusion had statistically significant lesser bleeding at surgical field (P < 0.05). The mean awakening time and recovery from anaesthesia did not show any significant difference between the groups.

Conclusion:

Dexmedetomidine infusion can be safely used to provide oligaemic surgical field for better visualization using operating microscope for middle ear surgery.

Different effects of propofol and isoflurane on cochlear blood flow and hearing function in Guinea pigs

Objectives

To investigate the effects of isoflurane and propofol on mean arterial pressure (MAP), cochlear blood flow (CoBF), distortion-product otoacoustic emission (DPOAE), and the ultrastructure of outer hair cells (OHCs) in guinea pig cochleae.

Methods

Forty-eight male guinea pigs were randomly assigned to one of six treatment groups. Groups 1 to 3 were infused (i.v.) with a loading dose of propofol (5 mg/kg) for 5 min and three maintenance doses (10, 20, or 40 mg kg⁻¹·h⁻¹, respectively) for 115 min. Groups 4 to 6 were inhaled with isoflurane at concentrations of 1.15 vol%, 2.30 vol% or 3.45 vol% respectively for 120 min. CoBF and MAP were recorded prior to and at 5 min intervals during drug administration. DPOAE was measured before, immediately after, and 1 h after administration. Following the final DPOAE test, cochleae were examined using scanning electron microscopy.

Results

Propofol treatment reduced MAP in a dose-dependent manner. CoBF and DPOAE showed increases at propofol maintenance doses of 10 and 20 mg kg⁻¹·h⁻¹. Inhalation of isoflurane at concentrations of 2.30 vol% and 3.45 vol% reduced MAP and CoBF. DPOAE amplitude increased following inhalation of 1.15 vol% isoflurane, but decreased following inhalations of 2.30 vol% and 3.45 vol%. Cochlear structure was changed following inhalation of either 2.30 vol% or 3.45 vol% isoflurane.

Conclusions

Propofol could decrease MAP and increase both CoBF and DPOAE without affecting OHC structure. Inhalation of isoflurane at concentrations >2.30 vol% decreased CoBF and DPOAE, and produced injury to OHCs.

Comparison of the effects of desflurane and sevoflurane on middle ear pressure: a randomized controlled clinical trial

OBJECTIVE

The aim of the present study was to compare the effects of two inhalation anesthetics, desflurane and sevoflurane, on middle ear pressure.

METHODS

After we obtained written consent from the patients and the approval from our institutional ethical committee, we included 56 ASA I-II patients aged between 18 and 60 years in this study. They were randomly divided into two groups of 28 patients each. Desflurane 4-6% (Group D) or sevoflurane 1-2% (Group S) were used for anesthesia management in patients. Baseline tympanometry was carried out and recorded before the induction of anesthesia on both ears, and 3 more measurements were done and recorded 5, 15 and 30 min after induction.

RESULTS

In both groups, middle ear pressure values were found to be significantly elevated when compared to baseline measurements (p < 0.05). When middle ear pressure was compared between the groups, no difference was found between the values obtained at baseline and at 5 min in Group S, while especially the values obtained at 15 min revealed significantly higher middle ear pressures in Group D.

CONCLUSION

It was observed that the increase in middle ear pressure caused by sevoflurane was significantly lower than that caused by desflurane.