|Year : 2019 | Volume
| Issue : 4 | Page : 683-687
Safety and efficacy of dexmedetomidine versus propofol infusion as an adjunct to transtracheal block in ensuring patient immobility during general anesthesia without the use of muscle relaxants
Pulak Tosh, Sunil Rajan
Department of Anaesthesiology, Amrita Institute of Medical Sciences, Amrita Vishwa Vidyapeetham, Kochi, Kerala, India
|Date of Submission||04-Nov-2019|
|Date of Decision||06-Nov-2019|
|Date of Acceptance||29-Nov-2019|
|Date of Web Publication||16-Dec-2019|
Department of Anaesthesiology, Amrita Institute of Medical Sciences, Kochi, Kerala
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Background: In surgeries where nerve stimulation study is required intraoperatively, the use of long-acting muscle relaxants should be avoided. Aim of Study: This study aimed to assess the efficacy of dexmedetomidine versus propofol infusion as an adjunct to transtracheal block to ensure patient immobility during general anesthesia without the use of muscle relaxants and to compare hemodynamics in both the groups. Settings and Design: It was a prospective randomized controlled trial done at a tertiary care center. Subjects and Methods: Forty adult patients undergoing brachial plexus surgeries were included in the study and all patients received a transtracheal block just before the induction. After standardized induction and intubation, Group D received intravenous (i.v.) bolus of dexmedetomidine 0.5 μg.kg-1 body weight followed by infusion at 0.5 μg/kg/h intraoperatively. In Group B, the infusion of propofol was started at 1 mg/kg/h after induction. In both the groups, if the patient moved, bucked on endotracheal tube, or if there were signs of inadequate depth of anesthesia, bolus of propofol 0.5 mg.kg-1 i.v. was given and repeated as required. Statistical Tests Used: Mann–Whitney U-test and Fisher's exact test were used for the statistical analysis. Results: Number of times propofol bolus was required intraoperatively and hemodynamic parameters were comparable in both the groups at all-time points. Time to extubate was significantly higher in Group P compared to Group D (16.06 ± 5.78 vs. 9.61 ± 11.53 min). Conclusion: The use of dexmedetomidine infusion as an adjunct to transtracheal block is superior to propofol infusion in view of significantly shorter extubation time though both the agents provided comparable intraoperative hemodynamics and patient immobility.
Keywords: Dexmedetomidine, general anesthesia, propofol, relaxants, transtracheal
|How to cite this article:|
Tosh P, Rajan S. Safety and efficacy of dexmedetomidine versus propofol infusion as an adjunct to transtracheal block in ensuring patient immobility during general anesthesia without the use of muscle relaxants. Anesth Essays Res 2019;13:683-7
|How to cite this URL:|
Tosh P, Rajan S. Safety and efficacy of dexmedetomidine versus propofol infusion as an adjunct to transtracheal block in ensuring patient immobility during general anesthesia without the use of muscle relaxants. Anesth Essays Res [serial online] 2019 [cited 2020 Jan 25];13:683-7. Available from: http://www.aeronline.org/text.asp?2019/13/4/683/272978
| Introduction|| |
The use of muscle relaxants is a regular practice during general anesthesia. It is often necessary to help the surgeons achieve the best possible operating conditions under general anesthesia by providing relaxation or an immobile field so that intricate procedures such as finer dissection or anastomosis could be done. However, frequently during total parotidectomy or brachial plexus surgeries where identification of nerves or their integrity is to be checked, a request for avoidance of longacting neuromuscular blockers is made. This is usually managed by increasing depth of anesthesia with supplemental intravenous (i.v.) infusion of propofol or dexmedetomidine but may be associated with hemodynamic instability. The use of a transtracheal block as an adjunct to general anesthesia has shown its efficacy as an alternative to the use of muscle relaxants.,, This technique helps to reduce the dose of IV or inhalational agent required to produce patient immobility by increasing the endotracheal tube (ETT) tolerance so that a lower depth of anesthesia can ensure patient immobility.
The primary objective of the present study was to assess the efficacy of dexmedetomidine versus propofol infusion as an adjunct to transtracheal block in providing patient immobility during surgeries under general anesthesia without the use of long-acting neuromuscular blockers. The secondary objectives included a comparison of hemodynamic changes, use of anticholinergics, vasopressors or inotropes, and the time taken to extubate following the use of these two drugs.
| Subjects and Methods|| |
The present study was a prospective randomized single-blinded one performed in forty patients after obtaining Institutional Ethical Committee clearance. Following a detailed preanesthesia checkup, forty consenting patients aged 18–70 years who belonged to the American Society of Anesthesiologist physical status (ASA PS) Classes I and II and underwent brachial plexus surgeries under general anesthesia were included in the study. Those who had significant hepatic, renal, or cardiac diseases or had a history of allergy to any of the test drugs were excluded from the study.
The patients were randomly and equally allotted to either Group D or Group P based on the computer-generated random sequence of numbers. Allocation concealment was done with sequentially numbered opaque, sealed envelopes. All patients in both the groups received general anesthesia as per a standardized protocol.
All patients were kept fasted 6 h for solids and 2 h for clear fluids and were brought to the operation theater. After attaching standard monitors such as pulse oximeter, electrocardiograph, and noninvasive blood pressure monitor, i.v. access was obtained. Patients in both the groups received glycopyrrolate (0.2 mg), midazolam (2 mg), and fentanyl 2 μg.kg-1 body weight intravenously before the induction. Transtracheal block was given to all patients with 4 mL of 4% lignocaine, and following 3 min of preoxygenation, induction of general anesthesia was done with i.v. propofol (2–2.5 mg.kg-1) body weight till there was loss of response to verbal commands. After ensuring the ability to mask ventilate, suxamethonium 2 mg.kg-1 body weight was administered, and patients were intubated orally with 8 mm ID ETT for males and 7 mm ETT for females.
Anesthesia was maintained with isoflurane 1% in oxygen and air mixture (1:1) under intermittent positive pressure ventilation. Tidal volume of 6–8 mL.kg-1 and respiratory rate of 14–16 min-1 were used to maintain end-tidal carbon dioxide levels between 25 and 30 mmHg. A bite block was kept to prevent the patient biting, thereby blocking, the ETT intraoperatively in case the depth of anesthesia became inadequate at any time.
Following induction, patients of Group D received a bolus of dexmedetomidine 0.5 μg.kg-1 over 10 min followed by an infusion at the rate of 0.5 μg/kg/h. In the presence of hypotension, the rate of infusion was reduced to 0.3 μg/kg/h. In Group P, after induction, an i.v. infusion of propofol was started at the rate of 1 mg/kg/h based on lean body weight. In both the groups, if the patient moved, bucked on endotracheal tube, or if there were signs of inadequate depth of anesthesia such as tachycardia (heart rate [HR] >100/min) or hypertension (systolic blood pressure [SBP] >140 mmHg), the plane of anesthesia was deepened with a bolus of propofol 0.5 mg.kg-1 i.v. It was repeated in both the groups if required. The number of times propofol bolus was required was documented.
Bradycardia was defined as HR <60/min and was treated with glycopyrrolate (0.2 mg) or atropine (0.6 mg) i.v. according to the severity. Fall in SBP <90 mmHg was initially managed by the administration of i.v. fluid bolus of 200 mL. If not responding, the rate of dexmedetomidine infusion was reduced to 0.3 μg/kg/h in Group D and that of propofol to 0.8 mg/kg/h in Group P. If the fall in SBP lasted for more than 5 min, phenylephrine 50 μg boluses or ephedrine 3 mg incremental boluses were given i.v. in both the groups depending on the HR. Sustained hypotension was managed with noradrenaline infusion, the dose varying from 0.02 to 2 μg/kg/min as required.
HR, SBP, and mean arterial pressures were recorded before induction and then at 5, 10, 15, 30, 45, 60, 90, 120, 150, and 180 min after induction. The number of patient movements requiring propofol bolus administration, if any during surgery, was noted. In Group D, dexmedetomidine infusion was stopped 30 min before the end of the surgery, whereas in Group P, propofol infusion was stopped 10 min prior to the end of the surgery. Time to extubate was documented in both the groups which was defined as the time from discontinuing all anesthetics to the time of extubation.
Statistical analysis was performed using IBM SPSS Statistics 20.0 (Bengaluru, India). Mann–Whitney U-test was used to compare the demographics and hemodynamic parameters in both the groups. Fisher's exact test was used to compare the intraoperative patient movements in both the groups. Probability value (P)≤ 0.05 was considered statistically significant.
| Results|| |
Data of forty patients were analyzed in the present study [Table 1]. Demographic variables and distribution of ASA PS did not show any statistically significant difference between the groups [Table 2]. The mean HR and SBP were comparable in both the groups at all-time points [Figure 1] and [Figure 2]. Consumption phenylephrine and intraoperative propofol as bolus also were comparable in both the groups [Table 3]. However, the mean time to extubate was significantly higher in Group P compared to Group D (16.06 ± 5.78 vs. 9.61 ± 11.53 min, P = 0.001, [Figure 3] and [Table 3]). No patient in either group required administration of atropine or glycopyrrolate.
|Table 2: Comparison of demographics and the American Society of Anesthesiologist physical status|
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|Table 3: Comparison of extubation time, intraoperative consumption of propofol, and phenylephrine|
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| Discussion|| |
The classic anesthesia triad includes hypnosis, analgesia, and muscle relaxation. The use of nondepolarizing muscle relaxants improves surgical conditions by ensuring an immobile patient intraoperatively so that lower doses of volatile or i.v. anesthetics can be used, resulting in better hemodynamic stability. Surgeries such as brachial plexus repair, scoliosis, and parotidectomy require neuromuscular monitoring to test the integrity of nerves, and hence, the use of muscle relaxants is to be avoided which may necessitate the use of a higher minimum alveolar concentration (MAC) of volatile agents or an i.v. anesthetic agent to provide higher depth of anesthesia to keep the patient immobile during surgery.
Transtracheal injection of lidocaine has shown to be a better alternative to propofol and dexmedetomidine infusion in brachial plexus and parotid surgeries when nerve monitoring needs to be done.,, Transtracheal block anesthetizes the larynx and trachea and results in a reduction in need of anesthetic agents required to maintain adequate depth during the intraoperative period, as “MAC incision” is always less than “MAC intubation” for inhalational anesthetics. Hence, following transtracheal block, by abolishing stimuli from the trachea and larynx because of the presence of endotracheal tube, maintaining the depth of anesthesia at “MAC incision” will be enough to provide patient immobility.
Dexmedetomidine is a short-acting alpha 2 agonist with analgesic and sedative properties. The most frequent adverse events observed following administration of large bolus of dexmedetomidine are bradycardia and hypertension; however, slow infusions result in hypotension. Dexmedetomidine because of its stable cardiorespiratory profile, better sedation, and analgesic properties is proposed as a valuable adjunct for intraoperative sedation.
Propofol is an i.v. anesthetic agent used for the induction and maintenance of general anesthesia. Although recovery from propofol-induced anesthesia is generally rapid, the use of it for the maintenance of anesthesia is associated with depressant effects on the cardiovascular system manifesting as hypotension and bradycardia. In patients with myasthenia and muscular dystrophy, the use of propofol has been shown to provide adequate muscle relaxation., However, in normal patients to provide the same operating conditions without relaxants, higher doses will be required which will predispose to the development of adverse events. The use of high doses of propofol for prolonged periods carries the risk of development of propofol infusion syndrome which presents as refractory bradycardia leading to asystole, metabolic acidosis, rhabdomyolysis, hyperlipidemia, and fatty liver which carries a high mortality rate.
It was shown that dexmedetomidine when administered as an adjuvant of sevoflurane inhalational anesthesia improved the wake-up test quality and maintained hemodynamic stability during scoliosis surgery. The combination of anesthetics helps to reduce the dose requirement of both the drugs. The advantage of combining transtracheal block with the infusion of either propofol or dexmedetomidine is that doses of both i.v. and the volatile agents used can be reduced, thereby reducing adverse effects of these agents.
| Conclusion|| |
In view of significantly shorter extubation time, the use of dexmedetomidine infusion as an adjunct to transtracheal block is superior to propofol infusion in patients undergoing surgeries under general anesthesia without the use of long-acting neuromuscular blockers. However, both the agents provided comparable intraoperative hemodynamics and patient immobility.
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[Figure 1], [Figure 2], [Figure 3]
[Table 1], [Table 2], [Table 3]