How is blood pressure monitored during surgery?

Question

Yesterday I had a minor procedure involving anesthetic and being "on the table". As the blood pressure cuff inflated, it occurred to me that on medical TV shows, where they are doing far more significant surgeries, the doctors are depicted as having instant and constant measures of the patient's blood pressure. They yell out numbers as the pressure falls and generally do the "we're losing him!" thing.

But my cuff only inflated every few minutes, and took probably at least a minute to get even one reading, what with the inflating and the slow deflating, same as the old days when a person did that.

I did find a few articles describing tech that can read bp continuously, eg Invasive (intra-arterial) blood pressure (IBP) monitoring but I can't tell whether it's normal to use that for anything and everything or only for some patients.

So, are the TV shows making up tech for drama reasons, or is it common to measure blood pressure continuously for big surgeries?

Answer 1

Monitoring of patient blood pressure is vital because anesthesia and surgery can cause rapid changes in vital functions. Even brief periods of hypotension are associated with poor post-operative outcomes (Walsh et al 2013. PMID 23835589).

For the 80-90% of routine cases (Lam et al 2021. PMCID 8483407), standard intermittent non-invasive blood pressure using oscillometry via brachial cuff is sufficient. In these cases, oscillometry blood pressures show relatively good correlation with invasively obtained blood pressures. However, when patients begin exhibiting hypotension or hypertension, non-invasive blood pressures appear to systematically over- or under- estimate blood pressures, respectively (Lehman et al 2013. PMCID 3724452).

Thus, in the remaining 10-20% of cases, more acurate "invasive" blood pressure monitoring is implemented. One common procedure is radial artery catheterization where a plastic catheter is directly inserted into the artery. From here, blood pressure is transduced outside the body and converted into an electrical signal where it can be analyzed and continuously monitored (Saugel et al 2020. PMCID 7183114).

^{Image of a radial artery catheter adapted from Xiong et al 2022 (PMCID 8905752).}

Patients are selected as needing continuous blood pressure monitoring when they are critically ill, have major comorbidities, or are undergoing a major or extended procedure.

In sum, in the United States, it is estimated that 10-20% of surgical procedures involve continuous invasive blood pressure monitoring.

Answer 2

In certain cases an arterial line can be placed to allow continuous pressure monitoring.

Tiru, B., J. A. Bloomstone, and W. T. McGee. "Radial artery cannulation: a review article." J Anesth Clin Res 3.5 (2012): 1000209.