Minimising haemodynamic lability during changeover of syringes infusing norepinephrine in adult critical care patients: a multicentre randomised controlled trial

Effect of vertical stopcock position on start-up fluid delivery in syringe pumps used for microinfusions

The purpose of this in vitro study was to evaluate the impact of the vertical level of the stopcock connecting the infusion line to the central venous catheter on start-up fluid delivery in microinfusions. Start-up fluid delivery was measured under standardized conditions with the syringe outlet and liquid flow sensors positioned at heart level (0 cm) and exposed to a simulated CVP of 10 mmHg at a set flow rate of 1 ml/h. Flow and intraluminal pressures were measured with the infusion line connected to the stopcock primarily placed at vertical levels of 0 cm, + 30 cm and - 30 cm or primarily placed at 0 cm and secondarily, after connecting the infusion line, displaced to + 30 cm and - 30 cm. Start-up fluid delivery 10 s after opening the stopcock placed at zero level and after opening the stopcock primarily connected at zero level and secondary displaced to vertical levels of + 30 cm and - 30 cm were similar (- 10.52 [- 13.85 to - 7.19] µL; - 8.84 [- 12.34 to - 5.33] µL and - 11.19 [- 13.71 to - 8.67] µL (p = 0.469)). Fluid delivered at 360 s related to 65% (zero level), 71% (+ 30 cm) and 67% (- 30 cm) of calculated infusion volume (p = 0.395). Start-up fluid delivery with the stopcock primarily placed at + 30 cm and - 30 cm resulted in large anterograde and retrograde fluid volumes of 34.39 [33.43 to 35.34] µL and - 24.90 [- 27.79 to - 22.01] µL at 10 s, respectively (p < 0.0001). Fluid delivered with the stopcock primarily placed at + 30 cm and - 30 cm resulted in 140% and 35% of calculated volume at 360 s, respectively (p < 0.0001). Syringe infusion pumps should ideally be connected to the stopcock positioned at heart level in order to minimize the amounts of anterograde and retrograde fluid volumes after opening of the stopcock.

Pressure-adjusted venting eliminates start-up delays and compensates for vertical position of syringe infusion pumps used for microinfusion

Microinfusions are commonly used for the administration of catecholamines, but start-up delays pose a problem for reliable and timely drug delivery. Recent findings show that venting of the syringe infusion pump with draining of fluid to ambient pressure before directing the flow towards the central venous catheter does not counteract start-up delays. With the aim to reduce start-up delays, this study compared fluid delivery during start-up of syringe infusion pumps without venting, with ambient pressure venting, and with central venous pressure (CVP)-adjusted venting. Start-up fluid delivery from syringe pumps using a microinfusion of 1 mL/h was assessed by means of liquid flow measurement at 10, 60, 180 and 360 s after opening the stopcock and starting the pump. Assessments were performed using no venting, ambient pressure venting or CVP-adjusted venting, with the pump placed either at zero, - 43 cm or + 43 cm level and exposed to a simulated CVP of 10 mmHg. Measured fluid delivery was closest to the calculated fluid delivery for CVP-adjusted venting (87% to 100% at the different timepoints). The largest deviations were found for ambient pressure venting (- 1151% to + 82%). At 360 s after start-up 72% to 92% of expected fluid volumes were delivered without venting, 46% to 82% with ambient pressure venting and 96% to 99% with CVP-adjusted venting. CVP-adjusted venting demonstrated consistent results across vertical pump placements (p = 0.485), whereas the other methods had significant variances (p < 0.001 for both). In conclusion, CVP-adjusted venting effectively eliminates imprecise drug delivery and start-up delays when using microinfusions.

Evaluation of the venting principle to reduce start-up delays in syringe infusion pumps used for microinfusions

Start-up delays of syringe pump assemblies can impede the timely commencement of an effective drug therapy when using microinfusions in hemodynamically unstable patients. The application of the venting principle has been proposed to eliminate start-up delays in syringe pump assemblies. However, effectively delivered infusion volumes using this strategy have so far not been measured. This invitro study used two experimental setups to measure the effect of the venting principle compared to a standard non-venting approach on delivered start-up infusion volumes at various timepoints, backflow volumes, flow inversion and zero drug delivery times by means of liquid flow measurements at flow rates of 0.5, 1.0 and 2.0 mL/h. Measured delivered initial start-up volumes were negative with all flow rates in the vented and non-vented setup. Maximum backflow volumes were 1.8 [95% CI 1.6 to 2.3] times larger in the vented setup compared to the non-vented setup (p < 0.0001). Conversely, times until flow inversion were 1.5 [95% CI 1.1 to 2.9] times shorter in the vented setup (p < 0.002). This led to comparable zero drug delivery times between the two setups (p = 0.294). Start-up times as defined by the achievement of at least 90% of steady state flow rate were achieved faster with the vented setup (p < 0.0001), but this was counteracted by the increased backflow volumes. The application of the venting principle to the start-up of microinfusions does not improve the timely delivery of drugs to the patient since the faster start-up times are counteracted by higher backflow volumes when opening the three-way stopcock.

Effect of vertical pump position on start-up fluid delivery of syringe pumps used for microinfusion

BACKGROUND

Connection and opening a syringe infusion pump to a central venous line can lead to acute anterograde or retrograde fluid shifts depending on the level of central venous pressure. This may lead to bolus events or to prolonged lag times of intravenous drug delivery, being particularly relevant when administering vasoactive or inotropic drugs in critically ill patients using microinfusion. The aim of this study was to assess the effect of syringe pump positioning at different vertical heights on start-up fluid delivery before versus after purging and connection the pump to the central venous catheter.

METHODS

This in vitro study measured ante- and retrograde infusion volumes delivered to the central venous line after starting the syringe pump at a set infusion rate of 1 mL/h. In setup one, the pump was first positioned to vertical levels of +43 cm or -43 cm and then purged and connected to a central venous catheter. In setup two, the pump was first purged and connected at zero level and secondarily positioned to a vertical level of +43 cm or -43 cm. Central venous pressure was adjusted to 10 mmHg in both setups.

RESULTS

Positioning of the pump prior to purging and connection to the central venous catheter resulted in a better start-up performance with delivered fluid closer to programmed and expected infusion volumes when compared to the pump first purged, connected, and then positioned. Significant backflow volumes were observed with the pump purged and connected first and then positioned below zero level. No backflow was measured with the pump positioned first below zero level and then purged and connected.

CONCLUSIONS

Syringe infusion pump assemblies should be positioned prior to purging and connection to a central venous catheter line when starting a new drug, particularly when administering highly concentrated vasoactive or inotropic drugs delivered at low flow rates.

Effect of central venous pressure on fluid delivery during start-up of syringe infusion pumps for microinfusion

BACKGROUND

Intravenous administration of highly concentrated and potent drugs at low flow rates is common practice, particularly in critically ill children. Drug delivery during infusion start-up can be considerably delayed by intrinsic factors of syringe infusion pump assemblies. The impact of central venous pressures on the course of start-up fluid delivery of such microinfusions remains unknown.

METHODS

Infusion volumes delivered after activation of the start button in a conventional 50 mL syringe infusion pump assembly equilibrated (representing classical in vitro testing) and not equilibrated (representing real clinical conditions) to central venous pressure levels of 0, 10 and 20 mmHg at a set infusion flow rate of 1 mL/h were measured using a fluidic flow sensor.

RESULTS

The experimental setup mimicking real life conditions demonstrated considerable differences in fluid delivery during pump start-up depending on central venous pressure. A central venous pressure of 0 mmHg resulted in massive fluid delivery at infusion start-up, while central venous pressure levels of 10 and 20 mmHg resulted in retrograde flows with related mean (95% CI) zero-drug delivery times of 3.22 (2.98-3.46) min and 4.51 (4.33-4.69) min, respectively (p < .0001).

CONCLUSION

Depending on central venous pressure level, connection and starting a new syringe pump can result in significant antegrade or retrograde fluid volumes. In clinical practice, this can lead to hemodynamic instability and hence requires clinical alertness. Further research and methods to improve start-up performance in syringe infusion pump systems are desirable.

An analysis of the effect of syringe barrel volume on performance and user perception

In the market, there are many types and shapes of syringes. One of the groupings of syringe types is based on barrel volume. The shape of the product design affects performance and user perception. The aim of this study is to investigate the effect of barrel volume on its performance and user perception. We performed analysis following international organization for standardization 7886 procedures on syringe with 1 mL, 3 mL, 5 mL, and 10 mL volume. In addition, a user perception test was conducted on 29 respondents using a questionnaire with the Likert chart method. This study indicates that the bigger the syringe volume, the larger the dead space and the force to operate the piston are. A larger syringe volume also raises the volume that changes due to the plunger position increase. Meanwhile, the barrel volume does not affect water and water leakage, as we did not observe any leak during the syringe tests in our experiment. In addition, the user perception test shows that the barrel's length influences the ease of device control during the injection. The volume of the barrel negatively correlated with its effect to the environment. The safety features of all syringes are similar except for the 3 mL syringe, which has a value of 0.1 points difference to other syringes.

One hundred ECMO retrivals before and during the Covid-19 pandemic: an observational study

OBJECTIVES

Patients with severe acute respiratory distress syndrome may require veno-venous extracorporeal membrane oxygenation (V-V ECMO) support. For patients in peripheral hospitals, retrieval by mobile ECMO teams and transport to high-volume centers is associated with improved outcomes, including the recent COVID-19 pandemic. To enable a safe transport of patients, a specialised ECMO-retrieval program needs to be implemented. However, there is insufficient evidence on how to safely and efficiently perform ECMO retrievals. We report single-centre data from out-of-centre initiations of VV-ECMO before and during the COVID-19 pandemic.

DESIGN & SETTING

Single-centre retrospective study. We include all the retrievals performed by our ECMO centre between January 1st, 2014, and April 30th, 2021.

RESULTS

One hundred ECMO missions were performed in the study period, for a median retrieval volume of 13 (IQR: 9-16) missions per year. the cause of the acute respiratory distress syndrome was COVID-19 in 10 patients (10 %). 98 (98 %) patients were retrieved and transported to our ECMO centre. To allow safe transport, 91 of them were cannulated on-site and transported on V-V ECMO. The remaining seven patients were centralised without ECMO, but they were all connected to V-V ECMO in the first 24 hours. No complications occurred during patient transport. The median duration of the ECMO mission was 7 hours (IQR: 6-9, range: 2 - 17). Median duration of ECMO support was 14 days (IQR: 9-24), whereas the ICU stay was 24 days (IQR:18-44). Overall, 73 patients were alive at hospital discharge (74 %). Survival rate was similar in non-COVID-19 and COVID-19 group (73 % vs 80 %, p = 0.549).

CONCLUSION

In this single-centre experience, before and during COVID-19 era, retrieval and ground transportation of ECMO patients was feasible and was not associated with complications. Key factors of an ECMO retrieval program include a careful selection of the transport ambulance, training of a dedicated ECMO mobile team and preparation of specific checklists and standard operating procedures.

The hypodermic syringe performance based on the ISO 7886-1:2017: A narrative review

A syringe is used to inject fluid or medicine into the patient's soft tissue. The main components of the syringe were the needle, barrel, and plunger. The use of syringes in the medical world is relatively high, and especially since the COVID-19 pandemic, the use of hypodermic syringes increased sharply due to vaccination. The syringe used must be effective and of good quality, so the International Organization for Standardization (ISO) has published test procedures and minimum specifications for hypodermic syringes. The performance of the syringe can be observed from the dead space, force piston operation, water and air leakage, and fitting position of the plunger in the barrel. This review shows that most researchers use the weighing method to measure the dead space, although some use other methods. The researchers found that most of the products met the minimum specifications of the ISO, and that the dimensions and shape of the syringe affected the dead space. Researchers have not examined other performance measures recommended by the ISO. Researchers have focused more on force injection than force piston operation, leakage after injection or back spray than air and water leakage, and reduction the friction of the plunger without considering the fitting position of the plunger in the barrel.