Normal Labs

Lab	Low	High	Unit
Na	135	145	mEq/L
K	3.5	5	mEq/L
Mg	1.5	2.5	mg/dL
Ca	8.5	10.5	mg/dL
Ionized Ca	4.6	5.1	mg/dL
Phos	2.5	4.5	mg/dL
Bicarb	22	24	mEq/L
Osm	275	290	mOsm/L

$$\text{Osm} = 2*\text{Na}+\text{BUN} / 2.8 + \text{BG} / 18 + \text{EtOH} / 3.7 \\ \text{Na (mEq/L), BUN (mg/dL), BG (mg/dL), EtOH (mg/dL)}$$

Normal Fluid Repletion Rates

• 30-40 mL/kg QD (Adults)
• Holliday-Segar (Peds & Adults)
  • 100 mL/kg (1st 10kgs)
  • 50 mL/kg (2nd 10kgs)
  • 20 mL/kg (Remainder)
  • 1500 mL + 20 mL/kg * (Wt - 20kg) (for those greater than 20kgs)
• Monitor
  • Wt QD
  • I/Os and UOP
  • Volume Status QD
  • Vitals QD
  • BUN/SCr

Common Fluid Composition

Crytalloids

Soln	Osm	SID	Na	Cl	K	Ca	Mg	Lactate	Acetate	Free Water (mL/L)
NS	308	0	154	154	—	—	—	—	—	0
1/2 NS	154	0	77	77	—	—	—	—	—	500
3% Saline	1027	0	513	513	—	—	—	—	—	0
LR	274	28	130	109	4	3	—	28	—	0
D5W	252	0	—	—	—	—	—	—	—	1000
Normosol / Plasmalyte	295	50	140	98	5	—	3	—	27	0

*All lytes in mEq/L

Colloids

• Albumin 5%
  • 0.5-1 g/kg for hypovolemia at 2-4 mL/min (normal plasma volume) or 5-10 mL/min (hypoproteinemia)
• Albumin 25%
  • 5-8 g/L removed during paracentesis of > 5 L removed at 1 2-4 mL/min (normal plasma volume) or 2-3 mL/min (hypoproteinemia)

Blood Products

• PRBCs
  • 1 Unit = 230-350 mL
  • 1 Unit administration leads to an increase of 1 g/dL in Hgb

Daily Fluid Losses

Sensible	Amount (mL)	Insensible	Amount(mL)
Urine	400-1500	Skin	350-400
Defecation	100-200	Lungs	350-450
Total	1000-1500	Total	1000

Additional Sources of Fluid Loss

• NG Tube Suction
• D / V
• Burns
• Fistulas
• Drains
• Bleeding

Sodium

Hyponatremia

Hypertonic Hyponatremia

Most commonly caused by elevated BG. Treat BG and adjust Na once BG is controlled

$$\text{Corrected Na} = [\text{Na}] + 1.6\left( \frac{\text{BG}-100}{100} \right)$$

Pseudohyponatremia (Isotonic Hyponatremia)

Excessively high proteins and/or lipids leads to increased plasma volume. Dilution effects make sodium appear low, but measured Osm is relatively normal.

Hypovotonic Hyponatreamia

SSx

• Acute Hyponatremia
  • Nausea
  • HA
  • Malaise
  • Weakness
  • Disoriented
  • Coma
  • Szs
  • Respiratory Arrest
• Hypovolemic
  • Typical SSx of dehydration
• Isovolemic
  • Malaise
  • Psychosis
  • Szs
  • Coma
• Hypervolemic
  • Edema
  • Wt Gain

Treatment

Syndrome	Treatment
Hypovolemic	3% Saline (Symptomatic) NS (Asymptomatic)
Isovolemic	Furosemide and 3% Saline (Symptomatic) NS and Water Restriction (Asymptomatic)
Hypervolemic	Furosemide and Small Amounts of 3% Saline (Symptomatic) Furosemide (Asymptomatic)

• Replete Sodium Deficit: $\text{TBW}*(\text{Na}_{goal} - \text{Na}_{serum})$
• For non-emergent repletion, use the “Rule of 8’s”
  • 50% of deficit in 1st 8 hrs
  • 25% over following 16hr
• Replete at 1-2 mEq/L/hr until SSx resolution for emergent repletion
  • 3% Saline @ 1-2 mL/kg/hr x2-3hr if coma or Szs present
• NTE ≥ 8-12 mEq/L change Q24H to avoid Central Pontine Demyelination
• If presenting w/ Cerebral Edema and/or Metabolic Encephalopathy
  • Consider 50% repletion at 24hr and remaining over 48-72hrs

Monitoring

• [Na] Q2-4H until asymptomatic then Q4-8H until WNL
• Watch CV, Neuro, and Pulm function regularly over 1st 12hrs

SIADH

Diagnosis

• Urine Osm > 100 mOsm/kg
• Urine Na > 20-30 mEq/L

Causes

• Tumor
• Head Trauma
• Stroke
• Meningitis
• Drugs
  • Antipsychotics
  • Bromocriptine
  • Carbamazepine
  • Chlorprompamide
  • Cyclophosphamide
  • Desmopressin
  • Imipramine
  • Meperidine
  • Morphine
  • Nicotine
  • NSAIDs (Ibuprofen)
  • Oxytocin
  • SSRIs (Fluoxetine and Sertraline)
  • TCAs (Amitriptyline)
  • Tolbutamide
  • Vincristine
  • Vinblastine

Treatment

• Remove underlying cause if possible
• 1-2L Total Daily Free Water Restriction
• Vaptans if 24-48hr Free Water Restriction Fails
  • Conivaptan (Severe Symptomatic Eu- and Hypervolemic)
    • 20mg IV Bolus over 30min
    • 20mg over 24hr x2-4d (may increase Q24H to 40mg NTE 4d)
  • Tolvaptan (Asymptomatic Eu- and Hypervolemic)
    • 15mg PO QD (May increase Q24H to 60mg NTE 30d)
  • CIs
    • Hypovolemia
    • Anuria
    • Pts w/o sense of thirst
    • Strong 3A4 Inhibition

Hypernatremia

Classification and Causes

• Hypovolemic
  • Dehydration
  • Renal Fluid loss w/ Na preservation
  • GI Losses
  • Skin Losses
  • Adrenal Problems
• Isovolemic
  • Diabetes Insipidus
  • Osmotic Diuresis
  • Primary Polydipsia
  • Skin Losses
• Hypervolemic
  • Excess Na Ingestion
  • MC Excess

Treatment

• Hypervolemic
  • Remove offending fluid
  • Match I/Os
  • Diuretic if needed
  • If suffering from MC excess, consider MC antagonist
• Isovolemic (Central Diabetes Insipidus)
  • Desmopressin
    • Acute: 0.25-0.5 mL SubQ BID
    • Chronic: 0.05-0.2 mL Intranasal BID
  • Vasopressin
    • Continuous infusion titrated to goal UOP (checked hourly until at goal)
• Hypovolemic
  • Manage hemodynamics 1st
  • Correct Free Water Deficit: $\text{FWD} \approx \text{TBW} * \left( \frac{\text{Na}}{140}-1 \right)$
  • Give D5W IV or water via feeding tube
  • 50% of deficit in 24hrs, 50% over 24-48hrs

Monitoring

• [Na] Q3-6H x24hr
• After SSx resolution and normal [Na] Q6-12H
• I/Os
• Fluid Status Q24H

Potassium

Hypokalemia

Causes

• Diuretics
• β-Agonist Administration
• NG Drainage
• Metabolic Alkalosis
• Diarrhea
• Mg Depletion

SSx

• Weakness
• N/V
• EKG Changes
  • ST Depression
  • T Wave Depression
  • U Wave Prominence
  • Atrial and Ventricular Tachyarrhytmias
  • PVCs / PACs
  • VFib
• Cramping
• Muscle Weakness

Treatment

• Correct underlying Mg deficiency if existent
• K 3.5-4
  • No therapy usually needed
  • May be repeated to 4 in ICU pts
• K 3-3.4
  • PO for pts w/ cardiac conditions
  • In other pts, repletion is debatable
• K < 3
  • PO in asymptomatic
  • IV in symptomatic or those NPO

IV K

• K < 3 and SSx Present
• SEs
  • Thrombophlebitis
  • Hyperkalemia
• NTE 10 mEq/hr w/o cardiac monitoring
• NTE 20 mEq/hr w/ cardiac monitoring
  • Emergent can justify 40-60 mEq/hr if severe

Hyperkalemia

SSX

• EKG Changes
  • NOT ALWAYS PRESENT OR IN THIS ORDER, TREAT AGGRESSIVELY REGARDLESS OF SSX
  • Peaked T Waves
  • Wide Complex
  • Bradycardias
  • Long-QT
  • TdP
  • VFib

Treamtent

1. Cardiac Membrane Stabilization
   • CaCl 1g IVP Q20-30Min
   • Ca Gluconate 3g (Not for emergent treatment or those in hepatic failure)
2. Intracellular Ca Shift
   • Insulin Regular 10U IVP Q2-6H w/ 50 mL (25g) D50W IVP (unless BG is very high)
   • Bicarb 50-100mEq IVP Q2-6H (avoid in metabolic alkalosis, not useful in respiratory acidosis)
     • Bicarb cannot be used in ESRD pts
   • Albuterol 10-20mg Nebulized (Can be continuous, lasts 1-2hrs)
3. Potassium Excretion
   • Furosemide 20-40mg IVP Q4-6H (useless if K is high from renal failure)
   • 4hrs hemodialysis
   • SPS 15-60g PO or PR (has very poor evidence, avoid)
   • Patiromer (K Binder) 8.4g PO

Magnesium

Hypomagnesemia

Causes

• Diarrhea
• Amphotericine
• Diuretics (Loops and Thiazides)
• Cyclosporine
• EtOH

SSx

• Often masked by hypocalcemia or hypokalemia
• Tetany
• Convulsions
• Ventricular arrythmias
• Ataxia
• Szs
• Lethargy
• Confusion
• Nystagmus

Treatment

• PO
  • Milk of Mag 5-10mL PO QID
  • MgO 800mg PO QD or 400mg PO TID w/ food
• IV (Symptomatic or NPO)
  • Mg 1-2: 0.5 mEq/kg
  • Mg < 1: 1mEq/kg
  • 8 mEq = 1g
  • Infuse at 1g per hour
  • May take up to 48hrs to normalize

Hypermagnesemia

Causes

• Renal Failure
• Excessive Consumption of Mg containing laxatives
• Treatment of eclampsia

SSx

• Sedation
• Loss of Reflexes
• Lethargy
• Respiratory Paralysis
• Hypotension
• Heart Block
• “Slows everything down”

Treatment

• CaCl 1g IVPB repeated PRN for cardiac presevation
• IV Hydration (NS, 1/2 NS) 200 mL/hr and add 1-2g Ca
• IV Furosemide
• Dialysis
• Supportive care
  • Cardiac pacing
  • Pressors / Inotropes / Inopressors
  • Ventilation

Calcium

Assess via Corrected Calcium:

$$\text{Corrected Ca}^{2+} = \text{Ca}^{2+} + 0.8 \left( 4-\text{Alb} \right)$$

Hypocalcemia

Causes

• Mg Deficiency
• Large volumes of blood products
• Hypoalbuminemia
• Hypoparathyroidism
• Vit D Deficiency
• Thyroid Surgery
• Medications (Ex. Loops)

SSx

• Parasthesias
• Cramps
• Tetany
• Depression
• Anxiety
• Confusion
• Memory Loss
• Hallucinations
• Szs
• Hair Loss
• Weak nails
• Eczema
• Long-QT
• Bradyarrhythmias

Treatment

• Correct hypomagnesemia
• 1-3g PO Ca
  • CaCO₃ 650 mg PO QID = 1g Ca
• 100-300mg IV Ca over 5-10min
  • 1g CaCl = 3g Ca Gluconate = 270mg Ca
  • Gluconate prefered due to decreased risk of necrosis and extravasation
  • 1g Ca per hour
• May need to supplement Vit D
  • Calcitriol 0.25mcg PO QD or QOD
  • Can increase by 0.25mcg Q4-8W Max of 1mcg PO QD

Ca Salt	Route	Ca / g (mg)	Ca / g (mEq)
Carbonate	PO	400	20
Citrate	PO	211	10.6
Glubionate	PO	64	3.2
Lactate	PO	130	4.5
Phosphate	PO	230-400	11.5-20
Chloride	IV	270	13.5
Gluconate	IV	90	4.5

Hypercalcemia

Causes

• Cancer
• Primary Hyperparathyroidism
• Increased absorption / consumption
• Decreased renal elimination
• Increased bone breakdown

SSx

• Acute
  • Anorexia
  • N / V / C
  • Polyuria / Polydipsia
  • Nocturia
• Chronic
  • Metastatic Calcification
  • Nephrolithiasis
  • CKD
• Hypercalcemic Crisis
  • ARF
  • Obtunded
  • Coma
  • Arrhythmias

Treatment

• NS 200-300 mL/hr
  • Normal or moderate renal impairment
  • Pts are usually dehydrated
• Furosemide
  • Increase Ca loss and prevent fluid overload
• Calcitonin
  • 4 U/kg SC or IM Q12H (Max 8 U/kg Q12H)
  • CHF or moderate-severe renal impairment
  • Increases bone resorption and decreases renal reabsorption
• Bisphosphonates
  • If from bone breakdown
  • Pamidronate 30-90mg IV over 2-24hr
  • Takes ~2 days to decrease
• GCs
  • If multiple myeloma, leukemia, lymphoma, or sarcoidosis
  • Decreases GI absorption of CA
  • Interferes w/ Vit D metabolism => increased bone reabsorption and decreased osteoblast proliferation
  • Slow onset

Phosphate

Hypophosphatemia

Causes

• Decreased Intake
• Impaired Absorption
• Intracellular shifts (refeeding syndrome)

SSx

• Irritability
• Myalgia
• Rhabdo
• Paranoia
• Szs
• Coma
• Parasthesias
• Obtunded
• Acute Renal Failure
• Cardiomyopathy
• Arrhythmias
• Respiratory Failure
• Delerium
• Hemolysis
• WBC Dysfunction
• Plt Dysfunction

Treatment

• Phos 1-2 mg/dL: PO Phos-NaK 30-60 mmol QD in 2-3 divided doses
• Phos <1 (or symptomatic): KPhos (K < 4) or NaPhos
  • 1 mmol NaPhos = 1.33 mEq Na and Phos
  • 1 mmol KPhos = 1.47 mEq K and Phos
• Phos 2.3-2.9: 0.32 mmol/kg Phos
• Phos 1.6-2.2: 0.64 mmol/kg Phos
• Phos < 1.6: 1 mmol/kg Phos
• NTE 7 mmol/hr and consider K infusion rate

Hyperphosphatemia

Causes

• Renal Failure
• Hypoparathyroidism
• Excessive Intake

SSx

• Soft tissue calcification if $\text{Ca}^{2+} \times \text{PO}_4^{3-} > 60$
• Concurrent hypocalcemia

Treatment

• IV Ca if severe hyperphosphatemic
  • Follow guidelines above for hypocalcemia
• Decrease phosphate intake and GI absorption