Cardiovascular Monitoring during Anesthesia. 台大醫院麻醉部 詹偉弘. Electrocardiogram (EKG). One of the standardized monitors during any form of anesthesia. For detection and diagnosis of dysrhythmias conduction defects cardiac ischemia electrolyte disturbance. Types of Monitoring.
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One of the standardized monitors during any form of anesthesia.
For detection and diagnosis of
Three-electrode system: right arm, left arm, left leg; white is always right, black is on the left, red is even lower.
Kaplan et al. (Anesthesiology, 1976):
90% of intraoperative cardiac ischemia will be detected by multiple EKG, especially V5. At least two leads should be simultaneously showed on the monitor.
1. Monitoring mode: 0.5~40 Hz, eliminates high and low frequency artifacts, but distorts the height of QRS and the degree of ST depression.
2. Diagnostic mode: 0.05~100 Hz, does not filter high frequency artifacts.
1) Auscultation of Korotkoff sounds
2) Microprocessor-assisted interpretation of
from Barbara Bates: A Guide to Physical Examination
Damping is necessary.
: density of the fluid; P/V: compliance
Overestimation of SBP and under-estimation of DBP.
1)Low-frequency responses: Air in line or failure in flush device with formation of partial clot in catheter. Over-damping.
2)Catheter whip: Motion of catheter tip itself produces a noticeable pressure swing; not common in A-line but common in PA catheter.
3)Resonance in peripheral vessels: The systolic pressure measured in a radial artery may be up to 20~50 mmHg higher than in the central aorta.
4)Change in electronic balance: electronic zeroing should be done periodically to preclude baseline drift (for example: due to change in room temperature).
5)Transducer position error: ideally at right atrium. (Midaxillary line in supine patients.) Changes may be less significant in blood pressure but significant in CVP or PA pressure/wedge pressure.
Apply pressure over both radial and ulnar arteries simultaneously and ask the patient to squeeze his or her hand several times to promote exsanguination. Then release the pressure on the ulnar side and measure the time for refill of the nailbed of the capillary. If refill time is greater than 15 sec, it is a positive test, indicating inadequate collateral flow.
It can measure:
Usual conditions (just for ease to memorize)
O2 consumption= SaO2-SvO2
SvO2=SaO2 - (VO2/Q x Hb x 13)
Causes for decreasing SvO2:
A vibrating piezoelectric crystal at the probe tip both produces and receives the ultrasound wave. The time required for the wave to travel through biological structures, together with the intensity of reflected waves, provides information about the size and the intensity of the structures.
V = fc/2f0 x cos
Color flow mapping:
Peak pressure gradient can be calculated by a modified Bernoulli equation:
P = 4 x V2
Mitral Area = 220/ T 1/2
Aortic short-axis view