Effect of Induced Mild Hypothermia on Acid-Base Balance During Experimental Acute Sepsis in Rats

Association between the severity of hypothermia and in-hospital mortality in patients with infectious diseases: The J-Point registry

Aim

Hypothermia is associated with poor prognosis in patients with sepsis. However, no studies have explored the correlation between the severity of hypothermia and prognosis.

Methods

Using data from the Japanese accidental hypothermia network registry (J-Point registry), we examined adult patients aged ≥18 years with infectious diseases whose initial body temperature was ≤35°C from April 1, 2011 to March 31, 2016, in 12 centers. Patients were divided into three groups according to their body temperature: Tertile 1 (T1) (32.0-35.0°C), Tertile 2 (T2) (28.0-31.9°C), and Tertile 3 (T3) (<28.0°C). In-hospital mortality was employed as a metric to assess outcomes. We conducted a multivariate logistic regression analysis to investigate the relationship between the three categories and the occurrence of in-hospital mortality.

Results

A total of 572 patients were registered, and 170 eligible patients were identified. Of these patients, 55 were in T1 (32.0-35.0°C), 76 in T2 (28.0-31.9°C), and 39 in T3 (<28.0°C) groups. The overall in-hospital mortality rate in accidental hypothermia (AH) patients with infectious diseases was 34.1%. The in-hospital mortality rates in the T1, T2, and T3 groups were 34.5%, 36.8%, and 28.2%, respectively. The multivariable analysis demonstrated no significant differences regarding in-hospital mortality among the three groups (T2 vs. T1, adjusted odds ratio [OR]: 1.29; 95% confidence interval [CI]: 0.58-2.89 and T3 vs. T1, adjusted OR: 0.83; 95% CI: 0.30-2.31).

Conclusion

In this multicenter retrospective observational study, hypothermia severity was not associated with in-hospital mortality in AH patients with infectious diseases.

Mild Hypothermia Alleviates CLP-induced Multiple Organ Dysfunction by Mitigating Pyroptosis Through the TLR4/NF-κB/NLRP3 Signaling Pathway

BACKGROUND

Multiple organ failure secondary to severe sepsis leads to increased morbidity and mortality and is often accompanied by inflammation and immune system dysfunction. Mild hypothermia has been shown to have anti-inflammatory properties, but whether it can exert a protective effect in cases of multiple organ failure remains unclear. Thus, in this study, we investigated the protective effect of mild hypothermia on septic multiple organ failure and the underlying mechanism for this effect.

METHOD

Sepsis was induced through the cecal ligation and puncture (CLP) method. Rats were then housed at normal (36-38°C) or mild hypothermic (32-34°C) temperature for 10 h.

RESULTS

CLP-induced effects on inflammatory cytokines and biochemical markers in serum were reversed by mild hypothermia. The pathological injury score and the expressions of pyroptosis markers, including TLR4, MyD88 and NF-κB signaling molecules, showed a similar trend. Moreover, 3 d survival of CLP rats was improved by mild hypothermia.

CONCLUSIONS

Mild hypothermia alleviated CLP-induced organ failure and the downstream effects on pyroptosis, probably through the TLR4/NF-κB/NLRP3 signaling pathway.

A low direct electrical signal attenuates oxidative stress and inflammation in septic rats

Electrical stimulation is proposed to exert an antimicrobial effect according to studies performed using bacterial and cell cultures. Therefore, we investigated the effects of electrification on inflammation in septic rats. Twenty-eight male Wistar albino rats were divided into 4 groups: healthy control (C), electrified healthy (E), sepsis (S), and electrified sepsis (SE) groups. Staphylococcus aureus (1 x 109 colonies) in 1 ml of medium was intraperitoneally injected into rats to produce a sepsis model. The rats in the E and SE groups were exposed to a low direct electrical signal (300 Hz and 2.5 volts) for 40 min and 1 and 6 h after bacterial infection. Immediately after the second electrical signal application, blood and tissue samples of the heart, lung, and liver were collected. An antibacterial effect of a low direct electrical signal was observed in the blood of rats. The effects of electrical signals on ameliorating changes in the histological structure of tissues, blood pH, gases, viscosity and cell count, activities of some important enzymes, oxidative stress parameters, inflammation and tissue apoptosis were observed in the SE group compared to the S group. Low direct electrical signal application exerts antibacterial, antioxidant, anti-inflammatory and antiapoptotic effects on septic rats due to the induction of electrolysis in body fluids without producing any tissue damage.

Slow as Compared to Rapid Rewarming After Mild Hypothermia Improves Survival in Experimental Shock

BACKGROUND

Accidental hypothermia following trauma is an independent risk factor for mortality. However, in most experimental studies, hypothermia clearly improves outcome. We hypothesized that slow rewarming is beneficial over rapid rewarming following mild hypothermia in a rodent model of hemorrhagic shock.

MATERIALS AND METHODS

We subjected 32 male Wistar rats to severe hemorrhagic shock (25-30 mmHg for 30 min). Rats were assigned to four experimental groups (normothermia, hypothermia, rapid rewarming [RW], and slow RW). During induction of severe shock, all but the normothermia group were cooled to 34°C. After 60 min of shock, rats were resuscitated with Ringer's solution. The two RW groups were rewarmed at differing rates (6°C/h versus 2°C/h).

RESULTS

Slow RW animals exhibit a significantly prolonged survival compared with the rapid RW animals (P < 0.05). Nevertheless, hypothermic animals show a significant survival benefit as compared to all other experimental groups. Whereas seven animals of the hypothermia group survived to the end of the experiment, none of the other animals did (P < 0.001). No significant differences were found regarding acid base status, metabolism, parameters of organ injury, and coagulation.

CONCLUSIONS

The results indicate that even slow RW with 2°C/h may be still too fast in the setting of experimental hemorrhage. Too rapid rewarming may result in a loss of the protective effects of hypothermia. As rewarming is ultimately inevitable in patients with trauma, potential effects of rewarming on patient outcome should be further investigated in clinical studies.

Therapeutic Hypothermia Reduces Oxidative Damage and Alters Antioxidant Defenses after Cardiac Arrest

After cardiac arrest, organ damage consequent to ischemia-reperfusion has been attributed to oxidative stress. Mild therapeutic hypothermia has been applied to reduce this damage, and it may reduce oxidative damage as well. This study aimed to compare oxidative damage and antioxidant defenses in patients treated with controlled normothermia versus mild therapeutic hypothermia during postcardiac arrest syndrome. The sample consisted of 31 patients under controlled normothermia (36°C) and 11 patients treated with 24 h mild therapeutic hypothermia (33°C), victims of in- or out-of-hospital cardiac arrest. Parameters were assessed at 6, 12, 36, and 72 h after cardiac arrest in the central venous blood samples. Hypothermic and normothermic patients had similar S100B levels, a biomarker of brain injury. Xanthine oxidase activity is similar between hypothermic and normothermic patients; however, it decreases posthypothermia treatment. Xanthine oxidase activity is positively correlated with lactate and S100B and inversely correlated with pH, calcium, and sodium levels. Hypothermia reduces malondialdehyde and protein carbonyl levels, markers of oxidative damage. Concomitantly, hypothermia increases the activity of erythrocyte antioxidant enzymes superoxide dismutase, glutathione peroxidase, and glutathione S-transferase while decreasing the activity of serum paraoxonase-1. These findings suggest that mild therapeutic hypothermia reduces oxidative damage and alters antioxidant defenses in postcardiac arrest patients.