OTHER CAUSES OF HYPOTENSION
Hypoglycemia, hypocalcemia, and hypermagnesemia can also cause
hypotension. The hypotension caused by alcohol or magnesium intoxication usually
responds to blood volume expansion or, better still, to an infusion of dopamine.
The arterial blood pressure of hypermagnesemic neonates also may increase with a
bolus of 100 to 200 mg/kg of calcium gluconate (given over 5 minutes) and a continuous
infusion of 100 to 300 mg/kg/day of the drug.
Polycythemia (hematocrit level > 65%) may also cause hypotension
because of increased PVR and decreased left ventricular filling pressures. Polycythemia
occurs with delayed clamping of or with stripping blood from the
Figure 59-10
The aortic blood pressure (PAO)
during first 5 hours of life of a premature infant with hypovolemia. PAO
values equal mean aortic pressures. (From Gregory GA: Resuscitation of
the newborn. Anesthesiology 43:225, 1975.)
umbilical cord. The hyperviscosity that accompanies polycythemia also increases
PVR, reduces pulmonary blood flow, and increases right-to-left shunting of blood
through the ductus arteriosus and foramen ovale. Hyperviscosity also increases the
systemic vascular resistance. The combination of hypoxia and increased vascular
resistance causes cardiorespiratory failure. Alleviating polycythemia improves the
cardiovascular status of the patient. An exchange transfusion with plasma or saline
with albumin (4 g of albumin/100 mL of saline) can be used to reduce the hematocrit
level to 50% to 55%. Late sequelae of polycythemia include cardiac and renal failure
and CNS injury.
