Fluid and electrolyte imbalance

Question 1

Explain the total body water and draw a representation of it

Answer 1

Question 2

What is the range for magnesium?

Answer 2

0.7 – 1.0 mmol/L

Question 3

What is the classification of hypERkalaemia?

Answer 3

• >7.0 mEq/L - Severe
• >6-7 mEq/L - Moderate
• >5.5 mEq/L - Mild
• 3.6 to 5.2 mEq/L - normal

Question 4

What is the normal range for phosphate?

Answer 4

The normal range in adults is 0.8-1.5 mmol/L

Question 5

What is the normal range for sodium in the body?

Answer 5

• Normal - 135-145 mEq/L
• Hypernatremia - >145 mEq/L
• Hyponatremia - <135 mEq/L
• Severe hyponatreamia <120mmol/L (cerebral oedema, seizure)

Question 6

What is the normal range for calcium?

Answer 6

Normal calcium range is around 2.2 to 2.6 mmol/L

Question 7

Causes of hypermagnesemia?

Answer 7

Excessive parenteral or oral Mg intake including laxative and antacids containing Mg salts.

Mg containing enemas and bowel cleansing preparation in patient with renal impairment

Question 8

What value does hypomagnesia show itself at? Symptoms? Cause?

Answer 8

Symptomatic hypomagnesaemia: <0.4mmol/L

SYMPTOMS:

• Neuromuscular irritability – convulsions – Arrythmias

CAUSE:

• Clinically significant disturbances are usually rare without renal failure.
• Usually secondary to GI losses such as chronic diarrhoea or high output stomas or fistula
• deficiency may also occur in alcoholism
• as a result of treatment with certain drugs.
• Hypomagnesaemia often causes secondary hypocalcaemia, and also hypokalaemia.

Question 9

What is the importance of magnesium?

Answer 9

• An important component of many enzyme systems and helps maintain enzyme stability.
• Particularly those involved in energy generation;
• The largest stores are in the skeleton.

Question 10

Explain the absorption and excretion of Mg

Answer 10

ABSORPTION:

• Mg salts are not well absorbed from the GI tract
• This is why magnesium sulfate is used as an osmotic laxative.

EXCRETION:

• Mg is excreted mainly by the kidneys
• Therefore retained in renal failure, which can result in hypermagnesaemia (causing muscle weakness and arrhythmias).
• Calcium gluconate injection is used for the management of magnesium toxicity.

Question 11

How is HYPER Mg treated?

Answer 11

Hypermagnesemia may not be treated unless the serum mg concentration is above 2mmol/L especially if asymptomatic.

Initially remove anything that can cause hyperMg e.g. fluids, laxatives, enemas etc

Calcium gluconate injection is used for the management of magnesium toxicity. This is to protect the heart. 10mL 10% slow IV injection over 5 min.

Monitor levels every 4 hours

Question 12

How to treat hypomagnesia with IV magnesium sulphate?

Answer 12

IV infusion:

• Give using a controlled infusion device (preferably a syringe pump)
• Infusion over 2 to 6 hours.
• An infusion rate of 1g MgSo4 (4mmol Mg) per hour is recommended.
• Max infusion rate (except in emergencies): 2g MgSo4 (8mmol magnesium) per hour.
• Higher infusion rates of up to 9g MgSo4 (36mmol mg) per hour e.g. in critical care, or in the management of emergencies at ward level.

Monitoring:

• Monitor BP, RR, HR, urinary output, ECG
• Signs of HYPERmagnesaemia (signs include flushing, thirst, respiratory depression, N&V, loss of patellar reflexes, drowsiness, double vision, slurred speech, hypotension, bradycardia and coma).
• Hypocalcaemia.
• Phlebitis.
• Severe acute asthma: Monitoring of blood pressure and heart rate during administration is advised due to the risk of hypotension.
• In patients with underlying cardiac issues - ECG
• The rate should be reduced if the patient becomes bradycardic.

Magnesium sulfate 50% must ALWAYS be diluted before use (refer to dilution section below).

OTHER - Oral

Mg aspartate: 10–20 mmol daily, taken as 1–2 sachets of Magnaspartate® powder.

Question 13

What other indications are there for the administration of Magnesium?

Answer 13

Severe acute asthma, continuing respiratory deterioration in anaphylaxis (UL)

• IV infusion: 1.2-2g magnesium sulfate (4.8-8mmol magnesium) over 20 minutes.

Emergency treatment of serious arrhythmia

• IV infusion: 2g magnesium sulfate (8mmol magnesium) over 10-15 minutes.

Treatment and prevention of seizures in pre-eclampsia

• Initially by IV injection (loading dose:) 4g magnesium sulfate (16mmol magnesium) over 5-15 minutes followed by:
• IV infusion (maintenance dose): 1g magnesium sulfate (4mmol magnesium) per hour for 24 hours.

For peripheral administration, a max concentration of magnesium sulfate 5% is recommended. For prevention and treatment of seizures in pre-eclampsia, magnesium sulphate 10% or 20% solution is frequently used due to fluid restriction.

Concentrations over 5% have a high osmolarity and may cause venous irritation and tissue damage in cases of extravasation. If a central venous access device is unavailable, administer via a large peripheral vein monitoring insertion site closely using a recognised phlebitis scoring tool. Re-site cannula at first signs of inflammation.

Question 14

How many millimoles of sodium is in a one-litre bag of 0.9% normal saline?

• 74
• 104
• 134
• 154
• 284

Answer 14

154

Question 15

Give examples of fluid in CHILDREN

Answer 15

Potassium Chloride 0.15% and NaCl 0.9%

Potassium Chloride 0.15% and Glucose 5%

Sodium Chloride 0.45% and Glucose 5%

Question 16

Examples of fluid and when to use

Answer 16

Sodium chloride 0.9% (Normal saline)

• Isotonic
• Used for resuscitation and/or maintenance

Compound Sodium Lactate - Hartmann’s solution

• Isotonic
• Used for resuscitation and/or maintenance
• K/bicarb loss
• Used in vomiting/diarrhoea as patients are also losing K

Sodium chloride 0.18% / Glucose 4%

• Hypotonic
• Used for maintenance

5% Dextrose

• Hypotonic
• Used for maintenance

Potassium Chloride 0.3% and Glucose 5%

• Used for replacement
• Usually given together as glucose has an indirect, body produces increased insulin which decreases potassium in the body ,

Potassium Chloride 0.3% and Sodium Chloride 0.9%

• Used for replacement
• either 20mmol or 40mmol in bag

Question 17

What 3 types of fluid replacement is there?

Answer 17

Acute Resuscitation fluids (Assess volume status - when hypovolaemia):

• Who: Patients actively bleeding (haemorrhage, surgery), GI losses (D&V), burns, severe sepsis, pancreatitis.
• These patients need urgent restoration and maintenance of circulating volume to maintain the function of vital organs.
• Administer an initial 500 ml bolus of a crystalloid solution (e.g NaCl 0.9%/Hartmann’s solution) over less than 15 minutes
• Reassess using ABCDE and IF ongoing hypovolemia, give a further 250-500 ml bolus of a crystalloid solution, then reassess.
• Repeat this process if there is ongoing clinical evidence suggestive of the need for fluid resuscitation up until you’ve given a total of 2000 ml of fluid.
• Once haemodynamically stable, so no further resuscitation fluids are required. Check blood to check if the patient needs replacement.

Factors to consider i.e. more cautious (smaller boluses/250ml):

• Heart failure
• Renal failure
• Elderly

Routine Maintenance fluids:

• e,g. bowel obstruction, pre-operative period
• Haemodynamically stable their daily fluid and electrolyte requirements
• 25-30 ml/kg/day of water and
• ~1 mmol/kg/day of potassium, sodium and chloride and
• ~50-100 g/day of glucose to limit starvation ketosis (however note this will not address the patient’s nutritional needs)
• Obese patients – use IBW and lower range of volume per kg (25ml/kg). Patient rarely need >3L/day
• Elderly/Renal impairment/cardiac failure/malnourished patient at risk of refeeding syndrome - 20-25 ml/kg/day
• Monitor: Bloods: electrolytes/renal function/haemoglobin

Replacement and redistribution of fluids:

• Different to routine maintenance fluids. Patient has one or more of the following:
  
  • Existing fluid or electrolyte deficits or excesses [dehydration/overloaded/hyper/hypokalaemia]
  • Ongoing abnormal fluid or electrolyte losses [vomiting/diarrhoea/stoma/blood loss/urinary loss/fever/biliary drainage loss]
  • Redistribution and other complex issue [fluid in the wrong compartment/gross oedema/severe sepsis/hyper/hyponatraemia/renal/liver/cardiac impairment/ post-operative fluid retention/malnourishment]
• Calculate how much fluid has been lost. Using the NICE chart calculate approx. the electrolyte lost as a result of fluid loss. Adjust this value by taking into consideration how much fluid has already been given. Check if there will be ongoing losses over the next 24h. if unable to take in maintenance.

Question 18

What are the THREE categories of fluids?

Answer 18

CRYSTALLOIDS:

• solutions of small molecules in water
• (e.g. sodium chloride, Hartmann’s (more close to normal), dextrose)
• superior in initial fluid resuscitation

COLLOIDS:

• solutions of larger organic molecules
• (e.g. albumin, Gelofusine)
• expands intravascular space with a longer duration of action
• Used less as a higher risk of anaphylaxis

BLOOD PRODUCTS:

• Packed red cells
• Platelets
• Fresh frozen plasma

Question 19

Medication that affects SODIUM?

Answer 19

Medication that can affect SODIUM:

• Diuretics,
• ACE inhibitors

Consider stopping other drugs that may be associated with SIADH:

• SSRI
• Carbamazepine
• Desmopressin
• Phenothiazines
• Tricyclic antidepressants
• Cyclophosphamide
• Opioids
• Vincristine
• NSAIDS
• Clofibrate
• Proton pump inhibitor

*though this is often not appropriate or possible e.g. anti-epileptics.

Question 20

What types of patient are high risk of hyponatreamia?

Answer 20

• Postoperative patients.
• Diuretic use.
• Alcohol excess.
• Malnourished patients.
• Psychogenic polydipsic patients.
• Older patients or those with multiple comorbidities and multiple medications.
• Burns patients.

Question 21

Fluid status - 3 classes

Answer 21

False hyponatraemia can occur

Need to assess overall fluid/water balance

Question 22

When to treat hyponatraemia?

Answer 22

Hypernatremia:

• > 48 hrs duration chronic; Assume chronic unless evidence to contrary
• The rate of correction of hyponatremia should generally be a rise of 6-9mmol/L/24 hours but never exceed 10mmol/L/24 hours due to the risk of sudden osmotic shift and demyelination. (No more than 0.5-1 mmol/L every hr; Less than 18 mmol/L in 48 hrs)
• Duration of hyponatraemia is important (<48h = medical emergency)
• Asymptomatic + chronic mild hyponatremia + 125-135mmol/L = NO FURTHER INVESTIGATION/Tx/GP REFERRAL.
• Symptomatic + <130mmol/L OR Asymptomatic + <125mmol/L = Tx
• In severe hyponatraemia (Na<110mmol/L) or neurological compromise, urgent correction with 3% Saline
• (irrespective of the cause) in ITU setting
• Fluid restriction should be the main stay of treatment for all other causes of hyponatremia

Question 23

MEDICAL EMERGENCY - Hyponatreamia (acute)

Answer 23

Acute onset (<48 hrs), life threatening hyponatraemia with fitting or other neurological deficits e.g. seizures

MEDICAL EMERGENCY

• Administer an intravenous bolus of 150mLs of hypertonic sodium chloride solution (2.7%), through an infusion pump over 20 mins. Administration via central venous line recommended to prevent risk of extravasation*
• Check the serum sodium after 20 mins
• Then repeat another infusion of 150mL 2.7% sodium chloride for the next 20 mins.
• Repeat above recommendations twice or until a target of 5 mmol/l increase in serum sodium concentration is achieved.
• This will need frequent sodium monitoring and only in an HDU setting. Initiation of treatment upon urgency in high intensity patient care areas, such as A&E resuscitation bay, AMU acute care bay, should be continued under HDU setting.
• Limit the rise of serum sodium concentration to a total of 10 mmol/l during the first 24 hours and an additional 8 mmol/l during every 24 hours thereafter until the target.
• Higher concentrations and volumes are occasionally used by specialists under near continuous monitoring but are associated with an increased risk of permanent neurological damage and death.
• * Consider peripheral administration through a large bore cannula when timely administration is necessary or central access isn’t clinically appropriate. Observe carefully for signs of extravasation.

Question 24

When looking at a patient’s urea and electrolytes levels, you notice that the potassium level is 2.7 mmol/L. Which of the patient’s regular medications could cause this low potassium level?

Aspirin
Atorvastatin
Salbutamol nebs
Lactulose
Soluble paracetamol

Answer 24

The correct answer was Salbutamol nebs

Hypokalaemia may result from beta2 agonist therapy.

Question 25

List medications that can cause hyperkalaemia

Answer 25

• Potassium supplements.
• ACEi / ARB, aliskiren (renin-inhibitor).
• NSAIDs.
• Nonselective beta-blockers (e.g., labetalol).
• Potassium-sparing diuretics (amiloride, triamterene, spironolactone, eplerenone).
• Antibiotics (trimethoprim, pentamidine, ketoconazole, IV penicillin G-potassium, Co-trimoxazole).
• Heparin.
• PRBC transfusion.
• Calcineurin inhibitors (cyclosporine, tacrolimus).
• Digoxin toxicity, succinylcholine.
• Normal saline causing hyperchloremic metabolic acidosis.
• Theophylline

Question 26

List other causes of hyPERkalaemia (other than medications)

Answer 26

Diabetic ketoacidosis, hyperglycemic hyperosmolar non-ketotic syndrome (HHNS).

Renal failure, primarily if there is: Oliguria.;GFR <15 ml/min.

AKI

Catabolic state

Tissue injury/damage

Question 27

Explain the treatment of hypERkalaemia

Answer 27

Stop medication that maybe cause hypERkalaemia

This treatment will on treat hyperkalaemia acutely and the body can potentially rebound after treatment. Therefore monitoring potassium is important, in addition to finding the cause.

If all fails - dialysis may be required.

https://gpnotebook.com/en-gb/simplepage.cfm?ID=-1972699118&linkID=57164

Question 28

What do you need to monitor in hypERkalamia?

Answer 28

Glucose: (0, 15, 30, 60, 90, 120, 180, 240, 300, 360 minutes) for a min of 6h after administration of insulin-glucose infusion

ECG

We suggest that serum K+ is assessed at least 1, 2, 4, 6 and 24 hours after identification and treatment of moderate or severe hyperkalaemia

Question 29

Why is treating hyperkalaemia important?

Answer 29

Potassium is important as it regulates the heart and therefore hyperkalaemia can lead to arrhythmias if untreated.

Question 30

Max rate of potassium

Answer 30

• Can not be given quickly due to effects on the heart
• usually10mmol/hr
• 20mmol or 40mmol bags are not used in acute resuscitation
• Pump is used instead of bolus to set rate

Question 31

When would you use Sodium bicarbonate in hyperk?

Answer 31

Sodium bicarbonate in hyperkalaemia

• Use to correct acidosis (if serum HCO3- is less than 20mmol/l)
• Use only if fluid overload is not a danger.
• Dose: IV infusion of 50-100mls of 4.2% sodium bicarbonate or 200-300 mls of 1.26% sodium bicarbonate. Titrate against PH or serum bicarbonate.

Sodium bicarbonate encourages the movement of extracellular potassium into cells. Traditionally its actions have been attributed to its effect on blood pH, but it may affect serum potassium without increasing blood pH. The sodium ion itself may play an important role in stimulating the uptake of potassium. Effects are observed within 30-60 minutes. This is a temporary measure. Doses may repeated as needed, especially if the patient is acidotic.

Note that there are risks associated with the use of sodium bicarbonate. These are:

• risk to patients with circulating volume overload, congestive heart failure or pulmonary oedema.
• rapid alkalinisation of the blood may precipitate tetany by lowering serum ionised calcium concentration.
• excessive administration may lead to alkalosis.

Question 32

What is the most common cause of HYPOkalaemia?

Answer 32

GI losses

Drugs (primarily diuretics)

Question 33

When is potassium loss is considered severe?

Answer 33

<2.5mmol/L

muscle weakness, paralysis, cardiac arrhythmias

Should be immediately replaced to >3mmol/L

Question 34

Mrs CB, a 65-year-old woman, suffers from depression and heart failure, and has recently been admitted into hospital. After reviewing her notes you notice her potassium level has increased to 6.5 mmol/L (range 3.5 – 5.3 mmol/L).

Which newly started medicine could have contributed to this?

• Citalopram
• Furosemide
• Indapamide
• Enoxaparin
• Salbutamol

Answer 34

Heparin may cause hyperkalaemia

D is correct. Enoxaparin, a low molecular weight heparin (LWMH), is associated with raised potassium levels by inhibiting aldosterone secretion. Aldosterone normally acts on the nephron of the kidney at the distal convoluted tubule, causing upregulation of the epithelial sodium channel (ENaC) responsible for potassium ion excretion and sodium reabsorption. Therefore a lack of aldosterone leads to accumulation of potassium ions.

A is incorrect. Citalopram does not cause hyperkalaemia but can be associated with hyponatremia (low sodium levels).The patient’s past medical history indicates that she may have already been prescribed an antidepressant.

B, C and E are incorrect. Furosemide (a loop diuretic), Indapamide (a thiazide diuretic) and Salbutamol (short acting B2 agonist) are associated with hypokalaemia (low potassium levels). For the diuretics, the risk of hypokalaemia depends on the duration of action and potency of the diuretic. As thiazides are more potent than loop diuretics hypokalaemia is more clinically important. The greatest reduction normally occurs in the first 2 weeks of treatment.

Question 35

Mrs W is a 52-years-old woman who has been admitted to the respiratory ward that you are in charge of. She has been newly prescribed theophylline 200mg every 12 hours to manage her asthma. She smokes 10 cigarettes a day and does not drink any alcohol. She has no known allergies.

Which of the following is correct regarding the theophylline dose adjustment, if Mrs W stops smoking?

• the dose should not be altered
• the dose should be decreased as smoking reduces clearance
• the dose should be increased as smoking reduces clearance
• the dose should be decreased as smoking increases clearance
• the dose should be increased as smoking increases clearance

Answer 35

the dose should be decreased as smoking increases clearance

Question 36

A 24-year-old woman was diagnosed with asthma 4 months ago and has been using a salbutamol 100 microgram inhaler (2 puffs QDS PRN breathlessness). She complains of a worsening cough, palpitations and tremor. She then reports that she has been experiencing the cough around 2 nights a week and explains that her blue inhaler has helped reduce the night time cough.

Which of the following options is most appropriate?

• Add oral prednisolone 40 mg daily
• Prescribe salbutamol at a dose of 100 micrograms, 4 puffs BD
• Counsel the patient on salbutamol overuse and add Clenil Modulite® at a dose of 100 mcg, 2 puffs BD
• Counsel the patient on salbutamol overuse and add Qvar Easi-breathe® at a dose of 100 mcg 2 puffs BD
• Counsel the patient on salbutamol overuse and add Qvar Autohaler® at a dose of 100 mcg, 4 puffs BD

Answer 36

C is correct. Salbutamol was being excessively used indicated by the palpitations and tremors. Salbutamol is a short-acting-B2-agonist (SABA), acting on the sympathetic nervous system causing these symptoms. In accordance with the British Thoracic Society (BTS) or NICE guidelines, a low dose corticosteroid should be added if adult patients are woken at night by asthma symptoms once weekly or more, and/or they have asthma symptoms three times a week or more, and/or they use an inhaled SABA three times a week or more. Clenil Modulite® contains beclomethasone dipropionate, and at a dose of 100 micrograms, 2 puffs BD this is classified as a low dose.

D is incorrect. Beclomethasone dipropionate metered-dose inhalers (Qvar® is more potent than Clenil Modulite®) are not interchangeable. Qvar® preparations contain extra-fine particles and as a result of the formulation it is approximately twice as potent. A dose of 100 micrograms, 2 puffs BD is classified as a BTS Medium dose, not Low dose. Therefore inhalers containing beclomethasone are prescribed by brand. For more information see BTS at: https://www.brit-thoracic.org.uk/quality-improvement/guidelines/asthma/

E is incorrect. Qvar Autohaler® at a dose of 100 micrograms, 2 puffs BD is also classed as a Medium dose.

A is incorrect. Oral Prednisolone (dose 40 to 50 mg) is prescribed for an acute asthma attack for at least 5 days in adults (and 3 days for children > 2 years old) until recovery. Oral corticosteroids have greater systemic side-effects than inhaled corticosteroids and therefore would not be used long-term due to the risk of adrenocortical suppression, in which the body fails to manufacture endogenous corticosteroids.

B is incorrect. The patient is already overusing salbutamol and four x 100 microgram puffs is not licensed for each dose (Each maximum dose: 100 micrograms – 200 micrograms, up to 4 times a day)

Question 37

Mrs W is a 52-years-old woman who has been admitted to the respiratory ward that you are in charge of. She has been newly prescribed theophylline 200mg every 12 hours to manage her asthma. She smokes 10 cigarettes a day and does not drink any alcohol. She has no known allergies.

What is the ideal range for plasma theophylline concentration that should be maintained?

• 0-10mg/L
• 1-10mg/L
• 10-20mg/L
• 10-100mg/L
• 10-20g/L

Answer 37

10-20mg/L