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Venous access in small infants is difficult and central venous catheter placed into the brachiocephalic vein is often the preferred approach. Ultrasound guided vein cannulation is standard practice and endocavitary electrocardiography is a reliable catheter tip location method. We report a not immediately recognised 2 month old case of inadvertent intra-arterial catheterisation with a 3 Fr - 8 cm catheter during right innominate vein cannulation under ultrasound guidance. Endocavitary electrocardiography showed an increased amplitude P wave with a low P/R wave ratio but further insertion of the catheter resulted in a reduction of the P wave amplitude. At ultrasound re-evaluation of the innominate vein, the catheter seemed to be inside the vessel into the proximal part of the vein, but distally appeared to surpass the vein to get into the brachiocephalic artery at the level of the bifurcation of the right common carotid artery and the right subclavian artery. Cardiac ultrasound from the suprasternal notch view identified the catheter into the aortic arch. Contrast-enhanced CT scan with 3D reconstruction confirmed the intra-arterial catheterisation and showed that the innominate vein was shifted and partially compressed but not transfixed by the catheter. The catheter was non-surgically removed uneventfully. During innominate vein cannulation the catheter cannot always be visualised into the distal tract of the vein and the maximal P wave may have a low P/R ratio; a chest X-ray can identify intra-arterial but false negative results are possible. We recommend always using a real time ultrasound tip navigation and location protocol, like the Neo-ECHOTIP protocol, to confirm the correct position of the guidewire and the catheter. If the catheter cannot be identified inside the venous system, we suggest systematically visualising the aortic arch from the suprasternal notch view and the aortic root from the parasternal view to identify arterial malposition., Competing Interests: Declaration of conflicting interestsThe author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Introduction: Intra-abdominal hypertension is common in critically ill patients and is associated with increased severity of organ failure and mortality. The techniques most commonly used to estimate intra-abdominal pressure are measurements of bladder and gastric pressures. The bladder technique requires that the bladder be infused with a certain amount of saline, to ensure that there is a conductive fluid column between the bladder and the transducer. The aim of this study was to evaluate the effect of different volumes and temperatures of infused saline on bladder pressure measurements in comparison with gastric pressure., Methods: Thirteen mechanically ventilated critically ill patients (11 male; body mass index 25.5 +/- 4.6 kg/m2; arterial oxygen tension/fractional inspired oxygen ratio 225 +/- 48 mmHg) were enrolled. Bladder pressure was measured using volumes of saline from 50 to 200 ml at body temperature (35 to 37 degrees C) and room temperature (18 to 20 degrees C)., Results: Bladder pressure was no different between 50 ml and 100 ml saline (9.5 +/- 3.7 mmHg and 13.7 +/- 5.6 mmHg), but it significantly increased with 150 and 200 ml (21.1 +/- 10.4 mmHg and 27.1 +/- 15.5 mmHg). Infusion of saline at room temperature caused a significantly greater bladder pressure compared with saline at body temperature. The lowest difference between bladder and gastric pressure was obtained with a volume of 50 ml., Conclusion: The bladder acts as a passive structure, transmitting intra-abdominal pressure only with saline volumes between 50 ml and 100 ml. Infusion of a saline at room temperature caused a higher bladder pressure, probably because of contraction of the detrusor bladder muscle.