MILD THERAPEUTIC HYPOTHERMIA REDUCES ISCHEMIA-REPERFUSION INJURY AFTER ZONE 1 REBOA IN A SWINE HEMORRHAGIC SHOCK MODEL

ABSTRACT

Background: Resuscitative balloon occlusion of the aorta (REBOA) is an endovascular hemostasis method used for the management of traumatic abdominal and pelvic hemorrhages. However, REBOA-associated ischemia-reperfusion injury complication limits its blocking time. We hypothesized that mild therapeutic hypothermia would relieve ischemia-reperfusion injury caused by prolonged zone 1 REBOA. Methods: Ten pigs were anesthetized, intubated, and subsequently struck with the experimental sliding-chamber ballistic gun to inflict liver damage. Animals were randomized to hypothermia (60 min of zone 1 REBOA with external cooling for 180 min, n = 5) or control (60 min of zone 1 REBOA with no external cooling, n = 5). Physiological and laboratory parameters were monitored and assessed. Distal organs were obtained for histologic analysis. Results: At 180 min, compared with the control, the hypothermia animals exhibited significantly increased pH and significantly reduced lactate, hemoglobin, and hematocrit (all P < 0.05). The change of lactate from 0 to 180 min in hypothermia animals was less than that in the control ( P = 0.02). The total bleeding in the control group was significantly less than the hypothermia ( P < 0.01). In the hypothermia group, prothrombin time at 120 and 180 min was significantly longer than that at baseline (all P < 0.05). Compared with the control, animals in the hypothermia group showed slighter pathological injury of the distal organs and significantly lower overall injury score (all P < 0.05). Conclusions: Mild therapeutic hypothermia during prolonged zone 1 REBOA offered extraordinary distal organ preservation and decreased metabolic acidosis.

Effects of different external cooling placements prior to and during exercise on athletic performance in the heat: A systematic review and meta-analysis

Background: Nowadays, many high-profile international sport events are often held in warm or hot environments, hence, it is inevitable for these elite athletes to be prepared for the challenges from the heat. Owing to internal cooling may cause gastrointestinal discomfort to athletes, external cooling technique seems to be a more applicable method to deal with thermal stress. Central cooling mainly refers to head, face, neck and torso cooling, can help to reduce skin temperature and relieve thermal perception. Peripheral cooling mainly refers to four limbs cooling, can help to mitigate metabolic heat from muscular contrac to effectively prevent the accumulation of body heat. Hence, we performed a meta-analysis to assess the effectiveness of different external cooling placements on athletic performance in the heat Methods: A literatures search was conducted using Web of Science, MEDLINE and SPORTDiscus until September 2022. The quality and risk of bias in the studies were independently assessed by two researchers. Results: 1,430 articles were initially identified (Web of Science = 775; MEDLINE = 358; SPORTDiscus = 271; Additional records identified through other sources = 26), 60 articles (82 experiments) met the inclusion criteria and were included in the final analysis, with overall article quality being deemed moderate. Central cooling (SMD = 0.43, 95% CI 0.27 to 0.58, p < 0.001) was most effective in improving athletic performance in the heat, followed by central and peripheral cooling (SMD = 0.38, 95% CI 0.23 to 0.54, p < 0.001), AND peripheral cooling (SMD = 0.32, 95% CI 0.07 to 0.57, p = 0.013). For the cooling-promotion effects on different sports types, the ranking order in central cooling was ETE (exercise to exhaustion), TT (time-trial), EWT (exercise within the fixed time or sets), IS (intermittent sprint); the ranking order in peripheral cooling was EWT, TT, ETE and IS; the ranking order in central and peripheral cooling was ETE, IS, EWT and TT. Conclusion: Central cooling appears to be an more effective intervention to enhance performance in hot conditions through improvements of skin temperature and thermal sensation, compared to other external cooling strategies. The enhancement effects of peripheral cooling require sufficient re-warming, otherwise it will be trivial. Although, central and peripheral cooling seems to retain advantages from central cooling, as many factors may influence the effects of peripheral cooling to offset the positive effects from central cooling, the question about whether central and peripheral cooling method is better than an isolated cooling technique is still uncertain and needs more researchs to explore it.

Mild Hypothermia via External Cooling Improves Lung Function and Alleviates Pulmonary Inflammatory Response and Damage in Two-Hit Rabbit Model of Acute Lung Injury

OBJECTIVES

Targeted temperature management (TTM) with therapeutic hypothermia (TH) has an organ-protective effect by mainly reducing inflammatory response. Here, our objective was to determine, for the first time, whether mild TH with external cooling, a simple and inexpensive method, could be safe or even beneficial in two-hit rabbit model of acute lung injury/acute respiratory distress syndrome (ALI/ARDS).

METHODS

Twenty-two New Zealand rabbits (6-month-old) were randomly divided into healthy control (HC) with conventional ventilation, but without injury, model group (ALI), and hypothermia group with external cooling (ALI-HT). After induction of ALI/ARDS through mild lung-lavages followed by non-protective ventilation, mild hypothermia was started in ALI-HT group (body temperature of 33-34 °C). All rabbits were conventionally ventilated for an additional 6-h by recording respiratory parameters. Finally, lung histopathology and inflammatory response were evaluated.

RESULTS

Hypothermia was associated with higher oxygen saturation, resulting in partial improvement in the P/F ratio (PaO2/FiO2), oxygenation index, mean airway pressure, and PaCO2, but did not affect lactate levels. The ALI-HT group had lower histopathological injury scores (hyperemia, edema, emphysema, atelectasis, and PMN infiltration). Further, tumor necrosis factor-alpha (TNF-α), interleukin (IL)-6 and -8 levels in lung tissue and serum samples markedly reduced due to hypothermia.

CONCLUSION

Mild TH with external cooling reduced lung inflammation and damage, whereas it resulted in partial improvement in gas exchanges. Our findings highlight that body temperature control may be a potentially supportive therapeutic option for regulating cytokine production and respiratory parameters in ALI/ARDS.