ARTERIAL MONITORING PRESSURE MONITORING Indirect intermittent measurements of vascular pressures are considered inadequate in unstable critical patients Direct measurement involves the connection of.
PRESSURE MONITORING Indirect & intermittent measurements of vascular pressures are considered inadequate in unstable critical patients Direct measurement involves the connection of a transducer system via fluid-filled manometer tubing to a cannula placed in an appropriate vessel ADVANTAGES; Continuous information on the arterial & venous pressures Information available from the waveform Blood sampling (via arterial) POTENTIAL SOURCES OF ERRORS: Zero errors: - inaccurate zeroing of transducer - imprecise placement of the transducer Kinks, clots, bubbles in the manometer tubing leading to ; - Damping: Flattening of the pressure trace which underestimated systolic & overestimates the diastolic pressure MEAN is accurate - Resonance: Overshoot of the pressure waveform due to resonant oscillations within the measuring system Overestimates systolic & underestimates the diastolic pressure MEAN is accurate ARTERIAL PRESSURE MONITORING Arterial cannulation with continuous pressure waveform display remains the accepted standard for BP monitoring Indications and Advantages - Frequent ABG’s and blood sampling - Continuous real-time monitoring when rapid, moment-to-moment BP changes are anticipated, i.e CV instability, major fluid shifts or EBL - Failure of indirect BP monitoring i.e morbid obesity, burned extremity - Deliberate induced induced hypotension - Cardiac surgery for cardiopulmonary bypass - Major vascular surgery - Administration of vasoactive drug infusions The arterial tree starts with the aorta and the major branches of this vessel The aorta and its branches stretch to receive blood from the left ventricle and recoil to distribute the blood and to maintain arterial pressure Arteries and arterioles control blood pressure through vasoconstriction or vasodilation Arterioles are the primary sites that contribute to systemic vascular resistance (SVR) Arterial pressure is measured at its peak, which is the systolic blood pressure (SBP), and at its trough, which is the diastolic blood pressure (DBP) Pulse pressure is the difference between systolic and diastolic pressure A normal pulse pressure in the brachial artery is approximately 40 mm Hg An increased pulse pressure may be the result of increased stroke volume or ejection velocity and is common during fever, exercise, anemia, and hyperthyroidism Other causes of increased pulse pressure include bradycardia (increased stroke volume), aortic regurgitation, and arterial stiffening, which is most noticeable after the age of 50 to 60 years An acute decrease in pulse pressure may indicate an increase in vascular resistance, decreased stroke volume, or decreased intravascular volume Systemic mean arterial pressure (MAP) is defined as the mean perfusion pressure throughout the cardiac cycle MAP is sensed by baroreceptors located in the carotid sinuses and the arch of the aorta These receptors control arterial pressure mainly by adjusting heart rate and arteriolar vessel radius MAP is also the basis for autoregulation by some organ systems such as the kidney, heart, and brain Over damping causes slurred upstroke, absent dicrotic notch, and loss of fine detail Causes include blood clots, air bubbles in the tubing, and kinked catheters Under damping produces exaggerated peaks and troughs in the waveform It can cause falsely high systolic pressures and low diastolic pressures Causes include long connecting lines (>1.4 mm), small tubing (