Abstract



 



Purpose   The purpose of this study was to determine the optimal dose of dexmedetomidine administered upon surgery completion that would provide the best quality emergence. The goal was to prevent cough, agitation, hypertension, and tachycardia following general anesthesia.



Background   Emergence from general anesthesia has been associated with potentially detrimental physiologic changes such as: coughing, agitation, hypertension, tachycardia, bleeding, and shivering, among others. Periextubation cough has the potential to cause postoperative complications, especially when hypertensive episodes need to be avoided or when increases in intraocular or intracranial pressures can occur. Lidocaine, ketamine, opioids, and dexmedetomidine have been previously studied for their ability to prevent or treating the side effects of an agitated emergence from anesthesia. Dexmedetomidine is an option with an attractive side effect profile. As a central alpha-2 agonist, dexmedetomidine encompasses analgesic, sedative, sympatholytic, anxiolytic, and opioid sparing properties without contributing to respiratory depression. Previous studies have suggested intraoperative infusions or boluses of dexmedetomidine at the end of surgery were associated with improved recovery profiles; however, the literature has not produced a consensus as to dexmedetomidine's ability to decrease cough and emergence phenomena. Efficacy and the optimal dexmedetomidine dose are poorly understood.



 



Methodology   The study was a prospective, randomized, double-blind trial. Adult patients scheduled for elective surgery requiring general anesthetics ranging from 1-3 hours were eligible for the study. Patients were excluded from the study if they were obese (BMI >35 Kg/m2), febrile, pregnant, prescribed anti-depressants, and those with chronic pain who were prescribed opioid medications. Two hundred sixteen patients were selected and randomly assigned to 4 groups: dexmedetomidine 1µg/Kg (Dex 1), 0.5µg/Kg (Dex 0.5), 0.25µg/Kg (Dex 0.25), or Control. Upon surgical completion and discontinuation of general anesthesia, patients received their assigned dose or placebo as a 10 minute IV infusion.



 



Result   Surgical procedures were evenly distributed between the four groups and included: orthopedic, general, gynecological, head and neck, and urological procedures. Both N2O and sevoflorane end tidal concentrations were 0 at the time of extubation. The incidence of cough at extubation was lower in all three dexmedetomidine groups compared to the Control group (Table 1). Furthermore, moderate and severe cough in the dexmedetomidine 1 µg/Kg group was reduced by over 60% compared to the control group.



 


























































Table 1: Events at Extubation




 




Dex 1 µg




Dex 0.5 µg




Dex 0.25 µg




Control




Cough




48%




64%




64%




84%




Increase in SBP




4%




11%




17%




35%




Increase in HR




11%




12%




30%




43%




Systolic < 90




27%




19%




16%




0%




Event at Emergence




Agitation




33%




34%




33%




72%




NOTES: Dex = dexmedetomidine, doses in µg/Kg. SBP = systolic blood pressure. HR = heart rate.




 



Hypotension (SBP < 90 mm Hg) was found in all dexmedetomidine groups but was not present in the Control group. The magnitude of HR and SBP deviation from baseline during emergence was inversely proportional to the dose of dexmedetomidine delivered. During emergence, the dexmedetomidine groups produced at most a mild elevation of SBP while SBP rose 35% in the control group. On extubation, tachycardia was only present in the Control subjects. Emergence agitation occurred in over 70% of the Control group but only approximately 33% of the dexmedetomidine groups.



 



There was no variation in sedation scores among the four groups upon arrival to the PACU. PACU hemodynamics were most stable in the dexmedetomidine groups. Lastly, PACU length of stay was not statistically different between all groups (Figure 1).



 













Figure 1. Systolic BP Over Time







 



Conclusion   Dexmedetomidine 1µg/Kg administered at the end of surgery minimized cough during extubation and considerably reduced moderate and severe coughing. Furthermore, the incidence of emergence agitation was diminished significantly among all dexmedetomidine groups. There was no delay in extubation or PACU discharge.



 



Comment



 



While dexmedetomidine itself is not new to anesthesia practice, how to fully realize its anesthetic benefits has remained somewhat of a mystery. Probably the biggest reason many of us don’t use dexmedetomidine is the fear that emergence, awakening, and discharge times will be delayed. Some feel this cost outweighs the benefits and avoid dexmedetomidine in their anesthetic practice. In my experience, prolonged time to extubation, prolonged PACU stays, and delayed outpatient discharge usually result from either improper dexmedetomidine dosing and/or the timing of administration.



 



At my clinical institution, the Oral Maxillofacial Surgery (OMFS) team expressed concern over postoperative hematoma formation in their LeFort I osteotomy patients. In collaboration with the Chief of OMFS, I developed an anesthetic protocol which includes a dexmedetomidine 1 µg/Kg infusion. Since implementation of the protocol, rates of tachycardia, hypertension and emergence agitation have been reduced considerably along with the incidence of postoperative hematoma formation.