Approach to fevers and management ..pptx

Introduction:

Fever, a common clinical symptom, represents an elevation in body temperature above the normal range due to a regulated increase in the hypothalamic set point. As one of the most frequently encountered symptoms in both outpatient and inpatient settings, understanding the approach to fever is essential for all healthcare professionals. The causes of fever range from benign self-limiting viral infections to life-threatening conditions like sepsis, malignancies, and autoimmune diseases. This presentation aims to equip learners with a comprehensive, step-by-step approach to diagnosing and managing fever, ensuring optimal patient outcomes and judicious use of healthcare resources.

Objectives:

Define fever and its physiological basis.

Understand the pathophysiology and types of fever.

Learn the systematic clinical approach to a febrile patient.

Review common causes based on age, region, and immune status.

Master the diagnostic workup of fever based on clinical clues.

Discuss management principles and red flag signs.

Highlight special types of fever: PUO, neutropenic fever, etc.

Definition and Physiology:

Fever is defined as a temporary increase in body temperature, often due to an illness. The normal body temperature varies based on circadian rhythm, age, and activity but is typically around 36.5–37.5°C (97.7–99.5°F). Fever is generally considered a core body temperature above 38.0°C (100.4°F). The thermoregulatory center in the hypothalamus raises the set point in response to endogenous or exogenous pyrogens. Exogenous pyrogens (e.g., bacterial endotoxins) stimulate the release of endogenous pyrogens (e.g., IL-1, TNF-α, IL-6), which then trigger the synthesis of prostaglandin E2 (PGE2) in the hypothalamus.

Types of Fever:

Fever can be classified based on pattern:

Continuous: Does not fluctuate more than 1°C in 24 hours (e.g., typhoid).

Remittent: Fluctuates more than 1°C in 24 hours, never returns to normal (e.g., infective endocarditis).

Intermittent: Fever spikes separated by periods of normal temperature (e.g., malaria).

Relapsing: Recurrent episodes separated by days of normal temperature (e.g., Borrelia).

Pel-Ebstein: Cyclical fever with days of high fever alternating with afebrile periods (e.g., Hodgkin’s lymphoma).

Clinical Approach to Fever:

A thorough and structured approach includes:

History Taking:

Onset, duration, and pattern of fever

Associated symptoms (e.g., chills, rigors, rash, cough, dysuria)

Exposure history (travel, animal contact, insect bites)

Past medical history (immunosuppression, chronic illnesses)

Medication and vaccination history

Physical Examination:

General assessment (toxicity, dehydration)

Vital signs (fever grade, tachycardia, hypotension)

Systemic examination (focus on skin, ENT, chest, abdomen, CNS)

Red Flags:

Persistent high-grade fever (>39.5°C)

Immunocompromised state

Signs of sepsis (tachycardia, hypotension, altered sensorium)

Organ dysfunction

1. Approach to new fever or rigors in the ICU patient By Dr Sanmay Chowdhury

2. Contents Rapid Reference Definition and Classification of Fever Common causes of Fever Evaluation Management Specific Fever Types Drug Fever Neurogenic Fever

3. Approach to fevers and rigors in ICU        History: Any localizing symptoms ? Recent procedures or transfusion ? Indwelling Devices Exam: Respiratory(If intubated : Sputum ? Increasing Ventilator Support ? Abdominal Tenderness ? Skin Exam ( Focus on Surgical Incisions, line/drain sites)

4. Evaluation Basic Evaluation: Chest X-Ray ( Unless not intubated and no respiratory symptoms Additional tests only if indicated: C. Difficile, if diarrhea.        Sputum culture  only  for patients diagnosed with  probable VAP .        Urine culture  only  if: i ) Urinary symptoms & no foley catheter. ii) Urologic issue (e.g., obstruction/surgery/renal transplant)

5. Management: Treat any identified source of infection Avoid empiric, broad spectrum antibiotics – unless neutropenic or in septic shock D/C lines as able D/C drugs , if possibly causing Drug Fever Acetaminophen only if : Neurological injury Severe fever ( >40C/ >104F Fever causing clinical detoriation ( e. g delirium)

6. Exam for a febrile ICU patient

7. Definition of Fever : Fever is a bedrock concept in medicine, yet its precise definition remains a bit elusive. • The Infectious Disease Society of America defined fever in the ICU as a temperature above 38.3/101. This is generally a useful rule of thumb. However, a lower threshold for fever (>38/100.4 ) may be appropriate in some patients: • Immunocompromised patients (e.g. neutropenic). • Elderly patients. • Patients on scheduled acetaminophen or NSAIDS .

8. * • Precise temperatures may vary, depending on the site and the technique of measurement. Ideally, core temperature should be measured (e.g., rectal or esophageal temperature). However, in practice this is not routinely performed. • Once patients have been in the ICU for a few days, their fever curve may be more informative than any single measurement. A consistent trend over multiple time-points may be more likely to reflect a true event. Alternatively, a one-time fever spike which is below 38.9/102 and immediately disappears is less likely to represent infection.

9. Graph of Temperature and WBC count

10. D efinition of ICU-acquired fever This chapter explores new-onset fevers which occur after a couple days in the ICU, suggesting that the fever results from a process acquired  within  the hospital.  For patients who develop fevers shortly after ICU admission, the differential diagnosis will be broader (with a greater focus on community-acquired infection). ICU-acquired fever should ideally be better defined.  Based on definitions of ventilator-associated pneumonia, a fever arising >48 hours after hospital admission might be more likely to have been acquired within the hospital.

11. R ecognition of neutropenic fever Neutropenia is defined as absolute neutrophil count < 500 , or between 500-1000 and falling • Absolute neutrophil count = ( WBC ) ( % bands + % neutrophils ) . MDCalc calculator for absolute neutrophil count . • Fever in the context of neutropenia is defined as a temperature above hour , or a single measurement above 38.3 / 101 . • Neutropenic fever is critical to recognize , because these patients require empiric broad - spectrum antibiotics .

12. Recognition of Hyperthermia Hyperthermia has its own differential diagnosis and requires specific treatment . More on the critical distinction between fever versus hyperthermia . • Hyperthermia is defined as elevated temperature resulting from extreme heat generation , rather than from an alteration of the hypothalamic set point . • Hyperthermia is suggested by the following clinical features : • Extreme temperature elevation ( temperatures above roughly -41 / 105.8 • Skin may be hot and dry ( but not always ! ) . • Antipyretics are ineffective. Hyperthermia has its own differential diagnosis and requires specific treatment . More on the critical distinction between fever vs hyperthermia

13. Fever VS Hypothermia

14. A ppreciation of spontaneous rigors as a fever-equivalent • Rigors are shaking chills , which which can be very dramatic . They represent an aggressive attempt by the hypothalamus to rapidly increase body temperature . A rigor will often precede development of a fever . • Rigors are closely linked to bacteremia . Although not supported by evidence specific to the ICU environment , it's logical to investigate a patient with new - onset rigors in the same fashion as a patient with new - onset fever . Overall , evidence linking rigors to bacteremia is probably more persuasive than evidence linking fever to bacteremia .

15. Common Causes of Fever Infectious infections ( causing -50 % of fever in ICU ) • Pneumonia . . C. difficile . • Intravascular catheter infection . ● Surgical site infection . Metastatic or local complications from known infection ( e.g. , empyema , spinal abscess following endocarditis ) . • Less often • Acalculous cholecystitis . • Cellulitis , including infected decubitus ulceration . • Spontaneous bacterial peritonitis ( SBP ) . • Urinary tract infection following the removal of a Foley catheter . • Urinary tract infection in a patient with a functioning Foley catheter ( rare )

16. Non Infectious causes of Fever Procedure - related : ● Hemodialysis . • Bronchoscopy . • Febrile transfusion reaction ( within 6 hours of transfusion ) . • Benign postoperative fever ( post - operative day # 1-3 ; usually < 39C / 102F ) . • Medication - related : • Drug fever ( more on this below ) .

17. Non infectious causes pf fever • Medication - induced hyperthermia ( serotonin syndrome , neuroleptic malignant syndrome , malignant hyperthermia ) . • Sterile pulmonary inflammation ( e.g. , ARDS , cryptogenic organizing pneumonia , aspiration pneumonitis ) . • Pulmonary embolism ( usually low - grade fever , < 39/102 ) . ( 10631196 ) • Neurogenic fever ( more on this below ) . • Disorders which seldom arise in the ICU ( yet may remain possible ) : Pancreatitis . • Thyroid storm or adrenal insufficiency . • Rheumatologic disorders ( vasculitis , flare or gout or underlying rheumatologic disease ) . • Malignancy ( especially lymphoma , hepatocellular carcinoma , renal cell carcinoma ) . Hemophagocytic lymphohistiocytosis ( HLH ) ,

18. Evaluation: Physical examination as above. Chest X-ray if the patient is intubated or has respiratory symptoms. Blood cultures: Two sets of peripheral blood cultures at different sites (each set contains an anaerobic bottle and an aerobic bottle). Additionally, any line in place >48-72 hours should be cultured .

19. U rine culture should usually be avoided  Why avoid urinalysis and urine culture? These are frequently  positive  in elderly patients, or anyone with a prolonged Foley catheter. In patients with a Foley catheter, it's  extremely unusual  for urinary tract infection to be a cause of fever in the absence of urological manipulations, neutropenia, or Foley dysfunction.( 23878765 ,  18379262 ) Routinely obtaining urinalysis and urine culture will lead to overdiagnosis of urinary tract infections. Bladder ultrasound to exclude Foley catheter dysfunction Obstruction of the Foley catheter causing inadequate drainage of urine  may  cause ascending urinary tract infection. For an ICU patient with a Foley catheter, the best way to evaluate for urinary tract infection may be bladder ultrasound to exclude Foley dysfunction (the presence of a significant volume of urine in the bladder indicates inadequate drainage).

20. Indications  to obtain a urinalysis and urine culture: (1) Patient who lacks a Foley catheter and has signs/symptoms of urinary tract infection. (2) Neutropenia. (3) Structural urologic abnormality (e.g., recent surgery or urological procedure, or status post renal transplant) More information in the chapter on catheter-associated urinary tract infection here (REF).

21. T racheal aspirate cultures should usually be avoided  Tracheal aspirate cultures will often be positive among patients with structural lung disease (i.e., COPD) or prolonged intubation (often with scary bacteria such as Pseudomonas).  However, in the absence of other features of infection, this reflects only  colonization  and should not affect management. Cultures should be obtained  only  if there is a clinical suspicion of a ventilator-associated pneumonia.

22. O ther testing based on clinical scenario Clostridioides difficile testing is indicated for patients with diarrhea. Abdominal imaging is indicated for patients with abdominal pain or recent abdominal instrumentation.  CT scan of the abdomen/pelvis is often most useful as a survey study, but right upper-quadrant ultrasonography may be useful if there is localizing pain in the right upper quadrant. If there are clinical features suggestive of venous thromboembolic disease, DVT ultrasonography or CT angiography of the chest may be warranted. Lumbar puncture is indicated if there is a  reason  to suspect meningitis (e.g., recent craniotomy or external ventricular drain).  However, if an external ventricular drain is in place, fluid may be removed directly from the drain to avoid the risk of lumbar puncture. Paracentesis should be considered in the context of ascites, to exclude spontaneous bacterial peritonitis (SBP).

23. Management: I ndications for empiric antibiotics Fever itself isn't an indication for antibiotics. (They're  antibiotics , not  anti- pyretics .) Antibiotics may be indicated in the following situations: (a) Neutropenic fever (b) Septic shock (e.g., hypotension, tachycardia, oliguria, delirium, tachypnea ).  More on sepsis  here . (c) High index of suspicion for specific infection (e.g., Clostridioides difficile or ventilator associated pneumonia).  In many situations antibiotic initiation for a specific focus of infection is appropriate, while awaiting additional diagnostic information (e.g., culture results).

24. A ntipyretic therapy: Whether fever is a beneficial, adaptive response to infection remains controversial. • Most fevers don't require treatment. Following the fever curve without antipyretic therapy may provide superior diagnostic information. & A single fever spike which is transient and self-resolving is unlikely to represent true infection. Avoiding the urge to treat with antipyretics or antibiotics allows the wisdom of time to establish the fever's benignity. Isolated fever spikes sometimes result from manipulation of a colonized mucosal surface.(9448975) • Potential indications for acetaminophen are: • Neurologic injury (e.g., stroke, anoxic brain injury). • Severe fever (e.g. over roughly >40C/104F). • Fever that seems to be worsening the patient's clinical condition: • Altered mental status (fever can cause delirium in some at-risk patients). • Hemodynamic instability or acute myocardial ischemia (tachycardia may exacerbate both of these). • Multiple sclerosis patients (fever may cause acute deterioration - known as Uhthoff Phenomenon).

25. C entral venous catheter removal • Fever alone isn't necessarily an indication to remove a central venous catheter. However, central venous catheter removal should be considered for lines in place >72 hours. • If the patient is unstable and manifests features of sepsis (e.g., hemodynamic instability), line removal may be more strongly considered. • More on this in the chapter on catheter-related bloodstream infection. You are here:  Home  / IBCC / Approach to new fever or rigors in the ICU patient       

26. Drug Fever Commonly Implicated Drugs : Antimicrobials (most common class): Penicillins , cephalosporins, piperacillin, carbapenems. Aminoglycosides (rare), fluoroquinolones. Vancomycin, daptomycin, linezolid (rare). Clindamycin (rare). Tetracyclines, macrolides (rare). Isoniazid (INH), rifampin . Sulfonamides , nitrofurantoin, pentamidine. Antiretrovirals. Amphotericin B. Cardiac/renal: Antihypertensives:  Captopril, hydralazine, nifedipine. Digoxin (rare). Sulfa -containing diuretics (e.g., furosemide). Antiarrhythmics:  Procainamide, quinidine. Antiepileptic agents: Barbiturates. Phenytoin. Carbamazepine. Immunologics : Interferon. Azathioprine.

27. Epidemiology Exact numbers are hard to track, but drug fever may occur in up to ~10% of admitted patients. ( 8698996 ) Risk factors for drug fever: Sensitivities to multiple medications. Polypharmacy. HIV infection. Cystic fibrosis .

28. Clinical Findings: Fever may occur to any degree, most commonly the temperature is ~102-104F (~38.8-40C). Patients can be asymptomatic or may look profoundly ill (e.g., with rigors, myalgias, and hypotension). One clue suggesting drug fever may be that a patient looks “inappropriately well” compared to the degree of fever.( 23878765 ) Rash is seen only in ~20% of patients (usually a maculopapular central rash, which may involve palms and soles). Timing of drug fever is  variable.   Drug fevers frequently begin 1-2 weeks after starting a medication, but they may emerge after months or years.  Upon drug re-challenge, fever may develop within hours.

29. Laboratory Abnormalities Leukocytosis with left shift may occur in 18% of patients. Eosinophilia is seen only in ~18% of patients.  If present, consider also whether the patient could have DRESS syndrome (Drug Reaction with Eosinophilia and Systemic Symptoms).

30. Diagnosis and Treatment Definitive diagnosis is often impossible (as drug fever is largely a diagnosis of exclusion). After discontinuing the offending agent, fever should resolve within 3-4 days if no rash is present.  However, sometimes resolution may take a week.

31. Neurogenic Fever Pathophysiology: Neurogenic fever (a.k.a. “central fever”) appears to represent a hypothalamic disorder, resulting in an elevation of the hypothalamus's target temperature for the body (the “set point”).( 26772198 ) Causes : Subarachnoid hemorrhage Extremely common, affecting  most  patients. Risk factors include more severe subarachnoid hemorrhage and coexisting intraventricular hemorrhage . Intracranial hemorrhage with ventricular extension. Traumatic brain injury.

32. Clues supporting a neurogenic fever Occurrence within 72 hours of admission. Poor response to antipyretics (<10% will defervesce). Presence of subarachnoid or intra-ventricular blood. Fever usually isn't associated with diaphoresis or tachycardia. Longer duration of fever.

33. Diagnosis of a Neurogenic Fever Ultimately this is largely a diagnosis of exclusion. Neurogenic fever may be likely if: (a) A reasonably exhaustive evaluation fails to identify an alternative explanation for the fever. (b) Clinical features of the fever are consistent with neurogenic fever (as above).

34. Management Neurogenic fever is often resistant to antipyretics. Reduction in temperature usually requires physical cooling (e.g., with a cooling blanket or physical temperature control device). These patients often have neurologic injury, so treatment of the fever may be important to limit secondary neurologic injury. Shivering should be treated aggressively, as this may increase the intracranial pressure.  Potential treatments include the following (often more than one therapy will be needed): Aggressive IV magnesium repletion. Warming of the hands and feet. Infusions of dexmedetomidine, propofol, and/or pain-dose ketamine. Ondansetron 4 mg IV q8hr. Fentanyl boluses (these are preferred over meperidine, due to a superior safety profile). Paralysis is a treatment of last resort only.