Aluminium release and fluid warming: provocational setting and devices at risk

Verification of an intravenous fluid warmer: A prospective, two-center observational trial

Objectives

Avoiding inadvertent hypothermia during surgery is important. Intravenous fluid warmers used intraoperatively are critical for maintaining euthermia. We sought to prospectively evaluate the performance of the parylene-coated enFlow™ intravenous fluid warmer in patients undergoing surgery.

Methods

This was a prospective two-center observational clinical trial performed in inpatient surgical services of two large academic hospital systems. After written informed consent, patients were enrolled in the trial. All patients were adults scheduled for a surgery that was expected to last for at least 1 h with the administration of at least 1 L of fluid warmed prior to infusion. Patient temperature was recorded in the preoperative unit, at the induction of anesthesia, and then every 15 or 30 min until the end of surgery. Temperature monitoring continued in the recovery unit. The parylene-coated enFlow™ intravenous fluid warmer was used in addition to the usual patient warming techniques. The primary outcome was the average core temperature, and secondary analyses assessed individual temperature measurements, temperature measurements during specific time periods, and rate of hypothermic events.

Results

In all, 50 patients (29 males) with a mean age of 64 years were included in the analysis. The mean surgical time was 195 min and patients received an average of 1142 mL of fluids. Core temperature dropped by only 0.3°C approximately 60 min after induction and recovered back to the baseline level approximately 60 min later. There was no correlation between flow rate and measured core body temperature.

Conclusions

The parylene-coated enFlow intravenous fluid warmer was able to warm fluids at all flow rates during prolonged surgery. The results showed that enFlow performed as expected.

The results of designing a new prototype device and algorithm in closed method intraperitoneal hyperthermia model in rats

BACKGROUND

There is currently no standard medical device and method available for hyperthermic intraperitoneal therapy studies in rats. In this study, we present our designed device and algorithm that operates based on our own protocol for hyperthermic intraperitoneal treatment in rats. The aim was to demonstrate the effectiveness of the designed device, algorithm, and hyperthermia protocol by showing that the device can achieve the desired temperature inside the rat's abdomen, does not cause rat loss due to complications, operates autonomously, and provides warnings to the operator in case of emergencies.

METHODS

A closed method for intraperitoneal hyperthermia protocol was established for 6 female 8-week-old (280-310 g) albino Wistar rats. Fluid inlet and outlet tubes and a temperature probe were inserted through a 1 cm vertical incision between the xiphoid and bladder in the rat's abdomen, and the skin was sutured in a circular manner. A protocol for intraperitoneal hyperthermic treat-ment was established using a saline solution at a flow rate of 100 mL/min for 60 min, maintaining a temperature of 41°C±0.5 inside the rat's abdomen.

RESULTS

During the study, a temperature of 41°C±0.5 was successfully achieved in the abdomen of all rats at a flow rate of 100 mL/min±5 for 60 min. Due to three rats reaching a rectal temperature above 38.5°C during the hyperthermia protocol, external cooling was applied to the rat's tail base using ice. There were no losses until the postoperative 72nd h, and the study was successfully completed.

CONCLUSION

Our designed device and algorithm, which prioritize animal welfare, operate rapidly, safely, and with high accuracy sensitivity, have been successful in hyperthermic intraperitoneal treatment studies in rats. We believe that they can be used as a stan-dard method and approach in hyperthermic intraperitoneal studies in rats.

Levels of leachable elements from long-term use of enFlow fluid warmer

Objective:

In the delivery of intravenous fluids, in-line warming devices frequently transfer heat using a metal heating plate, which if uncoated can risk elution. This bench study examined extractable elements detected following long-term use of the parylene-coated enFlow^® Disposable IV/Blood Warmer.

Methods:

We tested 16 clinically relevant challenge fluids typical of the surgical setting, including commercially available single donor blood and blood products as well as intravenous saline and electrolyte solutions. After 72 h of warming at 40°C (104°F) via the enFlow, analytical chemistry identified and quantified the most clinically significant extractable elements (arsenic, barium, cadmium, copper, and lead) to estimate chemical exposure. We also measured the extracted concentrations of these five elements following simulated use of the device with three solutions (Sterofundin ISO, Plasma-Lyte 148, and whole blood) that were pumped through the warmed device at two different flow rates (0.2 and 5.5 mL min⁻¹).

Results:

Across all scenarios of acute and long-term exposures for different populations, the enFlow demonstrated low toxicological risks as measured by the calculation of tolerable exposure for extracted arsenic, barium, cadmium, copper, and lead.

Conclusion:

The results suggest biological safety for the use of parylene-coated enFlow with a variety of intravenous solutions and in different therapeutic scenarios.

Aluminum Leaching from Fluid Warmers: Regulatory Deferral to Clinicians' Decision

Fluid-warming systems are crucial in surgical and trauma settings because of their key role in preventing or treating hypothermia and enabling proper resuscitation of blood products that are stored cold. Recently, several manufacturers have issued warnings of the possibility of aluminum leaching from their fluid warmers and cautioned about the potential for aluminum toxicity in patients who underwent fluid resuscitation with these devices. Studies suggest that one of the main factors affecting aluminum leaching in this setting is the coating of the aluminum plate itself. Coating, often with a biocompatible material, appears to reduce aluminum leaching by 100- to 200-fold compared with an uncoated plate. Nonetheless, leaching with the coating is still at a level exceeding U.S. regulations. A few aluminum-free warming systems are available on the market, but these are not carried by all providers and some clinicians may be less familiar with their use. Medical device manufacturers will likely design future warming systems with less potential for aluminum blood contact. In the meantime, the risk of inadequate resuscitation, consequent to the proper fluid warmer no longer being available, is contrasted with the risk of potential toxicity. In the situation described here, the regulators deferred the ultimate decision of which fluid warmer to use in a given situation to the risk-benefit decision of the clinician.

Impact of parylene coating on heating performance of intravenous fluid warmer: a bench study

BACKGROUND

Perioperative hypothermia is a common occurrence, particularly with the elderly and pediatric age groups. Hypothermia is associated with an increased risk of perioperative complications. One method of preventing hypothermia is warming the infused fluids given during surgery. The enFlow™ intravenous fluid warmer has recently been reintroduced with a parylene coating on its heating blocks. In this paper, we evaluated the impact of the parylene coating on the new enFlow's fluid warming capacity.

METHODS

Six coated and six uncoated enFlow cartridges were used. A solution of 10% propylene glycol and 90% distilled H2O was infused into each heating cartridge at flow rates of 2, 10, 50, 150, and 200 ml/min. The infused fluid temperature was set at 4 °C, 20 °C, and 37 °C. Output temperature was recorded at each level. Data for analysis was derived from 18 runs at each flow rate (six cartridges at three temperatures).

RESULTS

The parylene coated fluid warming cartridge delivered very stable output of 40 °C temperatures at flow rates of 2, 10, and 50 ml/min regardless of the temperature of the infusate. At higher flow rates, the cartridges were not able to achieve the target temperature with the colder fluid. Both cartridges performed with similar efficacy across all flow rates at all temperatures.

CONCLUSIONS

At low flow rates, the parylene coated enFlow cartridges was comparable to the original uncoated cartridges. At higher flow rates, the coated and uncoated cartridges were not able to achieve the target temperature. The parylene coating on the aluminum heating blocks of the new enFlow intravenous fluid warmer does not negatively affect its performance compared to the uncoated model.