ICU Basics

First five minutes

New Fever in the ICU Algorithm

Shock check, cultures, the source hunt and the mimics

Reviewed by Alex G, BSN, RN, CEN, CCRN, CMC, NREMT-P · From the Reference tab of the app

Each step lists what to do, then the choices that lead on. In the app the algorithm is tapped through one decision at a time.

1 Confirm the fever and look at the patient

  • Fever is 38.3 °C (101 °F) or higher (SCCM/IDSA); with neutropenia, 38.3 °C once or 38.0 °C for an hour
  • Reliable method: bladder, esophageal or PA catheter probe, then oral or rectal (no rectal if neutropenic); not axillary, tympanic or temporal
  • Full vital signs, SpO₂, mental status, urine output, skin and capillary refill
  • Unstable: call the rapid response team or provider now; monitor, oxygen, IV access
  • Note new drugs, procedures, anesthesia, transfusions, and each line with its days in place

Blood product running or given in the last 4 hours → step 2Rigid muscles or clonus, or rising EtCO₂ and HR after anesthesia → step 3Low BP, new organ dysfunction or neutropenia → step 4Stable, no organ dysfunction → step 5

2 Fever with a transfusion: stop it

  • Stop the transfusion; keep the IV open with saline through new tubing
  • Vital signs; recheck the patient ID against the unit label; call the provider and the blood bank
  • Return the bag and tubing; send blood for a DAT and repeat type and screen, and urine for hemoglobin
  • Rigors, hypotension or a rise of 2 °C or more: blood cultures from the patient; ask the blood bank to culture the bag
  • New hypoxia or pulmonary edema in the hours after: TRALI or TACO; support breathing and call now

Hypotension, rigors, back pain, dark urine or oozing → step 4Stable, fever only → step 6

3 Heat from muscle: which syndrome fits?

  • Cool physically now: ice packs to neck, axillae and groin, a cooling device, cold IV fluids; antipyretics will not work
  • Call the provider now; CK, potassium, creatinine and a blood gas; review every drug given in the past days

During or soon after a volatile anesthetic or succinylcholine; EtCO₂ rising → step 7Antipsychotic or metoclopramide, or stopped levodopa; rigidity over days → step 8Serotonergic drug; clonus and hyperreflexia within hours → step 9None of these fits → step 5

4 Shock, probable sepsis or neutropenia: antibiotics within 1 hour

  • Call the rapid response team or provider now; time zero is recognition; follow the Sepsis: Hour-1 Bundle
  • Lactate; two blood culture sets, then broad-spectrum antibiotics within 1 hour (SSC 2021)
  • Hypotension or lactate 4 or more: 30 mL/kg balanced crystalloid within 3 hours, reassessing after each bolus
  • MAP under 65 during or after fluids: norepinephrine; a peripheral start is fine
  • Long-term steroids or adrenal insufficiency: hydrocortisone 100 mg IV for possible adrenal crisis

Next: hunt the source → step 10

5 Stable, sepsis possible: rapid workup

  • Tell the provider now; vital signs, mental status and urine output at least hourly
  • Two or more blood culture sets from different sites, drawn back to back (ideally 60 mL of blood in all)
  • Lactate, CBC, chemistry, liver tests and a chest x-ray; procalcitonin helps when infection is uncertain
  • Infection still likely: antibiotics within 3 hours (SSC 2021); unlikely: hold them and keep watching
  • Worse at any point (hypotension, rising lactate, new organ failure): antibiotics within 1 hour

Next: hunt the source → step 10

6 Comfort and cooling

  • No antipyretics just to lower the number (SCCM/IDSA 2023); in infection it did not improve survival (HEAT 2015)
  • For comfort, an antipyretic is preferred over cooling blankets (SCCM/IDSA 2023)
  • Acetaminophen 650–1,000 mg every 6 h, max 4 g/day (less with liver disease or alcohol use); IV doses can drop BP
  • Brain injury, stroke or SAH: keep normothermic; comatose after cardiac arrest: 37.5 °C or less as ordered
  • Treat fever that strains a failing heart or lungs; with a cooling device, prevent and report shivering

Next: report → step 11

7 Malignant hyperthermia: dantrolene now

  • Call for help, anesthesia and the MH cart; stop volatile agents and succinylcholine
  • Clues: EtCO₂ rising despite more ventilation, fast HR, masseter or total rigidity, acidosis, high potassium
  • 100% oxygen at 10 L/min or more; dantrolene 2.5 mg/kg IV rapidly, repeated until signs resolve
  • Cool if over 39 °C and stop at 38 °C; call the MH hotline (US 1-800-644-9737)
  • Follow the Malignant Hyperthermia algorithm; ICU monitoring for at least 24 hours

End of this path.

8 Neuroleptic malignant syndrome

  • Hold the antipsychotic or metoclopramide and call the provider; restart levodopa or the dopamine agonist if it was stopped
  • Clues: fever, lead-pipe rigidity, confusion, labile BP and HR, CK 4 times normal or more
  • Cool physically; IV fluids to protect the kidneys; check CK, potassium and creatinine
  • Benzodiazepine for agitation; severe rigidity or fever: dantrolene or bromocriptine per the provider
  • ICU monitoring for airway, aspiration, arrhythmia and kidney injury; no antipsychotic until it resolves

End of this path.

9 Serotonin syndrome

  • Hold every serotonergic drug and call the provider: SSRIs, SNRIs, MAOIs, linezolid, methylene blue, tramadol, fentanyl, ondansetron
  • Clues: onset within hours; clonus (legs more than arms), hyperreflexia, tremor, agitation, sweating, diarrhea
  • Benzodiazepine for agitation and tremor; avoid physical restraint, which makes more heat
  • Cyproheptadine 12 mg by mouth or tube per the provider (evidence is weak); poison center 1-800-222-1222
  • Over 39 °C with rigidity, agitation, falling consciousness or failed cooling: call for sedation, intubation and nondepolarizing paralysis (never succinylcholine)

End of this path.

10 Hunt the source, head to toe

  • Lines: site redness or pus, days in place; cultures from the line (two lumens) and a vein at the same time
  • Lungs: secretions, oxygen need, chest x-ray; ventilated: tracheal aspirate; viral PCR panel if respiratory signs
  • Urine: culture when a urinary source is suspected; with pyuria and a catheter, replace it and culture from the new one
  • Skin and gut: wounds, surgical sites, pressure injuries; C. difficile test for 3 or more loose stools in 24 h without laxatives
  • Hidden: sinusitis (nasal tubes), abdomen (CT after surgery), acalculous cholecystitis (ultrasound), EVD or shunt (CSF), endocarditis

Likely source found → step 12No clear infection → step 13

11 Report and reassess

  • SBAR: temperature and how it was measured, vital signs trend, mental status, urine output, lactate
  • Lines and days in place, recent procedures, transfusions, new drugs, stool count, wound changes
  • What is done: culture times, first antibiotic time, fluids given, cooling started
  • Ask for: the antibiotic plan, imaging of the suspected source, procalcitonin or a repeat lactate
  • Recheck vital signs every 15 minutes while unstable; repeat lactate in 2–4 hours if it was over 2

End of this path.

12 Source found: control it

  • Infected line: remove it once other access works
  • Abscess, empyema, obstruction or dead tissue: surgery or IR drainage, ideally within 6 hours (SSC 2026)
  • C. difficile: contact precautions, soap-and-water hand hygiene; oral vancomycin or fidaxomicin
  • Antibiotics matched to the source; narrow to culture results at 48–72 hours

Next: comfort and cooling → step 6

13 No infection found: think of the mimics

  • Drug fever: beta-lactams, sulfa drugs, phenytoin, heparin; often 7–10 days in; fades within 72 h of stopping
  • Clots and inflammation: DVT or PE, pancreatitis (lipase), gout, hematoma, ischemic bowel
  • Adrenal crisis (shock despite fluids and pressors, low Na, high K, low glucose): hydrocortisone 100 mg IV now
  • Thyroid storm, alcohol withdrawal, stimulant or anticholinergic toxicity; stroke, ICH or SAH (central fever)
  • After surgery, fever in the first 48 hours is usually inflammatory; still look if the patient is unwell

Next: comfort and cooling → step 6

Drugs in this algorithm

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