Point of Care Ultrasound and Fluids Co-loading for the Prevention of Spinal-induced Hypotension in Dehydrated Elderly Patients and Cardiac Diseases

Elderly dehydrated patients (age>70 years) with proximal femur fracture scheduled for orthopedic surgical repair under spinal anesthesia were recruited. Patients' medical history, physical examination, electrocardiogram (ECG), and X-ray evaluation were performed during the preoperative assessment and supplemented by specific exams (e.g., troponin, pro-BNP levels, coronary angiography, myocardial perfusion scintigraphy, echocardiographic examination, or stress tests) as per consultant cardiologists' recommendations. Informed consent was obtained from the patients or their surrogates.

Based on cardiology consultation, the initial patient screening was used to identify those patients who were American Heart Association/American College of Cardiology (AHA/ACC) stage B or C whose cardiac disease status was compensated. Patients with tachycardia (heart rate > 100 beats/min), atrial fibrillation or left bundle branch block on ECG and those who diagnosed with moderate to severe or severe tricuspid or mitral valve regurgitation, severe aortic or mitral stenosis, severe pulmonary hypertension, right heart failure were not recruited. Patients who fulfilled the above criteria were scheduled for TTE examination prior to spinal anesthesia.

Baseline blood pressure measurements. In all the participants, the cardiovascular medication except for beta blockers was not given the day of surgery. Medications with standardized dose time once a day (e.g. angiotensin converting enzyme inhibitor) were discontinued 24 hours before surgery. Upon arrival in the operating room (preparation area), standard non-invasive monitoring (continuous ECG, non-invasive blood pressure measurements every three minutes and SPO2) was applied. Prior to placement of 20/18G intravenous and indwelling radial artery catheters, three consecutive MAP measurements were recorded, and their average was used as reference value.

Preoperative echocardiographic examination. After baseline MAP measurements and prior to spinal anesthesia induction, a complete TTE examination was performed which included the following views: parasternal long (LAX) and short axis (SAX), apical 4-chamber (4CH), including also the "RV-focused view", apical 2-chamber (2CH), apical 3-chamber (3CH) and subcostal IVC (SUB-IVC). All data were saved for off-line analysis. The physicians who analyzed the data were all competent at TTE. The LV-EF was estimated by the Simpson's method of discs by performing measurements of LV volumes in the 2CH and 4CH views. In suboptimal images, ultrasound contrast agents were used for the improvement of endocardial border definition. (SonoVue: Bracco, Milan, Italy and Optison: GE, Helthcare, USA).

To assess the function of the right ventricle (RV), the "RV-focused view" and the SUB-IVC views were acquired. The FAC, (2-dimentional surrogate for RV-EF) was calculated by the following formula: 100 × (RV-Area end-diastolic - RV-Area end-systolic) / RV-Area end-diastolic). Tricuspid regurgitation grading and velocity were assessed according to pertinent guidelines. LV filling pressures were estimated by the E/Em ratio (E=peak velocity of mitral flow in early diastole, Em=the average of peak velocities in early diastole of lateral and septal mitral annulus). Stroke volume (SV) and subsequent stroke volume index (SVI=SV/m2) of the LV were assessed using automated measurements of LV volumes, according to the formula SV = EDV-ESV, where EDV=end diastolic LV volume, and ESV=end systolic LV volume. From these data, we derived values for the assessment of cardiac output (CO) =SV x HR, and SVR =MAP x 80/CO, (MAP=mean arterial blood pressure, HR=heart rate). The IVC measurements included the IVC maximum diameter at the end of expiration (dIVCmax), the IVCCI during spontaneous, quiet, breathing [(IVC maximal diameter - IVC minimal diameter)/IVC maximal diameter], and the ratio of dIVCmax-to-IVCCI. All data were saved and stored digitally for off-line, postoperative analysis. All measurements were repeated twice (by a physician who were unaware of patients' hemodynamic status), and their arithmetical mean was taken for the analysis.