Kidney: Na, K Imbalance, Fluid Balance

Question 1

Initial assessment of fluid requirements

Answer 1

A-E
- low BP, high HR, RR
- high CRT or cold peripheries
- 45 deg passive leg raise suggesting fluid responsiveness

Question 2

Management of fluid resuscitation

Answer 2

Identify cause of deficit
Give 500ml crystalloid (0.9% saline or Hartmann) over 15mins and reassess
-repeat until fluid resuscitation no longer needed
If 2000ml given OR shocked => senior advice

Question 3

If fluid resus no longer needed, how would you assess fluid and electrolyte needs

Answer 3

Hx - thirst, past intake, losses, comorbidities

Examination - HR, BP, CRT, JVP, edema, postural hypotension

Monitoring - NEWS, fluid balance chart, weight

Bloods - FBC, U&E

Question 4

When would you initial routine maintenance

Answer 4

No existing or ongoing deficits/excesses?
Cannot meet fluid or electrolyte needs orally or enterally

Daily fluid and electrolyte requirements

• 25-30ml/kg/day water
• 1mmol/kg/day Na, K, Cl
• 50-100g/day glucose

0.9% saline, Hartmann, Saline 0.18% Glucose 4%, Dextrose 5%

If IV fluids needed for 3+ days => NG fluids and enteral feeding used

Question 5

When would you initiate fluid replacement

Answer 5

Existing or ongoing deficits/excesses
Cannot meet fluid or electrolyte needs orally or enterally

Prescribe fluid by adding or subtracting from routine maintenance
- assess for fluid, electrolyte deficits or excesses
- frequent monitoring and adjust

Question 6

Hyponatremia - U135
-causes related to increased water intake
-causes related to increased water reabsorption
-causes related to loss of Na

Answer 6

Increased water intake
-severe polydipsia
-inappropriate IV fluids

Increased water reabsorption
-SIADH

Loss of Na
-kidneys - diuretics, reduced CS
-sweating
-vomiting
-diarrhoea
-burns

Question 7

Hyponatremia - U135
- presentation

Answer 7

Early
-headache, dizzy, confused
-N+V, D
-muscle cramps
Late
-seizures, coma, resp arrest

Question 8

Hypernatremia - 145+
- mnemonic
- presentation

Answer 8

Medication, meals
Osmotic diuretics
DI
Excess water loss
Low water intake

Thirst, fatigue
Neurodysfunction

Question 9

Hypernatremia
-management

Answer 9

Hypovolemia
-dextrose fluid

Euvolemia
- dextrose fluid
- central DI => desmopressin
- peripheral DI => thiazides

Hypervolemia
-diuresis

Question 10

Hypokalemia
-alkalosis causes
-acidosis causes

Answer 10

Alkalosis
- vomiting
- thiazide, loop diuretics
- Cushing, Conns

Acidosis
- diarrhoea
- renal tubular acidosis
- acetazolamide
- partially treated DKA, excess insulin

Question 11

Hypokalemia ECG signs

Answer 11

ST depression, T small/absent
U waves
PR QT elongation

Question 12

Hypokalemia
- presentation
- management

Answer 12

7Ls
- lethargy
- low shallow resp, failure
- lethal cardiac dysrrythmias
- lots of urine - decreased response to ADH
- leg cramps
- limp muscles
- low BP

Asymptomatic/no ECG changes/mild/moderate (2.5-3.4) - PO K
ECG changes/severe (U2.5) - cardiac monitoring + diluted K infused over 20mmol/hr max

K sparing diuretics if hypervolemic

Question 13

Hyperkalemia causes

Answer 13

AKI
Drugs - spironolactone amiloride, triamterene, cimetedene, ACEi, ARB, Bb, ciclosporin, heparin
Metabolic acidosis
Addisons
Rhabdomyolysis/TLS
Massive blood transfusion

Question 14

Hyperkalemia ECG changes

Answer 14

Tented T
No P
Broad QRS
Sinusoidal => asystole

Question 15

Hyperkalemia
- presentation
- management

Answer 15

Muscle weakness
Urine ouput little/none => AKI
Resp failure => from muscle weakness
Decreased cardiac contractility => weak pulse, low HR
Early muscle twitches
Reflex changes

ECG first!
IV Ca gluconate - stabilise cardiac IF ECG CHANGES OR 6.5+

Insulin dextrose infusion
-can use neb salbutamol

Remove K
-Ca resonium/zirconium cyclosilicate
-dialysis if AKI with persistent high K

Stop exacerbating drugs
Treat underlying cause

Question 16

Causes of pseudohyperkalemia

Answer 16

Traumatic bloods taken
Delay between collection and processing

Question 17

Causes of SIADH
-malignancy
-infections
-neuro
-drugs

Answer 17

Malignancy
-small cell lung
-pancreatic, prostate

Infections
-CAP
-atypical pneumonias

Neuro
-SAH
-CVA
-meningitis

Drugs
-SSRI
-carbemazepine
-PPI
-NSAIDs

Question 18

Steps needed to assess hyponatremia

Answer 18

1. Serum osmolarity
   -hypoosmolar => genuine lowNa
   -normal osmolarity => pseudohyponatremia
   -high lipids - hyperlipidemia?
   -high proteins - myeloma?
   -hyperosmolar - 2Na + glucose + urea
   -high glucose - HHS?
   -high urea
2. Fluid status
   -dehydrated - lowNa
   -euvolemic - excess water
   -edematous - CCF, hypoalbuminemia (cirrhosis, nephrotic)
3. Urinary sodium
   -high => renal cause
   -low => extrarenal cause

Question 19

Causes of true hyponatremia divided by fluid status and source

Answer 19

Dehydrated - Urinary Na 20+
-diuretics
-adrenal insufficiency

Dehydrated - Urinary Na U20
-sweating
-vomiting
-dirrhoea
-burns

Euvolemic - Urinary Na 20+
-SIADH

Euvolemic - Urinary Na U20
-polydipsia
-inappropriate IV fluids

Edematous - Urinary Na 20+
-renal failure

Edematous - Urinary U20
-CCF
-nephrotic
-cirrhotic

Question 20

Management of hyponatremia based on fluid status

Answer 20

Dehydrated
-IV 0.9% saline

Euvolemic
-fluid restriction - 1-1.2L/day
-demeclocycline/vaptan - ADH antagonists

Edematous
-fluid restriction - 1-1.2L/day
-treat underlying cause

If acute with severe symptoms
-hypertonic saline 3%
-CLOSE MONITORING FOR CPM

Question 21

Central pontine myelinolysis
-why does this happen
-presentation
-how to avoid this

Answer 21

Rapid correction of Na => water moves out of brain into vasculature
-brain cells become dehydrated and injured => demyelination

Presents after 2 days, irreversible
-dysphagia
-paralysis
-seizures
-confusion
-coma

Ensure Na is increased by 4-6mmol/l in 24hrs