Metabolism

Free Water Deficit (FWD)

Parameter 0.6 × W × (Na ÷ 140 - 1)
W Weight (kg)
Na Serum sodium (mEq/L)

Crystalloids

Solution Na (mEq/L) K (mEq/L) Ca (mg/dL) Cl (mEq/L) Glucose (g/dL) pH
5% dextrose in water (D5W) 0 0 0 0 5 3.5 ~ 6.5
5% dextrose in normal saline (D5NS) 154 0 0 154 5 3.5 ~ 6.5
Normal saline (NS) 154 0 0 154 0 4.5 ~ 7
Ringer's lactate 130 4 1.35 109 0 6 ~ 7.5
Ringer's acetate 130 5 1 112 0 6 ~ 8

Rate of Fluid Administration

Weight (kg) Rate (mL/kg/h) Rate (mL/kg/d)
< 10 4 100
10 ~ 20 2 50
> 20 1 20

Parkland Formula of Fluid Requirement for Burns

Parameter W × TBSA × 4
W Weight (kg)
TBSA Total body surface area (%)
  • 1/2 in the 1st 8 hours
  • 1/2 in the next 16 hours

Acid-Base Disturbances

Disturbance pH HCO3 PaCO2
Metabolic acidosis ↓ (1°) ↓ 1.25 ΔHCO3
Metabolic alkalosis ↑ (1°) ↑ 0.75 ΔHCO3
Respiratory acidosis ↑ 0.1 ~ 0.4 ΔPaCO2 ↑ (1°)
Respiratory alkalosis ↓ 0.2 ~ 0.4 ΔPaCO2 ↓ (1°)

Workup of Metabolic Acidosis

  • Anion gap :: normal
    • Urine anion gap :: negative
      • Saline
      • Diarrhea
      • VIPoma
    • Urine anion gap :: positive {HARD}
      • Hypoaldosteronism
      • Adrenal insufficiency
      • Renal tubular acidosis (RTA)
      • Renal failure
      • Diuretics :: Acetazolamide & K-sparing diuretics
  • Anion gap :: high {MUDPILES}
    • Methanol
    • Uremia
    • Diabetic ketoacidosis (DKA)
    • Propylene glycol
    • Iron & Isoniazid
    • Lactate
    • Ethanol & Ethylene glycol
    • Salicylates

Workup of Metabolic Alkalosis

  • Urine Cl < 20 [Saline-responsive]
    • Vomiting
    • Cystic fibrosis
  • Urine Cl > 20 [Saline-resistant]
    • Normotensive
      • Diuretics :: Loop diuretics & Thiazides
      • Bartter syndrome
      • Gitelman syndrome
    • Hypertensive
      • Hyperaldosteronism
      • Liddle syndrome
      • Syndrome of apparent mineralocorticoid excess (SAME)

ECG Changes in Electrolyte Disturbances

Hypokalemia

  • Flattened T waves
  • U waves

Hyperkalemia

  • Flattened P waves
  • Widened QRS complexes
  • Peaked T waves
  • Sine waves

Hypocalcemia

  • Prolonged QT interval
  • Bradycardia

Hypercalcemia

  • Shortened QT interval
  • Tachycardia

Sodium Correction for Hyperglycemia

Parameter Na + 0.024 × (Glucose - 100)
Na Serum sodium (mEq/L)
Glucose Serum glucose (mg/dL)

Workup of Hyponatremia

  • Serum osmolality < 280 mOsm/kg [Hypotonic]
    • Volume status :: hypovolemic
      • Urine Na < 20 & FENa < 1%
        • GI losses
        • Skin losses
        • Third spacing
      • Urine Na > 20 & FENa > 1%
        • Diuretics
        • Adrenal insufficiency
    • Volume status :: euvolemic
      • Urine osmolality < 100 mOsm/kg
        • Polydipsia
      • Urine osmolality > 100 mOsm/kg
        • SIADH
        • Hypothyroidism
    • Volume status :: hypervolemic
      • Urine Na < 20 & FENa < 1%
        • Heart failure
        • Hepatic failure
      • Urine Na > 20 & FENa > 1%
        • Renal failure
  • Serum osmolality 280 ~ 295 mOsm/kg [Isotonic]
    • Hyperlipidemia
    • Hyperproteinemia
  • Serum osmolality > 295 mOsm/kg [Hypertonic]
    • Hyperglycemia

Management of Hyponatremia

Volume Status Management
Hypovolemic Normal saline
Euvolemic Fluid restriction
Hypervolemic Fluid restriction ± Diuretics

Workup of Hypernatremia

  • Urine osmolality < 600 mOsm/kg
    • Diabetes insipidus
    • Diuretics :: osmotic
  • Urine osmolality > 600 mOsm/kg
    • Urine Na < 25
      • GI losses
      • Skin losses
      • Seizures
      • Eexercise
    • Urine Na > 100
      • Fluids :: hypertonic saline

Etiology of Hypokalemia

  • Extra-renal losses
    • Vomiting
    • Cystic fibrosis
    • Diarrhea
    • VIPoma
  • Renal losses
    • Hyperaldosteronism
    • Renal tubular acidosis (RTA) :: type 1 & 2
    • Diuretics :: Acetazolamide & Loop diuretics & Thiazides
    • Bartter syndrome
    • Gitelman syndrome
    • Liddle syndrome
    • Syndrome of apparent mineralocorticoid excess (SAME)

Etiology of Hyperkalemia

  • Pseudohypokalemia
  • Insulin deficiency
  • β antagonists
  • Hypoaldosteronism
  • Adrenal insufficiency
  • Renal tubular acidosis (RTA) :: type 4
  • Renal failure
  • Diuretics :: K-sparing diuretics
  • High anion gap metabolic acidosis

Treatment of Hyperkalemia

  • Insulin & Glucose
  • β agonists :: Albuterol
  • Bicarbonate
  • Calcium
  • Polystyrene sulfonate: Kalimate & Kayexalate
  • Diuretics :: Loop diuretics

Calcium Correction for Hypoalbuminemia

Parameter 0.8 × (4 - Albumin) + Ca
Ca Serum calcium (mg/dL)
Albumin Serum albumin (g/dL)

Presentation of Hypocalcemia

  • Bradycardia
  • Paresthesia
  • Prolonged QT interval
  • Tetany
  • Chvostek sign
  • Trousseau sign

Etiology of Hypocalcemia

  • Chronic kidney disease
  • 1° Hypoparathyroidism
  • Vitamin D deficiency
  • Pseudohypoparathyroidism (PHP)

Presentation of Hypercalcemia

  • Tachycardia
  • Shortened QT interval
  • Weakness
  • Constipation
  • Polyuria
  • Kidney stones
  • Bone pain
  • Psychiatric overtones

Etiology of Hypercalcemia {CHIMPANZEES}

  • Calcium supplementation
  • Hyperparathyroidism
  • Hyperthyroidism
  • Iatrogenic
  • Immobility
  • Milk-alkali syndrome
  • Paget disease
  • Adrenal insufficiency
  • Acromegaly
  • Neoplasm
  • Zollinger-Ellison syndrome
  • Excess vitamin A
  • Excess vitamin D
  • Sarcoidosis

Treatment of Hypercalcemia

  • Hydration
  • Diuretics :: Loop diuretics
  • Calcitonin
  • Bisphosphonates
  • Corticosteroids
  • Dialysis

Iron Disorders

Disorder Fe Ferritin Transferrin [TIBC] Saturation = Fe ÷ TIBC
Thalassemia - - - -
Anemia of chronic disorders -
Iron deficiency anemia (IDA)
Lead poisoning
Sideroblastic anemia
Hemochromatosis
Pregnancy & OCP - -

Presentation of Iron Deficiency

  • Iron deficiency anemia (IDA)
  • Koilonychia
  • Pica
  • Plummer-Vinson syndrome
    • Dysphagia
    • Esophageal web
    • Squamous cell carcinoma
  • Restless legs syndrome (RLS)

Presentation of Hemochromatosis

  • Skin pigmentation
  • Cardiomyopathy
  • Hepatomegaly
  • Cirrhosis
  • Diabetes melitus
  • Hypogonadism
  • Arthropathy
  • Pseudogout

Treatment of Hemochromatosis

  • Phlebotomy
  • Chelation
    • Deferasirox
    • Deferoxamine
    • Deferiprone

Presentation of Copper Deficiency

  • ↓ Wound healing
  • Easy bruising
  • Brittle hair
  • Ataxia
  • Peripheral neuropathy
  • Sideroblastic anemia

Presentation of Wilson Disease

  • Kayser-Fleischer rings
  • Cirrhosis
  • Fanconi syndrome
  • Parkinsonism

Treatment of Wilson Disease

  • Zinc
  • Chelation
    • Penicillamine
    • Trientine

Presentation of Zinc Deficiency

  • ↓ Wound healing
  • Easy bruising
  • Alopecia
  • Dermatitis
  • Diarrhea
  • Male hypogonadism
  • Dysgeusia
  • Anosmia

Electrolyte Changes in Cystic Fibrosis

  • ↓ NaCl in lungs
  • ↓ NaCl in pancreatic ducts
  • ↑ NaCl in sweat glands

Presentation of Vitamin Deficiency

Vitamin Deficiency
A Night blindness
Xeroderma
Xerophthalmia
Bitot spots
B1 Dry beriberi
Wet beriberi
Wernicke encephalopathy
Korsakoff syndrome
Wernicke-Korsakoff syndrome
B2 {2C} Cheilosis
Corneal vascularization
B3 {3D} Dermatitis :: pellagra
Diarrhea
Dementia
B6 Homocystinuria
Sideroblastic anemia
Peripheral neuropathy
B7 Dermatitis
Alopecia
B9 Homocystinuria
Megaloblastic anemia
Neural tube defect
B12 Homocystinuria
Megaloblastic anemia
Methylmalonic acidemia
Subacute combined degeneration
C Scurvy
↓ Wound healing
Easy bruising
D Rickets
Osteomalacia
Hypocalcemia
Hypophosphatemia
E Hemolytic anemia
K Coagulopathy
Easy bruising

Classic Triad of Wernicke Encephalopathy {CAO}

  • Confusion
  • Ataxia
  • Ophthalmoplegia

Etiology of Folate Deficiency

  • Alcoholism
  • Crohn disease
  • Malabsorption syndromes
  • Drugs
    • Methotrexate
    • Phenytoin
    • Sulfonamides
    • Trimethoprim

Etiology of Vitamin B12 Deficiency

  • Achlorhydria
  • Crohn disease
  • Diphyllobothrium latum
  • Gastrectomy
  • Gastritis
  • Ileal resection
  • Malabsorption syndromes
  • Metformin
  • Pernicious anemia

Etiology of Vitamin K Deficiency

  • Biliary atresia
  • Broad-spectrum antibiotics
  • Crohn disease
  • Cystic fibrosis
  • Primary biliary cholangitis (PBC)
  • Primary sclerosing cholangitis (PSC)
  • Newborns
  • Steatorrhea
  • Vitamin E intoxication

Harris-Benedict Adjustment of Energy Expenditure

Condition Calorie (BEE) Protein (g/kg)
Sedentary 1.2 0.8 ~ 1
Postoperation 1.3 ~ 1.5 1.2 ~ 1.6
Burns 1.6 ~ 2.0 1.5 ~ 2

Curreri Formula of Energy Expenditure for Burns

Parameter 25 × W + 40 × TBSA
W Weight (kg)
TBSA Total body surface area (%)

Glycogen Storage Diseases (GSD)

Disease Defects Hypoglycemia Hepatomegaly Myopathy
Von Gierke disease Glucose-6-phosphatase + + -
Pompe disease α-1,4-Glucosidase :: lysosomal - + +
Cori disease Debranching enzyme + + +
Anderson disease Branching enzyme - + -
McArdle disease Glycogen phosphorylase :: musclular - - +
Hers disease Glycogen phosphorylase :: hepatic + + -

Lysosomal Storage Diseases (LSD)

Glycogenosis

Disease Defects Findings Hepatomegaly
Pompe disease α-1,4-Glucosidase - +

Sphingolipidosis

Disease Defects Findings Hepatomegaly
Gaucher disease Glucocerebrosidase Gaucher cell +
Niemann-Pick disease Sphingomyelinase Cherry-red spot +
Tay-Sachs disease Hexosaminidase Cherry-red spot -
Fabry disease α-Galactosidase Peripheral neuropathy -
Krabbe disease Galactocerebrosidase Leukodystrophy -
Metachromatic leukodystrophy Arylsulfatase Leukodystrophy -

Mucolipidosis

Disease Defects Findings Hepatomegaly
I-cell disease Phosphotransferase Corneal clouding +

Mucopolysaccharidosis

Disease Defects Findings Hepatomegaly
Hurler syndrome α-Iduronidase Corneal clouding +
Hunter syndrome Iduronate sulfatase - -

Metabolic Disorders

Disorder Defects Effects
Alkaptonuria (AKU) Homogentisate oxidase ↑ Homogentisic acid
Cystinuria Amino acid transporter ↓ COLA
Hartnup disease Amino acid transporter ↓ Tryptophan
Homocystinuria Cystathionine synthase ↑ Homocysteine
↓ Cysteine
  Methionine synthase ↑ Homocysteine
↓ Methionine
Lesch-Nyhan syndrome HGPRT ↑ Uric acid
Maple syrup urine disease (MSUD) Branched-chain α-ketoacid dehydrogenase ↑ α-ketoacids
Methylmalonic acidemia Methylmalonyl-CoA mutase ↑ Methylmalonic acid
Ornithine transcarbamylase deficiency Ornithine transcarbamylase ↑ Orotic acid
↑ Ammonia
↓ Urea
Orotic aciduria UMP synthase ↑ Orotic acid
↓ DNA
Phenylketonuria (PKU) Phenylalanine hydroxylase
Tetrahydrobiopterin
↑ Phenylalanine
↓ Tyrosine

Symptoms of Lesch-Nyhan Syndrome {HGPRT}

  • Hyperuricemia
  • Gout
  • Psychosis :: aggression & self-mutilation
  • Retardation :: intellectual disability
  • Dystonia

Metabolic Syndrome

  • Abdominal obesity
  • Hypertension: BP ≥ 130/85 mmHg
  • Hyperglycemia: FBG ≥ 100 mg/dL
  • Hypertriglycemia: triglyceride ≥ 150 mg/dL
  • Low HDL cholesterol
    • HDL < 40 mg/dL in men
    • HDL < 50 mg/dL in women

Presentation of Hyperlipidemia

  • Xanthomas
  • Xanthelasma
  • Corneal arcus

Medications for Hyperlipidemia {OECSNF}

Mechanism Medication LDL HDL Triglyceride
Pancreatic lipase inhibitors Orlistat ↓↓ - -
Cholesterol absorption inhibitors Ezetimibe ↓↓ - -
Bile acid resin Cholestyramine
Colestipol
Colesevelam
↓↓ - -
HMG-CoA reductase inhibitors Statins ↓↓↓
HSL & VLDL synthesis inhibitors Niacin (B3) ↓↓ ↑↑
LPL & PPAR-α inducers Fibrates ↓↓↓

Indications for Statin Therapy

  • History of arterial thromboembolism
  • LDL > 190 mg/dL
  • Age > 40 years & Diabetes mellitus
  • 10-year ASCVD risk > 7.5% ~ 10%

Treatment of Morbid Obesity

  • GLP-1 analogs
  • Orlistat
  • Phentermine-Topiramate
  • Bariatric surgery

Collagen Releated Diseases

Component Diseases
Type 1 collagen Osteogenesis imperfecta
Type 2 collagen -
Type 3 collagen Vascular Ehlers-Danlos syndrome (EDS)
Type 4 collagen Alport syndrome
Goodpasture syndrome
Type 5 collagen Classical Ehlers-Danlos syndrome (EDS)
Elastin α1-antitrypsin deficiency
Fibrillin Marfan syndrome

Etiology of Marfanoid Habitus

  • Marfan syndrome
  • Multiple endocrine neoplasia (MEN) 2B
  • Homocystinuria

Indications for Low-Protein Diet

  • Liver failure → Hyperammonemia
  • End stage renal disease (ESRD) → Uremia

Amyloidosis

Disease Amyloid Precursor
Primary amyloidosis Amyloid light-chain (AL) Immunoglobulin light-chain
Secondary amyloidosis Amyloid A (AA) Serum amyloid A (SAA)
Dialysis-related amyloidosis Amyloid β2-microglobulin (Aβ2M) β2-microglobulin (β2M)
DM type 2 Amyloid islet amyloid polypeptide (AIAPP) Islet amyloid polypeptide (IAPP)
Medullary thyroid cancer Calcitonin Calcitonin
Alzheimer disease Amyloid β (Aβ) Amyloid precursor protein (APP)
Creutzfeldt-Jakob disease Amyloid prion protein (APrP) Prion protein (PrP)
Familial amyloidosis Amyloid transthyretin (ATTR) Transthyretin (TTR)