Intravenous Dexmedetomidine Infusion Compared with that of Fentanyl in Patients Undergoing Arthroscopic Shoulder Surgery under General Anesthesia.

BACKGROUND: Anesthesia for arthroscopic shoulder surgery is challenging due to the need for oligaemic surgical field as well as a good postoperative recovery profile. AIM: The present study was prospective, randomized to evaluate the efficacy of dexmdetomidine infusion compared to that of fentanyl in patients undergoing arthroscopic shoulder surgery under general anesthesia. PATIENTS AND METHODS: A total of 60 patients aged from thirty to fifty years, American Society of Anesthesiologists Class I/II of either sex for arthroscopic shoulder surgery, were included. The patients were divided into two groups of 30 patients each. Group I received dexmedetomidine loading 1 μg/kg over 10 min followed by maintenance 0.5 μg/kg/h and Group II Fentanyl loading 1 μg/kg followed by maintenance 0.5 μg/kg/h. MEASUREMENTS: Hemodynamic readings (Heart rate HR, and mean arterial blood pressure MAP) were recorded after the start of the study drug infusion (T1), after intubation (T2), then every 15 minutes till the end of surgery (T15, T30, T45, T60, T75, T90). In the PACU, MAP, and HR were recorded on arrival, after 30 min, 1 hr, and 2 hrs (R0, R30, R1 hr, R2 hr) Postoperative analgesia was assessed by visual analogue scale (VAS), Modified Observers's Assessment of Alertness and Sedation OAA/S was recorded on arrival to PACU.
RESULTS: This study showed that in the dexmedatomidine group there was statistically significant decrease of MAP and HR after drug infusion up to two hours in the recovery period, more sedation, better control of pain and surgeon satisfaction.
CONCLUSION: Iv infusion of dexamedatomidine may be an attractive option during arthroscopic shoulder surgery as it provided a better hypotensive anesthesia by lowering MAP and HR which leads to better surgical field and surgeon satisfaction than iv infusion fentanyl along with a better postoperative VAS.

INTRODUCTION

Arthroscopic shoulder surgery is a minimally invasive technique that effectively treats certain diseases and injuries of the shoulder joint.[1]

Arthroscopic shoulder surgery is associated with moderate-to-severe postoperative pain which is comparable to the pain following a gastrectomy or thoracotomy and requires intensive pain management for several days.[2]

Controlling postoperative pain in shoulder surgery facilitates early mobilization and fast functional recovery, allowing pain-free muscle contraction.[3]

Another challenge of anesthesia for shoulder arthroscopic procedures is the need for controlled hypotension to lessen intraarticular bleeding to provide adequate visualization by the surgeon owing to inability to use a tourniquet in this situation.[4]

Dexmedetomidine (Precedex, HOSPIRA, Inc), an α2 agonist, was approved by the US Food and Drug Administration as an Intensive Care Unit sedative in 1991; it also possesses anxiolytic, anesthetic, hypnotic, and analgesic properties. In addition, it reduces the pressor responses mediated by the sympathetic nervous system.[5]

Fentanyl is a commonly used synthetic opiate for the relief of perioperative pain; it has an analgesic potency 50–100 times that of morphine.[6]

Aim of the study

This study was aimed to compare intravenous (IV) infusion of dexmedetomidine versus that of fentanyl during general anesthesia for arthroscopic shoulder surgery regarding hemodynamic parameters, surgical satisfaction, and postoperative sedation and pain scores.

Study design

This was a prospective randomized study.

PATIENTS AND METHODS

After obtaining an approval from the Ethical Committee of Kasr Al Ainy University Hospital, an informed written consent was taken from sixty patients of ASA class I or II aged 30–50 years with body mass index (BMI) 20–30 kg/m2 undergoing arthroscopic shoulder surgery under general anesthesia.

Patients with uncontrolled systemic diseases (e.g., diabetes mellitus, hypertension, and chronic obstructive lung disease), significant organ dysfunctions (e.g., cardiac, respiratory, renal, or liver disorders), morbid obesity (BMI >35), a history of allergy to the study drugs used, use of beta blockers or calcium channel blockers, and chronic use of opioids were excluded from the study.

On arrival to the operating room, all patients received 0.02 mg/kg midazolam IV as premedication 5 min before the induction of anesthesia.

Standard monitoring, namely, electrocardiogram, noninvasive blood pressure, and pulse oximetry were attached.

Baseline hemodynamic reading of mean arterial blood pressure (MAP) and heart rate (HR) were recorded (T0).

Patients were randomly allocated into two equal groups using a closed envelope technique to dexmedetomidine group (GDEX) (n = 30) which received dexmedetomidine 1 μg/kg over 10 min as loading dose followed by continuous infusion at a rate of 0.5 μg/kg/h during surgery and fentanyl group (GFEN) (n = 30) which received fentanyl 1 μg/kg as loading dose followed by continuous infusion at a rate of 0.5 μg/kg/h during surgery.

General anesthesia for all patients was induced by IV administration of 2 mg/kg propofol and intubation was facilitated by IV administration of 0.5 mg/kg atracurium and general anesthesia was maintained by inhalation of 1.5% isoflurane in 100% oxygen; ventilation was controlled aiming to keep normocapnia (ETCO2 between 35 and 40 mmHg).

Hemodynamic readings (MAP and HR) were recorded after the start of the study drug infusion (T1), after intubation (T2), then every 15 min till the end of surgery (T15, T30, T45, T60, T75, T90).

At the end of surgery, the infusion test drugs were stopped; extubation was done after full reversal (using 0.04 mg/kg of neostigmine with atropine 0.02 mg/kg and complete neuromuscular recovery and then the patients were transferred to the postanesthesia care unit [PACU]).

In the PACU, MAP and HR were recorded on arrival, after 30 min, 1 h, and 2 h (R0, R30, R1 h, R2 h).

Postoperative analgesia was assessed by visual analog scale (VAS); this scale ranges from 0 to 10 where 0 represents no pain and 10 represents worst pain,[7] and when VAS was more than 4 (0.04 mg/kg), morphine was given to the patients.

Modified Observer's Assessment of Alertness[8] and Sedation (OAA/S) was recorded on arrival to PACU; it is measured on a scale of 0–5 where

5 – Responds readily to name spoken in normal tone

4 – Lethargic response to name spoken in normal tone

3 – Response only after name is called loudly and /or repeatedly

2 – Response only after mild prodding or shaking

1 – Response only after painful trapezius squeeze

0 – No response after painful trapezius squeeze.

Surgeons were asked about their convenience with the anesthesia during surgery using a 2 scale simple questionnaire (1 = satisfied, 0 = unsatisfied).

Sample size

To see a mean difference in blood pressure of 10 mmHg between group with standard deviation (SD) of 8 mmHg, a minimum of 15 patients per group is required with a significance level of 0.05 and power of a test of 90% based on Jung et al.'s study,[9] we conducted this study on sixty patients to be more powerful, the patients were divided into two equal groups (30 each).

Statistical analysis

Data were analyzed using SPSS win statistical package version 17. Parametric demographic data were analyzed using Student's t-test; qualitative data were compared using Chi-square test or Fisher's exact test as appropriate. Numerical data were described as mean and SD or median and range as appropriate. While qualitative data were described as frequency and percentage, P < 0.05 will be considered as statistically significant.

RESULTS

Sixty patients were enrolled in this prospective study and were randomly divided into two equal GDEX and GFEN; each has 30 patients (n = 30).

Demographic data

Patients’ characteristics include age, sex, BMI, and duration of surgery. There was no statistically significant difference in the demographic data of both study groups with P > 0.05 as demonstrated in Table 1.

Table 1

Demographic data of patients in both study groups

Regarding MAP, this study showed that in the GDEX, there was statistically significant decrease of MAP after drug infusion up to 2 h in the recovery period [Table 2 and Figure 1].

Table 2

Mean arterial blood pressure changes in both study groups

Figure 1

Line curve to show changes in mean arterial blood pressure over time in the two groups showing significant difference between the 2 groups in mean arterial blood pressure at all time points except T0 and T1

Regarding HR in both study groups, this study showed that there was statistically significant decrease in HR in GDEX compared to GFEN after drug infusion up to 2 h in the recovery period [Table 3 and Figure 2].

Table 3

Heart rate changes in both study groups

Figure 2

Line curve to show changes in heart rate over time in the two groups showing significant difference between the two groups in heart rate at all time points except T0, T1, and T2

Figure 2 line curve shows changes in HR over time in the 2 groups showing significant difference between the two groups in HR at all time points except T0, T1, and T2.

Regarding VAS, it was significantly less in GDEX compared to GFEN at R0 (on arrival after extubation), R30 min, R1 h following surgery; however, after 2 h, it was comparable between both groups [Table 4 and Figure 3].

Table 4

Visual analog scale for postoperative pain

Figure 3

Changes of visual analog scale in the postoperative period in both groups showing significant difference between the two groups in visual analog scale at R0, R 30 min, and R 1 h

Regarding modified OAA/S, this study showed that there was statistically significant decrease in OAA/S score in GDEX compared to GFEN as demonstrated in Table 5.

Table 5

Observer's assessment of alertness and sedation for both groups

Regarding surgeon satisfaction, surgeons were satisfied in 25 patients (83.3%) in GDEX compared to GFEN where they were satisfied in 15 patients (50%) as showed in Table 6.

Table 6

Surgeon satisfaction

DISCUSSION

Arthroscopic shoulder surgery requires good surgical field visibility with good postoperative analgesia.

In this prospective randomized study, we studied the efficacy of intraoperative infusion of dexmedetomidine compared to that of fentanyl in arthroscopic shoulder surgery under general anesthesia. It is evident from the current study that patients who received dexmedetomidine infusion have oligemic surgical field and better visibility when compared to GFEN patients. These findings can be attributed to the fact that dexmedetomidine reduces sympathetic activity, resulting in lower blood pressure and reduced HR thereby decreasing blood loss at the surgical site, thus improving the quality of the surgical field with better surgeon satisfaction.

The main finding of this study was that intraoperative infusion of dexmedetomidine significantly attenuates the pressor response to intubation, extubation, and recovery as shown by that the MAP and HR which were significantly lower throughout the intraoperative and early recovery period in the dexmedetomidine group compared to the GFEN.

These results are in accordance with those of Feld et al.,[10] who studied twenty bariatric patients undergoing surgery for open gastric bypass; they used fentanyl 0.5 μg/kg bolus followed by 0.5 μg/kg/h or dexmedetomidine 0.5 μg/kg bolus followed by 0.4 μg/kg/h combined with desflurane; they found that mean blood pressure and HR were lower in the dexmedetomidine group compared with GFEN and also dexmedetomidine group provides better postoperative analgesia and this is also in line with this study.

Furthermore, Rao et al.[11] assessed hemodynamic and anesthetic advantages on 81 patients who underwent elective surgical procedures under general anesthesia; they were given a loading dose of dexmedetomidine 1 mg/kg, followed by a continuous infusion of 0.5 μg/kg/h until closure of the surgical incision; they found that there was a significant reduction in HR and systolic blood pressure following the loading dose of dexmedetomidine and also in the intraoperative period; this is strongly in line with this study.

Furthermore, in accordance with the current study, Aksu et al.[12] compared the effect of IV dexmedetomidine 0.5 μg/kg compared to fentanyl 1 μg/kg given 5 min before extubation on airway reflexes and hemodynamic responses to tracheal intubation during rhinoplasty in forty patients; they suggest that dexmedetomidine was more effective in attenuating airway reflex response to tracheal intubation and maintaining hemodynamic stability without prolonging recovery compared to fentanyl.

On the other hand, Turgut et al.[13] compared dexmedetomidine 0.6 μg/kg bolus dose and 0.2 μg/kg/h infusion versus fentanyl 1 μg/kg bolus and 0.5 μg/kg/h infusion in patients undergoing lumbar laminectomy. MAP values in the dexmedetomidine group were significantly higher than the GFEN and this in contrast to this study where MAP was statistically lower in the dexmedetomidine group compared to the GFEN, and this may be explained by the lower dexmedetomidine dose they used compared to the dose in this study which is 1 μg/kg as loading and 0.5 μg/kg/h as maintenance.

The bradycardiac effect of dexmedetomidine is primarily mediated by a decrease in sympathetic tone and partly by baroreceptor reflex and enhanced vagal activity.[14]

Regarding postoperative analgesia in this study, there was a statistically significant difference in the VAS between the two study groups with better score and analgesia in the dexmedetomidine group compared to GFEN in the immediate recovery period, after extubation in the recovery room R0, after 30 min (R30), and 1 h (R1 h) but was comparable between the two groups after 2 h (R 2 h); this is in accordance with a study done by Gurbet et al.,[15] who investigated the efficacy of dexmedetomidine infusion for postoperative analgesia after total abdominal hysterectomy and concluded that continuous IV dexmedetomidine during abdominal surgery provides effective postoperative analgesia and reduces postoperative morphine requirements.

Regarding sedation, patients in the dexmedetomidine group were more sedated than GFEN, and these results were in line with Jung et al.,[9] who found that Modified OAA/S scores of sedation were significantly lower in the dexmedetomidine infusion group after gynecologic laparoscopic surgery, and this could be explained that dexmedetomidine has sedative and analgesia-sparing effects through central actions in the locus coeruleus and in the dorsal horn of the spinal cord.[16]

Limitations of the study

There was a lack of bispectral index monitor to monitor intraoperative awareness

Lack of measurement of serum norepinephrine and cortisol level as a markers for stress response

To further studies are needed to assess postoperative analgesia for longer duration (24-48 h).

CONCLUSION

IV infusion of dexmedetomidine may be an attractive option during arthroscopic shoulder surgery as it provided a better hypotensive anesthesia by lowering MAP and HR which leads to better surgical field and surgeon satisfaction than IV infusion fentanyl along with decreased postoperative pain level which will help for early rehabilitation.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.