A focused collection of 35 calculators, scores, and clinical references.
APACHE II Score: Explanation and Clinical Context The APACHE II (Acute Physiology And Chronic Health Evaluation II) score is a widely used ICU severity-of-disease classification system that sums abnormalities in 12 physiologic variables (the Acute Physiology Score, APS), adds age points, and adds chronic health points to provide an admission severity score (range 0–71). Higher scores correlate with higher hospital mo
APACHE-IV: Purpose, limitations, and clinical context APACHE-IV (Acute Physiology and Chronic Health Evaluation, version IV) is an updated severity-of-illness model developed from a very large multi-center ICU cohort to estimate hospital mortality and length of stay for critically ill adults. The original publication describes a multivariable logistic procedure using first-24-hour physiologic data, age, chronic healt
ARDS Severity Index (PaO₂/FiO₂): Explanation and Clinical Context The ARDS Severity Index uses the ratio of arterial oxygen partial pressure (PaO₂) to fractional inspired oxygen (FiO₂) to stratify patients with acute respiratory distress syndrome according to severity. A PaO₂/FiO₂ ratio >300 mmHg indicates no ARDS; 201-300 mmHg indicates mild ARDS; 101-200 mmHg indicates moderate ARDS; < 100 mmHg indicates severe ARD
: Explanation and Clinical Context Cardiac Index represents the cardiac output normalized to body surface area, allowing clinicians to interpret cardiac performance in a manner that accounts for differences in body habitus. This parameter provides a more individualized assessment of circulatory adequacy compared to cardiac output alone. It is expressed in liters per minute per square meter and is widely used in criti
Explanation and Clinical Context Cardiac Output represents the total blood volume ejected from the ventricles every minute. It is determined by multiplying Stroke Volume and Heart Rate and presented in liters per minute. The value reflects the effectiveness of the cardiovascular system in delivering oxygen and nutrients to tissues. Normal Cardiac Output typically ranges from four to eight liters per minute in healthy
Cardiac Output Deficit (COD): Clinical Explanation and Interpretation Cardiac Output Deficit represents the difference between the individualized target cardiac output and the patient’s measured cardiac output. It provides a quantitative measure of how far a patient’s current circulatory performance deviates from the expected requirement based on metabolic demand and body size. A positive COD indicates that the patie
Cardiac Power Output (CPO): Comprehensive Explanation and Clinical Context Cardiac Power Output is a hemodynamic parameter that quantifies the overall pumping capability of the heart by integrating both cardiac output and mean arterial pressure into a single measure. It reflects the amount of hydraulic energy delivered by the heart to circulate blood throughout the body, and it is expressed in Watts. Unlike isolated
Cardiac Power Output Index (CPO Index) Explanation and Clinical Context Cardiac Power Output Index is a hemodynamic parameter that reflects the amount of hydraulic power generated by the heart per unit of body surface area. It is calculated from Cardiac Power Output, which itself is derived from cardiac output and mean arterial pressure. Because it incorporates both flow and pressure components, the CPO Index provide
CardShock Risk Score: Explanation and Clinical Context The CardShock Risk Score is a validated prognostic tool developed in the multicenter European CardShock Study to estimate short-term (in-hospital) mortality in patients presenting with cardiogenic shock, including both acute coronary syndrome (ACS) and non-ACS aetiologies. It incorporates seven easily available clinical and laboratory variables at admission: age
CathLab Shock (CardShock-based) Score: Explanation and clinical context The calculator above implements the CardShock risk score items (age, altered mental status/confusion at presentation, prior MI or CABG, ACS aetiology, LVEF <40%, arterial lactate category, and eGFR category) using the original CardShock thresholds and point allocations. The CardShock score was developed in a prospective multicentre cohort to pred
Collapsibility Index and Distensibility Index: Explanation and Clinical Context The measurement of the inferior vena cava provides a noninvasive method to estimate right atrial pressure and to assess intravascular volume status. The collapsibility index compares the maximum diameter of the inferior vena cava during expiration with the minimum diameter during inspiration. A greater degree of collapse often reflects lo
Explanation and clinical context The CardShock score was developed from a multicenter cohort to predict short-term mortality in patients with cardiogenic shock of various etiologies and uses seven admission variables (age, confusion, previous MI/CABG, ACS as cause, LVEF, lactate and eGFR). The IABP-SHOCK II score was derived from the IABP-SHOCK II trial in AMI-related cardiogenic shock; it uses variables available at
CVP/PCWP Ratio Prognostic Index: Explanation and Clinical Context The CVP/PCWP Ratio Prognostic Index is used to evaluate right and left heart filling pressures in patients with advanced heart failure or cardiogenic shock. Central Venous Pressure (CVP) reflects right atrial pressure, indicating right ventricular preload and venous congestion. Pulmonary Capillary Wedge Pressure (PCWP) reflects left atrial pressure and
ECMOnet Score: Explanation and Clinical Context The ECMOnet score is a tool for evaluating the appropriateness and timing of veno-venous (VV) ECMO in acute lung failure. It incorporates clinical parameters such as age, PaO₂/FiO₂ ratio, APACHE II score, platelet count, and PaCO₂ levels to assess the severity of illness and predict outcomes. Higher scores indicate a lower likelihood of survival and may suggest the need
Explanation and Clinical Context The Fick principle is one of the most fundamental physiological methods used to determine cardiac output. This calculation is based on the relationship between oxygen consumption and the arteriovenous oxygen content difference. The method assumes that the uptake or release of oxygen by the tissues is equal to the product of blood flow and the arteriovenous oxygen difference. In clinic
IABP-SHOCK II Risk Score: Explanation and Clinical Context The IABP-SHOCK II Risk Score was developed to provide a simple and rapid risk stratification tool for 30-day mortality in patients with acute myocardial infarction complicated by cardiogenic shock undergoing early PCI. The six independent predictors included: age > 73 years, prior stroke, admission glucose > 191 mg/dL, creatinine > 1.5 mg/dL, arterial lactate
Lactate Clearance Index: Explanation and Clinical Context Lactate Clearance Index represents the rate at which elevated blood lactate levels decline over time following resuscitation efforts. It reflects the balance between tissue oxygen delivery and utilization, and thus serves as a dynamic marker of global tissue perfusion. A higher clearance indicates effective resuscitation and improved prognosis, while persisten
Left Atrial Pressure LAP Explanation and Clinical Context Left atrial pressure represents the pressure within the left atrium and provides an indirect assessment of left ventricular filling pressures. Echocardiography offers a non invasive method to estimate LAP through the ratio between transmitral early filling velocity and early diastolic mitral annular velocity. The E over e average ratio is strongly correlated w
ACS-MCS (Mechanical Circulatory Support) Score: Explanation and Clinical Context The ACS-MCS score is a simple, four-point risk score developed to predict 30-day all-cause mortality in patients with cardiogenic shock due to acute coronary syndrome who require short-term mechanical circulatory support (ST-MCS). The model assigns 1 point each for: age > 60 years, pre-ST-MCS lactate > 2.5 mmol/L, presence of acute kidne
Modified Shock Index (MSI): Explanation and Clinical Context The Modified Shock Index (MSI) is a refinement of the traditional Shock Index (SI), which is defined as the ratio of heart rate (HR) to systolic blood pressure (SBP). MSI replaces SBP with mean arterial pressure (MAP) in the denominator, thereby improving sensitivity and specificity in detecting hemodynamic instability. It is calculated as: MSI = Heart Rate
Parkland Formula Explanation and Clinical Context Parkland formula, also known as Baxter formula, is a widely accepted method for estimating initial fluid resuscitation requirements in patients with significant burn injuries. The formula uses two primary variables which are the patient weight in kilograms and the percentage of total body surface area affected by partial thickness or full thickness burns. The total ca
Pulse Pressure: Explanation and Clinical Context Pulse pressure is the numerical difference between systolic and diastolic blood pressure. It reflects the interaction between stroke volume, aortic compliance, and ventricular function. A normal pulse pressure in healthy adults is approximately forty millimeters of mercury, although this value may vary with age. A widened pulse pressure may indicate increased arterial
Quick SOFA (qSOFA) Score: Explanation and Clinical Context The Quick Sequential Organ Failure Assessment (qSOFA) score was proposed by the Sepsis-3 task force (Singer et al., 2016) as a simplified bedside tool to identify patients with suspected infection at greater risk for poor outcomes outside the intensive care unit. It uses three simple clinical criteria: respiratory rate > 22 breaths per minute, systolic blood
RESP Score (Respiratory ECMO Survival Prediction) for VV-ECMO: Explanation and Clinical Context The RESP Score is a validated tool developed to predict in-hospital survival in patients receiving veno-venous ECMO for severe respiratory failure. It incorporates patient age, immunocompromised status, duration of mechanical ventilation before ECMO, central nervous system dysfunction, presence of acute non-pulmonary infec
SpO2 FiO2 Percentage Respiratory Rate ROX Index Explanation and Clinical Context The ROX Index is a clinical tool used to predict the success of high flow nasal cannula therapy in patients with acute hypoxemic respiratory failure. It is calculated using the ratio of peripheral oxygen saturation to fraction of inspired oxygen divided by respiratory rate. A higher ROX Index reflects better oxygenation efficiency and lo
Simplified Acute Physiology Score II (SAPS II): Explanation and Clinical Context SAPS II is a validated intensive care unit (ICU) mortality prediction model designed to estimate the probability of hospital mortality based on physiological variables measured during the first 24 hours of ICU admission. It incorporates 17 parameters: 12 physiological variables, age, type of admission, and three underlying disease variab
SAVE Score (Survival After Veno-Arterial ECMO): Explanation and Clinical Context The SAVE score is a validated tool designed to predict in-hospital mortality for adult patients undergoing VA-ECMO for refractory cardiogenic shock. It incorporates multiple pre-ECMO variables, including age, body weight, underlying diagnosis, pre-ECMO organ failures, serum bicarbonate, peak inspiratory pressure, and duration of mechanic
SCAI Shock Stages: Explanation and Clinical Context The Society for Cardiovascular Angiography and Interventions (SCAI) shock stages provide a standardized framework for classifying the severity of cardiogenic shock from Stage A (At risk) to Stage E (Extremis). Stage A includes patients at risk but without hypoperfusion. Stage B shows early signs of shock without organ dysfunction. Stage C represents classic cardioge
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
SOFA (Sepsis-related Organ Failure Assessment): Explanation and Clinical Context The SOFA score quantifies the degree of dysfunction across six organ systems (respiratory, coagulation, hepatic, cardiovascular, neurologic, and renal) by assigning 0–4 points for each organ system, producing a total score ranging from 0 to 24. It was developed primarily as an objective tool to describe and track organ dysfunction in cri
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
Target Cardiac Output (CO): Explanation and Clinical Context Target cardiac output represents the estimated cardiac output required to maintain adequate systemic perfusion in relation to an individual's body surface area. The formula uses a standard cardiac index value of 2.2 liters per minute per square meter, which reflects the minimal cardiac index associated with preserved organ perfusion in hemodynamically stabl