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

Shara WY Lee, Kim S Khaw, Warwick D Ngan Kee

Michael TC Ying, Stella SY Ho

Department of Anaesthesia & Intensive CareDepartment of Diagnostic Radiology & Organ ImagingThe Chinese University of Hong Kong

Department of Health Technology & InformaticsThe Hong Kong Polytechnic University





A new method for detecting inferior vena cava compression in term parturients

Annual Scientific Meeting in Anaesthesiology 2006 – 18th ~ 19th November 2006 (HKCEC) 11

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

22

Effects of inferior vena cava compression

Compensatory mechanisms:

Maternal Heart rate Systemic 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

33

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

44


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)

55


All the methods required complicated setupsAll the methods required complicated setups

No convenient and non-invasive bedside technique available to detect aortocaval compression

66

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.

77

Venous phasicity test - Principles

Presence of phasicityPresence of phasicity

88

Venous phasicity test - Principles

Absence of phasicityAbsence of phasicity

99

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

1010

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)

1111

Femoral vein US Image

Colour-flow Colour-flow USUS

Aortic/IVC Aortic/IVC CompressionCompression

Doppler USDoppler USFemoral veinFemoral vein

Finometer Finometer NIBP & CO

PortapresPortapresDetects aortic compression

Dinamap Dinamap NIBP (Right arm)

DatexDatex NIBP (Right calf)NIBP (Right calf)

USCOM USCOM Cardiac Output

1212

Inferior vena cava

Abdominal aorta

Spine

Direct Abdominal scan of aorta / IVC

1313

Direct abdominal scan of aorta / IVC

Supine position 15 degrees tilt

Difference in size /colour-filling of vessel

1414

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 cmH2O 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 cmH2O PEEP valve)

Loss of phasicity Presence of IVC compressionLoss of phasicity Presence of IVC compression

1515

Quiet breathing

Supine position 15 degrees tilt

Difference in respiratory phasicity at different tilts

1616

Forced breathing

Presence of phasicity (No obstruction)

Absence of phasicity (IVC obstruction)

1717

Valsalva Manoeuvre

1818

Results:

Pos CO HR/SVR IVC NB FB VAL Status

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

HaemodynamicsHaemodynamics Patency / Phasicity testPatency / Phasicity test IVC statusIVC statusPosition

1919

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

2020

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

2121

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

2222

- The End - Annual Scientific Meeting in

Anaesthesiology 2006








Department of Health Technology & InformaticsThe Hong Kong Polytechnic University 2323

Documents

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