Blood pressure responses to phenylephrine infusions in subjects with Cushing's syndrome.
The pathogenesis of the hypertension associated with Cushing's syndrome is not completely understood. Sensitivity to pressor agents may play a role. We have investigated this possibility by measuring blood pressure (BP) during incrementally increasing infusions of the alpha-adrenergic agonist phenylephrine. Ten subjects (8 women: 2 men), aged 40 +/- 5 years (mean +/- s.e.m.) with Cushing's syndrome were studied. All had raised BP but none had received any anti-hypertensive treatment for at least 16 days before study. Ten age- (40 +/- 5 years) and sex-matched control subjects were also studied. At 13.30, 30 min after a light meal, subjects had an intravenous cannula inserted, ECG leads and a sphygomanometer cuff attached, and then rested supine in a quiet room for 30 min. Phenylephrine was then infused incrementally at intervals of 5 min. The doses used were 0.3, 0.6, 0.9, 1.35 and 2 micrograms/kg/min. Basal mean blood pressure (MAP) was 108 +/- 2 mm Hg (mean +/- s.e.m.) in patients and 74 +/- 3 mm Hg in controls (P < 0.05) and pulse rate was 75 +/- 5 and 68 +/- 3 beats/min (NS), respectively). MAP increased and pulse rate decreased linearly with time. The rate of rise of MAP was 1.7 +/- 0.4 mm Hg/min in subjects and 1.1 +/- 0.2 mm Hg/min in controls (NS). The rate of decrease of pulse was significantly more rapid in Cushing's subjects than in controls (1.4 +/- 0.2; 0.6 +/- 0.1 beats/min2; P < 0.05). The lack of any increased BP response to alpha-adrenergic stimulation suggests that altered sensitivity is not a major cause of the increased BP seen in patients with Cushing's syndrome.
McKnight
J A
JA
Sir George E Clark Metabolic Unit, Royal Victoria Hospital, Belfast, Northern Ireland.
Rooney
D P
DP
Whitehead
H
H
Atkinson
A B
AB
D000293:Adolescent; D000316:Adrenergic alpha-Agonists / Q000627:therapeutic use*; D000328:Adult; D001794:Blood Pressure / Q000187:drug effects*; D003480:Cushing Syndrome / Q000188:drug therapy / Q000503:physiopathology*; D005260:Female; D006801:Humans; D006973:Hypertension / Q000209:etiology* / Q000503:physiopathology; D007262:Infusions, Intravenous; D008297:Male; D008875:Middle Aged; D010656:Phenylephrine / Q000627:therapeutic use*
D000316:Adrenergic alpha-Agonists; D010656:Phenylephrine