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Intraoperative Invasive Blood Pressure Monitoring and the Potential Pitfalls


Invasive intraarterial blood pressure measurement is currently the gold standard for intraoperative hemodynamic

monitoring but accurate systolic blood pressure (SBP) measurement is difficult in everyday clinical practice, mostly because

of problems with hyper-resonance or damping within the measurement system, which can lead to erroneous treatment decisions if

these phenomena are not recognized. A hyper-resonant blood pressure trace significantly overestimates true systolic blood

pressure while underestimating the diastolic pressure. Invasively measured systolic blood pressure is also significantly more

affected than mean blood pressure by the site of measurement within the arterial system. Patients in the intraoperative

period should be treated based on the invasively measured mean blood pressure rather than the systolic blood pressure. In

this review, we discuss the pros/cons, mechanisms of Disposable

IBP Transducers
, and the interpretation of the invasively measured systolic blood pressure value.






Introduction & Background


Disposable IBP

Transducer Kit-Single Channel
is the gold standard of arterial pressure measurement in 10-20% of high-risk patients [1

-2]. In the remaining 80%-90% of surgical patients, the standard intermittent non-invasive blood pressure (BP) that is

obtained using oscillometry with a brachial cuff has been shown to have only poor agreement with IBP in critically ill

patients [3-4]. These observed measurement differences are clinically significant because they would have triggered a change

in treatment in as many as 20% of the critical care patients. Non-invasive oscillometric BP measurement with a brachial cuff

tends to, on average, overestimate BP during hypotension and underestimate BP during hypertension, with a significant bias

and considerable scatter. Invasive BP measurement with an arterial catheter, providing continuous BP measurements, detected

nearly twice as many episodes of hypotension as intermittent oscillometric measurements with a brachial cuff [5]. Continuous

rather than intermittent hemodynamic monitoring is highly desirable in high-risk patients. Even when continuous BP monitoring

was accomplished in medium-risk patients with non-invasive techniques, the number of episodes of intraoperative hypotension

was still reduced by half when compared to intermittent monitoring with a brachial cuff [6]. Although non-invasive continuous

monitoring has fewer complications than arterial cannulation, it has not yet Disposable IBP Transducer Kit-Double Channel as the gold

standard in high-risk patients, but rather serves as an alternative in low and medium-risk patients where IBP measurements

are not warranted [7].






An adequate blood pressure level is a means to achieve the ultimate goal of the circulation, which is adequate end-organ

perfusion and tissue oxygenation. Adequate organ perfusion is mostly regulated locally, in the organs, by changing the local

vascular resistance, which, when seen over multiple organs and the entire circulation, works as a re-distribution of the

total flow or cardiac output (CO) [8]. In addition, the total flow or CO is also regulated centrally if this re-distribution

is not enough. The local flow control via regulation of resistance of the arterioles only functions properly under the

condition of adequate perfusion pressure, in which the mean systemic arterial pressure plays a central role. Continuous

monitoring of local organ circulation, global flow, or CO and arterial pressure is, therefore, the key. Monitoring the

microcirculation has been shown to be useful when determining the optimal BP range that is associated with adequate

regulation of local blood flow and tissue oxygenation for an individual patient [9-10]. Pulse contour analysis provides a

means of assessing global flow or CO because it has long been recognized that an apparently adequate BP level may not

necessarily be associated with an adequate total blood flow to all the tissues [11-12]. Different organs have a different

range of perfusion pressures that allow for adequate local control of organ flow. While the coronary circulation can increase

flow fivefold as long as heart rate is maintained at 70 bpm, diastolic arterial pressure is maintained at adequate levels and

coronary obstructive lesions are absent, the kidney is much more sensitive to decreases in perfusion pressure [13]. The

average lower limit of cerebral blood flow autoregulation in normotensive adult humans is around a mean arterial pressure

(MAP) of 70 mmHg [14]. Hence, the heart has a greater range of adequate perfusion pressures than both the brain and the

kidneys. Blood pressure goals as adequate perfusion pressure ranges, therefore, need to be specifically determined and

adjusted for every individual clinical situation by considering the patient’s specific comorbidities as well as the planned

surgical procedure.






Blood pressure and surgical outcomes 


Although the real target is adequate total blood flow and adequate local flow to individual organs, most outcome data are

available for blood pressure. Hypotension has been associated with increased postoperative morbidity. Even short durations of

intraoperative MAP less than 55 mmHg are associated with myocardial injury and acute kidney injury (AKI) [15]. A

perioperative quality initiative consensus statement also concluded that even brief durations of systolic arterial pressure

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