Kidneys: Na, K imbalances and fluid management

Question 1

Initial assessment of fluid requirements

-when would a patient need fluid resus?

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

-how would you manage fluid requirements

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

-how would you manage fluid requirements

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

• high urinary Na causes
• low urinary Na causes

Answer 6

High urinary Na
Na depletion due to renal loss
-diuretics
-Addisons
-ESRF
-SIADH
-hypothyroidism

Low urinary Na
Na depletion due to extrarenal loss or increased fluid
-diarrhoea, vomiting, sweating
-burns, rectal adenomas
-edema
-psychogenic polydipsia

Question 7

Hyponatremia - U135

• presentation
• management

Answer 7

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

Acute hyponatremia

• hypertonic saline
• readjust Na slowly to prevent CPM

Chronic hyponatremia
Hypovolemia => isotonic saline
Euvolemia, hypervolemia => fluid restriction, address cause

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, 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 changes

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

Fluid resus if needed
K replacement
K sparing diuretics if hypervolemic

Question 13

Hyperkalemia

-causes

Answer 13

AKI
Drugs - K sparing diuretics, ACEi, ARB, Bb, ciclosporin, heparin
Metabolic acidosis
Addisons
Rhabdomyolysis
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
Rhythm changes

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

Insulin dextrose infusion
-can use neb salbutamol

Remove K
-Ca resonium/loop/dialysis

Stop exacerbating drugs
Treat underlying cause