1,329 calculators and references across 60 specialties, with formula confidence shown up front.
Serum Albumin Ascitic Albumin Serum Ascites Albumin Gradient SAAG Explanation and Clinical Context SAAG represents the difference between serum albumin concentration and ascitic albumin concentration. It is a validated method to classify the underlying mechanism of ascites formation and to guide diagnostic reasoning. A value of one point one g per dL or more indicates portal hypertension related etiologies because th
Shock Index (HR/SBP Ratio): Explanation and Clinical Context The Shock Index (SI) is a simple, bedside physiological ratio calculated by dividing the heart rate (HR) by the systolic blood pressure (SBP). It serves as a rapid and sensitive indicator of hemodynamic compromise and circulatory shock. A normal Shock Index typically ranges from 0.5 to 0.7. Values above 0.9 are considered abnormal and have been strongly cor
Simpson’s biplane method: explanation, clinical context and references The biplane method of disks (the modified Simpson’s rule) estimates left ventricular end-diastolic and end-systolic volumes from apical 4-chamber and apical 2-ch views; the ejection fraction (LVEF) is then calculated as EF = [(EDV − ESV) / EDV] × 100%. In routine practice the machine may report volumes from each apical view and clinicians commonly
Stroke Volume: Explanation and Clinical Context Stroke volume represents the amount of blood ejected by the left ventricle during each cardiac contraction. The most accurate non invasive method for calculating stroke volume in clinical practice uses pulsed wave Doppler at the left ventricular outflow tract. The calculation requires the cross sectional area of the outflow tract and the velocity time integral of the sy
Stroke Volume Index (SVi): Explanation and Clinical Context Stroke Volume Index is a hemodynamic parameter that describes the amount of blood ejected by the left ventricle during each cardiac contraction, adjusted to body surface area. This index refines the interpretation of stroke volume by incorporating patient size, making it a more accurate indicator of forward flow in individuals with significantly different bo
Systemic Vascular Resistance (SVR): Comprehensive Explanation and Clinical Context SVR represents the resistance encountered by blood as it flows through the systemic circulation. It reflects the interaction between vascular tone, blood viscosity, and vessel diameter. The calculation of SVR is derived from the relationship between perfusion pressure and cardiac output, expressed as the difference between mean arteria
Systemic Vascular Resistance Index (SVRi): Explanation and Clinical Context The systemic vascular resistance index represents the afterload imposed on the left ventricle after correcting for body surface area. It is derived from the transpulmonary pressure gradient, represented by mean arterial pressure minus right atrial pressure, divided by the cardiac index. SVRi provides a more individualized assessment of vascul