Equations

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Basic
Pulse Pressure
PP = Systolic Blood Pressure - Diastolic Blood PressureBasic
Mean Arterial Pressure
MAP = 1/3 x Systolic Pressure + 2/3 x Diastolic PressureBasic
Mean Arterial Pressure
MAP = Cardiac Output x Systemic Vascular Resistance + Central Venous Pressure (usually 0)Basic
ASA Scoring
Table Available HereBasic
Revised Cardiac Risk Index
1 For CAD or PAD; 1 for CHF; 1 for CVD; 1 for IDDM; 1 for CKD (Cr>2); 1 if surgery is suprainguinal vascular, intraperitonial or intrathoracicBasic
Fluid Management
Intracellular volume
40% of Body WeightFluid Management
Interstitial volume
13% of Body WeightFluid Management
Intravascular volume
7% of Body WeightFluid Management
Classical Fluid Replacement
4-2-1 Rule: 4 ml/kg/hr for 1st 10 kg, 2ml/kg/hr for next 10-20 kg, 1 ml/kg/hr for each kg above 20 kgFluid Management
Pre-existing Fluid Deficits
Maintenance requirements x # of hours NPOFluid Management
Evaporative losses
Minimal tissue trauma (e.g Hernia repair): 1 ml/kg/hr; Moderate tissue trauma (e.g. cholecystectomy): 3 ml/kg/hr; Severe tissue trauma (e.g. Bowel Resection): 6 ml/kg/hrFluid Management
Estimated Blood Loss (EBL)
(Suction cannister - irrigation) + "laps"(100ml each) + 4x4 Sponges (10 ml each) + field estimateFluid Management
Volume loss by burns (Parkland Formula)
Volume = % Burn Surface Area x 4 ml/kg x weight(in kg)Fluid Management
Transfusion Therapy
Arterial O2 Content
CaO2 = O2.HB + Dissolved O2 = (Hb x 1.36 x SaO2/100) + (PaO2 x 0.003)Transfusion Therapy
Allowable Blood Loss
ABL = (Hct (start) - Hct (allowed)) x EBV {70 for males, 65 for females}/Hct(start)Transfusion Therapy
Volume to Transfuse
Volume = (Hct (desired) - Hct (current)) x EBV {70 for males, 65 for females}/Hct(transfused blood)Transfusion Therapy
Hypoxemia
Alveolar-arterial (A-a) Gradient
P(A-a)O2 = PAO2 - PaO2Normal(FIO2 = 0.21):<10 mm Hg; Normal(FIO2=1.00): <60 mm HgHypoxemia
Alveolar Gas Equation
PAO2 = FIO2(Patm - PH2O)-(PaCO2/0.8) ; Patm=760 PH2O = 47Hypoxemia
Arterial O2 Content
CaO2 = O2.HB + Dissolved O2 = (Hb x 1.36 x SaO2/100) + (PaO2 x 0.003)Hypoxemia
Mixed Venous O2 Content
CvO2= (Hb x 1.36 x SvO2/100) + (PvO2 x 0.003) ; SVO2=75%; PvO2 = 40Hypoxemia
O2 Delivery
DO2 = Cardiac Output x Arterial O2 ContentHypoxemia
O2 Consumption (Fick Equation)
VO2 = Cardiac Output x (Arterial O2 Content - Mixed Venous O2 ContentHypoxemia
O2 Consumption
VO2 = VExp * ( FIO2 - FEO2 )Hypoxemia
O2 Extraction Ratio
ERO2 = (VO2/DO2)x100Hypoxemia
SO2 PO2 anchor points
50% SO2 = 27 mmHg PO2; 75% SO2 = 40 mmHg PO2; 97% SO2 = 100 mmHG PO2Hypoxemia
Post-Op Nausea/Vomiting
Simplified Apfel Score
1 point each for: Female; Non-Smoker; History of PONV; Postoperative OpioidsPost-Op Nausea/Vomiting
Post-op Nausea Vomiting (PONV) Prophylaxis
by Apfel ScorePost-Op Nausea/Vomiting