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post-operative pain control and during therapy
sessions to allow pain free movement during exercises. Electrotherapy variables include intensity, mode, ramp duration, on:off time, pulse width, frequency, treatment duration, and treatment frequency. Intensity is measured in milliamps (mA), and is generally between 50 and 400mA. Intensity determines how many nerve fibers are stimulated. Mode can be set to constant, synchronous, or alternate. In constant, there is a constant flow of current through both channels. In synchronous, both channels turn on and off simultaneously. In alternate,
the one channel turns on as the other turns off. Ramp durations is the time that the stimulus takes to reach peak intensity and is measured in seconds. On:Off time is the ratio of time during which the intermittent current is on and is measured in seconds. Pulse width is the length of time that pulses of electricity are on and is measured in microseconds. Pulse width determines which nerve fibers are stimulated, and widths of greater than 150 microseconds are more comfortable for the patient.Frequency, measured in Hertz (Hz) or pulses per second, is the speed at which pulses enter the body, and determines the amount of muscle tension that is developed. Higher frequency is more comfortable. Frequencies of 1 to 10Hz are used for pain management, while frequencies of 25-50Hz generate strong tetanic muscle contractions. Treatment duration is generally between 15 and 20 minutes, and treatment frequency
is generally at least two to three times per week. Depth of penetration is determined by the distance between the electrodes.Electrodes must be flexible to conform
to the patient’s muscles, low resistance (less than 100 ohms), highly conductive, reusable, inexpensive, and appropriately sized for the patient. A medium, usually gel, is necessary to transmit the current between the electrode and the patient’s skin.
U. Giger1
1School of Veterinary Medicine, University of Pennsylvania, Philadelphia, USA
Although strictly speaking polycythemia implies a rise
of all blood cell counts above normal, the occurrence
of leukocytosis and thrombocytosis along with erythrocytosis is exceptionally rare in companion animals. Hence, polycythemia would be more appropriately called erythrocytosis and clinically refers to an increase to an above normal red blood cell count, hematocrit or packed cell volume (PCV), and hemoglobin (Hb) concentration. Polycythemic animals will not show clinical signs until
the PCV reaches >60% with some of the highest PCVs exceeding 85%. Because of an underappreciation of the normal upper limit of the PCV in cats (48%) versus dogs (56%), polycythemia is generally underdiagnosed in cats. Based upon blood volume and red cell mass, polycythemia can be divided into relative and absolute polycythemias, which represent completely different conditions, both requiring immediate but opposing therapeutic interventions.
Relative polycythemia is characterized by an elevated PCV in the presence of a normal (or even decreased) total red blood cell mass. This is usually due to a decrease in plasma volume associated with severe dehydration or increased serum total proteins, e.g. profound vomiting and diarrhea, or severe burns. The hematocrit is generally only mildly increased, therefore relative polycythemia is rarely associated with signs of hyperviscosity, and the clinical features of the underlying disorder prevail. Because of the obvious signs of dehydration, relative polycythemia is usually easily recognized and simply corrected with aggressive fluid therapy.
Absolute or true polycythemia is characterized by an expanded red blood cell mass. Splenic contraction is an unlikely cause in dogs and cats, as it only marginally increases the PCV. The blood volume and red cell mass could be determined by labeling red cells radioactively or with biotin. This is, however, rarely if ever needed in clinical practice, as dehydration can be readily excluded as cause of relative polycythemia. More difficult is the differentiation of absolute polycythemia into primary
or secondary polycythemia, which depends on whether the condition is erythropoietin independent or dependent.
Some clinicians readily equate absolute erythrocytosis
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