Surfactant can be effectively delivered via a vascular catheter, and this method of MIST deserves further investigation.

P Pu ur rp po os se e: : To evaluate the risk of retrograde embolization of flush solution in neonates and infants with routinely used electronic syringe pumps and infusion bag pump flush systems.

Saline tonometry has been replaced by automated air tonometry (TONOCAP ® ). As with saline tonometry there are some pitfalls to consider. We investigated the influence of different filling handicaps to the tonometry catheter sampling balloon on measurement of regional PCO 2 (PrCO 2 ). In an in vitro set-up, PrCO 2 was measured using the TONOCAP ® at intervals of 10 minutes from a 8F tonometry catheter sampling balloon placed in a container with constant PCO 2 (PcCO 2 ). Catheter alarms displayed by the TONOCAP® device were noted. The following experiments were performed: A) control measurement without modifications; B) adding deadspace of 7 ml into the sampling line; C) placing the sampling balloon in a 3 ml syringe; D) cross-clamping of the sampling balloon. Each experiment was performed four times using two catheters on two TONOCAP ® devices. Differences between PcCO 2 and PrCO 2 were calculated as Pc-rCO 2. Results are presented as mean±SD and were compared using ANOVA with Scheffe's correction. Pc-rCO 2 in the control set-up (A) amounted to 0.16±0.22%. Increasing catheter deadspace (B) resulted in a higher Pc-rCO 2 of 3.2±0.57% (P<0.0001). Restriction of balloon expansion (C) caused an Pc-rCO 2 gap of 1.17±0.36% (P<0.0001). With filling restriction (D) the Pc-rCO 2 gap increased to 3.87±0.29% (P<0.0001). The catheter alarms provided were not able to indicate all catheter problems and initial alarms disappeared although the problems continued. We conclude that impaired catheter deadspace to balloon volume relation can negatively influence accuracy of PrCO 2 measurement by the TONOCAP ®.

Infusion solutions can be significantly warmed by syringe pumps. This has potential impact on bacterial growth and the stability of drug solutions and blood products infused, as well as on the susceptibility to hydrostatic pressure changes within the infusion syringe.

Fast bolus flushing from pressurized infusion bag systems, using the flow regulating device tested, can be applied during neonatal and paediatric anaesthesia without delivering uncontrolled amounts of fluid.

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Based on data about critical flow velocities through an radial arterial cannula in neonates, both tested flushing systems carry the risk of exceeding the critical value of 0.5 ml/s. They are likely to cause retrograde embolization of flushing solution into the central arterial circulation with the associated risk of clot and air embolization. In vivo studies should identify margins of safety to minimize the risk of retrograde flushing into the central arterial circulation.