| paradoxical sleep | A deep sleep, with a brain wave pattern more like that of waking states than of other states of sleep, which occurs during rapid eye movement sleep. (05 Mar 2000) |
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| paradoxical triceps reflex | Flexion of the forearm caused by tapping the olecranon. Synonym: paradoxical triceps reflex. (05 Mar 2000) |
| reversed paradoxical pulse | A pulse in which the amplitude increases with inspiration and decreases with expiration, as observed in some cases of tricuspid insufficiency and during A-V dissociation with sinus arrhythmia. (05 Mar 2000) |
| Hunt's paradoxical phenomenon | In dystonia musculorum deformans, if an attempt is made at plantar flexion of the foot when the foot is in dorsal spasm the only response is an increase of the extensor, or dorsal, spasm; if, however, the patient is told to extend the foot which is already in a state of strong dorsal flexion, there will be a sudden movement of plantar flexion; the same phenomenon, mutatis mutandis, is observed when there is a condition of strong plantar flexion. (05 Mar 2000) |
| embolism, paradoxical | Passage of a clot (thrombus) from a vein to an artery. When clots in veins break off (embolise) , they travel first to the right side of the heart and, normally, then to the lungs where they lodge. The lungs act as a filter to prevent the clots from entering the arterial circulation. However, when there is a hole in the wall between the two upper chambers of the heart (an atrial septal defect), a clot can cross from the right to the left side of the heart, then pass into the arteries as a paradoxical embolism. Once in the arterial circulation, a clot can travel to the brain, block a vessel there, and cause a stroke (cerebrovascular accident). Because of the risk of stroke from paradoxical embolism, it is usually recommended that even small atrial septal defects be repaired. Also called crossed embolism. (12 Dec 1998) |
| Kussmaul's paradoxical pulse | An exaggeration of the normal variation in the pulse volume with respiration, becoming weaker with inspiration and stronger with expiration; characteristic of cardiac tamponade, rare in constrictive pericarditis; so called because these changes are independent of changes in the cardiac rate as measured directly or by electrocardiogram. Synonym: pulsus paradoxus, pulsus respiratione intermittens. (05 Mar 2000) |
| accelerated reaction | A response occurring in a shorter time than expected; the cutaneous manifestations occurring during the period between the second and tenth day following smallpox vaccination; because it is intermediate between a primary reaction and an immediate reaction, it is regarded as evidence of some degree of resistance. Synonym: vaccinoid reaction. (05 Mar 2000) |
| acid reaction | Any test by which an acid reaction is recognised such as the change of blue litmus paper to red, an excess of hydrogen ions over hydroxide ions in aqueous solution indicated by a pH value less than 7 (at 22캜). Compare: dissociation constant of water. (05 Mar 2000) |
| acute-phase reaction | <immunology, rheumatology> Refers to the changes in synthesis of certain proteins within the serum during an inflammatory response, which provides rapid protection for the host against microorganisms via non-specific defense mechanisms. It consists of fever, an increase in inflammatory humoral factors, and an increased synthesis by hepatocytes of a number of proteins or glycoproteins usually found in the plasma; the reaction is mediated by endogenous pyrogens, the hypothalamus, adrenal hormones, and other factors. (12 Jul 2000) |
| acute situational reaction | An acute emotional reaction related to extreme environmental stress. Synonym: acute situational reaction. (05 Mar 2000) |
| acute stress reaction | A sudden bout of anxiety that is often accompanied by the features of hyperventilation (tingling around mouth and in fingertips, rapid breathing, faintness or fainting). (27 Sep 1997) |
| addition reaction | <chemistry> Any reaction in which two chemicals combine to form a single chemical. (15 Jan 1998) |
| adverse drug reaction reporting systems | Systems developed for collecting reports from government agencies, manufacturers, hospitals, physicians, and other sources on adverse drug reactions. (12 Dec 1998) |
| adverse reaction | Any undesirable or unwanted consequence of a preventive, diagnostic, or therapeutic procedure or regimen. (05 Mar 2000) |
| agar-gel reaction | <immunology> The reaction between an antibody and an antigen during an immunology lab procedure where the two are allowed to diffuse toward each other through an agar-gel medium. Lines of precipitation form in the places on the gel where the two react with each other and shows where the reaction has occurred. (09 Oct 1997) |