Equations Flashcards
Interstitial space deficit (hydration)
% dehydrated (as decimal) x BW (kg) x 1000 = mL to replace
Maintenance Fluid Therapy
40 - 60 mL/kg/day
K9 and Feline blood volume
K9 = 90 mL/kg
Feline = 55 mL/kg
Resting Energy Requirement
kcal/day
> 2kg and < 30kg = (BW[kg] × 30) + 70
< 2kg and > 30 kg = (70 × BW [kg])^0.75
Base Deficit
Normal HCO3 - Patient HCO3 = mEq/L
Sodium Bicarb supplementation
0.3 × BW (kg) × base deficit = mEq/L
base deficit = Normal HCO3 − patient HCO3
Anion Gap
(Na + K) - (Cl + HCO3) = mEq/L
Cations - Anions
Corrected Calcium
Measured Ca − alb (g/dL) + 3.5 = mg/dL
Corrected Sodium
Current Na +
[(pt glucose − 100) ÷ 100 × 1.6]
Calculated Osmolality
2 Na + (BUN ÷ 2.8) + (glucose ÷ 18)
Osmolar Gap difference
Measured osmolality – calculated osmolality
expected osmole gap for dogs = 0 to 1 and cats = 2
Effective Osmolality
2(Na) + (Glu ÷ 18)
Total Body Water
0.6 x BW (kg)
Free water deficit
0.6 × BW (kg) × ([current Na ÷ 140] – 1)
140 can be changed to target Na
150 for cats
Sodium adjustment rate
0.5 - 1.0 mEq/hr = MAX
use with Free water deficit to calculate water supplementation over time
Corrected Cl-
Measured Cl x
(Normal Na ÷ Measured Na)
K- Max
0.5mEq/kg/hr
Coronary Perfusion Pressure
Aortic diastolic pressure - R atrial diastolic pressure
CPP of at least 15 mmHg needed for ROSC to occur.
Pressure gradient that drives coronary blood pressure and is a surrogate for coronary blood flow.
Cerebral Perfusion Pressure
MAP - ICP
Mean Arterial Pressure (MAP)
CO x SVR
Cardiac Output (CO)
CO = HR x SV
Stroke Volume (SV)
Preload - Afterload + Contractility
CI / BW
N = 1.5–2.5 ml/beat/kg
Systemic Vascular Resistance (SVR)
(MAP - CVP) ÷ CI
CI = Cardiac Index (CO / BW)
N= 0.5–0.8 mmHg/ml/kg/min
Blood Pressure
Diastolic + [(Systolic - Diastolic) ÷ 3]
Arterial Oxygen Content (CaO2)
(1.34 × Hb × SaO2) + (0.003 × PaO2)
SaO2 = Arterial O2 saturation
N= 19–21 ml/dl
Delievery of Oxygen (DO2)
DO2 = CO x CaO2
ml/kg/min
Tissue Oxygenation (Oxygen extraction)
VO2 ÷ DO2
tissue O2 consumption ÷ delivery of O2
P/F Ratio
PaO2 ÷ FiO2
N= 476 (PaO2 = 100, FiO2 = 0.21)
Alveolar Partial Pressure of O2 (PAO2)
FiO2 (atm pressure - 47) -
(PaCO2 ÷ 0.8)
Atmospheric pressure @ sea level 760 mmHg
A-a Gradient
PAO2 - PaO2
N= < 15 mmHg
useful for room air assesment
assessing the oxygenation ability of the lungs while removing the effects of changes in minute ventilation (PaCO2)
calculated - measured
Minute Volume (MV or Ve)
MV = TV x RR
N= 150-250 mL/kg
Tidal Volume (TV or Vt)
Approx 10-20 mL/kg
Alveolar Ventilation (Va) in relation to Tidal volume
TV = Va + Vd
TV = sum of alveolar ventilation (Va) and anatomical dead space (Vd)
Lung Compliance
C =ΔV ÷ ΔP
change in volume divided by amount of pressure applied
Alveolar Ventilation (Va)
Va = (Vt - Vd) x RR
tidal volume - anatomical dead space
control amounts of CO2 in blood
FFP dosage
5-10mL/kg
PCV transfusion calculation
transfused vol (mL) = BW(kg) x 90mL* x (desired PCV - pt PCV ÷ donor PCV)
- or 70mL for cats*
1mL/kg will raise PCV by 1%
Lean Body mass
Normal BW x 0.8
Obese BW x 0.7
Thin BW x 0.1
Lactate effusion vs peripheral
difference of > 2mmol/L higher than peripheral suggestive of septic peritonitis
bacteria consume glucose and excrete lactate
Glucose effusion vs peripheral
Difference of > 20 mg/dL lower than peripheral suggestive of septic peritonitis
- bacteria consume glucose and eliminate lactate
Creatine measurment of effusion
Fluid : serum ratio >2:1 indicates uroabdomen
Potassium measurement of effusion
Fluid : serum ratio > 1.4:1 (dogs) and 1.9:1 (cats) indicates uroabdomen
Pulse pressure (digital palpation)
Systolic BP - Diastolic BP
Oxygen Index (OI)
MAP x FiO2 x 100 ÷ PaO2
Lower # = better lung function
means of evaluating oxygenation in ventilated pts
Shock Index (SI)
SI = HR ÷ Systolic BP
identifier for shock, esp for early compensatory
N = 0.37 - 0.9
Corrected BG for polycythemia
BG + ([1.6 x PCV] - 81.3)
Strong Ion Difference
(Na + K + Ca + Mg) - Cl - (other strong anions)
Stewarts strong Ion approach
the difference between cations and anions in plasma
Hematocrit
(MCV x RBC count) ÷ 10
Calulated Hemoglobin from PCV
PCV x 0.34
Hb makes up approximately 1/3 of a RBC
Ventilation
Physiological Dead Space
Vd/Vt = (PaCO2 -ETCO2) / PaCo2
Normal values (dogs): <40% (spontaneous breathing), <50% (positive pressure ventilation)
Physiological dead space = anatomical dead space + alveolar dead space
Anatomical dead space = TV of airways from nose/mouth to terminal bronchioles