Ultrasound Assessment of the Subclavian Vein for Predicting Hypotension in Children After Anaesthesia Induction

To examine if ultrasound assessment of the diameter and collapsibility index of the SCV is correlated to fasting time and can be a predictor of post induction hypotension in children undergoing general anesthesia.

Design and setting: Prospective observational study in a day case surgical unit in a tertiary university hospital.

Patients: Children aged 0-18 years ASA 1-2 undergoing anesthesia for day case surgery after written and informed consent from parents is obtained according to local ethical permit. Exclusion criteria: ongoing medication for hypertension.

Measurements and results: Based on previous studies (Min Hee Choi et al. Eur J Anaesthesiol 2020; 37:474-481), a sample size of approximately 80 subjects will be needed. Data on fasting time will be collected after informed and written consent has been obtained. Before the induction of anesthesia, the patients will be breathing spontaneously in a supine position. Noninvasive blood pressure will be recorded. An ultrasound examination of SCV will then be performed on cross section of the vessel both in 2D and M-mode and the minimum and maximum diameters of the SCV will be recorded. Collapsibility index will then be calculated from these data as previously described (Min Hee Choi et al. Eur J Anaesthesiology 2020; 37:474-481). After this, the subjects will undergo anesthesia under which blood pressure will be recorded according to departmental standard as usual. SCV collapsibility index will then be investigated for potential significant correlation with fasting time and percentage decrease in blood pressure from baseline after anesthesia induction and during the surgical preparation phase, before start of surgery.