Improving the safety of resuscitative endovascular balloon occlusion of the aorta - Compliant versus semi-compliant balloon systems.

OBJECTIVES: Resuscitative endovascular balloon occlusion of the aorta is an alternative to resuscitative thoracotomy in non-compressible torso haemorrhage. Low-profile, compliant balloon catheter systems have been developed, which can be deployed without the need for fluoroscopy. However, concern exists for over inflation and aortic injury, especially as compliant balloon material can stretch reducing syringe feedback and limiting the effectiveness of a safety valve. An alternative material would be a semi-compliant balloon material, but its performance is unknown. The aim of this study was to compare the inflation characteristics of compliant versus semi-compliant balloon systems and to determine whether a pressure relief safety valve can be practically applied to a semi-compliant balloon catheter as a safety device. METHODS: This was an ex vivo study using porcine segments of thoracic aorta. The study consisted of two phases. The first phase involved intermittent inflation of six compliant balloon and six semi-compliant balloon balloons until balloon or aortic rupture. In the second phase, six semi-compliant balloons with the pressure-relief valve set at 0.45 atmospheres were inflated in the aortas until the valve release, followed by injection with additional 30 mL. Data including pressure, volume, balloon working length, diameter and circumferential stretch ratio were collected. RESULTS: At failure, mean balloon volume was almost double in compliant balloon group vs semi-compliant balloon group - 49.83 mL (±23.25) and 25.16 mL (±8.93), respectively (p = 0.004), with 36% increase in working length in the compliant balloon group - 81.17 mm (±19.11) vs 59.49 (±4.86) for semi-compliant balloon (p = 0.023). When plotted, the relationship pattern between volume and pressure fit a linear model for the compliant balloon, and a quadratic model for the semi-compliant balloon. Following attempted over inflation with the pressure valve, there was no change in parameters before and after attempted over inflation. CONCLUSIONS: The inflation profile differs between balloon designs. In contrast to semi-compliant balloons, compliant balloons will accommodate more volume to mitigate increase in pressure. This does not completely eliminate the risk of over inflation. The inflation characteristics of the semi-compliant balloon permit pairing it with a safety valve, which could lead to a development of a safer balloon technology in the future.

Erythrocyte mean corpuscular volume as a surrogate marker for 6-thioguanine nucleotide concentration monitoring in patients with inflammatory bowel disease treated with azathioprine or 6-mercaptopurine.

Mean corpuscular volume may correlate with erythrocyte 6-thioguanine nucleotide concentrations in patients treated with azathioprine and 6-mercaptourine. We conducted a study of 166 patients with inflammatory bowel disease treated with azathioprine or 6-mercaptopurine to determine the relationship between mean corpuscular volume and erythrocyte 6-thioguanine nucleotide concentrations, disease activity as measured by the Inflammatory Bowel Disease Questionnaire (active disease <170, remission >170), and leukopenia. Blood was submitted for mean corpuscular volume, whole blood 6-thioguanine nucleotide concentration, and leukocyte count. The mean +/- SD mean corpuscular volume during treatment was 94.7 +/- 6.6 fL and the mean +/- SD change in mean corpuscular volume was 7.5 +/- 6.3 fL. There were significant correlations between mean corpuscular volume and erythrocyte 6-thioguanine nucleotide concentration (r(s) = 0.33, p < 0.001) and between change from baseline in mean corpuscular volume and erythrocyte 6-thioguanine nucleotide concentration (r(s) = 0.26, p = 0.001). There was no correlation between Inflammatory Bowel Disease Questionnaire scores and mean corpuscular volume values (r(s) = 0.01, p = 0.94). The mean corpuscular volume values in 55 patients with active disease and 111 patients in remission were similar (95.1 vs. 94.5 fL, p = 0.57). There was a weak negative correlation between the mean corpuscular volume and the leukocyte count, (r(s) = -0.18, p = 0.022). In patients with inflammatory bowel disease treated with azathioprine or 6-mercaptopurine, mean corpuscular volume and change from baseline in mean corpuscular volume correlated with erythrocyte 6-thioguanine nucleotide concentrations and negatively with leukocyte counts, but did not correlate with disease activity as measured by the Inflammatory Bowel Disease Questionnaire. Measurement of mean corpuscular volume is a simple and inexpensive alternative to measurement of 6-thioguanine nucleotide concentrations in patients treated with azathioprine or 6-mercaptopurine.