Comparison of utility of pre- operative ultrasonographic measurement of internal jugular vein diameter variation versus inferior vena cava diameter variation to passive leg raising in predicting hypotension following induction of general anaesthesia: a cross sectional study

A total of 330 patients who will be scheduled for elective surgery under general anesthesia in hospitals attached to Bangalore Medical College and Research Institute, the patients fulfilling the inclusion criteria will be included for this cross sectional study after obtaining informed consent (Annexure 1).

A thorough pre -anaesthetic evaluation will be done. Tab Alprazolam 0.5 mg will be prescribed to all patients on the night prior to surgery. On arrival to the operating theatre, routine monitors in the form of pulse oximetry, electrocardiogram and non -invasive blood pressure monitors will be applied. An intravenous line will be inserted and premedication, ondansetron 4 mg and ranitidine 50mg will be administered.

 IVC Ultrasonography

IVC evaluation will be done with patients in supine position after 5 minutes rest. Using curved probe ultrasound transducer adjusted to abdominal mode (SonoSite M-Turbo, Bothell, Washington, USA) will be placed in the subcostal area to visualize the IVC in the paramedian long -axis view. IVC will be  visualized using two-dimensional mode at the site where it enters the right atrium; then pulse wave Doppler will be used to distinguish if the viewed structure is IVC or aorta. All patients will be instructed to breathe, and through three breathing cycles, an average of three measurements will be obtained using curved probe and M-mode. Maximum IVC diameter (DIVCmax) and minimum IVC diameter (DIVCmin) will be obtained and recorded as DIVCmax1 and DIVCmin1 in the supine position. Collapsibility Index of DIVC(DIVC-CI) in the supine position will be calculated by the formula below and recorded as DIVC-CI1:

DIVC-CI1=(DIVCmax1-DIVCmin1)/DIVCmax1*100%

Patients then will be instructed to change their body positions for the PLR test, (trunk in supine position and legs elevated at 450) and the DIVCmax and DIVCmin will be measured again and recorded as DIVCmax2 and DIVCmin2, respectively. Collapsibility index calculation would be recorded as DIVC-CI2.

 DIVC-CI2=(DIVCmax2-DIVCmin2)/DIVCmax2*100%

DIVC expresses the change rate of DIVC by the PLR test, and will be calculated by the following formula:

DIVC=(DIVCmax2-DIVCmax1)/DIVCmax2*100%

IJV Ultrasonography

IJV measurements will be obtained in the supine position using a linear ultrasound transducer. Probe will be positioned horizontally at the middle level of thyroid cartilage. After obtaining a transverse clear view of the right IJV, antero- posterior diameter of IJV   will be measured using M- mode during three respiratory cycles and average of three measurements will be taken. The maximum value diameter of IJV(DIJVmax) and minimum value of diameter of IJV(DIJVmin) will be obtained as well and recorded as DIJVmax1 and DIJVmin1 in the supine position.

Collapsibility Index of DIJV(DIJV-CI) in the supine position would be calculated by the formula below and recorded as DIJV-CI1:

DIJV-CI1=(DIJVmax1-DIJVmin1)/DJVmax1*100%

Patients then will be instructed to change their body positions for the PLR test, and the DIJVmax and DIJVmin will be measured again and recorded as DIVCmax2 and DIJVmin2, respectively. Collapsibility index calculation would be recorded as DIJV-CI2.

DIJV-CI2=(DIJVmax2-DIJVmin2)/DIJVmax2*100%

DIJV expresses the change rate of DIJV by the PLR test , and will be calculated by the following formula:

DIJV=(DIJVmax2-DIJVmax1)/DIJVmax2*100%

 Induction of anesthesia

After all data is collected, GA will be induced by injecting 2mg/kg propofol and 2mcg/kg of fentanyl, then by injecting vecuromium (0.1 mg/kg) to aid endotracheal tube insertion. Mask ventilation is commenced with the cessation of spontaneous breathing. After 3 minutes of mask ventilation, endotracheal intubation will be performed. Then volume-controlled ventilation mode will be adopted, with tidal volume of 8-10 ml/kg of ideal body weight, respiratory rate of 12-16 times/min, the fraction of inspired oxygen (FiO2) at 50% and positive end-expiratory pressure (PEEP) at 5cmH2O.Anesthesia will be maintained with isoflurane, oxygen and air. HR and MAP will be measured every 1 min after anesthesia induction for first 15 mins. Crystalloid fluid infusion will be given. The documentation of study variables will end at this point and patient management will be continued further as per institutional protocol. The one who does ultrasonography will not be involved in the further study.

Any hypotension episode, defined as MAP more than 30% below the baseline reading, will be managed by intravenous bolus of fluids and ephedrine. Any bradycardia episode (defined as heart rate less than 55bpm) will be managed by atropine (0.01mg/kg).