variety of electrolyte and metabolic disturbances that require urgent investigation
and intervention.
Blood pressure (BP) consists of two distinct phases. Systolic blood
pressure is the pressure exerted within the arterial vasculature during ventricular
contraction and is a reflection of the SV. Diastolic pressure reflects overall blood
volume and vascular tone (capacity). It is important to note that children have
such great physiologic reserves that they can sustain relatively normal systolic
blood pressure in even in instances of moderate shock. BP is relatively
insensitive since it drops only after all compensatory mechanisms to maintain CO
have been exhausted. In hypovolemic shock, a decrease in pulse pressure
(difference between systolic and diastolic blood pressures) is a more sensitive
and earlier indicator of blood loss compared to a decrease in blood pressure. In
certain congenital heart defects such as coarctation of the aorta, the BP may be
normal despite compromised CO if the systemic vascular resistance is high.
Normal to high systolic BP in conjunction with a low diastolic BP suggests
systemic vasodilation with acceptable ventricular ejection whereas a low systolic
BP with a high diastolic BP is indicative of poor ventricular ejection and systemic
vasoconstriction. Despite some limitations, BP is still an important vital sign that
can be monitored to trend responses to therapy. Normal ranges, based on age,
are available. Therefore, a provider should not overly rely on blood pressure as
indication of tissue perfusion.