2011-2012p1l139-9627120413175444

2011/4/6 Jesus Loves You!

Electrolytes Part II Potassium

Dr Chloe MakMBBS, PhD, FRCPA, FHKCPA, FHKAM

Consultant Chemical PathologistPrincess Margaret Hospital

[email protected]


Homeostasis

Input: In diet, e.g. meat, fish, fruit

Distribution Mainly in intracellular compartment

Output Body fluids with varying K concentrations See Table


Hyperkalemia Defined as

plasma K >5.0 mmol/L, or, serum K >5.5 mmol/L

Consequences of hyperkalemia: Mild: non-specific: malaise, vomit, nausea Vague muscle weakness (first sign) Flaccid paralysis Paraesthesia No correlation between weakness & K Cardiac arrhythmia

ECG changes: 6-7mmol/L: tall, peaked T waves 8-10mmol/L: aberrant QRS complexes 11mmol/L: fusion of QRS and T waves 10-12mmol/L: ventricular fibrillation


Prostaglandin inhibitionIndomethacinDiabetes MellitusInterstitial nephritis Syndrome of hyporeninemic hypoaldosteronismCommon in elderly with DM and mild renal impairment

Mineralocorticoid resistance(2 hyperaldosteronism)Interstitial nephritisObstructive uropathyAmyloidosisSLEPseudohypoaldosteronism

Extrarenal causes

Renin Aldosterone

Renin Aldosterone

Spot Renin & Aldosterone

ACTH stimulation

Plasma creatinine

Plasma HCO-3-

Exclude

Selective aldosterone deficiency

Addisons diseaseC21- -Hydroxylase deficiency

Normal response

No response/Blunted response

Normal

High Renal Failure (Acute or end stage renal failure)

Anion GapNormal

Decreased

NormalIncreased

DKARenal failure

*Extrarenal causes: Pseudohyperkalemia (eg hemolysed specimen, EDTA contamination, thrombocytosis, leucocytosis, aged samples) , tumor lysis syndrome, tissue necrosis, periodic paralysis hyperkalemia, drugs: IV/oral K therapy Acute renal failure Repeat K once

Renin Aldosterone

Normal Renin & Aldosterone

Hyperkalemia

Source: Cases in Chemical Pathology, RN Walmsley


Diagnostic Approach Hyperkalemia noted in the laboratory report R/o factitious results like:

Hemolysis Thrombocytosis Leucocytosis EDTA contamination Drip-arm

Repeat sample if query Decide the severity

Moderate: 6.5mmol/L

Do an ECG (save Urine K +/- other blood samples before Tx) Give treatment accordingly Review the test profiles for ? RF, ? DKA

Review drug history, K-sparing diuretics, oral intake


Extracellular Intracellular Distribution

1. Na/K ATPase Pump 2. Acid-base 3. Insulin 4. Adrenaline



1. Na/K ATPase Pump

If the pump fails, what will happen? What can cause the pump to fail?

www.cvphysiology.com


Case 1

F/65y, HT, DM. OPD FU Collection time 15/4/2011 14:05 Arrival time 16/4/2011 10:13 Plasma Na 140 (132-144mmol/L) K 5.5 (3.2-4.8mmol/L) Urea 5 (3.0-8.0mmol/L) Cr 125 (60-120umol/L)


2. Acid-base status HyperK and acidosis HypoK and alkalosis


Ref: mgwater.com


Case 2

F/65y Plasma Na 140 (132-144mmol/L) K 5.5 (3.2-4.8mmol/L) HCO3 15 (23-28 mmol/L) Urea 5 (3.0-8.0mmol/L) Cr 100 (60-120umol/L)


3. Insulin Insulin promotes cellular uptake of

Glucose Potassium magnesium phosphate



Case 3a

F/65y, nonketotic hyperglycemia, insulin drip was given

Insulin drip must be given together with _____!!!

To avoid lethal hypokalemia!

uwhealth.org


Case 3b M/48, known DM, found LOC Plasma Na 132 (132-144mmol/L) K 6.5 (3.2-4.8mmol/L) Urea 23 (3.0-8.0mmol/L) Cr 323 (60-120umol/L) Glucose 18 mmol/L Urine ketone ++ Potassium deficit despite hyperkalaemia


4. Adrenaline Adrenaline stimulates cellular potassium

uptake Lead to HypoK



Case 4

M/45y, asthma on ventolin, suicide attempt by drug overdose

Plasma Na 140 (132-144mmol/L) K 2.8 (3.2-4.8mmol/L) Urea 5 (3.0-8.0mmol/L) Cr 100 (60-120umol/L)


Renal Potassium Excretion

Aldosterone action

Na+

K+

H+

Lumen Collecting ducts Blood

Aldosterone


Case 5 Too less aldosterone Baby / 1 day old, ambiguous external

genitalia, hypotensive Plasma Na 118 (132-144mmol/L) K 6.5 (3.2-4.8mmol/L) Urea 9.5 (3.0-8.0mmol/L) Cr 60 (30-50umol/L)


http://www.aafp.org/afp/990301ap/1190.html


Some Types of Congential Adrenal Hyperplasia

Frequency %

Mineralocorticoids Androgens

21-hydroxylase CAH 90-95% 11-hydroxylase CAH 5% 3-HSD CAH very rare 17-hydroxylase CAH very rare

Wikipedia


Case 6 Too much aldosterone F/39y, young onset of hypertension

Plasma Na 143 (132-144mmol/L) K 3.0 (3.2-4.8mmol/L) Urea 5.0 (3.0-8.0mmol/L) Cr 70 (60-120umol/L)


Cause: Factitious Hyperkalemia

Plasma or serum K higher? Release of K from platelets in clotting

Leucocytosis Thrombocytosis Hemolysis

Increased Intracellular constituents E.g. AST, LDH, urate


Case 7a M/70y, CRF with renal transplant 10 years

ago, FU OPD

Na 140 (132-144mmol/L) K 9.5 (3.2-4.8mmol/L) Urea 5 (3.0-8.0mmol/L) Cr 110 (60-120umol/L)


Case 7a K 9.5 mmol/L is life-threatening unlikely to be true in normal individuals In addition, the patients RFT was normal. Suspected artifact

Ca 0.56 (2.20-2.60mmol/L)

EDTA contamination

What else will be falsely abnormal?

Do ECG if in doubt


Case 7b M/27, leukemia, just post chemotherapy Na 140 (132-144mmol/L) K 9.5 (3.2-4.8mmol/L) Urea 5 (3.0-8.0mmol/L) Cr 125 (60-120umol/L) Ca 0.56 (2.20-2.60mmol/L)


Case 7b

High PO4, urate Tumour lysis syndrome

Tissue damage: High K, PO4, AST, LDH, uric acid Tumor lysis Syndrome Other causes: trauma, burns, rhabdomyolysis


Case 7c M/58, Plasma Na 140 (132-144mmol/L) K 6.5 (3.2-4.8mmol/L) Urea 5 (3.0-8.0mmol/L) Cr 100 (60-120umol/L)Comments: Sample hemolyzed.


In general, marked hemolysis produces misleading results in the following analytes:

Can increase: Phosphate, potassium (horses, pigs, Japanese breed dogs (e.g. Akitas), some cows and sheep), CK, AST, LDH, uric acid, and magnesium.

Can decrease: alkaline phosphatase, amylase, and GGT.

http://ahdc.vet.cornell.edu/clinpath/modules/chem/hemol.htm


Case 8 You noted that the values of K are different in different sample

types for different tests. The three samples are collected on the same time. why?

Patient A

K from ABG profile using whole blood sample

6.8

Plasma K 4.4Serum K 4.9


Digitalis

Inhibit Na/K ATPase pump Inhibit intracellular K+ uptake

Digoxin overdose hyperK

Risk factors for digoxin overdose: Elderly Hypothyroidism HypoK

with courtesy of Dr Morris Tai


Internal balance

3Na+

2K+Digoxin

glucose

K+

insulin

Catecholamines, aldosterone, thyroxine

H+H+K+

K+

with courtesy of Dr Morris Tai


Autosomal dominant disorder Acute onset of muscle weakness

associated with hyperK Spontaneously resolves over a few hrs PPt by exercise, cold, hyperK

Hyperkalemic periodic paralysis


AD mode Male predominance Attacks of flaccid paralysis lasting 6-24

hours with marked hypoK Spontaneously return to normoK

afterwards

Hypokalamic periodic paralysis


Case 8 M/18y, sudden onset of paralysis Plasma Na 140 (132-144mmol/L) K 5.5 (3.2-4.8mmol/L) Urea 5 (3.0-8.0mmol/L) Cr 100 (60-120umol/L)


Common causes of hyperkalaemia

1. Artefactual2. Renal failure3. K-sparing diuretics

Medically important causes of hyperkalaemia

1. Mineralcorticoid deficiency Some types of congenital adrenal hyperplasma Addisons disease

2. DKA (apparent hyperK)


HypoK

Defined as plasma K


Inadequate intakeChronic alcoholismAnorexia nervosaInappropriate IV therapyExtrarenal lossChronic diarrheaLaxative abusePrevious diureticsVillous adenoma of colonSalbutamol, insulinHypokalemic periodicParalysisIntracellular shift vitamin B12 therapy

Renal Loss VomitingCurrent diureticsMineralocorticoid excess syndromeGentamycinMg depletion ( can cause refractory hypocalcemia & hypokalemia) Leukemia

Acute diarrhea

Renal LossRenal tubular acidosis type 1, type 2Carbonic anhydrase inhibitors

< 20 40 mmol/L

Plasma HCO3-

Normal/ Increased

Decreased

Paired Spot urine K before K replacement

> 20 40 mmol/L

Paired spot Urine K before K replacement

< 20 40 mmol/L

> 20 40 mmol/L

Hypokalemia Diagnostic Pathway of Hypokalemia



Common causes of hypokalaemia1. Diuretics2. Vomiting/diarrhoea3. Magnesium deficiency

Medically important causes of hypokalaemia1. Mineralcortcoid excess 2. Glucocorticoid excess3. Renal tubular acidosis


Table: Approximate electrolyte composition of body fluids:

Concentration (mmol/L)Na+ K+ Cl- HCO3-

Plasma 140 4 100 25Saliva 60 15 30 40Gastric Juice 80 10 150 --Bile 150 10 50 30Pancreatic 110 10 40 100Diarrhoea fluid 60 40 ~ 100 varied variedUrine 100 50 80 --


Case 9 M/3mo, pyloric stenosis with refractory vomiting

Plasma Na 140 (132-144mmol/L) K 2.5 (3.2-4.8mmol/L) HCO3 30 (23-28 mmol/L) Urea 5 (3.0-8.0mmol/L) Cr 100 (60-120umol/L)

Vomiting Alkalosis potentiate hypoK Secondary hyperaldosteronism if hypovolemia

Similar mechanisms in excessive nasogastric suction


Case 10

M/65, chronic smoker, weight loss and dry cough for 3 months

Na 140 (132-144mmol/L) K 2.6 (3.2-4.8mmol/L) Urea 7 (3.0-8.0mmol/L) Cr 110 (60-120umol/L)


Case 10

Further investigations Urine K = 102 mmol/l

Cortisol 2424 umol/L ACTH increased

CXR lung mass Dx?


Case 11 F/70y, ca stomach on chemotherapy Plasma K 2.3 mmol/L (3.5-5.0) Ca 1.86 mmol/L (2.25-2.55) PO4 0.56 mmol/L (0.6-1.2) ALB 30 g/L (30-52)

Hypocalcemia refractory to replacement Whats the reason for his hypocalcemia?


Hypomagnesemia

Severe hypomagnesemia


Prostaglandin inhibitionIndomethacinDiabetes MellitusInterstitial nephritis Syndrome of hyporeninemic hypoaldosteronism(Common in elderly with DM and mild renal impairment )

Mineralocorticoid resistance(2 hyperaldosteronism)Interstitial nephritisObstructive uropathyAmyloidosisSLEPseudohypoaldosteronism

Extrarenal causes

Renin Aldosterone

Renin Aldosterone

Spot Renin & Aldosterone

ACTH stimulation

Plasma creatinine

Plasma HCO-3-

Exclude

Selective aldosterone deficiency

Addisons diseaseC21- -Hydroxylase deficiency

Normal response

No response/Blunted response

Normal

High Renal Failure (Acute or end stage renal failure)

Anion GapNormal

Decreased

NormalIncreased

DKARenal failure

*Extrarenal causes: Pseudohyperkalemia (eg hemolysed specimen, EDTA contamination, thrombocytosis, leucocytosis, aged samples) , tumor lysis syndrome, tissue necrosis, periodic paralysis hyperkalemia, drugs: IV/oral K therapy Acute renal failure Repeat K once

Renin Aldosterone

Normal Renin & Aldosterone

Hyperkalemia



Try to practice in this way: Make up a case of Syndrome of hyporeninemic

hypoaldosteronism Common in elderly with DM and mild renal impairment Hx: ____________________ Na ____ (132-144mmol/L) K ____ (3.2-4.8mmol/L) Urea ____ (3.0-8.0mmol/L) Cr ____ (60-120umol/L)

What other investigations do I need? ___________________


Inadequate intakeChronic alcoholismAnorexia nervosaInappropriate IV therapyExtrarenal lossChronic diarrheaLaxative abusePrevious diureticsVillous adenoma of colonSalbutamol, insulinHypokalemic periodicParalysisIntracellular shift vitamin B12 therapy

Renal Loss VomitingCurrent diureticsMineralocorticoid excess syndromeGentamycinMg depletion ( can cause refractory hypocalcemia & hypokalemia) Leukemia

Acute diarrhea

Renal LossRenal tubular acidosis type 1, type 2Carbonic anhydrase inhibitors

< 20 40 mmol/L

Plasma HCO3-

Normal/ Increased

Decreased

Paired Spot urine K before K replacement

> 20 40 mmol/L

Paired spot Urine K before K replacement

< 20 40 mmol/L

> 20 40 mmol/L

Hypokalemia Diagnostic Pathway of Hypokalemia



Try to practice in this way: Make up a case of Renal tubular acidosis type 1 Hx: ____________________ Na ____ (132-144mmol/L) K ____ (3.2-4.8mmol/L) Urea ____ (3.0-8.0mmol/L) Cr ____ (60-120umol/L)

What other investigations do I need? ___________________


Thank you

Electrolytes Part IIPotassiumHomeostasisHyperkalemia 4Diagnostic ApproachExtracellular Intracellular DistributionExtracellular Intracellular DistributionCase 1Extracellular Intracellular DistributionCase 2Extracellular Intracellular DistributionCase 3aCase 3bExtracellular Intracellular DistributionCase 4Renal Potassium ExcretionCase 5 Too less aldosterone 18 19Case 6 Too much aldosteroneCause: Factitious HyperkalemiaCase 7aCase 7a Case 7bCase 7bCase 7c 27Case 8DigitalisInternal balance 31Hypokalamic periodic paralysisCase 8 34HypoK 36 37Table: Approximate electrolyte composition of body fluids:Case 9Case 10Case 10Case 11Hypomagnesemia 44Try to practice in this way: 46Try to practice in this way:Thank you

2011-2012p1l139-9627120413175444

Documents

mmoll cr

mmoll urea

mmoll hco3

120umoll201146 jesus

com201146 jesus

table201146 jesus

adrenaline201146 jesus

rn walmsley201146 jesus