Postoperative Complications Flashcards
Why is tympani under the costal margin common after laparoscopic surgery?
It results from CO₂ insufflation into the abdominal cavity during laparoscopy and is a benign finding that resolves without intervention.
What is the most common cause of immediate postoperative fever?
Malignant hyperthermia.
What is the underlying genetic mutation in malignant hyperthermia?
Ryanodine receptor (RYR1) gene mutation; autosomal dominant inheritance.
What are the key clinical features of malignant hyperthermia?
Acute muscle rigidity, hypercapnia (elevated CO2), tachycardia, hyperthermia, and rhabdomyolysis.
How is malignant hyperthermia treated?
100% oxygen and dantrolene.
What is the most common cause of early postoperative fever (within 1-3 days)?
Nosocomial infections such as pneumonia or catheter-related infections (CLABSI).
What is the most common bacterial cause of catheter-related bloodstream infections (CLABSI)?
Staphylococcus aureus and coagulase-negative staphylococci.
What is the diagnostic approach for nosocomial pneumonia in postoperative patients?
Urinalysis, chest X-ray, and checking catheter sites for infection.
What are the most common causes of late postoperative fever (>3 days)?
Surgical site infections, intra-abdominal abscess, deep venous thrombosis (DVT), and Clostridium difficile colitis.
A 65-year-old man presents to the emergency department for evaluation of worsening abdominal pain. Five days ago the patient underwent open partial colectomy with anastomosis to treat colonic adenocarcinoma. The patient has a history of hypertension, diabetes mellitus, and ulcerative colitis. At home, the patient has been experiencing nausea, vomiting, and subjective fevers. The patient is passing gas and had a bowel movement yesterday. Temperature is 38.9 °C (102.0 °F), pulse is 126/min, blood pressure is 95/65 mmHg, respirations are 18/min, and SpO2 is 96% on room air. On physical examination, the patient appears uncomfortable. The abdomen is distended and rigid with rebound, tenderness, and guarding. General surgery is consulted and laboratory studies are obtained and pending. CT of the abdomen and pelvis with IV and oral contrast is performed. What is most likely to be seen on abdominal imaging?
This patient presents for evaluation of postoperative abdominal pain. He has evidence of peritonitis and an acute abdomen, and given the recent surgical history, this is most likely due to an anastomotic leak. This complication will appear on CT imaging as free intraabdominal air and fluid, and extravasation of contrast around the site of the anastomosis. CT and ultrasound imaging can help differentiate between the many causes of postoperative abdominal pain. Superficial causes of postoperative abdominal pain include fascial dehiscence which will be seen on CT or ultrasound as separation of the fascial layers. Seromas or hematomas will be readily identifiable on ultrasonography, as will superficial surgical site infections. Patients may also present with deep organ space complications of abdominal surgery for which CT imaging is required. Patients with bowel obstruction will have a transition point with proximal distended bowel loops and collapsed distal bowel on CT imaging. Patients with a phlegmon or abscess will have an intraabdominal fluid collection near the operative site on CT imaging. Patients who have had laparoscopic surgery and have increasing air seen under the diaphragm with serial imaging, likely have pneumoperitoneum.
Which organisms are most commonly associated with early surgical site infections?
Group A Streptococcus and Clostridium perfringens.
Which organisms are most commonly associated with late surgical site infections?
Staphylococcus aureus and other gram-negative bacteria.
What is the best initial diagnostic test for suspected postoperative deep vein thrombosis (DVT)?
Doppler ultrasound of the lower extremities.
What is the difference between dehiscence and evisceration of a surgical wound?
Dehiscence: disruption of sutures without organ protrusion. Evisceration: complete opening with organ protrusion.
What is the first-line treatment for evisceration?
Emergency surgery.
What is a fistula and what conditions increase its risk postoperatively?
An abnormal connection between two organs, commonly seen in Crohn’s disease, radiation, and infections.
What is Ogilvie’s syndrome, and how is it diagnosed?
Acute pseudo-obstruction of the colon, diagnosed via abdominal X-ray or CT scan.
What is the treatment for Ogilvie’s syndrome?
Supportive care and neostigmine if severe dilation is present.
How is a suspected postoperative myocardial infarction diagnosed?
ECG and troponin levels.
How is postoperative bleeding managed?
Assess vitals, CBC, coagulation panel, and surgical site for signs of hemorrhage; transfuse if necessary.
What are the most common causes of hypoxemia in postoperative patients?
- Residual anesthesia effect
- Airway obstruction and edema
- Bronchospasm
- Atelectasis
- Pneumonia
- Pulmonary embolism
- Aspiration
- Heart failure
What are the earliest causes for postoperative hypoxia?
Residual anesthesia effect, airway obstruction and edema, as well as bronchospasm.
What form of postoperative hypoxia is associated with wheezing?
Bronchospasm is a potential cause of early postoperative hypoxemia. Patients will experience wheezing on physical examination. This tends to occur early postoperatively.
Who are at greatest risk for hypercapnic, hypoxic, respiratory failure, seen in postoperative hypoxia (secondary to residual anesthesia effect)?
Postoperative hypercapnic and hypoxic respiratory failure, most likely due to residual anesthesia effect, has a predilection for patients with underlying obstructive sleep apnea. These patients are at further risk due to sedation and neuromuscular blockers causing decreased pharyngeal muscle dilator tone and a higher propensity for obstructive apneic or hypopneic events. These factors can lead to severe hypoventilation and respiratory failure immediately following or shortly after surgery due to the effects of sedation, opioid analgesia, and anesthesia, which place patients at risk for respiratory failure due to decreased central respiratory drive and a depressed state of arousal.
How do both the respiratory rates and tidal volumes impact patient’s ABGs and Aa gradient if they have respiratory failure due to residual anesthesia?
Patients with respiratory failure due to residual anesthesia effect are typically somnolent with decreased respiratory rate and tidal volume, and will have hypoinflation on chest x-ray. Arterial blood gas will demonstrate respiratory acidosis with a normal alveolar-arterial (A-a) gradient. Because the hypoxemia is due to hypoventilation and A-a gas exchange is intact, the hypoxemia typically corrects with supplemental oxygen.
A patient has stridor and hypoxemia postoperatively, what is the likely underlying cause?
Upper airway (laryngeal) edema is a potential complication early in the postoperative period. There is an increased risk of airway obstruction and edema following endotracheal intubation that presents in the early postoperative period. Patients usually have stridor with tachypnea and increased work of breathing.
Who are at the greatest risk for developing postoperative pulmonary complications (PPCs)?
Patients with the following underlying medical conditions are at the greatest risk for developing PPC: COPD, Cigarette smoking, Sleep apnea, and Heart failure.
PPCs are most common after thoracic and upper abdominal surgery due to reduced lung volumes from diaphragmatic dysfunction and splinting (reduction in inspiration depth due to pain). Common PPCs include atelectasis, infection, hypoxia, and respiratory failure.
How long should patients stop smoking prior to surgery?
4 weeks.
Does incentive spirometry significant;y help to improve postoperative complications?
Incentive spirometry and deep breathing exercises are often prescribed postoperatively with the intent to increase lung volume and minimize atelectasis. However, meta-analysis shows that these therapies have little or no benefit.
Is Atelectasis a common finding immediately after surgery?
Atelectasis is a common cause of postoperative hypoxemia that can occur 2-5 days following surgery; however, it is uncommon immediately following surgery. It is no longer considered as a factor that causes post-operative fever.
Does atelectasis tend to cause fever?
No.
What is the classic ABG finding in postoperative atelectasis?
Atelectasis causes hypoxemia due to intrapulmonary shunting, the hypoxemia fails to correct with supplemental oxygen and the A-a gradient is typically elevated. Patients have respiratory alkalosis with low PaO2 and low PaCO2.
How is postoperative atelectasis typically managed?
Encourage incentive spirometry, early ambulation, deep breathing exercises, and adequate pain control.
When does postoperative pneumonia tend to occur?
Within the first week postoperatively (1 to 5 days)
When does postoperative pulmonary embolism tend to occur?
Usually anytime after 3 days. Postoperative patients are at increased risk of pulmonary embolism (PE); however, PE in the immediate postoperative period is rare. In addition, acute PE usually presents with respiratory alkalosis due to hyperventilation, and an elevated A-a gradient is expected due to ventilation/perfusion mismatch.
What are the major causes of decreased urine output in postoperative patients?
Pre-renal (hypovolemia), intrinsic renal (acute tubular necrosis), and post-renal (obstruction).
What is the minimum urine output required in adults postoperatively?
0.5 mL/kg/hr.
What is the minimum urine output required in children postoperatively?
≥1 mL/kg/hr.
Why does postoperative urinary retention (POUR) occur in patients who undergo anesthesia?
POUR is the inability to void after a surgical procedure, commonly due to anesthesia-induced bladder dysfunction and large intraoperative fluid administration. The anesthesia causes bladder stretch-receptor dysfunction and decreased detrusor contractility,
What classic case presentation should raise suspicion for postoperative urinary retention?
A patient with recent surgery, mild nausea, suprapubic tenderness, abdominal distension, and inability to void despite adequate hydration and normal hemodynamic status.
What are the major risk factors for postoperative urinary retention?
- Age ≥50 years
- Surgery duration >2 hours
- Intraoperative fluid administration >750 mL
- Regional anesthesia, 5. Neurological disease
- Underlying bladder dysfunction
- Previous pelvic surgery
Why does large-volume intraoperative fluid administration contribute to postoperative urinary retention?
Excess fluid administration rapidly fills the bladder, but anesthesia-induced detrusor dysfunction prevents normal voiding, leading to retention.
How does regional anesthesia increase the risk of postoperative urinary retention?
Regional anesthesia (e.g., spinal or epidural) blocks autonomic bladder control, leading to decreased detrusor contractility and impaired voiding reflexes.
Which neurological diseases increase the risk of postoperative urinary retention?
Spinal cord injury, multiple sclerosis, Parkinson’s disease, and diabetic autonomic neuropathy all impair bladder function and increase POUR risk.
Why does previous pelvic surgery increase the risk of postoperative urinary retention?
Pelvic surgery can cause scarring and nerve damage affecting bladder innervation, reducing detrusor contractility.
What are the classic clinical features of postoperative urinary retention?
Decreased urine output, suprapubic pain or pressure, and abdominal distension.
Why do patients with POUR experience suprapubic tenderness?
Bladder overdistension due to retained urine causes stretching of the bladder wall, leading to suprapubic discomfort.
What is the first-line management for postoperative urinary retention?
Indwelling catheter placement, which is both diagnostic (confirming large retained urine volume) and therapeutic (relieving bladder distension).
What is the most appropriate initial diagnostic test for suspected postoperative urinary retention?
Bladder ultrasound to assess for urinary retention, though catheterization is often performed directly if clinical suspicion is high.
What is the next step after catheterization in patients with POUR?
Patients typically undergo an outpatient voiding trial within a week, after which the catheter is removed if normal voiding resumes.
Why is an outpatient voiding trial performed after treating postoperative urinary retention?
To ensure the patient has regained normal bladder function before permanently removing the catheter and preventing recurrence.
Why is immediate catheterization important in postoperative urinary retention?
Delayed bladder decompression increases the risk of permanent bladder dysfunction due to detrusor muscle overdistension and injury.
How can postoperative intra-abdominal hemorrhage mimic postoperative urinary retention?
Both conditions can present with decreased urine output, but intra-abdominal hemorrhage is associated with hemodynamic instability (hypotension, tachycardia) and peritoneal signs (rebound, guarding).
How does intraoperative bladder injury differ from postoperative urinary retention?
Bladder injury often results in immediate anuria due to cystotomy, whereas POUR presents with bladder distension and discomfort despite adequate renal function.
How does intraoperative urethral injury present differently from postoperative urinary retention?
Urethral injury leads to decreased urine output with peritonitis signs (rebound, guarding) due to urine leakage into the abdominal cavity.
How does small bowel obstruction differ from postoperative urinary retention?
Small bowel obstruction typically presents 2–3 days postoperatively with nausea, vomiting, severe abdominal pain, and obstipation, whereas POUR presents earlier and lacks significant nausea or vomiting.
