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 from the oropharyngeal view. Class III/IV indicates a potentially difficult airway. Assess with the patient seated, mouth fully open and tongue maximally protruded, without 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. ARDS also needs onset within 1 week, bilateral opacities not fully explained by effusion, collapse or nodules, respiratory failure not fully explained by cardiac failure or fluid overload, and PEEP/CPAP ≥ 5 cmH₂O — the ratio alone does not diagnose ARDS.
- 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): 17 variables (worst values in the first 24 h of ICU) predicting hospital mortality. 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 DischargeModified Aldrete score (Aldrete 1995 — SpO₂ in place of colour): readiness for discharge from the post-anaesthesia care unit (PACU / recovery room). A score ≥ 9 is required for discharge.
- 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 (adults). Children: use a children's formulary.
- NUTRIC Score for ICU Nutrition RiskModified NUTRIC score (mNUTRIC — without IL-6; Rahman 2016) identifies ICU patients who benefit most from aggressive nutritional therapy. Range 0–9; 5 or more = high nutrition risk.
- 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 the severity of acute lung injury / ARDS from 4 parameters (Murray 1988). A score above 3.0 despite optimal conventional management was the CESAR criterion for referral to an ECMO centre.
- 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 CalculatorVancomycin dosing guidance: dosing is AUC-guided (target AUC 400–600 mg·h/L, ASHP/IDSA/PIDS/SIDP 2020). Information page — no dose is calculated.
- 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 FailureAdjusts a measured total phenytoin level for hypoalbuminaemia and end-stage renal disease, giving the equivalent total level at normal albumin (therapeutic range 10–20 mg/L). A measured free phenytoin level is preferred where available.
- Local Anaesthetic Maximum Dose CalculatorCalculates the maximum recommended single dose of common local anaesthetics for adults, to help prevent local anaesthetic 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: TISS-28 scores 28 therapeutic interventions over 24 hours (0–78). One point ≈ 10.6 minutes of nursing time; one nurse can deliver about 46 points per shift (Miranda 1996).
- PICU Delirium Assessment (pCAM-ICU)Paediatric adaptation of CAM-ICU (Smith 2011) for delirium in critically ill children ≥ 5 years, ventilated or not, who respond to voice (RASS −3 or above). 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. NEWS2 adds SpO₂ Scale 2 for hypercapnic respiratory failure (not included in this calculator). 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. A MEWS of 5 or more was associated with increased risk of death and of ICU or HDU admission (Subbe 2001).
- 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)Surgical Outcome Risk Tool: predicts 30-day mortality after inpatient non-cardiac surgery from six pre-operative variables (ASA grade, NCEPOD urgency, high-risk specialty, surgical severity, cancer, age). Derived from the NCEPOD 'Knowing the Risk' cohort.
- Logistic Organ Dysfunction Score (LODS)Logistic Organ Dysfunction score for ICU patients: 6 organ systems (neurologic, cardiovascular, renal, pulmonary, haematologic, hepatic), worst values in the first 24 hours of ICU admission, each organ scored by its most severe variable. Total 0–22; converts to predicted hospital mortality.
- Lung-Protective Tidal Volume (ARDSNet Predicted Body Weight)Calculates 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)SAPS 3 admission score from data within 1 hour of ICU admission (Box I: before admission; Box II: circumstances of admission; Box III: physiology). Predicts hospital mortality.
- Mallampati Score (Airway Assessment)Classifies oropharyngeal visibility (modified Mallampati, Samsoon & Young) to predict difficult intubation. Class III–IV is associated with difficult laryngoscopy. Mallampati alone has limited accuracy — combine it with other predictors (mouth opening, thyromental distance, neck movement, BMI; see the El-Ganzouri risk index).
- 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. Levels 2–3 are a common target for most ICU patients; levels 4–6 indicate deeper 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 × (adrenaline + noradrenaline) + 10 × milrinone + 10 000 × vasopressin (µg/kg/min; vasopressin in units/kg/min). Enter 0 for drugs not running. A high maximum VIS after infant 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.