What is the appropriate management of rigors?

Management of Rigors

Treat rigors immediately with meperidine 25 mg IV (may repeat once within 30 minutes) or hydromorphone 0.5 mg IV every 15 minutes up to 3 total doses, while simultaneously investigating and treating the underlying cause. 1

Immediate Symptomatic Management

• Administer meperidine 25-50 mg IV every 4 hours as needed for active rigors, with the option to repeat an additional dose within 30 minutes of the initial dose if rigors persist 1
• Alternatively, use hydromorphone 0.5 mg IV every 15 minutes as needed for rigors, repeating up to 3 total doses for severe episodes 1
• Give acetaminophen 650 mg PO every 4 hours on a scheduled basis (not as needed) when fever exceeds 100.5°F (38°C), as fever commonly accompanies rigors 1
• Consider indomethacin 50-75 mg every 6 hours for refractory fever and rigors, but discontinue immediately if serum creatinine exceeds 2 mg/dL, urine output decreases, or platelets fall below 50,000 x10^9/L 1

Critical Diagnostic Workup

The presence of rigors should trigger immediate evaluation for sepsis or severe infection, as this is a life-threatening emergency requiring intervention within one hour. 1

• Obtain at least two sets of blood cultures (one drawn percutaneously and one through each vascular access device if present >48 hours) before antimicrobials, but do not delay antibiotics beyond 45 minutes 1
• Assess for sepsis using clinical criteria: hypotension, altered mental status, tachypnea, or elevated lactate levels 1
• Consider malaria in any patient with travel history to endemic regions presenting with cyclical fevers and rigors, even if initial blood smears are negative 2, 3
• Perform imaging studies promptly to identify potential sources of infection requiring source control 1

Antimicrobial Therapy Decision Algorithm

If sepsis or septic shock is suspected, administer IV antimicrobials within one hour of recognition—this is non-negotiable. 1, 4

• Initiate empiric broad-spectrum therapy covering all likely bacterial pathogens (and fungal/viral if indicated) before culture results return 1, 4
• For septic shock specifically, use combination empiric therapy with at least two antibiotics from different antimicrobial classes targeting the most likely pathogens 1, 4
• Reassess antimicrobial regimen daily for potential de-escalation once pathogen identification and sensitivities are available 1, 4
• Discontinue combination therapy within 3-5 days, narrowing to targeted single-agent therapy as soon as susceptibility profiles are known 1, 5

Hemodynamic Support

Target mean arterial pressure ≥65 mmHg in patients with septic shock. 1, 4

• Administer 30 mL/kg IV crystalloid fluid within the first 3 hours of recognizing sepsis-induced hypoperfusion 4
• Use norepinephrine as the first-choice vasopressor if hypotension persists despite fluid resuscitation 4
• Monitor urine output targeting ≥0.5 mL/kg/hour and check serum creatinine twice daily during acute illness 1

Special Considerations for Malaria

In patients with travel history to endemic areas presenting with cyclical fevers and rigors, initiate empiric antimalarial therapy even with negative blood smears if clinical suspicion is high. 3

• Intravenous artesunate is the treatment of choice for severe falciparum malaria 6, 7
• Monitor for hypoglycemia, lactic acidosis, and acute kidney injury, which are common metabolic complications 6, 7
• Recognize that P. vivax can also cause severe malaria in Asia, not just P. falciparum 7
• Blood smears and PCR may be falsely negative in some malarial strains with low circulating biomass, so clinical judgment supersedes negative testing 3

Common Pitfalls to Avoid

• Do not delay antimicrobials while waiting for culture results if sepsis is suspected—every hour of delay increases mortality 1, 4
• Do not treat rigors symptomatically without investigating the underlying cause—rigors are a red flag for serious infection 1, 2
• Do not use NSAIDs like indomethacin in patients with renal dysfunction (creatinine >2 mg/dL) or thrombocytopenia (platelets <50,000) 1
• Do not dismiss malaria in returning travelers with negative initial blood smears—repeat testing and consider empiric treatment based on clinical presentation 3