Download FLUIDS AND ELECTROLYTES FOR SURGEONS

FLUIDS AND
ELECTROLYTES FOR
SURGEONS
Anil S. Paramesh MD, FACS
Associate Professor of Surgery and Urology
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%
ICF
2/3 (40% BW)
Predominant solute
K+
ECF
1/3
(20% BW)
Predominant solute
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
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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
  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
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