Predicting Postinduction Hypotension in Patients for Elective Surgery under General Anesthesia using a Preanesthesia Ultrasonography of the Subclavian Vein.

BACKGROUND

Estimating fluid status before surgery is not routine, but ultrasound can be used for this purpose. Previous studies have shown a correlation between collapsibility indices of the subclavian vein (SCV) and inferior vena cava (IVC). There is a limited data regarding the suitability of studying SVC for predicting hemodynamic events like hypotension during induction anesthesia. By studying SCV width variations prior to surgery, we hope to get an indirect estimate of the fluid status of the patient, which may predict the occurrence of postinduction hypotension during surgery.

METHODOLOGY: This was a prospective, observational, single-center study registered with the Clinical Trials Registry of India. Patients aged 18 years and above, with ASA physical status 1 or 2, undergoing elective surgery with general anesthesia (GA) and endotracheal intubation were enrolled as per inclusion criteria. There were two observers performing the procedure: observer 1 measuring the blood pressure every minute for 10 min and observer 2 doing the measurements of the SCV ultrasonographically. The measurements included SCVDmax, SCVDmin, and SCVCI, which indicate maximum and minimum diameters of the SCV and its collapsibility index. Measurements were taken both during spontaneous breathing, deep breathing, and after passive leg raising.

RESULTS

In total, 80 patients were recruited for the study, and these data were analyzed. Patients were analyzed into two groups: a hypotension group (defined by absolute mean arterial pressure (MAP) <65 mmHg or a drop in MAP by more than 30% from baseline) and a no hypotension group. There were no significant differences between the two groups for baseline heart rate ( P = 0.0673), SCV diameters (maximum and minimum diameters measured in spontaneous, deep, and during PLR), and collapsibility indices (for spontaneous, deep, and during PLR).

CONCLUSION

Preoperative measurements of SCV diameter and its collapsibility index during spontaneous breathing, deep breathing, and passive leg raising are not reliable to predict the occurrence of hypotension after induction of GA.