MEDI7302 Study Guide - Final Guide: Hematoma, Thrombophlebitis, Paresthesia
Fluid and Electrolyte Management
Fluid and electrolyte management
Learning
objectives
Understand the physiology of fluid and electrolyte distribution and fluid losses in the
body
Describe the factors to consider when prescribing fluids to a surgical patient
Understand the different types of intravenous fluid preparations and how to
document a fluid order
Recognize the basic electrolyte abnormalities and how they are corrected
Normal body
composition
Body fluid composition
Total body
water (60% body weight)
oExtrace
llular fluid (20% body weight)
o
Intravascular blood +
lymphatics (5% ECF)
o
Interstitial fluid
between cells (15% ECF)
oIntrace
llular fluid (40% body weight)
Total body Na
4200mmol/L (50% in ECF)
Total body K
3500mmol/L (98% in ICF)
Solute composition
Solutes are restricted to their compartments
ICF - K, PO4, SO4
ECF - Na, Cl, HCO3
Plasma - albumin
Interstitial fluid
Water is freely diffusible between compartments such that the osmolality (solute
concentration) is identical in each compartment (serum osmolality ~290mosm/kg)
Osmolality is regulated by water intake (thirst) vs excretion (urine and insensible
losses)
Normal daily
requirements +
losses
Requirements Losses Fluid assessment in surgical patient
Water =
30-35mL/kg
7
0kg male ~2000-
2500mL
5
0kg female
~1500-1800mL
Na =
2mmol/kg ~90-
140mmol
K =
1mmol/kg ~40-
80mmol
Mg =
0.5mmol/kg
Glucose =
30kcal/kg
Kidney
(urine output) = 0.5-
1.0mL/kg/hr
70k
g male ~1500mL
50k
g female ~1000mL
Insensible
losses
GIT
(faecal) ~100mL
Res
piratory ~400mL
Ski
n/ perspiration
~500mL (however
could be less in
patient lying down
Pre-operative/ pre-
admission
Hydration status
signs = HR, BP, skin turgor,
mucous membranes, urine output
Dehydration %
Mild (<5%,
2.5L)
Mild thirst
Dry mucous
membranes
Concentrated
urine
Moderate
(5-8%, 4L)
Mild dehydration
signs
PLUS
find more resources at oneclass.com
find more resources at oneclass.com
PO4 =
0.5mmol/kg
Ca = 5-
10mmol/day
in air-conditioned
room)
Moderate thirst
Decreased skin
turgor
Increased heart
rate
Severe
(>8%, 6L)
Moderate
dehydration signs
PLUS
Hypotensive (SBP
<80mmHg)
Ongoing daily water losses
Upper GIT - vomit, NG drainage
Lower GIT - diarrhoea, stoma, fistula
3rd space - ileus (fluid in bowel), ascites (fluid in peritoneum), pleural
effusions (fluid in pleural cavity), retroperitoneal and other soft tissue oedema, surgical
drains
Skin - severe burns
Ongoing daily electrolyte losses
Na - pyrexia, diarrhoea, vomiting, high output fistulas, dextrose infusions
K - pyrexia, diarrhoea, vomiting, high output fistulas
Fluid overload signs
Pulmonary oedema and dyspnoea
Peripheral oedema (most commonly extremities)
Elevated JVP or jugular venous distension
Urinary retention (bladder palpation)
Post-bowel
surgery
recovery
First 1-2 days post-bowel surgery
Low urine output is expected due to physiologic secretion of ADH -> fluid
becomes retained in body -> IV fluid prescription to increase urine output is unnecessary
Urine output 100mL/4hrs is acceptable
Post-operative ileus is expected and can last up to 5 days
Maintenance IV fluids is the only necessary fluid prescription
Good bowel recovery
Diuresis - increase of urine output to 500-600mL/4hrs (clear and dilute
urine) due to kidneys shedding retained water
IV fluid replacement is greatly restricted (eg keep vein open order for drug
administration) OR ceased completely
Poor bowel recovery
Urine output remains unexpectedly low + dark concentrated urine signifies
major problem (eg anastomotic leak)
Observe other clinical signs (eg HR, temp, pain levels, WCC) and act
accordingly
IV fluids IV fluids should only be prescribed for patients whose needs cannot be met by oral
or enteral routes
Main goals
Resuscitation - 0.9% normal saline 500mL bolus q15, only max 2L (use in
acute setting in severely dehydrated patient, don't have to fix entire dehydration status but
at least make haemodynamically stable)
Replace deficit - % dehydration x (0.6 x weight [kg]) in isotonic fluid; give
first half in first 8hrs + second half in next 16hrs
Re-evaluate ongoing losses, NGT, fistulas, drains
find more resources at oneclass.com
find more resources at oneclass.com
Routine maintenance requirements - 30mL/kg/day + electrolytes
Indications
Fluid restriction (unable to drink or absorb via enteral route, nil by mouth)
Replace abnormal losses (eg burns, vomiting and diarrhoea)
IV drug administration (eg chemotherapeutics, antibiotics)
Parenteral feeding
Main factors for amount/ type
Level of activity - normal function, lying in hospital bed (reduce fluids)
Patient factors - age, CV reserve, renal function, surgery (eg inguinal hernia
repair, bowel resection, major burns)
oElderly, heart failure, poor renal function = reduce fluids
Fluid accumulation issues - dependent oedema (eg legs), pulmonary
oedema, urinary retention, prolonged ICU stay, increased anastomotic leakage
Main considerations
Generally, 1-2L/day is adequate for majority of patients progressing well
post-op
Justify and prescribe every L of IV fluid & cease whenever possible
Check U&E daily until stable
IV fluid types (crystalloids - small molecules in water)
Hartmann Normal saline 4% dextrose + 1/5 saline 5% dextrose
Sodium (mmol/L) 131 154 30 Nil
Chloride (mmol/L) 111 154 30 Nil
Potassium (mmol/L) 5 Nil Nil Nil
Bicarbonate (mmol/L) 29 Nil Nil Nil
Calcium (mmol/L) 2 Nil Nil Nil
Glucose (g/L) Nil Nil 40 50
IV fluid types (colloids - large organic molecules)
Human Albumex 4 40g albumin
140mmol Na
128mmol Cl
50mL water
Albumex 20 200g albumin
Synthetic Gelofusine 40g gelatin
154mmol Na
120mmol Cl
500mL water
Volvulen 6g hydroxyethyl starch
154mmol Na
120mmol Cl
500mL water
Choosing the correct IV fluid
Crystalloid Most common choice
Normal saline
Example prescription - 2 boluses of NaCl, followed by
4% dex + 1/5 NaCl
Result - excess of Na (easily compensated by kidneys),
mild metabolic acidosis (not clinically relevant)
Dextrose 5% Glucose is rapidly metabolised, hence essentially giving
a patient free water
Indication - possible hypernatremia
Generally avoided since it produces hyponatremia
Albumex Indication - albumin replacement (serum albumin <
20), sepsis (distributive shock)
Gelofusine/
Volvulen
Indication - maintain intravascular volume (eg HR and
BP stable during major bleed, sepsis etc)
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Understand the physiology of fluid and electrolyte distribution and fluid losses in the. Describe the factors to consider when prescribing fluids to a surgical patient. Understand the different types of intravenous fluid preparations and how to document a fluid order. Recognize the basic electrolyte abnormalities and how they are corrected. Intravascular blood + lymphatics (5% ecf) o o. Water is freely diffusible between compartments such that the osmolality (solute. Normal daily requirements + losses concentration) is identical in each compartment (serum osmolality ~290mosm/kg) Osmolality is regulated by water intake (thirst) vs excretion (urine and insensible losses) ~500ml (however could be less in patient lying down. Hydration status signs = hr, bp, skin turgor, mucous membranes, urine output. 3rd space - ileus (fluid in bowel), ascites (fluid in peritoneum), pleural effusions (fluid in pleural cavity), retroperitoneal and other soft tissue oedema, surgical drains. Na - pyrexia, diarrhoea, vomiting, high output fistulas, dextrose infusions. K - pyrexia, diarrhoea, vomiting, high output fistulas.
