Lessons · Medicine foundations · Quick reference
Medicine foundations quick reference
36 topics, one line each, in the order Hone teaches them.
Hone is a place to practise a career, one idea a day. This sheet is the whole Medicine foundations track at a glance: every idea it covers, in the order they are taught, one line each. It is a map rather than a lesson. Read opens the full explanation of an idea; Practise gives you a question on it. Both are free, and reading needs no account at all.
From a unit to a physiology you can calculate · Units and the body's numbers
mmol/L and mg/dLOne laboratory prints a result in millimoles per litre and another prints the same result in milligrams per decilitre; a single factor, given to you, turns either one into the other. Read: The same blood, two units: mmol/L and mg/dL · Practise mmol/L and mg/dL
pounds to kilograms, feet and inches to centimetresAlmost every formula in this track wants kilograms and centimetres, so the first line of the working is usually just the conversion. Read: Pounds to kilograms, feet and inches to centimetres · Practise pounds to kilograms, feet and inches to centimetres
body mass indexBody mass index is the weight in kilograms divided by the height in metres, squared. Read: Body mass index: kilograms over metres squared · Practise body mass index
body surface areaThe Mosteller formula gives body surface area in square metres as the square root of the height in centimetres times the weight in kilograms, divided by 3600. Read: Body surface area: one square root, in centimetres and kilograms · Practise body surface area
Fahrenheit to CelsiusCelsius is the Fahrenheit reading minus 32, multiplied by five ninths; going back is nine fifths, then add 32. Read: Fahrenheit to Celsius: subtract, then five ninths · Practise Fahrenheit to Celsius
a reference range, and what within it meansA reference range is a lower limit and an upper limit, both given to you; a value is within the range when it sits at or between them, and how far outside it is, if it is, is a subtraction. Read: A reference range is two numbers and a rule · Practise a reference range, and what within it means
From a unit to a physiology you can calculate · The heart and the vessels
heart rate from a rhythm stripOn standard paper the rate is 300 divided by the number of large squares between two beats, or 1500 divided by the number of small squares. Read: Heart rate off a rhythm strip: 300 over the large squares · Practise heart rate from a rhythm strip
pulse pressure and mean arterial pressurePulse pressure is the systolic minus the diastolic; mean arterial pressure is the diastolic plus one third of that pulse pressure. Read: Two numbers on a cuff, and the two figures you take from them · Practise pulse pressure and mean arterial pressure
cardiac outputCardiac output is the volume pushed out by one beat times the number of beats in a minute: stroke volume × heart rate. Read: Cardiac output: how much blood the heart moves in a minute · Practise cardiac output
ejection fractionEjection fraction is the stroke volume divided by the volume in the ventricle at the end of filling, written as a percentage. Read: Ejection fraction: the share of a full ventricle that leaves · Practise ejection fraction
blood volume from body weightCirculating blood volume is estimated as a given number of millilitres per kilogram of body weight, so working it out is one multiplication. Read: Blood volume: a set number of millilitres for every kilogram · Practise blood volume from body weight
From a unit to a physiology you can calculate · The lungs and the kidneys
minute ventilationMinute ventilation is the tidal volume, the air moved in a single breath, multiplied by the respiratory rate. Read: Minute ventilation: one breath, times the breaths in a minute · Practise minute ventilation
dead space and alveolar ventilationPart of every breath never reaches the gas-exchanging part of the lung, so the ventilation that counts is (tidal volume minus dead space) times the rate. Read: Dead space: the part of every breath that does no work · Practise dead space and alveolar ventilation
creatinine clearance by Cockcroft-GaultCreatinine clearance is estimated as (140 minus the age) times the weight in kilograms, divided by 72 times the serum creatinine in mg/dL, and then multiplied by a further factor of 0.85 where the problem says to apply it. Read: Cockcroft-Gault: an equation you substitute into · Practise creatinine clearance by Cockcroft-Gault
urine output in mL per kg per hourUrine output is compared per kilogram of body weight and per hour, so a volume collected over a stretch of time is divided twice: once by the hours, once by the weight. Read: Urine output: millilitres per kilogram per hour · Practise urine output in mL per kg per hour
the anion gapThe anion gap is the sodium minus the sum of the chloride and the bicarbonate, all in millimoles per litre. Read: The anion gap: what the measured ions do not account for · Practise the anion gap
maintenance fluid by the 4-2-1 rulePer hour, the rule gives 4 mL per kilogram for the first 10 kg of body weight, 2 mL per kilogram for the next 10 kg, and 1 mL per kilogram for every kilogram beyond 20, added together. Read: The 4-2-1 rule: maintenance fluid in three slices · Practise maintenance fluid by the 4-2-1 rule
From a unit to a physiology you can calculate · Cells, genes and statistics
dilutions and counting cellsA dilution factor is the total number of parts divided by the parts of sample; a count in a known volume becomes cells per microlitre by dividing by that volume, and the dilution is then undone by multiplying back. Read: Dilutions, and turning a count into a concentration · Practise dilutions and counting cells
the Punnett square and Mendelian fractionsPut one parent's two alleles along the top and the other parent's down the side, fill the four boxes, and every fraction the question wants is a count of boxes out of four. Read: The Punnett square: four boxes, and the fractions fall out · Practise the Punnett square and Mendelian fractions
the Hardy-Weinberg equationIf p and q are the frequencies of the two forms of a gene, then p + q = 1 and p² + 2pq + q² = 1, where p² and q² are the two homozygous groups and 2pq is the heterozygotes. Read: Hardy-Weinberg: two frequencies that add up to one · Practise the Hardy-Weinberg equation
sensitivity and specificitySensitivity is the share of people who have the condition that the test calls positive, TP / (TP + FN); specificity is the share of people who do not have it that the test calls negative, TN / (TN + FP). Read: Sensitivity and specificity: two columns of one table · Practise sensitivity and specificity
positive predictive valuePositive predictive value is the share of positive results that turn out to be right: TP / (TP + FP). It reads across the row of positive results, not down a column. Read: Positive predictive value: what a positive result is worth here · Practise positive predictive value
absolute risk, relative risk and number needed to treatThe absolute risk reduction is one group's event rate minus the other's; the number needed to treat is one divided by that difference; the relative risk is one rate divided by the other. Read: Absolute risk, relative risk, and how many people · Practise absolute risk, relative risk and number needed to treat
From a unit to a physiology you can calculate · Pharmacology arithmetic
half-life, and what is left after n of themAfter each half-life half of what was there is gone, so after n half-lives the fraction remaining is one half to the power n. Read: Half-life: halve it, and halve it again · Practise half-life, and what is left after n of them
the loading doseA loading dose is the volume of distribution multiplied by the target concentration, both of them given by the problem. Read: The loading dose: fill the space first · Practise the loading dose
the maintenance rateAt steady state the rate going in equals the rate coming out, so the maintenance rate is the clearance multiplied by the target concentration. Read: The maintenance rate: replace exactly what is cleared · Practise the maintenance rate
a dose in mg per kilogramMilligrams per kilogram becomes milligrams by multiplying by the weight in kilograms; a daily figure split into equal parts is then divided by how many parts. Read: A figure written per kilogram is one multiplication · Practise a dose in mg per kilogram
an infusion in mL per hourMultiply by the weight to get micrograms a minute, by 60 to get micrograms an hour, then divide by the concentration in micrograms per millilitre to get millilitres an hour. Read: From micrograms per kilogram per minute to millilitres per hour · Practise an infusion in mL per hour
bioavailability as a fractionBioavailability F is the share of an oral amount that reaches the bloodstream; the amount absorbed is the amount taken times F, and the oral amount matching an intravenous one is the intravenous amount divided by F. Read: Bioavailability: the fraction that actually gets in · Practise bioavailability as a fraction
From a unit to a physiology you can calculate · Procedures in order
hand hygiene, in orderWet, soap, rub every surface in turn, rinse, dry with a single-use towel, and turn the tap off with that towel. Read: Hand hygiene: the order is the technique · Practise hand hygiene, in order
putting on sterile glovesThe rule underneath every step is one sentence: a bare hand only ever touches the inside of a glove, and a gloved hand only ever touches the outside. Read: Putting on sterile gloves without touching the outside · Practise putting on sterile gloves
a vital-signs round, in orderHand hygiene and an introduction, then temperature, pulse, respirations, blood pressure, oxygen saturation, and finally every value written down with its unit and the time. Read: A vital-signs round, in the order it is done · Practise a vital-signs round, in order
the ABCDE primary surveyAirway, Breathing, Circulation, Disability, Exposure: five letters that fix the order in which a person is assessed, so the order is never decided in the moment. Read: ABCDE: an order of looking, agreed in advance · Practise the ABCDE primary survey
taking a history in the standard orderPresenting complaint, then the history of that complaint, then past medical history, then drugs, then allergies, then family history, then social history. Read: A history in the standard order · Practise taking a history in the standard order
SBAR, and the handoverSituation, Background, Assessment, Recommendation: four headings that put a spoken handover in an order the listener is expecting. Read: SBAR: a handover in four letters · Practise SBAR, and the handover
consent before a procedureConfirm who they are, check they can make this decision, explain what is involved, then the benefits, the risks and the alternatives including doing nothing, answer questions, ask for the decision, and record it. Read: Consent before a procedure, as a sequence · Practise consent before a procedure