Transcript Fluid and Electrolyte Management of the Surgical Patient

Fluid and Electrolyte
Management of the
Surgical Patient
Basic Science
9/08/09
J. P. Stokes
Case Presentation #1
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28 y/o WM involved in MVC brought to 1W with
GCS of 3 and hypotensive. Pt intubated and
receives 2L of LR which stabilize HR and BP.
Found to have extensive cerebral contusion and
SAH. Admitted to ICU with plan by
Neurosurgery to correct any coagulopathy and
keep sodium >150. Placed on 3% Hypertonic
saline with Q6 Na. After 6 hours in the ICU, the
patients UOP increases to 500-1000cc/hr. The
next sodium is 168. 3% discontinued and
patient started on Vasopressin replacement and
free water. Pt deteroriates and herniates due to
cerebral edema.
Case Presentation #2
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55 y/o WF with low rectal cancer s/p neoadjuvant
undergoes LAR with diverting ileostomy. Blood loss is
300cc, fluid for the case was 1.8L crytalloid, and the
case lasted 3.5 hours. Post-operative the patient is
hypotensive with minimal UOP. Patient receives several
1L boluses and BP and UOP improve. She continues to
receive IVFs and her sodium on POD#3 is 128 and her
sats are decreased. She is diuresed and improves. On
POD #5, she is tolerating liquids and her ileostomy
output is 2.8L for that 24 hour period. Her IVFs were
discontinued due to her oral intake and the next morning
her creatinine is 2.3. She is bolused, restarted on
maintenance, and ileostomy replacement, along with
anti-motility agents. Her creatinine improves and she is
discharged on POD #7 with ileostomy output of 1L/day.
Overview
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Total Body Water (TBW) – 50-60% of total
body weight depending on gender
(amount of adipose tissue)
TBW is divided into extracellular (1/3) and
intracellular (2/3) compartments
Extracellular is divided into plasma (1/4)
and interstitial fluid (3/4) – 5% and 15%
of body weight, respectively
Questions
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What is the amount in milliliters of the
intracellular volume in a 70kg male?
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14,000
10,500
42,000
28,000
ml
ml
ml
ml
Composition
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Extracellular – Sodium (+), Chloride (-)
and Bicarbonate (-)
Intracellular- Potassium, Magnesium (+),
Phosphate and Proteins (-)
Plasma – 154 mEq/L of cations/anions
Maintained by ATP-driven sodiumpotassium pumps
Osmotic pressure
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The movement of water across a cell
membrane depends primarily upon
osmosis. This depends on solutes or
osmotically-active particles.
Calculated serum osmolality = 2 X Sodium
+ glucose/18 + BUN/2.8
Normal 280-300 mOsm
Charge determines equivalents (1 mEq of
sodium equals 1 mmol)
Questions
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What is the calculated serum osmolality of a
patient with a the following chemistry?
Na 140, K 4, Cl 105, HCO3 25, BUN 28, Cr 1.0,
Glc 180
260
280
300
320
Bonus: What is the anion gap of this patient?
Fluid Homeostasis
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Average person
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Intake - 2L of water per day (75% oral, 25% from
solids
Output – 1L of urine, 250ml of stool, 600ml of
insensible loss (skin and lungs – pure water)
Insensible losses increased by fever,
hypermetabolism, and hyperventilation
Sweating is an active process and is electrolytes
and water
Average salt intake – 3-5 grams
Fluid Balance
System
Volume down
Volume UP
GeneralizedWeight loss
Weight gain
Dec. skin turgor
Perp. Edema
Cardiac
Tachycardia
Orthostasis
Hypotension
Collasped veins
Increased CO
Increased CVP
Bulging veins
Murmur (flow
GI secretions
Type
Stomach
Intestine
Colon
Pancreas
Bile
Volume
Na
1000–2000
2000–3000
60–90
10–30
120–140 5–10
60
30
135–145 5–10
135–145 5–10
600–800
300–800
K
Cl
100–130
90–120
40
70–90
90–110
HCO3–
0
30-40
0
95–115
30–40
Question
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What fluid do you replace NGT output
with?
D51/2NS
LR
1/2NS with 20 mEq KCL
D5W with 150 mEq NaHCO3
Electrolyte Abnormalities
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Sodium
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Hyponatremia
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Hypernatremia
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Hypervolemic – Excess oral water intake, IV fluids
Euvolemic – Hyperglycemia, SIADH, Hyperlipidemia (pseudo)
Hypovolemic – Decreased sodium intake or increased loss of
sodium containing fluids, GI losses, renal losses (UrNa >20)
Hypervolemic – Salt intake, Mineralcorticoid excess
Euvolemic – Renal water loss (diuretics, DI), Nonrenal water
loss (skin, GI)
Hypovolemic – Adrenal failure, Osmotic diuretics
Signs and Symptoms: CNS, MSK, GI, CV, etc.
Potassium
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Dietary intake 50-100 mEq/day; primarily
intracellular
Hyperkalemia – Excess intake, increased
release from cells, impaired excretion,
medications
Hypokalemia – Decreased intake, Excess
excretion, GI losses (direct vs. indirect)
S/S: GI, CNS, CV
Magnesium
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Hypomagnesemia – Poor intake, increased
renal excretion, GI losses (diarrhea)
Hypermagnesemia – impaired renal
function, excess intake (TPN)
Magnesium plays an important role in
potassium and calcium homeostasis
Calcium/Phosphorus
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Hypercalcemia – Primary
hyperparathyroidism, malignancy
Hypocalcemia – Pancreatitis, renal failure,
hypopara-, etc.
Asymptomaic hypocalcemia can be due to
hypoproteinemia, mainly albumin
Correction for albumin
Phosphorus – renal, gastrointestinal
Acid/Base
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Normal pH – 7.35-7.45
Metabolic vs. Respiratory
Uncompensated vs. Compensated
pH, CO2, HCO3
Anion Gap and Metabolic Acidosis
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Anion gap = (Na + K) – (Cl + HCO3)
Normal: 12 +/- 4
Non-gap acidosis: Hyperalimentation,
Acetozolamide, RTA, Diarrhea, Ureteral
diversion, pancreatic fistulas
Anion gap acidosis – Methanol, Uremia,
DKA, Paraldehyde, INH, Lactate, Ethylene
glycol, Salicylate
Metabolic Alkalosis
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Normal acid-base homeostasis prevents
metabolic alkalosis from developing unless
both an increase in HC03 generation and
impaired renal excretion of HCO3 occurs.
Generally associated with hypokalemia
(pyloric stenosis)
Etiology: Mineralocorticoid excess, loss
from gastric secretions, exogenous,
impaired exretion
Question
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What is the electrolyte and acid/base
disturbance in pyloric stenosis, and explain
why the patient has paradoxical aciduria?
Respiratory derangements
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Hyperventilation
Hypoventilation
Involves minute ventilation (respiratory
rate and tidal volume)
Treatment directed at the cause
Fluid therapy
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What are the concentrations of normal
saline and lactated ringer’s?
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Na 154 and 130
K 0 and 4
Cl 154 and 109
HCO3 0 and 28
Ca 0 and 3
Question
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What is the amount of dextrose per liter in
D51/2NS? How many calories is in one
liter? How many calories per hour if fluids
run @ 125 cc/hr?
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5grams
50grams
500grams
500mg
Treating Electrolyte Disturbances
Hypernatremia – Correction of free water deficit
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Water deficit (L) =[(Na-140)/140] x TBW
TBW at 50% in men and 40% in women
The rate of fluid administered should be titrated to
achieve a decrease in serum sodium of no more than
12 mEq/d.
Rapid correction: cerebral edema, herniation
Hyponatremia – Free water restriction, sodium
administration
Neurologic symptoms – 3% (No more than 1
mEq/L/hr); Complication: CPM
Potassium Correction
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Hyperkalemia: Reduce total body
potassium, shift from extra- to
intracellular, and protect cells from effects
of increased potassium
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What can kill my patient? EKG, calcium
How do I shift potassium? Bicarbonate,
Glucose (Insulin), Albuterol
How can I remove potassium? Lasix, Dialysis,
Potassium binders (Kayexalate)
Repleting Electrolytes
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Potassium: IV and PO/NG
Magnesium: IV (Important for repleting
other electrolytes)
Calcium: IV and PO
Phosphorus: IV and PO (ineffective)
Treatment of ….
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Hypermagnesemia: Remove source,
calcium for cardiovascular effects, dialysis
Hypercalcemia: Volume and diuresis,
bisphosphonates, calcitonin
Hyperphosphotemia: Phosphate binders,
urinary exrection, dialysis
Maintenance fluids/Post-op
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Maintenance
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Boluses
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4, 2, 1 rule (Dextrose, Electrolytes)
5, 2, 1 rule in pediatric surgery
What fluid?
Post-Op
Question
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What is the appropriate fluid and
maintenance rate for a 4kg baby with
pyloric stenosis? What would you use to
bolus the baby and why?
Special Situations
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SIADH – Euvolemia and hyponatremia along
with elevated urine sodium and urine osmolality;
Tx: Free water restriction, diuresis, fluids (?),
lithium, democycline
DI – Dilute Urine in the face of hypernatremia;
Central and Nephrogenic; Tx: Free water,
Vasopressin
Refeeding: Shift from fat to carbohydrate
stimulates insulin release and uptake of
electrolytes (PO4, Mg, K, Ca), hyperglycemia