PERI - Fluid Prescription and Nutrition Flashcards
5 reasons patients need IV fluids
1.) Nil By Mouth
2.) Malfunctioning GI Tract
3.) Dehydration
4.) Fluid Losses
5.) Abnormal Electrolytes
Assessing Clinical Dehydration/Hypovolaemia
Inspection
Palpation
Observations
1.) Inspection
- cyanosis, pallor, dry mucous membrane, sunken eyes
2.) Palpation
- cold hands, increased CRT (>2s), ↓ skin turgor
- weak thready pulse,
3.) Observations
- hypotensive, tachycardia, reduced urine output
- raised haematocrit, raised urea, raised sodium
Causes of changes in osmolality
Normal/Increased Serum w/ ↑ Urine Osmolality
Normal/Increased Serum w/ ↓Urine Osmolality
Decreased Serum w/ ↑ Urine Osmolality
Decreased Serum w/ ↓ Urine Osmolality
1.) Normal/Increased Serum w/ ↑ Urine Osmolality - anything that causing ↑ concentration of urine
- dehydration, DM/hyperglycaemia
- hypercalcaemia, hypernatraemia, uraemia
- renal disease, addison’s disease, alcohol, mannitol
2.) Normal/Increased Serum w/ ↓Urine Osmolality
- diabetes insipidus (dilution of urine)
3.) Decreased Serum w/ ↑ Urine Osmolality
- SIADH
4.) Decreased Serum w/ ↓ Urine Osmolality
- overhydration, hyponatraemia, addison’s disease
- sodium loss: diuretic, low salt diet
Causes of ongoing fluid losses
Pure Water
Vomiting and NG Tube
Diarrhoea
Inappropriate Urinary Loss
Stoma/Fistula
Blood Loss
1.) Pure Water Loss - insensible losses
- e.g. fever, dehydration, hyperventilation
- low electrolyte content, possible hypernatraemia
2.) Vomiting and NG Tube Loss - lose H+ ions
- causes hypokalaemia metabolic alkalosis
3.) Diarrhoea
- lose HCO3- so causes metabolic acidosis
4.) Inappropriate Urinary Loss - e.g. polyuria
5.) Stoma/Fistula
- loss from colon from colostomy (like diarrhoea)
- loss from ileum from ileostomy or fistulae
- loss from jejunum from stoma or fistulae
6.) Ongoing Blood Loss - GI or PR bleeding
Bowel Obstruction and Fluid Losses
Cause of Fluid Losses
Gut Capacity
Hypovolaemic Shock
Effect on Electrolytes
1.) Cause of Fluid Losses - SI obstruction leads to:
- accumulation of fluids, increased secretion and decreased reabsorption
2.) Gut Capacity - in bowel obstruction the gut can sequester 3-4 litres of isotonic fluid
- vomiting leaves space for more to be sequestered
3.) Hypovolaemic Shock
- can lose up to 7L of fluid from their ECF
- raised haematocrit and serum urea are useful indicatiors of dehydration in this context
4.) Effect on Electrolytes - isotonic hypovolaemia
- hypochloremic, hypokalemic, metabolic alkalosis
- vomitng leads to loss of H+ –> metabolic alkalosis
- renal compensation for alkalosis –> hypokalaemia
Post-operative Phase (first 3 days)
Oliguria and Sodium Retention
Why is Potassium not Given?
1.) Oliguria and Sodium Retention - due to the physiological stress response
- ↑aldosterone, ↑ADH release –> salt/water retention
- should be temporary and only last 24 hrs, if not ?AKI and ?urinary retention
Why is potassium not given?
- hyperkalaemia –> aldosterone release –> which makes oliguria and sodium retention worse
Fluids Compartments
1.) Total Body Water - 2/3 of body weight
- 70kg man has 42L of water
2.) Intracellular Fluid - 2/3 of total body water
- 70kg man has 28L in ICF
3.) Extracellular Fluid - 1/3 of total body water
- 70kg man has 14L in ECF
- intersitial fluid: 75% of ECF (10L)
- intravascular fluid: 25% of ECF (3.5L)
5 features of giving 1L of 5% dextrose
Glucose Content
Osmolarity
Osmolarity Change
Fluid Displacement
1L of Blood Replacement
1.) Glucose Content - contains 50g of glucose
- glucose is rapid taken up by cells so hyperglycaemia can occur if infusion rate > uptake and metabolism
2.) Osmolarity is 278 mOsm/kg
3.) Osmolarity Change - reduces for all compartments
- glucose rapidly enters the ICF and the free water is distributed in all compartments, reducing osmolarity
4.) Fluid Displacement - enters ICF and ECF
- 2/3 ICF = 666ml, 1/3 ECF = 333ml
- interstitium = 75% of ECF = 250ml
- intravascular = 25% of ECF = 84ml
5.) 1L of Blood Replacement - need 12L of dextrose
(84ml x 12)
5 features of giving 1L of 0.9% saline
Tonicity
Osmolarity
Osmolarity Change
Fluid Displacement
1L of Blood Replacement
1.) Isotonic - contains 154 mM of Na+ and Cl- ions
2.) Osmolarity - 308 mOsm/kg
3.) Osmolarity Change - No change in all compartments
- isotonic solution so doesnt affect osmolarity
4.) Fluid Displacment - only enters the ECF
- doesn’t enter ICF due to no change in osmolarity
- interstitium = 75% of ECF = 750ml
- intravascular = 25% of ECF = 250ml
5.) IL of Blood Replacement - need 4 litres of saline (250ml x 4)
5 features of giving 1L of Hartmann’s solution
Contents
Osmolarity
Osmolarity Change
Fluid Displacement
1L of Blood Replacement
1.) Contents - composition closer to normal blood fluid
- 131 mM of sodium, 111mM of chloride
- 5mM of potassium, 2mM of calcium
- 29mM of bicarbonate as lactate
2.) Osmolarity - 280 mOsm/kg
3.) Osmolarity Change - no change in all compartments
- osmolarity is maintained with effective osmoles of sodium, potassium, and calcium
4.) Fluid Displacement - only enters ECF
- doesn’t enter ICF due to no change in osmolarity
- interstitium = 75% of ECF = 750ml
- intravascular = 25% of ECF = 250ml
5.) IL of Blood Replacement - need 4 litres of Hartman’s (250ml x 4)
Fluid Prescribing
Substances Lost
Replacement Doses
Routine Maintenance
Fluid Resucitation
1.) Substances Lost
- fluids: urine (1-2.5L/day), insensible losses (50ml/h)
- water, electrolytes (Na, Cl, K), glucose
2.) Replacement Doses
- water: 25-30ml/kg/day (<30 if frail, renally impaired)
- electrolytes: Na and Cl (1mM/kg/day), K (0.5mM)
- glucose: 50-100g/day (avoid starvation and ketosis)
3.) Routine Maintenance - given day 1
- 25-30 ml/kg/day of NaCl 0.18% in 4% glucose
- add 27 mM potassium
4.) Fluid Resuscitation
- IV Saline (0.9%) bolus of 500ml over 15 minutes
- 250ml over 10 mins (elderly/frail, HF)
- repeat boluses up to 4 times for at risk patients
- after each bolus, reassess for signs of overload
Routes of Enteral Feeding
Oral
Nasogastric
Nasojejunal
Gastrostomy
Jejunostomy
1.) Oral - if normal GI tract
2.) Nasogastric - tube feeding into stomach
- for patients unable to tolerate swallowing
3.) Nasojejunal - tube feeding into the jejunum
- upper GI dysfunction or inaccessible upper GI tract
4.) Gastrostomy - surgical or PEG (percutaneous endoscopic gastrostomy)
- for long term (4wks+) enteral tube feeding
5.) Jejunostomy - stoma into jejunum
- alternative to gastrostomy
Nutrition
Daily Calorie Requirements
Starvation Before Surgery
Additional Demands of Surgery
Nutritional Routes
1.) Daily Calorie Requirements
- 2000 (women) to 2500 (men) calories per day
2.) Starvation Before Surgery - to prevent pulmonary aspiration of food due to general anaesthetic
- however, it makes it harder for bodies to tolerate the invasive procedures, anaesthetics and other drugs
- food 6hrs before, fluids 2 hrs before surgery
3.) Additional Demands of Surgery - good nutrition to:
- replace blood loss, heal incisions, prevent infections, increase energy levels, repair wounds
4.) Nutritional Routes
- enteral: into GI tract, preferred but not always feasible (e.g.) ileus, fistula, small bowel resection
- parenteral: IV, TPN, (total parenteral nutrition)
Lecture
Colloids are protein/starch that enter the vessels and stay there, drawing fluid into the vessels but has longer term side effects
1% = 1g per 100mls
Total Parenteral Nutrition
What is it?
Complications/Regular Monitoring
Thiamine Deficiency
1.) What Is It?
- contains a mix of fluid, macro/micronutrients
- if the GI tract is inaccessible or not working
- given via dedicated central line (PICC or Hickman)
2.) Complications/Regular Monitoring
- infection: 4hrly obs, line/dressing inspection
- hyperglycaemia: high sugar content, check BM
- fluid imbalance: accurate fluid balance recording
- electrolyte imbalances: daily U&Es
3.) Thiamine Deficiency - due to starvation
- thiamine is needed to process food
- causes Wernicke’s encephalopathy: confusion, ataxia, ophthalmoplegia
- if untreated —> Korsakoff’s psychosis —> dementia
- IV Pabrinex (mix of vitB and vitC) given for prevention
