Evaluation of N95 respirators, modified snorkel masks and low-cost powered air-purifying respirators: a prospective observational cohort study in healthcare workers.

Disposable N95 respirator masks are the current standard for healthcare worker respiratory protection in the COVID-19 pandemic. In addition to shortages, qualitative fit testing can have low sensitivity for detecting poor fit, leading to inconsistent protection. Multiple groups have developed alternative solutions such as modified snorkel masks to overcome these limitations, but validation of these solutions has been lacking. We sought to determine if N95s and snorkel masks with attached high-efficiency filters provide consistent protection levels in healthcare workers and if the addition of positive pressure via an inexpensive powered-air purifying respirator to the snorkel mask would provide enhanced protection. Fifty-one healthcare workers who were qualitatively fitted with N95 masks underwent quantitative mask fit testing according to a simulated workplace exercise protocol. N95, snorkel masks with high-efficiency filters and snorkel masks with powered-air purifying respirators were tested. Respiratory filtration ratios were collected for each step and averaged to obtain an overall workplace protocol fit factor. Failure was defined as either an individual filtration ratio or an overall fit factor below 100. N95s and snorkel masks with high-efficiency filters failed one or more testing steps in 59% and 20% of participants, respectively, and 24% and 12% failed overall fit factors, respectively. The snorkel masks with powered-air purifying respirators had zero individual or overall failures. N95 and snorkel masks with high-efficiency filter respirators were found to provide inconsistent respiratory protection in healthcare workers.

The association between platelet dysfunction and adverse outcomes in cardiac surgical patients.

Haemostatic activation during cardiopulmonary bypass is associated with prothrombotic complications. Although it is not possible to detect and quantify haemostatic activation directly, platelet dysfunction, as measured with point-of-care-assays, may be a useful surrogate. In this study, we assessed the association between cardiopulmonary bypass-associated platelet dysfunction and adverse outcomes in 3010 cardiac surgical patients. Platelet dysfunction, as measured near the end of the rewarming phase of cardiopulmonary bypass, was calculated as the proportion of non-functional platelets after activation with collagen. Logistic regression and multivariable analyses were applied to assess the relationship between platelet dysfunction and a composite of in-hospital death; myocardial infarction; stroke; deep vein thrombosis or pulmonary embolism; and acute kidney injury (greater than a two-fold increase in creatinine). The outcome occurred in 251 (8%) of 3010 patients. The median (IQR [range]) percentage platelet dysfunction was less for those without the outcome as compared with those with the outcome; 14% (8-28% [1-99%]) vs. 19% (11-45% [2-98%]), p < 0.001. After risk adjustment, platelet dysfunction was independently associated with the composite outcome (p < 0.001), such that for each 1% increase in platelet dysfunction there was an approximately 1% increase in the composite outcome (OR 1.012; 95%CI 1.006-1.018). This exploratory study suggests that cardiopulmonary bypass-associated platelet dysfunction has prognostic value and may be a useful clinical measure of haemostatic activation in cardiac surgery.

Use of prothrombin complex concentrate for management of coagulopathy after cardiac surgery: a propensity score matched comparison to plasma.

BACKGROUND: An important cause of coagulopathy in cardiac surgery is impaired thrombin generation. While plasma is often used to correct this element of the coagulopathy, studies in vitro suggest that prothrombin complex concentrates (PCCs) might be more effective. Comparative data, however, are scant. METHODS: We compared the outcomes of those who received only plasma with those who received PCCs (with or without plasma) for management of coagulopathy in patients who underwent cardiac surgery with cardiopulmonary bypass at a single institution from 2012 to 2016. Propensity score matching was used to obtain between-group balance. Primary outcome was avoidance of perioperative red cell transfusions. Other outcomes were incidence of massive transfusion (more than nine red cell units), refractory bleeding (requiring factor VIIa), and adverse events. RESULTS: Of 6362 patients, 1151 (18.2%) received plasma without any PCCs, and 204 (3.2%) received PCCs, either with (n=125) or without plasma (n=79). Overall, patient risk-profile was higher in the PCCs group. In a well-balanced propensity score match that included 117 patients per group, the odds ratio (OR) for red cell avoidance was 2.4-fold [95% confidence interval (CI) 1.2-4.8] higher in the PCCs group. Massive transfusion (OR 0.58; 95% CI 0.33-1.0) and refractory bleeding (OR 0.49; 95% CI 0.24-1.03) incidences were almost significantly lower in the PCCs group. The adverse event profiles were similar. CONCLUSIONS: Our exploratory study suggests that the use of PCCs as part of a multifaceted coagulation management strategy may have blood-sparing effects. Their incorporation into clinical practice, however, must await determination of their risk-benefit profile via multicentre randomised trials.

Systematic review and consensus definitions for the Standardised Endpoints in Perioperative Medicine (StEP) initiative: renal endpoints.

BACKGROUND: Renal injury is a common perioperative complication. The adoption of renal endpoints, standardised and valid for use in perioperative clinical trials, would enhance the quality of perioperative clinical research. The Standardised Endpoints in Perioperative Medicine (StEP) initiative was established to derive standardised endpoints for use in perioperative clinical trials. METHODS: A systematic review was conducted to identify renal endpoints currently reported in perioperative clinical trials. In parallel, an initial list of candidate endpoints was developed based on renal theme group expertise. A multi-round Delphi consensus process was used to refine this list and produce a suite of recommended perioperative renal outcome measures. RESULTS: Based on our systematic review, 63 studies were included for analysis. Marked heterogeneity and imprecision of endpoint definitions were observed. Our initial list of candidate endpoints included 10 endpoints for consideration. The response rates for Delphi rounds 1, 2, and 3 were 89% (n=16), 90% (n=75), and 100% (n=6), respectively. A final list of four renal endpoints was identified: acute kidney injury defined by the Kidney Disease: Improving Global Outcomes (KDIGO) consensus criteria, acute kidney disease defined by ≥30% decline in estimated glomerular filtration rate from baseline at 30 days after operation in patients meeting the acute-kidney-injury criteria within 7 days of surgery, the composite of death or renal replacement therapy, and the Major Adverse Kidney Events (MAKE) composite. CONCLUSIONS: We identified four key renal outcome measures that should be considered for use in perioperative clinical trials. Using standardised definitions to capture and report these endpoints will facilitate improved benchmarking and meta-analysis of future trials.

Pre-operative anaemia, intra-operative hepcidin concentration and acute kidney injury after cardiac surgery: a retrospective observational study.

Acute kidney after cardiac surgery is more common in anaemic patients, whereas haemolysis during cardiopulmonary bypass may lead to iron-induced renal injury. Hepcidin promotes iron sequestration by macrophages: hepcidin concentration is reduced by anaemia and increased by inflammation. We analysed the associations in 525 patients between pre-operative anaemia (haemoglobin < 130 g.l-1 in men and < 120 g.l-1 in women), intra-operative hepcidin concentration and acute kidney injury (dialysis or > 26.4 µmol.l-1 or > 50% creatinine increase during the first two days after cardiac surgery. Rates of pre-operative anaemia and postoperative kidney injury were 109/525 (21%) and 36/525 (7%), respectively. The median (IQR [range]) intra-operative hepcidin concentration was 20 (10-33 [0-125]) µg.l-1 and was lower in anaemic patients than those who were not: 15 (4-28 [0-125]) µg.l-1 vs. 21 (12-33 [0-125]) µg.l-1 , respectively, p = 0.002. Four variables were independently associated with postoperative kidney injury, for which the beta-coefficients (SE) were: minutes on cardiopulmonary bypass, 0.016 (0.004), p < 0.001; intra-operative hepcidin concentration, 0.032 (0.008), p < 0.001; pre-operative anaemia, 1.97 (0.56), p < 0.001; and Cleveland clinic risk score, 0.88 (0.35), p = 0.005. Contrary to generally increased rates of kidney injury in patients with higher hepcidin concentrations, rates of kidney injury in anaemic patients were lower in patients with higher hepcidin concentrations, beta-coefficient (SE) -0.037 (0.01), p = 0.007. In cardiac surgical patients the rate of postoperative acute kidney injury predicted by the Cleveland risk score might be adjusted for pre-operative anaemia and intra-operative cardiopulmonary bypass time and hepcidin concentration. Pre-operative correction of anaemia, reduction in intra-operative bypass time and modification of iron homeostasis and hepcidin concentration might reduce acute kidney injury.

Effectiveness of platelet inhibition on major adverse cardiac events in non-cardiac surgery after percutaneous coronary intervention: a prospective cohort study.

BACKGROUND: Platelet inhibition is mandatory therapy after percutaneous coronary intervention (PCI). Withdrawal of oral antiplatelet agents has been linked to increased incidence of postoperative adverse cardiac events in post-PCI patients having non-cardiac surgery (NCS). There is limited knowledge of temporal changes in platelet inhibition in this high-risk surgical population. We therefore performed a multicentre prospective cohort study evaluating perioperative platelet function and its association with postoperative major adverse cardiac events (MACE). METHODS: In 201 post-PCI patients having NCS, we assessed the association between platelet function and postoperative MACE. We performed perioperative platelet function testing using a platelet mapping assay (PMA). Troponin-I was measured every 8 h for 2 days, then daily until day 5. Myocardial infarction was assessed using the third universal definition. We used multivariable logistic regression to assess the association between platelet inhibition and MACE. RESULTS: Major adverse cardiac events occurred in 40 patients within 30 days of surgery. Thirty-two of these events were non-ST-elevation myocardial infarction, four ST-elevation myocardial infarction, and four exacerbation of congestive heart failure. We were unable to show an association between platelet inhibition and MACE. The PMA showed declining levels of platelet inhibition the longer the antiplatelet therapy was withheld before surgery. Logistic regression did not show an association between preoperative platelet function or the type of stent and MACE. We found an increased cardiac risk of MACE after surgery within 6 weeks of PCI. CONCLUSIONS: The incidence of MACE in patients undergoing NCS after previous PCI is high in spite of adequate perioperative antiplatelet therapy. CLINICAL TRIAL REGISTRATION: NCT 01707459 (registered at http://www.clinicaltrials.gov).

The pathophysiology and consequences of red blood cell storage.

Red cell transfusion therapy is a common treatment modality in contemporary medical practice. Although blood collection and administration is safer and more efficient than ever before, red cells undergo multiple metabolic and structural changes during storage that may compromise their functionality and viability following transfusion. The clinical relevance of these changes is a hotly debated topic that continues to be a matter of intense investigation. In the current review, we begin with an in-depth overview of the pathophysiological mechanisms underlying red cell storage, with a focus on altered metabolism, oxidative stress and red cell membrane damage. We proceed to review the current state of evidence on the clinical relevance and consequences of the red cell storage lesion, while discussing the strengths and limitations of clinical studies.

The role of point-of-care platelet function testing in predicting postoperative bleeding following cardiac surgery: a systematic review and meta-analysis.

This systematic review and meta-analysis appraises the utility of point-of-care platelet function tests for predicting blood loss and transfusion requirements in cardiac surgical patients, and analyses whether their use within a transfusion management algorithm is associated with improved patient outcomes. We included 30 observational studies incorporating 3044 patients in the qualitative assessment, and nine randomised controlled trials including 1057 patients in the meta-analysis. Platelet function tests demonstrated significant variability in their ability to predict blood loss and transfusion requirements. Their use within a blood transfusion algorithm demonstrated a reduction in blood loss at longest follow-up (mean difference -102.9 ml (95% CI -149.9 to -56.1 ml), p < 0.001), and transfusion of packed red cells (RR 0.86 (95% CI 0.78-0.94), p = 0.001) and fresh frozen plasma (RR 0.42 (95% CI 0.30-0.59), p < 0.001). Viscoelastic methods used in combination with other platelet function tests achieved greater reduction in blood loss (mean difference -111.8 ml (95% CI -174.9 to -49.1 ml), p = 0.0005) compared with their use alone (mean difference -90.6 ml (95% CI 166.1-15.0 ml), p = 0.02). We conclude that incorporation of point-of-care platelet function tests into transfusion management algorithms is associated with a reduction in blood loss and transfusion requirements in cardiac surgery patients.

Transfusion and risk of acute kidney injury in cardiac surgery.

Acute kidney injury (AKI) is a serious and common complication of major surgery. This narrative review focuses on the relationship between perioperative red blood cell transfusion and AKI after cardiac surgery with cardiopulmonary bypass (CPB). Numerous observational studies have shown that these two factors are independently associated with each other. Several lines of evidence suggest that the nature of this association is one of cause and effect. The pathophysiological mechanism by which transfusions might harm the kidney has not been fully elucidated, but it is known that erythrocytes undergo irreversible morphological and biochemical changes during storage. As a result, after transfusion, they can promote a pro-inflammatory state, impair tissue oxygen delivery, and exacerbate tissue oxidative stress. This in turn can cause AKI in susceptible patients undergoing cardiac surgery with CPB, such as those with pre-existing kidney dysfunction or anaemia. Interventions aimed at avoiding perioperative blood transfusion might, therefore, reduce the risk of AKI after cardiac and other types of surgery.

Antithrombotic therapy management of adult and pediatric cardiac surgery patients.

Despite the development of catheter-based interventions for ischemic and valvular heart disease, hundreds of thousands of people undergo open heart surgery annually for coronary artery bypass graft (CABG), valve replacement or cardiac assist device implantation. Cardiac surgery patients are unique because therapeutic anticoagulation is required during cardiopulmonary bypass. Developmental hemostasis and altered drug metabolism affect management in children. This narrative review summarizes the current evidence-based and consensus guidelines regarding perioperative, intraoperative and postoperative antithrombotic therapy in patients undergoing cardiac surgery. Anticoagulation preoperatively is required in the setting of cardiac arrhythmias, prior valve replacement or history of venous thromboembolism. In patients with ischemic heart disease, aspirin is continued in the perioperative period, whereas oral P2Y12 antagonists are withheld for 5-7 days to reduce the risk of perioperative bleeding. Intraoperative management of cardiopulmonary bypass in adults and children includes anticoagulation with unfractionated heparin. Variability in dose-response to heparin and influence of other medical conditions on dosing and reversal of heparin make intraoperative anticoagulation challenging. Vitamin K antagonist therapy is the standard anticoagulant after mechanical heart valve or left ventricular assist device (LVAD) implantation. Longer duration of dual antiplatelet therapy is recommended after CABG if patients undergo surgery because of acute coronary syndrome. Antiplatelet therapy after LVAD implantation includes aspirin, dipyridamole and/or clopidogrel in children and aspirin in adults. A coordinated approach between hematology, cardiology, anesthesiology, critical care and cardiothoracic surgery can assist to balance the risk of thrombosis and bleeding in patients undergoing cardiac surgery.

Hemodilution during cardiopulmonary bypass is an independent risk factor for acute renal failure in adult cardiac surgery.

BACKGROUND: This observational study sought to determine whether the degree of hemodilution during cardiopulmonary bypass is independently related to perioperative acute renal failure necessitating dialysis support. METHODS: Data were prospectively collected on consecutive patients undergoing cardiac operations with cardiopulmonary bypass from 1999 to 2003 at a tertiary care hospital. The independent relationship was assessed between the degree of hemodilution during cardiopulmonary bypass, as measured by nadir hematocrit concentration, and acute renal failure necessitating dialysis support. Multivariate logistic regression was used to control for variables known to be associated with perioperative renal failure and anemia. RESULTS: Of the 9080 patients included in the analysis, 1.5% (n = 134) had acute renal failure necessitating dialysis support. There was an independent, nonlinear relationship between nadir hematocrit concentration during cardiopulmonary bypass and acute renal failure necessitating dialysis support. Moderate hemodilution (nadir hematocrit concentration, 21%-25%) was associated with the lowest risk of acute renal failure necessitating dialysis support; the risk increased as nadir hematocrit concentration deviated from this range in either direction (P = .005). Compared with moderate hemodilution, the adjusted odds ratio for acute renal failure necessitating dialysis support with severe hemodilution (nadir hematocrit concentration <21%) was 2.34 (95% confidence interval, 1.47-3.71), and for mild hemodilution (nadir hematocrit concentration >25%) it was 1.88 (95% confidence interval, 1.02-3.46). CONCLUSIONS: Given that there is an independent association between the degree of hemodilution during cardiopulmonary bypass and perioperative acute renal failure necessitating dialysis support, patient outcomes may be improved if the nadir hematocrit concentration during cardiopulmonary bypass is kept within the identified optimal range. Randomized clinical trials, however, are needed to determine whether this is a cause-effect relationship or simply an association.

The effects of a treatment protocol for cardiac surgical patients with excessive blood loss on clinical outcomes.

BACKGROUND AND OBJECTIVES: Excessive blood loss (EBL) is a common complication of cardiac surgery that is associated with adverse events. The objective of this before/after study was to determine whether the implementation of a protocol for management of cardiac surgical patients with EBL was associated with improved clinical outcomes. MATERIALS AND METHODS: In November 2002, a protocol for prompt identification and aggressive management of cardiac surgical patients with EBL was implemented at our institution. The independent relationship between protocol implementation and adverse outcomes was measured by comparing the outcomes of patients who received > or = 4 RBC (red blood cell) units within 1 day of surgery and were operated on before protocol implementation (2000-02) with those operated on after protocol implementation (2003-05), using multivariable logistic regression analysis to control for the effects of confounders. The primary outcome was a composite of adverse events that included death, renal failure, stroke, and sepsis. Bootstrapping was used to confirm the validity of the results. RESULTS: Of the 11,314 patients who underwent surgery during the study period, 1875 (16.6%) received > or = 4 RBC units within 1 day of surgery, with 958 and 917 in the pre- and postprotocol periods, respectively. The composite adverse outcome occurred in 164 (17.1%) patients in the preprotocol period and 115 (12.5%) patients in the postprotocol period (P = 0.005). Protocol implementation was independently associated with reduced odds of the composite adverse outcome (odds ratio 0.67; 95% confidence interval 0.50, 0.91; P = 0.01). This estimate was stable in bootstrap sampling. CONCLUSION: Implementation of a protocol to manage EBL in cardiac surgery was independently associated with improved outcomes.

A multivariable model for predicting the need for blood transfusion in patients undergoing first-time elective coronary bypass graft surgery.

BACKGROUND: The incidence of blood transfusion in coronary artery bypass graft (CABG) surgery remains high. Preoperative identification of those at high risk for requiring blood will allow for the cost-effective use of some blood conservation modalities. Multivariable analysis techniques were used in this study to develop a prediction rule for such a purpose. STUDY DESIGN AND METHODS: Data were prospectively collected for all patients undergoing elective first-time CABG surgery from January 1997 to September 1998 at a tertiary-care teaching hospital (n = 1007). The prediction rule was developed on the first two-thirds of the sample by using logistic regression methods to examine the relationship of patient demographics, comorbidities, and preoperative Hb with perioperative blood transfusion. The remaining one-third of the sample was used to validate the rule. RESULTS: The transfusion rate was 29.4 percent. The prediction rule included preoperative Hb (g/dL, OR 0.928, p<0.0001), weight (kg, OR 0.938, p<0.0001), age (years, OR 1.037, p<0.01), and sex (male/female, OR 0.493, p<0.01); receiver operating characteristic = 0.86. When externally validated, the rule had a sensitivity of 82.1 percent and a specificity of 63.6 percent (at a selected probability cutoff). CONCLUSION: A simple and valid prediction rule is developed for predicting the risk of blood transfusion in patients undergoing first-time elective CABG surgery.

Predicting difficult intubation: a multivariable analysis.

PURPOSE: To develop a clinically useful and valid model for predicting difficult laryngoscopic tracheal intubation in patients with seemingly normal airways by adhering to the principles of multivariable model development. METHODS: This was an observational study performed at a tertiary-care teaching hospital. Preoperatively, 444 randomly selected patients requiring tracheal intubation for elective surgery were assessed. In addition, 27 patients in whom tracheal intubation was difficult, but were not assessed preoperatively, were assessed postoperatively. One assessor, blinded to the intubation information, collected the predictor variables. A reliable definition for difficult intubation was used and all attempts were made to eliminate sources of bias. Multivariable modeling was performed using logistic regression and the model was validated using the bootstrapping technique. RESULTS: Of the 461 patients included in the analysis, 38 were classified as difficult to intubate. Multivariable analysis identified three airway tests that were highly significant for predicting difficult tracheal intubation. These were: 1) "mouth opening", 2) "chin protrusion", and 3) "atlanto-occipital extension". Using these tests, a validated, highly reliable and predictive model is produced to determine the probability of difficult intubation for patients. At a selected probability cut-off value, the model is 86.8% sensitive and 96.0% specific. CONCLUSION: A simple and accurate multivariable model, consisting of three airway tests, is produced for predicting difficult laryngoscopic tracheal intubation. Additional studies will be required to determine the accuracy and feasibility of this model when applied to a large sample of new patients by multiple anesthesiologists.

Inter-observer reliability of ten tests used for predicting difficult tracheal intubation.

PURPOSE: To determine inter-observer reliability of ten preoperative airway assessment tests used for predicting difficult tracheal intubation. METHOD: We prospectively assessed 59 patients undergoing elective surgery requiring tracheal intubation at a large metropolitan teaching hospital. Two experienced observers independently conducted the airway assessment tests on the same group of patients. Inter-observer reliability was examined using Kappa (K) and intraclass correlation coefficient (ICC). RESULTS: Two tests--mouth opening (ICC = 0.93) and chin protrusion (ICC = 0.89)--had excellent inter-observer reliability. Seven tests--thyromental distance (ICC - 0.74), subluxation (K = 0.66), atlanto-occipital extension distance (ICC = 0.67) and angle (K = 0.66), profile classification (K = 0.58), ramus length (ICC = 0.53), oropharyngeal best view (K = 0.49)--were moderately reliable. One test--Mallampati technique of assessing oropharyngeal view (K = 0.31)--had poor reliability. CONCLUSION: Many of the preoperative airway tests have only moderate inter-observer reliability. This may provide some insight into why previous research has failed to show that the tests accurately predict difficult tracheal intubation.