Mild hyperthermia down-regulates receptor-dependent neutrophil function

Neutrophil extracellular traps formation and clearance is enhanced in fever and attenuated in hypothermia

Fever and hypothermia represent two opposite strategies for fighting systemic inflammation. Fever results in immune activation; hypothermia is associated with energy conservation. Systemic Inflammatory Response Syndrome (SIRS) remains a significant cause of mortality worldwide. SIRS can lead to a broad spectrum of clinical symptoms but importantly, patients can develop fever or hypothermia. During infection, polymorphonuclear cells (PMNs) such as neutrophils prevent pathogen dissemination through the formation of neutrophil extracellular traps (NETs) that ensnare and kill bacteria. However, when dysregulated, NETs also promote host tissue damage. Herein, we tested the hypothesis that temperature modulates NETs homeostasis in response to infection and inflammation. NETs formation was studied in response to infectious (Escherichia coli, Staphylococcus aureus) and sterile (mitochondria) agents. When compared to body temperature (37°C), NETs formation increased at 40°C; interestingly, the response was stunted at 35°C and 42°C. While CD16+ CD49d+ PMNs represent a small proportion of the neutrophil population, they formed ~45-85% of NETs irrespective of temperature. Temperature increased formyl peptide receptor 1 (FPR1) expression to a differential extent in CD16+ CD49d- vs. CD49d+ PMNSs, suggesting further complexity to neutrophil function in hypo/hyperthermic conditions. The capacity of NETs to induce Toll-like receptor 9 (TLR9)-mediated NF-κB activation was found to be temperature independent. Interestingly, NET degradation was enhanced at higher temperatures, which corresponded with greater plasma DNase activity in response to temperature increase. Collectively, our observations indicate that NETs formation and clearance are enhanced at 40°C whilst temperatures of 35°C and 42°C attenuate this response. Targeting PMN-driven immunity may represent new venues for intervention in pathological inflammation.

Aggressive intraoperative warming and postoperative pulmonary complications in elderly patients recovering from esophageal cancer surgery: sub-analysis of a randomized trial

Background

Elderly patients having esophagectomies often become hypothermic which may promote complications. We tested the hypothesis that aggressive warming to a core temperature of 37°C reduces postoperative pulmonary complications (PPCs) in elderly patients having esophageal cancer resections.

Methods

This study was a pre-defined sub-study of a multi-center, parallel group, superiority trial (PROTECT). Patients aged >65 years and having elective radical resection of esophageal cancer in a single center were randomly allocated into either aggressive warming group (target intraoperative core temperatures of 37°C) or routine thermal management group (target intraoperative core temperatures of 35.5°C). The primary endpoint was the incidence of PPCs. Secondary endpoints included duration of chest tube drainage and other postoperative complications.

Results

A total of 300 patients were included in the primary analysis. PPCs occurred in 27 (18%) of 150 patients in the aggressive warming group and 31 (21%) of 150 patients in the routine thermal management group. The relative risk (RR) of aggressive versus routine thermal management was 0.9 (95% CI: 0.5, 1.4; p = 0.56). The duration of chest drainage in patients assigned to aggressive warming was shorter than that assigned to routine thermal management: 4 (3, 5) days vs. 5 (4, 7) days; hazard ratio (HR) 1.4 [95% CI: 1.1, 1.7]; p = 0.001. Fewer aggressively warmed patients needed chest drainage for more than 5 days: 30/150 (20%) vs. 51/150 (34%); RR:0.6 (95% CI: 0.4, 0.9; p = 0.03). The incidence of other postoperative complications were similar between the two groups.

Conclusion

Aggressive warming does not reduce the incidence of PPCs in elderly patients receiving esophagectomy. The duration of chest drainage was reduced by aggressive warming. But as a secondary analysis of a planned sub-group study, these results should be considered exploratory.

Clinical trial registration

https://www.chictr.org.cn/showproj.aspx?proj=37099, ChiCTR1900022257.

The Effects of Temperature Management on Brain Microcirculation, Oxygenation and Metabolism

Purpose: Target temperature management (TTM) is often used in patients after cardiac arrest, but the effects of cooling on cerebral microcirculation, oxygenation and metabolism are poorly understood. We studied the time course of these variables in a healthy swine model.Methods: Fifteen invasively monitored, mechanically ventilated pigs were allocated to sham procedure (normothermia, NT; n = 5), cooling (hypothermia, HT, n = 5) or cooling with controlled oxygenation (HT-Oxy, n = 5). Cooling was induced by cold intravenous saline infusion, ice packs and nasal cooling to achieve a body temperature of 33–35 °C. After 6 h, animals were rewarmed to baseline temperature (within 5 h). The cerebral microvascular network was evaluated (at baseline and 2, 7 and 12 h thereafter) using sidestream dark-field (SDF) video-microscopy. Cerebral blood flow (laser Doppler MNP100XP, Oxyflow, Oxford Optronix, Oxford, UK), oxygenation (PbtO₂, Licox catheter, Integra Lifesciences, USA) and lactate/pyruvate ratio (LPR) using brain microdialysis (CMA, Stockholm, Sweden) were measured hourly. Results: In HT animals, cerebral functional capillary density (FCD) and proportion of small-perfused vessels (PSPV) significantly decreased over time during the cooling phase; concomitantly, PbtO₂ increased and LPR decreased. After rewarming, all microcirculatory variables returned to normal values, except LPR, which increased during the rewarming phase in the two groups subjected to HT when compared to the group maintained at normothermia. Conclusions: In healthy animals, TTM can be associated with alterations in cerebral microcirculation during cooling and altered metabolism at rewarming.

Genetic Variants of Matrix Metalloproteinase and Sepsis: The Need Speed Study

Many causal mechanisms in sepsis susceptibility are largely unknown and the functional genetic polymorphisms (GP) of matrix metalloproteinases (MMPs) and their natural tissue inhibitor of MMPs (TIMP1) could play a role in its development. GPs of MMPs and TIMP (namely MMP-1 rs1799750, MMP-3 rs3025058, MMP-8 rs11225395, MMP-9 rs2234681, and TIMP-1 rs4898) have been compared in 1058 patients with suspected sepsis to assess the association with susceptibility and etiology of sepsis. Prevalence of MMP8 rs11225395 G/G genotype was higher in sepsis patients than in those with non-infective Systemic Inflammatory Reaction Syndrome (35.6 vs. 26%, hazard ratio, HR 1.56, 95% C.I. 1.04–2.42, p = 0.032). G/G patients developed less hyperthermia (p = 0.041), even after stratification for disease severity (p = 0.003). Patients carrying the 6A allele in MMP3 rs3025058 had a higher probability of microbiologically-proven sepsis (HR 1.4. 95%C.I. 1.01–1.94, p = 0.044), particularly when due to virus (H.R. 2.14, 95% C.I. 1.06–4.31, p = 0.046), while MMP-1 G/G genotype patients carried a higher risk for intracellular bacteria (Chlamydia, Mycoplasma, and Legionella, H.R. 6.46, 95% C.I. 1.58–26.41, p = 0.003). Neither severity of sepsis at presentation, nor 30-day mortality were influenced by the investigated variants or their haplotype. MMP8 rs11225395 G/G carriers have lower temperature at presentation and a more than 50% increased susceptibility to sepsis. Among patients with sepsis, carriers of MMP1 rs1799750 G/G have an increased susceptibility for intracellular pathogen infections, while virus serology is more often positive in those with the MMP3 rs3025058 A/A genotype.

Intensive fever control using a therapeutic normothermia protocol in patients with febrile early septic shock: A randomized feasibility trial and exploration of the immunomodulatory effects

Objectives:

Fever control has been shown to reduce short-term mortality in patients with septic shock. This study aimed to explore the feasibility of early intensive fever control in patients with septic shock and to assess the immunomodulatory effects of this intervention.

Methods:

In this single-center, randomized, open-label trial, febrile patients with septic shock presenting to the emergency department were assigned to either a standard fever control or therapeutic normothermia group. Therapeutic normothermia involved intensive fever control in maintaining normothermia below 37°C. The primary outcome was the feasibility of fever control for 24 h. Secondary outcomes included changes in immunomodulatory biomarkers and adverse events.

Results:

Fifteen patients were enrolled and analyzed. Fever control was comparable in both groups, but significantly more patients in the therapeutic normothermia group experienced shivering (p = 0.007). Both groups demonstrated increased C-reactive protein and unchanged neutrophil chemotaxis and CD11b expression. The therapeutic normothermia group revealed significant decreased IL-6 and IL-10. The standard fever control group significantly expressed increased monocytic human leukocyte antigen. There were no significant differences between the groups in terms of immunomodulation.

Conclusions:

Therapeutic normothermia was feasible in patients with febrile septic shock but was not superior to standard fever control in terms of average body temperature and host defense function. Shivering was more frequent in the therapeutic normothermia group.

Trial registration:

Thai Clinical Trials Registry number: TCTR20160321001

Effects of Inadvertent Perioperative Hypothermia on Metabolic and Inflammatory Mediators

Objective

The aim of the present study was to investigate the effects of perioperative undesirable hypothermia on inflammatory (interleukin (IL)-8, IL-10, IL-18, IL-23 and pentraxin (PTX)-3) and metabolic responses (cortisol and insulin) and recovery time.

Methods

A total of 60 patients between the ages of 18 and 65 years who were in the lumbar stabilisation operation were included in the study. In this prospective, randomised controlled study, two groups were constituted as with warmed (Group N) and not warmed (Group C) patients before and during the operation. Diuresis, blood loss, body temperature and side effects were recorded with IL-8, IL-10, IL-18, IL-23, PTX-3, cortisol and insulin levels.

Results

Perioperative diuresis was significantly higher in Group C. Aldrete score was significantly higher in Group N with less shivering and vomiting in the postoperative period. IL-10, PTX-3 and cortisol levels were found to be significantly higher in Group C in the first postoperative hour. PTX-3 and cortisol were found to be significantly higher in Group C after 24 h of the operation. Insulin was significantly higher in Group N. In 72 h, IL-8 in Group N and cortisol level in Group C were significantly higher.

Conclusion

Positive effects of heating the patients in the perioperative period on haemorrhage, diuresis, complications and recovery time were observed in our study. In addition, maintenance of normothermia appeared to modulate the biomarkers that indicate the inflammatory and metabolic responses.

Thermosensitive liposomal cisplatin in combination with local hyperthermia results in tumor growth delay and changes in tumor microenvironment in xenograft models of lung carcinoma

Treatment efficacy of a heat-activated thermosensitive liposome formulation of cisplatin (CDDP), known as HTLC, was determined in xenograft models of non-small-cell lung carcinoma. The short-term impact of local hyperthermia (HT) on tumor morphology, microvessel density and local inflammatory response was also evaluated. The HTLC formulation in combination with local HT resulted in a significant advantage in therapeutic effect in comparison with free drug and a non-thermosensitive liposome formulation of CDDP (i.e. Lipoplatin^TM) when administered at their maximum tolerated doses. Local HT-induced widespread cell necrosis and a significant reduction in microvessel density in the necrotic regions of tumors. CD11b-expressing innate leukocytes were demonstrated to infiltrate and reside preferentially at the necrotic rim of tumors, likely as a means to phagocytose-damaged tissue. Colocalization of CD11b with a marker of DNA damage (i.e. γH2AX) revealed a small portion of CD11b-expressing leukocytes that were possibly undergoing apoptosis as a result of HT-induced damage and/or the short lifespan of leukocytes. Overall, HT-induced tissue damage (i.e. at 24-h post-treatment) alone did not result in significant improvements in treatment effect, rather, the enhancement in tumor drug availability was correlated with improved therapeutic outcomes.

High temperature affects the phagocytic activity of human peripheral blood mononuclear cells

BACKGROUND

The ability for engulfment of pathogens and inert particles is the key hallmark of the phagocytic cells. Phagocytes play a significant role in the modulation of local or extended inflammation. Since fever activates a number of factors linked with the immune response it was the goal of this study to examine the in vitro effect of hyperthermia on the phagocytic capacity, the number of phagocytic cells and the viability of human peripheral blood mononuclear cells (PBMC) at 37 and 40°C.

METHODS

PBMC were incubated with 0.8 μm polysterene latex beads, for 2 hours at 37 and 40°C. The number of phagocytic cells, and that of latex particles internalized by each individual cell was counted with a light microscope. In addition, the percentage of viable cells and the number of active metabolic cells was evaluated.

RESULTS

A temperature of 40°C significantly increased the number of phagocytic cells and the phagocytic index by 41 and 37% respectively, as compared to cells incubated at 37°C. While the number of vital cells (trypan blue test) did not differ statistically at both temperatures, the number of active metabolic cells (XTT test) after 2 h of incubation at 40°C was 17% higher as compared with that at 37°C. However, the number of active metabolic cells after 24 h of incubation at 40°C was 51% lower compared with cells incubated at 37°C.

CONCLUSIONS

The increased phagocytic capacity of human peripheral blood monocytes at high temperature further enlightens the immunomodulatory effect of fever in the immune responses during inflammation.

Factors affecting the risk surgical site infection and methods of reducing

According to estimates by the National Audit Office (NAO) hospital acquired infections (HAl), in particular surgical site infections (SSls), cost the NHS on average 3200 pounds per SSI and cause a mortality rate of at least five thousand patients a year (Leaper 2010). Despite practitioners' knowledge of safe working technique and control of infection, reported cases of nosocomial infections are still high, despite a reduction in-rate from 9% in 1993/4 to 8.2% in 2006 (Roberts & Cookson 2009).

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.

Influence of non-ventilatory options on postoperative outcome

Perioperative patient handling should urgently be updated according to current evidence and, if none is available, at least according to physiological knowledge. To prevent pulmonary aspiration, preoperative fasting for 2 h (clear fluids) and 6 h (solid food) and abdication of 20 min for smoking is sufficient. Beta-blockage requires an indication. Bowel preparation should be abandoned and minimal invasive surgery as well as local and regional anaesthesia should be used where possible. Fluid therapy should be rational and requirement-adapted, and hypothermia, postoperative nausea and vomiting, unnecessary drains, tubes and catheters avoided. A multi-modal opioid-sparing pain therapy, sufficient oxygenation as well as early nutrition and mobilisation all play an important role for patient outcome. Recent studies have postulated that combining single-modality evidence-based care principles into a multi-modal effort to enhance postoperative recovery has improved patient outcome. Henrik Kehlet termed such a principle the 'fast-track concept', comprehending the entire perioperative phase starting with preoperative preparation, over atraumatic surgical and anaesthesiological techniques reducing the neuroendocrine stress response and also comprising the postoperative treatment. This strategy has been shown to positively influence organ function, homeostasis, morbidity, need for hospitalisation and convalescence and, therefore, to reduce costs. Despite these promising results, general implementation of evidence-based measures leaves a lot to be desired. Further development of surgical minimally invasive techniques and ongoing evaluation of procedure-specific strategies is urgently warranted.

Bilateral simultaneous endogenous Aspergillus endophthalmitis in an immunocompetent patient

PURPOSE

To report a case of bilateral endogenous Aspergillus endophthalmitis in an immunocompetent patient.

METHODS

We report a young immunocompetent 26-year-old Indian woman who presented with bilateral simultaneous endogenous endophthalmitis and was managed with pars plana vitreous surgery in both the eyes.

RESULTS

Smear examination of the vitrectomy specimen from the left eye identified septate hyphae with acute-angle branching, which on culture showed growth of Aspergillus fumigatus. A detailed systemic evaluation failed to reveal any systemic focus or predisposing factor for fungal infection. The patient had received an intravenous dextrose infusion 2 weeks before this episode while being treated at a rural hospital for malarial infection. During follow-up, she developed bilateral rhegmatogenous retinal detachment requiring revised pars plana vitreous surgery with silicon oil tamponade.

CONCLUSION

An immunocompetent patient can present with bilateral simultaneous endogenous Aspergillus endophthalmitis after receiving an intravenous infusion of presumably contaminated dextrose solution.

Effect of Dim and Bright Light Exposure on Some Immunological Parameters Measured under Thermal Neutral Conditions

This study assesses the effects of ambient light conditions, under a thermoneutral environment, on selected immunological parameters of 7 healthy young women (aged 19 to 22 yrs). Subjects entered the bioclimatic chamber at 11: 00 h, controlled at 26 degrees C and 60% relative humidity, a "neutral climate". They lead a well-regulated life in the climatic chamber (pre-condition) while exposed to dim (200 lux) or, on the next day, bright (5000 lux) light between 06 : 00 to 12 : 00 h. Just before the end of each period of light exposure, a blood sample was taken for later immunological assay of white blood cell count (WBC), phagocytosis, interferon-gamma (IFN-gamma), interleukin-4 (IL-4), CD69 T cells (CD69), CD4+CD25+ T cells (CD4+CD25+), and transforming growth factor-beta 1 (TGF-beta1). The results, when compared with the pre-condition, were as follows: 1) CD69 and IFN-gamma increased during normal conditions without thermal stress under dim light; 2) WBC increased and IL-4 decreased under bright light; 3) as shown by the highly significant decrease of TGF-beta1, the immune system was activated under bright light; 4) phagocytosis tended to increase under bright light exposure; 5) CD69 and IFN-gamma were significantly higher, and CD4+CD25+ tended to decrease under bright light; 6) phagocytosis tended to be lower and TGF-beta1 significantly higher under dim light, indicating a decline of immune system function. Taken together, this preliminary single time-point sampling study infers that some parameters are activated (CD69) while others are attenuated (phagocytosis, TGF-beta1) according to the environmental light intensity, dim vs. bright, in women adhering to a standardized routine in the absence of thermal stress. These findings are discussed in terms of inhibition of the sympathetic and excitation of the parasympathetic nervous system under the influence of life-style regularity and daytime bright light exposure.

Can we improve neurological outcomes in severe traumatic brain injury? Something old (early prophylactic hypothermia) and something new (erythropoietin)

Traumatic brain injury is a leading cause of mortality and long-term morbidity, particularly affecting young people. With our best therapies, one half of the patients with severe traumatic brain injury are never capable of living independently. Two interventions, which have real potential to improve neurological outcomes in patients with traumatic brain injury, are (i) very early induction of prophylactic hypothermia and (ii) exogenous erythropoietin therapy. There is substantial experimental evidence, a plausible biological rationale, and supportive clinical evidence from clinical trials to suggest a possible beneficial effect of prophylactic hypothermia and also for exogenous erythropoietin therapy in severe traumatic brain injury. Despite the recent guidelines and publications recommending these interventions, critical care clinicians should be conservative towards implementing these therapies outside clinical trials due to substantial efficacy and safety concerns. Nevertheless the high morbidity and mortality associated with severe traumatic brain injury (TBI) demands that we investigate the safety and efficacy of these promising potential therapies as a matter of urgency.

Moderate hypothermia as a rescue therapy against intestinal ischemia and reperfusion injury in the rat

OBJECTIVE

Moderate hypothermia is protective when applied throughout experimental intestinal ischemia and reperfusion (I/R). However, therapeutic intervention is usually possible only after ischemia has occurred. The aim of this study was to evaluate moderate hypothermia when applied at reperfusion as a rescue therapy for intestinal I/R.

DESIGN

Prospective, randomized, controlled experiment.

SETTING

University research laboratory.

SUBJECTS

Adult male Sprague-Dawley rats (240-300 g).

INTERVENTIONS

In experiment I, rats underwent 60 mins of normothermic intestinal ischemia (36-38 degrees C) plus 300 mins of reperfusion at either normothermia or moderate hypothermia (30-32 degrees C) with or without rewarming. Hemodynamics were measured invasively and survival was assessed. In experiment II, rats underwent 60 mins of normothermic ischemia plus 120 mins of reperfusion at either normothermia or moderate hypothermia. At kill, organs and a blood sample were collected.

MEASUREMENTS AND MAIN RESULTS

In experiment I, all normothermic I/R rats died within 197 mins of reperfusion after developing severe tachycardia and hypotension, whereas hypothermic rats, with or without rewarming, were alive at 300 mins of reperfusion (p < .001 vs. I/R normothermia) and were hemodynamically stable. In experiment II, normothermic reperfusion caused histologic and biochemical damage to the gut, hepatic energy failure, and inflammatory infiltration of the lung. However, hypothermia reduced injury to the reperfused ileum and prevented distant organ injury by counteracting energy failure in the liver, systemic overproduction of nitric oxide, altered cardiac fatty acid metabolism, and infiltration of inflammatory cells in the lungs.

CONCLUSIONS

Hypothermia applied as a rescue therapy for intestinal I/R abolishes mortality even after rewarming. Hypothermic protection during early reperfusion appears to be mediated by several pathways, including prevention of intestinal and pulmonary neutrophil infiltration, reduction of oxidative stress in the ileum, and preservation of cardiac and hepatic energy metabolism. Moderate hypothermia may improve outcome in clinical conditions associated with intestinal I/R.

Short-term heat exposure inhibits inflammation by abrogating recruitment of and nuclear factor-{kappa}B activation in neutrophils exposed to chemotactic cytokines

Cytokines, such as granulocyte macrophage-colony stimulating factor (GM-CSF) and interleukin (IL)-8 attract neutrophils into inflammatory sites. During emigration from the blood neutrophils interact with extracellular matrix proteins such as fibronectin. Fibronectin provides beta2-integrin co-stimulation, allowing GM-CSF and IL-8 to activate nuclear factor (NF)-kappaB, an effect that does not occur in suspension. We tested the hypothesis that exposure of mice to fever-like temperatures abrogates neutrophil recruitment and NF-kappaB activation in a mouse model of skin inflammation. Mice that were exposed to 40 degrees C for 1 hour showed strongly reduced GM-CSF- and IL-8-induced neutrophilic skin inflammation. In vitro heat exposure did not interfere with neutrophil adhesion or spreading on fibronectin but strongly inhibited migration toward both cytokines. Using specific inhibitors, we found that PI3-K/Akt was pivotal for neutrophil migration and that heat down-regulated this pathway. Furthermore, neutrophils on fibronectin showed abrogated NF-kappaB activation in response to GM-CSF and IL-8 after heat. In vivo heat exposure of mice followed by ex vivo stimulation of isolated bone marrow neutrophils confirmed these results. Finally, less NF-kappaB activation was seen in the inflammatory lesions of mice exposed to fever-like temperatures as demonstrated by in situ hybridization for IkappaBalpha mRNA. These new findings suggest that heat may have anti-inflammatory effects in neutrophil-dependent inflammation.

A review of current strategies to reduce intraoperative bacterial contamination of surgical wounds

Surgical site infections are a mean topic in cardiac surgery, leading to a prolonged hospitalization, and substantially increased morbidity and mortality. One source of pathogens is the endogenous flora of the patient's skin, which can contaminate the surgical site. A number of preoperative skin care strategies are performed to reduce bacterial contamination like preoperative antiseptic showering, hair removal, antisepsis of the skin, adhesive barrier drapes, and antimicrobial prophylaxis. Furthermore we can also support the natural host defense by optimal intra-operative management of oxygen supply, normoglycemia, and temperature. Nevertheless we still have a number of patients, who develop a surgical site infection. Therefore new skin care strategies are introduced to reduce the contamination by the endogenous skin flora. We present the use of a new microbial sealant, InteguSeal((R)), which was evaluated in patients undergoing cardiac surgery. The preliminary results of this investigation showed a trend in surgical site infection reduction by the use of this new microbial sealant.

Perioperative Hypothermie

Mild perioperative hypothermia is a common complication of anesthesia and surgery associated with several adverse effects including impaired wound healing and more frequently leads to wound infections. Perioperative hypothermia affects the hemostasis and various immune functions and therefore interferes with the initial phases of the wound healing process. Furthermore, perioperative hypothermia contributes to wound complications by inhibition of deposition of collagen and prolongation of postoperative catabolism. Wound complications prolong hospitalization and substantially increase medical costs. Thus, maintaining normothermia perioperatively is essential to reduce the number of wound complications.

The impact of long-term haemofiltration (continuous veno-venous haemofiltration) on cell-mediated immunity during endotoxaemia

BACKGROUND

Increased survival with high-volume continuous veno-venous haemofiltration (CVVH) has been demonstrated in critically ill patients. This may be the result of intensified blood purification or an effect on the immune system. We hypothesized that CVVH modifies the cell-mediated immunity. We investigated the effect of high-volume CVVH for 24 h on the cell-mediated immunity following endotoxin infusion.

METHODS

Thirty pigs were divided into three groups. Ten pigs received 30 microg/kg of Escherichia coli endotoxin. These pigs were treated with CVVH (replacement 35 ml/kg/h) over the following 24 h. Ten pigs received the same bolus of endotoxin and ten pigs served as a control group. The adhesion molecules CD18, CD44 and CD62L and the ability to respond with an oxidative burst were measured. The number of neutrophils was counted in blood and lung tissue. The lymphoproliferative response and cytokines interleukin-6 and interleukin-10 were measured.

RESULTS

The infusion of endotoxin was followed by initial granulocytopenia and, later, granulocytosis, activation of CD18 and CD62L, and increased oxidative burst. The cytokine level was increased. CVVH had no effect on the adhesion molecules or cytokine level and did not reduce the number of granulocytes in the lung significantly. CVVH, however, reduced the oxidative burst activity of neutrophils after 2 h of treatment.

CONCLUSION

In the first few hours after endotoxaemia, high-volume CVVH reduced the oxidative burst activity of neutrophils. However, in the long term, CVVH was unable to modify the endotoxin-induced changes in cell-mediated immunity.

The effects of hypothermia on endotoxin-primed lung

BACKGROUND

Hypothermia may be effective for endotoxin-induced acute lung injury. In most studies, hypothermia was induced before the development of neutrophilic inflammation, which would be clinically irrelevant. We investigated whether hypothermia induced after the onset of such neutrophilic inflammation reduces acute lung injury.

METHODS

In the first experiment, rats were allocated to one of four groups: intratracheal saline instillation/killed at 1 h (saline), intratracheal lipopolysaccharide (LPS) instillation/killed at 1 h (LPS-primed), intratracheal LPS instillation/killed at 6 h (LPS-NT), all under normothermia (NT) (37 +/- 0.5 degrees C) throughout study, and intratracheal LPS instillation/killed at 6 h with hypothermia (HT) (32 +/- 0.5 degrees C) for the last 5 h of study (LPS-HT). Lungs were lavaged for biochemical measurements. In the second experiment in 26 additional rats, we followed exactly the same protocol as described above for the saline group (n = 2), LPS-NT (n = 12), and LPS-HT (n = 12), and obtained a fresh pool of alveolar neutrophils to assess oxidative burst.

RESULTS

Compared with the LPS-primed group, the neutrophil count, protein level, and lactate dehydrogenase activity in the bronchoalveolar lavage fluid, and myeloperoxidase activity of the lung were all higher in the LPS-NT group. Compared with this LPS-NT group, the neutrophil count, protein level, and lactate dehydrogenase activity in the bronchoalveolar lavage fluid, and microscopic scores for alveolar neutrophilic infiltration were all lower in the LPS-HT group. The stimulated production of hydrogen peroxide in neutrophils was lower in the LPS-HT group than in the LPS-NT group.

CONCLUSION

Hypothermia, applied even after the onset of neutrophilic inflammation, was effective in reducing endotoxin-induced acute lung injury.

Non-pharmacologic Prevention of Surgical Wound Infection

Surgical site infections are among the most common serious perioperative complications. Infections are established during a decisive period that lasts a few hours after contamination. Adequacy of host immune defenses is the primary factor that determines whether inevitably wound contamination progresses into a clinical infection. As it turns out, many determinants of infection risk are under the direct control of anesthesiologists; factors that are at least as important as prophylactic antibiotics. Major outcome studies demonstrate that the risk of surgical wound infection is reduced threefold simply by keeping patients normothermic. Infection risk is reduced by an additional factor of two by if supplemental oxygen is provided (80% versus 30%) during surgery and for the initial hours after surgery. The contribution, if any, of other factors including, tight glucose control, fluid management, and mild hypercapnia have yet to be suitably tested.

Exercising in Environmental Extremes

Athletes, military personnel, fire fighters, mountaineers and astronauts may be required to perform in environmental extremes (e.g. heat, cold, high altitude and microgravity). Exercising in hot versus thermoneutral conditions (where core temperature is > or = 1 degrees C higher in hot conditions) augments circulating stress hormones, catecholamines and cytokines with associated increases in circulating leukocytes. Studies that have clamped the rise in core temperature during exercise (by exercising in cool water) demonstrate a large contribution of the rise in core temperature in the leukocytosis and cytokinaemia of exercise. However, with the exception of lowered stimulated lymphocyte responses after exercise in the heat, and in exertional heat illness patients (core temperature > 40 degrees C), recent laboratory studies show a limited effect of exercise in the heat on neutrophil function, monocyte function, natural killer cell activity and mucosal immunity. Therefore, most of the available evidence does not support the contention that exercising in the heat poses a greater threat to immune function (vs thermoneutral conditions). From a critical standpoint, due to ethical committee restrictions, most laboratory studies have evoked modest core temperature responses (< 39 degrees C). Given that core temperature during exercise in the field often exceeds levels associated with fever and hyperthermia (approximately 39.5 degrees C) field studies may provide an opportunity to determine the effects of severe heat stress on immunity. Field studies may also provide insight into the possible involvement of immune modulation in the aetiology of exertional heat stroke (core temperature > 40.6 degrees C) and identify the effects of acclimatisation on neuroendocrine and immune responses to exercise-heat stress. Laboratory studies can provide useful information by, for example, applying the thermal clamp model to examine the involvement of the rise in core temperature in the functional immune modifications associated with prolonged exercise. Studies investigating the effects of cold, high altitude and microgravity on immunity and infection incidence are often hindered by extraneous stressors (e.g. isolation). Nevertheless, the available evidence does not support the popular belief that short- or long-term cold exposure, with or without exercise, suppresses immunity and increases infection incidence. In fact, controlled laboratory studies indicate immuno-stimulatory effects of cold exposure. Although some evidence shows that ascent to high altitude increases infection incidence, clear conclusions are difficult to make because of some overlap with the symptoms of acute mountain sickness. Studies have reported suppressed cell-mediated immunity in mountaineers at high altitude and in astronauts after re-entering the normal gravity environment; however, the impact of this finding on resistance to infection remains unclear.

Moderate hypothermia therapy for acute liver failure in rats before liver transplantation

AIM: To observe the effect of moderate hypothermia on the donated livers in rats with acute liver failure (ALF) before liver transplantation.

METHODS: ALF rats model were established by hepatectomy and hepatic devascularization. In situ liver transplantations were carried out for hypothermia treated group (35.0ºC) and the control group (37.5ºC) 12 h after the transplantation. Blood and tissue samples were collected just before and 6 or 24 h after transplantation. The concentrations of TNF-α were compared before and after the transplantation. The content of malondialdehyde (MDA) and the apoptotic rate of hepatic cells after the transplantation were observed. The apoptotic rate and MDA contents in donated liver were also assayed. The morphological changes of liver tissues were observed under microscope.

RESULTS: In the hypothermia treated group, the concentrations of TNF-α before and after the transplantation were significantly lower than those in the control group (19.3±5.9 vs 43.4±9.0 µg/L, t= 5.008, P = 0.007; 6 h, 97.7±18.3 vs 137.1±23.3 µg/L, t = 9.471, P = 0.001); the MDA contents and apoptotic rate after transplantation were also significantly lower than those in the control group (407.1±49.4 vs 598.2±61.8 nmol/L, t = 34.46, P = 0.001; 18.3±3.9% vs 23.6±4.3%, t = 29.63, P = 0.001).

CONCLUSION: Moderate hypothermia can decrease TNF-α level and relieve the damages of the donated liver in rats with ALF.

Oxidative stress and electron spin resonance

The body constantly reacts with oxygen as part of the energy producing processes of cells. Oxidative stress is a dysbalance between the production of free radicals as products of these reactions and antioxidant properties of cells. The factors influencing the production of free radicals are physical agents, chemical agents and biological agents. Free radicals are paramagnetic molecules with short time-period for their detection by electron spin resonance (ESR) spectroscopy. The free radical stabilization can be gained by freezing a solution of an organic radical or bonding to spin trapping agents. The spin trapping agents are diamagnetic compounds which rapidly scavenge transient radicals to form stable paramagnetic spin adducts radicals. Because this secondary radical retains an unpaired electron, it can often be detected by electron spin resonance. From ESR spectra can be obtained structural information and kinetic information, information about the formation and decay of the radicals. To study the process of free radical generation is an important step towards reducing the deteriorating effects of oxidative stress.

[Preoperative evaluation and perioperative management of patients with increased cardiovascular risk]

Due to the increasing age in western countries, combined with high rates of major surgical interventions in high-risk patients, perioperative reduction of cardiovascular complications becomes increasingly more important for perioperative physicians. After identifying patients with increased perioperative risk, specific interventions need to be considered to reduce their risk for cardiovascular complications, either by perioperative medical therapy or specific treatment options (e.g. coronary intervention). Several trials have demonstrated an effect of perioperative beta-blocker-therapy in reducing cardiovascular complications among high-risk patients. Additionally, several monitoring techniques are effective in detecting cardiovascular complications. Nevertheless, it remains unclear whether they are associated with a measurable improvement of outcome. Based on the ACC/AHA-guidelines, the present review describes a stepwise approach to surgical patients to identify perioperative risks, based on specific patient related risk factors, the kind of surgery and on the specific setting (emergency versus elective surgery). In addition, strategies to reduce perioperative cardiovascular complications are discussed.