Internal Jugular Vein and Spinal-induced Hypotension

Study design; Observational

1. Recruitment: Preoperative anesthetic and cardiovascular evaluation by the anesthesiology department as well as the cardiology department to define patients with predetermined criteria. Patients' medical history, blood tests (e.g. blood urea and cratinine) physical examination, electrocardiogram (ECG), and X-ray assessment are performed during the pre-operative assessment, supplemented by specific exams or tests (e.g. TTE, troponin or pro-BNP levels) as per the consultant cardiologists' recommendations. Consecutive sampling of aging patients (>70 years), who sustain trauma of the lower limb(hip fractures) undergoing an orthopedic surgical procedure (hip fracture repair) and planned spinal anesthesia. More specifically, patients included, are subjected to an orthopaedic surgical repair of a proximal femur fracture under spinal anaesthesia. All patients or their relatives provide a written consent to participate in the study.
2. Inclusion criteria/initial screening: Age>70 years. Nitrogen Urea/Creatinine>20.American College of Cardiology (ACC) stage I or II.

Exclusion criteria includes severe pulmonary hypertension/tricuspid regurgitation, tachycardia (heart rate \> 100 beats/min), atrial fibrillation. Additionally, all patients who has spinal anaesthesia and the maximum cephalad dermatomal extension of the sensory block is below T12 are excluded from the study. Arterial hypotension related to overt intra-operative bleeding (\>150 cc) or patients requiring blood transfusion, for any reason, is not considered in the statistical analysis.

1. Preoperative POCUS IJV ultrasonography To visualize both the right and left IJV a linear transducer with a 5-10 MHz linear probe is placed over the neck, and the IJV is measured just below the bifurcation of the sternal and clavicular heads of the muscle. The IJV measurements are performed on the transverse axis during spontaneous quiet, breathing. Patients with evidence of IJV thrombosis are excluded. IJV measurements included the maximum area at the end of expiration (IJVmax), the minimum area at the end of inspiration (IJVmin), the IJV collapsibility index (IJV-CI): [(IJVmax - IJVmin area)/IJVmax] and the ratio (R) of IJVmax-to-IJV-CI. Two examiners each performed all the measurements, generating two values; the mean of these values is used for analysis.
2. Anesthetic protocol and measurements. Spinal anesthesia is introduced with a single intrathecal injection of 0.75% (15 mg) plain ropivacaine using a 22 or 25-gauge needle with the patient in the lateral or sitting position. Intraoperative ECG, SPO2 and non-invasive blood pressure (measurements every two minutes) monitoring are routinely used. The non-invasive blood pressure is measured every 2 minutes and vital parameters are recorded continuously throughout surgery.

Patients experiencing a MAP (two consecutive measurements) less than or equal to 65 mmHg, or greater than or equal to 25% reduction of its baseline preoperative value is considered hypotensive Arterial hypotension related to bone cement application, intraoperative/postoperative bleeding with blood loss greater than 150cc or patients receiving blood transfusion for any reason are not considered in our statistical analysis.

The degree of sensory block (cold test) is assessed by an anesthesia staff not further involved in the study.

1. Follow up: Assessing hypotension due to spinal-anesthesia intraoperatively.
2. Statistical analysis Sample size: Previously, many echocardiographic indices have been used to predict spinal-induced hypotension. The collapsibility index of the inferior vena cava has showed an area under the curve in a receiver operating characteristic curve analysis between 0.77. We hypothesized, therefore, that the area under the curve of the IJV-CI would be at least 0.77 to predict spinal induced hypotension. We calculated the required sample size for the comparison of the area under a receiver operating characteristic curve with a null hypothesis value. Considering the α error of 0.05 with 90% power, 42 patients are needed. To allow for a possible 20% dropout rate, at least a sample size of 50 patients.