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History of the present illness
Medical decision-making and treatment- calcium gluconate
- insulin + glucose
- albuterol by nebuliser
- bicarbonate
- kayexalate - sodium polysyrene sulfonate
- lasix
- dialysis
- treat the underlying cause of the hyperkalemia
| Introduction |
- this guidemap is mainly focused on the ED management of life-threatening hyperkalemia
- to determine the likely cause of the hyperkalemia (if the etiology is not clinically evident) => use the algorithm for the diagnosis of hyperkalemia in conjunction with the table listing causes of hyperkalmia
| History of the present illness |
- neurological symptoms
- fatigue, generalized weakness, distal limb paresthesias, muscle cramps, restless legs, fasiculations, tetany, respiratory depression
- an ascending proximal muscle paralysis rarely occurs and is usually incomplete - cardiac arrythmias usually dominate the clinical picture before complete muscle paralysis occurs
- palpitations or weakness/dizziness secondary to an arrhythmia (second/third degree heart block, wide complex tachyarrhythmia, ventricular tachycardia)
- sudden cardiac arrest (VF or asystole or electro-mechanical dissociation)
| Risk factors |
- renal failure
- acute renal failure especially in association with hypercatabolic states (rhabdomyolysis, tumor lysis syndrome, severe IV hemolysis)
- chronic renal failure + supplemental potassium load (eating potassium-rich foods, salt-substitutes, taking potassium supplements, TPN, potassium-containing medicines eg. IV penicillin) +/- potassium-sparing diuretics
- primary (Addisons disease)
- secondary - hyporeninemia - elderly diabetics, chronic interstitial nephritis (type IV RTA)
- sickle cell disease, amyloidosis, SLE, renal allograft, analgesic nephropathy
- drugs - angiotensin converting enzyme inhibitors (especially when administered in association with potassium-sparing diuretics), spironolactone, amiloride, triamterene, high-dose trimethoprim, pentamidine, digoxin, NSIADs, cyclosporine, heparin (prolonged use - greater than 3 days use)
- redistribution of potassium
- acidosis
- hyperkalemic periodic paralysis (familial)
- hypertonicity (mannitol, hyperglycemia)
- drugs (succinylcholine, beta blockers, digoxin)
- hemolysis during blood sampling or centrifuging
- excessively "tight" arm cuff + "clenched fist"
- platelets > 1,000,000; leucocytes > 70,000
- family history of abnormal red blood cell membrane permeability
| Examination |
- first check the patient's ABC’s with a special emphasis on the evaluation of any respiratory depression
| Diagnostic testing |
There is no definite correlation between any ECG changes and the serum potassium - the relationship depends on individual patient sensitivity and the rapidity of development of the hyperkalemia
(* ECG signs may be absent if the onset of hyperkalemia is slow - as seen in chronic renal failure - even though the serum potassium is in the range of 7 - 7.5meq/L; by contrast, acute hyperkalemia can produce ECG signs at much lower serum potassium levels)
- tall peaked T waves with a narrow base (called "tenting") or even more exaggerated "thorn-like" peaked T waves, an increased PR interval, and a slightly prolonged QRS duration suggest a serum potassium > 6 - 7 meq/L
- P wave flattening => absent P waves and/or marked QRS widening suggest a serum potassium > 7 - 8 meq/L
- fusion of the widened QRS complex and a tall T wave forming a sine wave suggests a serum potassium > 8 - 9 meq/L
- certain ECG changes may mimic an AMI
- other typical ECG patterns include the "dumping" pattern and the "z-fold" pattern
- varying degrees of heart block and ventricular tachyarrhythmias
- the progression from benign to malignant arrhythmias can be rapid and unpredictable
- any diagnostic ECG change represents an emergency requiring aggressive therapy
(* see the appendix for samples of ECG changes in hyperkalemia)
- serum electrolytes, calcium, serum digoxin, BUN and creatinine, glucose +/- ABG’s
(* consider Addison's disease in a hyperkalemic patient who has associated hyponatremia and postural hypotension => diagnosed by a low serum cortisol and lack of response to a synthetic ACTH injection)
- plasma renin and plasma aldosterone levels prn in patients with a history of diabetes mellitus, or if there is a suggestion of some type of tubulo-interstitial renal disease, or when the etiology is not readily apparent
| Medical decision-making and treatment |
- continuous cardiac monitoring is mandatory if the patient has severe hyperkalemia (serum potassium > 6.5 MEq/L) or cardiac arrhythmias
- a patient with mild-moderate hyperkalemia (serum potassium < 6.0 meq/L) can be treated with dietary restriction + discontinuation of any potassium sparing diuretic +/- a potassium-binding resin eg. sodium polystyrene sulfonate (Kayexalate) = 15 - 30 g qd/qid => the patient can be discharged and followed-up in 48 - 72 hours
- a patient with moderate hyperkalemia (serum potassium 6.0 - 6.5 mEq/L) should probably be admitted to hospital for supervised lowering of the serum potassium with a potassium-binding resin
- treat hyperkalemia more emergently if the serum potassium is > 6.5 meq/L or if there are any ECG changes suggestive of hyperkalemia => use sodium polystyrene sulfonate as first line therapy +/- insulin/glucose +/- calcium gluconate
The following drug order sequence is recommended for life-threatening hyperkalemia (absent P waves + widened QRS complex, and/or serum potassium > 8 meq/L, and/or significant cardiovascular symptoms or arrhythmias, and/or severe neuromuscular symptoms)
- there is no "correct" dose
- 10 ml of 10% calcium gluconate solution over 10 minutes IV (rule of "tens") is a common approach
- calcium chloride can be used at 1/3 the dose of calcium gluconate
(* calcium should preferably be administered in large veins because it is sclerosing)
- works in 1 - 3 minutes and lasts 30 - 60 minutes
- repeat dose in 5 - 10 minutes if no ECG change/improvement
- initial dose can be given in 1 - 3 minutes for life-threatening arrhythmias or sine wave ECG changes, and repeated every 2 - 5 minutes prn
- short-half life requires repeat dosing every 20 minutes prn
(* calcium only antagonises potassium's deleterious electrical effect on the myocardium and it does not decrease the serum level of potassium - it is used temporarily until the serum potasium can be decreased by insulin + glucose administration)
- pediatric dose = 75 - 100 mg/kg IV (0.75 - 1.0 cc/Kg to maximum of 10 cc)
- special warnings:-
- calcium should be given slowly over 20 - 30 minutes in a digitalised patient by diluting the calcium in 100 ml of normal saline and giving the calcium by an infusion pump - high risk of increased myocardial toxicity in the digitalised patient
- calcium is contra-indicated in digoxin-toxic patients and hypercalcemic states
- don’t give calcium in solutions containing bicarbonate
- insulin + glucose is used to drive potassium into the cells
- 10 units insulin by rapid IV bolus + 50ml of 50% dextrose IV over 20 - 30 minutes; or the insulin can be mixed with 100 ml of 20% dextrose solution and administered IV over 20 - 30 minutes
- glucose should not be given to diabetics without first giving insulin - because insulin is needed to move potassium into the cells; also avoid giving 50% glucose by rapid IV bolus injection
(* rapid bolus injection of concentrated glucose => hypertonicity-induced potasium redistribution => temporary increased serum potassium before the insulin takes effect)
- pediatric dose = 0.1 unit/kg of insulin + 25% glucose (0.5 mg/kg - 2ml/kg of 25% concentration)
- onset occurs within 15 - 60 minutes and effect lasts 4 - 6 hours
- follow-up 10% glucose solution at 50 - 100cc/hour is rarely needed - only if the patient develops hypoglycemia secondary to the IV insulin bolus
(* IV glucose is not indicated when the serum glucose is greater than 250mg/ml => check the serum glucose frequently to detect delayed-onset hypoglycemia)
- 10 - 20mg in 4 ml saline over 10 - 20 minutes (large doses required)
(* may need to be given undiluted over 5 - 10 minutes in a patient with life-threatening hyperkalemia)
- immediate onset and maximum effect in 90 - 120 minutes
- decreases serum potassium by about 0.5 - 1.0 meq/L
- pediatric dose = same as the adult dose
(* small risk of tachyarrhythmias => stop if PVC's develop)
- only indicated when the patient is significantly acidotic (serum bicarb < 5 - 10)
- beneficial effect is small and inconsistent
- useful if the patient is also sodium/volume depleted => use 3 amps of bicarb in 1L of 5DW at desired rehydration rate
- more rapid administration of bicarbonate (1 amp over 10 - 15 minutes) should be reserved for severely acidotic patients with sine wave QRS changes
- pediatric dose = 0.5 - 1.0 meq/kg
(* sodium load worsens hypertension and may induce CHF in vulnerable patients)
5) Kayexalate - sodium polystyrene sulfonate
- defer if the patient is going to be dialysed within 2 hours to avoid a "colonic laundry"
- po route preferred if possible (greater degree of cation exchange)
- 15 - 50g in 100cc of 70% sorbitol po (or use commercial preperation)
- onset within 1 - 2 hours and lasts 4 - 6 hours
- dose can be repeated q 4 hourly, up to 5x doses/day prn
- use a retention enema if po administration is not preferable/possible
- use a retention enema of 50 - 100g kayexalate + 50cc of 70% sorbitol + 150cc tap water, or suspend the powder in 10% dextrose solution, or use 120 - 180cc of the commercially available suspension
- the retention enema is administered through a 24 - 28g rectal tube placed 20cm into rectum after any necessary pre-cleansing enema, followed by a saline flush of 50cc
- a retention enema must be retained for at least 30 - 60 minutes, preferably 1 - 2 hours
(* po administration may produce nausea and vomiting; retention enema with sorbitol - risk of colonic perforation in post-op renal transplant patients and therefore contra-indicated; risk of volume overload from sodium load whether given po or by retention enema)
- pediatric dose = 0.5 - 1g/kg po (maximum of 50g) or 1 - 2g/kg rectally (mixed in 70% sorbitol solution)
- 40 - 80 mg of lasix IV to all patients who can produce urine
- pediatric dose = 1 mg/kg IV
- primary therapy when renal function is absent
- prompt dialysis may also be required in patients with ARF + associated rhabdomyolysis (large potasssium load)
- also used for intractable hyperkalemia unresponsive to conservative pharmacological measures
8) Treat any underlying cause of the hyperkalemia
- treatment is disease-specific
| Appendix |
- "Tenting" pattern with tall waves
- "Thorn-like" T waves
- "Sine" wave pattern
- ECG mimicing an acute inferior AMI
- "Dumping" pattern
- "Z-fold" pattern
| Causes of hyperkalemia |
Pseudohyperkalemia
Chronic renal failure Urinary tract obstruction Tubular defects in potassium secretion
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Algorithm for the diagnosis of hyperkalemia
