Anaesthesia & Critical Care Calculators

Predicts 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.

Acute 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.

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.

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).

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.

Quantifies 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.

Simplified Acute Physiology Score II (SAPS II) predicts ICU mortality using 17 variables collected within 24h of admission. Widely used in European ICUs.

American Society of Anesthesiologists (ASA) physical status classification grades peri-operative risk based on patient's overall health. Used for all anaesthetic risk assessments.

Assesses readiness for discharge from the post-anaesthesia care unit (PACU / recovery room). Score ≥ 9 generally indicates fitness for discharge to ward.

Calculates 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.

Converts 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.

Nutrition 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.

Assesses sedation depth in mechanically ventilated ICU patients on a 6-point scale. Predecessor to RASS. Target level typically 2–3 for most ICU patients.

Quantifies severity of acute lung injury / ARDS using 4 parameters. Also used to define criteria for ECMO referral (Murray score ≥ 3 despite optimal ventilation).

Systemic Inflammatory Response Syndrome (SIRS) criteria and Sepsis-3 definitions. SIRS ≥ 2 criteria; Sepsis = life-threatening organ dysfunction caused by dysregulated response to infection.

Guides conversion between opioid analgesics using oral morphine equivalents (OME). Start at 50–75% of calculated equianalgesic dose due to incomplete cross-tolerance.

Calculates initial vancomycin dose based on weight and renal function. Target AUC/MIC 400–600 mg·h/L (ASHP/IDSA 2020 guidelines).

11-point numeric scale (0–10) for pain intensity. Validated across clinical settings. Single-item self-report tool.

Corrects total phenytoin level for hypoalbuminaemia and/or renal failure to estimate free (active) phenytoin concentration. Therapeutic range for free phenytoin: 1–2 mg/L.

Calculates maximum safe dose of common local anaesthetics to prevent systemic toxicity (LAST).

NEWS2 is the UK standard early warning score endorsed by NICE for sepsis screening. Triggers escalation based on physiological parameters. Replaced NEWS1 in 2017.

Measures ICU nursing workload and patient acuity. TISS-28 is a simplified 28-item version. Score reflects interventions required in 24 hours.

Paediatric adaptation of CAM-ICU for delirium assessment in mechanically ventilated children ≥5 years. Positive if Features 1+2 AND (3 or 4).

Rapid 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.

Guides warfarin dose adjustment based on current INR versus target INR range. Commonly used in ICU and inpatient settings for warfarin bridging and management.

Quantifies the degree of dysfunction in 6 organ systems: respiratory, renal, hepatic, cardiovascular, haematological, and neurological. Predicts ICU mortality. Complements SOFA score.

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.

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.

Physiological 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.

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.

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.

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.

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.

Classifies oropharyngeal visibility to predict difficult intubation. Class III-IV associated with difficult laryngoscopy.

Interprets Train-of-Four ratio to assess depth of neuromuscular blockade and guide reversal of non-depolarising muscle relaxants.

Predicts risk of post-operative nausea and vomiting (PONV). Guides prophylactic antiemetic strategy.

Predicts perioperative major adverse cardiac events (MACE) for non-cardiac surgery. Guides preoperative optimisation and monitoring.

Multi-variate risk score combining seven airway predictors for difficult laryngoscopy and intubation.

American Society of Anesthesiologists (ASA) physical status classification for perioperative risk. Guides anaesthetic planning and consent.

Assesses sedation depth in ICU and procedural settings. Level 2-3 is optimal for most ICU patients; level 5-6 indicates deep sedation.

Rapid Shallow Breathing Index (f/Vt) predicts successful extubation. RSBI <105 associated with successful weaning. Used with SBT and clinical readiness assessment.