Area-pressure relationship of lower limb main veins in man

Peripheral Venous Pressure as an Indicator of Preload Responsiveness During Volume Resuscitation from Hemorrhage

BACKGROUND

Fluid resuscitation of hypovolemia presumes that peripheral venous pressure (PVP) increases more than right atrial pressure (RAP), so the net pressure gradient for venous return (PVP-RAP) rises. However, the heart and peripheral venous system function under different compliances that could affect their respective pressures during fluid infusion. In a porcine model of hemorrhage resuscitation, we examined whether RAP increases more than PVP, thereby reducing the venous return pressure gradient and blood flow.

METHODS

Anesthetized pigs (n = 8) were bled to a mean arterial blood pressure of 40 mm Hg and resuscitated with stored blood and albumin for pulmonary artery occlusion pressures (PAOPs) of 5, 10, 15, and 20 mm Hg. Venous pressures, inferior vena cava blood flow (ultrasonic flowprobe), and left ventricular diastolic compliance (Doppler echocardiography) were measured. Stroke volume variability was calculated.

RESULTS

With volume resuscitation, the slope of RAP exceeded PVP (P ≤ 0.0001) when PAOP is 10 to 20 mm Hg, causing the pressure gradient for venous return to progressively decrease. Inferior vena cava blood flow did not further increase after PAOP > 10 mm Hg. The E/e' ratio increased (P = 0.001) during resuscitation indicating reduced diastolic compliance. A significant curvilinear relationship was found between PVP and stroke volume variability (R = 0.62; P < 0.001), where fluid responders had PVP < 15 mm Hg.

CONCLUSIONS

Fluid resuscitation above a PAOP 10 mm Hg reduces myocardial compliance and reduces the venous return pressure gradient. The hemodynamic response to fluid resuscitation becomes limited by diastolic properties of the heart. PVP measurement during hemorrhage resuscitation may predict fluid responsiveness and nonresponsiveness.

Composite PTFE-transposed superficial femoral vein for lower limb arteriovenous access

PURPOSE

We report our experience in creating a composite loop of transposed superficial femoral vein (tSFV) and polytetrafluoroethylene (PTFE) synthetic graft for lower limb access. The indication for surgery was exhaustion of access sites in both upper limbs.

METHODS

Surgery was performed on 3 male patients. All patients had an ankle brachial index =0.9. The SFV was mobilized up to adductor canal, with ligation of all small tributary branches, up to the level below the profunda femoral vein, then tunneled medially to the skin. A 6-mm PTFE graft was tunneled laterally, deep in the subcutaneous plane in loop fashion to the end of the tSFV, where a beveled end-to-end anastomosis was created.

RESULTS

The blood flow in both fistulas increased gradually to 0.7-1.3 l/min postoperatively. No clinical manifestation indicative of lower limb ischemia, lymphorrhea, or infection was documented. No signs related to chronic venous hypertension were noticed.

CONCLUSIONS

Our initial experience shows that the creation of a composite PTFE-tSFV conduit is a promising technique, since it can be constructed without compromising the distal perfusion, and without infectious complications.