Continuous cardiac monitoring is vital (Table2).
Table 2 Safety of methods of cardiovascular assistance
Hypotension indicates an unfavorable prognosis (Tabje.3) and is sometimes a sign of an irreversible phase of the illness, since hypothyroid patients usually have mild diastolic hypertension (HyJ.§nd®IaDd..Rosengvj.stlll1985; Roti e.L§L 1993). Several other factors, such as blood loss by gastrointestinal bleeding (which should be sought and treated), aggressive warming, and overuse of diuretics, may aggravate hypotension. Concurrent hypovolemia aggravates tolerance to blood loss. Transfusion with whole blood is the fastest and most effective treatment for hypotension and anemia, particularly when hematocrit is below 30 per cent. Careful monitoring of central venous pressure is required during the transfusion. In the absence of severe anemia, colloid solutions can be used instead of blood transfusions.
Table 3 Factors indicating unfavorable prognosis
Hypotension can occur as a complication of a silent myocardial infarction. Diagnosis may be difficult because of high levels of muscular enzymes and abnormalities on ECG due to severe hypothyroidism itself (Nicp!lpfflnandMlLpPresti 1993). Echocardiography may help to make a definite diagnosis.
Caution is needed in treating congestive heart failure. Digitalis, if used, should be given at low dose, since drug metabolism is slowed during hypothyroidism ( NicolofL
and Lo.P.r.estj_ 1993). The risk of overdose is high for digitalis, diuretics, and afterload-reducing agents. These drugs should be prescribed with caution and at low dosage in such patients.
Vasoactive drugs such as dopamine are ineffective and may be dangerous, precipitating ventricular arrhythmias; a-adrenergic agents are not indicated as vasoconstriction already exists and may induce tachyarrhythmias (Nicoloff land L.O.PIeMiJ...9.9.3.). Transvenous ventricular pacing may dramatically reduce cardiac output, which is already reduced. If pacing is necessary, an atrioventricular system should be used.
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