Commentary: Is it time to revisit the arterial pressure monitoring site for cardiac surgery?

Nakul Kumar, MD, and Mariya Geube, MD, FASE

Current research confirms that radial artery pressure measurement is associated with radial-to-femoral pressure gradient in cardiac surgery and smaller radial artery diameter is a risk factor.

See Article page 446.

Radial arterial catheterization has historically been the most common form of invasive arterial blood pressure monitoring used during surgical procedures and in the intensive care units. It is relatively safe due to collateral blood supply to the hand, and can reflect dynamic changes in blood pressure on a continuous basis.

Bouchard-Dechêne and colleagues explore the accuracy of blood pressure monitoring during cardiac surgery when radial arterial cannulation is utilized. In a nonrandomized and unadjusted analysis, the authors found significant radial-to-femoral pressure gradient in more than one-third of patients undergoing cardiac surgery and proposed the size of the radial artery as a potential risk factor. Patients with radial artery diameter <1.8 mm had higher frequency (up to 48%) and duration of the pressure gradient than those whose arterial diameter was larger. The authors report substantial difference in the measured pressure and vasopressor use that can result as a consequence of cardiopulmonary bypass (CPB) between radial and femoral arterial measurements. In this observational study, the decision about the site of the arterial catheter is left to the discretion of the anesthesiologist. The authors report no difference in the comorbidities and procedure type between patients who had radial artery catheter versus radial + femoral catheter. Yet, intraoperative characteristics, such as duration of CPB, aortic clamp time, combined procedures, and “ease of separation” from CPB suggest that patients who had dual arterial line monitoring had more complex and involving procedures. This brings the question that there is some selection process when the decision was made about pressure monitoring strategy, and that the groups are not similar. The fact that the study is prone to selection bias and the anesthesiologist practice is not adjusted for, should be acknowledged.

With this all-too-common scenario of underestimation of true arterial pressure with radial artery catheters, would it not be better to avoid it altogether? What would be the alternative? Double arterial cannulation for blood pressure monitoring can alleviate a radial arterial underestimation intraoperatively but introduces additional risk for the patient, also requires an operator (either the surgeon or anesthesiologist) to switch from their current task to perform the procedure, along with postoperative concerns for mobilization, infection, and bleeding risks. Many patients are started on anticoagulation on first postoperative day for various reasons, which puts the patient at risk of bleeding and thigh hematoma if the femoral arterial line is removed after anticoagulation was started.

Brachial arterial catheters for pressure monitoring have been feared historically for the concern of arterial thrombosis of an end artery leading to arm ischemia. Brachial arterial cannulation alleviates the need for 2 separate procedures by providing reliable accuracy of central arterial pressure immediately after CPB unlike radial artery catheterizations, and also mitigates the risks from 2 procedures to the patient., At our institution, we have experienced the safety and efficacy of utilizing brachial arterial catheters for both routine and complex cardiac surgical cases while the risk of complications remains low (complication rate requiring intervention is 0.26% with brachial artery cannulation). In addition, we also see good longevity and accuracy from these catheters during the postoperative intensive care unit stay. The low complication rate from brachial arterial cannulation may be due to high-dose heparin during CPB, and from experience in routine placement for a large number of cases. In the rare event of complications, they must be rapidly identified and intervened upon to minimize the risks from limb ischemia.

The authors did a great job recognizing the issue of radial-to-femoral pressure gradient and alluded to the size of the radial artery as a potential contributor; however, they do not discuss the implications of their research on the current wide spread practice of using radial artery monitoring during cardiac surgery. Because the pressure gradient is so common, even in simple procedures patients may receive unnecessary higher doses of vasopressors, in which case I expect their conclusion to be that an alternative monitoring site should be routinely used.

Ultimately, the debate of arterial blood pressure monitoring during cardiac surgery remains open and the conclusion that the sole use of radial arterial pressure monitoring is associated with higher rate of vasopressor use will undoubtedly lead to more questions on the most appropriate cannulation site. Accurate and reliable pressure monitoring is vital for patient care and safety during the perioperative period and brachial arterial catheters have repeatedly been shown to have a significantly greater accuracy and decreased vasopressor use compared with radial catheters.2, 3, 4, 5 Compared with femoral arterial catheters, brachial catheters are associated with lower infection risk, as well.,, We make a case based on experience and data from a large cohort of patients that brachial arterial cannulation for blood pressure monitoring during cardiac surgery is a safe and efficient technique for both simple and complex procedures that warrants consideration when dual arterial cannulation would otherwise be required.