(PT) the time taken for blood clotting to occur in a sample of blood to which calcium and thromboplastin have been added. A prolonged PT (compared with a control sample) indicates a deficiency of *coagulation factors, which – with calcium and thromboplastin – are required for the conversion of prothrombin to thrombin to occur in the final stages of blood coagulation. Measurement of PT is used to control anticoagulant therapy (e.g. with warfarin). See INR.
An inactive substance in the blood PLASMA that is the precursor of the ENZYME, thrombin, which clots the blood. The conversion occurs when a blood vessel is damaged and the process of blood COAGULATION occurs.... prothrombin
a quickly performed test to assess the adequacy of circulation in an individual with poor cardiac output. An area of skin is pressed firmly by (say) a fingertip until it loses its colour; the number of seconds for the area to return to its original colour indicates capillary refill time. Normal capillary refill takes around 2 seconds. Slow capillary refill may occur globally in an individual with poor circulation or in a small area (e.g. a toe) in which local circulation is compromised (due, for example, to peripheral vascular disease). This test may not be very useful in people with dark skin.... capillary refill time
(clotting time) the time taken for blood or blood plasma to coagulate (see blood coagulation). When measured under controlled conditions and using appropriate techniques, coagulation times may be used to test the function of the various stages of the blood coagulation process.... coagulation time
the rapid acquisition and manipulation of ultrasound information from a scanning probe by electronic circuits to enable images to be produced on TV screens almost instantaneously. The operator can place the scanning probe accurately on the region of interest in order to observe its structure and appreciate moving structures within it (see Doppler ultrasound). Using similar techniques, the instantaneous display of other imaging modalities, such as *computerized tomography scanning and *magnetic resonance imaging, can now be achieved. Real-time imaging is useful in guiding *interventional radiology procedures, for example, allowing a needle to be guided accurately as it is passed into the body. It is also useful for observing dynamic physiological activity.... real-time imaging
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