Mount Sinai Expert Guides. Группа авторов

       Patients requiring ICU care often require multiple forms of hemodynamic monitoring.

       There has been a tremendous increase in usage of invasive hemodynamic monitoring in order to enhance our understanding of patients’ hemodynamics and helping to guide appropriate therapeutic interventions.

       Although there is a paucity of evidence to support the use of many of these invasive monitors, they are very commonly used in the ICU.

       Direct arterial pressure monitoring is recommended for all ICU patients with hemodynamic instability who require inotropic or vasopressor medications as well as significant ventilatory deficits. This allows for continuous monitoring of blood pressure as well as access to the arterial circulation for the measurement of arterial oxygenation and frequent blood sampling.

       As the pulse moves peripherally, the pressure waveform is distorted with higher systolic pressure and pulse pressure (Figure 11.1).

       Radial artery: common site of cannulation. Check collateral flow of ulnar artery with the Allen’s test, which has low reliability.

       Brachial artery: located in antecubital fossa, lack of collateral circulation, median nerve injury possible.

       Axillary artery: can cause axillary nerve damage from hematoma or traumatic cannulation.

       Femoral artery: prone to pseudoaneuryms and atheroma formation.

       Dorsalis pedis and posterior tibial arteries: most distorted waveforms.

       Deficiencies of collateral circulation (e.g. Raynaud’s phenomenon).

       Rates of up to 10%.

       Hematoma, bleeding, vasospasm, arterial thrombus, aneurysm, dissection, pseudoaneurysm, infection.

       Multiple proprietary systems have developed algorithms for estimating cardiac output from the arterial waveform. Arterial pulse contour analysis can evaluate stroke volume to calculate cardiac output and examine stroke volume variation to assess fluid responsiveness.

       Characteristics of the arterial pressure waveform are affected by changes in vascular compliance, aortic impedance, and peripheral arterial resistance, limiting the accuracy and utility of this class of monitors.

       Pulse contour cardiac output (PiCCO) requires the insertion of a central venous catheter and a thermodilution arterial line.

       It provides hemodynamic monitoring by combining pulse contour analysis and a transpulmonary thermodilution technique to provide a continuous display of PiCCO cardiac index (L/min/m2) and stroke volume (mL/kg).

       Calibration of the PiCCO to more accurate transpulmonary thermodilution cardiac output measurements needs to be repeated every 8 hours, or more frequently if the patient is hemodynamically unstable.

       Additional data derived from the PiCCO system include:Extravascular lung water index (mL/kg).Global end‐diastolic volume (measure of cardiac preload in mL/m2).Systemic vascular resistance index (dyn·s/cm5/m2).Stroke volume variation (%).

       Requires an arterial line.

       Uses pulse contour analysis based on an algorithm to provide continuous cardiac output, stroke volume, and stroke volume variation in real time.

       Provides an estimate of cardiac output using the standard deviation of the arterial pulse pressure around the mean arterial pressure and a conversion factor.

       Calibration is not required.

       Lithium dilution cardiac output (LiDCO) requires a peripheral or central arterial line.

       Uses pulse power analysis rather than pulse contour analysis. The algorithm is based on the assumption that the net power change in the system in a heartbeat is the difference between the amount of blood entering the system, the stroke volume, and the amount of blood flowing out peripherally.

       Requires calibration using transpulmonary lithium indicator dilution technique via a peripheral venous line. It is not as accurate when the patient is receiving lithium or certain neuromuscular‐blocking agents.

       CVP is measured via a central line at the level of the right atrium or vena cava. It is equal to the right ventricular end‐diastolic pressure.

       CVP can be used to determine preload, the filling pressure of the heart. It has been used to estimate whether a patient is adequately resuscitated as well as helping to assess right ventricular function.Table 11.1 Waveform components.Waveform/descentPhase of cardiac cycleECGMechanical eventA waveEnd diastoleFollows P wavePressure increase due to atrial contractionC waveEarly systoleFollows R wavePressure increase due to tricuspid bulging into the right atriumV waveLate systoleEnd of T wavePressure increase due to systolic filling of the atriumX descentMid systoleDrop in atrial pressure due to atrial relaxationY descentEarly diastoleDrop in atrial pressure due to early ventricular filling

       A central line allows for infusion of hypertonic solutions and medications that can damage peripheral veins. It also allows for serial venous blood