ĐO HA ĐỘNG MẠCH XÂM LẤN

 The systemic arterial pressure waveform results from ejection of blood from the left ventricle into the aorta during systole, followed by peripheral arterial runoff of this stroke volu

ĐO HA ĐỘNG MẠCH XÂM LẤN

Chia thành 3 nhóm chính:

1 Không đo được huyết áp động mạch không xâm lấn

2 Cần theo dõi huyết áp động mạch liên tục:

1 Bệnh lý cần theo dõi huyết động liên tục

2 Phẫu thuật hay thủ thuật trên tim, mạch

3 Lấy máu xét nghiệm liên tục (khí máu)

Chỉ định

NIHON

 Nối module vào máy Nihon Kohden tại vị trí Press1

 Nối module vào máy Spacelabs tại T1-2

◦ Pha heparin 1000Ul (0,2ml heparin) vào dung dịch NaCl 0,9% 500ml

◦ Khóa dây dịch truyền,

cắm bầu chứa vào chai

Nacl

◦ Xả dịch vào khỏang

1/3bầu

◦ Mở khóa và xả đuổi khí trong hệ thống day, sau đó khóa lại

◦ Đặt chai dịch vào túi áp lực và treo lên giá

◦ Nối dây vào dây nối của tranducer

◦ Mở 3 chia

◦ Bóp nhẹ khóa màu xanh để làm dịch chảy qua

tranducer

◦ Tiếp tục bóp nút xanh để cho dịch chảy vào hệ thống day nối dài để đuổi khí

◦ Bơm túi tạo áp lực lên mức

300 mmHg, với áp lực trên, tốc độ dịch là 2-4 ml/giờ,

◦ Pha 50 ml NS + 0,02 ml

heparin

◦ Gắn vào đầu dưới tranducer

◦ Tăng tốc độ bơm để đuổi khí trong hệ thống dây

◦ Tốc độ duy trì 2ml/giờ

◦ Nối dây đo áp lực vào nắp chụp sao cho that khít

◦ Kiểm tra lại tất các

mối nối

◦ Di chuyển sao cho đầu thóat khí của 3 chia

ngang với nhĩ phải và mở 3 chia cho tiếp xúc với không khí

◦ Điều chỉnh mức 0 trên máy:

 Nhấn nut Press all zero ở góc trái trên màn hình

 Nhấn menu  press  å P1scale/zero cal  zero calibration

• Khóa 3 chia lại

 Máy đã sẵn sàng đo áp lực động mạch

◦ Điều chỉnh giới hạn báo

 Nhấn nut  để điều chỉnh

◦ Nhấn home để kết thúc

◦ Cài đặt chế độ hiển thị:

 Nhấn menu  press  other setting

 Nhấn S/D (M): chọn hiển thị HA tâm thu /tâm

trương và trung bình

 Nhấn M: chỉ hiển thị HA trung bình

◦ Nhấn home để kết thúc

1. Thiếu máu nuôi

2. Huyết khối

3. Chảy máu

4. Nhiễm trùng

5. Tổn thương thần kinh

 Dynamic response

 frequency at which it oscillates when stimulated

 Physiologic peripheral arterial waveforms have a

fundamental frequency of 3 to 5 Hz, although some

components may range up to 20 Hz [46]

 Thus, the resonant frequency of the system used to monitor arterial pressure must be greater than 20 Hz to avoid ringing and systolic overshoot [47]

 is a measure of how quickly an oscillating system comes to rest [47]

 A system with a high damping coefficient (eg, compliant tubing) absorbs mechanical energy well and causes a diminution in the transmitted waveform

 Common causes of underdamping include connecting tubing with stopcocks, excessive tubing lengths, and patient factors (eg,

tachycardia, high output states)

 A common cause of overdamping is air

bubbles in the connecting tubing

 The systemic arterial pressure waveform results from ejection of blood from the left ventricle into the aorta during systole, followed

by peripheral arterial runoff of this stroke volume during diastole (

Fig 40-11 )

 The systolic components follow the ECG R wave and consist of a steep pressure upstroke, peak, and decline and correspond to the period of left ventricular systolic ejection

 The downslope of the arterial pressure waveform is interrupted by the dicrotic notch, then continues its decline during diastole after the ECG T wave, and reaches its nadir at end-diastole

 The dicrotic notch recorded directly from the central aorta

is termed the incisura (from the Latin, “a cutting into”)

The incisura is sharply defined and is undoubtedly related

to closure of the aortic valve [ 61 ]

 In contrast, the peripheral arterial waveform generally

displays a later, smoother dicrotic notch that only

approximates the timing of aortic valve closure and

depends more on properties of the arterial wall

 Note that the systolic upstroke of the radial artery pressure

trace does not appear for 120 to 180 msec after inscription of the ECG R wave (see Fig 40-11 ) This interval reflects the sum

of times required for spread of electrical depolarization through the ventricular myocardium, isovolumic left ventricular

contraction, opening of the aortic valve, left ventricular ejection, transmission of the aortic pressure wave to the radial artery,

and finally, transmission of the pressure signal from the arterial catheter to the

 If the monitoring system has a natural

frequency that is too low, frequencies in the

monitored pressure waveform will overlap the natural frequency of the measurement system

As a result, the system will resonate and

pressure waveforms recorded on the monitor will be exaggerated or amplified versions of

true intra-arterial pressure ( Fig 40-4 ) This

phenomenon is the familiar arterial pressure waveform that displays overshoot, ringing, or resonance In these instances, the recorded

systolic blood pressure overestimates true

intra-arterial pressure

 Most catheter-transducer systems are underdamped but have an acceptable natural frequency that exceeds 12 Hz If the system's natural frequency is lower than 7.5 Hz, the pressure waveform is often distorted, and no amount

of damping adjustment can restore the monitored waveform to adequately resemble the original waveform [47] If, on the other hand, the natural

frequency can be increased sufficiently (e.g., 24 Hz), damping will have

minimal effect on the monitored waveform, and faithful reproduction of

intravascular pressure is achieved more easily (Figs 40-6 and 40-7 [ 0060 ] [ 0070 ]) In other words, the lower the natural frequency of the monitoring system, the more narrow the range of damping coefficients that can be

tolerated to ensure faithful reproduction of the pressure wave For example,

if the monitoring system's natural frequency is 10 Hz, the damping

coefficient must be between 0.45 and 0.6 for accurate monitoring of the

pressure waveform If the damping coefficient is too low, the monitoring system will be underdamped, resonate, and display factitiously elevated systolic blood pressure; if the damping coefficient is too high, the system will be overdamped, systolic pressure will be falsely decreased, and fine detail in the pressure trace will be lost

 From these considerations it follows that a pressure monitoring system will have optimal dynamic response if its natural frequency is as high as possible [ 51 ] In theory, this is best achieved by using short lengths of stiff pressure tubing and limiting the number of stopcocks and other monitoring system appliances Blood clots and air bubbles trapped and concealed in stopcocks and other connection points will have similar adverse influences on the system's dynamic response

As a general rule, adding air bubbles to monitoring systems will not improve their dynamic response because any increase in system damping is always

accompanied by a decrease in natural frequency

 To assess the amount of distortion existing in

a pressure monitoring system, the fast-flush test provides a convenient bedside method for determining the system's dynamic response.

[ 47 ] [ 49 ] [ 51 ] To perform this test, the fast-flush

valve is opened briefly, and the resulting flush artifact is examined Natural frequency is

inversely proportional to the time between

adjacent oscillation peaks It can be calculated

as 1 cycle/1.7 mm × 25 mm/sec = 14.7

cycles/sec (14.7 Hz) ( Fig 40-9 ) Monitoring

systems with shorter oscillation cycles will

have higher natural frequencies

 when blood pressure is lower in one arm than in the other or when the pulses are weaker on one side, one should never insert an arterial catheter on the side with the weaker pulse because determination of blood pressure from this site will probably underestimate true aortic pressure In addition to atherosclerosis, other pathologic conditions such as arterial dissection or embolism preclude accurate monitoring of

pressure from the affected sites