ICU Medicine
ICU Medicine
This is a collection of definitions that I considered to be essential knowledge for the CICM basic sciences primary exam. It is not intended to be an exhaustive list but if you think there are definitions that should be included, please send them this way.
Define and conquer!
| afterload | Myocardial wall tension during systole. Alternatively, resistance to the ejection of stroke volume. |
| vitamin | Organic substance required in the diet in small amounts for normal health and is not an energy substrate. |
| mineral | Inorganic substance required in the diet in small amounts for normal health. |
| preload | Average myocardial sarcomere length at onset of systole. Approximates with end diastolic volume. |
| myocardial contractility | Intrinsic ability of the heart to contract and generate systolic pressure independent of preload and afterload. |
| pathogenicity | Tendency of an organism to cause disease. |
| pathogen | Organism that causes disease. |
| virulence | Severity of disease caused by a pathogen. |
| commensal | Organism that colonises a host without causing disease. |
| essential fatty acid | Fat/ oil required in the diet in small amounts for normal health. Differs from vitamins in that EFAs may be used as energy substrate. |
| closing capacity | Largest lung volume at which there is some degree of airway collapse in the dependent regions. |
| functional residual capacity (FRC) | Volume of gas in the lungs at the end of expiration in normal tidal breathing. 30ml/kg. |
| Huffner constant | Haemoglobin capacity for oxygen. Maximal volume of oxygen that can be held by a mass of haemoglobin. Value = 1.39 mls/g theoretical maximum and 1.34 mls/g allowing for physiological amounts of methaemoglobin and carboxyhaemoglobin. |
| hypoxia | Low oxygen delivery. |
| hypoxaemia | Low oxygen content in arterial blood. |
| re-feeding syndrome | Potentially fatal shifts in electrolytes and fluids associated with the reinstatement of nutrition in a malnourished person. |
| pain | Unpleasant sensory and emotional experience associated with actual or potential tissue damage. |
| buffer | Solution containing either weak acids, weak bases or both that tend to limit changes in hydrogen ion concentration when further acid or base is added to the solution. |
| saturated vapour pressure | Pressure exerted by a vapor in equilibrium with its liquid state for a given temperature. |
| Fick principle | Blood flow is equal to uptake / production of an indicator by an organ divided by the arteriovenous concentration difference. |
| opioid | Substance exogenous or endogenous that exerts morphine like properties via the opioid receptors and antagonised by naloxone. |
| opiate | Endogenous non-peptide opioid. |
| acid (Bronsted-Lowry) | Proton donating molecule. |
| acid (Lewis) | Electron pair accepting molecule. |
| acid (Arrhenius) | Molecule that tends to decrease pH when in solution with water. |
| pKa | Negative logarithm of the acid dissociation constant for an acid or base. |
| drug | Substance which, when administered, alters body function. |
| ion trapping | The phenomenon where weak acids tend to ionise and accumulate in alkali fluid compartments and vice versa. |
| volume of distribution | Theoretical volume into which a drug would need to be dissolved to give the plasma concentration. |
| clearance | Volume of plasma cleared of a substance per unit time. |
| bioassay | A test to compare the relative potency of two drug preparations. |
| potency | Inverse drug dose required to achieve an effect. |
| blood pressure | Force per unit area exerted on the vascular tree by its contents. |
| boiling point | Temperature at which a liquid's saturated vapour pressure equals the surrounding atmospheric pressure. |
| absolute humidity | Mass of water per unit volume of a gas. Usually expressed as mg/l or g/m3. |
| relative humidity | Ratio of absolute humidity to humidity at saturation for a given temperature and pressure. |
| viscosity | The resistance of a fluid to flow. On a mathematical level it is the ratio of shear force to shear rate. |
| vapour | Substance in a gas-like state below its critical temperature. Example: nitrous oxide at room temperature. |
| triple point | Temperature at which a substance can exist as solid, liquid and vapour. |
| saturated vapour pressure | Pressure exerted by a saturated vapour, ie where it is in equilibrium with its liquid state. |
| Lambert Law | Intensity of light transmitted through a solution decreases exponentially with the length of path. |
| Beer Law | Intensity of light transmitted through a solution decreases exponentially with the concentration of solution. |
| Fourier analysis | Mathematical separation of a complex waveform into simple constituent sine waves. |
| natural frequency | Oscillations per unit time of unforced vibration in a system. Abbreviated to Fn. |
| resonant frequency | Oscillations per time of forcing vibration that generates the greatest amplitude of vibration in a system. Equates to natural frequency in most systems. |
| damping | Tendency for the amplitude of vibration in a system to decay over time. |
| fundamental frequency | The lowest resonant frequency of a system. Also known as the first harmonic. Abbreviated to F0. |
| critical temperature | Temperature at which a substance cannot be converted from a vapor into a liquid by increases in pressure. |
| gas | Substance above its critical temperature. |
| absolute pressure | True force per unit area exerted by a substance on its container. |
| gauge pressure | Pressure difference to atmospheric pressure. |
| adhesion | Attraction between molecules of different substance. |
| cohesion | Attraction between molecules of the same substance. |
| Doppler effect | Apparent change in frequency of wave when there is relative movement of the source towards or away from the observer. |
| variable | Value based on empirical measurement. |
| parameter | Value based on assumptions about the distribution of data. |
| parametric methods | Statistical analysis based on assumptions about the distribution of data. |
| non-parametric methods | Direct statistical analysis on empirical data without assumptions about the distribution of data. Otherwise known as rank tests. |
| type 1 error | Incorrectly rejecting the null hypothesis. (Finding a difference between two populations where none actually exists.) |
| type 2 error | Incorrectly accepting the null hypothesis. (Failing to find a difference between two populations where one does exist.) |
| null hypothesis | The assumption that there is no difference between populations. |
| statistical power | The probability that a study will correctly reject the null hypothesis. Equal to 1 − β. Usually 80%. |
