Can Vena Cava Ultrasound Guided Volume Repletion Prevent Spinal Induced Significant Hypotension in Elective Patients?

Can Vena Cava Ultrasound Guided Volume Repletion Prevent Spinal Induced Significant Hypotension in Elective Surgical Patients? A Randomized, Case Control, Prospective Trial.

Aim of this study is to determine whether Inferior Vena Cava analyzed by trans-thoracic echocardiography is an effective method to guide titrated fluid repletion in non critical patients, in order both to decrease post procedural significant hypotension rate and to avoid unnecessary fluid overload in patients undergoing spinal anesthesia for elective surgical procedures

The setting is standard spinal anesthesia and corresponds to our first arm of the study, used as the control sample and statistical reference. During the induction phase, the patient is fitted with non-invasive blood pressure monitoring, three-lead ECG, pulse-oximetry and peripheral intravenous device. Data and vital signs are recorded and an infusion of crystalloid (NaCl 0.9% or Ringer's acetate) is given during the procedure until the beginning of the operation. Total amount of fluid is also recorded before and after the spinal anesthesia.

In addition to the current clinical standard, for the second arm of the study, a trans-thoracic echocardiography is performed before spinal anesthesia, with the aim of assessing the patient's volume status; the exam is performed to assess size and collapsing of the Inferior Vena Cava during breathing cycle. According to different pre-established parameters, the patient is defined as fluid-responsive or unresponsive. If the patient is not responsive, investigators proceed to spinal anesthesia; otherwise they proceed to administration of crystalloid bolus (500 ml of NaCl 0.9% or Hartmann's solution). The patient may receive another bolus so as to reach a non-responsive pattern for echocardiographic evaluation.

Inclusion Criteria:

• both sexes
• grater than 18 year old
• requiring spinal anesthesia
• classified according to American Society of Anesthesiology (ASA) level as 1, 2 or 3

Exclusion Criteria:

• patients required invasive blood pressure monitoring (arterial/pulmonary catheter, thermodilution catheter),
• patients show signs of pre-procedural hypotension (defined as two measurements of systolic arterial pressure less than 80 mmHg and/or mean arterial pressure less than 60 mmHg),
• patients unable to give informed consent to language barriers, mental retard or any reduction in own ability to understand or give their informed consent,
• patient in which is not possible to perform spinal anesthesia for patient's refusal or technical difficulties in sampling,
• patients with International Normalized Ratio (INR) greater than 1.5 and/or activated Partial Thrombin Time in therapeutic range (more than 1.5 - 2 times the patient's normal values) and/or anti-factor X activity in therapeutic range
• patients with thrombocytopenia less than 50 G/l.