Please see Bibliography of References for a list of abstracts, manuscripts and posters.

Microvascular Dysfunction

Exaggerated StO₂ hyperaemic response to vascular occlusion testing in cirrhosis using near infrared spectroscopy

Thomson SJ, Cowan ML, Musa S, Al-Subaie N, Hamilton M, Grounds M, Rahman TM. J Hepatology 2009;50(Suppl 1):S282.

Background and Aims: Near infrared spectroscopy (NIRS) has been utilized in recent years to assess microcirculatory dysfunction in pathophysiological states including haemorrhagic and septic shock. Through a probe placed over the thenar eminence, NIRS utilizes the differential absorption properties of haemoglobin to calculate the ratio of oxygenated and deoxygenated haemoglobin present within a defined quantity of muscle tissue. Readings are expressed as StO₂ (muscle tissue oxygenation). Using vascular occlusion testing (VOT) it is possible to induce dynamic changes in StO₂ which represent tissue oxygen extraction, delivery, and hence, a surrogate marker of vascular function. Using this non invasive technique we aimed to investigate whether there was evidence of exaggerated vascular reactivity and vasodilatation in the peripheral microcirculation of patients with cirrhosis.

Methods: StO₂ readings were obtained from 25 healthy volunteers and 24 stable out patients with cirrhosis using the InSpectra 650 monitor and 15mm thenar probe. VOT was performed with a brachial cuff and manually set at a pressure of 50mmHg above systolic for three minutes. Results are reported sequentially for StO₂ baseline (%), downslope and upslope gradients (%/min), overshoot (%), area over the ischaemic curve (AOC Isch) (%/min), area under the recovery curve (AUC Rec) (%/min) and recovery time (Min).

Results: The rate and degree of StO₂ desaturation induced by vascular occlusion was the same in both cirrhotic and normal subjects (Downslope, AOC Isch), however the hyperaemic response, as defined by overshoot and AUC Rec, was significantly exaggerated. The abnormalities identified appear to increase in magnitude with degree of hepatic decompensation.

Conclusions: It has long been suggested that the circulatory abnormalities associated with cirrhosis include peripheral vasodilatation due to a relative nitric oxide excess. Using a simple non invasive technique we have collected a truly novel dataset which supports this theory.