Surgical Complications



  • Any negative outcome in operative or postoperative period; no consensus on definition
  • Multiple classification systems exist based on severity.


Incidence varies with type of operation, operative time, hospital, surgeon, and patient comorbidities.

  • Emergent cases associated with more complications than nonemergent cases (23% vs. 14%) and have higher mortality rate (6% vs. 1%) (1)
  • Mortality rate in general and vascular surgery is 4–7% (2).
  • Overall complication rate in general and vascular surgery is 24–27%.
  • Lower morbidity and complication rates for complex surgeries performed at high-volume centers
  • Postoperative fever is very common. Incidence ranges 14–91% (3).
  • Rate of venous thromboembolic events: 3/1,000 surgical discharges in the United States
  • Complications after bariatric surgery: anastomotic leak (0–6%), internal hernia (3–5%), marginal ulcer (1–16%), GI bleeding (0.6–4%), and acute distention of distal stomach
  • Rate of ventral hernia after laparotomy: 2–25% (4)
  • Surgical site infection (SSI) incidence varies with type of operation.
    • 1–2% clean operative site (e.g., hernia repair)
    • 5–15% clean contaminated site (e.g., cholecystectomy)
    • 10–20% contaminated site (e.g., colectomy)
    • 50% dirty operative site

Etiology and Pathophysiology

  • Fever
    • Caused by pyrogens (mediated by IL-1, IL-6, TNF, interferon-γ): bacteria, viruses, antigen–antibody complexes
    • Most common noninfectious causes of postoperative fever: deep vein thrombosis (DVT), gout, transfusion reaction, alcohol withdrawal, hematoma, medication, pancreatitis (3)[C]
    • Fever in the first 24 hours is usually due to atelectasis. Consider the “5 Ws”:
      • Wind—atelectasis, aspiration (24 to 48 hours)
      • Water—UTI (72 hours)
      • Walking—deep venous thrombosis (7 days)
      • Wound—SSI (4 to 5 days typically but anytime)
      • Wonder drugs—drug fever (anytime)
    • Emergent causes of early postoperative fever (24 to 48 hours): necrotizing infection, pulmonary embolus, anastomotic leak, adrenal insufficiency, alcohol withdrawal, and malignant hyperthermia (3)[C]
  • Wound complications
    • Wound infection
      • Staphylococcus aureus is the most common cause of wound infection. Others include Streptococcus, Pseudomonas, Proteus, and Klebsiella.
      • Necrotizing wound infections/fasciitis: can occur within 24 hours; common bacteria: group A Streptococcus, Clostridium perfringens
    • Wound dehiscence: poor wound healing, malnutrition, excessive tension, poor surgical technique, diabetes, obesity
    • Seroma: disruption of small blood vessels and inflammation
    • Hematoma: usually from inadequate hemostasis
  • DVT (Virchow triad):
    • Hypercoagulability
    • Hemodynamic changes (stasis, turbulence)
    • Endothelial injury/dysfunction
  • Cardiac
    • Postoperative myocardial infarction (MI) typically occurs within 3 days of surgery.
    • Arrhythmia (particularly atrial fibrillation) occurs due to electrolyte abnormalities, catecholamine release (pain), hypercapnia, and digitalis; more common after cardiothoracic surgery
  • Pulmonary
    • Pulmonary mechanics are compromised postoperatively. Precipitating factors include pain and altered mental status.
    • Decreased vital capacity leads to atelectasis, pneumonitis or pneumonia, and acute respiratory distress syndrome (ARDS).
    • Aspiration can occur at any time. Stomach acid/particulate matter causes an inflammatory reaction in airway, leading to respiratory complications.
    • Pulmonary edema due to fluid transudation to alveolus from fluid overload or heart failure
    • Pulmonary embolism: generally, due to thromboembolism from the deep veins of the legs or pelvis; more rarely from air, fat, or amniotic fluid
  • Gastrointestinal
    • Small bowel obstruction: Adhesive bands cause bowel torsion or constriction; can occur at any time after intra-abdominal procedures
    • Postoperative ileus may prolong hospital stay.
    • Fistula/intestinal leak: generally, occurs at the site of bowel anastomosis due to suture or staple line breakdown
    • Stoma complications
      • Include fibrosis of bowel at stoma, necrosis, retraction, skin breakdown, parastomal hernia, prolapse of stoma, and stomal stricture
      • More common in obese patients
  • Renal
    • Renal failure/acute kidney injury
      • Drug toxicity (Antibiotics or IV contrast use are most common.)
      • Inadequate resuscitation leading to poor perfusion (catecholamine release during surgery and activation of renin-angiotensin-aldosterone system) potentially contributes to acute tubular necrosis (ATN)
    • Urinary retention: more frequent in men than women; impaired coordination between α-receptors in the bladder neck and parasympathetic stimulation to the bladder due to anesthetic agents
    • UTI: related to indwelling catheter typically

Malignant hyperthermia syndrome (MHS): autosomal dominant inheritance with incomplete penetrance; a skeletal muscle disorder; hypermetabolic crisis following administration of halogenated inhalational anesthetic agents or succinylcholine

  • Incidence: 1/50 to 100,000; treated with dantrolene
  • No practical screening tests for general population

Risk Factors

  • Patients at increased operative risk include:
    • Poorly controlled diabetes
    • Obesity
    • Heart disease (especially MI and heart failure)
    • Obstructive sleep apnea or preexisting lung disease
    • Smoking: Current smokers have increased rates of major respiratory complications and SSI regardless of procedure, complexity of case, or operative time (5)[B].
    • Bleeding disorders
    • Malnutrition
    • Renal failure
    • Liver disease, especially cirrhosis
    • Immunosuppression
    • Malignancy
  • Other risk factors
    • Prolonged surgery
    • Immobility following surgery
    • Emergency surgery

General Prevention

Preventive measures span entire perioperative period.

  • Assessment of underlying risk factors
  • Smoking cessation
  • Clip hair instead of shaving preoperatively.
  • Appropriate fluid/blood resuscitation
  • Preoperative antibiotics, when appropriate
  • Sterile technique
  • Venous thromboembolism prophylaxis
  • Maintenance of normothermia during surgery
  • Perioperative checklists
  • Enhanced recovery after surgery (ERAS) pathways improve postoperative recovery and decrease complications. These pathways modify perioperative care to reduce surgical stress response, focus on optimizing nutrition, pain control, fluid management, and early mobility.
    • ERAS has been shown to reduce complications in colorectal surgery. Additional pathways for other surgical specialties are emerging.
  • Surgical Risk Calculator, by the American College of Surgeons, can be used to calculate risk of surgical complication.

Commonly Associated Conditions

  • Adrenal insufficiency steroids preoperatively
  • Arrhythmia
  • Pneumonia
  • Liver failure in patients with preexisting disease
  • Renal insufficiency
  • Delirium tremens in alcoholics/delirium

Pediatric Considerations
Operative procedures can lead to severe anxiety in children aged 1 to 2 years, with lasting emotional disturbance in 20%.

Geriatric Considerations
90% of patients >65 years of age experienced depression after surgery, with ADLs impaired in 50%. Increase human contact to prevent withdrawal and reduce symptoms.

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