Invasive and ultrasound based monitoring of the intracranial pressure in an experimental model of epidural hematoma progressing towards brain tamponade on rabbits.

INTRODUCTION: An experimental epidural hematoma model was used to study the relation of ultrasound indices, namely, transcranial color-coded-Doppler (TCCD) derived pulsatility index (PI), optic nerve sheath diameter (ONSD), and pupil constriction velocity (V) which was derived from a consensual sonographic pupillary light reflex (PLR) test with invasive intracranial pressure (ICP) measurements. MATERIAL AND METHODS: Twenty rabbits participated in the study. An intraparenchymal ICP catheter and a 5F Swan-Ganz catheter (SG) for the hematoma reproduction were used. We successively introduced 0.1 mL increments of autologous blood into the SG until the Cushing reaction occurred. Synchronous ICP and ultrasound measurements were performed accordingly. RESULTS: A constant increase of PI and ONSD and a decrease of V values were observed with increased ICP values. The relationship between the ultrasound variables and ICP was exponential; thus curved prediction equations of ICP were used. PI, ONSD, and V were significantly correlated with ICP (r² = 0.84 ± 0.076, r² = 0.62 ± 0.119, and r² = 0.78 ± 0.09, resp. (all P < 0.001)). CONCLUSION: Although statistically significant prediction models of ICP were derived from ultrasound indices, the exponential relationship between the parameters underpins that results should be interpreted with caution and in the current experimental context.

Changes in arterial blood flow of free flaps after the administration of sildenafil in swine.

We evaluated blood flow changes after experimental free tissue transfer and the potential hemodynamic effect of sildenafil on the free flap. Sixteen swine were used for free transfer of a latissimus dorsi myocutaneous flap to the chest that was anastomosed to the internal mammary vessels, and were randomized into controls and study group. The latter received a single dose of sildenafil, 6 hours following flap revascularization. Doppler ultrasonography revealed that arterial flow was mainly systolic postoperatively. Diastolic flow patterns were gradually restored after the first postoperative day. Pulsatility index (PI) significantly increased and flow volume decreased in all animals postoperatively. In the sildenafil group, PI significantly decreased and flow volume increased, while diastolic flow patterns were restored earlier on compared to controls, postoperatively. In conclusion, the administration of sildenafil after free tissue transfer increases flow volume and facilitates the restoration of diastolic blood flow patterns in the early critical postoperative period.