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Shara WY Lee, Kim S Khaw, Warwick D Ngan Kee Michael TC Ying, Stella SY Ho Department of Anaesthesia & Intensive Care Department of Diagnostic Radiology.

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Presentation on theme: "Shara WY Lee, Kim S Khaw, Warwick D Ngan Kee Michael TC Ying, Stella SY Ho Department of Anaesthesia & Intensive Care Department of Diagnostic Radiology."— Presentation transcript:

1 Shara WY Lee, Kim S Khaw, Warwick D Ngan Kee Michael TC Ying, Stella SY Ho Department of Anaesthesia & Intensive Care Department of Diagnostic Radiology & Organ Imaging The Chinese University of Hong Kong Department of Health Technology & Informatics The Hong Kong Polytechnic University Shara WY Lee, Kim S Khaw, Warwick D Ngan Kee Michael TC Ying, Stella SY Ho Department of Anaesthesia & Intensive Care Department of Diagnostic Radiology & Organ Imaging The Chinese University of Hong Kong Department of Health Technology & Informatics The Hong Kong Polytechnic University A new method for detecting inferior vena cava compression in term parturients Annual Scientific Meeting in Anaesthesiology 2006 – 18 th ~ 19 th November 2006 (HKCEC) 1 1

2 Aortocaval Compression in Pregnancy Compression of abdominal aorta & inferior vena cava by the gravid uterus Positioning of parturient – to minimize haemodynamic disturbance Compression of abdominal aorta & inferior vena cava by the gravid uterus Positioning of parturient – to minimize haemodynamic disturbance 2 2

3 Effects of inferior vena cava compression Compensatory mechanisms: Maternal Heart rateSystemic vascular resistance Collateral circulation: azygous vein, vertebral plexus & epidural venous plexus Compression of IVC by gravid uterus Venous return to heart Right atrial pressure / Preload / CO / SV Uterine blood flow Fetal compromise 3 3

4 Established methods to detect ACC Directly: Angiography to visualize aortic compression Venography - Presence of collateral circulations  Azygous vein, vertebral plexus & epidural venous plexus Less invasive modalities  MRI, CT  Abdominal US scan Directly: Angiography to visualize aortic compression Venography - Presence of collateral circulations  Azygous vein, vertebral plexus & epidural venous plexus Less invasive modalities  MRI, CT  Abdominal US scan 4 4

5 Established methods to detect ACC Indirectly: Detection of femoral / brachial hypotension  Gradient of BP femoral artery vs. BP brachial artery   BP femoral artery >  BP brachial artery Haemodynamic disturbance   Cardiac Output  Compensatory mechanisms (  Heart rate and SVR) Indirectly: Detection of femoral / brachial hypotension  Gradient of BP femoral artery vs. BP brachial artery   BP femoral artery >  BP brachial artery Haemodynamic disturbance   Cardiac Output  Compensatory mechanisms (  Heart rate and SVR) 5 5

6 Established methods to detect ACC All the methods required complicated setups No convenient and non-invasive bedside technique available to detect aortocaval compression 6 6

7 Study Objective To develop an easier bedside method for detecting inferior vena cava compression in parturients We hypothesize that: Observing for phasic blood flow in the femoral vein using ultrasound can be used to detect inferior vena cava compression in term parturients. 7 7

8 Venous phasicity test - Principles Presence of phasicity 8 8

9 Venous phasicity test - Principles Absence of phasicity 9 9

10 Methods Clinical Research Ethics Committee Approval Informed written consent 10 ASA I-II term parturients Before elective Caesarean section Clinical Research Ethics Committee Approval Informed written consent 10 ASA I-II term parturients Before elective Caesarean section 10

11 Materials and Methods Philips HDI-3000 ultrasound unit (3-5MHz curvilinear probe) Step 1: Direct insonation of abdominal aorta & IVC  Colour-flow ultrasound Step 2: Respiratory phasicity test of the femoral vein  Colour spectral Doppler ultrasound Patient positioned on tilting table (0º, left 7.5º & 15º) Philips HDI-3000 ultrasound unit (3-5MHz curvilinear probe) Step 1: Direct insonation of abdominal aorta & IVC  Colour-flow ultrasound Step 2: Respiratory phasicity test of the femoral vein  Colour spectral Doppler ultrasound Patient positioned on tilting table (0º, left 7.5º & 15º) 11

12 Femoral vein US Image Colour-flow US Aortic/IVC Compression Doppler US Femoral vein Finometer NIBP & CO Portapres Detects aortic compression Dinamap NIBP (Right arm) Datex NIBP (Right calf) USCOM Cardiac Output 12

13 Inferior vena cava Abdominal aorta Spine Direct Abdominal scan of aorta / IVC 13

14 Direct abdominal scan of aorta / IVC Supine position 15 degrees tilt Difference in size /colour-filling of vessel 14

15 Phasicity test of femoral vein To study the changes after direct abdominal insonation of IVC Respiratory phasicity test (Spectral Doppler US)  Quiet breathing  Deep breathing  Valsalva manoeuvre (15 cmH 2 O PEEP valve) To study the changes after direct abdominal insonation of IVC Respiratory phasicity test (Spectral Doppler US)  Quiet breathing  Deep breathing  Valsalva manoeuvre (15 cmH 2 O PEEP valve) Loss of phasicity  Presence of IVC compression 15

16 Quiet breathing Supine position 15 degrees tilt Difference in respiratory phasicity at different tilts 16

17 Forced breathing Presence of phasicity (No obstruction) Absence of phasicity (IVC obstruction) 17

18 Valsalva Manoeuvre 18

19 Results: PosCOHR/SVRIVCNBFBVALStatus Supine (n=3)    IVC compression Lt 7.5º (n=3)  IVC partial compression Supine (n=27) = /  = /  IVC patent Supine (n=27) = /  = /  IVC patent Lt 15º (n=30) = /  = /  IVC patent Haemodynamics Patency / Phasicity test IVC status Position 19

20 Summary: Venous phasicity of femoral vein In patients with partial IVC compression  Loss of phasicity during - Quiet breathing  Phasicity restored - Deep breathing & Valsalva  Minimal haemodynamic disturbance  Increased respiratory phasicity at 15º In patients with complete IVC compression  Loss of phasicity during - Quiet / Deep breathing & Valsalva  More severe haemodynamic disturbance Effects of lateral tilts  Phasicity restored during quiet breathing at 15º  Direct abdominal scan at ~T9 – Improved IVC patency In patients with partial IVC compression  Loss of phasicity during - Quiet breathing  Phasicity restored - Deep breathing & Valsalva  Minimal haemodynamic disturbance  Increased respiratory phasicity at 15º In patients with complete IVC compression  Loss of phasicity during - Quiet / Deep breathing & Valsalva  More severe haemodynamic disturbance Effects of lateral tilts  Phasicity restored during quiet breathing at 15º  Direct abdominal scan at ~T9 – Improved IVC patency 20

21 Conclusions Venous phasicity test – Detection of IVC compression ? Superseed abdominal scan Limitations of direct abdominal scan:  Time consuming  View obstructed by fetus (Fetal orientation)  Inadequate penetration (Gravid uterus increases depth of IVC)  Open vessel ≠ Presence of flow Venous phasicity test – Detection of IVC compression ? Superseed abdominal scan Limitations of direct abdominal scan:  Time consuming  View obstructed by fetus (Fetal orientation)  Inadequate penetration (Gravid uterus increases depth of IVC)  Open vessel ≠ Presence of flow 21

22 Conclusions Venous phasicity test:  Non-invasive, reproducible and convenient  Includes functional collateral circulation  Familiar anatomy – femoral catheters  Preliminary investigation shows feasibility  Further study to improve and modify present methodology and confirm clinical utility Venous phasicity test:  Non-invasive, reproducible and convenient  Includes functional collateral circulation  Familiar anatomy – femoral catheters  Preliminary investigation shows feasibility  Further study to improve and modify present methodology and confirm clinical utility 22

23 - The End - Annual Scientific Meeting in Anaesthesiology 2006 Shara WY Lee, Kim S Khaw, Warwick D Ngan Kee Michael TC Ying, Stella SY Ho Department of Anaesthesia & Intensive Care Department of Diagnostic Radiology & Organ Imaging The Chinese University of Hong Kong Department of Health Technology & Informatics The Hong Kong Polytechnic University Shara WY Lee, Kim S Khaw, Warwick D Ngan Kee Michael TC Ying, Stella SY Ho Department of Anaesthesia & Intensive Care Department of Diagnostic Radiology & Organ Imaging The Chinese University of Hong Kong Department of Health Technology & Informatics The Hong Kong Polytechnic University 23


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