Chapter 17: Fluids and Electrolytes- Third Spacing Flashcards
What is it?
Fluid accumulation in the interstitium of tissues, as in edema (think of the intravascular and intracellular spaces as the first two spaces)
When does “third-spacing” occur postoperatively?
Third-spaced fluid tends to _mobilize back into the intravascul_ar space aroundPOD #3
What are the classic signs of third spacing?
Tachycardia and Decreased urine output
What is the treatment?
IV hydration with isotonic fluids
What are the surgical causes of:
Metabolic acidosis
Loss of bicarbonate:
- diarrhea
- ileus
- fistula
- high-output ileostomy
- carbonicanhydrase inhibitors
Increase in acids:
- lactic acidosis (ischemia)
- ketoacidosis
- renal failure
- necrotic tissue
What are the surgical causes of:
Hypochloremic alkalosis
- NGT suction
- loss of gastric HCl through vomiting/NGT
What are the surgical causes of:
Metabolic alkalosis
- Vomiting
- NG suction
- diuretics
- alkali ingestion
- mineralocorticoid excess
What are the surgical causes of:
Respiratory acidosis
- Hypoventilation (e.g., CNS depression)
- drugs (e.g., morphine)
- PTX
- pleural effusion
- parenchymal lung disease
- acute airway obstruction
What are the surgical causes of:
Respiratory alkalosis
Hyperventilation (e.g., anxiety, pain, fever, wrong ventilator settings)
What is the “classic” acid–base finding with significant vomiting or NGT suctioning?
Hypokalemic and hypochloremic metabolic alkalosis
Why hypokalemia with NGT suctioning?
Loss in gastric fluid—loss of HCl causes alkalosis, driving K+ into cells
What is the treatment for hypokalemic and hypochloremic metabolic alkalosis?
IVF, Cl−/K+ replacement (e.g., NS with KCl)
What is paradoxic alkalotic aciduria?
Seen in severe hypokalemic, hypovolemic, and hypochloremic metabolic alkalosis with paradoxic metabolic alkalosis of serum and acidic urine
How does paradoxic alkalotic aciduria occur?
H+ is lost in the urine in exchange for Na+ in an attempt to restore volume
With paradoxic alkalotic aciduria, why is H+preferentially lost?
H+ is exchanged preferentially into the urine instead of K+ because of the low concentration of K
What can be followed to assess fluid status?
- Urine output
- base deficit
- lactic acid
- vital signs
- weight changes
- skin turgor
- jugular venous distention (JVD)
- mucosal membranes
- rales (crackles)
- central venous pressure
- PCWP
- chest x-ray findings
With hypovolemia, what changes occur in vital signs?
- Tachycardia
- tachypnea
- initial rise in diastolic blood pressure because of clamping down (peripheral vasoconstriction)
- with subsequent decrease in both systolic and diastolic blood pressures
- pulse pressure variability during inspiration on positive pressure ventilation
How can the estimated levels of daily secretions from bile, gastric,and small-bowel sources be remembered?
Alphabetically and numerically: BGS and 123 or B1, G2, S3, because Bile,Gastric, and Small bowel produce roughly 1 L, 2 L, and 3 L, respectively!
57-year-old man develops confusion and wide swings in heart rate and systolic blood pressure POD #2 after an appendectomy for a perforated appendix; sats = 99%, HCT stable, electrolytes normal, chest x-ray normal
Alcohol withdrawal
34-year-old in the ICU s/p laparotomy with fascia closed, decreased urine output, increased peak airway pressure,decreased CVP, normal chest x-ray, normal EKG
Abdominal compartment syndrome
A 77-year-old man s/p laparoscopic cholecystomy returns to theclinic with a palpable lower abdominal mass, confusion, and weak urine stream
Urinary retention
74-year-old female s/p ex lap now POD #4 with acute onset ofshortness of breath; ABG reveals hypoxia and hypocapnia:
how do you diagnose
Chest CTA to rule out pulmonary embolism
