BASIC FLUIDS AND
ELECTROLYTES
Douglas P. Slakey
Why ?
 Essential for surgeons (and all physicians)
 Based upon physiology
 Disturbances understood as pathophysiology
To Encourage Thought Not Mechanical
Reaction
Most abnormalities are
relatively simple, and many
iatrogenic
It’s All About Balance
 Gains and Losses
 Losses


Sensible and Insensible
Typical adult, typical day




Skin
Lungs
Kidneys
Feces
600 ml
400 ml
1500 ml
100 ml
 Balance can be dramatically impacted by
illness and medical care
Fluid Compartments
 Total Body Water
 Relatively constant
 Depends upon fat content and varies with age
 Men 60% (neonate 80%, 70 year old 45%)
 Women 50%
TOTAL BODY WATER
60% BODY WEIGHT
ECF
ICF
2/3
H2O
1/3
Predominant solute
Predominant solute
K+
Na+
I LOVE SALT WATER!
Electrolytes
(mEq/L)
Na
K
Ca
Mg
Cl
HCO3
Protein
Plasma
140
4
5
2
103
24
16
Intracellular
12
150
0.0000001
7
3
10
40
Fluid Movement
 Is a continuous process
 Diffusion
 Solutes move from high to low concentration
 Osmosis
 Fluid moves from low to high solute concentration.
 Active Transport
 Solutes kept in high concentration compartment
 Requires ATP
Movement of Water
 Osmotic activity
 Most important factor
 Determined by concentration of solutes
Plasma (mOsm/L)
2 X Na + Glc + BUN
18
2.8
Third Space
 Abnormal shifts of fluid into tissues
 Not readily exchangeable
 Etiologies
 Tissue trauma
 Burns
 Sepsis
Fluid Status




Blood pressure
Check for orthostatic changes
Physical exam
Invasive monitoring




Arterial line
CVP
PA catheter
Foley
Case 1
 6 month old boy, born full-term
 Developed worsening vomiting during the
past week
 Today he is listless, irritable, not tolerating
oral intake
 Pulse 145, BP 70/50
 Diaper is dry, anterior fontanel depressed
Case 1 Labs
149
92
12
2.8
40
0.8
12.3
15
45
200
Case 1 F & E Problem List




Hypovolemia
Hypernatremia
Hypokalemia
Alkalosis
149
92
12
2.8
40
0.8
Volume Deficit
 Most common surgical disorder
 Signs and symptoms
 CNS: sleepiness, apathy,
reflexes, coma
 GI: anorexia, N/V, ileus
 CV: orthostatic hypotension, tachycardia with
peripheral pulses
 Skin: turgor
 Metabolic: temperature
Dehydration
Chronic Volume Depletion
Affects all fluid components
Solutes become concentrated
Increased osmolarity
Hct can increase 6-8 pts for 1 L deficit
Patients at risk:
Cannot respond to thirst stimuli
Diabetes insipidus
Treatment: typically low Na fluids
Hypovolemia
Acute Volume Depletion
Isotonic fluid loss, from extracellular compartment
Determine etiology
Hemorrhage, NG, fistulas, aggressive diuretic
therapy
Third space shifting, burns, crush injuries,
ascites
Replace with blood/isotonic fluid
» Appropriate monitoring
»
Physical Exam
»
»
Foley (u/o > 0.5 ml/kg/min)
Hemodynamic monitoring
Treatment – Patient weight is 12 kg
 Fluid choice?
 Replace volume
 Replace Cl
 How to order
 “Bolus”
 Think about rate over time
 Adequate access important
 What would maintenance fluid choice and rate
be?
 4-2-1 rule
 Why not replace K right away?
Acid – Base Balance
 Acidosis
 May result from decreased perfusion i.e. decreased
intravascular volume
 K will move out of cells
 Alkalosis
 Complex physiologic response to more chronic
volume depletion
 i.e. vomiting, NG suction, pyloric stenosis, diuretics
 K will move intracellular
Paradoxical Aciduria
Hypochloremic
Hypovolemia
Na
Na
H
Cl
K
Loop of Henle
Case 1 When should we operate?
 Need to wait until adequately resuscitated
 Why
 Monitor by:
 Normalized vital signs
 Good urine output
 Normalized labs
Case 2
 64 year old, had colon resection 5 days ago
 “doing well” ….until….
 Suddenly develops atrial fibrillation with rapid
ventricular response
 P 120, irregular; BP 115/70; RR 20
 Temp 38.7
 Confused, anxious
Case 2 Labs
128
100
12
3.0
22
0.8
16.3
10
30
180
Mg 1.1
Case 2

Diagnoses?
 New
onset A fib, why?
 Hypervolemia
 Hyponatremia
 Hypokalemia
 Hypomagnesemia
 Anemia
Case 2

Why does patient have hypervolemia?
Increased Antidiuretic Hormone (ADH)
 Causes





Surgical stress (physiologic)
Cancers (pancreas, oat cell)
CNS (trauma, stroke)
Pulmonary (tumors, asthma, COPD)
Medications
 Anticonvulsants, antineoplastics, antipsychotics,
sedatives (morphine)
Hyponatremia – how to classify
 Na loss
 True loss of Na
 Dilutional (water excess)
 Inadequate Na intake
 Classified by extracellular volume
 Hyovolemic (hyponatremia)
 Diuretics, renal, NG, burns
 Isotonic (hyponatremia)
 Liver failure, heart failure, excessive hypotonic
IVF
 Hypervolemic (hyponatremia)
 Glucocorticoid deficiency, hypothyroidism
Patient was receiving maintenance Fluids
D5 0.45NS + 20 mEq KCl/L at 125 ml/hr
How much Sodium is Enough???
 NS
 0.9% = 9 grams Na per liter
 0.45 NS = 4.5 grams per liter
 125 ml/hour = 3000 ml in 24 hours
 3 liters X 4.5 grams Na = 13.5 GRAMS Na!
 (If 0.2 NS: 3 liters X 2 grams Na = 6 grams
Na)
Case 2 - How to treat
 A fib: ACLS protocol
 Correct electrolytes
 Replace Mg and K
 Decrease volume, fluid restriction
Case 3
 23 year old with jejunostomy
 Had colon and ileum resected due to injury
 Tolerates some oral nutrition, but has high
output from jejunostomy (2.5 liters per day),
therefore requires TPN
 P 118, BP 105/60
Case 3 Labs
154
114
28
3.2
16
2.4
10.3
9.7
28
380
Glucose 213
Mg 1.4
Current Problems
 Hypovolemia
 Increased plasma osmolarity
 2 X 154 + (213/18) + (28/2.8) = 329.8
 Hypernatremia
 Renal insufficiency
 Acidosis
Case 3 - Hypovolemia
 Fistula output
 High volumes can rapidly lead to dehydration
 Electrolyte composition can be difficult to
estimate
 Can send aliquot to laboratory
 May need to be replaced separately from
maintenance (TPN) fluids
 Hyperglycemia
Hypernatremia
Relatively too little H2O
 Free water loss (burns, fever, fistulas)
 Diabetes insipidus (head trauma, surgery,
infections, neoplasm)
 Dilute urine (Opposite of SIADH)
 Osmotic diuresis
 Nephrogenic DI
 Kidney cannot respond to ADH
 Too much Na, usually iatrogenic
Hypernatremia
Free water deficit:
[0.6 X wt (kg)] X [Serum Na/140 - 1]
Example:
Na 154, 60 kg person
(0.6 X 60) X [(154/140) - 1]
36 X [1.1 -1]
36 X 0.1 = 3.6 Liters
Case 3 – How to Treat




154
114
28
3.2
16
2.4
Correct hyperglycemia
Replace pre-existing volume deficits
Reduce ostomy output if possible
What to do with:
 Acidosis?
 Hypokalemia?
Case 4
 58 year old, had a recent kidney transplant
 Laboratory calls with critical value:
 Potassium 5.9
 What to do?
Case 4
 Evaluate the patient
 Exam
 ECG
 Order repeat labs
Hyperkalemia - Common Causes
 Spurious
 Blood drawn above running IV
 Underlying disease
 Renal failure
 Rhabdomyolysis
 Associated medications
 Too much K+, ACE inhibitors, beta-blockers,
antibiotics, chemotherapy, NSAIDS,
spironolactone
 Treatment
 Mild: dietary restriction, assess medications
 Moderate: Kayexalate
 Do not use sorbitol enema in renal failure patients
 Severe: dialysis
Potassium and Ph
 Normally 98% intracellular
 Acidosis
 Extracellular H+ increases, H+ moves
intracellular, forcing K+ extracellular
 Alkalosis
 Intracellular H+ decreases, K+ moves into cells
(to keep intracellular fluid neutral)
Hyperkalemia - Treatment
 Emergency (> 6 mEq/l)




Monitor ECG, VS
Calcium gluconate IV (arrhythmias)
Insulin and glucose IV
Kayexalate, Lasix + IVF, dialysis
 Mild to Moderate
 Mild: dietary restriction, assess medications
 Moderate: Kayexalate
 Do not use sorbitol enema in renal failure patients
 Severe: dialysis
The End
Makani U’i
Remember JVD?