Apr 15, 2022, 9:29 AM
Invasive hemodynamic monitoring is an important component in the effective management of critically ill patients, especially those in shock states. This type of surveillance is accomplished through the use of pulmonary artery catheters, central venous catheter, and arterial pulse wave analysis and is used to assess the performance of the cardiovascular system, including perfusion pressure and oxygen delivery, and to determine correct therapeutic intervention to optimize end-organ oxygen delivery while monitoring responses to therapeutic interventions to guide continued management. Invasive hemodynamic monitoring may be particularly useful in shock states, right ventricular infarction, ruptured ventricular septum, mitral regurgitation, low cardiac output syndrome, cardiac tamponade, and pulmonary embolism (Laher et al, 2017). Invasive hemodynamic monitoring is indicated in acute and complex conditions including in the concomitant use of an LVAD or ECMO. It is not indicated in for stable heart failure patients and for those with chronic conditions for which the response to medical therapy has been appropriate. It may be used in the perioperative setting in those that are high risk for complications to attenuate respiratory and hemodynamic deterioration, especially during anesthetic induction (Hernandez-Monfort et al, 2022).
Cardiogenic shock is a low cardiac output state that is most commonly caused by an AMI with resultant left ventricular dysfunction. This type of shock is associated with acutely deteriorating hemodynamic status and end-organ hypoperfusion, requiring vasopressors, inotropes, and mechanical ventilatory support, which often necessitates the use of invasive hemodynamic monitoring. Classically, cardiogenic shock is characterized by ineffective stroke volume, low cardiac output, low cardiac index, elevated systemic vascular resistance, and high PCWP. Treatment may be specific to underlying etiology and per cardiology. Low cardiac output conditions, including cardiogenic shock, require management to achieve a balance between tissue oxygen delivery and demand. This is achieved through pharmacologic augmentation with inotropes including epinephrine, dopamine and dobutamine. Additionally, the use of systemic vasodilators including nitroprusside is associated with a 17% increased in cardiac index. Vasopressin and norepinephrine may be used for blood pressure support despite the resultant increase in SVR to maintain adequate perfusion to vital organs (van Diepen et al, 2017). Invasive positive pressure ventilation via mechanical ventilation causes left ventricular wall pressure to remain constant, generating a flow gradient between the thorax and peripheral organs, creating an intra-aortic balloon like effect, lowering SVR and left ventricular afterload and improving cardiac output. The additional of a pulmonary artery catheter may guide pharmacological interventions by indirectly measuring SVR, PVR, cardiac index, and oxygen deliver concentration and more, (Alvair et al, 2018). Risk factors associated with the use of invasive hemodynamic monitoring include increased risk for vascular injury, bleeding, thrombosis, and distal limb ischemia. Risk factors associated with the cardiogenic shock patient include cardiopulmonary arrest, arrythmias, acute kidney injury, multisystem organ failure, thrombosis, stroke, and death (Hernandez-Montfort et al, 2022).
The cardiac index is an assessment of cardiac output and based on the amount of blood ejected from the LV ventricle in one minute relative to body surface area and ranges from 2.5-4L/min/m2. Differential diagnoses associated with cardiac index alterations include AMI, cardiogenic shock, SVT, heart failure, valvular disease, and septic shock (Fleitman et al 2021).
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