W10 Practise lecs on Nutrition (SG) Flashcards
IV Fluid Management, Electrolytes, Oral Enteral Parenteral Nutrition, Anaemias
Normal physiology:
Fluid intake and output
*Intake is controlled by thirst; excretion is controlled by ADH/vasopressor → water reabsorption
*Total fluid intake for adults: 25-30mL/Kg/day
*Urine output: approximately: 0.5-1mL/ kg/hour
Insensible losses
*Perspiration ~900mL/day
*Exhaled moisture from lungs ~400mL/day
*Water lost through faeces ~200mL/day
Assess the patient-algorithm 1
What do you assess?
Fluid balance
blood pressure, heart rate
Capillary refill time
NEWS
Passive leg raising
Serum electrolytes
Hypovolaemia Symptoms:
HR- Tachycardia
BP- HYPOtensive
Jugular venous pressure- Decreased
Mucous membrane- Dry
Peripheries- Cool to touch
Skin tugor (elasticity)- Decreased, sunken eyes
CRT- Prolonged
Daily weight- Weight loss
Hypervolaemic (Fluid overload) Symptoms:
HR: Tachychardia
BP: HYPERtensive
Jugular venous pressure- Increased
Peripheries- Warm to touch, oedematous
Skin turgor (elasticity)- Increased, peripheral or pulmonary oedema
Daily Weight- Weight gain
Physiology in dehydration:
Sepsis- Vasodilation
Trauma- Major blood loss
Severe burns- Loss of plasma
Vomiting & Diarrhoea- Loss of electrolytes
Physiology in fluid overload
Terminology for where fluid overload occurs:
*The third extravascular space= non-
functional collection in interstitial space
developing in edema
*Peritoneal cavity→ ascites
*Pleural cavity → pleural effusion
*Pericardial cavity → pericardial effusion
*Joints → joint effusion
Types of fluids: CRYSTALLOID- SMALLER MOLECULES
Water with added salts and glucose
* 1L of 0.9% NaCl (Iso)
* 1L of 5% glucose (hyper)
* 0.18% sodium chloride in 4%
glucose (hypo+hyper)
* Hartmann’s solution (isotonic)
Types of fluids: Plasma-lyte 148 (Iso) 140mm
Larger molecules which remain in intravascular space for longer thus theoretically aids fluid retention
Human albumin- For patients with decompensated liver disease. Albumin increases plasma volume through oncotic pressure drawing in and retaining fluid (anaphylaxis risk)
Tonicity and Osmolality: Definitions
What is a solvent?
What is osmolality?
What is osmolarity?
- Solvent: substance that can dissolve a solute → dissolving sugar in coffee
- Isotonic fluids have the same concentration of solutes as in plasma
- Osmolality is measure of solute concentration per unit mass of solvent. It is critical this matches blood plasma (mOsm/kg) →grams of sugar dissolved in kilograms of coffee
- Osmolarity is the measure of solute concentration per unit volume of solvent (mOsm/L) → grams of sugar dissolved per Litre of coffee
What should be used for fluid resuscitation?
-
Isotonic fluids should be used for fluid resuscitation
* Prescribed as boluses to rapidly correct fluid status (fluid challenge):
* 500mL over 15mins stat, reassess and prescribe and Rx 250-500ml again as needed (three- four times)
* Use crystalloids that contain sodium in the range 130–154 mmol/L
* Consider human albumin solution 4–5% for fluid resuscitation only in patients with severe sepsis. -
Passive leg raise
* Concerns about ability of the heart to respond to fluid challenge
* Patient lying flat, raise legs >45 degrees →haemodynamic improvement
→volume replacement
* If patient deteriorates → fluid overload
Algorithm 3- Routine Maintenance
- 25-30mL/kg/day of water (limit to 2.5L if possible)
- 1mmol/kg/day of Na+, K+, Cl-
- 50-100g/day glucose (glucose 5% contains 5g/100mL)
- Give less fluids in the older patients, cardiac failure or renal impairment
Algorithm 4- REPLACEMENT and REDISTRIBUTION
- Replace electrolytes and address fluid losses
- Seek expert help if patients have a complex fluid and/or electrolyte redistribution issue or imbalance, or significant comorbidity
- Reassess the patient
What are the 5Rs of Fluid Maintenance?
Resuscitation
Routine Maintenance
Replacement and redistribution
Reassessment
Potassium 3.5 – 5.3 mmol/L
- Potassium is the primary intracellular cation
- Has a vital role in cell metabolism
- A small amount is in extracellular fluids and is maintained within a narrow range
- Sodium-potassium adenosine triphosphate (ATPase) pump stands guard and maintains the balance.
- Maintenance for an adult is 1mmol/kg/day
Hypokalaemia
What are the signs and symptoms?
What drugs can cause Hypokalaemia?
What is given?
- ECG changes, arrhythmias
- Metabolic changes
- Postural hypotension
- Constipation
- Ileus
- Diuretics
- Laxatives
- Amphotericin, aminoglycosides,
- Insulin e.g. in treatment of diabetic ketoacidosis
- Caffeine, theophylline, adrenaline, salbutamol
- Magnesium depletion
- Oral/ enteral: Sando K, Kay-Cee-L
- IV Peripherally
- IV via central line
Hyperkalaemia:
What are the Signs and symptoms?
What drugs can cause hyperkalaemia?
What is the treatment?
Signs and symptoms:
* ECG changes, bradycardia
* Muscle pain, weakness, numbness
* Oliguria/ anuria
Causes
* ACEi, ARBs
* Potassium-sparing diuretics
* Renal and diabetic complications
* Lithium
* Digoxin
Treatments
* Calcium gluconate → reduce arrhythmias by antagonising cardiac membrane excitability without affecting K+ levels (protect cardiac myocytes)
* Rapid-acting insulin to shift potassium back into cells
* Remove k+ by giving diuretic (cation exchange resin if chronic); kindey filtration, correction of metabolic disease
* Prevent recurrence
What is the reference range for calcium?
function?
- 2.2-2.6mmol/L
- Most of calcium is incorporated in bones
and remaining 1% is used in neural
conduction, muscle activity and blood
coagulation. - 10% of calcium is complexed with phosphate and citrate and the remainder is
bound to proteins (mainly albumin - Maintenance for an adult is 0.1-0.2
mmol/kg/day
Hypocalcemia
Signs and Symptoms?
Causes?
Treatment?
- Hypotension
- QT prolongation
- Arrhythmia
- seizures
Causes
* Total thyroidectomy
* Partial/total parathyroidectomy
* Severe vit D deficiency
* Cytotoxic drug-induced
- Adcal, Calcichew
- Load vitamin D if depleted
- Correct magnesium first
- IV calcium gluconate with ECG monitoring, repeating until asymptomatic
- Give in glucose as sodium chloride has a calciuric effect
- Ca gluconate can precipitate arrhythmias and digitalis toxicity
Mild >1.9 mmol/L, asymptomatic
Severe <1.9 or symptomatic
Hypercalcemia:
Signs and symptoms?
Causes?
Treatment?
- Polyuria and thirst
- Nausea and vomiting
- Abdominal pain
- Constipation
- Renal stones
- Fatigue, muscle weakness
- 90% due to hyperparathyroidism or
malignancy - Drug causes: thiazides, lithium, theophylline toxicity, excessive vit A or D
- thyrotoxicosis
- Rehydration with sodium chloride (4-6 L in 24hrs)
- Haemodyalysis
- Bisphosphonates
- Off-label: steroids, denosumab, calcitonin
- Avoid thiazides and phosphate salts
mild: >3mmol/L
severe: >3.5mmol/L or symptomatic
What is the reference range for magnesium?
function?
- Magnesium (0.7 to 1.0 mmol/litre)
- Usually the first electrolyte that you need to replace.
- Magnesium is involved in energy transfer and storage, skeletal development, nerve conduction, muscle contraction
- > 50% in bone, >40% in muscle and soft tissue, 1% in extracellular fluids
- Maintenance for adults is 1mmol/kg
Hyomagnesaemia:
Causes?
Treatment?
- GI losses (diarrhoea, malabsorption)
- Malnutrition
- Chronic alcoholism
- Loop and thiazide diuretics
- PPI
- Aminoglycosides, amphotericin B
- Magnesium tablets or sachets
- Contraindicated in eGFR <30ml/min
- IV replacement using magnesium sulphate 50%
- (5 gram = 20mmol = 10mL) injection
- Administer slower if giving peripherally
Severity & Range
Mild: 0.4-0.7 mmol/L, asymptomatic
Severe: <0.4 mmol/L or symptomatic
Hypermagnesemia
Causes?
Treatment?
- Most common cause is renal failure
- Reduced GI transit time (gastroparesis),
- Lithium treatment, antacids, bowel preparations/ laxatives
- Hypothyroidism
- Concomitant hypocalcaemia
- Remove source of magnesium
- Maintain good urine output (can enhance with diuretic-not thiazide)
- Calcium gluconate 10% injection directly antagonises the neuromuscular and cardiovascular effects of magnesium.
- Calcium enhances the effect of glycosides (digoxin)
Severity & Range
Mild: 2-4 and asymptomatic
Severe: >4 mmol/L or symptomatic
What is the reference range for phosphate?
function?
- 80% of phosphorus is incorporated in skeleton as a calcium salt.
The remainder is in soft tissue, metabolic and enzymatic processes - Phosphate is regulated by renal excretion; parathyroid hormones reduce renal tubular reabsorption of phosphate
- Intestinal absorption is enhanced by vit D
Hypophosphatemia
Causes?
Treatment?
- Redistribution of phosphate into cells due to insulin therapy
- Increased urinary excretion
- Decreased intestinal absorption e.g. diarrhoea, laxative abuse, vit D deficiency, antacid abuse
- Phosphate Sandoz
- Phosphate polyfusor; dose is weight dependent
- Speed of administration of IV depends on urgency for repletion
- Correct calcium before correcting phosphate
Severity & Range
Mild >0.6 mmol/L
Moderate 0.3-0.6 mmol/L
Severe <0.3 mmol/L or symptomatic
Hyperphosphatemia
Causes? (2)
Treatment?
- Usually caused by renal failure
- Can be due to cell breakdown causing phosphate release. This would be due to rhabdomyolysis, during chemotherapy
- Treat underlying cause
- Low phosphate diet
- Phosphate binders e.g. calcium acetate or
sevelamer - Haemodialysis in renal failure
Classed as >1.5 mmol/L
What is the reference range for sodium?
function?
134-150 mmol/L
Sodium’s role in the body is to propagate nerve conduction, muscle contraction and maintain osmotic pressures through
balancing water and electrolytes.
