PubMed · 8219973
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I G Chadwick, G P Todd, L E Ramsay. 1993-09-25. Forced hyperventilation increases blood pressure.. https://doi.org/10.1136/bmj.307.6907.803-c
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BACKGROUND: The systemic hypotension during human sepsis has been ascribed to increased production of nitric oxide (NO). Therefore, inhibitors of NO synthesis have been used in the treatment of hypotension in patients with septic shock. In addition, NO production may inhibit the synthesis and vasoconstrictor effects of endothelin-1 (ET-1). In this study, we tested whether ET-1 contributed to the vasopressor action of the NO synthase inhibitor NG-nitro-L-arginine methyl ester (L-NAME) in patients with severe septic shock. METHODS AND RESULTS: Compared with healthy volunteers, patients with septic shock had increased plasma levels of nitrite/nitrate (37+/-5 [SEM] versus 12+/-5 mmol/L, P<0.01), the stable end products of NO metabolism, and ET-1 (45+/-7 versus 3+/-2 pg/mL, P<0.001). Plasma ET-1 concentration was not related to plasma nitrite/nitrate concentration or blood pressure. Continuous infusion of L-NAME (1 mg. kg-1. h-1 IV) for 12 hours increased mean arterial pressure by 43+/-5% and systemic vascular resistance by 64+/-10% (both P<0.01). The increase in blood pressure and systemic vascular resistance correlated positively with the level of ET-1 (both P<0. 005) but not with plasma nitrite/nitrate level. L-NAME infusion did not result in significant changes in the plasma concentrations of ET-1 or nitrite/nitrate. CONCLUSIONS: NO and ET-1 may both play a role in the cardiovascular derangements of human sepsis. Although L-NAME does not increase ET-1 concentration in patients with septic shock, the vasopressor response induced by L-NAME depends on the plasma level of ET-1. These findings may indicate that inhibitors of NO synthesis unmask a tonic pressor response of ET-1 in human septic shock.
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Factors that affect the reliability and accuracy of blood pressure measurements are reviewed, and new technologies for measuring blood pressure are discussed. Blood pressure measurements obtained in an office, hospital, or clinic are subject to variation and error. Reasons for variations include the wrong cuff size, improper inflation or deflation technique, and patient apprehension ("white-coat syndrome"). Ambulatory blood pressure monitoring (ABPM) involves the use of a fully automated standard arm cuff that is inflated at predetermined intervals by a small battery-powered pump unit. The most reliable ABPM method is the oscillometric method, which detects subtle changes in air pressure within the cuff system caused by fluctuations of the brachial artery. The process for interpreting 24-hour ABPM data is still evolving. Twenty-four-hour ABPM has been shown to eliminate white-coat hypertension and is also useful for assessing patients whose blood pressure is inappropriately high in the absence of end organ damage, monitoring persons at risk of developing hypertension because of their race or family history, determining a medication's 24-hour effect on blood pressure, and assessing the early-morning rapid rise in blood pressure, which has been linked to an increased risk of nonembolic stroke and myocardial infarction. ABPM enables identification of patients whose blood pressure is elevated in the office but normal at home, allows more appropriate screening of patients for clinical trials, gives reproducible values, and enables evaluation of drug duration and action.