Electrolytes And Blood Gas Flashcards
What is the normal serum potassium?
3,5 mm - 5 mmol
When must hyperkalaemia be treated?
If >6 mmol
How is hyperkalaemia treated (5) (“potassium shift”)
- Stop all sources eg ringer’s
- Promote excretion if K > 6,5. Use loop diuretic (furosemide)! or sodium polystyrene sulphonate (kayexelate)!
- If K > 6,5 NB to antagonise cardiac effects with Cacl2! Or calcium gluconate
- Promote moment of K into cells with insulin plus dextrose!, treat metabolic acidosis with NaHCO3, B agonists! (Nebulise salbutamol) and hyperventilation!
- Treat refractory hyperkalaemia with dialysis
Other: Cation exchangers (kayexelate)
How will hyperkalaemia of >5,5 mmol affect surgery?
No elective surgery!
What is hypernatraemia and what are some causes and treatment in hypo, Normo and hyper volaemia?
• > 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!
What is hypokalaemia and what are 3 causes , ECG changes, 5 complications and treatment?
•<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
Define hypercalcaemia, presentation, ECG changes and treatment
•>2,6
• stones, moans, groans, bones, dehydration
• reduce qt interval
• treat if ≥ 3,2 with rehydration and forced diuresis, bisphosphonates, gincocorticoids, iv phosphate
Define hypocalcaemia, presentation, ECG changes, 2 causes and treatment
•<2,2
• anxiety, convulsions, hyper reflex, Chvostek’s and trousseau sign
• prolonged qt interval
• massive blood transfusion, thyroidectomy
. Treat cacl2 or Ca gluconate
Complication of hypomagnesaemia?
Torsades de pointes
Complication of hypermagnesaemia?
Potentiate mitral regurg
Name 4 uses magnesium intra-op
•Bronchodilation
• lower bp
• adjuvant regional blocks and pain management
• phaeochromocytoma
Name 4 causes hyperkalaemia
• 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)
What are the 2 main electrolytes intracellularly?
Potassium and magnesium
What are the 2 main electrolytes extracellularly?
Sodium and chloride
Normal pH on blood gas?
7,35-7,45
Normal base excess on blood gas?
-2 to +2
How interpret base excess on blood gas?
> 2 = high amounts hco3 (alkalosis)
< -2= low hco3 (acidosis)
Anion gap formula?
Na + k- Cl - hco3
Normal anion gap on blood gas?
8-16 mmol/l
Interpretation anion gap on blood gas? (3)
• 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
Normal co2 on blood gas? (Paco2)
35-45
C02 is an acid
Normal bicarb on blood gas?
22-28
Interpretation c02 on blood gas?
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
Interpretation hco3 on blood gas?
Acidosis
• > 28= compensated respiratory acidosis if co2 >45
• < 22 = metabolic acidosis
Alkalosis
•>28= metabolic alkalosis
• <22 = compensated respiratory alkalosis if CO2 <35
What causes increased lactate on blood gas?
Hypoperfusion
Which electrolyte is main contributor to plasma osmolality?
Sodium
Potassium concentration in ringer’s?
5 (same as plasma )
Name 4 complications of hyperkalaemia
• Skeletal muscle weakness
• dysrythmia
• decreased myocardial contraction
• peaked T waves ECG
Name 9 symptoms and signs hypokalaemia
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 )
Name 6 signs and symptoms hyperkalaemia
Murder
Muscle cramps → weak → paralysis
Urine abnormalities: oliguria
Respiratory distress
Decreased cardiac contractility → decrease bp
ECG changes, dysrhythmias
Reflexes
