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FLUIDS AND
ELECTROLYTES FOR
SURGEONS
Anil S. Paramesh MD, FACS
Associate Professor of Surgery, Urology and Pediatrics
Why ?
 Essential for surgeons (and all physicians)
 Knowledge can diagnose, treat and prevent
many of the problems in surgical patients
Most abnormalities are
relatively simple, and many
iatrogenic
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
ICF
2/3 (40% BW)
H2O
ECF
1/3
(20% BW)
Predominant solute
Predominant solute
K+
Na+
75% interstitial
25% intravascular
(5% of BW)
It’s All About Balance
 Gains and Losses
 Most individuals ingest approx 2 – 2.5 L/day
 Losses


Sensible and Insensible
Typical adult, typical day
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
Skin
Lungs
Kidneys
Feces
600 ml
400 ml
1500 ml
100 ml
 Balance can be dramatically impacted by
illness and medical care
How much fluid can a patient lose if a patient
could lose fluid?
 Sensible losses
 Blood (most pts can tolerate 500 cc BL)
 Sweat (up to 4 L /day)
 Tears – (diarrhea)
 Insensible losses


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Skin 250 cc/day/degree fever
Trach/vent – upto 1500 cc/day
Peritoneum - > 1/day
Third spacing
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
 Gibbs-Donnan equation – product of diffusible an/cations
same on both sides of SP membrane
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
 Normal around 300 mOsm/L
 Osmolality determined by concentration of
solutes
Plasma (mOsm/L)
2 X Na + Glc + BUN
18
2.8
Fluid Status




Blood pressure
Check for orthostatic changes
Physical exam
Invasive monitoring




Arterial line
CVP
PA catheter
Foley
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
Hypovolemia
Acute Volume Depletion
Determine etiology
Hemorrhage,
NG, fistulas,
Aggressive diuretic therapy
Third space shifting, burns, crush injuries
Ascites
What kind of fluid are we losing?
 Sweat – hypotonic (low sodium)
 Insensible loss is pure water
 GI loss is usually isotonic
 Stomach – acid, high CL
 Pancreas/bile – high HCO3
 Saliva – high K
IV fluids a la carte
 NaCl
 Normal saline (0.9%) has 154 mEq/L Na, 154
mEq Cl
 ½ Normal has 77 mEq Na/Cl
 Lactated Ringers
 Has 130 Na, 109 Cl (also has some K, Ca,
lactate)
 D5Water
 Good replacement for insensible losses
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
134
92
12
2.8
40
0.8
12.3
15
45
200
Case 1 F & E Problem List


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
Hypovolemia
Hypochloremia
Hypokalemia
Alkalosis
134
92
12
2.8
40
0.8
Treatment – Patient weight is 12 kg
 Fluid choice?
 Replace volume
 Replace K/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
Acid – Base Balance
 Acidosis
 May result from decreased perfusion i.e. decreased
intravascular volume
 K will move out of cells (K+ - H+ exchange)
 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
Aldosterone
activation
Na
H
Na
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, 50 kg, 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
8.9
28
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
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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
 Hypovolemic (hyponatremia)
 Diuretics, renal, NG, burns
 Isovolemic (hyponatremia)
 Liver failure, heart failure, excessive hypotonic
IVF
 Hypervolemic (hyponatremia)
 Glucocorticoid deficiency, hypothyroidism
Patient was receiving maintenance fluids
D5 0.45NS at 125 ml/hr
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) + (28/1.8) = 335
 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
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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
 Hemolyzed specimen
 Underlying disease
 Renal failure
 Rhabdomyolysis
 Associated medications
 Too much K+, ACE inhibitors, beta-blockers,
antibiotics, chemotherapy, NSAIDS,
spironolactone
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)
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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
 Severe: dialysis
Pimping Questions on Rounds!

Signs of hypo Ca?

Chvostek, Trousseau,
prolonged QT

MCC of Hyper Ca?
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PTH/metastatic Ca
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Signs of hyper Mg
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Loss of DTR
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Signs of hypo Phos?
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Difficulty weaning off vent
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Compl of correcting Na too
rapidly?

Central Pontine Myelinolysis