Hypotension in dogs is a relatively rare circulatory disorder characterized by arterial blood pressure < 90 mm Hg.
In dogs, volatile anesthetics (e.g. isoflurane) decrease myocardial contractility and cardiac output, which results in dose-dependent hypotension which is not counteracted by administering intravenous isotonic fluids in dogs anesthetized at a surgical depth of anesthesia, even under conditions of surgical stimulation.
However, unlike arterial blood pressure, cardiac output can be positively influenced by administering intravenous fluid. By increasing circulating volume and therefore venous return (preload), it is possible to increase stroke volume, which contributes significantly to changes in cardiac output.
Therefore, intravenous fluid therapy is often recommended in anesthetized hypotensive patients to increase blood pressure since hypovolemia may be the cause of the hypotension and volume replacement will therefore benefit the patient.
Intravenous isotonic crystalloids fluids is recommended in most cases.
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