Influence of temperature on neutrophil trafficking during clinical cardiopulmonary bypass

Aggressive re-warming at 38.5 °C following deep hypothermia at 21 °C increases neutrophil membrane bound elastase activity and pro-inflammatory factor release

Background

Cardiopulmonary bypass (CPB) is often performed under hypothermic condition. The effects of hypothermia and re-warming on neutrophil activity are unclear. This study aimed to compare the effects of different hypothermia and re-warming regimens on neutrophil membrane bound elastase (MBE) activity and the release of pro-inflammatory factors from neutrophils.

Methods

Human neutrophils were exposed to different hypothermia and re-warming regimens. MBE activity and the release of interleukin (IL)-β1, IL-6, IL-8, and tumor necrosis factor (TNF)-α were measured.

Results

Neutrophil MBE activity was significantly reduced after 60-min moderate (28 °C) or deep (21 °C) hypothermic treatment. Compared with normothermic (37 °C) re-warming, aggressive re-warming (38.5°) for 120 min following deep hypothermia (21 °C) dramatically increased neutrophil MBE activity (P < 0.05). Co-incubation of neutrophils with platelet-rich plasma further increased MBE activity significantly under all the tested temperature regimens. IL-β1 release from neutrophils was significantly higher after deep hypothermia (21 °C) followed by normothermic (37 °C) re-warming than after moderate hypothermia (28 °C) followed by normothermic re-warming (P < 0.05). Aggressive re-warming (38.5°) following deep hypothermia significantly increased the release of IL-β1, IL-8, and TNF-α from neutrophil compared with moderate re-warming (37 °C) (all P < 0.05).

Conclusion

Aggressive re-warming following deep hypothermia may contribute to CPB-associated tissue injury by increasing neutrophil MBE activity and stimulating pro-inflammatory factor release, thus, should be avoided. The optimal hypothermic temperature of CPB should be determined based on patient clinical characteristics and surgery type.

Lung inflammatory response syndrome after cardiac-operations and treatment of lornoxicam

The majority of patients survive after extracorporeal circulation without any clinically apparent deleterious effects. However, disturbances exist in various degrees sometimes, which indicate the harmful effects of cardiopulmonary bypass (CPB) in the body. Several factors during extracorporeal circulation either mechanical dependent (exposure of blood to non-biological area) or mechanical independent (surgical wounds, ischemia and reperfusion, alteration in body temperature, release of endotoxins) have been shown to trigger the inflammatory reaction of the body. The complement activation, the release of cytokines, the leukocyte activation and accumulation as well as the production of several "mediators" such as oxygen free radicals, metabolites of arachidonic acid, platelet activating factors (PAF), nitric acid, and endothelin. The investigation continues today on the three metabolites of lornoxicam (the hydroxylated metabolite and two other metabolites of unknown chemical composition) to search for potential new pharmacological properties and activities.

Naturally occurring hypothermia is more advantageous than fever in severe forms of lipopolysaccharide- and Escherichia coli-induced systemic inflammation

The natural switch from fever to hypothermia observed in the most severe cases of systemic inflammation is a phenomenon that continues to puzzle clinicians and scientists. The present study was the first to evaluate in direct experiments how the development of hypothermia vs. fever during severe forms of systemic inflammation impacts the pathophysiology of this malady and mortality rates in rats. Following administration of bacterial lipopolysaccharide (LPS; 5 or 18 mg/kg) or of a clinical Escherichia coli isolate (5 × 10(9) or 1 × 10(10) CFU/kg), hypothermia developed in rats exposed to a mildly cool environment, but not in rats exposed to a warm environment; only fever was revealed in the warm environment. Development of hypothermia instead of fever suppressed endotoxemia in E. coli-infected rats, but not in LPS-injected rats. The infiltration of the lungs by neutrophils was similarly suppressed in E. coli-infected rats of the hypothermic group. These potentially beneficial effects came with costs, as hypothermia increased bacterial burden in the liver. Furthermore, the hypotensive responses to LPS or E. coli were exaggerated in rats of the hypothermic group. This exaggeration, however, occurred independently of changes in inflammatory cytokines and prostaglandins. Despite possible costs, development of hypothermia lessened abdominal organ dysfunction and reduced overall mortality rates in both the E. coli and LPS models. By demonstrating that naturally occurring hypothermia is more advantageous than fever in severe forms of aseptic (LPS-induced) or septic (E. coli-induced) systemic inflammation, this study provides new grounds for the management of this deadly condition.

Facts and fiction: the impact of hypothermia on molecular mechanisms following major challenge

Numerous multiple trauma and surgical patients suffer from accidental hypothermia. While induced hypothermia is commonly used in elective cardiac surgery due to its protective effects, accidental hypothermia is associated with increased posttraumatic complications and even mortality in severely injured patients. This paper focuses on protective molecular mechanisms of hypothermia on apoptosis and the posttraumatic immune response. Although information regarding severe trauma is limited, there is evidence that induced hypothermia may have beneficial effects on the posttraumatic immune response as well as apoptosis in animal studies and certain clinical situations. However, more profound knowledge of mechanisms is necessary before randomized clinical trials in trauma patients can be initiated.

Neonatal ECMO Study of Temperature (NEST)--a randomised controlled trial

BACKGROUND

Existing evidence indicates that once mature neonates with severe cardio-respiratory failure become eligible for Extra Corporeal Membrane Oxygenation (ECMO) their chances of intact survival are doubled if they actually receive ECMO. However, significant numbers survive with disability. NEST is a multi-centre randomised controlled trial designed to test whether, in neonates requiring ECMO, cooling to 34 degrees C for the first 48 to 72 hours of their ECMO course leads to improved later health status. Infants allocated to the control group will receive ECMO at 37 degrees C throughout their course, which is currently standard practice around the world. Health status of both groups will be assessed formally at 2 years corrected age.

METHODS/DESIGN

All infants recruited to the study will be cared for in one of the four United Kingdom (UK) ECMO centres. Babies who are thought to be eligible will be assessed by the treating clinician who will confirm eligibility, ensure that consent has been obtained and then randomise the baby using a web based system, based at the National Perinatal Epidemiology Unit (NPEU) Clinical Trials Unit. Trial registration.Babies allocated ECMO without cooling will receive ECMO at 37 degrees C +/- 0.2 degrees C. Babies allocated ECMO with cooling will be managed at 34 degrees C +/- 0.2 degrees C for up to 72 hours from the start of their ECMO run. The minimum duration of cooling will be 48 hours. Rewarming (to 37 degrees C) will occur at a rate of no more than 0.5 degrees C per hour. All other aspects of ECMO management will be identical.

PRIMARY OUTCOME

Cognitive score from the Bayley Scales of Infant and Toddler Development, 3rd edition (Bayley-III) at age of 2 years (24 - 27 months).

DISCUSSION

For the primary analysis, children will be analysed in the groups to which they are assigned, comparing the outcome of all babies allocated to "ECMO with cooling" with all those allocated to "ECMO" alone, regardless of deviation from the protocol or treatment received. For the primary outcome the analysis will compare the mean scores for each group of surviving babies. The rationale for this choice of primary analysis is to give a fair representation of the average ability of assessable children, accepting the limitation that excluding deaths might impose.The consistency of the effect of cooling on the group of babies recruited to the trial will be explored to see whether cooling is of particular help, or not, to specific subgroups of infants, using the statistical test of interaction. Therefore pre-specified subgroup analyses include: (i) whether the ECMO is veno-arterial or veno-venous; (ii) whether the child's oxygenation index at the time of recruitment is <60 or > or = 60; (iii) initial aEEG pattern shown on the cerebral function monitor, and (iv) primary diagnostic group.

TRIAL REGISTRATION

Current Controlled Trials ISRCTN72635512.

Specific p38 inhibition in stimulated endothelial cells: a possible new anti-inflammatory strategy after hypothermia and rewarming

To protect immature organ systems during corrective cardiac surgery, patients are cooled to a minimal temperature of 17 degrees C during cardiopulmonary bypass (CPB). However hypothermic CPB triggers the whole body inflammatory response and results in unwanted prolonged inflammation. The present study was designed to clarify the hypothermia and rewarming induced mechanisms and examine interventional pharmacological strategies that could prevent prolonged inflammation. Stimulated primary human umbilical vein endothelial cells (HUVECs) were exposed to a dynamic temperature protocol analogous to clinical settings. Furthermore endothelial cells were pretreated with methylprednisolone and/or tacrolimus as well as with MAPK inhibitors (SB203580, U0126 and SP600125). Cell viability, expression of IL-6 and ERK 1/2, p38 and SAPK/JNK were investigated. Stimulated endothelial cells secreted significantly higher IL-6 protein 2h after rewarming in comparison to normothermic control cells. Moreover, dynamic temperature changes lead to increased MAPK phosphorylation. Only the combined pre-treatment with MP and TAC served to inhibit the IL-6 secretion. As intracellular signalling pathway we could demonstrate that SB203580 as specific p38 inhibitor most effectively down regulated the unwanted IL-6 release after cooling and rewarming. Therefore inhibition of p38 or components of the p38 pathway could be a promising and selective antiinflammatory therapeutic target after hypothermic CPB.

Effect of temperature on tether extraction, surface protrusion, and cortical tension of human neutrophils

Neutrophil rolling on endothelial cells, the initial stage of its migrational journey to a site of inflammation, is facilitated by tether extraction and surface protrusion. Both phenomena have been studied extensively at room temperature, which is considerably lower than human body temperature. It is known that temperature greatly affects cellular mechanical properties such as viscosity. Therefore, we carried out tether extraction, surface protrusion, and cortical tension experiments at 37 degrees C with the micropipette aspiration technique. The experimental temperature was elevated using a custom-designed microscope chamber for the micropipette aspiration technique. To evaluate the constant temperature assumption in our experiments, the temperature distribution in the whole chamber was computed with finite element simulation. Our simulation results showed that temperature variation around the location where our experiments were performed was less than 0.2 degrees C. For tether extraction at 37 degrees C, the threshold force required to pull a tether (40 pN) was not statistically different from the value at room temperature (51 pN), whereas the effective viscosity (0.75 pN.s/microm) decreased significantly from the value at room temperature (1.5 pN.s/microm). Surface protrusion, which was modeled as a linear deformation, had a slightly smaller spring constant at 37 degrees C (40 pN/microm) than it did at room temperature (56 pN/microm). However, the cortical tension at 37 degrees C (5.7+/-2.2 pN/microm) was substantially smaller than that at room temperature (23+/-8 pN/microm). These data clearly suggest that neutrophils roll differently at body temperature than they do at room temperature by having distinct mechanical responses to shear stress of blood flow.

Effect of Blood Temperature on the Efficacy of Systemic Leucodepletion during Cardiopulmonary Bypass: A Prospective Randomized Clinical Study

The authors examined the effect of blood temperature within the cardiopulmonary bypass (CPB) circuit on the efficacy of an arterial line filter. Eighty patients undergoing elective, primary coronary artery bypass grafting under CPB were prospectively randomized in two equal groups. Blood temperature was kept at 35 degrees C in the first group and reduced to 28 degrees C in the second group. Twenty patients in each group had an arterial line LG6 filter attached onto CPB circuit. The other 20 patients in each group (controls) had a non-leukocyte-depleting filter. Blood samples (10 ml) were taken before CPB, at 5 minutes on CPB, at 30 minutes on CPB, 5 minutes after aortic clamp removal, and 6 hours postoperatively. Leucocytes were counted under light microscopy. Activated leucocytes were identified using nitroblue tetrazolium staining. Patients undergoing leucodepletion had significantly lower total and activated leukocyte counts than control patients in both groups (p < 0.05). Patients having a leukocyte-depleting filter at a CPB temperature of 35 degrees C had significantly lower total leukocyte counts (p < 0.05) than those having a leukocyte-depleting filter at a CPB temperature of 28 degrees C (p < 0.05). However, there were not statistically significant differences in the activated leukocyte counts between the two leucodepleted groups (p > 0.05). This study shows that warm blood temperature within the CPB circuit has a positive effect on the overall leucodepleting efficacy of the LG6 filter. Activated leucocytes, however, seem to be depleted at similar rates irrespective of the blood temperature in the CPB circuit.

Thermo-wrap technology preserves normothermia better than routine thermal care in patients undergoing off-pump coronary artery bypass and is associated with lower immune response and lesser myocardial damage

OBJECTIVE

Perioperative hypothermia might be detrimental to the patient undergoing off-pump coronary artery bypass surgery. We assessed the efficacy of the Allon thermoregulation system (MTRE Advanced Technologies Ltd, Or-Akiva, Israel) compared with that of routine thermal care in maintaining normothermia during and after off-pump coronary artery bypass surgery.

METHODS

Patients undergoing off-pump coronary artery bypass surgery were perioperatively and randomly warmed with the 2 techniques (n = 45 per group). Core temperature, hemodynamics, and troponin I, interleukin 6, interleukin 8, and interleukin 10 blood levels were assessed.

RESULTS

The mean temperature of the patients in the Allon thermoregulation system group (AT group) was significantly ( P < .005) higher than that of the patients receiving routine thermal care (the RTC group); less than 40% of the latter reached 36 degrees C compared with 100% of the former. The cardiac index was higher and the systemic vascular resistance was lower ( P < .05) by 16% and 25%, respectively, in the individuals in the AT group compared with in the individuals in the RTC group during the 4 postoperative hours. End-of-surgery interleukin 6 levels and 24-hour postoperative troponin I levels were significantly ( P < .01) lower in the patients in the AT group than in the RTC group. The RTC group's troponin levels closely correlated with their interleukin 6 levels at the end of the operation ( R = 0.51, P = .002).

CONCLUSIONS

Unlike routine thermal care, the Allon thermoregulation system maintains core normothermia in more than 80% of patients undergoing off-pump coronary artery bypass surgery. Normothermia is associated with better cardiac and vascular conditions, a lower cardiac injury rate, and a lower inflammatory response. The close correlation between the increased interleukin 6 and troponin I levels in the routine thermal care group indicates a potential deleterious effect of lowered temperature on the patient's outcome.

Mild hypothermia for acute liver failure: a review of mechanisms of action

Brain edema with intracranial hypertension is a major complication in patients with acute liver failure. Current therapies for this complication include a variety of pharmacologic and interventional measures, some of which are frequently associated with adverse effects or contraindications. Even though these measures usually allow the control of intracranial hypertension for a certain period of time, recurrence is common. New therapies are therefore needed. Increasing clinical and experimental evidence suggests that induction of mild hypothermia (32 degrees C-35 degrees C) may be a therapeutic alternative. Similar to traumatic brain injury or brain stroke, induction of mild hypothermia seems highly effective to reduce intracranial pressure in patients with acute liver failure. Several mechanisms by which mild hypothermia may prevent brain edema and intracranial hypertension in this condition have been disclosed and may include beneficial effects on ammonia metabolism, as well as on the disturbances of brain osmolarity, cerebrovascular hemodynamics, brain glucose metabolism, inflammation, and others. Improvement of systemic hemodynamics and amelioration of liver injury may be other benefits of the systemic induction of mild hypothermia, but the impact of potential adverse events, such as infection, should also be taken into account. At a time when mild hypothermia is increasingly used in several specialized centers, performance of a randomized controlled trial seems critical to confirm the benefits of mild hypothermia in acute liver failure and to provide adequate guidelines for its use.

Changes in mesenteric vascular reactivity and inflammatory response after cardiopulmonary bypass in a rat model

BACKGROUND

Mesenteric ischemia and acidosis leading to intestinal ischemia has been observed during cardiopulmonary bypass (CPB) despite normal flow in the mesenteric vessels. The aim of this study was to assess mesenteric endothelium-dependent reactivity and vasoconstrictor responses of small mesenteric arteries in a rat model of CPB without aortic cross-clamping.

METHODS

After femoral cannulation a partial 90 minutes CPB was performed with hemodynamics and blood gas parameters monitoring. Blood samples and segments of small mesenteric arteries were obtained in rats sacrificed 2.5 hours (CPBH2.5) or 6 hours (CPBH6) after femoral cannulation. Sham surgery (sham H2.5, sham H6) was performed with femoral cannulation only. Segments of small mesenteric arteries were placed in a myograph in order to assess the contractile response to phenylephrine (with or without NO synthase inhibitor) or the endothelium-dependent relaxation to acetylcholine. Systemic inflammation was evaluated by measuring plasma concentrations of TNFalpha. Pulmonary and intestinal infiltration of activated leukocytes was assessed by immunohistochemistry.

RESULTS

CPB induced increased contractile response to phenylephrine which persisted after blockade of NO synthesis as well as transient impairment of endothelium-dependent relaxations. CPB also led to early and marked release of TNFalpha.

CONCLUSIONS

CPB was responsible for mesenteric endothelial dysfunction and direct increase in the contractile response to alpha1-adrenergic agonist with increased systemic inflammatory response. This phenomenon might contribute to an increase in the risk of mesenteric ischemic events during cardiac surgery especially when vasopressor agents are used.

Regional oxygenation and systemic inflammatory response during cardiopulmonary bypass: influence of temperature and blood flow variations

OBJECTIVE

To evaluate the role of target temperature (28 degrees or 34 degrees C) in cardiac surgery on regional oxygenation during hypothermia and rewarming and systemic inflammatory response.

DESIGN

Prospective, controlled, and randomized clinical study.

SETTING

University hospital.

PARTICIPANTS

Elderly patients (mean age 70 +/- 2 years) with acquired heart disease with an anticipated bypass time exceeding 120 minutes (n = 30).

INTERVENTIONS

The patients were cooled to either 28 degrees C (n = 15) or 34 degrees C (n = 15). At hypothermia, bypass blood flow was reduced twice from full flow (2.4 L/min/m(2) body surface area [BSA]) to 2.0 L/min/m(2).

MEASUREMENTS AND MAIN RESULTS

Hepatic and jugular venous oxygen tension and saturation were higher at 28 degrees C than at 34 degrees C. In comparison with the preoperative values, at 28 degrees C hepatic venous values were higher; whereas at 34 degrees C, they were lower. The reduction of pump blood flow during hypothermia, from 2.4 to 2.0 L/min/m(2)was accompanied by reductions of central, jugular, and hepatic oxygenation at both target temperatures. During rewarming, central and regional venous oxygenation decreased irrespective of the preceding temperature. The decrease was most pronounced in hepatic venous blood, with the lowest individual values <10%. Serum concentrations of C3a and IL-6 increased during hypothermia and increased further during rewarming irrespective of the preceding temperature.

CONCLUSION

During cardiopulmonary bypass, hypothermia at 28 degrees C increases regional and central venous oxygenation better than at 34 degrees C. In contrast, venous oxygenation decreases during rewarming irrespective of the preceding temperature. No significant difference in the systemic inflammatory response associated with target temperature was detected.

Outcome after simultaneous abdominal aortic aneurysm repair and aortocoronary bypass

Myocardial infarction remains the leading cause of early and late death after abdominal aortic aneurysm (AAA) repair. Myocardial revascularization is staged either before or concomitant with AAA resection, but results are far from uniform. We retrospectively analyzed our experience with patients who underwent concomitant AAA resection and aortocoronary bypass (ACB) to examine the factors affecting early morbidity/mortality and early results. Forty-two patients (all men; mean age, 67.2 years) underwent simultaneous ACB grafting and AAA repair between 1975 and 1998. All were managed postoperatively in the cardiothoracic intensive care unit (mean stay, 6.1 days). The mean total hospital stay was 17.2 days. Two died in the early postoperative period (4.8%): 1 of sustained myocardial failure following a third ACB, and 1 of coagulopathy after concomitant ACB, aortic valve replacement, and AAA. One patient developed a nonfatal MI on postoperative day 3. The incidence of wound and bleeding complications was higher for patients undergoing both ACB and AAA repair than for patients undergoing AAA resection alone. On follow-up (mean, 10 years; range, 7 months to 15 years), only 2 of 10 late deaths were due to cardiovascular causes. We believe that concomitant myocardial revascularization is warranted in select patients requiring elective or urgent AAA resection in order to decrease perioperative risk and improve late survival. Cardiac failure or ischemia during aortic surgery can be prevented by proper perfusion with or without cardiopulmonary bypass. In patients undergoing simultaneous procedures, the increased risk is related to the severity of the vascular and coronary artery disease and not to the combined operations.

The systemic factor: the comparative roles of cardiopulmonary bypass and off-pump surgery in the genesis of patient injury during and following cardiac surgery

There is compelling evidence that off-pump coronary artery bypass operations are associated with reduced circulating levels of inflammatory mediators. Whereas complement activation and release of acute-phase reactants such as interleukin-6 are still expected to occur as consequences of a nonbypass-related general surgical trauma, a major feature of off-pump surgery seems to be a decreased production of interleukin-8, which may have important practical implications because of the participation of this cytokine in neutrophil trafficking and myocardial injury. The scarcity of carefully controlled, randomized trials precludes firm conclusions regarding the extent to which these biological changes translate into meaningful improvements in clinical outcomes. The problem is further complicated by the fact that the adverse effects of cardiopulmonary bypass largely depend on a genetically controlled balance between proinflammatory and antiinflammatory mediators. Currently, it is still impossible to predict, in a given patient, the side toward which this balance will be shifted. Nevertheless, accumulating experience identifies patient subgroups who may greatly benefit from avoiding extracorporeal circulation. These subsets include patients with severe extracardiac comorbidities (in particular, renal failure) and, possibly, patients with advanced left ventricular dysfunction, who may poorly tolerate superimposed, bypass-related, inflammatory tissue injuries.

Hypothermia induces T-cell production of immunosuppressive cytokines

BACKGROUND

Hypothermia is associated with increased postoperative infectious complications. We hypothesized that hypothermia suppresses the inflammatory response by altering T-cell cytokine production from a proinflammatory to an antiinflammatory profile, thus explaining the increased susceptibility to infectious complications associated with perioperative hypothermia.

METHODS

Forty rats were randomized to either a Hypothermia (30 degrees C) or Control (38 degrees C) group. Blood samples taken at baseline and after 8 h of thermoregulation were stimulated with phorbol 12-myristate 13-acetate and ionomycin. Interleukin (IL)-2 receptor expression and intracellular IL-10 production were measured using monoclonal antibodies and flow cytometry in CD4 and CD8 T cells. Differences in IL-10 production and IL-2 receptor expression for stimulated samples in the Hypothermia and Control groups were compared.

RESULTS

Stimulated CD4 cells demonstrated an antiinflammatory cytokine expression profile after hypothermia. Intracellular IL-10 production increased in the Hypothermia group but remained the same in the Control group (% change = 40 [3,87] and 2 [-36,26], respectively; P = 0.043). The increase in IL-2 receptor expression observed in the control group was suppressed after hypothermia (% change = 12[8,30] and 1 [-3,13], respectively; P = 0.026). We observed a greater increase in IL-10 production by CD8 cells from hypothermic animals than in those from control animals (% change = 41 [-8,90] and -4 [-40,5], respectively; P = 0.019). CD8 IL-2 receptor expression in hypothermic animals was similar to that of control animals (% change = 23 [-7,37] vs 25 [2,80], respectively; P = 0.32).

CONCLUSIONS

Hypothermia induced an antiinflammatory T-cell cytokine profile.

Inflammation After Cardiopulmonary Bypass: Therapy for the Postpump Syndrome

Cardiopulmonary bypass (CPB) is used in most, but not all, complex heart operations. CPB is associated with a systemic inflammatory response in adults and children. Many materials-dependent (exposure of blood to non- physiologic surfaces and conditions) and materials-in dependent (surgical trauma, ischemia-perfusion to the organs, changes in body temperature, and release of endotoxin) factors during CPB have been implicated in the etiology of this complex response. The mechanisms involved may include complement activation, release of cytokines, leukocyte activation with expression of ad hesion molecules, and production of various vasoactive and immunoactive substances. Postpump inflamma tion may lead to postoperative complications and may result in respiratory failure, renal dysfunction, bleeding disorders, neurologic dysfunction, altered liver func tion, and ultimately multiple organ failure. Significant efforts are being made to decrease the generation and effects of postpump inflammation. Interventions to this end have included avoiding CPB when possible, im proving the biocompatibility of the involved mechani cal devices, and administering medications that main tain cellular integrity. This article provides an overview of the etiology, pathophysiology, and treatment of postpump inflammation. Perhaps with additional in sight into this syndrome, CPB can be made a safer and more efficacious modality of cardiorespiratory support. Copyright© 2001 by W.B. Saunders Company.

Hypothermia attenuates beta1 integrin expression on extravasated neutrophils in an animal model of meningitis

Brain injury in meningitis occurs in part as a consequence of leukocyte migration and activation. Leukocyte integrins are pivotal in the inflammatory response by mediating adhesion to vascular endothelium and extracellular matrix proteins. We have demonstrated that moderate hypothermia early in the course of meningitis decreases leukocyte sequestration within the brain parenchyma. This study examines whether hypothermia alters neutrophil integrin expression in a rabbit model of bacterial meningitis. Prior to the induction of meningitis, peripheral blood samples were obtained and the neutrophils isolated. Sixteen hours after inducing group B streptococcal meningitis, animals were treated with antibiotics, i.v. fluids, and mechanically ventilated. Animals were randomized to hypothermia (32-33 degrees C) or normothermia conditions. After 10 hours of hypothermia or normothermia, neutrophils were isolated from the blood and cerebral spinal fluid (CSF), stained for beta1 and beta2 integrins, and analyzed using flow cytometry. Cerebral spinal fluid neutrophil beta1 integrin expression was significantly decreased in hypothermic animals. Beta-1 integrins can assume a higher affinity or "activated" state following inflammatory stimulation. Expression of "activated" beta1 integrins was also significantly decreased in hypothermic animals. Beta2 CSF neutrophil integrin expression was decreased in hypothermic animals, but failed to reach significance. These data suggest hypothermia may attenuate extravasated leukocyte expression of both total and "activated" beta1 integrins.

Can statins reduce the inflammatory response to cardiopulmonary bypass? A clinical study

OBJECTIVE

In addition to lowering lipid levels, statins might reduce leukocyte-endothelial cell interactions. Therefore, we assessed whether this effect could limit the inflammatory response to cardiopulmonary bypass (CPB) in cardiac surgical patients.

METHODS

Twenty patients undergoing valve or coronary operations with tepid (34 degrees C) CPB were randomized to receive an oral dose of atorvastatin (40 mg the evening before and 40 mg the morning of surgery) or to serve as controls. Pre- and post-CPB blood samples were assayed for neutrophil CD11b surface adhesion molecule and oxidative burst. Plasma levels of interleukins 6 and 8, P-selectin, soluble intercellular adhesion molecule-1, and lactoferrin were measured by enzyme-linked immunosorbent assay (ELISA). In addition, right atrial biopsies were taken before and at the end of CPB, and processed for the expression of the transcription nuclear factor-kappa B (NF-kappaB).

RESULTS

The two groups did not differ with regard to pre- and intraoperative data. Except for P-selectin, postbypass values of all markers significantly increased over baseline values, but atorvastatin therapy failed to attenuate the magnitude of this increase. In the two groups, the expression of NF-kappaB significantly (p = 0.004) increased over baseline without group effect. Postoperative clinical outcomes did not differ either between the two groups.

CONCLUSION

These data show that acute preoperative statin therapy fails to limit the inflammatory response to CPB; however, the data also document a major upregulation of NF-kappaB during cardiac operations, thereby providing a sound rationale for interventions targeted at inactivating this key component of the inflammatory cascade.

Soluble P-selectin and the postoperative course following cardiopulmonary bypass in children

BACKGROUND

Cytokine-inducible leucocyte-endothelial adhesion molecules were shown to affect the postoperative inflammatory response following cardiopulmonary bypass (CPB). Soluble P-selectin (sP-selectin) is one of these molecules. We investigated the correlation between plasma sP-selectin levels and the intra- and postoperative course in children undergoing CPB.

METHODS

Serial blood samples of 13 patients were collected preoperatively upon initiation of CPB and seven times postoperatively. Plasma was recovered immediately and frozen at - 70 degrees C until use. Circulating soluble selectin molecules were measured with a sandwich enzyme-linked immunoabsorbent assay technique.

RESULTS

The significant post-CPB changes in sP-selectins plasma levels were associated with patient characteristics, operative variables and postoperative course. sP-selectin levels correlated significantly with surgery time, aortic cross-clamping time and inotropic support, as well as with the postoperative Pediatric Risk of Mortality score, hypotension and tachycardia.

CONCLUSIONS

A relation between CPB-induced mediators and both early and late clinical effects is suggested. The up-regulation and expression of sP-selectin indicate neutrophil activation as a possible mechanism for the increase, and inhibiting it may reduce the inflammatory response associated with CPB.

Plasma-soluble E-selectin after cardiopulmonary bypass in children: is it a marker of the postoperative course?

OBJECTIVE

To investigate the relationship and possible role of soluble adhesion molecule E-selectin in the postoperative course in children undergoing cardiopulmonary bypass (CPB).

DESIGN

Prospective cohort study.

SETTING

Pediatric intensive care unit of a university hospital.

PARTICIPANTS

Thirteen children who were candidates for cardiac surgery.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Serial blood samples of 13 CPB patients were collected from the arterial catheter or from the bypass circuits preoperatively; on initiation of CPB; on termination of CPB; and 1, 2, 4, 8, 12, 18, 24, and 48 hours postoperatively. Plasma was recovered immediately, aliquoted, and frozen at -70 degrees C until use. Circulating soluble selectin molecules were measured with a sandwich enzyme-linked immunosorbent assay technique. There were significant changes in plasma levels of soluble E-selectins in patients after CPB, and these levels were associated with patient characteristics, operative variables, and postoperative course. Soluble E-selectin correlated significantly with inotropic support and the use of anti-inflammatory drugs. There was a significant association between the development of postoperative sepsis and soluble E-selectin levels. No correlation was found between soluble E-selectins and duration of CPB, aortic cross-clamping, or hemodynamic variables, including heart rate and mean systemic arterial pressure.

CONCLUSION

These results suggest a relationship between CPB-induced mediators and early and late clinical effects. Although the mechanism for the increase of soluble E-selectin remains to be elucidated, the upregulation of soluble E-selectin indicates neutrophil activation, and its inhibition may represent a target for reducing the inflammatory response associated with CPB.

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

OBJECTIVE

To prevent postoperative pulmonary dysfunction, we have investigated the effect of the Leuko-Guard 6 leukocyte-reducing arterial line filter (LG6) on postoperative lung function.

METHODS

Twenty-six cases of adult valvular heart disease were included in this study. Thirteen cases were operated upon using the LG6 (Group LG), and 13 cases were operated upon using a conventional arterial line filter (Group C). Neutrophil, polymorphonuclear leukocyte elastase and lipoperoxide were measured for this study, and the lung function was evaluated using the Oxygenation Index (PaO2/FiO2).

RESULTS

Statistically significant differences were observed in neutrophil counts between Group LG and Group C (LG = 2225 +/- 572/mm3, C = 3157 +/- 1413/mm3, p = 0.04) at 5 minutes after the onset of cardiopulmonary bypass. In simultaneous blood sampling from the pulmonary artery and the pulmonary vein, the sequestration of neutrophil in the lung decreased in Group LG after the discontinuation of cardiopulmonary bypass. Release of polymorphonuclear leukocyte elastase from the lungs was significantly decreased (p = 0.04) in the Group LG at 1 hour post-bypass. Significant differences were observed in the Oxygenation Index between Group LG and Group C (LG = 398 +/- 72, C = 326 +/- 71, p = 0.019) at 3 hours post-bypass.

CONCLUSION

We concluded that LG6 improved the postoperative lung function, and its mechanism might be derived from the prevention of leukosequestration in the lungs that occurs during the rewarming phase due to selective absorption of activated leukocyte by the LG6.

The effects of cardiopulmonary bypass temperature on inflammatory response following cardiopulmonary bypass

OBJECTIVES

The inflammatory response to cardiopulmonary bypass is believed to play an important role in end organ dysfunction after open heart surgery and may be more profound after normothermic systemic perfusion. The aim of the present study was to investigate the effects of cardiopulmonary bypass temperature on the production of markers of inflammatory activity after coronary artery surgery.

METHODS

Forty-five low risk patients undergoing elective coronary artery surgery were prospectively randomized into three groups: hypothermia (28 degrees C, n = 15), moderate hypothermia (32 degrees C, n = 15), and normothermia (37 degrees C, n = 15). All patients received cold antegrade crystalloid cardioplegia and topical myocardial cooling with saline at 4 degrees C. Serum samples were collected for the estimation of neutrophil elastase, interleukin 8, C3d, and IgG under ice preoperatively, 5 min after heparinisation, 30 min following start of CPB, at the end of CPB, 5 min after protamine administration, and 4, 12 and 24 h postoperatively.

RESULTS

Patients were similar with regard to preoperative and intraoperative characteristics (age, sex, severity of symptoms, number of grafts performed, aortic cross clamp time, cardiopulmonary bypass time). Neutrophil elastase concentration increased markedly as early as 30 min after the onset of cardiopulmonary bypass and peaked 5 min after protamine administration. Levels were not significantly different between the three groups. A similar finding was apparent for C3d release. Interleukin 8 concentrations also demonstrated a considerable increase related to cardiopulmonary bypass in all groups, but there was a significantly more rapid decline in interleukin 8 concentrations in the normothermic group in the postoperative period. Eluted IgG fraction showed a much earlier peak concentration than the other markers, occurring within 30 min of the start of cardiopulmonary bypass. Levels reached a plateau, before declining soon after the end of bypass and remained higher than preoperative values at 24 h. There was no difference between the three groups. The cumulative release of all markers was calculated from the concentration-time curves, and was not statistically different between groups.

CONCLUSION

Normothermic systemic perfusion was not shown to produce a more profound inflammatory response compared to hypothermic and moderately hypothermic cardiopulmonary bypass.

Cerebrovascular cytokine responses during coronary artery bypass surgery: specific production of interleukin-8 and its attenuation by hypothermic cardiopulmonary bypass

Brain dysfunction after cardiopulmonary bypass (CPB) is common, and it has been hypothesized that this injury might be due partly to activation of inflammatory processes in the brain. We measured juguloarterial gradients for interleukin-1beta, interleukin-6, and interleukin-8 (IL-8) as indices of local proinflammatory cytokine production in the brain and studied the effect of temperature during CPB on these changes. Twelve patients undergoing coronary artery bypass graft surgery (normothermic CPB n = 6, hypothermic CPB n = 6) were studied. Cytokine levels were measured in paired arterial and jugular bulb samples obtained before, during, and after CPB. Although systemic levels of all three cytokines increased during and after CPB, increases in juguloarterial cytokine gradients were observed only for IL-8. Juguloarterial IL-8 gradients started to increase 1 h post-CPB and were significantly elevated 6 h post-CPB (P < 0.05). At this time point, the median (interquartile range) juguloarterial IL-8 gradients were significantly larger in the normothermic CPB group (25.81 [24.49-39.51] pg/mL) compared with the hypothermic CPB group (6.69 [-0.04 to 15.47] pg/mL; P < 0.05). These data imply specific and significant IL-8 production in the cerebrovascular bed during CPB and suggest that these changes may be suppressed by hypothermia during CPB.

IMPLICATIONS

Using juguloarterial gradients to measure cerebrovascular cytokine production is novel in the setting of cardiopulmonary bypass and implicates the cerebral activation of inflammatory processes, which may contribute to brain dysfunction. Hypothermia during cardiopulmonary bypass may significantly attenuate this response.

Effect of cold exposure, exercise and high altitude on plasma endothelin-1 and endothelial cell markers in man

The aims were to examine the effect of cold exposure, exercise and high altitude on plasma concentrations of big endothelin-1, endothelin-1, von Willebrand factor and serum e-selectin in twenty five healthy male volunteers. Clinical evaluation and venesection were performed before and after 24 hours of low altitude mountaineering, exposure to temperatures of -18 degrees C and +4 degrees C and whilst ascending from sea level to an altitude of 5000 m in the Karakoram. Plasma big endothelin-1, plasma endothelin-1 and serum soluble e-selectin concentrations were significantly elevated after two hours at -18 degrees C (p < 0.05, p < 0.05 and p < 0.01 respectively). At +4 degrees C, plasma big endothelin-1 and endothelin-1 concentrations rose significantly after 5 hours (p < 0.005 for both) but not after 2.5 hours. Low altitude mountaineering did not alter circulating marker concentrations. At high altitude, big endothelin-1 and endothelin-1 (p < 0.01 for both) rose significantly at 2500 m and initially at 5000 m but returned to sea level values after prolonged exposure to 5000 m. Serum e-selectin rose at all altitudes greater than sea level (p < 0.05). In conclusion, exposure to high altitude, moderate cold or freezing temperatures, but not exercise, selectively activates endothelial cells increasing endothelin-1 production. Cold exposure may contribute to the observed increase in plasma endothelin-1 in mountaineers at high altitude.

Postoperative lumbar microdiscectomy pain. Minimalization by irrigation and cooling

STUDY DESIGN

Seventy patients undergoing de novo lumbar microdiscectomy were prospectively randomized into a control group and a group in which cold intraoperative wound irrigation along with postoperative wound cooling was used. Postoperative analgesia requirements and length of hospital stay were analyzed and correlated.

OBJECTIVES

To evaluate the role of intraoperative cold irrigation and postsurgical cooling in minimizing postoperative lumbar discectomy pain.

SUMMARY OF BACKGROUND DATA

Regulated hypothermia has been used frequently in pain reduction; however, the efficacy of such a strategy in lumbar disc procedures has not been established.

METHODS

Seventy patients (43 men and 27 women), operated on the first time for lumbar disk herniation were prospectively randomized into two groups. A standard microdiscectomy was performed on all patients. In cohort A the wound site was irrigated with a cold (18 C) 5% bacitracin solution for 5 minutes. Additionally, a cooling microtemperature pump was placed on the wound site for 24 hours after surgery. The patients in the control group (cohort B) were treated in a standard fashion without additional hypothermic therapy. All patients received postoperative analgesia through a self-administered morphine pump. The amount of postoperative analgesia received was calculated in morphine equivalents per kilogram. The length of hospital stay was also noted.

RESULTS

The total amount of pain medication was significantly smaller in cohort A than in the control group (cohort B). For the statistical analysis of the results, covariate analyses for both the length of hospital stay and the morphine dose were used, demonstrating a statistically significant difference with P = 0.0001. No postoperative wound infection was noted in either group.

CONCLUSIONS

Intraoperative and postoperative wound site cooling is a safe, inexpensive, and efficient therapeutic method. It reduces the patients' postoperative pain, promotes earlier ambulation and decreases the length of hospital stay.

Inflammatory response to cardiopulmonary bypass using roller or centrifugal pumps

BACKGROUND

The inflammatory response in 29 patients undergoing coronary artery bypass grafting using either roller or centrifugal (CFP) pumps was evaluated in a prospective study.

METHODS

Patients were randomized in roller pump (n = 15) and CFP (n = 14) groups. Terminal complement complex activation (SC5b-9) and neutrophil activation (elastase) were assessed during the operation. Cytokine production (tumor necrosis factor-alpha, interleukin-6, interleukin-8) and circulating adhesion molecules (soluble endothelial-leukocyte adhesion molecule-1 and intercellular adhesion molecule-1) were assessed after the operation.

RESULTS

Release of SC5b-9 after stopping cardiopulmonary bypass and after protamine administration was higher in the CFP group (p = 0.01 and p = 0.004). Elastase level was higher after stopping cardiopulmonary bypass using CFP (p = 0.006). Multivariate analysis confirmed differences between roller pump and CFP groups in complement and neutrophil activation. After the operation, a significant production of cytokines was detected similarly in both groups, with peak values observed within the range of 4 to 6 hours after starting cardiopulmonary bypass. However, interleukin-8 levels were higher using CFP 2 hours after starting cardiopulmonary bypass (p = 0.02). Plasma levels of adhesion molecules were similar in both groups within the investigation period.

CONCLUSIONS

During the operation, CFP caused greater complement and neutrophil activation. After the operation, the inflammatory response was similar using either roller pump or CFP.

Leukocyte depletion during cardiac operation: a new approach through the venous bypass circuit

BACKGROUND

Leukocyte depletion recently has been introduced for cardiac surgical patients to attenuate leukocyte-mediated inflammation and organ reperfusion injury. We evaluated the feasibility of a new leukocyte depletion method in which systemic leukocyte depletion is achieved through the venous side of the cardiopulmonary bypass circuit under low blood flow.

METHODS

Forty cardiac surgical patients undergoing cardiopulmonary bypass were allocated randomly to a leukocyte depletion group (n = 20) and a control group (n = 20). In the depletion group, leukocyte filtration was achieved with two filter sets located between the venous drainage and the venous reservoir. Leukocyte filtration was commenced after the start of rewarming but before the release of the aortic cross-clamp, and it was driven by a spare roller pump of the heart-lung machine.

RESULTS

All the episodes of filtration went smoothly within a period of 10 minutes and with a blood flow rate of 400 mL/min. The mean leukocyte removal rate calculated at the end of filtration was 69%. Circulating leukocytes were reduced by 38% in the depletion group compared with the control group at the moment of cross-clamp release (4.3x10(9)/L versus 6.8x10(9)/L, p<0.05). The postoperative inflammatory response also was reduced as indicated by less production of interleukin-8 (p<0.05). Clinically, there was no significant difference between the two groups in postoperative PaO2 or pulmonary hemodynamics.

CONCLUSIONS

It is technically feasible to deplete circulating leukocytes through the venous side of the cardiopulmonary bypass circuit with a low blood flow rate. Future studies should focus on the duration and timing of leukocyte depletion to optimize the methodology of leukocyte depletion for cardiac surgical patients.

Effects of cardiopulmonary bypass on leukocyte and endothelial adhesion molecules

During the inflammatory response, triggered by cardiopulmonary bypass, interaction between activated leukocytes, platelets, and endothelial cells is mediated through the expression of three main groups of adhesion molecules: the selectins, the integrins, and the immunoglobulin superfamily. The selectins, which mediate the initial rolling of the leukocyte on the endothelium, are divided in three subgroups: L-selectin is expressed on all three leukocyte types, P-selectin is expressed on platelets and endothelial cells, and E-selectin is only expressed on endothelial cells. Integrins can be found on most cell types, consist of an alpha and a beta subunit and mediate firm adhesion of the leukocyte and migration into the tissues. They are classified into subgroups according to the type of their beta subunit. Immunoglobulins such as ICAM-1 and VCAM-1 are expressed mainly on endothelium and act as ligands for certain integrins. This review article summarizes the existing, and rapidly expanding, literature concerning the effects of cardiopulmonary bypass on the expression of leukocyte and endothelial adhesion molecules. Deeper understanding of the, behavior and the role of adhesion molecules during cardiopulmonary bypass may facilitate effective intervention in the inflammatory response process and suppression of its adverse effects.

Inflammatory response to cardiopulmonary bypass using two different types of heparin-coated extracorporeal circuits

Previous reports have highlighted the disparity in biocompatibility of two differently engineered heparin coatings during the cardiopulmonary bypass (CPB) procedure. The aim of this prospective study was to evaluate the impact of the difference in haemocompatibility provided by either the Duraflo II equipment or the Carmeda equipment in the terminal inflammatory response observed after coronary artery surgery. Thirty patients were randomly allocated to two groups to be operated on using either Duraflo II equipment (group I) or Carmeda equipment (group 2) for extracorporeal circulation (ECC). Initial inflammatory response was assessed by terminal complement complex activation (SC5b-9). The late inflammatory response observed in the postoperative period was assessed by measuring cytokine production (tumour factor necrosis (TNF alpha), interleukin IL-6, interleukin IL-8) and circulating concentrations of adhesion molecules (ELAM-1, ICAM-1). The release of SC5b-9 after CPB and after protamine administration was lower in group 2 than in group 1 (p = 0.0002 and p = 0.006, respectively). A significant production of cytokines was detected in both groups with peak values observed within the time range of 4-6 h after the start of CPB.

Measures to control blood activation during assisted circulation

Major improvements in heart assist devices have allowed prolonged mechanical circulatory support with successful subsequent weaning or heart transplantation. The contact of blood with biomaterials used in life-sustaining devices and numerous biomaterial-independent factors elicit a systemic inflammatory response, which involves activation of various plasma protein systems and blood cells. Prolonged mechanical circulatory support elicits a systemic inflammatory response and hemostatic perturbations similar to that reported during cardiopulmonary bypass. However, in the setting of prolonged assistance, time has a complex and ill-known influence on blood activation. Methods to reduce blood activation during prolonged assisted circulation are derived from cardiopulmonary bypass investigations. Improving the biocompatibility of artificial devices can be achieved either by biomaterial surface modifications, by inhibition of biologic cascades leading to blood activation, or by controlling end points of biologic cascades. However, the necessity to respect the integrity of the organism during prolonged assistance precludes most systemic interventions and limits the control of blood activation to the area of the device.

Expression of soluble endothelial adhesion molecules in clinical cardiopulmonary bypass

Soluble endothelial adhesion molecule expression in clinical cardiopulmonary bypass (CPB) was investigated. Neutrophil-mediated endothelial injury plays an important role in CPB-induced organ dysfunction. The adhesion of neutrophil to the endothelium is central to this process. It has been well documented that CPB induces neutrophil activation and changes in neutrophil adhesion molecule expression, but the effect of CPB on endothelial cell activation is not known. This study was designed to measure soluble endothelial adhesion molecules during CPB. We made serial measurements (by specific enzyme-linked immunoabsorbent assay) of plasma levels of the soluble endothelial adhesion molecules, ICAM-1 and E-selectin in patients undergoing routine CPB (n = 7) and in a control group (thoracotomy, n = 3). The results show an initial significant decrease during CPB followed by an increase in plasma E-selectin from 29.3 +/- 5.1 ng/ml (mean +/- SEM) prebypass to 34.0 +/- 5.4 ng/ml at 48 h postbypass. Likewise, plasma ICAM-1 significantly decreased during CPB and then increased from 246.3 +/- 38.0 ng/ml before bypass to 324.8 +/- 25.0 ng/ml and 355.0 +/- 23.0 ng/ml at 24 and 48 h after bypass, respectively. The rise in levels is statistically significant (p < 0.05). This study shows a decrease in circulating ICAM-1 and soluble E-selectin during CPB and an increase in their levels at 48 h after CPB.

A second-generation blood substitute (perfluorodichlorooctane emulsion) does not activate complement during an ex vivo circulation model of bypass

OBJECTIVES

To examine whether a second-generation perfluorocarbon (PFC) blood substitute added to the cardiopulmonary bypass (CPB) prime influences complement production.

DESIGN

A prospective, randomized, single-blinded, ex vivo model.

SETTING

A university hospital, laboratory, and clinics.

PARTICIPANTS

Ten healthy adult consented volunteer blood donors (five men, five women).

INTERVENTIONS

Ex vivo closed-loop extracorporeal circuit including membrane oxygenator, tubing, and filter primed with crystalloid or crystalloid plus PFC was circulated for 1 hour with the addition of 500 mL of heparinized fresh human whole blood.

MEASUREMENTS AND MAIN RESULTS

Laboratory specimens were drawn from the circuit at 10-minute intervals for 1 hour and measured for complement (C3a, Bb fragment) concentrations, blood gases, fibrinogen concentration, platelet count, and hematocrit. In the PFC group, C3a and Bb fragments were equal to or less than those in the group that received crystalloid alone.

CONCLUSION

The second-generation PFC added to the prime of a CPB circuit does not independently increase complement production.

Effects of cardiopulmonary bypass on neonatal and paediatric inflammatory profiles

OBJECTIVE

Cardiopulmonary bypass (CPB) causes significant morbidity in paediatric patients, yet the mechanisms involved in the related inflammatory processes (resulting in capillary leak and edema) are poorly understood. Moreover, earlier palliative and corrective intervention in neonates and infants has provided the cohorts of patients about whom little is known of their proinflammatory response.

METHODS

In the present two group study, 14 neonates (age 1-28 days, 2.5-4.5 kg) and 13 infants (2-12 months, 3-7 kg), undergoing CPB for congenital heart disease were consecutively recruited. The two cohorts were well matched in terms of CPB and aortic cross-clamp times (P > 0.1). Blood samples were collected on induction of anaesthesia, 5 min following onset of CPB, at the end of CPB, and 30 min, 2 and 24 h post-protamine (PP) administration. Plasma concentration of cytokines interleukin-6 (IL-6) and interleukin-8 (IL-8), terminal complement complex (C5b-9) neutrophil counts and leucocyte elastase were measured.

RESULTS

Plasma levels of all inflammatory markers significantly increased in both groups during and following CPB as compared to baseline. During and following CPB the change in IL-8 level was more pronounced in neonates (peak 30 min PP, median(range): 1062 (182-3872) pg/ml) than in infants 568 (172-1368) pg/ml), P = 0.01. Changes in IL-6 level were indistinguishable between groups intraoperatively, but remained significantly higher at 24 h in neonates (P = 0.02). Peri and postoperative levels of C5b-9 were significantly higher in infants than in neonates (peak 30 min PP, median (range): 984 (118-1142) ng/ml vs 458 (22 1340) ng/ml in neonates respectively, P = 0.01) but were similar at 24 h. Despite this, leucocyte elastase profiles did not differ significantly between the respective cohorts.

CONCLUSION

These results indicate that there may be differences between neonates and infants with regard to the inflammatory response to CPB and neonatal patients merit further investigation in order to elucidate whether the pathophysiology of their CPB related inflammatory response and its clinical sequelae differs from their older counterparts.

Inflammatory response to cardiopulmonary bypass: mechanisms involved and possible therapeutic strategies

BACKGROUND

Recent study of the inflammatory reactions occurring during and after cardiopulmonary bypass (CPB) has improved our understanding of the involvement of the inflammatory cascade in perioperative injury. However, the exact mechanisms of this complex response remain to be fully determined.

METHODS

Literature on the inflammatory response to CPB was reviewed to define current knowledge on the possible pathways and mediators involved, and to discuss recent developments of therapeutic interventions aimed at attenuating the inflammatory response to CPB.

RESULTS

CPB has been shown to induce complement activation, endotoxin release, leukocyte activation, the expression of adhesion molecules, and the release of many inflammatory mediators including oxygen-free radicals, arachidonic acid metabolites, cytokines, platelet-activating factor, nitric oxide, and endothelins. Therapies aimed at interfering with the inflammatory response include the administration of pharmacologic agents such as corticosteroids, aprotinin, and antioxidants, as well as modification of techniques and equipment by the use of heparin-coated CPB circuits, intraoperative leukocyte depletion, and ultrafiltration.

CONCLUSIONS

Improved understanding of the inflammatory reactions to CPB can lead to improved patient outcome by enabling the development of novel therapies aimed at limiting this response.

Serum soluble selectins in patients undergoing cardiopulmonary bypass. Relationship with circulating blood cells and inflammation-related cytokines

BACKGROUND

Membrane-bound selectins mediate the adhesion among leukocytes, platelets and endothelial cells, while circulating (soluble) selectins may function as competitive inhibitors of them. Open heart surgery is known to induce activation of these cells.

METHODS

We studied the acute responses of soluble selectins, circulating blood cells and inflammation-related cytokines in 12 patients undergoing elective open heart surgery with cardiopulmonary bypass. Serial blood samples were withdrawn before, during and after surgery.

RESULTS

Serum soluble E-selectin concentrations did not change significantly during all the perioperative period. In contrast, P-selectin decreased after the initiation of cardiopulmonary bypass and remained low until the end of surgery. L-selectin showed a similar course. A decrease in platelet count and albumin was found during the perioperative period and an increase in leukocyte count was found after cardiopulmonary bypass. Clear elevations in circulating IL (Interleukin)-6, IL-8, and IL-10 were found after the end of surgery, while IL-12 levels remained undetectable.

CONCLUSIONS

While serum inflammatory cytokines clearly rise in response to open heart surgery, soluble selectins do not change (E) or decrease (P and L). Correcting for haemodilution, E-selectin rises postoperatively, but the decrease in P- and L-selectins is not explained by haemodilution.

The influence of cardiopulmonary bypass on cytokines and cell-cell communication

Cardiopulmonary bypass (CPB) is characterized by systemic endotoxemia immediately after its onset as well as the systemic release of proinflammatory cytokines, including tumor necrosis factor-alpha and the interleukins 1 and 6. Recent studies document that increased morbidity and mortality rates correlate with elevated systemic concentrations of these proinflammatory cytokines during adult and neonatal sepsis, following thoracoabdominal aortic aneurysm repair, as well as following CPB. These proinflammatory cytokines induce increased neutrophil and endothelial surface adhesive molecule expression, thereby promoting enhanced neutrophil-endothelial adherence. Increased neutrophil-endothelial adherence and subsequent neutrophil organ binding are thought to be a "final common pathway" of organ injury during clinical inflammatory conditions. Proinflammatory cytokines also increase cellular expression of inducible nitric oxide synthase, thus increasing cellular production of nitric oxide, a known inflammatory mediator. This review discusses recent evidence of the adverse effects of proinflammatory cytokine release during CPB and therapeutic modalities that can reduce the systemic concentrations of these mediators of inflammation.

Cytokine responses to cardiopulmonary bypass: lessons learned from cardiac transplantation

BACKGROUND

A growing body of evidence relates the release during cardiopulmonary bypass (CPB) of proinflammatory cytokines, such as tumor necrosis factor-alpha, interleukin (IL)-6, and IL-8, to the postoperative systemic inflammatory response syndrome. Antiinflammatory cytokines, such as IL-10, however, may also play an important role in limiting these complications.

METHODS

The English-language literature was reviewed. Emphasis was placed on cytokine responses during clinical CPB for cardiac operations and, in particular, for heart and heart-lung transplantation.

RESULTS

The recent data indicate that (1) although cytokine release can be triggered by many factors during CPB, ischemia-reperfusion may play the most important role; (2) the levels of tumor necrosis factor-alpha, IL-6, and IL-8 are correlated with the duration of cardiac ischemia and the myocardium is a major source of these three cytokines during CPB; (3) IL-10 levels are correlated with the duration of CPB and the liver is a major source of IL-10 during CPB; and (4) steroid pretreatment is an effective intervention to inhibit the release of proinflammatory cytokines and enhance IL-10 production.

CONCLUSIONS

The improved knowledge of cytokine responses to CPB may help to develop interventions aimed at reducing postoperative morbidity and mortality.

Endothelial cell injury in cardiovascular surgery: the systemic inflammatory response

Many of the components currently used to perform cardiovascular operations lead to systemic insults that result from cardiopulmonary bypass circuit-induced contact activation, circulatory shock, and resuscitation, and a syndrome similar to endotoxemia. Experimental observations have demonstrated that these events have profound effects on activating endothelial cells to recruit neutrophils from the circulation. Once adherent to the endothelium, neutrophils release cytotoxic proteases and oxygen-derived free radicals, which are responsible for much of the end-organ damage seen after cardiovascular operations. Recently the cellular and molecular mechanisms of endothelial cell activation have become increasingly understood. It is conceivable that once the molecular mechanisms of endothelial cell activation are better defined, therapies will be developed allowing the selective or collective inhibition of vascular endothelial activation during the perioperative period.