Evaluation of leukocyte-reducing arterial line filter (LG6) for postoperative lung function, using cardiopulmonary bypass

Leukodepletion for patients undergoing heart valve surgery

BACKGROUND

There is some evidence for the benefits of leukodepletion in patients undergoing coronary artery surgery. Its effectiveness in higher risk patients, such as those undergoing heart valve surgery, particularly in terms of overall clinical outcomes, is currently unclear.

OBJECTIVES

To assess the beneficial and harmful effects of leukodepletion on clinical, patient-reported and economic outcomes in patients undergoing heart valve surgery.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (2013, Issue 3 of 12) in The Cochrane Library, the NHS Economic Evaluations Database (1960 to April 2013), MEDLINE Ovid (1946 to April week 2 2013), EMBASE Ovid (1947 to Week 15 2013), CINAHL (1982 to April 2013) and Web of Science (1970 to 17 April 2013) on 19 April 2013. We also searched the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP), the US National Institutes of Health (NIH) clinical trials database and the International Standard Randomised Controlled Trial Number Register (ISRCTN) in April 2013 for ongoing studies. No language or time period restrictions were applied. We examined the reference lists of all included randomised controlled trials and contacted authors of identified trials. We searched the 'grey' literature at OpenGrey and handsearched relevant conference proceedings.

SELECTION CRITERIA

Randomised controlled trials comparing a leukocyte-depleting arterial line filter with a standard arterial line filter, on the arterial outflow of the heart-lung bypass circuit, in elective patients undergoing heart valve surgery.

DATA COLLECTION AND ANALYSIS

Data were collected on the study characteristics, three primary outcomes (1. post-operative in-hospital all-cause mortality within three months, 2. post-operative all-cause mortality excluding inpatient mortality < 30 days, 3. length of stay in hospital, 4. adverse events and serious adverse events) and seven secondary outcomes (1. tubular or glomerular kidney injury, 2. validated health-related quality of life scales, 3. validated renal injury scales, 4. use of continuous veno-venous haemo-filtration, 5. length of stay in intensive care, 6. costs of care). Data were extracted by one author and verified by a second author. Insufficient data were available to perform a meta-analysis or sensitivity analysis.

MAIN RESULTS

Eight studies were eligible for inclusion in the review but data on prespecified review outcomes were available from only one, modestly powered (24 participants) study (Hurst 1997). There were no differences between a leuko-depleting versus standard filter in length of stay in the intensive care unit (ICU) (mean difference (MD) 0.80 days; 95% confidence interval (CI) -0.24 to 1.84) or length of hospital stay (MD 0.20 days; 95% CI -1.78 to 2.18).

AUTHORS' CONCLUSIONS

There are currently insufficient good quality trials with valve surgery patients to inform recommendations for changes in clinical practice. A future National Institute for Health Research (NIHR)-funded feasibility study (recruiting mid-year 2013) comparing leukodepletion with a standard arterial line filter in patients undergoing elective heart valve surgery (the ROLO trial) will be the largest study to date and will make a significant contribution to future updates of this review.

The effects of various leukocyte filtration strategies in cardiac surgery

It is known that cardiopulmonary bypass causes an inflammatory reaction with an associated morbidity and mortality. Several anti-inflammatory strategies have been implemented to reduce this response, including leukocyte removal from the circulation using specialised filters. The aim of this study is to systematically review the available evidence on leukocyte filtration in cardiac surgery, focusing on its effect on systemic inflammation and whether this has influenced clinical outcomes. Five electronic databases were systematically searched for studies reporting the effect of leukocyte filtration at any point within the cardiopulmonary bypass circuit in humans. Reference lists of all identified studies were checked for any missing publications. Two authors independently extracted the data from the included studies. Whilst systemic leukodepleting filters do not appear to consistently lower leukocyte counts, they may preferentially remove activated leukocytes. Small improvements in early post-operative lung function in patients receiving systemic leukodepletion have been reported, but this does not lead to reduced hospital stay or decreased mortality. There is substantial evidence that cardioplegic leukocyte filtration attenuates the reperfusion injury at a cellular level, but this has not been translated into clinical improvements. Finally, whilst various strategies involving multiple leukocyte filters, or the incorporation of pharmacological agents into leukocyte-depleting protocols have been evaluated, the current available results are not conclusive. Our study suggests that there is not enough high quality or consistent evidence to draw guidelines regarding the use of leukocyte-depleting filters within routine cardiac surgical practice.

Reducing risk in infant cardiopulmonary bypass: the use of a miniaturized circuit and a crystalloid prime improves cardiopulmonary function and increases cerebral blood flow

Advances in perfusion strategies have played an important role in improving outcomes following repair of complex congenital heart defects. The influence of cooling strategy, temperature, duration of circulatory arrest, and specific method of cerebral perfusion on neurologic morbidity have been extensively characterized. Similarly, the ability of pharmacologic agents to modulate the post-cardiopulmonary bypass (CPB) inflammatory response has been previously elucidated in both the laboratory and clinical arena. However, modification of the circuit and priming components have received comparably less attention. We recently showed that employment of a miniaturized circuit and a bloodless prime reduce inflammation and have salutary effects on cardiopulmonary function following hypothermic low-flow perfusion (HLF), and that this circuit may also improve cerebral protection following both deep hypothermic circulatory arrest and HLF. The current report, therefore, reviews current strategies utilized to minimize post-CPB inflammation and highlights the empirical evidence from our laboratory demonstrating the beneficial role of a miniaturized extracorporeal circuit in this context.

Clinical Effectiveness of Leukocyte Filtration During Cardiopulmonary Bypass in Patients with Chronic Obstructive Pulmonary Disease

BACKGROUND

We tested the hypothesis that leukocyte filtration during pulmonary reperfusion preserves pulmonary function and results in improved oxygenation after cardiopulmonary bypass (CPB) in patients with chronic obstructive pulmonary disease (COPD).

METHODS

In a prospective, randomized study, the treatment group consisted of 20 patients with COPD from consecutive open-heart procedures. A primed leukocyte filter was connected to the arterial line downstream of the standard arterial filter but was excluded from circulation. Circulated blood was directed through the leukocyte filter approximately 10 minutes before aortic cross-clamp removal and at early reperfusion for up to 30 minutes. These patients were compared to 20 additional COPD patients (controls) on whom systemic leukocyte filtration was not used during open-heart surgery.

RESULTS

There was no significant difference in gender, age, left ventricular ejection fraction, type of procedure, aortic cross-clamp time, perfusion time, preoperative FEV1 and preoperative respiratory index (Pao2/FiO2 ratio) between treatment and control groups. The respiratory index changed in the treatment group by +9.8% of baseline after completion of CPB, by -14.2% upon arrival in the intensive care unit (ICU), and by -19.6% 12 hours later, whereas in the control group, it changed by -14.5% (p < 0.05), -27.7%, and -24%, respectively. Leukocyte-depleted patients required shorter intubation time (20.4 +/- 16.1 hours), ICU stay (46.2 +/- 40.1 hours) and length of hospitalization (8.3 +/- 2.8 days) than controls (29.5 +/- 21.9 hours, p < 0.05; 75.5 +/- 34.9 hours, p < 0.005; and 10.4 +/- 3.5 days, p < 0.05, respectively). Surgical (30-day) mortality was zero in both groups.

CONCLUSIONS

In COPD patients having CPB, systemic leukocyte depletion at early reperfusion was associated with better oxygenation, shorter intubation time, and shorter ICU and hospital stays. Leukocyte filtration during CPB most likely preserves pulmonary function by ameliorating pulmonary reperfusion injury.

The inflammatory response to CPB: the role of leukocyte filtration

Leukocyte activation is a significant component of the systemic inflammatory response to cardiopulmonary bypass (CPB). Various strategies have been developed aiming to reduce leukocyte activation and its deleterious effects on organ function after cardiac surgery. Leukocyte filtration aims to physically remove activated leukocytes from the circulation during CPB. The technique has been used since the mid-1990s but its efficacy in attenuating the effects of inflammatory response remains controversial. This article presents a review of published trials investigating the effects of leukocyte filtration on humans undergoing cardiac surgery.

A review of leukofiltration in cardiac surgery: the time course of reperfusion injury may facilitate study design of anti-inflammatory effects

The systemic inflammatory response syndrome (SIRS) is a well-recognized phenomenon attending cardiopulmonary bypass (CPB) surgery. SIRS leads to costly complications and several strategies intended to ameliorate the symptoms have been studied, including leukocyte reduction using filtration. Although the body of work suggests that leukoreduction attenuates SIRS, discrepancies remain within the literature. The recent literature is reviewed, highlighting the areas where concordance is lacking. Investigations into many promising device-related technologies are often deterred by the high costs of clinical trials. Adding to costs is the fact that clinical end points generally require large sample sizes. An understanding, however, of the pathogenesis of reperfusion injury can guide the investigator to choose physiologic response measures that correlate well with clinical outcome, but feature low inherent variability, allowing for clinical trials with smaller sample sizes. With this goal in mind, a model for the pathogenesis of reperfusion injury is described. Using a model of reperfusion injury as underpinnings for the design of prospective pilot studies, we show that salvaged blood reinfused following CPB elicits time-dependent effects on pulmonary function as predicted by the model. Data are illustrative of principles that could expand the scope of clinical investigations designed to validate the use of physiologic response measures as correlates of clinical outcome. Such investigations would target surrogate markers of clinical outcome, measured at clinically relevant times. Once validated, these surrogate markers would, thereafter, become economical screening tools for clinical studies of device-related or pharmacological anti- inflammatory interventions.

Antiinflammatory effect of heparin-coated circuits with leukocyte-depleting filters in coronary bypass surgery

Cardiac surgery with cardiopulmonary bypass is associated with a systemic inflammatory response. We examined combined use of heparin coating of the cardiopulmonary bypass circuit and a leukocyte-depleting arterial line filter to reduce this response. Thirty patients were allocated randomly to equal groups with a conventional circuit and arterial line filter (C group), a heparin-coated circuit with a conventional filter (H group), or a heparin-coated circuit with a leukocyte-depleting arterial line filter (HF group). Cytokines and respiratory function were repeatedly measured perioperatively. Plasma interleukin (IL)-6 concentrations in the HF group were lower than in the C group immediately following bypass and operation, at 4 h, and 12 h (p < 0.05). Plasma IL-8 was lower in the HF group than in the C group at 4 h (p < 0.05). The respiratory index was lower immediately after bypass in the HF group than the C group (0.61 +/- 0.2 versus 1.05 +/- 0.4, p < 0.05). Heparin-coated circuits with leukocyte-depleting filters decrease inflammatory responses and improve pulmonary function during operation.

Leukocyte filtration in cardiac surgery: a review

Leukocyte filtration has evolved as an important technique in cardiac surgery with cardiopulmonary bypass to prevent pathogenic effector functions mediated by activated leukocytes. The underlying mechanisms that result in an improvement of laboratory variables as well as clinical outcome are not resolved yet. Moreover, the optimum strategy for the use of current filtration technology has not been systematically evaluated. This paper, therefore, reviews how activated leukocytes may lead to tissue damage, summarizes the known effects of leukocyte filtration on clinical outcome and laboratory parameters, and deals with current experimental and clinical efforts to further limit the pathogenic effects of leukocytes in cardiac surgery.