Rapid Blood Transfusion: The Importance of Hemodilution and Needleless Connectors.

INTRODUCTION:  Large-bore cannulas are critical to administering IV fluids and blood products during resuscitation and treatment of hemorrhage. Although catheter flow rates for crystalloid solutions are well defined, rapid administration of blood products is poorly characterized. In this in vitro study, we examined the effects of hemodilution and needleless connectors on red blood cell (RBC) flow rates. METHODS:  To determine RBC flow rates through large-bore cannulae, a crystalloid solution (Normosol®, Hospira, Lake Forest, IL) or RBC units were warmed and delivered under pressure (360 mmHg) using a Level 1 H-1200 Fast Flow Fluid Warmer (Smiths Medical, St. Paul, MN). Flow rates for crystalloid, packed RBCs and diluted RBCs were determined using a stopwatch. Additionally, the effect of the MaxPlus® clear needleless connector (CareFusion, San Diego, CA) was measured in all three infusion groups. RESULTS:  Flow rates for undiluted RBC units were 53% slower than crystalloid solution (220 mL/min vs. 463 mL/min; p=0.0003), however, when RBC units were diluted to a hematocrit of ~30% flow rate improved to 369 mL/min (p=0.005). The addition of the MaxPlus® needleless connector reduced flow of crystalloid solution by 47% (245 mL/min; p=0.0001), undiluted RBCs by 64% (78 mL/min; p=0.01), and diluted RBCs by 51% (180 mL/min; p=0.00003). Compared to undiluted RBC units, hemodilution increased RBC delivery rate through a MaxPlus® connector by 130% (p=0.004) and by 68% (p=0.02) when the catheter was directly connected to the Level 1 tubing (MaxPlus® excluded). CONCLUSION:  In settings requiring rapid transfusion of RBC units, needleless connectors should not be used and hemodilution should be considered in order to decrease the time required to deliver an equivalent red cell mass.

Feasibility study of a smartphone pupillometer and evaluation of its accuracy.

Measurement of pupillary characteristics, such as pupillary unrest in ambient light, and reflex dilation have been shown to be useful in a variety of clinical situations. Dedicated pupillometers typically capture images in the near-infrared to allow imaging in both light and darkness. However, because a subset of pupillary measurements can be acquired with levels of visible light suitable for conventional cameras, it is theoretically possible to capture data using general purpose cameras and computing devices such as those found on smartphones. Here we describe the development of a smartphone-based pupillometer and compare its performance with a commercial pupillometer. Smartphone pupillometry software was developed and then compared with a commercial pupillometer by performing simultaneous scans in both eyes, using the smartphone pupillometer and a commercial pupillometer. The raw scans were compared, as well as a selected pupillary index: pupillary unrest in ambient light. In 77% of the scans the software was able to successfully identify the pupil and iris. The raw data as well as calculated values of pupillary unrest in ambient light were in clinically acceptable levels of agreement; Bland-Altman analysis of raw pupil measurements yielded a 95% confidence interval of 0.26 mm. In certain situations a smartphone pupillometer may be an appropriate alternative to a commercial pupillometer.

100% Nitrous Oxide in the Oxygen Line: How Could This Happen in a Modern Anesthesia Machine?

The inadvertent crossover between O2 and N2O pipelines has become extremely rare in practice. We describe a case where it was possible to ventilate with 100% N2O instead of the intended 100% O2 on a modern anesthesia delivery system (Dräger Apollo; Drägerwerk AG & Co KgaA, Lübeck, Germany). This was the result of the incorrect assembly of diameter index safety system (DISS) components during preventative maintenance that defeated the DISS failsafe system. To make incorrect assembly easier to avoid, DISS component labeling could be more prominent and color-coded, or the internal construction of the gas manifold could incorporate DISS.

An Anesthesia Attempt to Be Green: How Do You Waste Your Carbon Dioxide Absorbers?

Operating room waste is categorized as noncontaminated solid waste (SW) and regulated medical waste (RMW). RMW is treated by autoclaving at an increased economic and environmental cost. We evaluated these costs with a focus on the disposable carbon dioxide (CO2) absorbers. At our institution, exhausted CO2 absorbers were discarded as RMW. We collaborated with product representatives, anesthesia and perioperative staff, and waste management personnel to identify opportunities and barriers for recycling and waste reduction. Ultimately, we agreed to discard CO2 absorbers as SW instead of RMW, a strategy that is practical, less expensive, and more environmentally appropriate.

Cerebral Oximetry Fails as a Monitor of Brain Perfusion in Cardiac Surgery: A Case Report.

Cerebral oximetry is commonly being advocated as a monitor for regional cerebral tissue oxygenation during cardiac surgery. We have increasing concern about the accuracy of this monitor, including the current systems entering the market, with new probes and algorithms. We present 2 cases where cerebral oximetry failed to accurately portray cerebral oxygenation. In the current form, cerebral oximetry may at best be an expensive tool without any benefit on outcomes. In addition, it may contribute to misleading and confusing clinical data.

The use of end-tidal argon to detect venous air embolism: foiled by "fake oxygen!"

Venous air-embolism (VAE) potentially catastrophic complication surgery. Based on previous data using changes in end-tidal nitrogen as an indicator of VAE, we surmised that changes in end-tidal argon (EtAr) may be an indicator of VAE. We sought to determine if a commercial mass-spectrometer (PCT Proline Analyzer 61700-8 Class 85, Ametek, Pittsburgh, PA 15238) could be used to detect changes in EtAr in an invitro model. A Drager Apollo™ (Drager, Lubeck, Germany) anesthesia machine was used to ventilate a dummy lung (2 L bag) with a minute ventilation of 6 L/min in 100% oxygen. The quadrupole mass-spectrometer (sampling at 0.0004 atm-cc/sec) was attached to the end-tidal inlet of the machine. Room air (1-60 mL) was injected into the dummy lung to simulate VAE. A strong baseline ion-current (1.2 × 10-12 amps) of argon was noted. Due to this contamination we were unable to detect "VAE" events of injected air. Argon represents approximately 0.93% of room air, or about 9300 parts per million (ppm). We detected about 2000 ppm argon in medical-grade oxygen (or 0.2%), limiting our ability to detect changes in EtAr. This is a USP-accepted contaminant, rendering this technology is insensitive for early, rapid detection of VAE. We assumed medical grade oxygen was pure and were surprised to learn otherwise. We want to share this likely largely unknown finding with the medical community.

Inaccurate Blood Pressure Readings in the Intensive Care Unit: An Observational Study.

Measuring and monitoring cerebral perfusion pressure (CPP) is important in the management of patients with certain neurological conditions. To accurately reflect blood pressure at the circle of Willis, the arterial line transducer should be leveled at the tragus. This study measured the relative distance of the transducer to the tragus in 100 intensive care unit (ICU) patients in the mixed ICU at our institution, of which 44 patients had a pressure-sensitive neurological diagnosis. For neurological patients, the average distance was 10.9 cm and for non-neurological patients, the average distance was 11.4 cm (p-value: 0.60). This suggests that the arterial line transducer was leveled at approximately the same level regardless of pathology, potentially leading to falsely elevated CPP readings in patients with pressure-sensitive neurological pathology.

A novel thermal compression device for perioperative warming: a randomized trial for feasibility and efficacy.

BACKGROUND: Inadvertent perioperative hypothermia (IPH) leads to surgical complications and increases length of stay. IPH rates are high with the current standard of care, forced air warming (FAW). Our hypothesis is that a prototype thermal compression device that heats the popliteal fossa and soles of the feet, with lower leg compression, increases perioperative temperatures and reduces IPH compared to the current standard of care. METHODS: Thirty six female breast surgery patients, at a tertiary academic hospital, were randomized to the device or intraoperative FAW (stage I) with a further 18 patients randomized to the device with a single heating area only (stage II, popliteal fossa or sole of the feet). Stage I: 37 patients recruited (final 36). Stage II: 18 patients recruited (final 18). INCLUSION CRITERIA: general anesthesia with esophageal monitoring for over 30 min, legs available and able to fit the device and no contraindications to leg heating or compression. The intervention was: Stage I: Investigational prototype thermal compression device (full device group) or intraoperative FAW. Stage II: Device with only a single heating location. Primary outcomes were perioperative temperatures and incidence of IPH. Secondary outcomes were local skin temperature, general and thermal comfort scores and presence of perioperative complications, including blood loss. RESULTS: Mean temperatures in the full device group were significantly higher than the FAW group in the pre-operative (36.7 vs 36.4 °C, p < 0.001), early intraoperative (36.3 vs 35.9 °C, p < 0.001), intraoperative (36.6 vs 36.2 °C, p < 0.001) and postoperative periods (36.8 vs 36.5 °C, p < 0.001). The incidence of IPH in the device group was also significantly lower (16.7% vs 72.0%, p = 0.001). Thermal comfort scores were significantly higher in the full device group and hypothermia associated wound complications were higher in the FAW group. CONCLUSIONS: The thermal compression device is feasible and has efficacy over the FAW. Further studies are recommended to investigate clinically significant outcomes. TRIAL REGISTRATION: clinicaltrials.gov ( NCT02155400 ).

Capnoperitoneum During Peroral Endoscopic Myotomy-Recognition and Management: A Case Report.

Peroral endoscopic myotomy (POEM) is a minimally invasive procedure for treating esophageal achalasia. During POEM, carbon dioxide is insufflated under pressure into the esophagus and stomach, which can cause clinically significant capnoperitoneum, capnomediastinum, or capnothorax. We present a case in which gas accumulation in the abdomen during POEM had adverse effects on ventilation. Once the cause was recognized, needle decompression of the abdomen led to immediate improvement in ventilation.