Medical Calculators

Emergency Medicine Clinical Calculators

Interactive scoring tools for clinical decision-making at the bedside. Select responses below and scores will calculate automatically. Each calculator can also be found on its relevant topic page.

Cardiac

HEART Score for Major Cardiac Events

Predicts 6-week risk of major adverse cardiac events (MACE) in patients presenting with chest pain.

Use in: Patients ≥21 years old with symptoms suggestive of ACS. Do not use if: New ST-elevation ≥1 mm, hypotension, life expectancy <1 year, or noncardiac illness requiring admission.

HEART Score

HEART Score Calculator

Criteria	Select One
History	Slightly suspicious (0)	Moderately suspicious (+1)	Highly suspicious (+2)
EKG	Normal (0)	Non-specific repolarization disturbance (+1)	Significant ST deviation (+2)
Age	<45 (0)	45–64 (+1)	≥65 (+2)
Risk Factors HTN, hypercholesterolemia, DM, obesity (BMI >30), smoking, family hx CVD, or hx atherosclerotic disease	No known risk factors (0)	1–2 risk factors (+1)	≥3 risk factors or hx atherosclerotic disease (+2)
Initial Troponin	≤normal limit (0)	1–3× normal limit (+1)	>3× normal limit (+2)
HEART Score	/ 10

Interpretation

0–3	Low Risk — 0.9–1.7% risk of MACE. Consider discharge with outpatient follow-up.
4–6	Moderate Risk — 12–16.6% risk of MACE. Consider admission for observation and further workup.
7–10	High Risk — 50–65% risk of MACE. Consider early invasive measures (cardiology consult, catheterization).

References

Six AJ, Backus BE, Kelder JC. Chest pain in the emergency room: value of the HEART score. Neth Heart J. 2008;16(6):191-196. PMID 18665203. Backus BE, Six AJ, Kelder JC, et al. Prospective validation of the HEART score for chest pain patients. Int J Cardiol. 2013;168(3):2153-2158. PMID 23465250. Mahler SA, Riley RF, Hiestand BC, et al. The HEART Pathway randomized trial. Circ Cardiovasc Qual Outcomes. 2015;8(2):195-203. PMID 25737484.

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CHA₂DS₂-VASc Score for Atrial Fibrillation Stroke Risk

Calculates stroke risk for patients with atrial fibrillation, to guide anticoagulation decisions.

Use in: Patients with nonvalvular atrial fibrillation.

CHA₂DS₂-VASc Score

CHA₂DS₂-VASc Score Calculator

Criteria	No (0)	Yes
Congestive heart failure (or LVEF ≤40%)	1	(+1)
Hypertension	1	(+1)
Age ≥75 years	1	(+2)
Diabetes mellitus	1	(+1)
Stroke/TIA/thromboembolism	1	(+2)
Vascular disease (prior MI, PAD, aortic plaque)	1	(+1)
Age 65–74 years	1	(+1)
Sex category (female)	1	(+1)
CHA₂DS₂-VASc Score	/ 9

Interpretation
0	Low Risk — 0.2% annual stroke risk (males). Anticoagulation generally not recommended.
1	Low-Moderate Risk — 0.6% annual stroke risk (males). Consider anticoagulation (esp. if not due to female sex alone).
≥2	Moderate-High Risk — ≥2.2% annual stroke risk. Oral anticoagulation recommended.

References

Lip GY, Nieuwlaat R, Pisters R, et al. Refining clinical risk stratification for predicting stroke and thromboembolism in atrial fibrillation using a novel risk factor-based approach: the Euro Heart Survey on Atrial Fibrillation. Chest. 2010;137(2):263-272. PMID 19762550. January CT, Wann LS, Calkins H, et al. 2019 AHA/ACC/HRS Focused Update of the 2014 Guideline for Management of Patients With Atrial Fibrillation. J Am Coll Cardiol. 2019;74(1):104-132. PMID 30703431.

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Pulmonary

Wells' Criteria for Pulmonary Embolism

Objectifies risk of pulmonary embolism based on clinical criteria.

Use in: Patients with clinical suspicion for PE. Note: Use clinical judgment first; the Wells score helps quantify pre-test probability.

Wells Score for PE

Wells' PE Score Calculator

Criteria	No	Yes	Points
Clinical signs and symptoms of DVT (leg swelling, pain with palpation)	1		+3.0
PE is #1 diagnosis OR equally likely	1		+3.0
Heart rate >100 bpm	1		+1.5
Immobilization (≥3 days) OR surgery in previous 4 weeks	1		+1.5
Previous objectively diagnosed PE or DVT	1		+1.5
Hemoptysis	1		+1.0
Malignancy (treatment within 6 months or palliative)	1		+1.0
Wells' Score	points

Three-Tier Model

0–1	Low Risk — 1.3% incidence of PE. Consider D-dimer to rule out. Consider PERC rule.
2–6	Moderate Risk — 16.2% incidence of PE. Consider high-sensitivity D-dimer or CTA.
>6	High Risk — 37.5% incidence of PE. Consider CTA. D-dimer not recommended.

Two-Tier Model (Preferred by guidelines)

0–4	PE Unlikely — 12.1% incidence. Consider high-sensitivity D-dimer; if negative, stop workup.
>4	PE Likely — 37.1% incidence. Consider CTA testing.

References

Wells PS, Anderson DR, Rodger M, et al. Derivation of a simple clinical model to categorize patients probability of pulmonary embolism. Thromb Haemost. 2000;83(3):416-420. PMID 10744147. van Belle A, Büller HR, Huisman MV, et al. Effectiveness of managing suspected pulmonary embolism using an algorithm combining clinical probability, D-dimer testing, and computed tomography. JAMA. 2006;295(2):172-179. PMID 16403929.

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PERC Rule for Pulmonary Embolism

Rules out PE if NO criteria are present and pre-test probability is ≤15% (low risk by gestalt).

Use in: Low-risk patients where PE has been considered but is not the leading diagnosis. Key point: ALL criteria must be negative (No) to rule out PE.

PERC Rule

PERC Rule Calculator

Criteria	No (0)	Yes (+1)
Age ≥50 years	1
Heart rate ≥100 bpm	1
SpO₂ <95% on room air	1
Unilateral leg swelling	1
Hemoptysis	1
Recent surgery or trauma (within 4 weeks requiring hospitalization)	1
Prior PE or DVT	1
Hormone use (oral contraceptives, HRT, or estrogenic hormones)	1
Positive Criteria	/ 8

Interpretation

Score = 0	PERC Negative — If pre-test probability is ≤15%, PE is effectively ruled out. No further workup needed (sensitivity 97.4%, NPV 99.5%).
Score ≥ 1	PERC Positive — Cannot rule out PE by PERC alone. Consider D-dimer, Wells' score, or CTA based on clinical suspicion.

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CURB-65 Score for Pneumonia Severity

Estimates 30-day mortality of community-acquired pneumonia (CAP) to help determine inpatient vs. outpatient treatment.

Use in: Adult patients with confirmed or suspected community-acquired pneumonia.

CURB-65 Score

CURB-65 Calculator

Criteria	No (0)	Yes (+1)
Confusion (new disorientation in person, place, or time)	1
Uremia — BUN >19 mg/dL (>7 mmol/L)	1
Respiratory rate ≥30 breaths/min	1
Blood pressure — SBP <90 mmHg or DBP ≤60 mmHg	1
Age ≥65 years	1
CURB-65 Score	/ 5

Interpretation & Disposition

0–1	Low Risk — 1.5% 30-day mortality. Consider outpatient treatment with oral antibiotics.
2	Moderate Risk — 9.2% 30-day mortality. Consider short inpatient stay or closely monitored observation.
3–5	High Risk — 22% 30-day mortality. Inpatient admission recommended. ICU if score 4–5.

References
Lim WS et al. Defining community acquired pneumonia severity. Thorax. 2003;58(5):377-382. PMID 12728155. Mandell LA et al. IDSA/ATS consensus guidelines on CAP. Clin Infect Dis. 2007;44:S27-72. PMID 17278083.

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Vascular

Wells' Criteria for DVT

Calculates risk of DVT based on clinical criteria.

Use in: Patients with clinical suspicion for deep venous thrombosis.

Wells Score for DVT

Wells' Criteria for DVT

Criteria	No	Yes	Points
Active cancer (treatment within 6 months or palliative)	1		+1
Bedridden recently >3 days or major surgery within 12 weeks	1		+1
Calf swelling >3 cm compared to other leg (measured 10 cm below tibial tuberosity)	1		+1
Collateral superficial veins (non-varicose)	1		+1
Entire leg swollen	1		+1
Localized tenderness along deep venous system	1		+1
Pitting edema confined to symptomatic leg	1		+1
Paralysis, paresis, or recent cast immobilization of lower extremities	1		+1
Previously documented DVT	1		+1
Alternative diagnosis at least as likely as DVT	1		−2
Wells' Score	points

Interpretation (Traditional)
≤0	Low Risk — 5% prevalence of DVT. Consider D-dimer to rule out.
1–2	Moderate Risk — 17% prevalence of DVT. Consider D-dimer or ultrasound.
≥3	High Risk — 53% prevalence of DVT. Ultrasound recommended.
Interpretation (Dichotomized)
≤1	DVT Unlikely — D-dimer to rule out.
≥2	DVT Likely — Ultrasound recommended.

References
Wells PS et al. Value of assessment of pretest probability of DVT. Lancet. 1997;350:1795-1798. PMID 9428249. Wells PS et al. Evaluation of D-dimer in suspected DVT. N Engl J Med. 2003;349:1227-1235. PMID 14507948.

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Neurological

Glasgow Coma Scale (GCS)

Assesses level of consciousness based on Eye, Verbal, and Motor responses. Score range: 3–15.

Use in: Any patient requiring neurological assessment — trauma, stroke, altered mental status. Note: GCS should not be used alone for clinical management decisions.

Glasgow Coma Scale (GCS)

Glasgow Coma Scale Calculator

Component	Response	Points
Eye Opening (E)	Spontaneous	+4
	To verbal command	+3
	To pain	+2
	No eye opening	+1
Verbal Response (V)	Oriented	+5
	Confused	+4
	Inappropriate words	+3
	Incomprehensible sounds	+2
	No verbal response	+1
Motor Response (M)	Obeys commands	+6
	Localizes pain	+5
	Withdrawal from pain	+4
	Flexion to pain (decorticate)	+3
	Extension to pain (decerebrate)	+2
	No motor response	+1
GCS Score	/ 15

Interpretation

13–15	Mild brain injury
9–12	Moderate brain injury
3–8	Severe brain injury — consider intubation if unable to protect airway

References
Teasdale G, Jennett B. Assessment of coma and impaired consciousness. Lancet. 1974;2:81-84. PMID 4136544. Teasdale G et al. The Glasgow Coma Scale at 40 years. Lancet Neurol. 2014;13:844-854. PMID 25030516.

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Infectious Disease / Sepsis

qSOFA (Quick SOFA) Score for Sepsis

Identifies high-risk patients for in-hospital mortality with suspected infection outside the ICU.

Use in: Patients with suspected sepsis outside the ICU. Note: Per Sepsis-3 definitions, qSOFA ≥2 with suspected infection warrants further evaluation for organ dysfunction.

qSOFA Score

qSOFA (Quick SOFA) Score

Criteria	No (0)	Yes (+1)
Altered mental status (GCS <15)	0	1
Respiratory rate ≥22 breaths/min	0	1
Systolic BP ≤100 mmHg	0	1
qSOFA Score	0   / 3

Interpretation
0–1	Low Risk — Not high risk for in-hospital mortality. Continue standard evaluation.
≥2	High Risk — Associated with ≥10% in-hospital mortality. Consider ICU-level care, lactate, blood cultures, and broad-spectrum antibiotics.

References
Singer M et al. Sepsis-3 Definitions. JAMA. 2016;315(8):801-810. PMID 26903338. Seymour CW et al. Assessment of clinical criteria for sepsis. JAMA. 2016;315(8):762-774. PMID 26903335.

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SIRS Criteria

Defines the systemic inflammatory response syndrome.

Use in: Screening for SIRS in the setting of suspected infection. Note: SIRS + suspected infection = sepsis (per Sepsis-1/2 definitions). Sepsis-3 uses SOFA/qSOFA instead.

SIRS Criteria

SIRS Criteria

Criteria	No (0)	Yes (+1)
Temperature >38°C (100.4°F) or <36°C (96.8°F)	1
Heart rate >90 bpm	1
Respiratory rate >20 breaths/min or PaCO₂ <32 mmHg	1
WBC >12,000/mm³ or <4,000/mm³ or >10% bands	1
SIRS Criteria Met	/ 4

Interpretation
0–1	SIRS criteria NOT met — Fewer than 2 criteria present.
≥2	SIRS criteria MET — If infection is suspected or confirmed, meets criteria for sepsis (per Sepsis-1/2 definition). Note: Sepsis-3 uses qSOFA/SOFA criteria instead.

References
Bone RC et al. Definitions for sepsis and organ failure. Chest. 1992;101:1644-1655. PMID 1303622. Kaukonen KM et al. SIRS criteria in defining severe sepsis. N Engl J Med. 2015;372:1629-1638. PMID 25776936.

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ENT / Pharyngitis

Modified Centor (McIsaac) Score for Strep Pharyngitis

Estimates probability that pharyngitis is streptococcal and suggests management course.

Use in: Patients presenting with sore throat to guide testing and treatment.

Centor/McIsaac Score

Modified Centor (McIsaac) Score

Criteria	No (0)	Yes (+1)
Tonsillar exudates or swelling	0	1
Tender/swollen anterior cervical lymph nodes	0	1
Temperature >38°C (100.4°F)	0	1
Absence of cough	0	1
Age modifier (McIsaac modification)
Age 3–14 years	0	1 (+1)
Age 15–44 years	(0 points — default)
Age ≥45 years	0	-1 (−1)
Modified Centor Score	0   / 5

Interpretation & Management
≤0	~1–2.5% strep probability — No testing or antibiotics needed.
1	~5–10% strep probability — No testing or antibiotics needed (optional rapid strep if high clinical suspicion).
2–3	~11–35% strep probability — Rapid strep testing recommended; treat if positive.
4–5	~51–53% strep probability — Consider empiric antibiotics or rapid strep test.

References
Centor RM et al. The diagnosis of strep throat in adults. Med Decis Making. 1981;1:239-246. PMID 6763125. McIsaac WJ et al. A clinical score to reduce unnecessary antibiotic use. CMAJ. 1998;158:75-83. PMID 9475915.

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Orthopedic / Trauma

Ottawa Ankle Rule

Rules out clinically significant foot and ankle fractures to reduce use of x-ray imaging.

Use in: Patients presenting with ankle or midfoot pain after injury. Note: Sensitivity 96.4–99.6% for clinically significant fractures. Apply only in adults >18 years.

Ottawa Ankle Rules

Ottawa Ankle Rule

Criteria	No (0)	Yes (+1)
Ankle X-ray is required if there is pain in the malleolar zone AND any of the following:
Bone tenderness along distal 6 cm of posterior edge of tibia or tip of medial malleolus	1
Bone tenderness along distal 6 cm of posterior edge of fibula or tip of lateral malleolus	1
Inability to bear weight both immediately and in the ED (4 steps)	1
Foot X-ray is required if there is pain in the midfoot zone AND any of the following:
Bone tenderness at the base of the 5th metatarsal	1
Bone tenderness at the navicular	1
Inability to bear weight both immediately and in the ED (4 steps)	1
Positive Criteria	/ 6

Interpretation
Score = 0	No X-ray needed — Sensitivity 96.4–99.6% for clinically significant fractures.
Score ≥ 1	X-ray recommended — Ankle and/or foot x-ray indicated based on positive criteria location.

References
Stiell IG et al. A study to develop clinical decision rules for radiography in acute ankle injuries. Ann Emerg Med. 1992;21:384-390. PMID 1554175. Stiell IG et al. Decision rules for radiography in acute ankle injuries: refinement and prospective validation. JAMA. 1993;269:1127-1132. PMID 8433468.

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Ottawa Knee Rule

Rules out knee fractures to reduce unnecessary radiographs.

Use in: Patients presenting with acute knee injury. Note: Sensitivity 98.5% for knee fractures.

Ottawa Knee Rules

Ottawa Knee Rule

Criteria	No (0)	Yes (+1)
Age ≥55 years	1
Tenderness at head of fibula	1
Isolated tenderness of patella (no other knee bone tenderness)	1
Inability to flex to 90°	1
Inability to bear weight (4 steps both immediately and in ED)	1
Criteria Met	/ 5

Interpretation
0	X-ray NOT indicated — No Ottawa Knee Rule criteria met. Sensitivity 98.5% for fracture.
≥1	X-ray indicated — One or more criteria met; obtain knee radiographs to evaluate for fracture.

References
Stiell IG et al. Prospective validation of a decision rule for radiography in acute knee injuries. JAMA. 1996;275:611-615. PMID 8594242. Stiell IG et al. Implementation of the Ottawa Knee Rule. JAMA. 1997;278:2075-2079. PMID 9403421.

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Cardiac / ECG

Corrected QT Interval (QTc)

Calculates corrected QT interval using Bazett's and Fridericia's formulas.

Use in: Patients on QT-prolonging medications, those with QT prolongation, or ECG interpretation. Key threshold: QTc >500 ms = high risk for Torsades de Pointes.

Corrected QT Interval (QTc)

Corrected QT Interval (QTc)

Parameter	Value
QT Interval (ms)
Heart Rate (bpm)
RR Interval (ms) — auto-calculated from HR	ms
Results
QTc (Bazett's) — QT / √(RR in sec)	ms
QTc (Fridericia) — QT / ∛(RR in sec)	ms

Interpretation (Bazett's QTc)
<440 ms	Normal QTc for males.
<460 ms	Normal QTc for females.
440–500 ms	Borderline/Prolonged — Monitor closely. Review medications for QT-prolonging drugs.
>500 ms	Significantly prolonged — High risk for Torsades de Pointes. Discontinue offending agents. Check Mg²⁺/K⁺/Ca²⁺.

References
Bazett HC. An analysis of the time-relations of electrocardiograms. Heart. 1920;7:353-370. Fridericia LS. Duration of systole in electrocardiogram. Acta Med Scand. 1920;53:469-486. Viskin S. Long QT syndromes and torsade de pointes. Lancet. 1999;354:1625-1633. PMID 10560690.

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Gastrointestinal

Alvarado Score (MANTRELS) for Appendicitis

Predicts likelihood of appendicitis based on clinical and laboratory criteria.

Use in: Patients presenting with RLQ pain or suspected appendicitis. Note: Score ≥7 is highly suggestive of appendicitis.

Alvarado Score

Alvarado Score (MANTRELS)

Criteria	Points	No	Yes
Symptoms
Migration of pain to RLQ	+1	1
Anorexia	+1	1
Nausea/vomiting	+1	1
Signs
Tenderness in RLQ	+2	1
Rebound pain	+1	1
Elevated temperature (≥37.3°C / 99.1°F)	+1	1
Labs
Leukocytosis (WBC >10,000/μL)	+2	1
Left shift (>75% neutrophils)	+1	1
Alvarado Score	/ 10

Interpretation
0–4	Low risk — Appendicitis unlikely. Consider other diagnoses.
5–6	Equivocal — Consider CT imaging or observation with serial exams.
7–8	Probable appendicitis — Surgical consultation recommended.
9–10	Very probable appendicitis — Operative management almost certain.

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Ranson's Criteria for Pancreatitis Severity

Predicts mortality from pancreatitis using admission and 48-hour criteria.

Use in: Patients with confirmed acute pancreatitis. Note: Full score requires 48-hour labs. Cannot be calculated on admission alone.

Ranson's Criteria

Ranson's Criteria — Pancreatitis Severity

At Admission (GA-LAW)
Criteria	Points	No	Yes
Glucose >200 mg/dL (non-diabetic)	+1	1
Age >55 years	+1	1
LDH >350 IU/L	+1	1
AST >250 IU/L	+1	1
WBC >16,000/mm³	+1	1
At 48 Hours (C-HOBBS)
Calcium <8 mg/dL	+1	1
Hematocrit drop >10%	+1	1
Oxygen PaO₂ <60 mmHg	+1	1
BUN increase >5 mg/dL	+1	1
Base deficit >4 mEq/L	+1	1
Sequestered fluid >6 L estimated	+1	1
Ranson's Score	/ 11

Interpretation
Score	Predicted Mortality	Recommendation
0–2	~2%	Mild pancreatitis. Likely suitable for ward admission.
3–4	~15%	Moderate pancreatitis. Consider ICU or step-down monitoring.
5–6	~40%	Severe pancreatitis. ICU admission recommended.
≥7	~100%	Very severe. Critical illness, nearly certain mortality without intervention.

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Toxicology / Withdrawal

CIWA-Ar (Alcohol Withdrawal)

Quantifies severity of alcohol withdrawal to guide benzodiazepine therapy.

Use in: Patients with suspected or known alcohol withdrawal. Protocol: Symptom-triggered dosing: administer benzodiazepines when CIWA ≥10.

CIWA-Ar Score

CIWA-Ar Score

Category	Select Score
Nausea/Vomiting	1 None (0)   Mild nausea (1)   Intermittent nausea (4)   Constant nausea/dry heaves/vomiting (7)
Tremor (arms extended, fingers spread)	1 None (0)   Not visible, can be felt (1)   Moderate (4)   Severe (7)
Paroxysmal Sweats	1 None (0)   Barely perceptible (1)   Obvious beads of sweat (4)   Drenching sweats (7)
Anxiety	1 None (0)   Mildly anxious (1)   Moderately anxious (4)   Acute panic (7)
Agitation	1 Normal activity (0)   Somewhat restless (1)   Moderately fidgety (4)   Constantly thrashes (7)
Tactile Disturbances	1 None (0)   Mild itch/burning/numbness (1)   Moderate hallucinations (4)   Continuous hallucinations (7)
Auditory Disturbances	1 Not present (0)   Mildly harshened (1)   Moderate hallucinations (4)   Continuous hallucinations (7)
Visual Disturbances	1 Not present (0)   Mild sensitivity (1)   Moderate hallucinations (4)   Continuous hallucinations (7)
Headache/Fullness	1 Not present (0)   Very mild (1)   Moderate (4)   Extremely severe (7)
Orientation/Clouding	1 Oriented (0)   Uncertain about date (1)   Date uncertain >2 days (2)   Disoriented (4)
CIWA-Ar Total	/ 67

Interpretation
<10	Mild withdrawal — May not require pharmacotherapy. Monitor with serial CIWA assessments.
10–18	Moderate withdrawal — Consider benzodiazepine treatment (symptom-triggered protocol).
>18	Severe withdrawal — High risk for seizures/delirium tremens. Aggressive benzodiazepine dosing required. Consider ICU admission.

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Renal / Electrolytes

Anion Gap Calculator

Calculates the anion gap with albumin correction and delta-delta ratio.

Use in: Evaluation of metabolic acidosis. Mnemonic: MUDPILES for elevated AG causes.

Anion Gap

Anion Gap Calculator

Parameter	Value
Sodium (Na⁺) mEq/L
Chloride (Cl⁻) mEq/L
Bicarbonate (HCO₃⁻) mEq/L
Albumin (g/dL) — optional, for correction
Results
Anion Gap	mEq/L
Corrected AG (for albumin)	mEq/L
Delta-Delta Ratio (ΔAG / ΔHCO₃)

Interpretation
AG <12	Normal anion gap — Consider non-AG metabolic acidosis (HARDUPS mnemonic).
AG ≥12	Elevated anion gap — Consider MUDPILES: Methanol, Uremia, DKA, Propylene glycol, Isoniazid/Iron, Lactic acidosis, Ethylene glycol, Salicylates.
Delta-Delta Ratio
<1	Concurrent non-AG metabolic acidosis (mixed).
1–2	Pure anion gap metabolic acidosis.
>2	Concurrent metabolic alkalosis (or pre-existing elevated HCO₃).

References
Kraut JA, Madias NE. Serum anion gap: its uses and limitations in clinical medicine. Clin J Am Soc Nephrol. 2007;2:162-174. PMID 17699401. Fenves AZ et al. Increased anion gap metabolic acidosis as a result of 5-oxoproline (pyroglutamic acid). Proc (Bayl Univ Med Cent). 2006;19:364-367.

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FENa — Fractional Excretion of Sodium

Calculates FENa to help differentiate pre-renal vs. intrinsic renal azotemia.

Use in: Patients with oliguria or acute kidney injury. Caveat: Unreliable on diuretics — use FEUrea instead.

Fractional Excretion of Sodium (FENa)

FENa — Fractional Excretion of Sodium

Parameter	Value
Serum Sodium (mEq/L)
Serum Creatinine (mg/dL)
Urine Sodium (mEq/L)
Urine Creatinine (mg/dL)
FENa (%)	%

Interpretation (in setting of oliguria/AKI)
<1%	Pre-renal azotemia — Kidneys are sodium-avid (hypoperfusion, hypovolemia, heart failure, cirrhosis). Consider volume resuscitation.
>2%	Intrinsic renal disease — ATN, AIN, or glomerulonephritis. Kidneys unable to concentrate urine.
1–2%	Indeterminate — May be seen in early ATN or with mixed etiologies. Clinical correlation required.
Important Caveats
FENa is unreliable on diuretics — use FEUrea instead Low FENa (<1%) can be seen in contrast nephropathy, rhabdomyolysis, early obstruction Not validated in CKD patients

References
Espinel CH. The FENa test: use in the differential diagnosis of acute renal failure. JAMA. 1976;236:579-581. PMID 947239. Steiner RW. Interpreting the fractional excretion of sodium. Am J Med. 1984;77:699-702. PMID 6486145.

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Pediatrics

PECARN Pediatric Head CT Decision Rule

Identifies children at very low risk of clinically-important traumatic brain injury (ciTBI) who do not need CT.

Use in: Children with GCS ≥14 after head trauma. Note: Two separate algorithms for <2 years and ≥2 years.

PECARN Pediatric Head Injury

PECARN — Pediatric Head CT Decision Rule

Age Group	Select One
Patient Age	1 <2 years    ≥2 years

Age <2 Years — Risk Factors

Criteria	No	Yes
GCS <15 (altered mental status)	1
Palpable skull fracture	1
Occipital/parietal/temporal scalp hematoma	1
Loss of consciousness ≥5 seconds	1
Not acting normally per parent	1
Severe mechanism of injury (MVC with ejection/rollover/fatality, pedestrian/cyclist without helmet struck by motorized vehicle, fall >3 feet, head struck by high-impact object)	1
Risk Factors (<2y)	/ 6

Age ≥2 Years — Risk Factors

Criteria	No	Yes
GCS <15 (altered mental status)	1
Signs of basilar skull fracture (hemotympanum, raccoon eyes, Battle sign, CSF otorrhea/rhinorrhea)	1
Vomiting	1
Loss of consciousness	1
Severe headache	1
Severe mechanism of injury (MVC with ejection/rollover/fatality, pedestrian/cyclist without helmet struck by motorized vehicle, fall >5 feet, head struck by high-impact object)	1
Risk Factors (≥2y)	/ 6

Interpretation (for selected age group)
0	Very low risk — ciTBI risk <0.02% (<2y) or <0.05% (≥2y). CT not recommended.
1 (intermediate*)	Low risk — ciTBI risk ~0.9% (<2y) or ~0.8% (≥2y). Observation vs. CT. *Only if GCS=15 and no skull fracture/AMS. Consider observation for 4-6 hours.
GCS<15 or skull fx	High risk — ciTBI risk 4.4% (<2y) or 4.3% (≥2y). CT recommended.

References
Kuppermann N, Holmes JF, Dayan PS, et al. Identification of children at very low risk of clinically-important brain injuries after head trauma: a prospective cohort study. Lancet. 2009;374:1160-1170. PMID 19758692.

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Trauma / Burns

Parkland Formula for Burns

Estimates fluid requirements for burn resuscitation in the first 24 hours.

Use in: Patients with significant thermal burns. Key: 4 mL × weight (kg) × %TBSA. Give first half in 8 hours from time of burn.

Parkland Formula

Parkland Formula — Burn Fluid Resuscitation

Parameter	Value
Patient Weight (kg)
TBSA Burned (%)
Results (Lactated Ringer's)
Total 24-hour volume	mL
First 8 hours (½ of total)	mL
Rate for first 8 hours	mL/hr
Next 16 hours (½ of total)	mL
Rate for next 16 hours	mL/hr

Notes
Formula: 4 mL × body weight (kg) × %TBSA burned = total fluid for first 24 hours Give first half over the first 8 hours from time of burn (not from time of presentation) Give second half over the next 16 hours Use Lactated Ringer's solution Titrate to urine output: 0.5–1 mL/kg/hr in adults; 1 mL/kg/hr in children This is a starting point — adjust based on clinical response

References
Baxter CR, Shires T. Physiological response to crystalloid resuscitation of severe burns. Ann N Y Acad Sci. 1968;150:874-894. PMID 4973463. Saffle JI. The phenomenon of fluid creep in acute burn resuscitation. J Burn Care Res. 2007;28:382-395. PMID 17438489.

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Shock Index

Simple hemodynamic screening tool: Heart Rate ÷ Systolic BP.

Use in: Rapid assessment of hemodynamic compromise in trauma, sepsis, or hemorrhage. Normal: 0.5–0.7.

Shock Index

Shock Index

Parameter	Value
Heart Rate (bpm)
Systolic Blood Pressure (mmHg)
Shock Index (HR/SBP)

Interpretation
0.5–0.7	Normal — Normal physiologic range.
0.7–1.0	Elevated — May indicate early/compensated shock. Consider further evaluation.
1.0–1.4	High — Consistent with significant hemodynamic compromise. Consider aggressive resuscitation.
>1.4	Critical — High mortality risk. Immediate intervention required.

References
Allgower M, Burri C. Shock index. Dtsch Med Wochenschr. 1967;92:1947-1950. PMID 5299769. Cannon CM et al. Utility of the shock index in predicting mortality in traumatically injured patients. J Trauma. 2009;67:1426-1430. PMID 20009697.

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Disclaimer: These calculators are provided as clinical decision support tools only. They do not replace clinical judgment. Always consider the full clinical picture when making treatment decisions. Scoring systems referenced from peer-reviewed literature. See individual topic pages for complete references.