Potassium Flashcards
1
Q
Hyperkalemia
Work up
A
- Confirm it with a repeat blood draw. In setting of extreme leukocytosis or thrombocytosis, check plasma K+
- Spot urine K+:
- Less than 20 mEq/L (while urine osmolality is about 300 mOsm/kg) suggests impaired renal function
- More than 40 mEq/L (while urine osmolality is about 300 mOsm/kg) suggests high intake or shift
2
Q
Hyperkalemia
Causing Drugs
A
- Aldosterone resistance:
- K+-sparing diuretics
- Trimethoprim-sulfamethoxazole
- Decrease aldosterone production:
- NSAIDs
- ACEIs and ARBs
- Cyclosporine (Also shifts K+ out of cells) and Tacrolimus
- Heparin (decrease aldosterone production)
- Shifts K+ out of cells
- Beta-blockers
- Digoxin and Fluoride toxicity (also venom of Bufo gargarizans toad that is used in Chinese folk medicine which acts like digoxin)
- Methotrexate
- Propofol infusion syndrome
- Succinylcholine
- Pentamidine
- Ketokonazole
- Metyrapone (reversible inhibitor of 11-beta hydroxylase, which stimulates ACTH secretion)
- Herbs:
- Alfalfa
- Dandelion
- Horsetail
- Stinging Nettle
3
Q
Hyperkalemia
Shifting of K+ into extracellular space Causes
A
- Metabolic acidosis
- Acute tubular necrosis
- Electrical and thermal burns
- Head trauma
- Rabdomyolysis
- Tumor lysis syndrome
- Hypertonicity states
4
Q
Hypomagnesemia
Treatment
A
- IV and oral supplements
- Hypokalemia and hypocalcemia will not correct without magnesium correction
5
Q
Hypokalemia
Treatment
A
- Stop ongoing losses like administration of H2 blockers in patients receiving NG suction and control hyperglycemia if glycosuria is present
- Replacement of K+ through oral or IV route or both in addition to correction of Mg++
6
Q
Hypomagnesemia
Presentation
A
In severe cases:
- Paresthesias
- Irritability, confusion, and lethargy
- Seizures
- Tetany
- Arrhythmias
- Hyperactive reflexes
7
Q
Hyperkalemia
Decreased Excretion Causes
A
It is due to Type IV renal tubular acidosis which can be caused by the following:
- DM
- Sickle cell disease or trait
- Lower urinary tract obstruction
- Adrenal insufficiency
- Primary Addison syndrome
- Enzyme deficiencies
8
Q
Hyperkalemia
ECG Findings
A
- Tall peaked T waves
- Wide QRS complex
- Prolongation of PR interval
- Low or loss of P waves
- Can progress to sine waves, VF and cardiac arrest
9
Q
Hypokalemia
Inadequate potassium intake Causes
A
- Eating disorders: anorexia, bulimia, starvation, pica, and alcoholism
- Dental: impaired ability to chew
- Poverty and “tea-and-toast” diet of elderly individuals
- Hospitalization: potassium-poor TPN
10
Q
Hypomagnesemia
Decrease intake Causes
A
Serum Mg++ < 1.5 mEq/L
- Malnutrition
- Malabsorption
- Short bowel syndrome
- TPN
11
Q
Hypokalemia
ECG Findings
A
- T-wave flattening
- U waves (an additional wave after T wave)
- ST segment depression
- AV block and subsequent cardiac arrest
12
Q
Hypokalemia
Genetic Causes
A
- Congenital adrenal hyperplasia (11-beta hydroxylase or 17-alpha hydroxylase deficiency)
- Glucocorticoid-remediable hypertension (AD disorder; fusion of regulatory region of 11-beta hydroxylase to coding region of aldosterone synthase [both on Chrom. 8] which results in an aldosterone synthase that is directly sensitive to ACTH; it responds to Rx with dexamethasone, spironolactone and eplerenone)
- Bartter syndrome
- Gitelman syndrome
- Liddle syndrome
- Gullner syndrome
- Glucocorticoid receptor deficiency
- Hypokalemic period paralysis
- Thyrotoxic periodic paralysis (TTPP)
- SeSAME syndrome
13
Q
Hypokalemia
Potassium shift to intracellular space Causes
A
- Alkalosis
- Insulin or glucose administration (glucose stimulates insulin release)
- Intensive beta-adrenergic stimulation
- Hypokalemic period paralysis
- Thyrotoxic periodic paralysis (TTPP)
- Refeeding: prolonged starvation, eating disorders and alcoholism
- Hypothermia
14
Q
Hypomagnesemia
Increased loss Causes
A
- Diuretics
- Diarrhea
- Vomiting
- Hypercalcemia
- Alcoholism
15
Q
Hypomagnesemia
Diagnosis
A
- There may be a concurrent hypocalcemia and hypokalemia
- ECG may reveal prolonged PR and QT intervals
16
Q
Hypokalemia
Work up
A
- Spot urine K+
- Less than 20 mEq/L (while urine osmolality is about 300 mOsm/kg) suggests GI losses, poor intake or shift
- More than 40 mEq/L (while urine osmolality is about 300 mOsm/kg) suggests renal loss
- Spot urine Na+: if less than 20 mEq/L with a high urine K+ this suggests secondary hyperaldosteronism
17
Q
Hypokalemia
Renal losses Causes
A
- Renal artery stenosis (increased renin)
- DKA
- Hypomagnesemia (Mg++ dependent K+ channels which open and spill K+ into urine when Mg++ is low)
- Renal tubular acidosis (RTA) type I and II
- Liquorice (Glycyrrhizic acid that inhibits 11-beta-hydroxysteroid dehydrogenase)
- Mineralocorticoid excess:
- Endogenous: Cushing syndrome, Primary and secondary hyperaldosteronism, and tumors that secret adrenocorticotropic hormone
- Exogenous: steroid therapy
18
Q
Hyperkalemia
Genetic Causes
A
- Glomerulopathy with fibronectin deposits (GFND)
- Disorders of steroid metabolism and mineralocorticoid receptors
- Congenital hypoaldosteronism
- Pseudohypoaldosteronism
- Disorders of Chloride homeostasis
- Nephronothisis
- Hyperkalemic periodic paralysis (HYPP)
19
Q
Hypokalemia
GI losses Causes
A
- Diarrhea
- Vomiting
- Small intestine drainage
- Chronic laxative use
- NG suction
20
Q
Hypokalemia
Drug Causes
A
- Diuretics: osmotic, loop and thiazides
- Methylxanthines: theophylline, aminophylline and caffeine
- In overdose: verapamil, quetiapine, and penicillins
- Bicarbonates
- Antifungals: amphotericin B, Azoles, and Echinocandins
- Gentamicin
- Cisplatin
- Ephedrine
- Beta-agonist intoxication
21
Q
Hyperkalemia
Increased Intake Causes
A
Occurs when accompanied by impaired renal K+ excretion:
- High K+, low Na+ diet
- K+ supplements
- “No salt” and “low salt” dietary salt substitutes
- High K+ in IV fluid preparations like TPN
- Penicillin G potassium
- PRBC transfusion (peak risk at 2-3 weeks of cell storage)
- Cardioplegia Solutions
22
Q
Hypomagnesemia
Other Causes
A
- DKA
- Pancreatitis
- Extracellular fluid volume expansion
23
Q
Hyperkalemia
Treatment
A
- Calcium gluconate for cardiac cell membrane stabilization (it works within few minutes)
- Give bicarbonate and/or insulin with glucose to temporarily shift K+ into cells
- Beta-agonists like Albuterol to promote cellular reuptake of K+
- Eliminate K+ from diet and IV fluids
- Kayexalate (Sodium polystyrene sulfonate) to remove K+ from the body (contra-indicated in ileus, bowel obstruction, ischemic gut, or pancreatic transplants [can cause bowel necrosis])
- Loop diuretics and dialysis also can be used
