What is included in the intraoperative management of aortic stenosis (AS) in noncardiac surgery patients?

Updated: Jul 16, 2021
  • Author: Lindsay A (Finger) Raleigh, MD; Chief Editor: Sheela Pai Cole, MD  more...
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Answer

Answer

The perioperative risks associated with noncardiac surgery in the AS patient can be mitigated with careful preoperative planning and vigilant intraoperative management. Using the severity of stenosis and the risk of surgery as bases, the anesthesiologist must choose a suitable anesthetic approach and consider the appropriate level of intraoperative monitoring needed to provide optimal care.

Safe anesthetic management of these patients involves maintaining CPP, sinus rhythm, and adequate preload while avoiding tachycardia. General anesthesia or neuraxial (ie, spinal or epidural) anesthesia can be employed, depending on other anesthetic and surgical considerations, provided that any adverse hemodynamic effects are minimized.

The greatest concern with neuraxial anesthesia is the subsequent decrease in SVR associated with local anesthetic medications. The resulting hypotension can decrease CPP and precipitate cardiovascular collapse. However, the effects of neuraxial anesthesia on SVR can be mitigated with careful monitoring, meticulous fluid management, and appropriate medication administration.

In patients with mild-to-moderate AS who are undergoing low-risk surgical procedures, standard ASA monitors, including noninvasive BP monitoring, may be adequate; however, in patients with severe ASand those undergoing moderate- to high-risk procedures, more advanced monitoring is warranted. Invasive arterial catheterization allows continuous BP monitoring, enabling the anesthesiologist to react quickly to changes in afterload and optimize CPP. Placement of an arterial line before induction of anesthesia is often warranted to minimize the hemodynamic affects associated with induction agents.

With impaired LV compliance, maintaining preload is important. If large shifts in intravascular volume are expected, pulmonary artery catheterization may be helpful in assessing ventricular filling pressures and cardiac output; it may also be beneficial in patients with reduced LV systolic function as a means of tracking trends in mixed venous oxygen saturation and cardiac output. In addition, central venous access enables the administration of vasopressors and inotropic agents that may be needed to support hemodynamics.

Intraoperative echocardiography can provide real-time monitoring of ventricular systolic and diastolic function and assessment of wall motion and ventricular filling. TTE can be performed if optimal windows can be accessed during the case and are not limited by the surgical field. TEE offers the ability to carry out continuous monitoring in almost any clinical situation.

Maintaining sinus rhythm is vital in the setting of AS. In patients with reduced ventricular compliance and diastolic dysfunction, the atrial component of diastole may provide as much as 40% of ventricular filling. Arrhythmias are poorly tolerated by these patients. Additionally, tachycardia limits the time in systole and diastole, which may limit the heart's ability to increase stroke volume in response to increases in oxygen demand and decrease the diastolic coronary artery perfusion time. Significant bradycardia may also reduce the heart's ability to provide enough cardiac output in times of stress.

Electrocardiographic (ECG) monitoring is routinely performed as part of the ASA standard monitors and can help detect myocardial ischemia and identify arrhythmias that occur during anesthesia. TEE can also show signs of myocardial ischemia, with regional wall-motion abnormalities or changes in LVEF.

Phenylephrine is the preferred agent for treating hypotension. Through its alpha-agonist properties, phenylephrine increases SVR and maintains CPP without increasing chronotropy or inducing tachycardia. In patients with a reduced LVEF, inotropic agents (eg, norepinephrine or epinephrine) may be considered. However, these medications should be administered with caution and under advanced hemodynamic monitoring. Avoiding tachycardia and arrhythmias is of the utmost importance.

With close intraoperative monitoring and careful anesthetic planning, emergency and elective noncardiac surgical procedures can be performed safely and with an acceptable risk profile. Making the surgical team aware of the patient’s cardiac risk factors further conduces to safe surgery. Collaboration between the anesthesia and surgical teams permits the identification of appropriate intraoperative hemodynamic goals and fluid resuscitation strategies, as well as allows for changes in surgical techniques that may be warranted to minimize the risk of adverse outcomes.


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