2. Introduction
Normal potassium levels are 3.5-5 mEq/L
Hypokalemia is defined as plasma K levels <3.5mEq/L
Plasma potassium levels correlate poorly with the total
potassium deficit.
Potassium is essential for Muscles, cardiovascular system,
Central nervous system, respiratory system.
Maintain osmolarity of ECF and ICF and hence cellular
volume
3. Regulation of acid base balance along with cellular growth,
protein synthesis and hormonal secretion
Vital for cell excitability and muscle contraction
Maintenance of transmembrane electric potential.
4. Physiology
98% of total body K+ is intracellular and chiefly in muscles.
In a healthy individual steady state K+ excreted 90% in urine
and 10% in feces.
K+ absorbs from small intestine; through duodenum, jejunum
and ileum.
K+ mainly required for the below mentioned channels’
K+ ATPase: almost all cells contains this pump; required for
maintenance of ICF and ECF through electromechanical gradient
(3 Na+ out & 2 K+ in)
5. H+K+ATPase: In GI cells and renal tubules (H+ out and K+
in)
Na+K+Cl- co transport: in salivary gland, GI tract and
Renal tubules; brings 1 Na+, 1 K+ & 2 Cl- inside cell
K+CI- Co transport: plays role in maintaining volume of
erythrocytes.
6. Potassium homeostasis is mainly done by renal system.
In case of hypokalemia it reabsorbs the filtered K+ and in
hyperkalemia it promotes secretion of K+ by principle
cells.
8. Etiology of Hypokalemia
There are 2 main causes of hypokalemia:
Transcellular K' shifts from ECF to ICF:
Iatrogenic causes:
Insulin therapy
Lithium therapy
Vitamin B therapy
Barium ingestion
Exogenous catecholamines:
Epinephrine
Ritodrine, terbutaline
13. Pathophysiology
K+ is the principle intracellular cation, 98% of K in body is
intracellular
Extracellular K+ is found mainly in muscles
Hypokalemia results in a reduction of the extracellular
potassium levels
Reduction in ECF K+ leads to a reduction in the resting
membrane potential (RMP)
This causes reduced responsiveness to sodium shifts into
the cell
14. Therefore, cellular excitability reduces
Chronic K+ loss causes ratio of ICF: ECF K+ to remain
stable
Acute K+ loss causes redistribution from ECF to ICF,
causing changes in RMP
This causes hyperpolarization of cardiac cell resulting in:
Ventricular premature ectopics.
Re-entrant phenomenon
Ectopic tachycardia
15. Clinical features
Cardiovascular system:
Hypertension
Autonomic neuropathy
Orthostatic hypotension
ECG changes :
U waves
T wave inversion
ST depression
QT shortening
16. Dysrhythmias: ventricular ectopics and AF most commonly
Myocardial dysfunction
Neuromuscular:
Malaise
fatigue
Skeletal muscle weakness
Hyporeflexia
Cramps, paralysis, tetany
Paresthesia, rhabdomyolysis
18. Metabolic:
Encephalopathy in patients with liver disease
Endocrine:
Glucose intolerance due to decreased insulin secretion
Decreased aldosterone secretion
19.
20.
21.
22.
23. Ecg changes that do not correlate with
severity of Hypokalemia
Changes include:
Narrow QRS complexes
ST depression > 0.5 mm
QT prolongation
T wave inversion and flattening
U wave amplitude> 1 mm
U wave amplitude greater than T wave amplitude inthe
same lead
24. These patients are predisposed to serious ventricular
arrhythmias such as:
Ventricular tachycardia
Torsades de-pointes
Ventricular fibrillation.
25. Therapeutic goals
1. Prevention of hypokalemia
2. To prevent life threatening complications. (arrhythmia
and respiratory failure)
3. To correct the potassium deficit
4. To minimize on-going losses
5. To treat underlying etiology
26. Prevention of potassium depletion
Normal potassium intake of about 60 mEq/day is sufficient to
prevent hypokalemia.
But patients receiving digitalis, long term diuretics or large
doses of steroids should receive potassium supplement.
Conditions where prevention of hypokalemia is of special
importance are digitalis therapy, hepatic failure, previous
myocardial infarction or IHD and diabetes mellitus.
Postoperative patients on parenteral fluid therapy should
receive40-50 mEq/day of potassium to prevent hypokalemia.
27. How much total body potassium deficit
occurs in hypokalemia?
The degree of total body potassium depletion does not
correlate with serum potassium.
Roughly 1 mEq/L fall in serum potassium 200-400 mEq
total body potassium deficit.
28. When to treat hypokalemia? – Treatment
guidelines
3.5 to 4 mEq/L:
No potassium supplement. Increased oral intake of potassium rich
food ,Add potassium sparing diuretics or decrease dose of diuretics
3 to 3.5 mEq/L:
Treatment in selected high risk patients(Risk of arrhythmia e.g.
CHF, digitalis therapy, history of acute myocradial infarction or
IHD.)
< 3 mEq/L :
Needs definitive treatment
29. How much potassium to give
The amount of potassium required to correct potassium deficit
cannot be determined by any fixed formula.
When the average deficit of potassium is about 200-400 mEq,
50 - 100 mEq/day of potassium slowly given & it adequately
corrects deficit.
With severe hypokalemia or with high rate of ongoing loss,
larger dose may be required.
The deficit should be corrected slowly over a period of days. It
may take weeks to correct severe potassium loss.
Failure to increase serum potassium after sufficient dose and
duration of potassium supplement raises the possibility of
associated magnesium deficiency.
30. Selection of Potassium preparations
Potassium chloride (KCI) is usually the preparation of choice and
will promote correction of hypokalemia as well as of metabolic
alkalosis (vomiting and diuretics lead to both hypokalemia and
alkalosis).
Potassium bicarbonate and citrate tend to alkalinize the patient
and would be more appropriate for hypokalemia associated with
chronic diarrhoea or distal RTA.
Oral potassium administration is safer than I.V. route because I.V.
route carries high risk of hyperkalemia.
31. Inj. Potassium chloride: Most widely available and used is
inj. KCI 15%, 10 ml ampoule.
10 ml of 15% KCI = 1.5 gm KCI = 20 mEq of potassium,1 ml
of 15% KCI = 2 mEq of potassium
32. Oral K+ Supplementation
Oral potassium is a safer mode of correction of hypokalemia's
In mild to moderate hypokalemia (serum potassium 3 to 3.5 mEq/L)
average dose of potassium chloride is 60 to 80 mEq/day (20 mEq, 3-
4 times) along with treatment of underlying disorder (such as
vomiting or diarrhoea).
In severe or symptomatic hypokalemia more rapid replacement is
needed and can be most easily done by oral replacement.
In severe cases (serum potassium 2 mEq/L or less) it can be
increased upto 40 mEq 6 hourly under close ECG monitoring.
33. Potassium chloride solution, available in the market
contains 20 mEq potassium per 15 ml solution (1gm
KCl=13.4 mEq of potassium).
KCI tablets available contain 8 mEq potassium per tablet.
Oral potassium preparation may frequently cause G.I.
irritation and therefore the patient is advised to take
potassium chloride solution with proper dilution in a glass
of water, after food.
Esophageal or small bowel erosion and stricture are
uncommon side effects.
34. Potassium rich food:
Fruit juices, coconut water, banana, juicy fruits, dry
fruits, chocolate, coffee, soup, salt substitutes e.g. Lona
salt.
35. Iv potassium therapy
I.V. potassium supplementation carries higher risk of
hyperkalemia.
So I.V. potassium supplementation should be reserved for
severe symptomatic hypokalemia (K* <3 mEq/L) or for patients
who cannot ingest oral potassium
common guidelines for I.V. potassium therapy are as follows:
Always monitor I.V. potassium therapy closely with continuous ECG
monitoring and frequent serum potassium estimation.
Avoid I.V. potassium, till urine output is established
36. Don't give 10-20 mEq/hour.
Don't give> 40 mEq/Litre.
Don't give > 240 mEq/day.
Never give inj. KCI directly intravenously, it can cause
sudden hyperkalemia and instant death from cardiac
arrest.
Never add KCI to Isolyte-M.
Remember that hypokalemia is safer than hyperkalemia.
37. Rapid I.V. correction can cause dangerous hyperkalemia
even in potassium depleted patients.
Treatment of acidosis with I.V. NaHCO, may aggravate or
precipitate hypokalemia (due to intracellular shift of
potassium
38. How long to give
As soon as cardiac rhythm returns to normal or the
respiratory muscle strength is restored to normal, I.V.
potassium drip is gradually tapered and discontinued and
oral KCI is initiated.
39. Infusion rate and method:
(Body weight) x (Potassium deficit) 1
KCL required in mL = _____________________________ x ___
2 3
Maximum rate is 0.5 mEq/kg/hr or 250 mEq/day
20 mEq K is added to 100 mL of NS and infused over 1 hour
Maximum rate of infusion is usually set at 20 mEq/hr
41. Pre-operative considerations
Patients with ESRD should undergo dialysis except during
emergency surgery
Plasma K+ levels measured 1-3 days before surgery
0.2-0.8 mEq/L higher than if measured immediately before
surgery
Beta blockers like propranolol can be used to prevent this effect
Prevent hypokalemia from anxiety induced hyperventilation by
premedication with dexmedetomidine/clonidine
42. INTRA-OPERATIVE CONSIDERATIONS
Glucose free intravenous fluids are used
No change in anesthetic requirements immediately in
perioperative period
Avoid hyperventilation as it aggravates hypokalemia by causing
respiratory alkalosis
Increased sensitivity to NMBAs may be seen
This may necessitate:
Reduction in dosage of NMBAS
Monitoring with nerve stimulator
Prolonged NMB action expected post-surgery: delayed recovery.
43. Following factors should be considered
before postponement of Sx
Urgency of surgery
Concomitant medications given (digitalis toxicity with
serum K<4 mEq/L)
Acid base balance
Sudden of development of hypokalemia
All patients undergoing elective surgery to have normal K+
level
Postponement of surgery not required if K+ >3 mEq/l.
