Abstract
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.
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.
Background
Balloon‐tipped bronchial blocker catheters are widely used in pediatric thoracic anesthesia to establish single‐lung ventilation. In clinical practice, their balloons demonstrate sudden ...expansion when inflated with air. In addition, there are concerns related to the high inflation pressures required to expand the balloons.
Methods
This in vitro study assessed inflation volume‐ and inflation pressure‐balloon diameter characteristics of the Fogarty arterial embolectomy catheters and Arndt endobronchial blockers. Balloon diameters were photographically assessed during unrestricted volume‐ and pressure‐guided inflation, using air up to the maximum allowed inflation volume as indicated by the manufacturers. Inflation pressures required to open the blocker balloons and inflation pressures needed to expand them to maximum indicated diameter were measured.
Results
Volume‐guided inflation demonstrated a late acute rise in diameter in Fogarty blocker balloons, whereas in the Arndt endobronchial blocker balloons almost linear inflation volume‐to‐diameter characteristics were observed. Pressure‐guided inflation on the other hand demonstrated low‐volume, high‐pressure characteristics in the Fogarty blocker balloons, with inflation pressures required to expand the balloons to maximum diameters ranging from (mean (SD)) 636 (75) to 947 (152) cmH2O. The inflation pressures required to open the Fogarty blocker balloons were even >1000 cmH2O. Inflation pressures required to expand the 5 F, 7 F, and 9 F Arndt endobronchial blocker balloons to maximum indicated diameter were much lower, namely at 218 (15), 252 (28), and 163 (8) cmH2O.
Conclusion
Based on these study findings, the balloons of Fogarty arterial embolectomy catheters represent high‐pressure devices and do not permit stepwise controlled bronchial blockage. The Arndt endobronchial blockers have some advantages over the Fogarty blocker devices, but also represent high‐pressure equipment and must be used with caution and limited duration. Manufacturers are asked to design pediatric endobronchial blocker catheters with truly high‐volume, low‐pressure balloons in accordance to age‐related pediatric airway dimensions.
Background
Age‐related recommendations for size selection of bronchial blocker devices are based on a few dated anatomical autopsy and radiological studies determining lower airway dimensions in ...children. These recommendations are based on anterior‐posterior internal bronchial diameters, which are smaller than the more relevant lateral internal bronchial diameters.
Methods
Outer diameters of bronchial blocker balloons inflated with the maximum recommended volume of air were compared to age‐related lateral internal bronchial diameters of left and right proximal mainstem bronchi using five different recommendations for age‐related size selection of bronchial blocker equipment in children published in the literature.
Results
The ratio of outer bronchial blocker diameters inflated with the maximal recommended volume of air to the median lateral internal diameters of the proximal mainstem bronchus ranged from 71.4% to 181.8% for the left side and from 61.7% to 162.6% for the right side. There were many settings where the blocker diameters did not reach the median lateral internal diameters of the proximal mainstem bronchus. This was more often observed for the right than for the left side (37 vs 22 settings).
Conclusion
This analysis demonstrates that irrespective of the recommendation for size selection used, neither the two balloon‐tipped vascular catheters included nor the Arndt endobronchial blockers are ideal for lung isolation in children are compared with the age‐related relevant dimensions of pediatric airway anatomy. A redesign of bronchial blocker equipment with age‐related anatomically based high‐volume, low‐pressure blocker balloons made from ultrathin membranes and with smaller catheters would be desirable.
Background
Flexible bronchoscope-guided tracheal intubation through supraglottic airway devices (SGAs) is a well-established element of difficult intubation algorithms. Success can be limited by ...dimensional incompatibilities between tracheal tubes (TTs) and SGAs.
Methods
In this
in vitro
study, we tested the feasibility of TT passage through SGAs, removal of SGAs over TTs, and the ability to guide the flexible bronchoscope with 13 TT brands (internal diameter, 6.5–8.0 mm) and ten different SGAs (#4 and #5) in an intubation mannequin.
Results
We tested 1,040 combinations of SGAs and TTs. Tracheal tube passage failed in 155 (30%) combinations of the five tested first-generation SGAs (117 46% with SGA #4, 38 15% with SGA #5) and in three (0.6%) combinations of the five tested second-generation SGAs (two 0.8% with SGA #4 and one 0.4% with SGA #5). The reason for failed passage of a TT through a first-generation SGA consistently was a too-narrow SGA connector. Removal of the SGA over the TT in the 882 remaining combinations was impossible for all sizes of reinforced TTs, except the Parker Reinforced TT, and was possible for all non-reinforced TTs. Only one combination with SGA #4 and 84 combinations with SGA #5 were not ideal to adequately guide the flexible bronchoscope.
Conclusion
Clinically relevant combinations of adult-size TTs and SGAs can be incompatible, rendering flexible bronchoscope-guided tracheal intubation through an SGA impossible. Additional limitations exist regarding removal of the SGA and maneuverability of the flexible bronchoscope.
The single-use supraglottic airway devices LMA-Supreme (LMA-S; Laryngeal Mask Company, Henley-on-Thames, United Kingdom) and i-gel (Intersurgical Ltd, Wokingham, Berkshire, United Kingdom) have a ...second tube for gastric tube insertion. Only the LMA-S has an inflatable cuff. They have the same clinical indications and might be useful for difficult airway management. This prospective, crossover, randomized controlled trial was performed in a simulated difficult airway scenario using an extrication collar limiting mouth opening and neck movement.
Sixty patients were included. Both devices were placed in random order in each patient. Primary outcome was overall success rate. Other measurements were time to successful ventilation, airway leak pressure, fiberoptic glottic view, and adverse events.
Success rate for the LMA-S was 95% versus 93% for the i-gel (P = 1.000). LMA-S needed shorter insertion time (34 +/- 12 s vs. 42 +/- 23 s, P = 0.024). Tidal volumes and airway leak pressure were similar (LMA-S 26 +/- 8 cm H20; i-gel 27 +/- 9 cm H20; P = 0.441). Fiberoptic view through the i-gel showed less epiglottic downfolding. Overall agreement in insertion outcome was 54 (successes) and 1 (failure) or 55 (92%) of 60 patients. The difference in success rate was 1.7% (95% CI -11.3% to 7.6%).
Both airway devices had similar insertion success and clinical performance in the simulated difficult airway situation. The authors found less epiglottic downfolding and better fiberoptic view but longer insertion time with the i-gel. Our study shows that both devices are feasible for emergency airway management in patients with reduced neck movement and limited mouth opening.
Rigid scopes are successfully used for management of difficult airways, but learning curves have not been established.
This randomised controlled trial was performed at the University Hospital Bern ...in Switzerland to establish learning curves for the rigid scopes Bonfils and SensaScope and to assess their performance. Fifteen consultant anaesthetists and 15 anaesthesia registrars performed a total of 740 intubations (10 to 20 intubations with each device per physician) in adult patients without predictors of a difficult airway under general anaesthesia. According to randomisation, physicians intubated the patient's trachea with either the Bonfils or the SensaScope. A maximum of three intubation attempts was allowed. Primary outcome was overall time to successful intubation. Secondary outcome parameters included first attempt success, first attempt success within 60 s, failures and adverse events.
A clear learning effect was demonstrated: Over 20 trials, intubations became 2.5-times quicker and first attempt intubation success probability increased by 21-28 percentage points. Fourteen and 20 trials were needed with the Bonfils and the SensaScope, respectively, to reach a 90% first attempt success probability. Intubation times were 23% longer (geometric mean ratio 1.23, 95% confidence interval 1.12-1.36, p < 0.001) and first attempt success was less likely (odds ratio 0.64, 95% confidence interval 0.45-0.92, p = 0.016) with the SensaScope. Consultants showed a tendency for a better first attempt success compared to registrars. Overall, 23 intubations (10 Bonfils, 13 SensaScope) failed. Adverse events were rare and did not differ between devices.
A clear learning effect was demonstrated for both rigid scopes. Fourteen intubations with the Bonfils and 20 intubations with the SensaScope were required to reach a 90% first attempt success probability. Learning of the technique seemed more complex with the SensaScope compared to the Bonfils.
Current Controlled Trials, ISRCTN14429285 . Registered 28 September 2011, retrospectively registered.
Supraglottic airway devices (SGA) are commonly used in pediatric anesthesia and serve as primary or back-up devices for difficult airway management. Most SGA are marketed without proper clinical ...evaluation. The purpose of this study was to evaluate the performance of the pediatric LMA Supreme™, Air-Q® and Ambu® Aura-i™.
This prospective observational study was performed at Bern University Hospital, Switzerland. With ethics committee approval and a waiver for written informed consent 240 children undergoing elective surgery with an ASA class I-III and a weight of 5-30 kg were included. Three different pediatric supraglottic airway devices were assessed: The LMA Supreme™, Air-Q® and Ambu® Aura-i™. Primary outcome parameter was airway leak pressure. Secondary outcome parameters included first attempt and overall success rate, insertion time, fiberoptic view through the SGA, and adverse events. The primary hypothesis was that the mean airway leak pressure of each tested SGA was 20 cmH
O ± 10%.
None of the SGA showed a mean airway leak pressure of 20 cmH
O ± 10%, but mean airway leak pressures differed significantly between devices LMA Supreme™ 18.0 (3.4) cmH
O, Air-Q® 15.9 (3.2) cmH
O, Ambu® Aura-i™ 17.3 (3.7) cmH
O, p < 0.001. First attempt success rates (LMA Supreme™ 100%, Air-Q® 90%, Ambu® Aura-i™ 91%, p = 0.02) and overall success rates (LMA Supreme™ 100%, Air-Q® 91%, Ambu® Aura-i™ 95%, p = 0.02) also differed significantly. Insertion times ranged from 20 (7) seconds (Air-Q®) to 24 (6) seconds (LMA Supreme™, <p = 0.005). Insertion was rated easiest with the LMA Supreme™ (very easy in 97% vs. Air-Q® 70%, Ambu® Aura-i™ 72%, p < 0.001). Fiberoptic view was similar between the SGA. Adverse events were rare.
Airway leak pressures ranged from 16 to 18 cmH
O, enabling positive pressure ventilation with all successful SGA. The highest success rates were achieved by the LMA Supreme™, which was also rated easiest to insert.
ClinicalTrials.gov , identifier NCT01625858 . Registered 31 May 2012.
Apneic oxygenation in pediatric anesthesia Kleine-Brueggeney, Maren; Grosshauser, Mareike; Greif, Robert
Current opinion in anaesthesiology,
2022-Jun-01, 2022-06-00, 20220601, Letnik:
35, Številka:
3
Journal Article
Odprti dostop
Apneic oxygenation is increasingly used in pediatric anesthesia. Its benefit for specific applications depends on the effect of apneic oxygenation on safe apnea time and carbon dioxide (CO2) ...elimination, on differences between low and high flow oxygen delivery, and on possible adverse effects. The present review summarizes current evidence on these pathophysiological aspects of apneic oxygenation as well as its applications in pediatric anesthesia.
Apneic oxygenation with both low flow and high flow nasal oxygen increases the safe apnea time, but does not lead to increased CO2 elimination. Airway pressures and adverse effects like atelectasis formation, oxidative stress and aerosol generation under apneic oxygenation are not well studied in pediatric anesthesia. Data from adults suggest no important effect on airway pressures when the mouth is open, and no significant formation of atelectasis, oxidative stress or aerosol generation with high flow nasal oxygen.
Apneic oxygenation in pediatric anesthesia is mainly used during standard and difficult airway management. It is sometimes used for airway interventions, but CO2 accumulation remains a major limiting factor in this setting. Reports highlight the use of high flow nasal oxygen in spontaneously breathing rather than in apneic children for airway interventions.
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