Transcript Fluid and Electrolyte Management of the Surgical Patient

Basic Science Lecture
9/28/10
Marcie Dorlon
Introduction
 Changes in fluid volume and electrolyte
composition occur: preoperatively,
intraoperatively, postoperatively, and in trauma
and sepsis
 Important to recognize and understand how to
manage changes
 http://www.youtube.com/watch?v=-Vw2CrY9Igs
Total Body Water
 Water constitutes 50-60% total body weight
 Primarily a reflection of body fat (lean muscle=more water)
 Estimated total body water should be downward by 10-20%
for obese individuals and downward 10% for malnourished
individuals
 Total body water is estimated around 80% for newborns
Fluid Compartments
Composition Fluid Compartment
Osmotic Pressure
 Facilitates water movement across cell membranes
 Determined by concentration of solutes on either side
membrane (mainly sodium, glucose and urea/BUN)
 Calculated serum osmolality=
2 * sodium + (glucose/18) + (BUN/2.8)
 Osmolality is maintained between 290 and 310
Normal Exchange of Fluid and
Electrolytes
 Healthy person comsumes average of 2000mL water/day
 Daily losses average 800-1200mL urine, 250mL stool,
600mL insensible (skin, lungs)
 To clear products of metabolism, kidneys must excrete 500
to 800mL urine per day despite intake
 Average salt intake is 3-5grams/day
Signs and Symptoms of Volume Disturbances
System
Generalized
Cardiac
Renal
GI
Pulmonary
Volume Deficit
Weight loss
Decreased skin turgor
Tachycardia
Volume Excess
Weight gain
Peripheral edema
Increased cardiac output
Orthostasis/hypotension Increased central
venous pressure
Collapsed neck veins
Distended neck veins
Murmur
Oliguria
—
Azotemia
Ileus
Bowel edema
—
Pulmonary edema
Composition of GI secretions
Type of
Secretion
Volume
Na
(mL/24 h) (mEq/L)
K (mEq/L) Cl
(mEq/L)
HCO3–
(mEq/L)
Stomach
1000–2000 60–90
10–30
100–130
0
Small
intestine
2000–3000 120–140
5–10
90–120
30–40
Colon
—
60
30
40
0
Pancreas
600–800
135–145
5–10
70–90
95–115
Bile
300–800
135–145
5–10
90–110
30–40
Body System
Hyponatremia
Central nervous system
Headache, confusion, hyperactive or hypoactive deep tendon
reflexes, seizures, coma, increased intracranial pressure
Musculoskeletal
Weakness, fatigue, muscle cramps/twitching
GI
Anorexia, nausea, vomiting, watery diarrhea
Cardiovascular
Hypertension and bradycardia if significant increases in
intracranial pressure
Tissue
Lacrimation, salivation
Renal
Oliguria
Body System
Hypernatremia
Central nervous system
Restlessness, lethargy, ataxia, irritability, tonic spasms,
delirium, seizures, coma
Musculoskeletal
Weakness
Cardiovascular
Tachycardia, hypotension, syncope
Tissue
Dry sticky mucous membranes, red swollen tongue, decreased
saliva and tears
Renal
Oliguria
Metabolic
Fever
Hyperkalemia Causes
 Increased intake:
 Potassium supplementation
 Blood transfusions
 Endogenous load/destruction:
 Hemolysis or rhabdomyolysis
 Crush injury
 Gastrointestinal hemorrhage
 Increased release:
 Acidosis
 Rapid rise of extracellular osmolality (hyperglycemia or mannitol)
 Impaired excretion:
 Potassium-sparing diuretics
 Renal insufficiency/failure
Hyperkalemia Symptoms
 GI
 Nausea
 Vomiting
 Intestinal colic
 Diarrhea
 Neuromuscular:
 Weakness
 Ascending paralysis
 Respiratory failure
 Cardiovascular:
 EKG changes:


Early peaked T waves
Late widened QRS, flat p-waves, prolonged PR interval, v-fib
 Cardiac arrest
Hypokalemia Causes
 Inadequate intake:
 Dietary
 Potassium-free intravenous fluids
 Potassium-deficient TPN
 Excessive potassium excretion:
 Hyperaldosteronism
 Medications
 GI losses:
 Direct loss of potassium from GI fluid (diarrhea)
 Renal loss of potassium (gastric fluid, either as vomiting or high
nasogastric output)
Hypokalemia Symptoms
 GI
 Ileus
 Constipation
 Neuromuscular
 Weakness
 Fatigue
 Diminished tendon reflexes
 Paralysis
 Cardiovascular
 EKG changes

U waves, T wave flattening, ST segment changes, arrhythmias
 Cardiac arrest
Calcium
•
•
•
Daily Intake 1-3grams
Adjust total serum calcium down by 0.8g/dL for every 1g/dL decrease in albumin
Acidosis increases ionized fraction of calcium due to decreased protein binding
•
Hypercalcemia
•
•
Think primary hyperparathyroidism in outpatient setting vs malignancy in inpatient
setting
•
Sx: neurologic impairment, musculoskeletal weakness and pain, renal dysfunction,
nausea, vomitting, abdominal pain, hypertension, arrhythmias, worsening digitalis
toxicity
•
EKG changes: shortened QT interval, prolonged PR and QRS interval, increased
QRS voltage, T wave flattening and widening, AV block->arrest
Hypocalcemia
•
Causes: pancreatitis, massive soft tissue infections, renal failure, pancreatic or small
bowel fistulas, hypoparathyroidism, TSS, tumor lysis syndrome, abnormal
magnesium levels, massive blood transfusion with citrate binding
•
Sx: paresthesias face and extremities, muscle cramps, stridor, tetany, seizures,
hyperreflexia, Trousseau’s sign, Chvostek’s sign, decreased cardiac contractility,
heart failure
•
EKG changes: prolonged QT interval, T wave inversion, heart block, V-fib
Phosphorus
 Abundant in metabolically active cells and tightly controlled by
renal excretion
 Hyperphosphatemia
 Causes: decreased urinary excretion, increased intake,
hypoparathyroidism, hyperthyroidism, rhabdomyolysis, tumor lysis
syndrome, hemolysis, sepsis, hypothermia, malignant hyperthermia
 Sx: Most asymptomatic but severe cases can lead to metastatic
deposition of calcium-phosphorus complexes
 Hypophosphatemia
 Causes: decreased intake, intracellular shift (respiratory alkalosis,
insulin administration, hungry bone syndrome, refeeding syndrome)
increased excretion, decreased GI uptake due to binders,
 Sx: Usually asymptomatic until severe- cardiac dysfunction and
muscle weakness when high energy phosphates unavailable
Magnesium
 Hypermagnesemia
 Causes: severe renal insufficiency, iatrogenic- in antacids, laxatives
and TPN, severe trauma, severe acidosis, thermal injury
 Sx: nausea, vomiting, weakness, lethargy, hyporeflexia,
hypotension and cardiac arrest
 EKG changes: increased PR interval, widened QRS complex,
elevated T waves
 Hypomagnesemia
 Causes: starvation, alcoholism, prolonged IVF tx, inadequate TPN,
diuretic use, amphotericin B, primary aldosterism, diarrhea,
malabsorption, acute pancreatitis
 Sx: neuromuscular and CNS hyperactivity, similar to hypocalcemia
 EKG changes:prolonged QT and PR intervals, ST segment
depression, flattening or inversion of p waves, torsades de pointes,
arrythmias
Acid-Base Disorders
Acute Uncompensted
Type of
Acid-Base
Disorder
pH
Chronic (Partially Compensated)
PCO2
Plasma
pH
(Respiratory HCO3–a
Component) (Metabolic
Component)
Respiratory
acidosis
N
Respiratory
alkalosis
N
Metabolic
acidosis
N
Metabolic
alkalosis
N
PCO2
Plasma
(Respiratory HCO3–a
Component) (Metabolic
Component)
?
IVF Composition
Na
CL
K
HCO3–
Ca
Mg
mOsm
Extracellular fluid 142
103
4
27
5
3
280–310
Lactated Ringer's
130
109
4
28
3
0.9% Sodium
chloride
154
154
308
77
407
Solution
D5 0.45% Sodium 77
chloride
D5W
3% Sodium
chloride
273
253
513
513
1026
Alternative Resuscitative Fluids
Solution
Molecular Weight
Osmolality (mOsm/L) Sodium (mEq/L)
Hypertonic saline
(7.5%)
—
2565
1283
Albumin 5%
70,000
300
130–160
Albumin 25%
70,000
1500
130–160
Dextran 40
40,000
308
154
Dextran 70
70,000
308
154
Hetastarch
450,000
310
154
Hextend
670,000
307
143
Gelofusine
30,000
NA
154
Correcting Hypernatremia
 Treat the associated water deficit
 Water deficit (L)= serum sodium-140 x TBW
140
 Estimate TBW as 50% lean body mass men and 40%
women
 Correct no more than 1 mEq/hr or 12 mEq/day to avoid
cerebral edema and brain herniation
Correcting Hyponatremia
 Free water restriction and occasionally administration of
sodium
 Correct by no more that 0.5mEq/L/hr or maximum increase
of 12 mEq/L/day to avoid central pontine myelinolysis
Correcting Hyperkalemia
 Potassium removal
 Kayexalate


Oral administration is 15–30 g in 50–100 mL of 20% sorbitol
Rectal administration is 50 g in 200 mL of 20% sorbitol
 Dialysis
 Shift potassium
 Glucose 1 ampule of D50 and
 regular insulin 5–10 units IV
 Bicarbonate 1 ampule IV
 Counteract cardiac effects
 Calcium gluconate 5–10 mL of 10% solution
Correcting Hypokalemia
 Serum potassium level <4.0 mEq/L:
 Asymptomatic, tolerating enteral nutrition: KCl 40 mEq
per enteral access x 1 dose
 Asymptomatic, not tolerating enteral nutrition: KCl 20
mEq IV q2h x 2 doses
 Symptomatic: KCl 20 mEq IV q1h x 4 doses
 Recheck potassium level 2 h after end of infusion; if <3.5
mEq/L and asymptomatic, replace as per above protocol
Correcting Hypomagnesemia
 Magnesium level 1.0–1.8 mEq/L:
 Magnesium sulfate 0.5 mEq/kg in normal saline 250 mL infused IV
over 24 h x 3 d
 Recheck magnesium level in 3 d
 Magnesium level <1.0 mEq/L:
 Magnesium sulfate 1 mEq/kg in normal saline 250 mL infused IV
over 24 h x 1 d, then 0.5 mEq/kg in normal saline 250 mL infused
IV over 24 h x 2 d
 Recheck magnesium level in 3 d
 If patient has gastric access and needs a bowel regimen:
 Milk of magnesia 15 mL (approximately 49 mEq magnesium) q24h
per gastric tube
 hold for diarrhea
Correcting Hypocalcemia
 Normalized calcium level <4.0 mg/dL:
 With gastric access and tolerating enteral nutrition:
Calcium carbonate suspension 1250 mg/5 mL q6h per
gastric access;
 Recheck ionized calcium level in 3 d
 Without gastric access or not tolerating enteral nutrition:
 Calcium gluconate 2 g IV over 1 h x 1 dose;
 Recheck ionized calcium level in 3 d
Correcting Hypophosphatemia
 Tolerating enteral nutrition:
 Neutra-Phos 2 packets q6h per gastric tube or feeding tube
 No enteral nutrition:
 KPHO4 or NaPO4 0.15 mmol/kg IV over 6 h x 1 dose
 Recheck phosphate level in 3 d
 Phosphate level <1.0 mg/dL:
 Tolerating enteral nutrition:
 KPHO4 or NaPO4 0.25 mmol/kg over 6 h x 1 dose
 Recheck phosphate level 4 h after end of infusion;
 If <2.5 mg/dL, begin Neutra-Phos 2 packets q6h
 Not tolerating enteral nutrition:
 KPHO4 or NaPO4 0.25 mmol/kg (LBW) over 6 h x 1 dose;
 recheck phosphate level 4 h after end of infusion;
 If <2.5 mg/dL, then KPHO4 or NaPO4 0.15 mmol/kg (LBW) IV over 6 h x 1
dose
Preoperative Fluid Therapy
For the first 0 to 10 kg
For the next 10 to 20 kg
For weight >20 kg
Give 100 mL/kg per day
Give an additional 50 mL/kg per day
Give an additional 20 mL/kg per day
Just an initial guideline, does not replace pre-existing
deficit or ongoing losses
No routine fluid choice. Surgeon/Anesthesia preference
Intraoperative Fluid Therapy
Usually at discretion of Anesthesia team
Be sure to note what (colloid vs crystalloid) and how much is
given, particular blood or blood products and pressors
Postoperative Fluid Therapy
Take into account NPO status, ongoing losses from NGT,
drains, fistua, etc
Type of fluid can be surgeon or service dependent
Special Circumstances
 Neurologic Patients
 SIADH- hyponatremic with elevated urine sodium & osmolality

Tx with fluid restriction and diuretics & underlying problem
 Diabetes Insipidus-hypernatremia with dilute urine


Central (ADH secretion) vs nephrogenic (ADH responsiveness)
Vasopressin tx
 Cerebral Salt wasting

Dx of exclusion
 Refeeding Syndrome
 Insulin release leads to cellular uptake of electrolytes (Phosphate,
Magnesium, Calcium, Potassium)
 Start feeding slowly at 20kcal/kg/day
 Acute Renal Failure
 Cancer Patients