In this way, intraoperative blood pressure monitoring is more accurate...

As one of the six intraoperative vital signs monitoring indicators recommended by ASA, blood pressure monitoring is undoubtedly the top priority and the focus of intraoperative management for anesthesiologists
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Generally speaking, blood pressure fluctuation is a comprehensive reflection of multiple dimensions; combined with heart rate changes, it can reflect heart function, blood volume or vascular tension; combined with peripheral finger pulse oxygen changes, it can also reflect tissue perfusion to a certain extent; blood pressure monitoring The results directly affect the choice of clinical anesthesia, and the operation should be as accurate as possible
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How to make blood pressure monitoring more accurate? This topic is more complicated, including patient factors, machine factors, human factors and so on
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I tried to explain two common blood pressure monitoring principles and explore the errors caused by some controllable factors during the operation, which may make the results more accurate
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There are two types of blood pressure monitoring most commonly used clinically, automatic intermittent non-invasive blood pressure (NIBP) and invasive continuous monitoring (ABP)
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(1) Most NIBP measurement principles use oscillation technology.
During the deflation of the cuff, the pulsation that can be detected goes from weak to strong, and then disappears; the machine detects the maximum pulsation first, and the blood pressure at this time is determined as the mean arterial pressure.
(MAP), and then determine the systolic blood pressure in the first half of the beat of the MAP, usually defined at the pressure value of 25-50% of the maximum beat (the algorithm of each manufacturer will be different); and the diastolic blood pressure of the non-invasive blood pressure is Then look for the pressure corresponding to 75% of the peak pulsation (different from each plant); therefore, the MAP value in non-invasive blood pressure measurement is the most reliable, and this also explains why the non-invasive systolic blood pressure is often lower than the invasive systolic blood pressure
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(2) Invasive blood pressure, also known as direct blood pressure monitoring, can continuously monitor the arterial waveform, and adjust the zero at the appropriate position to get the most accurate blood pressure; the best zero point is generally at the root of the aorta, which is 5cm from the posterior edge of the sternum , The zero position of invasive blood pressure directly affects blood pressure results
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The systolic blood pressure and the diastolic blood pressure correspond to the highest and lowest points of the arterial waveform, and the invasive MAP is equal to the area under the arterial pressure curve divided by the heartbeat time, and the average value of multiple cardiac cycles is taken; the invasive blood pressure is the most accurate, but the prerequisite is Appropriate zero position
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In the supine position, the automatic non-invasive blood pressure measurement is very close to the direct measurement of the mean arterial pressure MAP, especially when the MAP is 75mmHg or lower; but the oscillation method often underestimates the systolic blood pressure and overestimates the diastolic blood pressure, and significantly underestimates the calculated pulse pressure
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--When P1219 of the eighth edition of Miller Anesthesiology is in the lateral position, studies have shown that non-open thoracic upper limb non-invasive arterial pressure and invasive arterial pressure have a better linear correlation in thoracic lateral position surgery.
When MAP In the range of 70~100mmHg, it can reflect blood pressure changes as effectively as invasive arterial pressure, but direct arterial monitoring is more accurate when it is higher or lower than this range [1].
For similar results, see upper limb non-invasive blood pressure measurement in the lateral position.
How big is the error? When performing intra-arterial blood pressure monitoring, a non-invasive blood pressure cuff can be placed to compare the two measurements, and at the same time as a backup monitoring in the event of technical problems
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After inserting the arterial catheter, zeroing the sensor and adjusting the position, we will measure the non-invasive blood pressure (expected that the average blood pressure of invasive and non-invasive monitoring is similar), and make adjustments if necessary; then we set the non-invasive blood pressure cuff to It is measured every 30 minutes
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--From UpToDate's summary of the above suggestions: 1.
In non-invasive blood pressure monitoring, the assessment should be based on MAP as much as possible; 2.
In the lateral position, non-invasive blood pressure should be monitored on the non-operative side (lower side), and the error is smaller; 3.
In view of most In this case, non-invasive MAP is equivalent to invasive arteries, and non-invasive MAP can be used to guide the zero point adjustment of invasive arteries to ensure the accuracy of invasive arterial monitoring; 4.
During invasive arterial monitoring, longer intervals of non-invasive blood pressure can provide a control.
Further reduce errors
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References: [1] Liu Aijie, Liu Guoqiang, Wang Shiduan, et al.
Comparison of bilateral upper limb non-invasive blood pressure and invasive blood pressure during lateral decubitus surgery in thoracic patients[J].
Journal of Clinical Anesthesiology, 2011.
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