Fluids Flashcards
What is normal urine rate?
0.5 - 1.0ml/kg per hour
How much fluid do adults need per day?
35ml/kg per day or 1500ml/m2 per day
How much fluid do you lose due to fever every day?
250ml/day per degree centrigrade of fever
How do you estimate how much fluid you lose due to operative losses?
hours NPO x baseline maintenace IV fluid requirement + # hours of case x baseline IV fluid requirement + operative blood loss + insensible losses
Estimation of insensible losses:
1-3ml/kg per hour for minor procedure
4-7ml/kg per hour for intermediate procedure
8-12 ml/kg per hour for major procedure
What is pseudohyponatremia?
Low sodium due to:
1. hypertriglyceridemia (lots of fat)
2. hypoerproteinemia (lots of proteins)
What are the causes of isotonic hyponatremia? (4)
- Infusions of isotonic glucose
- Mannitol
- Glycine
- Post-TURP
What are the causes of hypertonic hyponatremia?(5)
- After hypertonic infusions of glucose
- Mannitol
- Glycine
- After TURP
- Hyperglycemia
What are the causes of hypovolemic hyponatremia?(3)
- GI losses (vomiting, diarrhea, fistula)
- Skin losses (thermal injury)
- Renal losses (diuretics, diabetes insipidus, salt wasting nephritis, peritoneal dialysis)
What are the causes of isovolemic hyponatremia? (6)
- Water intoxication
- Iatrogenic causes
- Secretion of ADH
- Hypokalemia
- Drugs (sulfonylureas, carbamazepine, phenothiazines, antidepressants)
- Reset thermostat
What are the causes of hypervolemic hyponatremia? (3)
- CHF
- Liver failure
- Drugs (indomethacin, carbamazepine, vincristine, vinblastine, cyclophosphamide, nicotine derivatives)
What is the formula to estimate sodium deficit?
Na+ deficit = (Desired Na+ level - actual Na +level) x TBW
What type of fluid do you use to correct hypovolemic hyponatremia?
REplace with 0.9% NaCl,
Monitor frequently to avoid too rapid of correction
How do you correct isovolemic hyponatremia?
Corrected by addressing the underlying disorder
What is a major complication of rapid infusion of hypertonic saline solutions?
Central pontine myelinosis
What are the 4 causes of hypervolemic hyponatremia?
- Iatrogenic (excessive administration of Na+) (5)
- Conn syndrome
- Cushing syndrome
- Steroid Use
- Congenital adrenal hyperplasia
What is Conn’s Syndrome?
Also known as primary aldosteronism…
What are the two effects of rapid reversal of hypernatremia?
- Cerebral edema
- Uncal herniation
How do you correct hypernatremia?
- Address the underlying disorder
- Calculate the free water deficit. H20 deficit = (0.6 x kg of body weight) x [(serum Na+/140)-1]
- Replace half the deficit in the first 24 hours and then the remainder in the following 2 days
- USE A HYPOTONIC FLUID such as D5W
At what level do you see the clinical signs of hypokalemia?
2.5 mEq/L
What are the clinical signs of hypokalemia?
- CV - sensitization to digitalis and epi, arrhythmias, electrocardiographic changes (low voltage, flattened T waves, ST segment depression, prolonged Qt interval and prominent U waves)
- CNS - parasthesias, paralysis
- GI - constipation, ileus
- M/S - weakness, cramps, myagias, rhabdomyolysis
What are the causative factors of hypokalemia in a surgical patient?
- GI (diarrhea, gastric drainage via vomiting or NG tube)
- Diuretics
- Insulin administration
How do you treat hypokalemia?
- Ensure adequate renal function before beginning replacements
- Treat the alkalosis
- Decrease Na+ intake
- Enteral replacement is preferred
- If not enteral, parenteral is preferred.
For every decrease of K+ on blood work, how much decrease is there in the total body stores?
For every 1 mEq decrease, there is a 100-200 mEq decrease in total body stores.
How much potassium is there in a banana?
10mEq K+
What is the maximum amount of KCl can you administer through a peripheral IV?
No more than 10mEq/h
What is the maximum amount of KCl can you administer through a central line?
No more than 20 mEq/h but can also be up to 40mEq/h if the patient has cardiac monitoring and is in the intensive care unit.
What are the signs and symptoms of hyperkalemia?
CV- peaked T waves, flattened P waves, QRS prolongation, cardiac arrest, ventricular fibrillation
M/S - weakness and parasthesias
GI - N/V, diarrhea, intestinal colic
What are the causative factors of hyperkalemia?
- Pseudohyperkalemia - can occur in hemolysis, thrombocytosis and leukocytosis
- Acidosis
- Insulin deficiency
- Reperfusion syndrome
- Tissue necrosis (crush injuries)
- Burns
- Electrocution
- Beta blocker therapy
- Digitalis
- Succinylcholine
- Renal insufficiency (most common cause in surgical patient)
- MRA
- Mineral corticoid deficiency
How do you treat mild hyperkalemic? (i.e. <6.0mEq/L)
- Remove the exogenous source
- Add lasix
How do you treat severe hyperkalemia? (>6.0)
Temporazing measures:
(i) Calcium gluconate or calcium chloride—temporary cardiac stabilization
(ii) Inhaled beta-agonists—causes the most rapid intracellular shift in K+
(iii) D50W (50 g) and 10 units intravenously of regular insulin
Therapeutic measures:
(i) Calcium gluconate or calcium chloride—temporary cardiac stabilization
(ii) Inhaled beta-agonists—causes the most rapid intracellular shift in K+
(iii) D50W (50 g - 1 amp) and 10 units intravenously of regular insulin
What are the different types of calcium available in the serum?
- Free ionized Ca2+ (45%) - the only physiologically active form
- Bound to proteins (40%)
- Bound to diffusible compounds (15%)
Which organ controls the metabolism of calcium?
Parathyroid hormone
What are the signs and symptoms of hypocalcemia? (4)
- CV - QT prolongation, ventricular arrhythmia
- M/S - cramping, parasthesias (first perioral/central, then extremities), tetany, increased deep tendon reflexes
- Chvostek sign- facial muscle twitching after percussion over trunk of facial nerve
- Trosseau sign - carpal spasm after inflating blood pressure cuff for more than 3 minutes
What is Chvostek sign?
facial muscle twitching after percussion over trunk of facial nerve
What is the Trousseau sign?
carpal spasm after inflating blood pressure cuff for more than 3 minutes
What are the causes of hypocalcemia?
- Calcium sequestration
Pancreatitis
Rhabdomyolysis
Packed RBC due to citrate chelation - Albumin normal: check PTH level.
Low parathyroid hormone, hypoparathyroidism, magnesium deficiency (because magnesium is required for the production and release of PTH hormone) - High parathyroid hormone indicates
Pancreatitis
Hyperphosphatemia
Renal insufficiency
Fistula
Specific drugs (gentamycin and lasix)
Pseudohypothyroidism
Decreased vitamin D
How do you treat acute hypocalcemia?
IV management in acute hypocalcemia:
- 200-300mg elemental calcium to eliminate attack of tetany
- 1g of calcium gluconate
- One gram of CaCl2
What are the symptoms of hypercalcemia?
Stones, bones, groans, and psychic overtones
(1) CNS—confusion, depression, psychoses, coma (psychic overtones)
(2) GI—nausea, vomiting, anorexia, ileus, constipation, abdominal pains (groans)
(3) Genitourinary—nephrolithiasis, polyuria (stones)
(4) CV—hypertension, shortening of the QT interval
What are causes of hypercalcemia?
- Hyperparathyroidism
- Malignancy
- Milk alkali syndrome
- Hyperthyroidism
- Acromegaly
- Pheochromocytoma
- Vitamin A
- Vitamin D
- Thiazides
- Granulomatous disease
- Adrenal insufficiency
- Page disease of the bone
- Prolonged immobilization
Treatment of mild hypercalcemia?
Mild hypercalcemia (<12 mg/dL) can be treated with restriction of calcium intake and discontinuance of offending or contributing agents.
Treatment of severe hypercalcemia?
Severe hypercalcemia requires prompt treatment.
(a) Intravenous hydration—Most patients are dehydrated; begin with 0.9% NaCl.
(b) Oral or intravenous phosphate inhibits bone resorption.
(c) Diuresis with loop diuretic and aggressive intravenous hydration (>200 mL/h).
(d) Calcitonin is useful in treating hypercalcemia associated with malignancy or primary hyperparathyroidism; usual dose is 4 units/kg subcutaneously or intramuscularly every 12–24 hours.
(e) Pamidronate is useful in malignancy-associated hypercalcemia; usual dose is 60–90 mg.
What are the signs of hypermagnesemia?
(1) CNS—mental status changes, paralysis (Mg2+ > 12 mEq), coma
(2) CV—atrioventricular block, prolonged QT interval, hypotension, sinus bradycardia
(3) GI—nausea, vomiting
(4) M/S—loss of deep tendon reflexes (Mg2+ > 8 mEq)
What are the signs and symptoms of Hypophosphatemia?
(1) CNS—mental status changes, weakness, flaccid paralysis
(2) CV—cardiac arrest
(3) M/S—bone pain
(4) Heme—platelet and granulocyte dysfunction
In what scenario do you use LR over NS for fluid resuscitation?
LR is the preferred fluid in a resuscitation in which the patient is acidotic and does not have hyperkalemia, hyponatremia, hypochloremia, hypercalcemia, or an alkalosis.
How much sodium chloride is there in 0.9% NS?
154mEq/L for both
How much sodium chloride is there in lactated ringers?
Na: 130mEq/L
Cl; 109 mEq/L
What type of solution do you want if you want a hypotonic solution for fluid replacement?
0.45%NS and D5W
What is the osmolarity of normal saline?
286
What is the osmolarity of LR?
272
What is the kcal amount in 0.9%NaCl?
None
What is the kcal amount in D5W?
170 Kcal/L
What is the caloric amount in D10W?
340 kCal/L
What is the caloric amount in D50W?
1700 kCal/L
When do you use hypertonic normal saline?
3% NS Has begun to have limited use as a volume expander in selected patient populations (some patients with head trauma); however, used primarily to correct symptomatic hyponatremia
What do you use for maintenance IV fluid?
Most commonly used is D5 0.45% NS with 20 mEq KCl added; this is simply tailored to meet the daily basal metabolic requirements of an otherwise healthy patient.
What is your differential for metabolic acidosis with increased anion gap?
MUDPILES
Methanol, Uremia, DKA, Paraldehyde, Ingestion, Lactic acidosis, Ethanol, Salicylates
What is your differential for metabolic acidosis with normal anion gap?
Essentially due to hyperchloremia
USEDCRAP
Ureterostomy
Small bowel fistulae
Extra Chloride
Diarrhea
Carbonic anhydrase inhibitors (i.e. acetazolomide)
Adrenal insufficiency
Pancreatic fistula
What is the most common cause of metabolic acidosis in surgical/ trauma patients?
Lactic acidosis due to indadequate volume resuscitation
What is the treatment of lactic acidosis?
- Correct the underlying disorder
- Provide bicarbonate
What is the treatment of metabolic acidosis when the pH is less than 7.2
For a pH less than 7.2–7.3, addition of an ampule or two of bicarbonate may be required; one ampule contains 50 mEq sodium bicarbonate.
For severe acidosis, while addressing the underlying disorder, the addition of bicarbonate can be beneficial to increase the pH to greater than 7.2.
How do you determine the cause of metabolic alkalosis?
- First determine if the treatment may be chloride responsive or unresponsive
What are the causes of metabolic alkalosis?
- Chloride responsive
a. Contraction alkalos
B. diuretic use
C acid loss through vomiting or the nasogastric tub
D. bicarbonate administration
E. jealous adenoma
- Chloride unresponsive
A. Severe hypokalemia.
B. Hyperaldosteronism
C. Mineralocorticoid excess.
renal failure
Chronic Edema
How do you determine whether the cause of metabolic alkalosis is chloride unresponsive versus chloride, responsive?
Urine chloride levels can be measured to help to differentiate among the various causative factors. A urine chloride level less than 15 mEq/dL suggests chloride-responsive causative factors, whereas a urine chloride level greater than 15 mEq/dL indicates chloride-unresponsive causes.
How do you treat metabolic alkalosis?
(1) Begin by addressing underlying causes. Volume expansion and correction of hypokalemia correct most cases. Correction with 0.9% NS facilitates improvement because of its acidity and chloride contents.
(2) In refractory cases, the use of acetazolamide (Diamox 500 mg every 6 hours) will inhibit de novo synthesis and renal reabsorption of bicarbonate.
What causes respiratory acidosis?
Primarily from an increase in partial pressure of carbon dioxide (PaCO2) secondary to inadequate ventilation.
What are the causes of hypoventilation?
- hyperventilation can be caused by respiratory centre depression
- Chronic obstructive pulmonary disease
- Inadequate, mechanical ventilation.
- Poor ventilation secondary to pain.
How do you know there’s respiratory acidosis?
Decreased pH with an increased PaCO 2; in chronic states, will see a compensatory increase in HCO
how do you treat respiratory acidosis?
(1) Address underlying cause of hypoventilation.
(2) Improve minute ventilation—remove airway obstruction, pulmonary toilet, bronchodilators, avoid respiratory depressants, reverse opioid narcotics and continuous positive airway pressure/bilevel positive airway pressure
(3) Endotracheal intubation and mechanical ventilation if noninvasive measures fail; if intubated, increase minute ventilation (frequency and tidal volume).
(4) In chronic hypercapnia, particularly related to chronic obstructive pulmonary disease, hypoxemia becomes the agent driving the respiratory system; therefore the patient’s hypoxemia should not be fully corrected and the hypercapnia should be slowly corrected.
How do you improve minute ventilation? (7)
Remove every obstruction.
Pulmonary toilet.
Bronchodilators.
Avoid respiratory depressants.
Reverse opioid narcotics.
CPAP.
BiPAP.
What does pulmonary toilet mean
Pulmonary hygiene, previously known as pulmonary toilet, refers to exercises and procedures that help to clear your airways of mucus and other secretions. This ensures that your lungs get enough oxygen and your respiratory system works efficiently.
What is the main driver of respiratory acidosis and patients with chronic hypercapnia?
In chronic hypercapnia, particularly related to chronic obstructive pulmonary disease, hypoxemia becomes the agent driving the respiratory system; therefore the patient’s hypoxemia should not be fully corrected and the hypercapnia should be slowly corrected.
What is the main cause of respiratory alkalosis?
Results primarily from a decrease in PaCO 2 secondary to hyperventilation
how do you diagnose respiratory alkalosis?
Increased pH with a decreased PaCO 2
how do you treat respiratory alkalosis?
(1) Address underlying disorder.
(2) Correct hypoxemia if present.
(3) If acutely symptomatic and not intubated, use a rebreathing device.
(4) In ventilated patients, decrease minute ventilation while maintaining PaCO 2 no less than 30 mm Hg.
