Clinical evaluation of a new fat removal filter during cardiac surgery.

OBJECTIVES: Fat microemboli are generated during cardiac surgery that are associated with post-operative organ injury. Recently, a fat removal filter has been developed, based on a polyester leukocyte depletion filter. However, the efficacy of such a filter in a clinical setting is unknown. In this study we tested the efficacy of this filter. METHODS: Coronary artery bypass patients were randomly divided into two groups. Group I: filtration of cardiotomy suction blood during cardiopulmonary bypass with a fat removal filter (n=14). Group II: control patients without filtration (n=14). Filter efficacy was evaluated in group I using biochemical assays and thin layer chromatography of blood samples taken simultaneously before and after the filter. In addition, clinical and biochemical markers for organ injury were determined in both groups. RESULTS: The fat filter removed triglycerides (0.9+/-0.08 vs. 0.63+/-0.08 mmol l(-1), P=0.004, paired t-test), leukocytes (4.3+/-0.8 x 10(9) vs. 2.3+/-0.6 x 10(9)l(-1), P=0.03), and platelets (116+/-26 x 10(9) vs. 75+/-21 x 10(9)l(-1), P=0.003) from the blood samples taken before and after the filter. Chromatography showed a significant reduction in free fatty acids, phospholipids and triglycerides. Clinically, leukocyte counts were similar, but platelet counts were higher (181+/-14 x 10(9) vs. 117+/-8.6 x 10(9)l(-1) control, P<0.001) in group I on the first postoperative day. CONCLUSIONS: The fat filter removed 40% fat, leukocytes and platelets from cardiotomy suction blood during cardiac surgery. A larger scale study is necessary to determine clinical effects on organ damage.

Leucocyte depletion during cardiac surgery: a comparison of different filtration strategies.

The results of leucocyte filtration during cardiac surgery are conflicting. This may be due to timing and duration of the filtration procedure, and to flow and pressure conditions in the filter. Therefore, we prospectively compared three major leucocyte filtration strategies in cardiac surgical patients. Forty patients were randomly divided into four groups. Group I: leucofiltration of arterial blood throughout cardiopulmonary bypass (CPB) (associated with high-flow and pressure gradients), Group II: leucofiltration of a part of the venous return blood in the rewarming phase during CPB (associated with intermediate flow, but high pressure), Group III: leucofiltration of residual heart-lung machine blood during transfusion into the patient after CPB (associated with low flow and low pressure), Group IV: control group without leucofiltration. We measured circulating leucocyte counts, plasma elastase levels and arterial blood oxygenation. Filters were postoperatively examined using scanning electronmicroscopy (SEM). Leucocyte counts increased over time and oxygenation decreased in all groups, without significant differences between the groups. SEM demonstrated extensive protein deposits and damaged leucocytes in the deeper layers of the filters from Group I. This was not observed in the filters from Group III. The postoperative plasma elastase levels increased in Groups II and IV and decreased in Groups I and III. In conclusion, we could not demonstrate a clinical difference among the three leucocyte depletion strategies. However, our laboratory results suggest that leucocyte filtration at low flow and pressure conditions is associated with less leucocyte damage and less release of elastase.

Normalization of aortic function during arousal episodes in the hibernating ground squirrel.

Hypothermia is commonly used to restrict organ damage during preservation of tissue, but does not offer complete protection. Organ damage after reperfusion/rewarming is amongst others caused by an impairment of vascular properties, particularly endothelium-dependent vasodilatation. We hypothesized that hibernating small animals, which frequently cycle through periods of deep cooling (torpor) and full rewarming (arousal), employ specific mechanisms to preserve vascular function after cooling and reperfusion. Therefore we measured contraction of aortic tissue of hibernating European ground squirrels after 24 h and 7 days of torpor, arousal (1.5 h) and in non-hibernating animals. To assess the role of nitric oxide (NO), experiments were performed in the absence and presence of the NO-synthesis inhibitor, L-NMMA (10(-4) M). Maximum contraction to phenylephrine and angiotensin II was doubled in 7-days torpid animals without a shift in EC50, compared to the other 3 groups. Maximum contraction to KCl was doubled in 7-days torpid animals compared to the arousal group and non-hibernating animals. Relaxation to acetylcholine (ACh) and sodium nitrite in phenylephrine precontracted rings did not differ between groups. In the presence of L-NMMA, the maximum of concentration-response curves for all three vasoconstrictors was increased by about 30% in the arousal group, but unaffected in other groups. L-NMMA completely inhibited ACh-induced relaxation in 24-h torpid animals and non-hibernating animals, but only partially in 7-days torpid animals and in the arousal group. From this we conclude that vascular adaptation proceeds during torpor. Further, increased contractility of aortic tissue during long torpor returns to normal within 1.5 hours of arousal, which is associated with an increased basal NO synthesis. In addition, involvement of NO in agonist-mediated relaxation differs between the various stages of hibernation.Thus, hibernating animals have effectively developed mechanisms to preserve vascular function after cooling and rewarming.

To ventilate or not after minimally invasive direct coronary artery bypass surgery: the role of epidural anesthesia.

OBJECTIVE: To evaluate the effect of immediate postoperative extubation and postoperative ventilation after minimally invasive direct coronary artery bypass (MIDCAB) surgery and to assess the role of epidural anesthesia. DESIGN: Randomized prospective study. SETTING: University hospital, single institution. PARTICIPANTS: Patients (n = 90) scheduled for elective MIDCAB surgery. INTERVENTIONS: Patients were divided into 3 groups: 30 patients had general anesthesia and were extubated immediately after surgery (extubated group), 30 patients had a thoracic epidural and general anesthesia and were extubated immediately after surgery (epidural group), and 30 patients had general anesthesia and were ventilated after surgery (intubated group). MEASUREMENTS AND MAIN RESULTS: With a similar cardiac index and less vasoactive medication, mean arterial blood pressure (77 plus minus 8 mmHg [mean plus minus SD]) and heart rate (76 plus minus 10 beats/min) in the epidural group were lower on the first postoperative day than in the intubated group (83 plus minus 10 mmHg and 81 plus minus 13 beats/min) and the extubated group (86 plus minus 10 mmHg and 83 plus minus 13) (p = 0.01 and p = 0.09). Oxygenation on the first postoperative day was better in the epidural group than in the intubated group (14.8 plus minus 3.8 kPa v 12.6 plus minus 3.2 kPa; p = 0.05). The epidural group and the extubated group had a transient respiratory acidosis postoperatively. Pain score in the epidural group was lower on the first postoperative day than in the extubated group with general anesthesia (3.0 plus minus 1.6 visual analog scale v 4.6 plus minus 1.8 visual analog scale; p = 0.01). Hospital stay was shorter in the epidural group than in the ventilated group (5.9 plus minus 2.4 days v 8.1 plus minus 5.3 days; p = 0.05) CONCLUSION: Immediate postoperative extubation in patients with thoracic epidural anesthesia and supplemental general anesthesia provides the most favorable clinical circumstances after MIDCAB surgery.