Correlation of preoperative anxiety using modified Yale preoperative anxiety scale and requirement of anaesthetic depth using bispectral index in children undergoing herniotomy

Anxiety is a state of worry caused by the anticipation of external or internal danger .Preoperative anxiety is a common occurrence among children undergoing surgery and can result in adverse physiological and psychological reactions. It is a general observation that highly anxious child has lower depth of anaesthesia.

The modified Yale preoperative anxiety scale remains the gold standard to evaluate preoperative anxiety in children. It is an observational measure consisting of 22 items divided into 5 categories: activity, vocalisation, emotional expressivity,state of arousal and use of parent. The score ranges from 5 to 22. It is usually used in children between the age of 2 to 6 years. Few studies have shown the validity of this scale in children less than 2 years also.

the bispectral index[BIS] is used to measure the effects of anaesthetics and sedatives on the brain and consciousness. It uses a complex mathematical algorithm based on descriptive EEG parameters from the frontal cortex to suggest various levels of sedation. A sensor placed on the patient’s forehead, sends raw EEG waveforms to the monitor, where they are analysed. The BIS value is a single number based on the previous 15seconds of EEG data and is updated frequently. This value ranges from 100[completely awake] to 0[isoelectric EEG]. For deeper sedation[general anaesthesia] aim is to target BIS from 40 to 60.

The depth of anaesthesia and thus the BIS values are dependant on many factors, mainly type of surgical stimulus, type of airway devices used[endotrachial tubes or supraglottic airway devices],sedatives and analgesics used, dosage of intravenous and inhalational anaestheitcs used, supplementary regional blocks. Provided these factors are kept constant, we can study the relationship between preoperative anxiety and [using MYPAS] and depth of anaesthesia[using BIS]

In our institute we have a fairly standardized protocol of general anaesthesia with supraglottic airway devices plus caudal epidural block for children undergoing herniotomy. This study aim to find out correlation between preoperative anxiety (using MYPAS) and depth of anaesthesia (using BIS). The hypothesis is that, more the child is anxious in the preoperative period, more the BIS value, i.e, lighter the plane of anaesthesia or in other words more the anaesthetic dose required for the maintenance of anaesthesia.

Anesthetic requirment may vary according to age also. So in this study, we will find out if similar correlation is there in all age groups.