Electrolytes And Blood Gas

Question 1

What is the normal serum potassium?

Answer 1

3,5 mm - 5 mmol

Question 2

When must hyperkalaemia be treated?

Answer 2

If >6 mmol

Question 3

How is hyperkalaemia treated (5) (“potassium shift”)

Answer 3

1. Stop all sources eg ringer’s
2. Promote excretion if K > 6,5. Use loop diuretic (furosemide)! or sodium polystyrene sulphonate (kayexelate)!
3. If K > 6,5 NB to antagonise cardiac effects with Cacl2! Or calcium gluconate
4. Promote moment of K into cells with insulin plus dextrose!, treat metabolic acidosis with NaHCO3, B agonists! (Nebulise salbutamol) and hyperventilation!
5. Treat refractory hyperkalaemia with dialysis
   Other: Cation exchangers (kayexelate)

Question 4

How will hyperkalaemia of >5,5 mmol affect surgery?

Answer 4

No elective surgery!

Question 5

What is hypernatraemia and what are some causes and treatment in hypo, Normo and hyper volaemia?

Answer 5

• > 145. Postpone surgery if >150
• hypervolemia: hypertonic saline ( treat loop diuretics and dextrose water)
• normovolaemia: diabetes insipidus (treat desmmopressin and dextrose water )
• hypovolaemia: renal losses due to osmotic solute diuretics, D and v, sweating (treat dextrose water), impaired water intake dehydration!

Question 6

What is hypokalaemia and what are 3 causes , ECG changes, 5 complications and treatment?

Answer 6

•<3,5
• redistribution from extra to intracellular: alkalosis, insulin, beta agonist, decreased B12, hyperventilation!
• decreased intake
• increased losses by kidneys (increased mineralocorticoid, increased renin, diuretics, antibiotics, RTA), by GIT (vomiting, diarrhoea)
• ECG changes: large P, prolonged pr, St depression, t wave flat, large u wave, dysrhythmias
•Complications: cardiac (arrythmia, dysfunction), neuromuscular (weak, tetany, rhabdomyolysis,ileus), renal (polyuria, increased ammonia, increased bicarb reabsorption), hormonal (decrease insulin and aldosterone), metabolic (negative nitrogen balance, encephalopathy if liver disease)
• treat with kcl and mgso2

Question 7

Define hypercalcaemia, presentation, ECG changes and treatment

Answer 7

•>2,6
• stones, moans, groans, bones, dehydration
• reduce qt interval
• treat if ≥ 3,2 with rehydration and forced diuresis, bisphosphonates, gincocorticoids, iv phosphate

Question 8

Define hypocalcaemia, presentation, ECG changes, 2 causes and treatment

Answer 8

•<2,2
• anxiety, convulsions, hyper reflex, Chvostek’s and trousseau sign
• prolonged qt interval
• massive blood transfusion, thyroidectomy
. Treat cacl2 or Ca gluconate

Question 9

Complication of hypomagnesaemia?

Answer 9

Torsades de pointes

Question 10

Complication of hypermagnesaemia?

Answer 10

Potentiate mitral regurg

Question 11

Name 4 uses magnesium intra-op

Answer 11

•Bronchodilation
• lower bp
• adjuvant regional blocks and pain management
• phaeochromocytoma

Question 12

Name 4 causes hyperkalaemia

Answer 12

• Less renal excretion: renal failure, decreased mineralocorticoid
• intercompartmental shift from intra to extracellular fluid: acidosis, rhabdomyolysis, excessive exercise, scolene! Burns!
• increased intake salt
• pseudo: red cell hemolysis! , marked leukocytosis or thrombocytosis
Hyperaldosterinism ( rx mineralocorticoid replacement)

Question 13

What are the 2 main electrolytes intracellularly?

Answer 13

Potassium and magnesium

Question 14

What are the 2 main electrolytes extracellularly?

Answer 14

Sodium and chloride

Question 15

Normal pH on blood gas?

Answer 15

7,35-7,45

Question 16

Normal base excess on blood gas?

Answer 16

-2 to +2

Question 17

How interpret base excess on blood gas?

Answer 17

> 2 = high amounts hco3 (alkalosis)
< -2= low hco3 (acidosis)

Question 18

Anion gap formula?

Answer 18

Na + k- Cl - hco3

Question 19

Normal anion gap on blood gas?

Answer 19

8-16 mmol/l

Question 20

Interpretation anion gap on blood gas? (3)

Answer 20

• High gap >16= acidosis
• Reduced gap <8= some unmeasured ion is present in abundance eg decreased anions like albumin, or increased cations like calcium, magnesium, lithium.
• normal gap but acidosis = loss of bicarbonate causing the acidosis. Most commonly due to hyperchloraemia

Question 21

Normal co2 on blood gas? (Paco2)

Answer 21

35-45
C02 is an acid

Question 22

Normal bicarb on blood gas?

Answer 22

22-28

Question 23

Interpretation c02 on blood gas?

Answer 23

Acidosis
• Increased >45 in respiratory acidosis
• decreased <35 could mean compensated metabolic acidosis-look at bicarb

Alkalosis
• increased >45 and increased bicarb > 28 = respiratory compensation for metabolic alkalosis
• decreased <35 in respiratory alkalosis

Question 24

Interpretation hco3 on blood gas?

Answer 24

Acidosis
• > 28= compensated respiratory acidosis if co2 >45
• < 22 = metabolic acidosis

Alkalosis
•>28= metabolic alkalosis
• <22 = compensated respiratory alkalosis if CO2 <35

Question 25

What causes increased lactate on blood gas?

Answer 25

Hypoperfusion

Question 26

Which electrolyte is main contributor to plasma osmolality?

Answer 26

Sodium

Question 27

Potassium concentration in ringer’s?

Answer 27

5 (same as plasma )

Question 28

Name 4 complications of hyperkalaemia

Answer 28

• Skeletal muscle weakness
• dysrythmia
• decreased myocardial contraction
• peaked T waves ECG

Question 29

Name 9 symptoms and signs hypokalaemia

Answer 29

I am A SIC WALT
Alkalosis
Shallow respiration
Irritability, intestinal mobility decreased, ileus
Confusion (encephalopathy), drowsy
Weakness, fatigue
Arrhythmias
Lethargy
Thready pulse
(Nausea and vomiting; tetany ; polyuria )

Question 30

Name 6 signs and symptoms hyperkalaemia

Answer 30

Murder
Muscle cramps → weak → paralysis
Urine abnormalities: oliguria
Respiratory distress
Decreased cardiac contractility → decrease bp
ECG changes, dysrhythmias
Reflexes