Study on evaluating the effect of Intravenous dexmedetomidine on depth of anaesthesia in patients undergoing lower segment cesarean section under general Anaesthesia

Inroduction & Aims: Awareness and recall causing posttraumatic stress disorder are the major hazards of General Anaesthesia in cesarean section because of exclusion of Benzodiazepines and opioids in the anaesthetic management before baby delivery. In this study, dexmedetomidine is used as a sedative & anxiolytic to abort awareness which was measured using BIS monitor. Materials and Methods: This study was carried on 50 parturient who were scheduled for elective cesarean section. They were divided into 2 groups. Group A patients received dexmedetomidine1mcg /kg IVas an infusion 10 min before induction. Group B patient received normal saline. Trend of BIS scores were observed at baseline, induction, intubation, skin incision, delivery, closure & extubation. Apgar score at 1 & 5 minutes were recorded. Isolated arm response by placing spygmomanometer cuff on Right forearm which was inflated before induction was also used to substantiate the presence of conscious awareness. Results: A median BIS score of 55ranging from42-68 with statistically significant value of P<0.05 was recorded on all occasions during surgery in the dexmedetomidine group. No statistical significance was observed in Apgar scores between 2 groups. Negative isolated arm response was noted in the dexmedetomidine group. Conclusion : The currently used GA technique was found to be inadequate to abort awareness before baby delivery. Thereforeby comparing the clinical outcomes like good apgar score and hemodynamic stability, the use of dexmedetomidine to abolish the awareness during caesarean section was considered as safe. © 2019 Published by Innovative Publication. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by/4.0/)


Introduction
Being Aware during General Anaesthesia is the biggest problem which is on increasing trend on recent studies, 1,2 in particular during cesarean section [3][4][5] because of withdrawal of opioids, sedatives, using low concentration of nitrous oxide& volatiles due to sedativeeffect & respiratory depression in neonates, until delivery .
Dexmedetomidine, a highly selective α 2 agonist which has sedative, analgesic & antisympathetic effect and produce conscious sedation without respiratory depression. Placental transfer and fetal metabolism of dexmedetomidine have been reported but there are no adverse effects on neonates, shown by apgar score.
In this study, dexmedetomidine is used to pr event awareness which was measured using BIS score & isolated forearm technique. 6

Materials and Methods
After obtaining ethical committee approval, an informed written consent obtained from all participants. This study included 50 full term parturients in the age group 21-30 years who were posted for elective cesarean section for different indications under General Anaesthesia. They were divided into 2 groups by sealed enveloped technique to receive 1mcg/kg IV dexmedetomidine 10 minutes before induction (Group A) or to not receive dexmedetomidine, For prophylaxis against aspiration, Inj. ranitidine 50 mg &Inj.perinorm 10mg i.v.were given 30 minutes before induction. Monitoring was done using ECG, NIBP, pulse oximetry, BIS monitor.
The person who supervised the anaesthesia ,explained the concept of study to patients and placed sphygmomanometer cuff around the Right arm of the patients after placing the cotton bandage and inflated it to 200 mm Hg immediately before induction. This technique isolated the Right sidearm from the effects of Neuromuscular blocking agents. Then the patient was presented with command, "open and close your Right hand". This was done every thirty seconds throughout the procedure til extubation. The cuff was deflated every twenty minutes to prevent ischemic paralysis.
After delivery of the baby, Inj.fentanyl 100mcg IV & Inj.midazolam 0.3mg/kg given. Sevoflurane administration stopped at start of closure of subcutaneous and N 2 O was then stopped at start of closure of skin.
BIS values & Isolated forearm responses were monitored. Apgar score were also recorded.

Results
Age and weight statistics (Demographic) data showed no significant difference between two groups. (Table 1)  Haemodynamic variables recorded during the entire anaesthesia procedure in both groups shown in Charts 2 and 3.

Discussion
In this study, it was found that dexmedetomidine succeeded significantly in aborting awareness & maintaining hemodynamic stability 7,8 & didn't affect the APGARscore .
Studies on the use of dexmedetomidine for cesarean section 9-11 are sparse. The available literature Nosaiba K.EZ Z El-Arab, salama I . EI-Hawary, Ashraf E.El-Zeftawy, RebabM. Mohammed 2017 , 220.225 shows use of dexmedetomidine with median BIS of 50 & didn't affect apgar score.
Dexmedetomidine, under the trade name Precedex among others, is an anxiety reducing, sedative, and also as an analgesic sometimes. Its is notable for its ability to produce sedation without producing much respiratory depression (unlike propofol, fentanyl and midazolam) and can provide cooperative or semi-arousable sedation. 12 Dexmedetomidine excite the presynaptic α 2 -AR, inhibit or reduce Norepinephrine release & stop pain signal transduction. It also excite postsynaptic α 2 -AR, lead to hyperpolarisation of neural cell Membrane& inhibit Norepinephrine release & inhibit sympathetic activity. Dexmedetomidine excites the presynaptic α 2 -AR of the nucleus ceruleus arousal response.
α2-Adrenergic Receptor agonists like dexmedetomidine produce clinical effects after binding to G-Protein-coupled α2 adrenergic receptors, of which there are three alpha subtypes (A, B, and C) with each having different physiological functions and pharmacological activities. These subtypes are found in peripheral, central, and autonomic nervous systems, as well as in major organs and blood vessels. 12 Dexmedetomidine is d-enantiomer of medetomidine 13 with highly selective alpha2 action (alpha2:alpha1=1600:1). Neither dexmedetomidine nor clonidine is totally selective for any of the α2receptor sub types, but dexmedetomidine seems to have increased α2Areceptor and α2C receptor affinity compared to clonidine.
Locus ceruleus of the brain stem is responsible for the sedative action, and spinal cord is the principal site for the analgesic action, both acting through α2A receptor. 14 In the heart, the predominant action of α2 adrenergic receptor is a decrease in heart rate through blocking cardioaccelerator nerve through subtype 2A and through vagomimetic action. In the peripheral vascular tissues, there is sympatholytic induced vasodilatation and smooth muscle receptormediated vasoconstriction.
Finding out whether a patient is conscious or awake while undergoing general anesthesia pose a major problem. 15 The limitations of current clinical methods to assess anesthetic adequacy have been well known. Mechanisms in the central nervous system that controlhigher functions likememory and consciousness may be anesthetized adequately, whereas spinal cord mechanisms that suppress movement to surgical stimulus may not be anaesthetised adequately. A direct method of evaluating consciousness is needed, rather than the current practice of monitoring hemodynamic changes or movement responses.
A machine or monitor that measures physiologic changes associated with the conscious state would be an improvement on current methods, which are dependent on responses that only indirectly reflect consciousness. The bispectral monitoring system, an Electroencephalogram derived data was introduced for clinical use in October 1996, as a technique for measuring depth of anaesthesia 16,17 induced by hypnotics and sedatives and as a guide for the administration of various drugs intraoperatively. Its use in clinical practice is increasing all over the world to prevent intraoperative awareness and is also recognised beyond the operating room to critical care units, accident and emergency units.
The isolated forearm technique, was originally described by Tunstall, in contrast to BIS detects the return of consciousness. 18,19 The use of this technique to identify recovery of response, in response toverbal commandsalong with the BIS monitoring enabled study of the association between return of consciousness and a quantitative, measurement of anesthetic adequacy.

Conclusion
The study concluded that loading dose of IV dexmeditomedine 1mcg/kg is effective in aborting awareness without affecting APGAR score. Dexmedetomidine, when given as a pre-anaesthetic medication and intraoperative infusion, decreases stress response to various noxious stimuli and maintains haemodynamic stability.

Source of Funding
None.

Conflict of Interest
None.