After obtaining approval from the Institutional Ethics committee and informed consent, 120 diabetic patients undergoing elective surgeries under spinal anaesthesia will be included in this study. A thorough preoperative assessment will be done by the attending anaesthesiologist and history on duration and current treatment will be obtained. Anthropometric assessment will be done. Routine investigations like RBS, HbA1c, RFT, CXR, funds examination and ECG will be reviewed. Heart rate variability will be measured one day prior to surgery in the department of physiology. Premedication and diabetic medications will be prescribed as per the departmental protocol. 

On the day of surgery, after attaching all monitors and recording baseline parameters, preloading will be done with 15ml/kg of crystalloid solution. Spinal block will be performed in left lateral position at L3-L4 interspace and 0.5% bupivacaine 3ml will given. The level of sensory blockade will be tested with pinpricks at five-minute intervals and highest level attained will be noted. Haemodynamic parameters will be recorded throughout the intraoperative period. Any fall in blood pressure of more than 20% of the baseline will be considered as hypotension and treated with fluid bolus and Inj. Mephenteramine 6mg IV. Total vasopressor requirement will be noted. Fall in heart rate of less than 60 bpm will be considered as bradycardia and will be treated with Inj. atropine 0.6mg IV.

1. Measuring Heart rate variability:

Cardiac Autonomic Function Test will be measured one day prior to surgery in the physiology department. Anthropometric assessment will be done. After 15 min of supine rest on a couch in the autonomic function test (AFT) lab (room temperature maintained at 25 degree C), following CAF tests will be done in the order as mentioned below: 

1) Resting Heart rate 

2) Resting Blood pressure-Systolic BP and Diastolic BP 

3) Resting short term heart rate variability (HRV): Lead II electrocardiogram (ECG) will be recorded for 5 min for Heart rate variability analysis following the standard procedure using HRV acquisition system.  

4) Lying to standing test:

5) Isometric hand grip test:

6) Deep breathing test: 

HRV analysis software will be used to analyze the frequency spectrum components using fast Fourier transformation and time domain components in the RR trend.  Standard frequency – domain measurements includes total power (T.P.), HF (0.15–0.4 Hz), LF (0.04–0.15 Hz) and LF/HF ratio and time domain parameters include mean and standard deviation of RR intervals (SDNN), mean and standard deviation of HR(SDHR), square root of the mean of the sum of the squares of differences between adjacent RR interval (RMSSD), adjacent RR interval differing more than 50 ms (NN50) and NN50 counts divided by all RR intervals (pNN50). HF, HFnu, SDNN, RMSSD, NN50 and pNN50 reflect cardiovagal tone. Other parameters will be calculated from the data as per European Task force guidelines. (13)

1. Hemodynamic parameters:

1. Heart rate, systolic, diastolic and Mean Arterial Pressure (NIBP) at

• Baseline – Before preloading
• After preloading and before spinal anaesthesia.
• Every 2 mins for the first 10 mins.
• Every 5 mins till the end of the surgery,