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 & FE_Na < 1%
    - GI losses
    - Skin losses
    - Third spacing
  - Urine Na > 20 & FE_Na > 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 & FE_Na < 1%
    - Heart failure
    - Hepatic failure
  - Urine Na > 20 & FE_Na > 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)

Metabolism

Free Water Deficit (FWD)

Crystalloids

Rate of Fluid Administration

Parkland Formula of Fluid Requirement for Burns

Acid-Base Disturbances

Workup of Metabolic Acidosis

Workup of Metabolic Alkalosis

ECG Changes in Electrolyte Disturbances

Hypokalemia

Hyperkalemia

Hypocalcemia

Hypercalcemia

Sodium Correction for Hyperglycemia

Workup of Hyponatremia

Management of Hyponatremia

Workup of Hypernatremia

Etiology of Hypokalemia

Etiology of Hyperkalemia

Treatment of Hyperkalemia

Calcium Correction for Hypoalbuminemia

Presentation of Hypocalcemia

Etiology of Hypocalcemia

Presentation of Hypercalcemia

Etiology of Hypercalcemia {CHIMPANZEES}

Treatment of Hypercalcemia

Iron Disorders

Presentation of Iron Deficiency

Presentation of Hemochromatosis

Treatment of Hemochromatosis

Presentation of Copper Deficiency

Presentation of Wilson Disease

Treatment of Wilson Disease

Presentation of Zinc Deficiency

Electrolyte Changes in Cystic Fibrosis

Presentation of Vitamin Deficiency

Classic Triad of Wernicke Encephalopathy {CAO}

Etiology of Folate Deficiency

Etiology of Vitamin B12 Deficiency

Etiology of Vitamin K Deficiency

Harris-Benedict Adjustment of Energy Expenditure

Curreri Formula of Energy Expenditure for Burns

Glycogen Storage Diseases (GSD)

Lysosomal Storage Diseases (LSD)

Glycogenosis

Sphingolipidosis

Mucolipidosis

Mucopolysaccharidosis

Metabolic Disorders

Symptoms of Lesch-Nyhan Syndrome {HGPRT}

Metabolic Syndrome

Presentation of Hyperlipidemia

Medications for Hyperlipidemia {OECSNF}

Indications for Statin Therapy

Treatment of Morbid Obesity

Collagen Releated Diseases

Etiology of Marfanoid Habitus

Indications for Low-Protein Diet

Amyloidosis

Etiology of Vitamin B₁₂ Deficiency