What are the possible causes of fever after placement of a laryngeal mask airway (LMA)?

Causes of Fever After LMA Placement

Fever following laryngeal mask airway (LMA) placement is most commonly caused by the normal systemic inflammatory response to surgery in the first 48-72 hours, but after 96 hours, infectious causes become equally likely and require systematic evaluation focusing on surgical site infection, urinary tract infection, pulmonary complications, and drug-induced fever. 1, 2

Early Postoperative Period (0-48 Hours)

Normal Inflammatory Response

• Surgery triggers a systemic inflammatory response characterized by fever, which is typically benign and self-limiting during the initial 48 hours after any procedure involving LMA placement 1, 2
• The magnitude of this inflammatory response corresponds to the extent of surgical injury and involves increased production of acute phase proteins 1
• Extensive workup is generally unnecessary for mild fever within 72 hours post-surgery without other symptoms, as this represents normal physiologic response rather than infection 1, 2

Rare Early Infectious Causes

• Group A streptococcal or clostridial infections can develop within 1-3 days after surgery, representing the exceptions to the rule that surgical site infections rarely occur during the first 48 hours 2
• These severe early infections require immediate recognition and intervention despite their rarity 2

Intermediate Period (48-96 Hours)

Airway-Related Complications

• Upper respiratory tract infections (URI) significantly increase the risk of perioperative respiratory complications including bronchospasm and laryngospasm when LMA is used 3, 4
• Children with recent URI who undergo LMA placement have doubled incidence of laryngospasm (odds ratio 2.6), coughing (odds ratio 2.7), and oxygen desaturation (odds ratio 1.9) compared to healthy children 4
• LMA misplacement or stimulation-induced laryngospasm under inadequate anesthesia can trigger inflammatory responses that manifest as fever 3

Emerging Infectious Causes

• By postoperative day 4, fever becomes equally likely to represent surgical site infection or other infectious sources 2
• Hematoma formation can cause fever and may take up to 72 hours to resolve even with appropriate treatment 2

Late Period (>96 Hours)

Surgical Site Infections

• Surgical site infections most frequently manifest between postoperative days 4 and 6, representing "late" infections that are usually polymicrobial 5
• Daily wound inspection is mandatory, specifically looking for purulent drainage, spreading erythema >5 cm from incision with induration, warmth, tenderness, or swelling 2, 5
• Any purulent drainage, even minimal amounts, is diagnostic of surgical site infection and mandates intervention 2, 5

Urinary Tract Infections

• Duration of catheterization is the single most important risk factor for UTI development 2, 5
• Urinalysis and culture are indicated for patients with indwelling catheters for >72 hours or those with urinary symptoms 2

Pulmonary Complications

• Chest radiograph should be obtained only if respiratory symptoms develop, not for isolated fever 1
• Atelectasis should be a diagnosis of exclusion after ruling out other causes, as assuming atelectasis without investigation is a common pitfall 2, 5
• Pulmonary embolism must be considered in patients with risk factors including sedentary status, lower limb immobility, malignancy, or oral contraceptive use 2

Drug-Induced Fever

• Medication review becomes critical when fever persists beyond 48-72 hours or when infectious workup is negative, as drug-induced fever can mimic infectious causes 1
• Drug-induced fever typically develops with a mean lag time of 21 days (median 8 days) after drug initiation, though it can occur within days 1
• Any antibiotic, particularly beta-lactams, can cause postoperative fever 1
• Haloperidol and other neuroleptic medications used perioperatively can cause drug-induced fever 1

Life-Threatening Hyperthermic Syndromes

• Malignant hyperthermia is caused by succinylcholine and inhalation anesthetics (especially halothane), mediated by dysregulation of cytoplasmic calcium in skeletal muscle 1
• Neuroleptic malignant syndrome is strongly associated with haloperidol (most common in ICU), phenothiazines, thioxanthenes, and butyrophenones 1
• These syndromes require immediate recognition and escalation due to extreme hyperthermia and hemodynamic instability 1

Systematic Evaluation Algorithm

Days 0-3

• Perform daily wound inspection but avoid extensive workup unless fever is extreme or accompanied by concerning features 1, 2
• Maintain high suspicion for rare early infections (group A streptococcal, clostridial) if purulent drainage, spreading erythema, or severe pain develops 2

Days 4-5

• Perform urinalysis and culture, followed by wound inspection and blood cultures if indicated by clinical findings 5
• Obtain Gram stain and culture of any purulent drainage before starting empiric antibiotics 2, 5
• Blood cultures should be obtained when temperature ≥38°C is accompanied by systemic signs of infection 2, 5

Persistent Fever Beyond 72 Hours

• Examine all drugs started within the past 3-4 weeks, not just those initiated perioperatively 1
• When infectious causes have been reasonably excluded and drug fever is suspected, discontinue the suspected agent 1
• Consider CT imaging of the operative area in collaboration with surgical service if etiology remains unidentified 1

Critical Pitfalls to Avoid

• Starting empiric antibiotics before obtaining cultures compromises diagnostic accuracy and may mask drug-induced fever 1, 5
• Assuming atelectasis without investigation when it should be a diagnosis of exclusion 2, 5
• Delaying investigation because other findings are unremarkable, as isolated fever on day 5 warrants targeted evaluation 5
• Continuing suspected offending medications "just in case" when definitive diagnosis requires discontinuation 1

When to Escalate Immediately

• Hemodynamic instability or signs of severe sepsis 1
• Respiratory compromise or altered mental status 1
• Extreme hyperthermia suggesting malignant hyperthermia or neuroleptic malignant syndrome 1
• Persistent fever beyond 48-72 hours despite appropriate therapy, indicating possible inadequate source control, resistant organisms, or drug fever 1, 5