Low Pneumoperitoneum Pressure Reduces Gas Embolism During Laparoscopic Liver Resection: A Randomized Controlled Trial

OBJECTIVE

To compare the effect of low and standard pneumoperitoneal pressure (PP) on the occurrence of gas embolism during laparoscopic liver resection (LLR).

BACKGROUND

LLR has an increased risk of gas embolism. Although animal studies have shown that low PP reduces the occurrence of gas embolism, clinical evidence is lacking.

METHODS

This parallel, dual-arm, double-blind, randomized controlled trial included 141 patients undergoing elective LLR. Patients were randomized into standard ("S," 15 mm Hg; n = 70) or low ("L," 10 mm Hg; n = 71) PP groups. Severe gas embolism (≥ grade 3, based on the Schmandra microbubble method) was detected using transesophageal echocardiography and recorded as the primary outcome. Intraoperative vital signs and postoperative recovery profiles were also evaluated.

RESULTS

Fewer severe gas embolism cases (n = 29, 40.8% vs n = 47, 67.1%, P = 0.003), fewer abrupt decreases in end-tidal carbon dioxide partial pressure, shorter severe gas embolism duration, less peripheral oxygen saturation reduction, and fewer increases in heart rate and lactate during gas embolization episodes was found in group L than in group S. Moreover, a higher arterial partial pressure of oxygen and peripheral oxygen saturation were observed, and fewer fluids and vasoactive drugs were administered in group L than in group S. In both groups, the distensibility index of the inferior vena cava negatively correlated with central venous pressure throughout LLR, and a comparable quality of recovery was observed.

CONCLUSIONS

Low PP reduced the incidence and duration of severe gas embolism and achieved steadier hemodynamics and vital signs during LLR. Therefore, a low PP strategy can be considered a valuable choice for the future LLR.

Effects of different fractions of inspired oxygen on gas embolization during hysteroscopic surgery: A double-blind, randomized, controlled trial

OBJECTIVE

Gas embolism is a common complication of hysteroscopic surgery that causes serious concern among gynecologists and anesthesiologists due to the potential risk to patients. The factors influencing gas embolism in hysteroscopic surgery have been extensively studied. However, the effect of the oxygen concentration inhaled by patients on gas embolism during hysteroscopic surgery remains elusive. Therefore, we designed a double-blind, randomized, controlled trial to determine whether different inhaled oxygen concentrations influence the occurrence of gas embolism during hysteroscopic surgery.

METHODS

This trial enrolled 162 adult patients undergoing elective hysteroscopic surgery who were randomly divided into three groups with inspired oxygen fractions of 30%, 50%, and 100%. Transthoracic echocardiography (four-chamber view) was used to evaluate whether gas embolism occurred. Before the start of surgery, the four-chamber view was continuously monitored.

RESULTS

The number of gas embolisms in the 30%, 50%, and 100% groups was 36 (69.2%), 30 (55.6%), and 24 (44.4%), respectively. The incidence of gas embolism gradually decreased with increasing inhaled oxygen concentration (P = 0.031).

CONCLUSION

In hysteroscopic surgery, a higher oxygen concentration inhaled by patients may reduce the incidence of gas embolism, indicating that a higher inhaled oxygen concentration, especially 100%, could be recommended for patients during hysteroscopic surgery.

TRIAL REGISTRATION

Chinese Clinical Trial Registry (https://www.chictr.org.cn/showproj.html?proj=53779, Registration number: ChiCTR2000033202).

Semisitting position for cerebello-pontine angle surgery: Analysis of complications and how to avoid it

OBJECTIVE

To analyze the primary complications related to semisitting position in patients undergoing cerebelo-pontine angle surgery.

METHODS

Retrospective data analysis from patients undergoing elective tumoral cerebelo-pontine angle surgery in a semisitting position. The incidence, severity, occurrence moment, treatment, duration, and outcomes of venous air embolism (VAE), pneumocephalus, postural hypotension, and other complications were recorded. Neurointensive care unit (NICU), length of stay (LOS), hospital LOS, and modified Rankin scale scores were calculated six months after surgery.

RESULTS

Fifty patients were operated on. Eleven (22%) presented VAE (mean duration 8±4.5min): five (10%) during tumor resection, and four (8%) during dural opening. Ten (20%) were resolved by covering the surgical bed, air bubbles aspiration, jugular compression, and one (2%) tilted to a steep Trendelenburg position. One (2%) had intraoperative hemodynamic instability. The only variable associated with VAE was meningioma at histopathology OR=4.58, p=0.001. NICU was higher in patients with VAE (5.5±1.06 vs. 1.9±0.20 days, p=0.01). There were no differences in the Rankin scale. All patients presented postoperative pneumocephalus with a good level of consciousness, except one (2%) who required evacuation. Seven patients (14%) showed postural hypotension, three (6%) after positioning, and one (2%) after developing a VAE; all were reversed with usual vasoactive drugs. No other position-related complications or mortality were registered in this series.

CONCLUSIONS

The semisitting position is a safe option with the knowledge, prevention, detection, and early solution of all the possible complications. The development of VAE rarely implies hemodynamic instability or greater disability after surgery. Postoperative pneumocephalus is very common and rarely requires evacuation. Excellent cooperation between anesthesia, nursing, neurophysiology, and neurosurgery teams is essential to manage complications.

Evaluation of the Catheter Clamp over Hydrophilic Guide Wire Central Venous Catheter Exchange Technique for Air Embolism Prophylaxis in an In Vitro Model

PURPOSE

To develop a reproducible in vitro model simulating central venous catheter (CVC) exchange with high potential for air embolization and test the hypothesis that a closed catheter clamp over hydrophilic guide wire exchange technique will significantly reduce the volume of air introduced during CVC exchange.

MATERIALS AND METHODS

The model consisted of a 16-F valved sheath, 240-mL container, and pressure transducer submerged in water in a 1,200-mL suction canister system. Continuous wall suction was applied to the canister to maintain negative pressure at -7 mm Hg or -11 mm Hg. Each trial consisted of 0.035-inch hydrophilic guide wire introduction, over-the-wire catheter exchange, and wire removal following clinical protocol. A total of 256 trials were performed, 128 trials at each pressure with the catheter clamp open (n = 64) or closed (n = 64) around the hydrophilic guide wire.

RESULTS

There was a statistically significant lower volume of air introduced with closed clamp over-the-wire exchanges than with open clamp exchanges at both pressures (2-tailed t-test, P < .001). At -7 mm Hg, a mean of 48.0 mL (SD ± 9.3) of air was introduced with open clamp and 20.6 mL (SD ± 4.7) of air was introduced with closed clamp. At -11 mm Hg, 97.8 mL (SD ± 11.9) of air was introduced with open clamp and 37.8 mL (SD ± 6.3) of air was introduced with closed clamp.

CONCLUSIONS

This study demonstrated the use of a reproducible in vitro model mimicking conditions causing air embolism during CVC exchange. Results showed that CVC exchange using closed catheter clamp over hydrophilic guide wire exchange technique significantly reduced the volume of air introduced per exchange.

Dynamic Lateral Semisitting Position for Supracerebellar Approaches: Technical Note and Case Series

BACKGROUND

It has always been a matter of debate which position is ideal for the supracerebellar approach. The risk of venous air embolism (VAE) is the major deterrent for surgeons and anesthesiologists, despite the fact that sitting and semisitting positions are commonly used in these operations.

OBJECTIVE

To demonstrate a reduction on the risk of VAE and tension pneumocephalus throughout the operation period while taking advantages of the semisitting position.

METHODS

In this study, 11 patients with various diagnoses were operated in our department using the supracerebellar approach in the dynamic lateral semisitting position. We used end-tidal carbon dioxide and arterial blood pressure monitoring to detect venous air embolism.

RESULTS

None of the patients had clinically significant VAE in this study. No tension pneumocephalus or major complications were observed. All the patients were extubated safely after surgery.

CONCLUSION

The ideal position, with which to apply the supracerebellar approach, is still a challenge. In our study, we presented an alternative position that has advantages of the sitting and semisitting positions with a lower risk of venous air embolism.

Mini Trampoline, a New and Promising Way of SCUBA Diving Preconditioning to Reduce Vascular Gas Emboli?

Background: Despite evolution in decompression algorithms, decompression illness is still an issue nowadays. Reducing vascular gas emboli (VGE) production or preserving endothelial function by other means such as diving preconditioning is of great interest. Several methods have been tried, either mechanical, cardiovascular, desaturation aimed or biochemical, with encouraging results. In this study, we tested mini trampoline (MT) as a preconditioning strategy. Methods: In total, eight (five females, three males; mean age 36 ± 16 years; body mass index 27.5 ± 7.1 kg/m2) healthy, non-smoking, divers participated. Each diver performed two standardized air dives 1 week apart with and without preconditioning, which consisted of ±2 min of MT jumping. All dives were carried out in a pool (NEMO 33, Brussels, Belgium) at a depth of 25 m for 25 min. VGE counting 30 and 60 min post-dive was recorded by echocardiography together with an assessment of endothelial function by flow-mediated dilation (FMD). Results: VGE were significantly reduced after MT (control: 3.1 ± 4.9 VGE per heartbeat vs. MT: 0.6 ± 1.1 VGE per heartbeat, p = 0.031). Post-dive FMD exhibited a significant decrease in the absence of preconditioning (92.9% ± 7.4 of pre-dive values, p = 0.03), as already described. MT preconditioning prevented this FMD decrease (103.3% ± 7.1 of pre-dive values, p = 0.30). FMD difference is significant (p = 0.03). Conclusions: In our experience, MT seems to be a very good preconditioning method to reduce VGE and endothelial changes. It may become the easiest, cheapest and more efficient preconditioning for SCUBA diving.

High-altitude decompression strain can be reduced by an early excursion to moderate altitude while breathing oxygen

Recent observations suggest that development of venous gas emboli (VGE) during high-altitude flying whilst breathing hyperoxic gas will be reduced by intermittent excursions to moderate altitude. The present study aimed to investigate if an early, single excursion from high to moderate altitude can be used as an in-flight means to reduce high-altitude decompression strain. Ten healthy men were investigated whilst breathing oxygen in a hypobaric chamber under two conditions, once during a 90-min continuous exposure to a simulated cabin altitude of 24,000 ft (High; H) and once during 10 min at 24,000 ft, followed by 30 min at 15,000 ft and by 80 min at 24,000 ft (high–low–high; H–L–H). VGE scores were assessed by cardiac ultrasound, using a 6-graded scale. In H, VGE increased throughout the course of the sojourn at 24,000 ft to attain peak value [median (range)] of 3 (2–4) at min 90, just prior to descent. In H–L–H, median VGE scores were 0 throughout the trial, except for at min 10, just prior to the excursion to 15,000 ft, whence the VGE score was 1.5 (0–3). Thus, an early, single excursion from high to moderate cabin altitude holds promise as an in-flight means to reduce the risk of altitude decompression sickness during long-duration high-altitude flying in aircraft with limited cabin pressurization. Presumably, such excursion acts by facilitating the gas exchange in decompression bubbles from a predomination of nitrogen to that of oxygen.

Acclimatization to diving: a systematic review

Multiday hyperbaric exposure has been shown to reduce the incidence of decompression sickness (DCS) of compressed-air workers. This effect, termed acclimatization, has been addressed in a number of studies, but no comprehensive review has been published. This systematic review reports the findings of a literature search. PubMed, Ovid Embase, The Cochrane Library and Rubicon Research Repository were searched for studies reporting DCS incidence, venous gas embolism (VGE) or subjective health reports after multiday hyperbaric exposure in man and experimental animals. Twenty-nine studies fulfilled inclusion criteria. Three epidemiological studies reported statistically significant acclimatization to DCS in compressed-air workers after multiday hyperbaric exposure. One experimental study observed less itching after standardized simulated dives. Two human experimental studies reported lower DCS incidence after multiday immersed diving. Acclimatization to DCS has been observed in six animal species. Multiday diving had less consistent effect on VGE after hyperbaric exposure in man. Four studies observed acclimatization while no statistically significant acclimatization was reported in the remaining eight studies. A questionnaire study did not report any change in self-perceived health after multiday diving. This systematic review has not identified any study suggesting a sensitizing effect of multiday diving, and there is a lack of data supporting benefit of a day off diving after a certain number of consecutive diving days. The results suggest that multiday hyperbaric exposure probably will have an acclimatizing effect and protects from DCS. The mechanisms causing acclimatization, extent of protection and optimal procedure for acclimatization has been insufficiently investigated.

Acclimatization to diving: a systematic review

Multiday hyperbaric exposure has been shown to reduce the incidence of decompression sickness (DCS) of compressed-air workers. This effect, termed acclimatization, has been addressed in a number of studies, but no comprehensive review has been published. This systematic review reports the findings of a literature search. PubMed, Ovid Embase, The Cochrane Library and Rubicon Research Repository were searched for studies reporting DCS incidence, venous gas embolism (VGE) or subjective health reports after multiday hyperbaric exposure in man and experimental animals. Twenty-nine studies fulfilled inclusion criteria. Three epidemiological studies reported statistically significant acclimatization to DCS in compressed-air workers after multiday hyperbaric exposure. One experimental study observed less itching after standardized simulated dives. Two human experimental studies reported lower DCS incidence after multiday immersed diving. Acclimatization to DCS has been observed in six animal species. Multiday diving had less consistent effect on VGE after hyperbaric exposure in man. Four studies observed acclimatization while no statistically significant acclimatization was reported in the remaining eight studies. A questionnaire study did not report any change in self-perceived health after multiday diving. This systematic review has not identified any study suggesting a sensitizing effect of multiday diving, and there is a lack of data supporting benefit of a day off diving after a certain number of consecutive diving days. The results suggest that multiday hyperbaric exposure probably will have an acclimatizing effect and protects from DCS. The mechanisms causing acclimatization, extent of protection and optimal procedure for acclimatization has been insufficiently investigated.

Proactive Air Management in CT Power Injections: A Comprehensive Approach to Reducing Air Embolization

OBJECTIVE

Venous air embolism as a complication of contrast media administration from power injection systems in CT is found to occur in 7%-55% of patients, impacting patient safety, diagnostic image quality, workflow efficiency, and patient and radiographer satisfaction. This study reviews the challenges associated with reactive air management approaches employed on contemporary systems, proposes a novel air management approach using proactive methods, and compares the impact of reactive and proactive approaches on injected air volumes under simulated clinical use.

METHODS

Injected air volumes from three power injection systems were measured under simulated clinical use via custom air trap fixture. Two of the systems employed reactive air management approaches, while a new system implemented the proposed proactive air management approach.

RESULTS

The proactive system injected significantly less air (average of 0.005 mL ± 0.006 mL with a maximum of 0.017 mL) when compared to two systems with reactive approaches (averages of 0.130 mL ± 0.082 mL and 0.106 mL ± 0.094 mL with maximums of 0.259 mL and 0.311 mL, respectively) (p < 0.05). CT images were taken of static and dynamic 0.1 mL air bubbles inside of a vascular phantom, both of which were clearly visible. Additionally, the dynamic bubble was shown to introduce image artifacts similar to those observed clinically.

CONCLUSION

Comparison of the injected air volumes show that a system with a proactive air management approach injected significantly less air compared to tested systems employing reactive approaches.

SIGNIFICANCE

The results indicate that the use of a proactive approach could significantly reduce the prevalence of observable, and potentially artifact-inducing, venous air embolism in contrast-enhanced CT procedures.

Comparison of 2 CT Contrast Media Injection Systems: Visual Air Identification and Injector Face Cleaning

PURPOSE

To compare the MEDRAD Stellant and MEDRAD Stellant FLEX computed tomography contrast media injection systems in terms of radiologic technologists' ability to visually identify air in the syringes at various distances and under different lighting conditions, as well as the ease of cleaning contrast media spills on the injector faces.

METHODS

Ten experienced radiologic technologists performed 104 tests (52 per injector) in normal light and in ambient light conditions. The tests were randomized for the radiologic technologists' distance from the injector at 2 ft (61 cm), 8 ft (244 cm), and 16 ft (488 cm). In addition, the authors tested the cleaning efficiency of the Stellant injector face with raised buttons and the Stellant FLEX injector face with buttons on a flush surface by applying a mixture of contrast media and invisible ultraviolet ink. Radiologic technologists followed 2 cleaning protocols: a quick clean (5 seconds) and a full clean (1 minute). Residual contrast mixture was measured.

RESULTS

The Stellant FLEX injector had an overall higher rate of correct air identification than did the Stellant injector, 97.5% vs 86.9%, respectively (P < .001), with improvement seen at greater distances. The rates for the Stellant FLEX injector remained stable for all distances (99.4%-93.9%; P < .003). A similar result was seen with ambient lighting: The visibility of air in the Stellant FLEX injector remained stable (P < .001). During cleaning, the Stellant FLEX injector required less time to reach a greater level of cleanliness and showed less contrast mixture residue, especially after the quick clean procedure (16% and 59%, respectively; P < .001).

DISCUSSION

Injector manufacturers provide various technologies to assist radiologic technologists in visualizing the presence of air in a syringe. The Stellant injector features clear syringes with FluiDots as an air identification technology. The Stellant FLEX injector incorporates an added feature called Beacon technology. This study's results are highly clinically relevant because unintentional iatrogenic air injection occurs in clinical practice and can, in rare cases, severely harm patients.

CONCLUSION

Radiologic technologists showed an improved ability to identify air in the syringes in the Stellant FLEX system. In addition, radiologic technologists were confident about their identification, specifically at greater distances and in ambient lighting conditions. The Stellant FLEX injector face also enabled quicker and more efficient cleaning.

Evolution and Preservation of Venous Gas Emboli at Alternating High and Moderate Altitude Exposures

INTRODUCTION: The evolution and preservation of venous gas emboli (VGE), as markers of decompression stress, were investigated during alternating high- and moderate altitude exposures, thus, simulating a fighter aircraft high-altitude flight, interrupted by refueling excursions to lower altitudes.METHODS: Eight men served as subjects during three normoxic simulated altitude exposures: High = 90 min at 24,000 ft; High-Low = three × 30 min at 24,000 ft, interspersed by two 30-min intervals at 15,000 ft; Low = 90 min at 15,000 ft. VGE scores were assessed by cardiac ultrasound, using a 5-grade scale. Respiratory nitrogen exchange was measured continuously using a modified closed-circuit electronic rebreather.RESULTS: Both High and High-Low induced persistent VGE, with no inter-condition difference either at rest [median (range): High: 1 (0-3), High-Low: 2 (0-3)] or during unloaded knee-bends [High: 3 (1-4), High-Low: 3 (0-4)], whereas VGE was considerably less in Low, both at rest [0 (0-1)] and during knee-bends [0 (0-2)]. In High-Low, VGE decreased temporarily during the 15,000-ft excursions, but resumed pre-excursion values upon return to 24,000 ft. During the final descent to ground level, VGE were more persistent following High-Low than High. In both High and Low, nitrogen was continuously washed out at altitude, whereas in High-Low, the washout at 24,000 ft was interrupted by nitrogen uptake at 15,000 ft.DISCUSSION: In normoxic conditions, long-duration flying at a cabin altitude of 24,000 ft is associated with substantial VGE occurrence, which is not abolished by intermittent excursions to a cabin altitude of 15,000 ft.Ånell R, Grönkvist M, Gennser M, Eiken O. Evolution and preservation of venous gas emboli at alternating high and moderate altitude exposures. Aerosp Med Hum Perform. 2020; 91(1):11-17.

Fibonacci's Golden Ratio-An Innovative Approach to the Design and Management of Extra-Corporeal Circulation

Technological advances in the field of extracorporeal circulation (ECC) over the past decade have led to numerous methods for monitoring metabolism and coagulation during cardiopulmonary bypass (CPB), as well as materials with improved biocompatibility, which has reduced the risk associated with cardiopulmonary bypass. However, ECC is still predominantly based on a traditional design that involves the use of roller pumps. This exposes the patient to a variety of pathophysiological consequences, both intra- and postoperative, such as postoperative cognitive disorders, hemolysis and hemodilution, systemic inflammation and changes in coagulation. This article describes the advantages of an ECC circuit inspired by the Fibonacci Golden Ratio, which does not use a roller pump, in a prospective study on patients undergoing elective cardiac surgery, compared to conventional ECC. During CPB, echocardiography was used to estimate the quality of fluid dynamics in the extracorporeal circuit and the patient's arterial vessels, a DO2 management system was used to evaluate metabolism, and an electronic system was used to determine gaseous microemboli (GME) counts. Fibonacci ECC offered superior intraoperative fluid dynamics, reduced the production of and improved the elimination of GME, and improved intraoperative metabolism, particularly with regard to oxygen delivery and extraction. The improvements in fluid dynamics and metabolic variables were associated with a reduction in the incidence of pathophysiological events compared to the conventional system, particularly regarding transitory cognitive disorders, and a shorter stay in intensive care.

Venous carbon dioxide embolism during laparoscopic cholecystectomy a literature review

Laparoscopy has become the procedure of choice for routine gallbladder removal. A serious complication of this technique is the occurrence of gas emboli due to insufflation. It is associated with a high mortality rate of around 28%. The present systematic review intends to provide more insight into causes, symptoms and risk factors for this specific complication and to explore which measures should be taken to treat and prevent it. The Cochrane library and Pubmed were used as sources. Articles and their references were selected when they were related to the subject in sufficient detail. The course of this complication can vary from asymptomatic up to impairment of normal flow through the right ventricle (RV) or pulmonary artery, potentially leading to acute heart failure. The severity depends on the amount of gas, the rate of accumulation and the ability to remove the gas bubbles. It is difficult to estimate the true incidence of venous gas embolism during laparoscopic cholecystectomy as there are various diagnostic tools, each with different sensitivity. Precautions that need to be taken are: correct positioning of the needle, low insufflation pressure, low insufflation speed, screening for hypovolemia, Trendelenburg positioning, availability of intervention equipment at operation table, no placement of venous catheters during inspiration and catheter removing during expiration. Physicians need to be more aware of this harmful complication and the preventative measurements that need to be taken. As there are virtually no prospective data, future studies are needed to gain more knowledge on gas emboli during laparoscopic cholecystectomy.

Retrospective Analysis of Air Handling by Contemporary Oxygenators in the Setting of Cardiac Surgery

Purpose: Cardiac surgery with the use of extracorporeal circulation is associated with a significant risk for gaseous microemboli (GME) despite excellent surgical techniques and highest operative standards. GME are associated with postoperative neurocognitive dysfunction and negative clinical outcome. This study determines whether oxygenator design has influence on perioperative outcome after cardiac surgery.

Methods: Three different oxygenator models with integrated arterial filter (HiliteAF 7000, Fusion Affinity, and Synthesis) were retrospectively evaluated in 55 patients undergoing elective cardiac surgery with the use of extracorporeal circulation. The two-channel ultrasound bubble counter BCC200 was used to detect GME in real time.

Results: All three oxygenators differ in terms of structural specifications and have different rates of number and volume GME reduction. The Fusion Affinity had the lowest arterial GME volume (1.81 µL ± 0.23 µL), which was statistically significant compared to the Synthesis (3.37 µL ± 0.71 µL, p = 0.014). However, the Synthesis had lower absolute numbers at the venous GME count (31771 µL ± 6579 µL) versus the Fusion Affinity (49304 µL ± 8196 µL). However, with regard to clinical outcome after cardiac surgery (duration of invasive and non-invasive mechanical ventilation, incidence of delirium, stroke, acute renal failure, or new myocardial infarction), we found no differences between groups.

Conclusion: Despite significant differences in the design specifications, all oxygenators eliminated relevant GME volumes safely.

An In-Vitro Study Comparing the GME Handling of Two Contemporary Oxygenators

Gaseous microemboli (GME) are a potential complication of cardiopulmonary bypass (CPB). Though it is difficult to prove that GME is the only major cause of neurological deficits, it may increase the chance of post-operative cognitive dysfunction if not removed. The objectives of this research were to compare LivaNova-Sorin Inspire (Inspire) oxygenator with a Medtronic arterial filter to the Medtronic Fusion (Fusion) oxygenator with and without a Medtronic arterial filter based on each system's ability to handle GME. The Inspire and Fusion systems were evaluated in vitro. GME handling was observed by introducing air in the sampling manifold connected to the venous return at a 60 mL bolus or 1 liter per minute (LPM). The emboli detection and classification (EDAC) system measured GME preand post-oxygenator/arterial filter. The Inspire with a filter was able to remove a statistically significant greater amount of total emboli per second during the 60 mL bolus and 1 LPM tests than the Fusion with and without an arterial filter. The Inspire with an arterial filter was more efficient in removing GME during a 60 mL bolus and 1 LPM than the Fusion and Fusion with an arterial filter. However, the Fusion with an arterial filtered performed better than the Fusion system without the arterial filter.

Health care worker decompression sickness: incidence, risk and mitigation

Inadvertent exposure to radiation, chemical agents and biological factors are well recognized hazards associated with the health care delivery system. Less well appreciated yet no less harmful is risk of decompression sickness in those who accompany patients as inside attendants (IAs) during provision of hyperbaric oxygen therapy. Unlike the above hazards where avoidance is practiced, IA exposure to decompression sickness risk is unavoidable. While overall incidence is low, when calculated as number of cases over number of exposures or potential for a case during any given exposure, employee cumulative risk, defined here as number of cases over number of IAs, or risk that an IA may suffer a case, is not. Commonly, this unique occupational environmental injury responds favorably to therapeutic recompression and a period of recuperation. There are, however, permanent and career-ending consequences, and at least two nurses have succumbed to their decompression insults. The intent of this paper is to heighten awareness of hyperbaric attendant decompression sickness. It will serve as a review of reported cases and reconcile incidence against largely ignored individual worker risk. Mitigation strategies are summarized and an approach to more precisely identify risk factors that might prompt development of consensus screening standards is proposed.

Infusion Pump in UH60L/M Flight in Afghanistan: Why Failures Occur

The ALARIS MSIII Infusion Pump (CareFusion, San Diego, CA) uses 3 separate alarms designed to prevent air emboli: "check air sensor," "air in lower tubing," and "air in line." It is assumed that ambient pressure changes cause air emboli that lead to pump failure although evidence to support this is limited. In this small study, the MSIII proved to be highly resilient and able to maintain function even after large repetitive emboli. Although unproven, it is more likely that these alarms are usually caused by loosening of the intravenous tubing within the pump's collar. This disjointing of the tubing and the ultrasonic sensor can be perceived as an air embolus leading to severe consequences. If the user attempts the clear air function, the pump will not resume function. Problems such as this may have been related to at least 1 reported patient death. More research is needed to determine the cause of these alarms and determine the exact cause. Patient safety can potentially be improved at all levels including manufacturer modifications and operator training. It seems reasonable that the manufacturer should design a mode ("transport mode") that allows the pump to function even with air emboli.

Diagnosis, Treatment, and Prevention of Hemodialysis Emergencies

Given the high comorbidity in patients on hemodialysis and the complexity of the dialysis treatment, it is remarkable how rarely a life-threatening complication occurs during dialysis. The low rate of dialysis emergencies can be attributed to numerous safety features in modern dialysis machines; meticulous treatment and testing of the dialysate solution to prevent exposure to trace elements, toxins, and pathogens; adherence to detailed treatment protocols; and extensive training of dialysis staff to handle medical emergencies. Most hemodialysis emergencies can be attributed to human error. A smaller number are due to rare idiosyncratic reactions. In this review, we highlight major emergencies that may occur during hemodialysis treatments, describe their pathogenesis, offer measures to minimize them, and provide specific interventions to prevent catastrophic consequences on the rare occasions when such emergencies arise. These emergencies include dialysis disequilibrium syndrome, venous air embolism, hemolysis, venous needle dislodgement, vascular access hemorrhage, major allergic reactions to the dialyzer or treatment medications, and disruption or contamination of the dialysis water system. Finally, we describe root cause analysis after a dialysis emergency has occurred to prevent a future recurrence.

Bubbles and bypass: an update

Bubbles in the bloodstream are not a normal condition -yet they remain a fact of cardiopulmonary bypass (CPB), having been extensively studied and documented since its inception some 50 years ago. While detectable levels of gaseous microemboli (GME) have decreased significantly in recent years and gross air embolism has been nearly eliminated due to increased awareness of etiologies and technological advances, methods of use of current perfusion systems continue to elicit concerns over how best to totally eliminate GME during open-heart procedures. A few studies have correlated adverse neurocognitive manifestations associated with excessive quantities of GME.

Newer techniques currently in vogue, such as vacuum-assisted venous drainage, low-prime perfusion circuits, and carbon dioxide flooding of the operative field, have, in some instances, exacerbated the problem of gas embolism or engendered secondary complications in the safe conduct of CPB. Doppler monitoring (circuit or transcranial) primarily remains a research tool to detect GME emanating from the circuit or passing into the patients’ cerebral vasculature. Newer developments not yet widely available, such as multiple-frequency harmonics, may finally provide a tool to distinguish particulate microemboli from GME and further delineate the clinical significance of GME.

Effect of Normobaric versus Hypobaric Oxygenation on Gaseous Microemboli Removal in a Diffusion Membrane Oxygenator: An In Vitro Comparison

Gaseous microemboli (GME) are an abnormal physiological occurrence during cardiopulmonary bypass and extracorporeal membrane oxygenation (ECMO). Several studies have correlated negative sequelae with exposure to increased amounts of GME. Hypobaric oxygenation is effective at eliminating GME in hollow-fiber microporous membrane oxygenators. However, hollow-fiber diffusion membrane oxygenators, which are commonly used for ECMO, have yet to be validated. The purpose of this study was to determine if hypobaric oxygenation, compared against normobaric oxygenation, can reduce introduced GME when used on diffusion membrane oxygenators. Comparison of a sealed Quadrox-iD with hypobaric sweep gas (.67 atm) vs. an unmodified Quadrox-iD with normal atmospheric sweep gas (1 atm) in terms of GME transmission during continuous air introduction (50 mL/min) in a recirculating in vitro circuit, over a range of flow rates (3.5, 5 L/min) and crystalloid prime temperatures (37°C, 28°C, and 18°C). GME were measured using three EDAC Doppler probes positioned pre-oxygenator, post-oxygenator, and at the arterial cannula. Hypobaric oxygenation vs. normobaric oxygenation significantly reduced hollow-fiber diffusion membrane oxygenator GME transmission at all combination of pump flows and temperatures. There was further significant reduction in GME count between the oxygenator outlet and at the arterial cannula. Hypobaric oxygenation used on hollow-fiber diffusion membrane oxygenators can further reduce GME compared to normobaric oxygenation. This technique may be a safe approach to eliminate GME during ECMO.

Embolic Factors Associated with Cardiac Surgery

Macro and microemboli can both cause significant neurologic dysfunction. The traditional belief in cardiac surgery was that the damage perpetrated by an embolus was caused by the occlusion of an arterial branch, resulting in an ischemic event and subsequent infarction. However, ongoing research has demonstrated that the mere passage of a deformable embolus (air, lipid, or semi-solid clot) will disrupt the endothelium as it is extruded through the vessel. A cascade of events follows endothelial irritation. In the closed environment of the brain, a disruption of the blood-brain barrier has been demonstrated after the passage of lipid microemboli. A significant breakdown of the blood-brain barrier causes marked brain swelling, increased intracranial hypertension, and a possible increase in the size of the lesions associated with larger occlusive emboli. Gaseous microemboli are also a well-documented endothelial irritant and can cause significant brain dysfunction. It is important to avoid delivering emboli of any size or composition to the cerebral vasculature in order to reduce the impact of cardiac surgery on the brain.

Reducing Cerebral Emboli During Cardiopulmonary Bypass

Neurologic injury is a common complication of cardiac surgery and is associated with significant morbidity, mortality, and resource utilization. The incidence varies widely according to the definition used, patient age, and complexity of surgery. The manifestations of neurologic injury are broad, ranging from subtle neurocognitive dysfunction to frank stroke. An increasing amount of evidence points to cerebral embolization during cardiopulmonary bypass (CPB) as the principal etiologic factor of these neurologic complications. Cerebral emboli may be composed of atherosclerotic debris, calcium, air, fat, platelet thrombi, or CPB tubing. Advancements in perfusion technology, CPB techniques and surgical strategies may lead to a reduction in neurologic injury during cardiac surgery. In the current paper, we discuss the pathophysiology of neurologic injury after cardiac surgery and methods of reducing cerebral embolization. Reducing emboli and neurologic injury during CPB requires a multidisciplinary approach that includes several simple diagnostic and therapeutic strategies. Reducing cerebral emboli should be a major goal for future research in the fields of cardiac anesthesia, surgery and perfusion.

The dynamic bubble trap reduces microbubbles in extracorporeal circulation and high intensity transient signals in the middle cerebral artery: a case report

Microemboli during extracorporeal circulation (ECC) might be a reason for postoperative neuropsychological dysfunction. This case report shows that reduction of microbubbles in the arterial line, as well as high intensity transient signals (HITS) in the middle cerebral artery (MCA), could be accomplished by use of a dynamic bubble trap (DBT) during routine coronary artery bypass graft (CABG) surgery in a 63-year-old male. The DBT was placed after the arterial filter, an ultrasound Doppler device was used for detection of microemboli before and after the DBT. HITS were measured by a transcranial ultrasound Doppler in both MCAs. For first 32 min of ECC, the DBT was excluded; 54 916 microbubbles and 507 HITS were counted. In the next 30 min, blood flow was directed through the DBT. This led to a significant reduction of microbubbles from 55 888 to 18 237; accordingly, only 120 HITS were registered. A DBT, integrated in ECC for routine CABG, effectively reduces air bubbles, thus protecting the cerebrovascular system from micro-embolization, as demonstrated by lower HITS counts.

Use of a dynamic bubble trap in the arterial line reduces microbubbles during cardiopulmonary bypass and microembolic signals in the middle cerebral artery

Neurological complications remain an important cause of morbidity and mortality of patients following cardiopulmonary bypass (CPB). Microemboli, as well as cerebral hypoperfusion, are the main postulated mechanisms. This study demonstrates that the insertion of a dynamic bubble trap (DBT) into the curcuit reduces microbubbles in the arterial line and microembolic signals (MES) in the middle cerebral arteries (MCAs).

We investigated 12 patients during coronary artery bypass grafting (CABG). The DBT was inserted between the arterial filter and the arterial cannula. For detection of microemboli before and after the DBT, a special ultrasound Doppler device was used. MES were detected by transcranial Doppler monitoring in both MCAs of the patients. Microbubbles and MES were counted during bypass. These data were compared to 12 patients who were operated in a previous period without the use of a DBT. There were no significant differences in both groups with respect to gender, age, crossclamp and bypass time and number of anastomoses. In the group without a DBT in the circuit, a mean of 6311 microbubbles per operation could be observed distal to the arterial filter, corresponding to 282 MES. After inclusion of a DBT, we could register, in the second group, 8496 microemboli proximal and 2915 distal of the DBT, corresponding to 89 MES per operation. The reduction rate of microbubbles in the tubing was 65.7%, corresponding to a reduction in MES of about 86.2%. We conclude that the insertion of a DBT in the arterial line of CPB circuit protects the cerebrovascular system from microembolic events, as demonstrated by lower MES counts.

Carbon dioxide field flooding versus mechanical de-airing during open-heart surgery: a prospective randomized controlled trial

Removal of intracardiac air during valvular surgery should be accomplished in the most effective manner. We conducted a prospective randomized controlled trial to compare mechanical de-airing and carbon dioxide (CO2) field flooding in 18 patients undergoing elective valvular surgery. Transoesophageal echocardiography was used to record intracardiac bubbles, and this was assessed postoperatively by two independent echocardio-graphers blinded to treatment group. Both assessors graded the bubble count higher in the mechanical de-airing group compared with the CO2 flooding group, and there was good agreement between assessors. CO2 field flooding is more effective than mechanical de-airing in removing intracardiac bubbles following valvular surgery.

Isolated lung perfusion for pulmonary metastases, a review and work in progress

Pulmonary metastasectomy is a widely accepted treatment for many patients with pulmonary metastases from various solid tumors. Nevertheless, 5–year survival is disappointing, with rates of 25–40%, and many patients develop recurrences. Isolated lung perfusion (ILuP) is a promising new technique to deliver high–dose chemotherapy to the lungs, while minimising systemic toxicities. This procedure is technically safe and feasible; however, clinical value and efficacy remain unclear. The aim of this paper is to give a review of literature on ILuP in humans, and to describe the development of the perfusion procedure in our institute.

Comparison of conventional extracorporeal circulation and minimal extracorporeal circulation with respect to microbubbles and microembolic signals

The intention of minimal extracorporeal circulation (MECC) is to reduce priming volume and minimize contact of blood with polymers and air in a closed system. In contrast to conventional extracorporeal circulation (ECC), a venous reservoir is missing. Thus, air trapping is limited and avoidance of bubble embolism is a major concern. This study investigates microbubbles (MBB) number and size in the venous and arterial lines of ECC and MECC compared to the number of microembolic signals (MES) in the right and left middle cerebral artery (MCA).

Twenty patients undergoing coronary surgery were operated either with conventional ECC (cardiotomy reservoir, Rotaflow pump, Quadrox oxygenator, Quart filter) or MECC (Quart filter, Rotaflow pump, Quadrox oxygenator). Number and size of MBB were monitored in the venous and arterial lines with an ultrasound Doppler system. MES in right and left MCAs were measured by transcranial Doppler (TCD) monitoring. Patients undergoing MECC had additional sealing of the venous cannula by a ligature at the site of its insertion into the right atrium.

There were no significant differences between groups with respect to age, X-clamping, bypass time and number of distal anastomoses. The number of MES and MBB in the arterial line was comparable between the groups. On the venous side, MECC-perfusion shows a significantly lower number of MBB. This could be explained with the additional sealing of the venous cannula. Furthermore, our data indicate that the MBB-volume reaching the pump will also appear in the arterial outflow and into the patient’s MCA. For this reason, the avoidance of air contamination is a major concern for surgeons, anaesthesiologists and perfusionists.

Removal of Gross Air Embolization from Cardiopulmonary Bypass Circuits with Integrated Arterial Line Filters: A Comparison of Circuit Designs

Advances in technology, the desire to minimize blood product transfusions, and concerns relating to inflammatory mediators have lead many practitioners and manufacturers to minimize cardiopulmonary bypass (CBP) circuit designs. The oxygenator and arterial line filter (ALF) have been integrated into one device as a method of attaining a reduction in prime volume and surface area. The instructions for use of a currently available oxygenator with integrated ALF recommends incorporating a recirculation line distal to the oxygenator. However, according to an unscientific survey, 70% of respondents utilize CPB circuits incorporating integrated ALFs without a path of recirculation distal to the oxygenator outlet. Considering this circuit design, the ability to quickly remove a gross air bolus in the blood path distal to the oxygenator may be compromised. This in vitro study was designed to determine if the time required to remove a gross air bolus from a CPB circuit without a path of recirculation distal to the oxygenator will be significantly longer than that of a circuit with a path of recirculation distal to the oxygenator. A significant difference was found in the mean time required to remove a gross air bolus between the circuit designs (p = .0003). Additionally, There was found to be a statistically significant difference in the mean time required to remove a gross air bolus between Trial 1 and Trials 4 (p = .015) and 5 (p =.014) irrespective of the circuit design. Under the parameters of this study, a recirculation line distal to an oxygenator with an integrated ALF significantly decreases the time it takes to remove an air bolus from the CPB circuit and may be safer for clinical use than the same circuit without a recirculation line.

[GAS MICROEMBOLISM DURING EXTRACORPOREAL CIRCULATION]

INTRODUCTION

Over the past 20 years, there are many studies, where great attention is paid to the gas and material embolism as the cause of cognitive impairment in patients undergoing surgery with cardiopulmonary bypass.

PURPOSE

To identify the filter capacity of 4 extracorporeal circuits for removing gaseous microemboli in various interventions on the heart and aorta.

MATERIAL AND METHODS

Work carried out on 60 patients operated on acquired heart and aorta under cardiopulmonary bypass. We used 4 different extracorporeal circuits, divided into groups of 15 patients. Quality and quantity of gaseous microemboli recorded in real time on the device BCC-200 GAMPT (Germany).

RESULTS

According to two indicators: Vol. Red (reduction in the volume of gas microemboli) and Fl (filter index) the best results were obtained after statistical processing systems Medtronic and Terumo, followed by Maquet system and Eurosets.

CONCLUSION

BCC-200 device allows identifying the sources of gaseous microemboIi. The perfusionist, having on-line information time about the number of microemboli coming in heart-lung machine can increase patient safety, using the capabilities of a particular extracorporeal circuit and minimize the amount of emboli from entering the patient's arterial line.

Should Air Bubble Detectors Be Used to Quantify Microbubble Activity during Cardiopulmonary Bypass?

Air bubble detectors (ABDs) are utilized during cardiopulmonary bypass (CPB) to protect against massive air embolism. Stockert (Munich, Germany) ABD quantify microbubbles >300 μm; however, their reliability has not been reported. The aim of this study was to assess the reliability of the microbubble data from the ABD with the SIII and S5 heart-lung machines. Microbubble counts from the ABD with the SIII (SIII ABD) and S5 (S5 ABD) were measured simultaneously with the emboli detection and classification (EDAC) quantifier in 12 CPB procedures using two EDAC detectors and two ABDs in series in the arterial line. Reliability was assessed by the Spearman correlation co-efficient (r) between measurements for each detector type, and between each ABD and EDAC detector for counts >300 μm. No correlation was found between the SIII ABD (r = .008, p = .793). A weak negative correlation was found with the S5 ABD (r = -.16, p < .001). A strong correlation was found between the EDAC detectors (SIII; r = .958, p < .001), (S5; r = .908, p < .001). With counts >300 μm, the SIII ABDs showed a correlation of small-medium effect size between EDAC detectors and ABD1 (r = .286, p < .001 [EDAC1], r = .347, p < .001 [EDAC2]). There was no correlation found between ABD2 and either EDAC detector (r = .003, p = .925 (EDAC1), r = .003, p = .929 [EDAC2]). A correlation between EDAC and the S5 ABD, was not able to be determined due to the low bubble count detected by the EDAC >300 μm. Both SIII ABD and S5 ABD were found to be unreliable for quantification of microbubble activity during CPB in comparison with the EDAC. These results highlight the importance of ensuring that data included in the CPB report is accurate and clinically relevant, and suggests that microbubble counts from devices such as the SIII ABD and S5 ABD should not be reported.

[SURGICAL TECHNIQUE OF A RENAL ARTERY CONTROL WHILE REMOVAL OF TUMORAL THROMBI FROM VENA CAVA INFERIOR]

Efficacy and safety of a renal artery ligation after thrombectomy in comparison with those while using a standard surgical technique were studied. Possibility of performance and safety of thrombectomy without preliminary ligation of renal artery was proved. The results did not depend on level of intravenous tumoral spread and were significantly better, than while application of standard approaches to renal artery because of absence of embolic complications.

Effects of line type blood-liquid warmer on two different infusion sets

OBJECTIVE

To investigate the source of 'bubbles' in infusion sets which were caused by the 'line type' blood-liquid warmers used in operation rooms to prevent hypothermia.

METHODS

The experimental study was conducted from August to September 2012 at the Thoracic Surgery Department of Dokuz Eylul University, Izmir, Turkey, by warming liquids in the operation room experimentally in a setting similar to clinical routine. Initially, 0.9% sodium chloride solution was infused using S-line blood-liquid warmers with Medisetin patients who were placed in Group M). The IPC Group had Intrafix Primeline Confortset at a rate of 350ml/hour in the operating room. The initiation time and level of bubble formation, temperatures of the operation room, infusion liquid, S-line device, line of the device, and the liquid at the outflow were recorded. Data was analysed with SPSS 15.

RESULTS

The two groups had 10 subjects each. The temperatures of the working area, the liquid before and after being placed in the warming device, the proximal-middle and distal parts of the line and the set temperature on the screen of the device were similar and the difference between them was not statistically significant (p>0.05). While no bubble formation was observed in Group IPC, bubbles were formed after 9.80±0.78 minutes and the level of bubble formation was close to 3 in Group Mediset (2.80±1.03). The main difference between the two groups was di (2-ethylhexyl) phthalate content of Mediset.

CONCLUSIONS

Infusion sets containing di(2-ethylhexyl) phthalate should not be used with warming devices in order to avoid toxic effects.

Safety Testing of Left Ventricular Vent Valves

Vent vacuum relief valves (VRVs) are used to limit the negative pressure at the ventricular vent catheter tip as well as prevent reversal of blood flow and prevention of air embolism. The purpose of this study was to evaluate the performance of three commercially available ventricular vent valves. The negative pressure at which the vent valve opened was measured at the valve inlet using high-fidelity pressure transducers. Also, the flow rate at which air entrainment occurred due to valve opening was recorded. Using a 51.5 cm column of saline, the resistance for each valve was calculated. The mean ± SD opening negative pressures were -231.3 ± 35.2 mmHg for the Quest Medical valve, -219.8 mmHg ± 17.2 for the Sorin valve, and -329.6 · 38.0 mmHg for the Terumo valve. The red Quest Medical valve opened at a lower flow (1.44 ± .03 L/min) than the dark blue Sorin valve (2.93 ± .01 L/min) and light blue LH130 Terumo valve (2.36 ± .02 L/min). The Sorin valve had the least resistance of 34.1 dyn-s/cm, followed by the Terumo LH130 valve resistance of 58.1 dyn·s/cm5, and the Quest Medical VRV-II valve with a resistance of 66.5 dyn·s/cm. We found that the valves are significantly different in the negative pressure generated. Understanding the limitations of these devices is important to reduce the occurrence of adverse events associated with venting and to select the best device for a specific clinical application.

Air embolism during insertion and replacement of tunneled dialysis catheters: a retrospective investigation of the effect of aerostatic sheaths and over-the-wire exchange

PURPOSE

To determine the impact of the introduction of aerostatic sheaths on air embolism (AE) events during tunneled dialysis catheter (TDC) insertion and to characterize such events occurring during over-the-wire exchange (OTWE).

MATERIALS AND METHODS

Between July 2001 and April 2013, 5,789 TDCs were placed, including 3,963 de novo placements, 1,811 OTWEs, and 15 tract recanalizations. There were 15 AE events reported, and the medical records of these patients were reviewed. The effect of aerostatic sheaths, introduced in July 2005, was compared with the period before their introduction; the same TDC design was used throughout.

RESULTS

Of the 15 AE events, 10 occurred during de novo placement (10 of 3,963 placement; 0.25%), 4 occurred during OTWE (4 of 1,811 placements; 0.22%), and 1 occurred during tract recanalization. With regard to aerostatic sheaths in de novo TDC placement, 4 of 1,174 (0.34%) AE events occurred before aerostatic sheath introduction, and 6 of 2,789 (0.22%) AE events occurred after aerostatic sheath introduction. These rates did not differ statistically (P = .5).

CONCLUSIONS

Use of aerostatic sheaths trended toward reducing AE events during de novo TDC placement. This trend was not statistically significant, probably owing to the rarity of AE despite the large sample size. Air embolism occurs during OTWE at a rate similar to de novo placement with aerostatic sheaths as well as during tract recanalization.

Medical devices; general hospital and personal use devices; classification of the intravascular administration set, automated air removal system. Final order

The Food and Drug Administration (FDA) is classifying the intravascular administration set, automated air removal system into class II (special controls). The special controls that will apply to the device are identified in this order and will be part of the codified language for the intravascular administration set, automated air removal system's classification. The Agency is classifying the device into class II (special controls) in order to provide a reasonable assurance of safety and effectiveness of the device.

Can the oxygenator screen filter reduce gaseous microemboli?

Gaseous microemboli (GME) define small bubbles as < 200 microm in size. GME are reported to increase morbidity after cardiopulmonary bypass (CPB) and cardiac surgery. To prevent intrusion of GME into the systemic circulation during CPB, arterial line filtration is generally recommended. New trends in oxygenator design promote location of arterial filtration as an integral part of the oxygenator housing. The present experimental study aimed to evaluate the GME removal properties of an integrated arterial screen filter in a standard microporous oxygenator. The GME properties of Terumo Capiox FX25 with an integrated arterial screen filter was assessed in an experimental setup and compared with Capiox RX25, in which no arterial screen filter is present. A blood analog prime solution was recirculated using a roller pump at 4 and 6 L per minute flow rate, respectively, through a customized CPB circuit comprising oxygenator, reservoir, and connecting tubing. A controlled volume of air was introduced into the circuit. The GME activity was measured and computed using a Gampt BCC200 ultrasonic device placing one probe at the venous inlet and one other at the arterial outlet of the oxygenator. Transmembrane delta values of GME activity were used to calculate the removal efficacy based on counts and volume of GME. Use of screen filtration reduced the GME volume by 99.1% +/- .1% compared with 98.0% +/- .1% for controls at 4 L/min flow rate (p < .001). At 6 L/min, the reduction was 97.9% +/- .1% compared with 97.0% +/- .1% (p < .001). In contrast, the reduction of GME counts was less effective after screen filtration compared with controls: 89.6 +/- .6% versus 91.4 +/- .4% at 4 L/min and 55.6% +/- 1.6% versus 76.0% +/- 1.4% at 6 L/min, respectively (p < .001). The tested oxygenator with incorporated arterial screen filter reduced GME activity based on the calculated volume at the same time as counts of GME increased.

[Iatrogenic gas embolism]

Gas embolism is the entry of air or medical gases into the blood circulation following invasive procedures, surgery, trauma or diving. The mortality of symptomatic gas embolism is high. Time is of the essence when initiating treatment, and gas embolism is often easily prevented. In this article, aetiology, frequency, pathophysiology, symptoms, diagnosis, treatment, outcome and prevention of both venous and arterial iatrogenic gas embolism are reviewed.

[Clinical study on echocardiography combined with end-tidal CO2 monitoring in preventing the venous air embolism during operative hysteroscopy]

OBJECTIVE

To explore the value of transthoracic echocardiography(TTE) combined with partial pressure of end-tidal CO2 (P ETCO2) monitoring in preventing venous air embolism(VAE) during hysteroscopy operation.

METHODS

From August 2010 to August 2012, 300 cases undergoing hysteroscopic surgery under general anaesthesia were enrolled in this study. With the echocardiography combined with P ETCO2 monitoring during hysteroscopic surgery, the time of VAE appearing in the right atrium , the extent of air embolism(grade 0-4), the changes of P ETCO2, peripheral oxygen saturation (SpO2), blood pressure (Bp), the amount of fluid intravasation and the blood loss were recorded in detail . Take the 24 cases that the grades of VAE in grade 3 or above and a decrease in P ETCO2 ≥ 5 mm Hg (1 mm Hg = 0.133 kPa) as intervention group. Stop operation immediately, the left side and raise your right shoulder, oxygen inhalation and dexamethasone 10 mg intravenous drip were given to the intervention group; the control group (5 cases in grade 3 or above and a decrease in P ETCO2<5 mm Hg) only stop operation immediately, observation patient's condition closely.

RESULTS

(1) The occurrence of VAE: air embolism occurred in 34 patients among all 300 patients, all of 34 patients had evidence of gas embolism in the inferior vena cava, right atrium(RA) and right ventricle chamber, and 29 patients had evidence of continuous groups of gas emboli. There were 32 cases with the decrease in P ETCO2 > 2 mm Hg, 14 cases with SpO2 less than 95%, and 4 cases with a drop in Bp ≥ 20%. (2) The change of the decrease of P ETCO2 and the grades of VAE: the decrease of P ETCO2 and the grades of VAE were positively correlated (r = 0.601, P < 0.01), continuous groups of gas emboli signal in RA, when the drop of P ETCO2 ≥ 5 mm Hg, 8 of the 34 cases whose drop of P ETCO2 ≥ 10 mm Hg, 7 cases in grades 4. The decrease of P ETCO2 [(7.5 ± 2.4) mm Hg versus (11.1 ± 4.1) mm Hg], the amount of fluid intravasation[(688 ± 150) ml versus (925 ± 268) ml] and the blood loss[(71 ± 36) ml versus (127 ± 56) ml] all had statistical difference in grade 3 and 4 (P < 0.05) . The sensitivity of P ETCO2 was better than SpO2 and Bp in detecting of VAE. (3) The cases of P ETCO2 continue to decline and recovery time between the two groups:2 cases' P ETCO2 continued to decline in the intervention group, but 4 cases in the control group. The recovery time of the two groups was (4.8 ± 1.6) and (8.3 ± 1.9) min, respectively, which reached statistical difference between (P < 0.05).

CONCLUSIONS

TTE combined with P ETCO2 monitoring can effectively predict the occurrence of air embolism in hysteroscopic surgery; Continuous groups of gas emboli signal in RA accompanied by a decrease in P ETCO2 ≥ 5 mm Hg indicates that the occurrence of air embolism; the more the amount of intravasation of distension fluid and the blood loss, the more the air into the body. Timely intervention can effectively prevent the development of air embolism when the VAE in grade 3 or above accompanied by a decrease in P ETCO2 ≥ 5 mm Hg.

Submarine rescue decompression procedure from hyperbaric exposures up to 6 bar of absolute pressure in man: effects on bubble formation and pulmonary function

Recent advances in submarine rescue systems have allowed a transfer under pressure of crew members being rescued from a disabled submarine. The choice of a safe decompression procedure for pressurised rescuees has been previously discussed, but no schedule has been validated when the internal submarine pressure is significantly increased i.e. exceeding 2.8 bar absolute pressure. This study tested a saturation decompression procedure from hyperbaric exposures up to 6 bar, the maximum operating pressure of the NATO submarine rescue system. The objective was to investigate the incidence of decompression sickness (DCS) and clinical and spirometric indices of pulmonary oxygen toxicity. Two groups were exposed to a Nitrogen-Oxygen atmosphere (pO2 = 0.5 bar) at either 5 bar (N = 14) or 6 bar (N = 12) for 12 h followed by 56 h 40 min resp. 60 h of decompression. When chamber pressure reached 2.5 bar, the subjects breathed oxygen intermittently, otherwise compressed air. Repeated clinical examinations, ultrasound monitoring of venous gas embolism and spirometry were performed during decompression. During exposures to 5 bar, 3 subjects had minor subjective symptoms i.e. sensation of joint discomfort, regressing spontaneously, and after surfacing 2 subjects also experienced joint discomfort disappearing without treatment. Only 3 subjects had detectable intravascular bubbles during decompression (low grades). No bubbles were detected after surfacing. About 40% of subjects felt chest tightness when inspiring deeply during the initial phase of decompression. Precordial burning sensations were reported during oxygen periods. During decompression, vital capacity decreased by about 8% and forced expiratory flow rates decreased significantly. After surfacing, changes in the peripheral airways were still noticed; Lung Diffusion for carbon monoxide was slightly reduced by 1% while vital capacity was normalized. The procedure did not result in serious symptoms of DCS or pulmonary oxygen toxicity and may be considered for use when the internal submarine pressure is significantly increased.

Vacuum assist: angel or demon CON

Vacuum-assisted venous drainage (VAVD) to enhance venous return during cardiopulmonary bypass (CPB) was described as early as 1958 but was not widely used until the late 1990s. VAVD was initially used to facilitate the use of smaller cannulas with ministernotomy but was increasingly used to allow reduction in CPB circuit size while maintaining CPB flow rates. This innovation was made without planned consideration to CPB circuit design, most critically that of the venous reservoir. Clinical reports of prime reduction facilitated by VAVD in both adult and pediatric CPB were associated with reduced nadir hematocrit and rates of transfusion that encouraged the proliferation of VAVD in CPB. Concomitantly, investigators have reported both in vitro and in vivo significantly increased arterial emboli associated with the use of VAVD, mostly related to accelerated venous air entrainment. In vitro studies continue to confirm this association and likely underestimate the resulting embolic load as a result of flawed study design. While the evidence for VAVD is equivocal, our understanding of the clinical impact of gaseous microemboli in CPB is similarly limited, most likely confined to blood-brain barrier disruption. It is only after two decades that CPB component design is receiving serious attention in terms of air handling. The ethics of innovation in the field of CPB warrant careful consideration. The application of VAVD is not without consequence.

Vacuum-assisted venous drainage, angel or demon: PRO?

Vacuum-assisted venous drainage (VAVD) was proposed to optimize venous drainage during bypass through femoral venous cannulation. It is currently used in both adult and pediatric surgery when siphon gravity venous drainage is suboptimal. In pediatric surgery, the major advantages of VAVD are a significant decrease in cardiopulmonary bypass prime volume and an improved drainage with all collateral benefits. To limit gravity drainage, we use a two-level heart-lung machine dedicated to pediatric perfusion. The top level of the cardiotomy reservoir is positioned at the patient atrial level, making it possible to downsize the length and diameter of venous and arterial lines. Since 2008, a negative pressure of approximately -30 mmHg has been used for all patients. Initiation of bypass is performed in a classical way with a cardiotomy reservoir open; vacuum is added as soon as the maximal gravity drainage is reached. During bypass, when the blood level in the reservoir decreases to the safety limit level, a small increase in negative pressure is used to improve venous drainage. For weaning from bypass, the negative pressure is gradually decreased to zero, then the reservoir is opened and the venous line progressively closed. Prime volumes were significantly reduced to 100 mL for small neonates, 125 mL for infants, and 175 mL for older children with flow up to 1.5 L/min(-1). A low prime volume is expected to improve blood conservation and decrease donor exposure, prevent drawbacks of transfusion (immunomodulation, infection), increase the incidence of blood-free surgery in smaller babies, and decrease whole body systemic inflammation by decreasing surface of foreign material in contact with blood and inflammation associated with blood transfusion. The main drawbacks described have been retrograde flow in the venous line with cerebral air embolus and an increased incidence of gaseous microemboli. These drawbacks are avoidable through appropriate training of perfusionists. When negative pressure is "reasonable," complications are more theoretical than significant in clinical practice. A technique with a benefit/drawback ratio of 1:0 is utopian, but the advantages of VAVD far outweigh any potential drawbacks when applied properly.

Nonfatal air embolism during shoulder arthroscopy

An air embolism is a rare but potentially fatal complication of shoulder arthroscopy. In this article, we report the case of a patient who developed a nonfatal air embolism during shoulder arthroscopy for an acute bony Bankart lesion and a greater tuberosity avulsion fracture. The venous air embolism occurred immediately after the joint was insufflated with air for diagnostic air arthroscopy. The diagnosis was based on a drop in end-tidal carbon dioxide and blood pressure and presence of mill wheel (waterwheel) murmur over the right heart. Supportive treatment was initiated immediately. The patient recovered fully and had no further complications of air embolism. This patient's case emphasizes the importance of being aware that air embolisms can occur during shoulder arthroscopy performed for acute intra-articular fractures of the shoulder. Monitoring end tidal carbon dioxide can be very useful in early detection of air embolisms.

Microbubble transmission during cardiotomy infusion of a hardshell venous reservoir with integrated cardiotomy versus a softshell venous reservoir with separated cardiotomy: an in vitro comparison

An important mechanism for postoperative cognitive impairment after cardiac surgery using cardiopulmonary bypass (CPB) is microemboli. One component of the CPB circuit-the cardiotomy-is a major source of gaseous microemboli because it aspirates significant volumes of air with blood from the operative field and intracardiac chambers. Cardiotomies are either integrated within an open hardshell venous reservoir (IC-HSVR) or are a separate canister attached to a softshell collapsible venous reservoir bag (SC-SSVR). The purpose of this study was to compare the Medtronic IC-HSVR (Affinity NT CVR) with Medtronic's SC-SSVR (CB 1351, CBMVR 1600) in terms of relative microbubble transmission during cardiotomy infusion. A recirculating in vitro circuit primed with blood was used to compare the two cardiotomy-reservoir systems with the venous reservoir in the SC-SSVR further assessed in a fully closed or partially open state (SC-SSVR-closed; SC-SSVR-open). Microbubbles were detected using a GAMPT BC100 Doppler system in the outflow line of the venous reservoir. Measurements were taken before (baseline) and after aerated prime was pumped into the cardiotomy while altering pump flow rates (3 L/min; 5 L/min) and reservoir prime volumes (400 mL; 900 mL). Infusing cardiotomy blood into the venous reservoir was associated with an increase in microbubbles and bubble volume transmitted by both cardiotomy-reservoir systems with the magnitude rising with reduced prime volumes. The effect was markedly greater with the IC-HSVR. The IC-HSVR also transmitted larger bubbles, particularly with reduced prime volumes. There was no significant difference in microbubble transmission seen between the SC-SSVR-closed and SC-SSVR-open. The SC-SSVR transmits fewer microbubbles than the IC-HSVR during cardiotomy infusion and should be considered as the preferential system. Because both cardiotomy-reservoir systems transmitted microbubbles during cardiotomy infusion, particularly at the lower venous reservoir volume, it is important to use strategies to minimize cardiotomy microbubble infusion.