Abstract ID: A8

Abstract Title: Quantification Of Deafferentation Following Central Neuraxial Blockade

Authors: Abrar K¹, Mantha S², Srilata M³, Gopinath R⁴
Nizam's Institute Of Medical Sciences Hyderabad Andhra Pradesh India¹, Nizam's Institute Of Medical Sciences Hyderabad Andhra Pradesh India², Nizam's Institute Of Medical Sciences Hyderabad Andhra Pradesh India³, Nizam's Institute Of Medical Sciences Hyderabad Andhra Pradesh India⁴
Poster Type: Discussion

ABSTRACT BODY

Introduction: A constant finding noted in patients given central neuraxial blockade[CNB]is the tendency to fall asleep in the intraoperative period. This is attributed to deafferentation where in interruption of sensory input to central nervous system occurs. Deafferentation leads to sedation.
Bispectral index[BIS]facilitates objective assessment of sedation.

Aim: To assess the usefulness of bispectral index in objective evaluation of sedation following central neuraxial blockade.

Materials and Methods: After institutional approval and taking informed consent, this prospective study was carried out in 22 patients of either sex; not having disabling pain preoperatively. Premedicant drugs for anxiolysis were not given. Before anaesthesia, baseline BIS index was recorded. Patients were then given CNB. No adjuvants were added to the local anaesthetics administered for CNB. From the onset of anaesthesia, BIS was recorded at regular intervals of 10 minutes upto 1 hour or until the end of surgery which ever was earlier.
Non parametric analysis was performed for ordinal data. Parametric analysis was performed for linear data. Chi-square test was employed for categorical data. Analysis Anova for repeated measures was applied to evaluate the temporal trends.

Results: The study was performed in 22 cases. The mean (SD) baseline BIS value for all cases was 97.22 (1.412). The mean BIS (SD) values at 10, 20, 30, 40, 50 and 60 minutes were 94.55(5.13), 95.09(4.03), 94.55(5.00), 94.65(4.51), 92.75(6.80) and 93.35(5.58) respectively; p value being significant at 50 minutes (p=0.04).

Discussion: Though CNB does not provide narcosis element of anaesthesia triad, sedation has been observed in patients given CNB. Sedation is objectively measured with BIS index values. Temporal trend of BIS index in the present study show a decline at 10 minutes from the baseline values and BIS values from then onwards remain fairly constant at 10, 20, 30, and 40 minutes. Decrease in BIS index at 10 minutes and subsequent BIS values upto 40 minutes were found not to be statistically significant. Further decrease in BIS index as seen at 50 minutes is statistically significant (p=0.04).

Conclusion: BIS index values are found to be significantly reduced at 50 minutes following central neuraxial blockade in patients without preoperative disabling pain.

ATTACHED FILES

A8_bis.doc

Reg Anesth Pain Med 2005; 30(3):A8