Sandbox/equations

Equations

Nephrology

• Anion gap = ([Na+] + [K+]) − ([Cl−] + [HCO3−])

we can simplify it to: Na-(Cl+HCO3) (Typically= 12±2mEq)

• Delta-delta(ΔΔ) = Δanion gap(calculated anion gap-expected)/ΔHCO3(24-measured HCO3)

• Urine anion gap = Urine anion gap is calculated by subtracting the urine concentration of chloride (anions) from the concentrations of sodium plus potassium (cations)= Na+ + K+ − Cl−

• Calculated osmoles = 2[Na+] + [Glucose]/18 + [ BUN ]/2.8 ,where [Glucose] and [BUN] are measured in mg/dL.

• Calculated osmolarity= 2 Na + Glucose + Urea (all in mmol/L)

• Osmolal gap= measured osmoles - calculated osmoles

• Estimated creatinine clearance =

• Glomerular filtration rate (GFR) = Urine concentration×Urine flow/Plasma concentration

• Fractional Excretion of sodium =

• Corrected sodium in hyperglycemia = measured Na + 2.4[(measured glucose-100)/100]

• Total body water = 0.60 × IBW(ideal body weight) (× 0.85 if female and × 0.85 if elderly)

• Free water deficit = 0.6 x weight (kg) x [(Current Na/140) - 1]

• Trans-tubular potassium gradient (TTKG) =

Cardiology

• Mean arterial pressure (MAP) = [Cardiac output(CO)×Systemic vascular resistance(SVR)] + Central venous pressure(CVP)

Or [systolic blood pressure(SBP)+(diastolic blood pressure(DBP)×2)]/3 in mmHg

• Cardiac Index (CI) = Cardiac output(CO)/ Body surface area(BSA)

Or (Stroke volume×Heart rate)/Body surface area in L/min/m²

• Stroke volume (SV) = Cardiac output(CO)/Heart rate(HR)

in mL/contraction

• Stroke volume index (SVI) = Cardiac index (CI)/ Heart rate (HR)

in mL/contraction/m²

• Systemic vascular resistance (SVR) =

in dynes×sec/cm5

• Pulmonary vascular resistance (PVR) =

in dynes×sec/cm5

• Cardiac output = Oxygen consumption/[hemoglobin×13.6]

13.6 is equal to (arterial oxygen saturation - mixed venous oxygen) in L/min