Retrospectively doing this, intraoperative blood pressure monitoring is more accurate...

As one of the six major intraoperative vital signs monitoring indicators recommended by ASA, blood pressure monitoring is undoubtedly the top priority, and it is also the focus of anesthesiologists' intraoperative management
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Generally speaking, the fluctuation of blood pressure is a comprehensive reflection of multiple dimensions; combined with heart rate changes, it can reflect cardiac function, blood volume or vascular tension; combined with changes in peripheral finger pulse oxygen, it can also reflect tissue perfusion to a certain extent; blood pressure monitoring The results of the clinical anesthesia directly affect the choice of clinical anesthesia, and should be as precise as possible during the operation
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How to make blood pressure monitoring more accurate? This topic is complex and includes patient factors, machine factors, human factors, and more
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I try to explain the two common blood pressure monitoring principles and explore the errors caused by some controllable factors in blood pressure monitoring during surgery, which may make the results more accurate
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There are two types of blood pressure monitoring most commonly used in clinical practice today, 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 process of deflating the cuff, the detectable pulsation varies 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 MAP beat, which is usually defined at the pressure value of 25-50% of the maximum beat (algorithms of various manufacturers will vary); while the diastolic blood pressure of non-invasive blood pressure is a Then find the pressure corresponding to 75% of the pulsatile peak value (there are differences between factories); therefore, the MAP value in non-invasive blood pressure measurement is the most reliable, and this also explains why non-invasive systolic blood pressure is often lower than 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 zeroing at a suitable position can obtain the most accurate blood pressure; the best zeroing point is generally at the aortic root, that is, at the level of 5cm behind the sternum.
, the zero-point position of invasive blood pressure directly affects blood pressure results
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Systolic blood pressure and diastolic blood pressure correspond to the highest and lowest points of the arterial waveform, respectively, and invasive MAP is equal to the area under the arterial pressure curve divided by the heartbeat time, taking the average of multiple cardiac cycles; invasive blood pressure is the most accurate, but the precondition is Appropriate zero position
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In the supine position, automated non-invasive blood pressure measurements are very close to directly measured mean arterial pressure MAP, especially when MAP is 75 mmHg or lower; however, the oscillatory method often underestimates systolic and diastolic blood pressure, and significantly underestimates calculated pulse pressure
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-- "Miller Anesthesiology" Eighth Edition P1219 In the lateral position, studies have shown that the linear correlation between non-invasive arterial pressure and invasive arterial pressure in the non-thoracotomy side of the upper extremity in thoracic lateral decubitus surgery is better, when MAP In the range of 70-100 mmHg, 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].
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 as a backup monitor in the event of technical problems
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After the arterial catheter is placed, the sensor is zeroed, and the position is adjusted, we measure the non-invasive blood pressure (expected to have similar mean blood pressure values ​​for invasive and non-invasive monitoring), and make adjustments if necessary; we then set the non-invasive blood pressure cuff to Measure every 30 minutes
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--From UpToDate to summarize the above recommendations: 1.
In non-invasive blood pressure monitoring, the assessment should be based on MAP as much as possible; 2.
In lateral recumbency, non-invasive blood pressure should be monitored on the non-surgical side (lower side), with smaller errors; 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.
In the process of invasive arterial monitoring, non-invasive blood pressure with longer intervals can provide a control further reduce errors
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References: [1] Liu Aijie, Liu Guoqiang, Wang Shiduan, et al.
Comparison of non-invasive and invasive blood pressure of bilateral upper extremities in thoracic patients in lateral decubitus position [J].
Journal of Clinical Anesthesiology, 2011.
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