A survey on air bubble detector placement in the CPB circuit: a 2011 cross-sectional analysis of the practice of Certified Clinical Perfusionists.

The ideal location of air bubble detector (ABD) placement on the cardiopulmonary bypass (CPB) circuit is debatable. There is, however, very little data characterizing the prevalence of specific ABD placement preferences by perfusionists. Therefore, the purpose of this study was to survey the perfusion community to collect data describing the primary locations of air bubble detector placement on the CPB circuit. In June 2011, an 18-question on-line survey was conducted. Completed surveys were received from 627 participants. Of these, analysis of the responses from the 559 certified clinical perfusionists (CCP) was performed. The routine use of ABD during CPB was reported by 96.8% of CCPs. Of this group, specific placement of the bubble detector is as follows: distal to the venous reservoir outlet (35.6%), between the arterial pump and oxygenator (3.8%), between the oxygenator and arterial line filter (35.1%), distal to the arterial line filter (ALF) (23.6%), and other (1.8%). Those placing the ABD distal to the venous reservoir predominately argued that an emptied venous reservoir was the most likely place to introduce air into the circuit. Those who placed the ABD between the oxygenator and the arterial line filter commonly reasoned that this placement protects against air exiting the membrane. Those placing the ABD distal to the ALF (23.6%) cited that this location protects from all possible entry points of air. A recent false alarm event from an ABD during a case was reported by 36.1% of CCPs. This study demonstrates that the majority of CCPs use an ABD during the conduct of CPB. The placement of the ABD on the circuit, however, is highly variable across the perfusion community. A strong rationale for the various ABD placements suggests that the adoption of multiple ABD may offer the greatest comprehensive protection against air emboli.

2010 Survey on cell phone use while performing cardiopulmonary bypass.

Cell phone use in the U.S. has increased dramatically over the past decade and text messaging among adults is now mainstream. In professions such as perfusion, where clinical vigilance is essential to patient care, the potential distraction of cell phones may be especially problematic. However, the extent of this as an issue is currently unknown. Therefore, the purpose of this study was to (1) determine the frequency of cell phone use in the perfusion community, and (2) to identify concerns and opinions among perfusionists regarding cell phone use. In October 2010, a link to a 19-question survey (surveymonkey.com) was posted on the AmSECT (PerfList) and Perfusion.com (PerfMail) forums. There were 439 respondents. Demographic distribution is as follows; Chief Perfusionist (30.5%), Staff Perfusionist (62.0%), and Other (7.5%), with age ranges of 20-30 years (14.2%), 30-40 years (26.5%), 40-50 years (26.7%), 50-60 years (26.7%), >60 years (5.9%). The use of a cell phone during the performance of cardiopulmonary bypass (CPB) was reported by 55.6% of perfusionists. Sending text messages while performing CPB was acknowledged by 49.2%, with clear generational differences detected when cross-referenced with age groups. For smart phone features, perfusionists report having accessed e-mail (21%), used the internet (15.1%), or have checked/posted on social networking sites (3.1%) while performing CPB. Safety concerns were expressed by 78.3% who believe that cell phones can introduce a potentially significant safety risk to patients. Speaking on a cell phone and text messaging during CPB are regarded as "always an unsafe practice" by 42.3% and 51.7% of respondents, respectively. Personal distraction by cell phone use that negatively affected performance was admitted by 7.3%, whereas witnessing another perfusionist distracted with phone/text while on CPB was acknowledged by 33.7% of respondents. This survey suggests that the majority of perfusionists believe cell phones raise significant safety issues while operating the heart-lung machine. However, the majority also have used a cell phone while performing this activity. There are clear generational differences in opinions on the role and/or appropriateness of cell phones during bypass. There is a need to further study this issue and, perhaps, to establish consensus on the use of various communication modes within the perfusion community.

Fatigue and extended work hours among cardiovascular perfusionists: 2010 Survey.

Due to the emergent unpredictable nature of cardiac surgery, perfusionists, potentially, are susceptible to extended work hours and acute sleep deprivation. While fatigue among other healthcare clinicians has been studied, there has been no research on this topic specifically in the perfusion community. Therefore, the purpose of this study was to: (1) collect preliminary data on the prevalence of fatigue in perfusion and (2) identify if there were concerns regarding fatigue, performance and perfusion safety. In May 2010, a link to a 50-question survey (surveymonkey.com) was posted on Perflist and Perfmail. The survey was closed in July 2010. There were 445 respondents and data were analyzed and expressed as a response percent. Participants included 27% chief perfusionists/managers, 67% staff perfusionists, and 6.0% other (perfusion education faculty, retired perfusionists, locum tenens). Regarding extended work hours, 68.9% of surveyed perfusionists have worked at the hospital for greater than 23 hours straight and 17.5% have worked continuously for over 36 hours. Actual performance of cardiopulmonary bypass (CPB) after 17, 23, and 36 hours of wakefulness was reported by 82.9%, 63% and 14.8% respondents, respectively. Regarding bathroom requirements while on CPB, 87.5% have felt extremely uncomfortable at least once, 19.9% have relieved themselves in the operating room at least once, and 22.3% have left the pump attended by a non-perfusionist to use the restroom at least once. Microsleep during CPB was reported by 49.5% of respondents. Automobile accidents attributed to an extended period of work and fatigue was reported by 6.9% and another 44.4% reported a near-miss auto accident. A fatigue-related minor error was reported by 66% and 6.7% admit to having a serious perfusion accident believed to be due to fatigue. Concerning critical phases of bypass, 51.5% believe that they perform less effectively when fatigued. Additionally, 75.9% indicate that they have been concerned about their ability to perform their job adequately due to fatigue-related acute sleep deprivation. Opinions regarding workplace management were as follows; 48% believe that fatigue can play a role in our profession and managers should do what they can to provide a rested staff, but, unfortunately, it is impractical to set work limits; 32.2% believe fatigue issues should be taken more seriously and specific guidelines should be stated by our professional organizations and 13.4% believe that limits should be established, legislated, and enforced by state or federal authorities. Based upon this preliminary survey data, it appears that fatigue and acute sleep deprivation is a significant safety concern in the perfusion community. Further research must be performed to understand actual performance degradation that may occur in fatigued perfusionists performing CPB.

Matrix metalloproteinase inhibitor prevents acute lung injury after cardiopulmonary bypass.

BACKGROUND: Acute lung injury (ALI) after cardiopulmonary bypass (CPB) results from sequential priming and activation of neutrophils. Activated neutrophils release neutral serine, elastase, and matrix metalloproteinases (MMPs) and oxygen radical species, which damage alveolar-capillary basement membranes and the extracellular matrix, resulting in an ALI clinically defined as adult respiratory distress syndrome (ARDS). We hypothesized that treatment with a potent MMP and elastase inhibitor, a chemically modified tetracycline (CMT-3), would prevent ALI in our sequential insult model of ALI after CPB. METHODS AND RESULTS: Anesthetized Yorkshire pigs were randomized to 1 of 5 groups: control (n=3); CPB (n=5), femoral-femoral hypothermic bypass for 1 hour; LPS (n=7), sham bypass followed by infusion of low-dose Escherichia coli lipopolysaccharide (LPS; 1 microgram/kg); CPB+LPS (n=6), both insults; and CPB+LPS+CMT-3 (n=5), both insults plus intravenous CMT-3 dosed to obtain a 25-micromol/L blood concentration. CPB+LPS caused severe lung injury, as demonstrated by a significant fall in PaO(2) and an increase in intrapulmonary shunt compared with all groups (P<0.05). These changes were associated with significant pulmonary infiltration of neutrophils and an increase in elastase and MMP-9 activity. CONCLUSIONS: All pathological changes typical of ALI after CPB were prevented by CMT-3. Prevention of lung dysfunction followed an attenuation of both elastase and MMP-2 activity. This study suggests that strategies to combat ARDS should target terminal neutrophil effectors.

Multiple sequential insults cause post-pump syndrome.

BACKGROUND: We hypothesize that post-pump syndrome (PPS) following cardiopulmonary bypass (CPB) can be caused by multiple minor insults and that the mechanism of PPS is a priming and subsequent activation of polymorphonuclear (PMN) leukocytes. In this study extensive pathophysiologic and morphometric assessment was undertaken in a porcine model of sequential insult PPS. METHODS: Pigs were anesthetized, placed on a ventilator, instrumented for measurements of hemodynamic function, and separated into five groups: (1) Control (n = 4)--surgery only, (2) CPB (n = 4)--placed on femoral-femoral hypothermic (28 degrees C) bypass for 1 h, (3) LPS (n = 6)--underwent sham CPB followed by infusion of low dose endotoxin [E. coli lipopolysaccharide (LPS-1 microg/kg)], (4) Heparin + protamine + LPS (HP + LPS, n = 4)--were heparinized without CPB for 1 h, following which protamine and LPS were infused and (5) CPB + LPS (n = 8)--subjected to both CPB and LPS. RESULTS: Only CPB + LPS resulted in acute respiratory distress typical of PPS as indicated by a significant decrease in PaO2 and increase in intrapulmonary shunt fraction (p<0.05). CPB + LPS significantly increased tissue density and the number of sequestered monocytes and PMNs (p<0.05) above all other groups. Alveolar macrophages (AM) increased equally in all groups receiving LPS. CONCLUSIONS: CPB primes the inflammatory system causing pulmonary PMN sequestration without lung injury. Exposure to an otherwise benign dose of endotoxin results in activation of the sequestered PMNs causing PPS. This study confirms that PPS can be caused by multiple minor insults.

Status of pediatric perfusion education: 2000 survey.

In recent years, studies have raised questions about pediatric perfusion training, minimum proficiency requirements, and specialization. To understand these questions better, a survey was undertaken to investigate the status of pediatric/neonatal perfusion training in the United States. Three groups were surveyed: program directors (PD), recent graduates of perfusion programs (RG), and pediatric cardiac anesthesiologists (PCA). Program directors and recent graduates were queried about didactic curriculum and clinical experiences. All three groups were asked core questions regarding minimum proficiency, specialization, and need for a postgraduate style program. Didactically, 65% of program directors believed that perfusion programs provided a solid introductory knowledge base in infant perfusion. Clinically, students performed an average of 124 +/- 42.5 adult and 17 +/- 12.9 pediatric cases during their education. Program directors cited numerous limitations to clinical pediatric education, including access to pediatric cases and allocation of resources. The PD (69%) and RG (96%) both believed graduates were less prepared to perform infant/pediatric cardio-pulmonary bypass (CPB) at graduation as compared to adult CPB. The opinions of all three groups were divided when asked whether the essentials and guidelines requirement for minimum pediatric caseload is too low (yes response: PD 52%, RG 73%, PCA 47%). The PD and RG were against pediatric subspecialization/certification (87%, 57% respectively); whereas, the PCA were unanimously in favor (100%) of pediatric subspecialization/certification for perfusionist. All three groups felt a postgraduate-style program in infant perfusion would benefit the community (78%, 82%, 100%). Finally, 64% of RG said that, if available, they would have considered entering a training program in pediatric/neonatal perfusion after graduation. Our results indicate that there are still limitations to pediatric perfusion education. A postgraduate-style program in infant perfusion is one possible solution to this problem.

Investigations into the sterility of manually assembled extracorporeal circuits with vented reservoirs.

This study was designed to investigate the ability of an extracorporeal circuit (ECC) with a vented hard shell reservoir to remain sterile for a period of 72 h under dry conditions. The study was conducted in three phases. In Phase One: Two previously published methods for detecting contamination of the ECC were compared. A group of positive controls was collected by contaminating identical circuits with a known level of Enterobacter cloacae (ATTC: 13047) before initiating a regimen of "sample-dilute-sample" culturing. Negative controls for this phase were conducted by randomly sampling 1 L per manufacturer's lot of lactated ringers with each detection method. Culture results suggest that large volume filtration, but not small aliquot sampling, is sensitive to extremely low levels of contamination. No growth was detected in any negative control samples. In Phase Two: 19 ECC consisting of a membrane oxygenator, vented hardshell reservoir, arterial filter, and PVC tubing were removed from their sterile packages, assembled, and left unprotected in the moderate traffic environment of a research laboratory. The circuits were then primed with Lactated Ringer's solution. The prime solution was sampled for aerobic contamination by large volume filtration. None of the 19 samples detected contamination. In Phase Three: 43 ECC identical to the Phase Two circuits were assembled and left unprotected in the substerile pump room. The circuits were then primed, circulated, and cultured as in Phase Two. One of the 43 samples was discarded because of a recognized break in aseptic technique during sample collection. None of the remaining samples detected contamination. Mathematical calculations of binomial probabilities suggest that the chance of an open ECC developing a detectable level of contamination within 72 h of its dry assembly is insignificant.

Evidence of increased matrix metalloproteinase-9 concentration in patients following cardiopulmonary bypass.

Cardiopulmonary bypass (CPB) is associated with a systemic inflammatory response, which can result in acute lung injury known as "postperfusion syndrome." Neutrophil activation with concomitant serine protease release has been implicated in the pathogenesis of "postperfusion syndrome." Increased plasma levels of neutrophil elastase (NE) have been demonstrated in patients undergoing CPB, and it is well documented that both NE and matrix metalloproteinase-9 (MMP-9) have a synergistic role in pulmonary injury. We, therefore, hypothesized that plasma levels of MMP-9 would be elevated in patients after CPB. Human plasma was obtained after informed consent from eight patients undergoing CPB. Plasma was collected at the start of CPB, 5 minutes after the initiation of CPB, and at the termination of CPB (156 +/- 17 min). All samples were analyzed by both standard enzyme-linked immunosorbent assay (ELISA) and gelatin zymography for MMP-9 (free and total enzyme) concentration. Data were expressed as means +/-SE and assessed by analysis of variance (ANOVA). Plasma MMP-9 concentration was significantly increased at the end of CPB (191 +/- 30.4 ng/mL; p <.05) as compared to both the start of CPB (28.3 +/- 13.2 ng/mL) and 5 minutes after the initiation of CPB (44.3 +/- 15.4 ng/mL). Patients undergoing CPB show an increase in serum MMP-9 levels. Prior studies utilizing an animal model of "postperfusion syndrome" have shown that inhibition of MMP-9 and NE prevented pulmonary injury following CPB. The results of the current study suggest that such an approach may also have merit in the clinical setting of cardiopulmonary bypass.

Systemic inflammation induced by cardiopulmonary bypass: a review of pathogenesis and treatment.

The acute respiratory distress syndrome (ARDS) is a severe alteration in lung structure and function that develops secondary to a traumatic stimulus. When ARDS develops following cardiopulmonary bypass (CPB) it is know as postpump syndrome (PPS). ARDS can be caused by a single massive insult ("hit"); however, sequential minor insults ("hits") are more common clinically. The concept of multiple sequential insults causing ARDS has been termed the "two-hit" model of ARDS. The purpose of this article is to summarize our studies testing the hypothesis that PPS is caused by multiple sequential insults. To confirm our hypothesis, we developed a porcine model of "two-hit" PPS. Our model was composed of sequential benign insults, with CPB as the "first hit" and low dose of endotoxin as the "second-hit." It is our hypothesis that the mechanism of PPS is CPB-induced priming of polymorphonuclear leukocytes (PMNs) ("first-hit") with subsequent PMN activation by a second insult ("second-hit") such as endotoxin. Our model confirms this clinically relevant postulate, and we provide strategies to disrupt the inflammatory cascade leading to PPS.

Matrix metalloproteinase inhibitor: differential effects on pulmonary neutrophil and monocyte sequestration following cardiopulmonary bypass.

UNLABELLED: Acute respiratory distress syndrome (ARDS) following cardiopulmonary bypass (CPB), also known as "post-pump" or "post-perfusion syndrome" (PPS), results from sequential priming and activation of neutrophils. We hypothesized that chemically modified tetracycline (CMT-3) an inhibitor of neutrophil matrix metalloproteinase (MMP) and elastase, would prevent PPS. We performed histometric analysis of lung tissue from our porcine PPS model to correlate cellular sequestration and histologic injury with CMT-3 treatment. METHODS: Yorkshire pigs were randomized into five groups: Control (n = 3); CPB (n = 5); femoral-femoral bypass 1 hour; LPS (n = 7), Escherichia coli lipopolysaccharide (1 microgram/kg); CPB + LPS (n = 6); and CPB + LPS + CMT (n = 5), sequential insults and CMT-3. Protocol histometric analysis defined cellular and tissue components of lung injury. RESULTS: CMT-3 decreased neutrophil sequestration in the CPB + LPS + CMT-3 group (p < 0.0001 vs. CPB + LPS). There were no differences in monocytes between CPB + LPS and CPB + LPS + CMT treatment groups. CONCLUSIONS: CMT-3 attenuates neutrophil sequestration but has no effect on mononuclear sequestration in our PPS model. This finding supports current research on leukocyte chemokines and has important implications regarding mechanisms of CMT-3. Despite lack of monocyte response to CMT-3, PPS was prevented by inhibiting neutrophils alone; confirming the primary role of neutrophils in PPS.

Soluble tumor necrosis factor receptor prevents post-pump syndrome.

Post-pump syndrome is an acute lung injury following cardiopulmonary bypass (CPB) which is indistinguishable from the adult respiratory distress syndrome (ARDS). Tumor necrosis factor (TNF) is central to the inflammatory process and is capable of triggering the entire pathophysiologic response leading to ARDS. We hypothesized that treatment with a soluble TNF receptor-binding protein (TNFbp) would reduce the increase in serum TNF and prevent acute lung injury in our sequential insult model of ARDS following CPB. Anesthetized pigs were randomized to one of three groups: Control (n = 3), surgical preparation only; CPB + LPS (n = 6), femoral-femoral hypothermic bypass for 1 h followed by infusion of low dose Escherichia coli lipopolysaccharide (LPS; 1 microg/kg); and TNFbp + CPB + LPS (n = 4), pretreatment with intravenous TNFbp (2 mg/kg) followed immediately by both insults. CPB + LPS caused severe lung injury demonstrated by a significant fall in PaO2 and an increase in both intrapulmonary shunt and peak airway pressure as compared to all groups (P < 0.05). These changes were associated with a significant increase in plasma TNF level and pulmonary neutrophil sequestration. TNFbp significantly reduced plasma levels of TNF and prevented the lung injury typically observed with this ARDS model, but did not reduce pulmonary neutrophil sequestration. Thus, elevated serum TNF is not responsible for neutrophil sequestration but does play a role in neutrophil activation which causes lung injury. Prophylactic use of TNFbp in CPB patients may prevent neutrophil activation and reduce the incidence of post-pump ARDS.