Equations

MAP = CO X SVR

CO = SV X HR

SVR = [(MAP – CVP)/CO] X 80

Arterial O2 content (CaO2) = Hgb X 1.34 X o2 saturation + (PO2 X .003)

O2 delivery = CO X arterial O2 content (CaO2) X 10

VO2 (O2 consumption) = CO X (CaO2 - CvO2 (venous o2 content))

Maximum dosing lidocaine 5 mg/kg, 7 mg/kg with epi. Bupivacaine 2 mg/kg, 3mg/kg with epi

• 1% lidocaine contains 10 mg/ml. Calculation for 70 kg male is: (5 mg/kg X 70 kg) / (10 mg/ml) = ml of lidocaine

Pulmonary capillary wedge pressure estimates left atrial pressure. > 15 suggest left heart failure

Percentage of expected weight loss after bariatric surgery = (Weight loss kg)/(excess weight)

Excess weight = Actual weight – Ideal body weight

Expected weight loss after surgery:

Adjusted body weight is needed for calculating caloric need in obese:

• Adjusted body weight = (actual body weight – ideal body weight) X (0.25) + ideal body weight

Ideal body weight for males: 106 + 6 lb for every inch above 5 // Or 50kg + 2.3kg for each inch above 5 ft

Women 100 + 5 lb for every inch above 5 OR 45.5 kg + 2.3 kg for each inch above 5 feet

TPN calorie calculation example

• 1000cc bag of TPN, which contains 20% dextrose and 7% protein and 250 cc of 20% lipid
• 0.2 X 1000 = 200 gm dextrose. 200 gm X 3.4 c/g = 640 calories
• 1000 X .07 = 70 gm protein. 70 gm X 4 = 280 calories
• 250 cc of 20% lipid = 50 gram of fat (0.2 X 250 = 50 grams fat)
• 50 gram of fat X 9 = 450 calories
• 20% fat emulsion has 2.0 kcal/cc
• 10% fat emulsion has 1.1 kcal/cc

Nutritional requirements for average healthy adult male 70kg

• Caloric requirement 25 kcalories/kg/day
• Protein requirement 1 g/kg/day
• Fat 9 calories/g
• Protein 4 c/g
• Carbs 4 c/g
• Dextrose 3.4/g
• 1500-1700 calories/day
• Protein 20% of calories. 20% should be essential AA
• Fat 30% of calories
• Carbs 50% of calories
• Trauma, sepsis or stress can increase kcal requirement by 20-40%
• Pregnancy increases it 300 kcal/day
• Lactation increases 500 kcal/day

Burn nutritional requirement – only for 2nd degree and above and at least 20% TBSA burn

• 25 calories/kg/day + 30 kcal X percentage burned 2nd degree and above.
• Protein: 1.5-2 g/kg/day + 3 g/day X percent burned
• Don’t exceed 3000 kcal/day

RQ respiratory quotient

• Ratio of CO2 produced to O2 consumed (CO2/O2) - measures energy expenditure
• Excess dextrose or overall energy can cause increase dependence to ventilator in those intubated
• RQ > 1 lipogenesis (overfeeding), tx: decrease calories and carbs.
• RQ < 0.7 ketosis and fat oxidation (starving),
• Pure fat (fatty acid) utilization = 0.7
• Pure protein utilization 0.8
• Pure carbs 1.0
• Balanced nutrition 0.825

Nitrogen balance

• 6.25 g protein contains 1 g of nitrogen.
• N in – N out = N balances
• (protein/6.25) – (24 hour urine nitrogen + 4) = Nitrogen balance
• Positive = anabolism. Negative = Catabolism

Total free water deficit = 0.6 (male) × weight (kg) × [(Serum Na-140/140)]

• 0.5 (women)
• This will = amount deficit in liters. Should replace HALF of this amount in next 24 hours
• Do not drop faster than 0.5-1 meq/L/hr

Plasma osmolarity = (2 X Na) + (glucose/18) + (BUN/2.8). Normal is 280-295

Hyperglycemia can cause pseudohyponatremia → for each 100 glucose over normal add 2 Na

Low albumin can cause pseudohypocalcemia = Serum Ca + 0.8 X [4-albumin]

• For every 1 g of decrease in albumin, add 0.8 to Ca

Anion gap: Na - (HCO3 + Cl); normal <12

Delta anion gap – in setting of high anion gap metabolic acidosis, delta gap checks to see if CO2 responded appropriately.

• = (change in anion gap from normal – change in CO2 from normal)
• < 1 = also has Non-gap metabolic acidosis, >1 also has metabolic alkalosis

FeNa –  (Urine Na/Cr) / (Plasma Na/Cr)  (UNa X PCr) / (PNa X UCr) X 100

• Contrast induced nephropathy = intrinsic kidney injury but has FeNa <1%, normal UOP, rise in Cr, and muddy brown cast
• Brown cast = ATN

Sensitivity – Test’s ability to detect disease = TP/(TP+FN)