Utility of Pleth Variability Index (PVI) in Predicting Spinal anaesthesia-induced hypotension in elderly patients: A prospective diagnostic test study

After approval from the Institutional Ethics Committee, PGIMER, Chandigarh, written informed consent will be obtained from all the patients before enrollment in this prospective diagnostic study.

 Pre anaesthesia evaluation

 Â· All the patients will undergo standard pre-anaesthesia checkups along with breath-holding time. Those patients who meet the inclusion and exclusion criteria will be included in the study.

 Before spinal anaesthesia

 Â·      Once the participant enters the operating theatre, he/she will be asked to lie supine on the table. Concurrently, the ASA (American Society of Anaesthesiologists) standard monitors and the Masimo Radical 7® (Masimo Corp., Irvine, CA, USA) devices will be attached to the patient within the operating room premises. A warming device will also be applied to the patient, and the preoperative fasting period will be recorded.

 Â·      Baseline parameters such as heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP), temperature, as well as baseline perfusion index (PI), and pleth variability index (PVI), will be recorded following a five-minute resting period.

 Â·      Subsequently, the individual will be instructed to perform a breathing manoeuvre by taking a deep exhalation followed by a peak inhalation and a 15-second breath hold immediately before administering spinal anaesthesia. We will record the second Pleth Variability Index (PVI) at this juncture.

 Â·      After recording 2nd PI and PVI values, intravenous crystalloid infusion will be started at the rate of 2 millilitres per kilogram per hour, will be initiated.

 Administration of spinal anaesthesia

 Â·      Under appropriate aseptic precautions, in the sitting position, the patient’s back will be painted with an antiseptic solution and draped. The antiseptic solution will be left to dry for a few minutes.

 Â·      Meanwhile, the drug (Heavy Bupivacaine 10mg + Fentanyl 25 mcg) will be loaded in a syringe for intrathecal injection, maintaining sterile conditions. L4-L5 intervertebral space will be identified using Tuffier’s line as a landmark that passes from the highest point on the iliac crests.

 Â·      Using 25G/26G Quincke’s spinal needle, a needle will be inserted in L3-L4 or L4-L5 intervertebral space through a midline or paramedian approach.

 Â·      After the free flow of CSF is seen, the syringe will be locked tightly to the spinal needle, and the drug will be administered intrathecally to the patient in the L3-L4  or L4-L5 intervertebral space.

 After spinal anaesthesia

·      After administration of sub-arachnoid block, NIBP(Non-invasive blood pressure) measurements will be cycled every 2 minutes for 10 minutes, followed by every 5 minutes till 30 minutes from spinal drug injection. The highest level of sensory and motor block will also be recorded.

·      A fall in MAP by 20% from baseline or SBP less than 80 mm of Hg at any of these time points will be considered anaesthesia-induced hypotension.

·      The hypotensive episode will be treated with an intravenous fluid bolus of 250 ml followed by phenylephrine 0.1 mics per Kg or Mephenteramine 3 to 6 mg boluses based on the heart rate and ongoing intravenous fluids if the hypotensive episode continues.

·      Duration of surgery and total intravenous fluid will also be documented.