Clinical evaluation of the effect of intravenous dexmedetomidine on the hemodynamic response to laryngoscopy and endotracheal intubation in patients undergoing thyroid surgeries.

BACKGROUND: The procedures in anesthesia such as laryngoscopy and endotracheal intubation are the most important skills to be mastered by an anesthesiologist. However, they produce marked cardiovascular responses such as hypertension and tachycardia. Various drugs have been used to suppress this response. One of those is a novel centrally acting α2 agonist - dexmedetomidine. It has numerous uses in anesthesia as it is having sedative, analgesic, hypnotic, and opioid sparing effects. It is also known to suppress the hemodynamic response to laryngoscopy and intubation. AIMS: This study is aimed to know the effect of intravenous dexmedetomidine 0.6 μg/kg body weight on hemodynamic response to laryngoscopy and endotracheal intubation in patients undergoing thyroid surgeries. SETTING AND
DESIGN: Sixty patients of American Society of Anaesthesiologist health status class I and II scheduled for thyroid surgery under general anesthesia were considered in this prospective randomized controlled double-blind study. The study population was randomly divided into two groups with 30 patients in each group using sealed envelopes containing the name of the group and patient is asked to pick up the envelope.
MATERIALS AND METHODS: Sixty euthyroid patients, scheduled for thyroid surgeries was randomly divided into two groups with 30 patients in each group. Group A (n = 30) received injection dexmedetomidine 0.6 μg/kg body weight and Group B (n = 30) received 10 ml of normal saline. Heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP), and mean arterial pressure (MAP) were recorded at regular intervals after intubation.
RESULTS: Statistically significant decrease in HR, SBP, DBP, and MAP were observed in Group A after intubation when compared to Group B.
CONCLUSION: We conclude that dexmedetomidine 0.6 μg/kg body weight obtunds the hemodynamic responses to laryngoscopy and tracheal intubation in patients undergoing thyroid surgeries.

RCT Entities:   Population Interventions Outcomes

INTRODUCTION

Administration of general anesthesia through laryngoscopy and endotracheal intubation is the most important and essential skill for an anesthesiologist. However, both laryngoscopy and intubation are noxious stimuli and are associated with hemodynamic responses such as hypertension and tachycardia.[1] The increase in the heart rate (HR) and blood pressure are usually transitory, variable, and unpredictable. Intravenous anesthetic induction agents do not adequately suppress the hemodynamic responses produced by endotracheal intubation.[2] Besides minimizing the cardiovascular response, anesthesia induction for patients at risk must also satisfy the following requirements. It should neither be time-consuming nor affect the duration or modality of anesthetic technique and also should not have any effect on the recovery characteristics of the patient.

Dexmedetomidine, a novel α2 agonist, has numerous applications in anesthesia and Intensive Care Unit because it causes sedation, hypnosis, analgesia, and sympatholysis.[345] Various studies have found that dexmedetomidine decreases the hemodynamic response to laryngoscopy and intubation.[678910] Different dose has been tried for the same.

Thyroid surgeries pose a multitude of challenges to an anesthesiologist. The commonest implications during such procedures involve the management of a potentially difficult airway, especially in cases of retrosternal goiter, and an enlarged thyroid gland compressing over the trachea for a prolonged duration.[111213] Very few literature are available on the usage of dexmedetomidine for thyroid surgeries.

Hence, this study was aimed at studying the effectiveness of intravenous dexmedetomidine, 0.6 µg/kg body weight on hemodynamic response to laryngoscopy and endotracheal intubation in patients undergoing thyroid surgeries.

MATERIALS AND METHODS

A prospective, randomized, controlled, double-blind study was done at Adichunchanagiri Institute of Medical Sciences Hospital, BG Nagar, using intravenous dexmedetomidine 0.6 µg/kg body weight for attenuation of hemodynamic response to laryngoscopy and endotracheal intubation in patients undergoing thyroid surgeries during a period of 1 year between January 2015 and December 2015.

The study was undertaken after obtaining ethical committee clearance as well as informed consent from all patients. Sixty euthyroid patients, scheduled for elective thyroid surgeries under general endotracheal anesthesia belonging to American Society of Anaesthesiologists (ASA) physical status I and II were selected for the study. As all 60 patients were taken for thyroid surgeries electively, preoperative optimization of thyroid function was done adequately. All patients were in euthyroid status before taking up for surgery.

The following patients were excluded from the study, those with cardiac, renal, hepatic, cerebral diseases and peripheral vascular diseases, known history of sensitivity and contraindications to drugs used, noneuthyroid at the time of surgery, patients with hypertension and diabetes mellitus, patients coming for emergency surgeries, anticipated difficult airway, pregnant females, and time for laryngoscopy and intubation exceeding 15 s.

Patients with relatively large swelling of thyroid were not considered for the study anticipating difficult airway. Furthermore, patients on beta blockers were not considered for the study as it can interfere in the hemodynamic variables after administration of dexmedetomidine.

Routine investigations such as hemoglobin, white cell and platelet count, urea and electrolytes, and specific investigations such as thyroid function tests, serum calcium, chest X-ray, electrocardiogram (ECG), indirect laryngoscopy, and X-ray anteroposterior and lateral view of the neck was done in all patients.

The study population was randomly divided into two groups with 30 patients in each group using sealed envelopes containing the name of the group and patient is asked to pick up the envelope. The envelope was opened by a senior anesthesiologist who was assigned to prepare the solutions and was not involved with the study. Group A (n = 30) received injection dexmedetomidine 0.6 µg/kg body weight diluted to 10 ml of normal saline, administered intravenously over 10 min. Group B (n = 30) received 10 ml of normal saline, administered intravenously over 10 min.

All patients included in the study were premedicated with tablet alprazolam 0.5 mg and tablet ranitidine 150 mg orally at bedtime the previous night before surgery. They were kept nil orally 10 pm onward on the previous night.

On arrival of the patient in the operating room, an 18-gauge intravenous cannula was inserted, and an infusion of 500 ml Ringer lactate was started. The patients were connected to Star Plus Larsen and Toubro India Limited, multiparameter monitor which records HR, noninvasive measurements of systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP), and continuous ECG monitoring and oxygen saturation. The baseline SBP, DBP, MAP, and HR were recorded.

After recording the baseline readings, patients in Group A, received dexmedetomidine 0.6 µg/kg body weight diluted in 10 ml normal saline intravenously over 10 min using syringe pump, 10 min before induction. Patients in Group B received normal saline 10 ml intravenously over 10 min using syringe pump, 10 min before induction.

The study drug was prepared by the senior anesthesiologist who was not involved in the study and as such, the observer as well as patient was blinded for the study.

All patients were premedicated with injection midazolam - 0.02 mg/kg body weight and injection fentanyl 1 µg/kg body intravenous (i.v.) after test drug administration. Then patients were preoxygenated for 3 min via a face mask with Bain's circuit. Anesthesia was induced with injection thiopentone as a 2.5% solution, in 25 mg increments till the loss of eyelash reflex. Endotracheal intubation was facilitated with 1.5 mg/kg i.v. succinylcholine 1 min before laryngoscopy and intubation. Laryngoscopy and intubation were performed using Macintosh No. 3 blade lasting for not more than 15 s and after confirmation of bilateral equal air entry and EtCO2, the endotracheal tube was fixed.

Anesthesia was maintained using 66% nitrous oxide and 33% of oxygen with 1% isoflurane. After the patients recovered from succinylcholine, the further neuromuscular blockade was maintained with vecuronium 0.05 mg/kg body weight initially and 0.5 mg increments as and when required. At the end of the procedure, patients were reversed with injection neostigmine - 0.05 mg/kg body weight and injection glycopyrrolate - 0.01 mg/kg body weight.

The cardiovascular parameters were monitored in the following time interval basal-before giving study drug, 1 min after laryngoscopy and intubation, 5 min after laryngoscopy and intubation and 10 min after laryngoscopy and intubation.

Statistical analysis

A sample size of 25 patients was needed to detect an intergroup difference of at least 10% in BP and HR with a power of 0.80 and α of 0.05. To make good for attrition rate, a total number of 30 patients in each group were included for the study. The independent samples t-test procedure compares means for two groups of cases. The crosstabs procedure forms two-way and multi-way tables and provides a variety of tests and measures of association for two-way tables. Repeated measures ANOVA analyzes groups of related dependent variables that represent different measurements of the same attribute.

SPSS for windows (version 17.0) (SPSS Inc., Chicago II, USA) was employed for data analysis. P <0.05 was considered as significant and P < 0.01 was considered as highly significant.

RESULTS

Sixty euthyroid patients belonging to ASA physical status I and II undergoing thyroid surgeries were included in the study. As shown in Table 1, patients in both groups were comparable with respect to baseline demographic characteristics.

Table 1

Demographic characteristics of patients

As shown in Table 2, the basal mean HR was comparable in both groups. Statistical evaluation between the groups showed highly statistically significant (P < 0.001) fall in the mean HR in Group A compared to Group B after intubation at 1st min, 5th min, and 10th min.

Table 2

The intergroup comparison of mean heart rate (bpm) changes in response to laryngoscopy and intubation between Group A and Group B

As shown in Table 3, the basal mean SBP were comparable in both groups. Statistical evaluation between the groups shows highly statistical significant fall (P < 0.001) in the mean SBP in Group A when compared to Group B, after intubation at 1st min, 5th min, and 10th min.

Table 3

The intergroup comparison of systolic blood pressure (mmHg) changes in response to laryngoscopy and intubation between Group A and Group B

As shown in Table 4, the basal mean DBP were comparable in both groups. Statistical evaluation between the groups shows highly statistically significant decrease (P < 0.001) in the mean DBP in Group A when compared to Group B, after intubation at 1st min, 5th min, and 10th min.

Table 4

The intergroup comparison of diastolic blood pressure (mmHg) changes in response to laryngoscopy and intubation between Group A and Group B

As shown in Table 5, the basal mean MAP was comparable in both groups. Statistical evaluation between the groups shows highly statistical significant fall (P < 0.001) in the mean MAP in Group A when compared to Group B, after intubation at 1st min, 5th min, and 10th min.

Table 5

The intergroup comparison of mean arterial pressure (mmHg) changes in response to laryngoscopy and intubation between Group A and Group B

DISCUSSION

Different doses of dexmedetomidine have been used to find the effectiveness for blunting hemodynamic responses to laryngoscopy and intubation.[678910] In our study, following laryngoscopy and intubation at 1 min, the mean HR increased by 36 bpm in the Group B whereas in Group A the mean HR increased by only 4 bpm which is statistically highly significant (P = 0.000) when compared to control group (Group B). At 5th min, the increase in mean HR in the control group (Group B) sustained, and it was 23 bpm, whereas in Group A there is a decrease in HR by 3 which is statistically significant. Similar observations were made by Scheinin et al.[6] and Jaakola et al.[7] At 10th min, there was an increase in HR by 13 bpm in control group compared to decrease in the HR by 4 bpm in Group A, which was statistically significant. Our study compares with the studies done by Basar et al.[9]

In our study, it is seen that there is highly significant fall in the SBP in Group A at 1st min, 5th min, and 10th min following laryngoscopy and intubation compared to control group (P = 0.000) wherein there was an increase of SBP of 29 mmHg, 11 mmHg and 1 mmHg at 1st min, 5th min, and 10 min following laryngoscopy and intubation respectively which is comparable with other studies.[67891415]

After laryngoscopy and intubation, there is an increase of DBP by 21 mmHg in the control group which gradually decreased to near basal values by 10th min. In Group A, there is an increase in DBP at 1st min by 8 mmHg and 5 mmHg respectively. However, there is a decrease in DBP by 9 mmHg and 11 mmHg at 5th min and 10th min in Group A compared to basal values which are statistically highly significant. Similar observations were noted in other studies.[71516]

Furthermore, we found that there was a significant decrease in MAP values by 11 mmHg and 14 mmHg, respectively in Group A after intubation at 5th and 10th min, respectively when compared to Group B. Similar observations were noted in other studies.[1516]

In 2012 Patel et al.,[14] conducted a similar study to assess the effect of i.v. dexmedetomidine on perioperative hemodynamics and also postoperative recovery in elective surgical procedures with continuous monitoring of depth of anesthesia by entropy analysis.

They noted that dexmedetomidine significantly attenuates stress response at intubation with lesser increase in HR (10% vs. 17%), SBP (6% vs. 23%), and DBP (7% vs. 20%) as compared to the control group (P < 0.05).

Authors concluded that dexmedetomidine attenuates various stress responses during surgery and maintains the hemodynamic stability when used as an adjuvant in general anesthesia.

In 2012, Sulaiman et al.[17] conducted a prospective, randomized, double-blind controlled clinical trial of dexmedetomidine for attenuation of stress response to endotracheal intubation in 60 adult patients on beta blockers, scheduled to undergo elective off-pump coronary artery bypass grafting.

Authors noted that there was a statistically significant lower value of HR, SBP, DBP, and MAP in the dexmedetomidine group when compared with the control group. There was no incidence of hypotension or arrhythmias observed during the study period in any group.

They concluded that pretreatment with dexmedetomidine 0.5 µg/kg as 10 min infusion before induction of anesthesia was a safe and effective method to attenuate the hemodynamic response to the laryngoscopy and intubation in patients scheduled for elective off-pump coronary artery bypass surgery.

In 2016 Santosh and Mehandale[18] studied the effect of dexmedetomidine on duration and quality of analgesia produced by bilateral superficial cervical plexus block (BSCPB) with 0.5% ropivacaine in patients undergoing thyroid surgeries. Authors concluded that the combination of 0.5% ropivacaine and dexmedetomidine for BSCPB provided significantly prolonged and better quality of postoperative analgesia and patient satisfaction than with 0.5% ropivacaine alone in patients undergoing thyroidectomy.

CONCLUSION

We conclude that dexmedetomidine 0.6 µg/kg body weight significantly obtunds the hemodynamic responses to laryngoscopy and tracheal intubation in patients undergoing thyroid surgeries.

Limitation of the study

In our study, we could not measure the plasma concentration of dexmedetomidine related to its dose as the facility is not available in our institution. Hence, we were unable to study the dose-effect relationship of the drug. Sedation score is not measured in our study which is also the limitation of the study.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.