Anaesthesia & Critical Care Calculators
45 calculators & risk scores
Browse 45 Anaesthesia & Critical Care clinical calculators and risk scores used in everyday UK practice. Every tool runs entirely in your browser — enter the values and get instant scoring, colour-coded interpretation bands and a link to the underlying guideline or publication. ClinCalc Pro is free, needs no sign-up, and is built for working clinicians.
These anaesthesia & critical care tools span Airway Assessment, ICU Scoring, Sedation Assessment, Delirium Assessment, Respiratory Assessment, Sepsis / Organ Failure and more.
- Modified Mallampati ClassificationPredicts difficult laryngoscopy and intubation based on oropharyngeal visualisation. Class III/IV indicates potentially difficult airway. Assess with mouth fully open, tongue not protruded, no phonation.
- APACHE II ScoreAcute Physiology and Chronic Health Evaluation II. 14-parameter score predicting ICU mortality from acute physiology (12 variables), age, and chronic health points. Range 0–71.
- Richmond Agitation-Sedation Scale (RASS)Standardised sedation and agitation scale for ICU patients. Range −5 (unarousable) to +4 (combative). Used to titrate sedation and assess readiness for awakening trials. Target RASS 0 to −2 for most ventilated patients.
- Confusion Assessment Method for ICU (CAM-ICU)Validated delirium assessment for ICU patients. CAM-ICU is POSITIVE if Feature 1 AND Feature 2 are present, PLUS Feature 3 OR Feature 4. Only assess if RASS ≥ −3 (not deeply sedated).
- P/F Ratio (Horowitz Index)PaO₂/FiO₂ ratio. Quantifies oxygenation efficiency and is the cornerstone of the Berlin ARDS Definition. Normal >400. Enter PaO₂ from ABG and FiO₂ as a percentage.
- Sequential Organ Failure Assessment (SOFA) ScoreQuantifies degree of organ failure in ICU patients across 6 organ systems. Used for sepsis definition (Sepsis-3) and predicts ICU mortality. Scores each system 0–4.
- SAPS II ScoreSimplified Acute Physiology Score II (SAPS II) predicts ICU mortality using 17 variables collected within 24h of admission. Widely used in European ICUs.
- ASA Physical Status ClassificationAmerican Society of Anesthesiologists (ASA) physical status classification grades peri-operative risk based on patient's overall health. Used for all anaesthetic risk assessments.
- Aldrete Score for Post-Anaesthesia DischargeAssesses readiness for discharge from the post-anaesthesia care unit (PACU / recovery room). Score ≥ 9 generally indicates fitness for discharge to ward.
- Parkland Formula for Burns Fluid ResuscitationCalculates the volume of IV fluid (Hartmann's/Ringer's lactate) required in the first 24 hours of a major burn. Half given in the first 8h post-burn; remainder over next 16h.
- Morphine Milligram Equivalents (MME) CalculatorConverts opioid doses to morphine milligram equivalents (MME) to assess total opioid burden, guide dose adjustments, and identify high-risk prescribing. Daily MME ≥ 90 mg/day associated with overdose risk.
- NUTRIC Score for ICU Nutrition RiskNutrition Risk in the Critically Ill (NUTRIC) score identifies ICU patients who benefit most from aggressive nutritional therapy. High NUTRIC = poor prognosis that may be modified by optimal nutrition.
- Ramsay Sedation ScaleAssesses sedation depth in mechanically ventilated ICU patients on a 6-point scale. Predecessor to RASS. Target level typically 2–3 for most ICU patients.
- Murray Score for Acute Lung Injury (ALI/ARDS)Quantifies severity of acute lung injury / ARDS using 4 parameters. Also used to define criteria for ECMO referral (Murray score ≥ 3 despite optimal ventilation).
- SIRS, Sepsis & Septic Shock CriteriaSystemic Inflammatory Response Syndrome (SIRS) criteria and Sepsis-3 definitions. SIRS ≥ 2 criteria; Sepsis = life-threatening organ dysfunction caused by dysregulated response to infection.
- Opioid Conversion / Equianalgesic GuideGuides conversion between opioid analgesics using oral morphine equivalents (OME). Start at 50–75% of calculated equianalgesic dose due to incomplete cross-tolerance.
- Vancomycin Dosing CalculatorCalculates initial vancomycin dose based on weight and renal function. Target AUC/MIC 400–600 mg·h/L (ASHP/IDSA 2020 guidelines).
- Numeric Rating Scale (NRS) for Pain11-point numeric scale (0–10) for pain intensity. Validated across clinical settings. Single-item self-report tool.
- Phenytoin Correction for Albumin / Renal FailureCorrects total phenytoin level for hypoalbuminaemia and/or renal failure to estimate free (active) phenytoin concentration. Therapeutic range for free phenytoin: 1–2 mg/L.
- Local Anaesthetic Maximum Dose CalculatorCalculates maximum safe dose of common local anaesthetics to prevent systemic toxicity (LAST).
- National Early Warning Score 2 (NEWS2) for SepsisNEWS2 is the UK standard early warning score endorsed by NICE for sepsis screening. Triggers escalation based on physiological parameters. Replaced NEWS1 in 2017.
- TISS-28 — Therapeutic Intervention Scoring SystemMeasures ICU nursing workload and patient acuity. TISS-28 is a simplified 28-item version. Score reflects interventions required in 24 hours.
- PICU Delirium Assessment (pCAM-ICU)Paediatric adaptation of CAM-ICU for delirium assessment in mechanically ventilated children ≥5 years. Positive if Features 1+2 AND (3 or 4).
- qSOFA (Quick SOFA) Score for Sepsis ScreeningRapid 3-variable bedside tool for identifying patients with suspected infection at risk of poor outcomes consistent with sepsis (Sepsis-3 criteria). Score of >= 2 warrants further assessment.
- Warfarin Dose Adjustment CalculatorGuides warfarin dose adjustment based on current INR versus target INR range. Commonly used in ICU and inpatient settings for warfarin bridging and management.
- Multiple Organ Dysfunction Score (MODS)Quantifies the degree of dysfunction in 6 organ systems: respiratory, renal, hepatic, cardiovascular, haematological, and neurological. Predicts ICU mortality. Complements SOFA score.
- National Early Warning Score 2 (NEWS2)Updated Royal College of Physicians early warning score for detecting clinical deterioration in adults. Adds new SpO2 Scale 2 for hypercapnic respiratory failure. Score triggers escalation thresholds. Endorsed by NHS England.
- Modified Early Warning Score (MEWS)5-parameter early warning score for detecting clinical deterioration in hospitalised adults. Precursor to NEWS. Score ≥5 = requires urgent review; score ≥4 = consider ICU/HDU transfer.
- POSSUM Score for Surgical Morbidity and MortalityPhysiological and Operative Severity Score for the enUmeration of Mortality and morbidity (POSSUM). Uses 12 physiological and 6 operative variables to predict 30-day morbidity and mortality. P-POSSUM is modified for mortality prediction.
- SORT (Surgical Outcome Risk Tool)6-variable perioperative mortality risk tool developed in UK. Predicts 30-day mortality after inpatient surgery. Validated across 100,000+ surgical cases (NELA database). More parsimonious than POSSUM.
- Logistic Organ Dysfunction Score (LODS)7-organ-system dysfunction score for ICU patients. Based on worst values in the first 24 hours of ICU admission. Weighted for severity. Maximum score 22. Used for mortality prediction and benchmarking.
- Endotracheal Tube Depth and Tidal Volume CalculatorCalculates recommended endotracheal tube depth and initial tidal volume based on patient height. Prevents endobronchial intubation and ventilator-induced lung injury (VILI). Based on ARDSNet and standard anatomical guidelines.
- Simplified Acute Physiology Score 3 (SAPS 3)Updated SAPS score using data from time of ICU admission (Box I: pre-hospital; Box II: admission circumstances; Box III: physiology). Predicts ICU and hospital mortality. Validated internationally. Calibrated for current intensive care practice.
- Mallampati Score (Airway Assessment)Classifies oropharyngeal visibility to predict difficult intubation. Class III-IV associated with difficult laryngoscopy.
- Train-of-Four (TOF) Neuromuscular MonitoringInterprets Train-of-Four ratio to assess depth of neuromuscular blockade and guide reversal of non-depolarising muscle relaxants.
- Apfel Score (Post-operative Nausea and Vomiting)Predicts risk of post-operative nausea and vomiting (PONV). Guides prophylactic antiemetic strategy.
- Revised Cardiac Risk Index (RCRI / Lee Index)Predicts perioperative major adverse cardiac events (MACE) for non-cardiac surgery. Guides preoperative optimisation and monitoring.
- Difficult Airway Prediction Score (El-Ganzouri)Multi-variate risk score combining seven airway predictors for difficult laryngoscopy and intubation.
- ASA Physical Status ClassificationAmerican Society of Anesthesiologists (ASA) physical status classification for perioperative risk. Guides anaesthetic planning and consent.
- Ramsay Sedation ScaleAssesses sedation depth in ICU and procedural settings. Level 2-3 is optimal for most ICU patients; level 5-6 indicates deep sedation.
- RSBI (Rapid Shallow Breathing Index) — Weaning ReadinessRapid Shallow Breathing Index (f/Vt) predicts successful extubation. RSBI <105 associated with successful weaning. Used with SBT and clinical readiness assessment.
- Vasoactive-Inotropic Score (VIS)Composite measure of inotropic / vasoactive drug support (Gaies 2010). VIS = dopamine + dobutamine + 100×(epi + norepi) + 10×milrinone + 10000×vasopressin + 100×isoproterenol (all µg/kg/min, vasopressin in U/kg/min). High VIS in first 48 h post-cardiac surgery predicts mortality and morbidity.
- Critical-Care Pain Observation Tool (CPOT)Behavioural pain assessment for non-verbal, ventilated adults (Gélinas 2006). Four behavioural domains, each 0–2. Total 0–8.
- Behavioral Pain Scale (BPS) for Ventilated PatientsThree-domain pain assessment for sedated, intubated adults (Payen 2001). Each domain scored 1–4. Total 3–12. Score >5 indicates unacceptable pain.
- Riker Sedation-Agitation Scale (SAS)Single 7-point clinical score of sedation–agitation in adult ICU patients (Riker 1999). Target SAS 3–4 typical for routine sedation.