Formulae and Quick Reference


Shunts



Valve Area



Coronary Artery Anatomy


Figure A-1. Coronary arteries.



PULMONARY


Dead space = Lung units that are ventilated but not perfused


Intrapulmonary shunt = Lung units that are perfused but not ventilated


Alveolar gas equation:



A-a gradient = PAO2 – PaO2 [normal A-a gradient ≈ 4 + (age/4)]


Minute ventilation ( V.E) = Tidal volume (  VT) × Respiratory rate (RR) (normal 4–6 L/min)


Tidal volume (VT) = Alveolar space (  VA) + Dead space (  VD)


Fraction of tidal volume that is dead space



NEPHROLOGY


Anion gap (AG) = Na – (Cl + HCO3) (normal = [alb] × 2.5; typically 12 ± 2 mEq)


Delta-delta (δδ) = [δ AG (i.e., calc. AG – expected)/δ HCO3 (i.e., 24 – measured HCO3)]


Urine anion gap (UAG) = (UNa + UK) – UCl



Osmolal gap (OG) = Measured osmoles – Calculated osmoles (normal <10)



Corrected Na in hyperglycemia


Estimate in all pts: Corrected Na = Measured Na +



However, δ in Na depends on glc (Am J Med 1999;106:399)


δ is 1.6 mEq per each 100 mg/dL ↑ in glc ranging from 100–440


δ is 4 mEq per each 100 mg/dL ↑ in glc beyond 440


Total body water (TBW) = 0.60 × IBW (× 0.85 if female and × 0.85 if elderly)



HEMATOLOGY




• PTT q6h after every change (half-life of heparin is ∼90 min)


•  PTT qd or bid once PTT is therapeutic


•  CBC qd (to ensure that Hct and plt counts are stable)


OTHER


Ideal body weight (IBW) = [50 kg (men) or 45.5 kg (women)] + 2.3 kg/in. over 5 ft



SENSITIVITY AND SPECIFICITY CALCULATIONS




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Aug 28, 2016 | Posted by in ANESTHESIA | Comments Off on Formulae and Quick Reference

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