Normally, when patients assume an upright posture, approximately 500 to 700 ml of blood is pooled in the lower extremities and in splanchnic and pulmonary tissues. In response to decreased venous blood return to the heart, there is a transient reduction in cardiac output and reflex stimulation of the cardiopulmonary, aortic, and carotid baroreceptors, which in turn increase sympathetic outflow and inhibit parasympathetic activity.12 The initial reduction in blood volume and inadequate cardiovascular compensation for the decline in cardiac preload may in susceptible patients (i.e., those with age-related physiologic changes and diseases) and/or those taking medications (alpha-adrenergic blocking agents, alpha-beta-adrenergic blocking agents, diuretics, and nitrates), impair homeostatic mechanisms of BP regulation and lead to orthostatic hypotension (OH).
OH is commonly defined as a supine-to-standing BP decrease >20 mmHg systolic or >10 mmHg diastolic. It has been shown to be a significant risk factor for syncope and falls and it is associated with a 64% increase in age-adjusted mortality compared to a control population.12 When treating older hypertensive patients, clinicians should be alert to the potential of OH as suggested by historical or clinical evidence of postural unsteadiness, dizziness, or fainting.
In a survey of 2,704 dentists throughout North America, a total of 13,836 medical emergencies occurred in 2704 dental offices within a 10-year period.25 Of these, 2,475 (17.9%) were diagnosed as postural hypotension. Based on these data, the incidence of OH is 0.02 cases per dental office per year. The lack of prodrome associated with OH should prompt OHCP to be proactive. Since antihypertensive medications and meals can cause major BP reductions in susceptible, especially elderly patients, it is prudent to schedule dental appointments 30 to 60 minutes after the ingestion of medications and meals.26 Following completion of dental treatment, the patient should be allowed to assume a sitting position for at least two minutes and then allowed to stand.27 Strategies to manage OH are summarized in Table 5.
|Symptoms and Signs||First Response|