The Relationship Between Spinal Anesthesia-Related Hypotension and Ultrasonography of Internal Juguler Vein in Cesarean Section

73 term pregnant women, older than 18 years undergoing elective cesarean section with spinal anesthesia were included the study. The exclusion criteria were high risk pregnancies who had chronic hypertension, preeclampsia, gestational diabetes, preterm pregnancy, pre-pregnancy obesity, or history of pregnancy complication and severe medical conditions such as pulmonary, liver and kidney disease. The women was then transferred to the operating theatre. Non-invasive blood pressure and heart rate was applied with the woman in the supine position with an estimated 15° left lateral table tilt to avoid aortocaval compression by the uterus. After a stabilisation interval of 3–5 min, baseline systolic blood pressure (SBP) and mean blood pressure (MBP) were recorded. We used the non-invasive oscillometric method. After measurements, the antero-posterior internal jugular vein (IJV) diameter was measured using M-mode during a respiratory cycle. In order to avoid changes in vein diameter unrelated to respiratory variation, gentle pressure by the Ultrasonograhy (USG) probe was used to collapse the IJV in order to distinguish it from the carotid artery, then the pressure was relieved to the USG probe-skin interface and attention was given to avoid influence of probe compression on IJV dimensions during the USG examination. Moreover, in order to avoid interference of probeto- vein angle, the IJV evaluation was performed by positioning the probe perpendicular to the skin and oriented orthogonally to the IJV short-axis diameter. Ultrasound measurements of IJV diameter with respiration, which include maximum diameter of the IJV (dIJVmax) at the end of expiration during spontaneous respiration and collapsibility index (CI), have been recorded. The IJV CI (%) was calculated as CI = (dIJVmax – dIJVmin)/dIJVmax and was expressed as percentage. All measurements were made by a single author to eliminate interobserver variability. Episodes of hypotension in the period after spinal anesthesia were defined by a more than 20% decrease in SBP from the baseline level or any recorded period of MBP lower than 60 mmHg. The MBP reading before IJV USG was defined as baseline. The duration of observation of each participant was 2 hour.