Changes in interleukin-10 mRNA expression are predictive for 9-day survival of pigs in an emergency preservation and resuscitation model

Physiological Changes in Subjects Exposed to Accidental Hypothermia: An Update

Background

Accidental hypothermia (AH) is an unintended decrease in body core temperature (BCT) to below 35°C. We present an update on physiological/pathophysiological changes associated with AH and rewarming from hypothermic cardiac arrest (HCA).

Temperature Regulation and Metabolism

Triggered by falling skin temperature, Thyrotropin-Releasing Hormone (TRH) from hypothalamus induces release of Thyroid-Stimulating Hormone (TSH) and Prolactin from pituitary gland anterior lobe that stimulate thyroid generation of triiodothyronine and thyroxine (T4). The latter act together with noradrenaline to induce heat production by binding to adrenergic β3-receptors in fat cells. Exposed to cold, noradrenaline prompts degradation of triglycerides from brown adipose tissue (BAT) into free fatty acids that uncouple metabolism to heat production, rather than generating adenosine triphosphate. If BAT is lacking, AH occurs more readily.

Cardiac Output

Assuming a 7% drop in metabolism per °C, a BCT decrease of 10°C can reduce metabolism by 70% paralleled by a corresponding decline in CO. Consequently, it is possible to maintain adequate oxygen delivery provided correctly performed cardiopulmonary resuscitation (CPR), which might result in approximately 30% of CO generated at normal BCT.

Liver and Coagulation

AH promotes coagulation disturbances following trauma and acidosis by reducing coagulation and platelet functions. Mean prothrombin and partial thromboplastin times might increase by 40–60% in moderate hypothermia. Rewarming might release tissue factor from damaged tissues, that triggers disseminated intravascular coagulation. Hypothermia might inhibit platelet aggregation and coagulation.

Kidneys

Renal blood flow decreases due to vasoconstriction of afferent arterioles, electrolyte and fluid disturbances and increasing blood viscosity. Severely deranged renal function occurs particularly in the presence of rhabdomyolysis induced by severe AH combined with trauma.

Conclusion

Metabolism drops 7% per °C fall in BCT, reducing CO correspondingly. Therefore, it is possible to maintain adequate oxygen delivery after 10°C drop in BCT provided correctly performed CPR. Hypothermia may facilitate rhabdomyolysis in traumatized patients. Victims suspected of HCA should be rewarmed before being pronounced dead. Rewarming avalanche victims of HCA with serum potassium > 12 mmol/L and a burial time >30 min with no air pocket, most probably be futile.

Targeted temperature management in patients with severe heatstroke: Three case reports and treatment recommendations

RATIONALE

Unprecedented heatwaves over the past several years are getting worse with longer duration in the course of global warming. Heatstroke is a medical emergency with multiple organ involvement and life-threatening illness with a high mortality rate of up to 71%. Uncontrolled damage to the central nervous system can result in severe cerebral edema, permanent neurological sequelae, and death. However, regarding the therapeutic aspects of heat stroke, there was no therapeutic strategy after the rapid cooling of the core body temperature to <39°C to prevent further injury.

PATIENT CONCERNS

Each of 3 patients developed a change of mental statuses after the exposure to summer heatwaves or relatively high environmental temperatures with high humidity in the sauna.

DIAGNOSES

The patients were diagnosed with severe heatstroke since they showed cerebral edema and multiple organ dysfunction based on the results from laboratory tests and the findings in brain computed tomography scan.

INTERVENTIONS

The patients underwent induced therapeutic hypothermia (<36°C) between 24 and 36 hours in the management of severe heatstroke.

OUTCOMES

The patients survived from cerebral edema and multiple organ dysfunction.

LESSONS

We believe that targeted temperature management (<36°C) will help treat severe heatstroke. Thus it should be considered for reducing the chance of development of complications in multiple organs, especially in the central nervous system, when managing patients with severe heatstroke.

Immunohistochemical Findings in Idiopathic Inflammatory Bowel Disease in Nine Cats

Inflammatory bowel disease is a term referring to a clinical condition characterized by recurrent/persistent gastrointestinal signs, which cannot be diagnosed only through histological findings, being an elimination diagnosis and needing therefore the previous exclusion of all other possible causes of gastrointestinal signs. The aim of the present study was to compare the expression of different cytokines on endoscopic biopsy samples of the small and large intestine of cats suffering from inflammatory bowel disease and healthy controls, by immunohistochemistry evaluation. Nine cats referred for chronic gastrointestinal signs to the Gastroenterology Service, Teaching Hospital, Faculty of Veterinary Sciences, University of Buenos Aires, were included. After being administered with antiparasitic drugs and after running complete laboratory exams, abdominal ultrasonography, etc., upper and lower gastrointestinal endoscopy with biopsy samplings for histopathology and immunohistochemistry was then performed. Controls were represented by archived samples from healthy cats (University of Camerino, Italy, Veterinary Pathology Unit Archive). On biopsy samples, the immunohistochemistry expression of the following antibodies was evaluated: TGF-β, CD3+, FoxP3+, TNF-α, IL-1β, IL-10, IL-12, and Th-17+. Statistic analysis was performed with the nonparametric Mann-Whitney test and with Spearman test, considering significant $p<0.05$ . TNF-α, IL-1β, IL-12, and CD3+ were significantly differently expressed between cats suffering from inflammatory bowel disease and controls, while no differences were found regarding TGF-β, IL-10, and FOXP3. A positive correlation was also found between proinflammatory cytokines and proinflammatory cytokines plus lymphocytes that were at the same time related to IL-10 and TGF-β. On the other hand, a negative correlation was found between proinflammatory and regulatory cytokines. Our results suggest an imbalance in the immune response which may play a role in the etiopathogenesis of feline inflammatory bowel disease.

Venoarterial Extracorporeal Membrane Oxygenation Increased Immune Function of Spleen and Decreased Reactive Oxygen Species During Post-Resuscitation

We aimed to investigate the effect of venoarterial extracorporeal membrane oxygenation (VA-ECMO) on immune function of the spleen and reactive oxygen species (ROS) during post-resuscitation in a porcine model. After 8 min of untreated ventricular fibrillation and 6 min of basic life support, pigs were randomized into two groups: Group 1 received VA-ECMO and Group 2 received conventional cardiopulmonary resuscitation. After successful return of spontaneous circulation, the hemodynamic status was determined and blood samples were collected at 0, 1, 2, 4, and 6 h. Surviving pigs were euthanized 6 h after return of spontaneous circulation, their spleens were harvested and the T-cells were separated. Then, we investigated immune function parameters of the spleen and ROS levels. VA-ECMO increased the return of spontaneous circulation and 6 h survival rate after return of spontaneous circulation. Compared with the conventional cardiopulmonary resuscitation group, the VA-ECMO group showed increased superoxide dismutase and decreased malondialdehyde and ROS levels. Furthermore, VA-ECMO was associated with a high rate of CD4+ and CD4+/CD8+, high levels of interleukin 2, interferon γ, and interferon γ/interleukin 4, as well as high proliferation of lymphocytes. The apoptotic rate of T-cells was lower in the VA-ECMO group than it was in the conventional cardiopulmonary resuscitation group. VA-ECMO increased immune function of spleen and decreased ROS levels during post-resuscitation. Further research is expected to illustrate whether the differences in immune responses are due to ROS or some other perfusion related effect on spleen.

Reduction of Serious Adverse Events Demanding Study Exclusion in Model Development: Extracorporeal Life Support Resuscitation of Ventricular Fibrillation Cardiac Arrest in Rats

Extracorporeal life support is a promising concept for selected patients in refractory cardiogenic shock and for advanced life support of persistent ventricular fibrillation cardiac arrest. Animal models of ventricular fibrillation cardiac arrest could help to investigate new treatment strategies for successful resuscitation. Associated procedural pitfalls in establishing a rat model of extracorporeal life support resuscitation need to be replaced, refined, reduced, and reported.Anesthetized male Sprague-Dawley rats (350-600 g) (n = 126) underwent cardiac arrest induced with a pacing catheter placed into the right ventricle via a jugular cannula. Rats were resuscitated with extracorporeal life support, mechanical ventilation, defibrillation, and medication. Catheter and cannula explantation was performed if restoration of spontaneous circulation was achieved. All observed serious adverse events (SAEs) occurring in each of the experimental phases were analyzed.Restoration of spontaneous circulation could be achieved in 68 of 126 rats (54%); SAEs were observed in 76 (60%) experiments. Experimental procedures related SAEs were 62 (82%) and avoidable human errors were 14 (18%). The most common serious adverse events were caused by insertion or explantation of the venous bypass cannula and resulted in lethal bleeding, cannula dislocation, or air embolism.Establishing an extracorporeal life support model in rats has confronted us with technical challenges. Even advancements in small animal critical care management over the years delivered by an experienced team and technical modifications were not able to totally avoid such serious adverse events. Replacement, refinement, and reduction reports of serious adverse events demanding study exclusions to avoid animal resources are missing and are presented hereby.

Significant Cytokine mRNA Expression Changes Immediately after Initiation of Cardiopulmonary Resuscitation

Introduction

The purpose of this study was to evaluate immediate immunological changes following cardiopulmonary resuscitation (CPR). mRNA expression levels of selected immunomodulatory cytokines in out-of-hospital cardiac arrest (OHCA) survivors were detected and correlated to clinical parameter.

Methods

OHCA survivors with sustained unconsciousness after return of spontaneous circulation (ROSC) were included. PAXgene whole blood samples were drawn immediately after initiation of CPR and subsequently after 6 h, 12 h, 24 h, 48 h, and 72 h. TNF-alpha, IL-8, IL-10, and IL-1ra mRNA levels were quantified by RT-qPCR and compared to multiple organ failure, 30-day survival, and the induction of therapeutic hypothermia (TH).

Results

25 patients (63 ± 15 years) were enrolled presenting a characteristic time-dependent cytokine profile in the early postresuscitation period. High initial TNF-alpha and IL-8 mRNA levels were followed by a significant decrease. IL-1ra mRNA levels significantly increased beginning after 6 h. Nonsurvivors showed significantly higher IL-8 mRNA levels immediately after CPR. TH induced significantly higher IL-1ra mRNA levels compared to normothermia.

Conclusion

Significant mRNA cytokine expression changes are already detectable immediately after initiation of CPR. These expressional changes are significantly different depending on 30-day survival. TH seems to attenuate proinflammatory immune reaction by a significant increase of IL-1ra mRNA levels. This trial is registered with DRKS00012940.

Blood biochemical changes in pigs after infusion with acetate-buffered or lactate-buffered crystalloid solutions

Perioperative fluid therapy is an important component of many medical procedures with animals. Buffered crystalloid solutions avoid inducing metabolic acidosis, but lactated solutions can elevate blood lactate concentrations and acetated solutions have not been thoroughly investigated using large animals. Here, the authors compare blood biochemical parameters in 20 juvenile pigs after perioperative fluid administration of an acetate-buffered solution (Elo-Mel isoton, EMI) or a lactate-buffered solution (lactated Ringer's solution, LRS). The authors measured blood lactate, glucose and electrolyte concentrations before and after administering the test fluid during surgery. Blood lactate concentration after administration was significantly higher in pigs that received LRS than in pigs that received EMI, but glucose and electrolyte concentrations did not differ significantly between treatment groups before or after administration. These findings suggest that EMI might be a preferable option for perioperative fluid therapy in pigs.

Rapid rewarming after therapeutic hypothermia worsens outcome in sepsis

OBJECTIVE

This study was performed to investigate the effect of the rewarming rate on survival and acute lung injury in sepsis.

METHODS

Male Sprague-Dawley rats underwent cecal ligation and incision. After 1 hour of sepsis induction, normothermia (37°C±0.5°C, NT group) or hypothermia (32°C±0.5°C) was induced. Hypothermia was maintained for 4 hours and rats were divided into two groups according to the rewarming rate: RW1 group, 1 hour of rewarming; and RW2 group, 2 hours of rewarming. In the survival study, rats were observed for 12 hours after sepsis induction (n=6 per group). In the second experiment, rats were sacrificed 7 hours after sepsis induction, and lung tissues and plasma were harvested (n=10 per group).

RESULTS

In the survival study, the RW2 group survived longer than the RW1 group (P<0.05), but the RW1 and NT groups showed no significant difference in survival duration (P>0.05). The histological lung injury score and malondialdehyde concentrations in the lung tissues were significantly higher in the RW1 group than in the RW2 group (P<0.05). Plasma interleukin (IL)-6 concentration and the ratio of IL-6 to IL-10 were higher in the RW1 group than in the RW2 group (P<0.05).

CONCLUSION

Rapid rewarming after therapeutic hypothermia results in a shorter survival period and acute lung injury in sepsis, which could be associated with the inflammatory responses.

Totally thoracoscopic repair of atrial septal defect reduces systemic inflammatory reaction and myocardial damage in initial patients

Background

To compare the effect of totally thoracoscopic with conventional, open repair of atrial septal defect.

Methods

Forty atrial septal defect cases were divided into two groups by surgical approach: totally thoracoscopic approach (group A, n = 20) and conventional open approach (group B, n = 20). In group A, surgical procedures were performed through three portal incisions in the right lateral chest wall under thoracoscopic vision without the aid of a computerized robotic surgical system. Notably, all operations were completed by one surgeon who had just begun using this technique. In group B, the atrial septal defects were repaired in conventional open fashion. Clinical outcomes and serum levels of tumor necrosis factor α (TNF-α), interleukin-6 (IL-6), interleukin-10 (IL-10), intercellular adhesion molecule 1 (ICAM-1), and creatine kinase isoenzyme-myocardial band (CK-MB) for the two groups were evaluated and compared.

Results

All operations were performed successfully without serious complications. Durations of cardiopulmonary bypass (CPB), CPB setup, aortic cross-clamping, and operative procedure were significantly longer in group A than in group B (P < 0.05). The recovery times for body temperature and laboratory values of leukocytes were significantly shorter for group A than for group B (P < 0.05). There were no differences in durations of postoperative assisted ventilation or intensive care unit and hospital stays, volumes of blood transfused intraoperatively or thoracic drainage, or medical costs between the two groups. Serum levels of inflammatory factors (TNF-α, IL-6, IL-10, and ICAM-1) and CK-MB increased significantly in both groups after surgery. However, 6 h and 12 h after surgery, levels of these inflammatory factors and CK-MB were significantly lower in group A than in group B (P < 0.05).

Conclusions

Thoracoscopic cardiac surgery is technically feasible and safe, with less trauma and quicker recovery even when done by a surgeon newly introduced to the technique.

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.

Exploratory reference intervals on hematology and cellular immune system of multiparous Large White sows

There is significant lack of basic hematologic and immunological data in adult sows. Therefore, aim of this study was to provide respective reference intervals. 32 clinically healthy multiparous Large White sows aged 33.5 ± 9.6 months and all of them two months postpartum were included in this study. Mean erythrocyte count was 5.5 ± 0.7 × 10(6)/μl and total leukocyte count was 12.1 ± 2.1 × 10(3)/μl. Proportion of lymphocytes was 44.7 ± 10.2% and of neutrophils 41.6 ± 11.0%. The ratio of naïve T helper (Th) cells to memory Th cells was 1:3.1 and the ratio of Th cells to cytotoxic T cells (CTLs) was 1:4.2. Proportions of regulatory T cells, NK cells, and CD21(+) B cells were lower (3.1, 2.6, and 6.0%) than those of memory Th cells ranging from 8.8 to 27.5% depending on the activation status and CTLs with 37.3%. γδ T cells were found at comparably high numbers (19.1%). Flow cytometric measurement of intracellular cytokines in PBMCs revealed marginal levels for IL-1β, IL-2, IL-4, IL-6, IL-10, and IL-12p35, but remarkable levels for TNF-α and IFN-γ. Highest mRNA levels were found for IL-1, IL-10, and TNF-α, with TNF-α showing the least inter-individual variation.

Minocycline neuroprotection in a rat model of asphyxial cardiac arrest is limited

OBJECTIVE

The study investigated a possible neuroprotective potency of minocycline in an experimental asphyxial cardiac arrest (ACA) rat model. Clinically important survival times were evaluated thus broadening common experimental approaches.

METHODS

Adult rats were subjected to 5 min of ACA followed by resuscitation. There were two main treatment groups: ACA and sham operated. Relating to minocycline treatment each group consisted of three sub-groups: pre-, post-, and sans-mino, with three different survival times: 4, 7, and 21 days. Neurodegeneration and microgliosis were monitored by immunohistochemistry. Alterations of microglia-associated gene expression were analyzed by quantitative RT-PCR.

RESULTS

ACA induced massive nerve cell loss and activation of microglia/macrophages in hippocampal CA1 cell layer intensifying with survival time. After 7 days, minocycline significantly decreased both, neuronal degeneration and microglia response in dependence on the application pattern; application post ACA was most effective. After 21 days, neuroprotective effects of minocycline were lost. ACA significantly induced expression of the microglia-associated factors Ccl2, CD45, Mac-1, F4-80, and Tnfa. Independent on survival time, minocycline affected these parameters not significantly. Expression of iNOS was unaffected by both, ACA and minocycline.

CONCLUSIONS

In adult rat hippocampus microglia was significantly activated by ACA. Minocycline positive affected neuronal survival and microglial response temporary, even when applied up to 18 h after ACA, thus defining a therapeutically-relevant time window. As ACA-induced neuronal cell death involves acute and delayed events, longer minocycline intervention targeting also secondary injury cascades should manifest neuroprotective potency, a question to be answered by further experiments.

Distribution of neuropathological lesions in pig brains after different durations of cardiac arrest

AIM OF THE STUDY

To evaluate all brain regions reported to be selectively vulnerable to global ischaemia in a pig cardiac arrest model with different durations of no-flow by establishing a semi-quantitative brain histopathologic scoring system and to compare histological damage with neurological deficits.

METHODS

In a prospective randomised laboratory investigation, 35 female Large White pigs weighing 35-45 kg underwent ventricular fibrillation cardiac arrest for 0, 7, 10 or 13 min. In the brains of all animals that survived until the final endpoint (72 h post-arrest), 22 distinct regions were evaluated on paraffin-embedded sections in terms of type and extent of lesions. The results of the histological examination were compared to the results of a neurological outcome evaluation after 72 h.

RESULTS

Significant differences were found in all cortex regions, the caudate nucleus and putamen, the hippocampal formation, the cerebellar cortex, and the thalamus between the ischaemic groups (7- and 10-min groups) and the control group (0-min group). No 13-min group animal survived. The main findings were neuronal necrosis and oedema. In animals from the 10-min group, many neurons were reabsorbed in the cerebral cortex, caudate nucleus and cerebellar granule cell layer. There was a highly significant correlation between histological damage and neurological deficits.

CONCLUSIONS

The pattern of neuronal lesions in this pig model bear good resemblance to the pattern known in humans and other animal models. The amount of histological lesions in selectively vulnerable brain regions correlates to neurological outcome.

Does anesthetic provide similar neuroprotection to therapeutic hypothermia after cardiac arrest?

In the previous issue of Critical Care, Meybohm and colleagues provide evidence to support hypothermia as a kind of therapeutic option for patients suffering cardiac arrest. Although anesthetics had been used to induce hypothermia, sevoflurane post-conditioning fails to confer additional anti-inflammatory effects after cardiac arrest. Further research in this area is warranted.