Medicine Study Notes

A focused gallery for medical notes, diagrams, handwritten study images, and clinical learning material.

Anesthesia Calculators

Search calculators by name, keyword, formula, or reference. Each calculator opens separately and has its own inputs, formula, meta title, meta description, and references.

!
For trained clinicians only. Verify all outputs with institutional protocols, patient condition, drug labels, and senior anesthesiologist judgement.

Calculator List

Tap any calculator below to open it.

CAL
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Intra-op Fluid Management

Fluid plan and maximum allowable blood loss calculator.

FL
Max Allowable Blood Loss
0 ml

Hour 1

0

Hour 2

0

Hour 3

0

Formula and calculation method

Maintenance fluid: 4-2-1 rule: first 10 kg x 4 ml/kg/hr, next 10 kg x 2 ml/kg/hr, remaining weight x 1 ml/kg/hr.

NPO deficit: maintenance rate x NPO hours minus fluid already given.

Intra-op plan: Hour 1 = half deficit + stress fluid, Hour 2 = quarter deficit + stress fluid, Hour 3 = stress fluid.

MABL: EBV x weight x (Initial Hb - Target Hb) / Initial Hb.

Formula: MABL = EBV x weight x (Hb initial - Hb target) / Hb initial.

Airway Calculator

Estimated ETT size, ETT depth, LMA and i-gel size.

AW
Airway Estimate

ETT Size

-

ETT Depth

-

i-gel

-

LMA

-

Type

-

Check

Clinical

Formula and calculation method

Pediatric ETT: cuffed ETT ID = age / 4 + 3.5 mm. Adult estimate: male 8.0 mm, female 7.5 mm.

ETT depth: pediatric oral depth = age / 2 + 12 cm. Adult estimate: male 23 cm, female 21 cm.

i-gel and LMA: selected by weight bands. Always confirm with leak, ventilation, capnography and clinical fit.

Formula: Pediatric cuffed ETT ID = age / 4 + 3.5; pediatric oral depth = age / 2 + 12.

Infusion Rate Calculator

Calculate ml/hr from dose, weight and drug concentration.

IV
Infusion Rate
0.00 ml/hr

Dose/hr

0

Conc/ml

0

Weight

0 kg

Formula and calculation method

Step 1: Weight is converted to kg if entered in pounds.

Step 2: Concentration is converted to mcg/ml, mg/ml or units/ml depending on selected dose type.

Step 3: Dose is converted to dose per hour. Weight-based doses are multiplied by patient weight.

Formula: ml/hr = total required dose per hour / concentration per ml.

Formula: infusion rate = dose per hour / concentration per ml.

Anesthesia Drug Dose

Common weight-based anesthesia drug dose list.

Rx

Formula and calculation method

Each dose is calculated as: weight x dose factor.

These are common reference ranges or typical doses, not a prescription. Adjust for age, ASA status, comorbidities, hemodynamics, renal/hepatic disease, pregnancy, frailty and institutional policy.

Formula: drug dose = patient weight in kg x selected drug dose in mg/kg or mcg/kg.

LAST Toxicity Limits

Local anesthetic maximum dose and maximum volume estimation.

LA

Formula and calculation method

Maximum dose: weight x maximum recommended mg/kg dose x risk factor.

Maximum volume: maximum mg / drug concentration in mg/ml.

Use the lowest effective dose. Toxicity may still occur below calculated maximums, especially after intravascular injection or in high-risk patients.

Formula: maximum dose = weight x mg/kg x risk factor; maximum volume = maximum mg / concentration mg/ml.

ASA Physical Status

Preoperative physical status classification.

ASA
ASA Classification
ASA I
Normal healthy patient.

Formula and calculation method

ASA Physical Status is a categorical classification based on systemic disease burden. It is not a numeric mortality prediction model.

Method: Select ASA I-VI; add E when the procedure is emergent.

Aldrete Score

PACU recovery score for discharge readiness.

PACU
Modified Aldrete Score
10 / 10
Usually acceptable for PACU discharge if local criteria are also met.

Formula and calculation method

Five domains are scored from 0 to 2: activity, respiration, circulation, consciousness and oxygen saturation.

Formula: Aldrete score = sum of five domain scores. Maximum = 10.

Apfel PONV Score

Postoperative nausea and vomiting risk prediction.

PONV
PONV Risk
0 points
Approximate risk: 10%.

Formula and calculation method

One point is assigned for each predictor: female sex, nonsmoker, history of PONV/motion sickness, and planned postoperative opioids.

Formula: Apfel score = number of positive predictors. Approximate risks: 0=10%, 1=20%, 2=40%, 3=60%, 4=80%.

STOP-BANG Score

Obstructive sleep apnea screening tool.

OSA
STOP-BANG Score
0 / 8
Low risk of OSA.

Formula and calculation method

Each positive STOP-BANG item scores 1 point.

Formula: STOP-BANG score = sum of 8 yes/no items. 0-2 low risk, 3-4 intermediate risk, 5-8 high risk.

Modified Mallampati Classification

Airway view classification.

MP
Mallampati Class
Class I
Usually easier laryngoscopic view, but not definitive alone.

Formula and calculation method

This is an anatomical classification based on visible oropharyngeal structures with mouth open and tongue protruded.

Method: Assign Class I-IV by visible structures; higher class suggests increased difficulty but must be combined with other airway assessments.

Maintenance Fluid Calculator

4-2-1 hourly and daily maintenance fluid.

MF
Maintenance Rate
110 ml/hr

Daily

2640 ml/day

First 10 kg

40

Extra

70

Formula and calculation method

Uses the 4-2-1 rule for hourly maintenance fluid requirement.

Formula: 4 ml/kg/hr for first 10 kg + 2 ml/kg/hr for next 10 kg + 1 ml/kg/hr for each kg above 20 kg.

IV Drip Rate Calculator

Manual drip rate in drops per minute.

GTT
Drip Rate
42 gtt/min

Formula and calculation method

Manual drip rate depends on total volume, infusion time and drop factor of the IV set.

Formula: gtt/min = volume ml x drop factor gtt/ml / time minutes.

Tidal Volume / PBW Calculator

Predicted body weight and lung protective tidal volume.

TV
Predicted Body Weight
66.0 kg

6 ml/kg

396 ml

7 ml/kg

462 ml

8 ml/kg

528 ml

Formula and calculation method

Predicted body weight is calculated from sex and height, then tidal volume targets are calculated in ml/kg PBW.

Formula: male PBW = 50 + 0.91 x (height cm - 152.4); female PBW = 45.5 + 0.91 x (height cm - 152.4).

RASS Sedation Scale

Richmond Agitation-Sedation Scale.

RASS
RASS Score
0
Alert and calm.

Formula and calculation method

RASS is a clinical ordinal scale from +4 to -5 based on agitation, alertness and response to voice/physical stimulation.

Method: Select the observed clinical state; no arithmetic formula is used.

Revised Cardiac Risk Index

Perioperative cardiac risk score.

RCRI
RCRI Score
0
Low risk by RCRI.

Formula and calculation method

One point is assigned for each of six predictors.

Formula: RCRI = sum of high-risk surgery, ischemic heart disease, heart failure, stroke/TIA, insulin therapy, and creatinine >2 mg/dL.

Caprini VTE Risk Score

Simplified surgical VTE risk estimation.

VTE
Caprini Score
0
Very low risk in this simplified tool.

Formula and calculation method

This simplified implementation adds points for common Caprini variables. It does not include every original Caprini item.

Formula: simplified score = sum of selected weighted risk factors. Use local surgical VTE prophylaxis policy.
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