Making the most of hemodynamic monitoring in the ICU: observing and optimizing appropriate parameters

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Date: May 2003
From: The Journal of Critical Illness(Vol. 18, Issue 5)
Publisher: CMP Medica, LLC
Document Type: Article
Length: 7,188 words

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ABSTRACT: In addition to traditional, noninvasive monitoring used in the ICU, an arterial catheter often is placed in patients with hypotension or in those starting on mechanical ventilation. The pulmonary artery catheter (PAC), which indirectly measures cardiac output (CO), can help identify different types of shock and mechanical complications of acute myocardial infarction, including mitral regurgitation, ventricular septal perforation, and tamponade. The PAC also has become a common supplement to clinical assessment for guiding the therapeutic management of hemodynamic parameters. Transesophageal echocardiography (TEE) can provide information about cardiac valvular disease, infectious and neoplastic mass lesions, and atrial septal defects. In patients on ventilation, TEE may be preferable to catheterization. There has been interest in using noninvasive thoracic bioimpedance in the hemodynamic monitoring of GO, but its use is still experimental and there is some controversy over the accuracy of its measure ments. (J Crit illness. 2003;18(5):196-207)

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It has become the standard of care in ICU practice to monitor physiologic parameters such as blood pressure, heart rate (HR), electrical activity of the heart, and urinary output. It is now thought that knowledge and monitoring of additional hemodynamic parameters such as cardiac output (CO) and pulmonary artery pressures (PAPs) may aid in diagnosis and help guide the management of critically ill patients.

In this article, we discuss current methods and new, less invasive alternatives that are available but not yet widely used for bedside hemodynamic monitoring, focusing on arterial monitoring, the pulmonary artery catheter (PAC), and echocardiography. We also provide guidance in data interpretation and clarify the context in which hemodynamic measurements can be helpful. We present the advantages and limitations of the available methods, allowing you to select the most appropriate approach for your setting and practice.

ARTERIAL MONITORING

In addition to traditional noninvasive methods for monitoring blood pressure, it is common in the management of hypotension or with the initiation of mechanical ventilation for a catheter to be placed in the radial or, alternatively, the femoral or axillary artery. The advantages of direct arterial pressure monitoring include continuous and reliable measurement of blood pressure and ready availability of arterial blood for laboratory analysis.

Continuous and accurate measurement of blood pressure is integral to the successful treatment of hypotensive patients with labile blood pressure. It provides a faster and more accurate assessment of the pressure response to vasodilators, vasopressors, inotropic agents, and ventricular-assist devices, thus facilitating the restoration of adequate perfusion. Arterial monitoring also is helpful for assessing the efficacy of therapy in hypertensive crisis or urgency.

Indications for arterial catheter placement are outlined in Table 1. While the benefits of monitoring have not been studied formally, such measurements are helpful in the diagnosis and management of derangement in gas exchange and of acid-base disorders. (1) Pulse oximetry often is sufficient to assess oxygenation; however, a [PO.sub.2] measured from arterial blood is desirable when a reliable signal cannot be obtained by pulse oximetry, when oxygen saturation is less than 92% (and pulse oximetry becomes less reliable), or when an accurate [PO.sub.2]...

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Gale Document Number: GALE|A102540055