fluids and electrolytes basics
TRANSCRIPT
+
Fluids and ElectrolytesIM 2013 (AVM)
+Outline
Potassium
Calcium
Magnesium
Phosphate
Creatinine and Renal Function
Water and Sodium
Bicarbonate
Inotropes
+
Basic Metabolic Panel
Na + Cl- BUN Ca++
Glu Mg++
K+ CO3-- Cr Phos--
3
+
POTASSIUM
+Potassium (K+)
Normal range: 3.5-4.5
Largely contained intra-cellular SK does not reflect total body K
Important roles: contractility of muscle cells, electrical responsiveness
Principal regulator: kidneys
5
+Potassium (K+)
Daily requirement 1-2 mEq/kg
Complete absorption in the upper GI tract
Kidneys regulate balance 10-15% filtered is excreted
Aldosterone: increase K+ & decrease Na+ excretion
Mineralocorticoid & glucocorticoid increase K+ & decrease Na+ excretion in stool
6
+Potassium (K+)
Acidosis Low pH shifts K+ out of cells (into serum) Hi pH shifts K+ into cells 0.3-1.3 mEq/L K+ change / 0.1 unit change in
pH in the opposite direction
7
+Hypokalemia
Hypokalemia <2.5: life threatening Common in severe gastroenteritis
8
+Causes of Hypokalemia
Distribution from ECF Hypokalemic periodic
paralysis Insulin, Β-agonists,
catecholamines, xanthine
Decrease intake
Extra-renal losses Diarrhea Laxative abuse Perspiration
Excessive colas consumption
Renal losses DKA Diuretics: thiazide, loop
diuretics Drugs: amphotericin B,
Cisplastin Hypomagnesemia Alkalosis Hyperaldosteronism Licorice ingestion Gitelman & Bartter
syndrome
9
+Hypokalemia: Presentation
Presentation Usually asymptomatic Skeletal muscle: weakness & cramps; respiratory
failure Flaccid paralysis & hyporeflexia Smooth muscle: constipation, urinary retention
ECG changes Flattened or inverted T-wave U wave: prolonged repolarization of the Purkinje fibers Depressed ST segment and widen PR interval Ventricular fibrillation can happen
10
+Hypokalemia: Presentation
11
Hypokalemia
- Flattened or inverted T-wave
- U wave: prolonged repolarization of the Purkinje fibers
- Depressed ST segment and widen PR interval
- Ventricular fibrillation can happen
+Hypokalemia: Treatment
Address the causes & underlying condition
Dietary supplements : leafy green vegetables, tomatoes, citrus fruits, oranges or bananas
Oral K replacement preferred
IV: KCl 0.5-1 mEq/kg over 1 hr (rate of 10 mEq/hr)
K Acetate or K Phos as alternative
Add K sparing diuretics
Correct hypomagnesemia
12
+Hypokalemia: Treatment
30cc Oral KCl = 40mEqs K
Kalium Durule = 10mEqs K
13
+Causes of Hyperkalemia
Hyperkalemia >6.5 – life threatening; Potential lethal
arrhythmias
Causes Spurious
Difficult blood draw hemolysis false reading Increase intake
Iatrogenic: IV or oral Blood transfusions
16
+Causes of Hyperkalemia
Decrease excretion Renal failure Adrenal insufficiency or
CAH Hypoaldosteronism Urinary tract
obstruction Renal tubular disease ACE inhibitors Potassium sparing
diuretics
Trans-cellular shifts Acidemia Rhadomyolysis; Tumor
lysis syndrome; Tissue necrosis
Succinylcholine Malignant
hyperthermia
17
+Hyperkalemia: Presentation
Neuromuscular effects Delayed repolarization, faster depolarization, slowing
of conduction velocity Paresthesias weakness flaccid paralysis
EKG changes ~6: peak T waves ~7: increased PR interval ~8-9: absent P wave with widening QRS complex Ventricular fibrillation Asystole
18
+Hyperkalemia: Presentation
19
+Hyperkalemia: Treatment
Lower K+ temporarily Calcium gluconate 100mg/kg IV Bicarb: 1-2 mEq/kg IV Insulin & glucose
Insulin 0.05 u/kg IV + D10W 2ml/kg then
Insulin 0.1 u/kg/hr + D10W 2-4 ml/kg/hr
Salbutamol (β2 selective agonist) nebulizer
Increase elimination Hemodialysis or hemofiltration Kayexalate via feces Furosemide via urine
Calcium: increases threshold potential decrease cardiac cell excitability
Bicarb: stimulate an exchange of cellular H+ for Na+, thus stim Na,K ATPase
Insulin: shift K into cells via Na,K-ATPase; last a few hours
Beta agonist: promote K shift into cells
20
+
CALCIUM
+Calcium
Normal range: 8.8-10.1 with half bound to albumin
Ionized (free or active)calcium: 4.4-5.4 – relevant for cell function
Majority is stored in bone
Hypoalbuminemia falsely decreased calcium (alb in g/L): Ca measured + [0.8 x (Albn – Alb m)]
(alb in g/dL): Ca measured + [(40 – Alb) x 0.02]
24
+Calcium
Roles: Coagulation Cellular signals Muscle contraction Neuromuscular transmission
Controlled by parathyroid hormone and vitamin D
25
+Hypocalcemia: Presentation
Neuromuscular irritability
Paresthesias: oral, perioral and acral, tingling or pin & needles
Tetany (Chvostek & Trousseau signs)
Hyperreflexia
Laryngospasm
Jittery, poor feedings or vomiting in newborns
ECG changes: prolonged QT intervals
27
+Hypocalcemia: Treatment
Supplements IV: gluconate or chloride with EKG change Oral calcium with vitamin D Calcium gluconate 10ml 10% wt/vol (90mg or
2.2mmol) IV, diluted in 50ml of 5%dextrose or 0.9%NaCl
Infusion: 10amps Ca gluc or 900mg Ca in 1L of D5 or 0.9%NaCl over 24hrs
Treat accompanying hypomagnesemia
28
+Hypercalcemia: Presentation
Groans: constipation
Moans: psychic moans (fatigue, lethargy, depression)
Bones: bone pain
Stones: kidney stones
Psychiatric overtones: depression & confusion
Fatigue, anorexia, nausea, vomiting, pancreatitis
ECG: short QT interval, widened T wave
30
+Hypercalcemia: Treatment
Fluid & diuretics 4-6L of IV saline may be needed in first 24hrs Forced diuresis with loop diuretic
Oral supplement: biphosphate or calcitonine Zoledronic acid (4mg IV over 30mins) Pamidronate (60-90 IV over 2-4hrs) Etidronate (7.5mg/kg/d for 3-7d) Onset 1-3days
Glucocorticoids IV hydrocortisone 100-300mg daily Oral prednisone (40-60mg daily for 3-7d)
Dialysis
31
+
MAGNESIUM
+Magnesium
Normal range: 1.5-2.3
60% stored in bone
1% in extracellular space
Necessary cofactor for many enzymes
Renal excretion is primary regulation
33
+Hypomagnesemia: Presentation
Weakness, muscle cramps
Cardiac arrhythmias Prolonged PR, QRS & QT Torsade de pointes Complete heart block & cardiac arrest with level >15
CNS: irritability, tremor, athetosis, jerking, nystagmus
Hallucination, depression, epileptic fits, HTN, tachycardia, tetany
36
+Hypomagnesemia: Treatment
Oral or IV supplement Oral MgCl2, MgO, Mg(OH)2: in divided doses
totalling 20-30mmol/d (40-60meq/d) IV MgCl2 as infusion of 50mmol/d (100meq/d) May also give MgSO4 IV
Correct ongoing loss
Correct for calcium, potassium, and phosphate as well
37
+Hypermagnesemia Presentation
Weakness, nausea, vomiting
Hypotension, hypocalcemia
Arrhythmia and asystole
4.0 mEq/L hyporeflexia
>5 prolonged AV conduction
>10 complete heart block
>13 cardiac arrest
39
+Hypermagnesemia: Treatment
Magnesium-free cathartics or enemas
IV hydration
Calcium infusion IV in doses of 100-200 over 1-2hrs
Diuretics
Dialysis
40
+
PHOSPHORUS
+Phosphorus
Normal range: 2.3 - 4.8
Most store in bone or intracellular space
<1% in plasma
Intracellular major anion, most in ATP
Concentration varies with age, higher during early childhood
Necessary for cellular energy metabolism
42
+Hypophosphotemia
Presentation: Muscle dysfunction and weakness: diploplia, low CO,
dysphagia, respiratory depression AMS WBC dysfunction Instability of cell membrane rhabdomyolysis
Treatments Supplementation with IV as neutral mixtures of Na and
Phos salts Oral phosphate 750-2000mg in divided doses Necessary to avoid Ca-Phos product >50 Correct hypocalcemia
46
+Hyperphosphotemia
Presentation: Tetany, seizures, accelerated nephrocalcinosis,
pulmonary and cardiac calcifications (mainly due to widespread calcium phosphate precipitates)
Treatments Limited Volume expansion Aluminum hydroxide antacids or sevelamer for
chelating Hemodialysis
47
+Creatinine and Renal Function
+BUN/CREA RATIO
BUN / Crea x 247
> 20:1 prerenal azotemia
10-15:1 oliguric acute renal failure
+Creatinine Clearance Estimation (Cockcroft-Gault)
Female = Male x 0.85
(lower fraction of body weight is muscle the metabolism of which yields creatinine)
+
CKD Stage
Description GFR mL/min/1.73
m2
1 Kidney damage w/ normal / increased
90
2 GFRKidney damage w/ mildly decreased
60-89
3 GFRModerately decreased GFR
30-59
4 Severely decreased GFR 15-29
5 Renal failure < 15 (or dialysis)
+
WATER and SODIUM
+Sodium (Na+)
Bulk cation of extracellular fluid change in SNa reflects change in total body Na+
Principle active solute for the maintenance of intravascular & interstitial volume
Absorption: throughout the GI system via active Na,K-ATPase system
Excretion: urine, sweat & feces
Kidneys are the principal regulator
54
+Sodium (Na+)
Kidneys are the principal regulator 2/3 of filtered Na+ is reabsorbed by the proximal
convoluted tubule, increase with contraction of extracellular fluid
Countercurrent system at the Loop of Henle is responsible for Na+ (descending) & water (ascending) balance – active transport with Cl-
Aldosterone stimulates further Na+ re-absorption at the distal convoluted tubules & the collecting ducts
<1% of filtered Na+ is normally excreted but can vary up to 10% if necessary
55
+Sodium (Na+)
Normal SNa: 135-145
Major component of serum osmolality Sosm = (2 x Na+) + (BUN / 2.8) + (Glu / 18) Normal: 285-295
Alterations in SNa reflect an abnormal water regulation
56
+Sodium (Na+)
Hyponatremia Na+<135 Seizure threshold ~125 <120 life threatening
57
+Hyponatremia: Presentation
Cellular swelling due to water shifts into cells
Anorexia, nausea, emesis, malaise, lethargy, confusion, agitation, headache, seizures, coma
Chronic hyponatremia: better tolerated
59
+Hyponatremia: Treatment
Rapid correction central pontine myelinolysis
Goal 12 mEq/L/day
Fluid restriction with SIADH
Hyponatremic seizures Poorly responsive to anti-convulsants Hypertonic saline Need to bring Na to above seizure threshold
60
+Causes of Hypernatremia
Excessive intake Improperly mixed formula Exogenous: bicarb, hypertonic saline, seawater
Water deficit: Central & nephrogenic DI Increased insensible loss Inadequate intake
62
+Causes of Hypernatremia
Water and sodium deficit GI losses Cutaneous losses Renal losses
Osmotic diuresis: mannitol, diabetes mellitus Chronic kidney disease Polyuric ATN Post-obstructive diuresis
63
+Hypernatremia: Presentation
Dehydration
“Doughy” feel to skin
Irritability, lethargy, weakness
Intracranial hemorrhage
Thrombosis: renal vein, dura sinus
64
+Hypernatremia: Treatment
Rate of correction for Na+ 1-2 mEq/L/hr
Calculate water deficit Water deficit = 0.6 x wt (kg) x [(current Na+/140) – 1]
Rate of correction for calculated water deficit 50% first 12-24 hrs Remaining next 24 hrs
65
+Sodium (Na+)
Urine Outpu
t
SerumNa
UrineNa
Serum Osm
UrineOsm
DI
SIADH
CSW
+Serum or Plasma Osmolality
2Na + Glu + BUN
Normal 280-290 mosmol/kg
Use in plasma osmolal gap
+Urine Osmolality (mosmol/kg)
2 (urine Na + urine K) + urine urea +
urine glucose
Use in urine osmolal gap
+Water Deficit
= [(Plasma Na – 140) / 140] x total body water in hypernatremia due to water loss
[(Plasma Na – 140) / 140] x
[(0.5 in men or 0.4 in women)
x lean body weight] Use in hypernatremia due to water loss, but should
be corrected slowly over at least 48-72h, ideally w/ hourly serum Na determination to target 0.5 mmol/L/h but not > 12 mmol/L over the 1st 24h.
+Ideal Body Weight
For men = (106 lb for the first 5 ft + 6 lb for each inch above 5 ft) / 2.2 lb/kg
For women = (100 lb for the first 5 ft + 5 lb for each additional inch) / 2.2 lb/kg
+24-hr Urine Collection Adequacy Creatinine is produced at a constant rate & in
an amount directly proportional to skeletal muscle mass
Creatinine coefficient = 23 mg/kg of ideal body weight in men & 18 mg/kg of IBW in women
If 24 h urine creatinine < IBW x creatinine coefficient inadequately collected specimen
Unpredictable when serum crea > 530 umol/L
+
FLUIDS
+Crystalloids
SOLUTIONS pH Osm
Kcal
Na K Cl Ca
Mg
Lactate
Acetate
(A) ISOTONIC
1. PNSS 5.7 308 - 154
- 154
- - - -
2. D5NSS 4.2 560 200 154
- 154
- - - -
3.D5NR 5.4 552 200 140
5 98 - 3 - 27
4. D5 Eurosol-R 4.6-6.5
552 200 140
5 98 - 3 - 50
5. D5LR 5.3 527 200 130
4 109
3 - 28 -
6. D5 Euromed LR
3.5-6.5
525 200 130
4 109
2.7
- 28 -
7.D5 LVP LR 3.5-5.0
586 200 147
4 158
2.2
- 28 -
8.Plasmasol 148 4-6 547 200 140
5 98 - 3 - 27
+
SOLUTIONS pH Osm
Kcal
Na
K Cl Ca
Mg
Lactate
Acetate
(B) HYPOTONIC
1.D5NM 5.2 368 200 40 13
40
- 3 - 16
2. D5 Eurosol 4.5-6.5
368 200 40 13
40
- 3 - 16
3.D5 Ionosol MB 4.7 350 200 25 20
22
- 3 23 -
4.D5 Eurolon 4.6-6.5
350 200 25 20
22
- 3 23 -
5. Plasmasol 48 4-6 348 200 25 20
24
- 3 23 -
6. D50 .45 Euromed
3.5-6.5
408 200 77 - 77
- - - -
+
BICARBONATE
+Bicarbonate
Normal range: 25-35
Important buffer system in acid-base homeostasis
Increased in metabolic alkalosis or compensated respiratory acidosis
Decreased in metabolic acidosis or compensated respiratory alkalosis
0.15 pH change/10 change in bicarb in uncompensated conditions
79
+Indications for HCO3 Therapy
pH < 7.2 and HCO3 < 5 – 10 mmHg
When there is inadequate ventilatory compensation
Elderly on beta blockers in severe acidosis with compromised cardiac function
Concurrent severe AG and NAGMA
Severe acidosis with renal failure or intoxication
+Complications of HCO3 Therapy
Volume overload
Hypernatremia
Hyperosmolarity
Hypokalemia
Intracellular acidosis
Causes overshoot alkalosis
Stimulates organic acid production
tissue O2 delivery
NaHCO3 50 ml = 45 mEq Na
NaHCO3 gr X tab = 7 mEq Na
+Bicarbonate Deficit
= HCO3 space x (desired HCO3 – measured HCO3)
(0.5-0.8* x body weight in kg) x (24** – measured HCO3)
* increases w/ increasing severity of the acidosis, normally 50% of body weight but increases to 80% in severe acidosis as a reflection of the total body buffering capacity.
** For severe acidosis < pH 7.20 in pure HAGMA, goal is to increase HCO3 to 10 mEq/L & pH to 7.15.
+
Goal is to increase plasma HCO3 slowly to 20-22 mEq/L. Notice that the formula uses 24 as the normal bicarbonate.
It tells us what the deficit is, but not what we should give the patient.
We still follow the targets for the above conditions (i.e., use them instead of 24). HCO3 therapy does not come without complications.
+
SHOCK and INOTROPES
+Dobutamine (ugtts/min)
desired dose x body weight in kg / (16.6 *
strength)
Desired dose 2-20 mcg/kg/min
For dobutamine 250 mg/amp 1 amp in 250 mL D5W, strength is 1 (if 2 amps for CHF, 2 and so on)
+Dopamine (ugtts/min)
desired dose x body weight in kg / (13.3 *
strength)
Desired dose 5-15 mcg/kg/min
For dopamine 200 mg/amp 1 amp in 250 mL D5W, strength is 1 (if 2 amps for CHF, 2 and so on)
+Norepinephrine (ugtts/min)
desired dose x body weight in kg / (0.133 *
strength)
Desired dose 0.5-30 mcg/kg/min
For norepinephrine 2 mg/amp 1 amp in 250 mL D5W, strength is 1 (if 2 amps for CHF, 2 and so on)
+
END.