a b s t r a c t

Background: Continuous renal replacement therapy was currently demonstrated to be an effective way to induce fast hypothermia and had proective effects on cardiac dysfunction and brain damage after cardiac pulmo- nary resuscitation (CPR). In the present study, we aimed to investigate the influence of extracorporeal circuit cooling using CRRT on renal and intestinal damage after CPR based on a porcine model.

Methods: 32 pigs were subjected to ventricular fibrillation for 8 min, followed by CPR for 5 min before defibrilla- tion. All were randomized to receive extracorporeal circuit cooling using CRRT (CRRT, n = 9), Surface cooling (SC, n = 9), normothermia (NT, n = 9) or sham control (n = 5) at 5 min post resuscitation. Pigs in the CRRT group were cooled by 8-h CRRT cooling with the infusion line initially submerged in 4 ?C of ice water and 16-h SC, while in the SC group by a 24-h SC. Temperatures were maintained at a normal range in the other two groups. Bio- markers in serum were measured at baseline and 1, 3, 6, 12, 24 and 30 h post resuscitation to assess organ func- tions. Additionally, tissues of kidney and intestine were harvested, from which the degree of tissue inflammation, oxidative stress, and apoptosis levels were analyzed.

Results: The blood temperature decreased faster by extracorporeal circuit cooling using CRRT than SC (9.8 +- 1.6 vs. 1.5 +- 0.4 ?C/h, P < 0.01). Post-resuscitation renal and intestinal injury were significantly improved in the 2 hypothermic groups compared to the NT group. And the improvement was significantly greater in animals re- ceived extracorporeal circuit cooling than those received surface cooling, from both the results of biomarkers in serum and pathological evidence.

Conclusion: Fast hypothermia induced by extracorporeal circuit cooling was superior to. surface cooling in mitigating renal and intestinal injury post resuscitation.

(C) 2021 Published by Elsevier Inc.

Abbreviation: AKI, Acute kidney injury; BUN, Blood urea nitrogen; CA, Cardiac arrest; CPP, Coronary perfusion pressure; CPR, Cardiac pulmonary resuscitation; Cr, Creatinine; CRRT, Continuous renal replacement therapy; DAO, Diamine oxidase; ELISA, Enzyme- linked immunosorbent assay kits; ETCO2, End-tidal carbon dioxide; IFABP, Intestinal fatty acid binding protein; IL-6, Interleukin-6; I/R, Ischemia-reperfusion; KDIGO, Kidney Disease Improving Global; MDA, Malondialdehyde; NT, Normothermia; PCAS, Post- cardiac arrest syndrome; ROSC, return of spontaneous circulation; SC, Surface cooling; SD, Standard deviation; SOD, superoxide dismutase; TH, Therapeutic hypothermia; TNF- ?, Tumor necrosis factor-?; TUNEL, Terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling; VF, Ventricular fibrillation.

* Corresponding author at: Hangzhou emergency medical center of Zhejiang Province,

NO.568 Mingshi road, Hangzhou 310021, China.

E-mail addresses: [email protected] (L. Shi), [email protected] (J. Xu), [email protected] (M. Zhang), [email protected] (J. Zhang).

¹ Jiangang Wang, Lin Shi contributed equally to this work, and should be regarded as co-

first authors.

1. Introduction

High rates of morbidity and mortality are observed in resuscitated patients undergone cardiac arrest , largely because of the post cardiac arrest syndrome (PACS), which include Anoxic brain injury, post-cardiac arrest myocardial dysfunction, systemic ischemia/reper- fusion (I/R) response occurring in multiple organs and the precipitat- ing pathology [1]. Several attempts have been made to mitigate the heart and brain injury after resuscitation, yet multiple organ dysfunc- tion due to the I/R, such as renal and intestinal injury, cannot be ig- nored. In fact, almost 50% of CA survivors suffer Acute kidney injury [2], which is an independent risk factor for worse neurological outcome and survival [2-4]. And the sensitivity to ischemia of the Small intestine is equal to or even more than that of the brain after

https://doi.org/10.1016/j.ajem.2021.04.057 0735-6757/(C) 2021 Published by Elsevier Inc.

resuscitation [5]. The I/R injury in the intestine increases intestinal permeability and thus, contributes to the Bacterial translocation, the subsequent emergence of sepsis [6], further increasing the chance of developing Multiple organ dysfunction.

Therapeutic hypothermia has been a main intervention of post- resuscitation care, as recommended in international Resuscitation guidelines [7]. Previous studies demonstrated that TH after resuscitation had a protective effect against the recovery of AKI, accompanied by lower levels of creatinine (Cr) and cystatin C [8,9]. TH alone or in the combination with sevoflurane or ulinastatin could mitigate the intesti- nal injury after cardiac arrest [10,11] with decreased levels of Malondialdehyde and increased levels of Superoxide dismutase . Nevertheless, more than 50% of CA survivors treated with TH die or have poor neurological outcome [12-14]. A review demonstrated that rapid cooling with a Cooling rate of >3 ?C/h exerted a higher rate of good neurological outcome than slower cooling methods [15]. There- fore, the undesirable outcome of TH may be deprived from the unsatis- factory cooling effects of Traditional methods, which usually take several hours to decrease the body temperature [16].

Recently, based on our previous research, extracorporeal circuit cooling using continuous renal replacement therapy (CRRT) can also be used as an effective cooling method. Our team have demonstrated that extracorporeal circuit cooling could achieve faster hypothermia than the traditional method, and had protective effects in systemic in- flammation, heart and brain injury after resuscitation in a porcine model [17]. However, the influence of hypothermia induced by extra- corporeal circuit cooling using CRRT on renal and intestinal dysfunction haven’t been determined. The aim of this research was to investigate the influence of extracorporeal circuit cooling on renal and intestinal injury following CPR in swine, to provide more evidence for applying such a technique into resuscitation.

1. Methods

This study was a randomized, controlled laboratory experiment based on a pig model of cardiac arrest. All the experimental procedures were performed based on the methods of our one previous study, in which the animal model has been well established [18]. Ethics commit- tee approval was obtained from the Second Affiliated Hospital, Zhejiang University School of Medicine (No. 2019004). The study included 32 healthy male domestic pigs purchased from same vendor (Shanghai Jiagan Biotechnology Inc., Shanghai, China), weighting 36 +- 2 kg. The pigs were housed under controlled pressure, temperature, humidity and lighting conditions. They were given water and food regularly, washed regularly and disinfected in closed cages. All pigs received care based on the Principles of Laboratory Animal Care and the Guide for the Care and Use of Laboratory Animals.

• 1. Animal preparation

The night before the experiment food was withdrawn from all ani- mals, but they were available to water intake. Induction of anesthesia in pigs was achieved by a combination of Intramuscular ketamine in- jection at 20 mg/kg and sodium pentobarbital injection at 30 mg/kg in an ear vein. Then, to maintain the anesthesia, sodium pentobarbital at 8 mg/kg/h as well as fentanyl at 2 mg/kg/h were given intravenously. Ventilation was maintained using a volume-controlled ventilator (SynoVent E5, Mindray, Shenzhen, China) with the following setting: tidal volume, 12 mL/kg; peak flow, 40 L/min and FiO₂, 21%. End-tidal carbon dioxide (ETCO₂) was measured using an ETCO₂/SPO₂ monitor (PMSH-300, SunLife Science Inc., Shanghai, China), maintaining at 35 mmHg ~ 40 mmHg by respiratory frequency. The standard lead II electrocardiogram surface electrode was secured.

A double-lumen catheter (11 F, Gambro Kathetertechnik Hechingen, Hechingen, Germany) was placed into the left femoral vein to establish vascular access of CRRT. A fluid-filled catheter (8 Fr, C.R. Bard Inc., Salt

Lake, UT) was placed via the right femoral artery to the thoracic artery to measure aortic pressure. A thermodilution catheter (7 Fr, Abbott Crit- ical Care # 41216, Chicago, IL) was placed via right femoral vein to the right atrium to monitor right atrial pressure and blood temperature. In- termittent heparinized saline flushes were made to avoid clogging of the catheters. A pacing catheter (5 F, EP Technologies Inc., Mountain View, CA) was placed via the right external jugular vein to the right ven- tricle to induce ventricular fibrillation (VF). Animals were placed supine on a heating blanket to maintain the normal temperature at 38.0 +-

0.5 ?C.

• 1. Experimental protocol

Baseline characteristics were recorded after a 10-min stabilization. Pigs were randomly allocated to 1 of 4 groups: normothermia (NT, n = 9), surface cooling (SC, n = 9), CRRT cooling (CRRT, n = 9), or sham control (Control, n = 5). Pigs in the NT and Control groups had the body temper- ature maintained at 38.0 +- 0.5 ?C using the Blanketrol III (Cincinnati Sub- Zero, Cincinnati, OH). For pigs in the other 2 groups, TH was started at 5 min after CPR, and then maintained at the temperature of 33 +- 0.5 ?C. The hypothermia induced in the CRRT group was achieved by 8-h CRRT, using an AN69ST hemofilter (Gambro Industries Inc., Meyzieu, France), followed by 16-h SC; while the cooling in the SC group was achieved by 24-h SC with the Blanketrol III. Then, a 1 ?C/h rate of rewarming were followed.

For the CRRT group, a 180 ml/min rate of the blood flow was deter- mined initially, immersing the circuit in 4 ?C ice water until the target temperature of 33 ?C arrived. Then, the temperature was maintained and the blood flow reduced by 60 mL/min. The rates of liquid replace- ment and ultrafiltration were 30 mL/kg/h and 20 mL/kg/h, respectively. Immediately when CRRT started, a load dose of 1000-IU heparin was given for anticoagulation, followed by a dose of 150 IU, 300 IU, 450 IU for the first 3 h, respectively, and 600 IU/h for the rest 5 h.

For Control group, animals did not undergo CA and resuscitation but only experienced animal preparation. In the other three groups, we in- duced VF by delivering alternating current of 1 mA. Anesthesia and ven- tilation were disconnected, and the animals underwent an 8-min period of untreated VF. Then, Cardiac pulmonary resuscitation was started, with a ratio of 30: 2 of compression to ventilation. The chest compressions were achieved at a rate of 100-120/min (reaching 50-60 mm deep) by a monitor defibrillator (ZOLL Medical Inc., Chelms- ford, MA). A dose of 20 mg/kg epinephrine was administered at 2.5 min during resuscitation. Biphasic defibrillation at 150 J was performed at 5 min of CPR. ROSC was determined as an organized rhythm and mean arterial pressure of >50 mmHg sustaining for >5 min. If not achieved, CPR was held on for another 2 min prior to the next defibril- lation. This cycle was duplicated every 2 min, and administration of epi- nephrine was carried out every 3 min until successful ROSC or 15 min had elapsed. If achieved, 30-h mechanical ventilation and infusion of normal saline were subsequently continued to keep fluid balance. After completion of the study, euthanasia and a following necropsy were executed to confirm potential injuries of thoracic or abdominal viscera due to experimental intervention. The experimental flow dia- gram was shown in Fig. 1.

• 1. Measurements

Blood samples of veins and arteries were collected at 1, 3, 6, 12, 24, and 30 h post resuscitation. Then the researchers separated serums from venous blood samples and stored them at -80 ?C prior to further analyzing the levels of creatinine (Cr), Blood urea nitrogen , intes- tinal fatty acid binding protein (IFABP) and diamine oxidase (DAO). To evaluate the inflammatory response and oxidative stress, kidney and in- testine tissues from renal parenchyma and middle part of small intestine were harvested immediately after euthanasia, and subsequently frozen in liquid nitrogen prior to analysis. Levels of tumor necrosis factor-?

Fig. 1. Experimental procedures. CPR indicates cardiac pulmonary resuscitation; CRRT, continuous renal replacement therapy; PR, post resuscitation; SC, surface cooling; VF, ventricular

fibrillation.

(TNF-?), interleukin-6 (IL-6) were analyzed using enzyme- linked immunosorbent assay kits (ELISA, Meixuan Biotechnology Inc., Shanghai, China). The contents of malondialdehyde were mea- sured by thiobarbitUric acid reactive substances assay, and activities of superoxide dismutase (SOD) were measured by xanthine oxide assay [19](Nanjing Jiancheng Bioengineering Institute, Nanjing, China).

The extent of apoptosis of the kidney and intestine were measured using terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL) assay. The proportion of apoptotic cells was determined as the percentage of TUNEL-positive cells/total cells, and the cleaved caspase-3 protein was detected using immunohistochemis- try. The staining intensity of cleaved caspase-3-positive undergone Semiquantitative analysis through integrated optical density based on a previous study [20] with Image-Pro Plus 6.0 software (Media Cyber- netics, Silver Spring, MD).

• 1. Statistical analysis

Continuous variables were described as mean +- standard deviation (SD) or median (25th ~ 75th percentiles) for data normally distributed or not. For comparisons among multiple groups, one-way analysis of variance was used for data normally distributed, Kruskal-Wallis test for data not normally distributed. Bonferroni test was used to account for any two group comparisons when the overall comparison was sig- nificant. Categorical data were analyzed using Fisher exact test. A two- sided P value of <0.05 was considered as statistically significant.

1. Results

A total of 32 pigs went through experiments completely, baseline characteristics and chemistries among all groups were mathematically

Fig. 2. Baseline data of all animals. CRRT indicates continuous renal replacement therapy; NT, normothermia; SC, surface cooling.

Fig. 3. Cardiopulmonary resuscitation outcomes of three groups. CPP indicates coronary perfusion pressure; CPR, cardiac pulmonary resuscitation; CRRT, continuous renal replacement therapy cooling; NT, normothermia; SC, surface cooling.

the same (Fig. 2). During CPR period, animals that experienced CA and resuscitation had an even level of CPP. In all three groups, 8/9 animals achieved ROSC, respectively. There was no significant difference as to coronary perfusion pressure , CPR duration, times of defibrillation, epinephrine dosage among 3 groups (Fig. 3). During post resuscitation period, the temperature in the CRRT group decreased significantly faster than in the SC group (9.8 +- 1.6 vs. 1.5 +- 0.4 ?C/h, P < 0.01, Fig. 4).

During post resuscitation period, the values of creatinine (Cr) showed tendency to descend in two hypothermic groups. At 6 h, 12 h and 24 h after resuscitation, compared to the NT group, the serum levels of Cr were significantly lower in two hypothermic groups, with the lowest in the CRRT group (all P < 0.05). In addition, the levels of blood urea nitrogen (BUN) in all groups increased in the first 24 h-post resus- citation but decreased in the remaining 6 h-rewarming period. Compared to the NT group, the levels of BUN were significantly lower in the two hypothermic groups, with the lowest in the CRRT group at 6 h, 12 h, 24 h and 30 h post resuscitation (all P < 0.05). Conclusively, in the 24 h-post resuscitation period, compared with the SC and NT,

Fig. 4. The changes of blood temperature of three groups. (note: except the control group containing 5 swine, the other groups have 9 swine each). BL indicates baseline; CRRT, continuous renal replacement therapy cooling; NT, normothermia; SC, surface cooling. ^aP < 0.05 versus SC group; ^bP < 0.05 versus NT group; ^cP < 0.05 versus Control group.

Fig. 5. The changes of Cr and BUN in different groups. (note: except the Control group containing 5 swine, the other groups have 9 swine each). BL indicates baseline; BUN, blood urea nitrogen; Cr, creatinine; CRRT, continuous renal replacement therapy; DF, defibrillation; NT, normothermia; PC, precordial compression; SC, surface cooling; VF, ventricular fibrillation. ^aP < 0.05 versus Control group; ^bP < 0.05 versus NT group; ^cP <

0.05 versus SC group.

Fig. 6. The comparisons of tissue inflammation, oxidative stress and cell apoptosis in kidney in different groups. (note: except the Control group containing 5 swine, the other groups have9 swine each). (A) The levels of TNF-? and IL-6; (B) The levels of MDA and the activities of SOD; (C) Representative photomicrographs of TUNEL assay and immunostaining of cleaved caspase-3 protein; (D) The percentage of TUNEL-positive cells and the IOD values of cleaved caspase-3-positive staining. CRRT indicates continuous renal replacement therapy; IL, interleukin; IOD, integrated optical density; MDA, malondialdehyde; NT, normothermia; SC, surface cooling; SOD, superoxide dismutase; TNF, tumor necrosis factor. ^aP < 0.05 versus Control group; ^bP < 0.05 versus NT group; ^cP < 0.05 versus SC group.

the alleviation of renal injury was associated with the cooling induced by CRRT (all P < 0.05, Fig. 5).

In the tissues of kidney, compared with the NT group, the levels of TNF-?, IL-6 were much lower in two hypothermic groups, with the lowest in the CRRT group (all P < 0.05). With regard to the effect on ox- idative stress, the lowest level of MDA and the highest level of SOD were observed in the CRRT group among three experiment groups (P < 0.05).

In the same way, the proportions of apoptotic cells and the expressions of cleaved caspase-3 in the kidney of the two hypothermic groups were lower than the NT group, with the lowest in the CRRT group (P < 0.05). Conclusively, the cooling induced by CRRT was associated with the mit- igated tissue inflammation, suppressed oxidative stress as well as the decreased cell apoptosis in the kidney compared with SC (P < 0.05, Fig. 6).

Fig. 7. The changes of IFABP and DAO in different groups (note: except the control group containing 5 swine, the other groups have 9 swine each). BL indicates baseline; CRRT, continuous renal replacement therapy; DAO, diamine oxidase; DF, defibrillation; IFABP, intestinal fatty acid binding protein; NT, normothermia; PC, precordial compression; SC, surface cooling; VF, ventricular fibrillation. ^aP < 0.05 versus control group; ^bP < 0.05 versus NT group; ^cP < 0.05 versus SC group.

Intestinal status was assessed using the levels of IFABP and DAO. After resuscitation, the values of IFABP increased in the first 24 h and de- creased in the remaining 6 h-rewarming period. At 24 h after resuscita- tion, the serum levels of IFABP were the lowest in CRRT group, followed by the SC group and the NT group (P < 0.05). In addition, the levels of DAO in all groups showed tendency to ascend in the first 12 h post re- suscitation, followed to descend in the remaining 18 h post resuscita- tion. Compared to the NT group, the levels of DAO were significantly lower in two hypothermic groups, with the lowest in the CRRT group at 12 h, 24 h and 30 h post resuscitation (all P < 0.05). Conclusively, in the 24 h-post resuscitation period, compared with the SC and NT, the al- leviation of intestinal injury was associated with the cooling induced by CRRT (all P < 0.05, Fig. 7).

In the tissues of intestine, compared with the NT group, the levels of TNF-?, IL-6 were much lower in the two hypothermic groups, with the lowest in the CRRT group (all P < 0.05). With regard to the effect on ox- idative stress, the lowest level of MDA and the highest level of SOD were observed in the CRRT group among the three experiment groups (P < 0.05). In the same way, the proportions of apoptotic cells and the ex- pression of cleaved caspase-3 in the intestine in the two hypothermic groups were lower than in the NT group, with the lowest in the CRRT group (P < 0.05). Conclusively, compared with SC, cooling induced by CRRT was associated with the mitigation of the tissue inflammation, suppression of oxidative stress and decrease of cell apoptosis in the in- testine (P < 0.05, Fig. 8).

1. Discussion

This present study focused on the potential organ protection of ex- tracorporeal circuit cooling against PCAS based on a swine model. We found the protective effect of extracorporeal circuit cooling using

CRRT was significantly superior to SC from the following aspects: 1) hy- pothermia induced by extracorporeal circuit cooling was achieved sig- nificantly faster than SC; 2) extracorporeal circuit cooling significantly alleviated the renal and intestinal injury post resuscitation compared to SC; 3) with pathologic evidence, the protective effect of extracorpo- real circuit cooling on kidney and intestine was associated with de- creased inflammation of tissues, suppressed oxidative stress and decreased cell apoptosis compared with SC.

Laurent et al. [21] found that the combination of CRRT with TH was feasible in CA patients, and might improve the prognosis of PCAS. Two cases reports demonstrated that CRRT cooling yielded better neurolog- ical recovery for CA and acute heart failure [22,23]. Therefore, cooling induced by CRRT might offer an efficient way to produce TH in the clin- ical practice. Based on a previous study, 8-h CRRT cooling followed by 16-h SC was determined in our study to reduce the possibility of adverse events [21]. And no adverse events were observed in the CRRT group. Thus, extracorporeal circuit cooling using CRRT might be a safe way to induce TH with high efficiency. Additionally, a review [15] demon- strated that the achievement of temperature below 34 ?C within 3.5 h after ROSC seemed to be beneficial. In the present study, the blood tem- perature was initially decreased rapidly by submerging the circuit in ice water to release heat, followed by the maintenance of TH by wrapping the circuit within an adjustable heating device.

Most importantly, the present study found that rapid therapeutic

hypothermia induced by extracorporeal circuit cooling significantly mitigated the renal and intestinal injury after resuscitation with comparation with SC. Cr and BUN are two well-recognized markers of renal function. In our study, with a smaller increase of levels of Cr and BUN, potential Renal protection by extracorporeal circuit cooling was showed. IFABP is a cytosolic protein, which will be released into the cir- culation when intestinal permeability increases, making it an efficient marker for intestinal damage [24]. Due to the susceptibility to I/R, mes- enteric ischemia often occurs post resuscitation, causing an increase in intestinal permeability and subsequent bacterial translocation [25]. Pre- vious evidence has shown a linear relation between max endotoxin level and max IFABP (p = 0.01), suggesting that the higher the intestinal injury, the higher the level of endotoxin [6]. And DAO is an intracellular enzyme mainly located in Intestinal mucosa, catalyzing oxidative deam- ination of diamines [26]. Recent evidence suggests that the rise in plasma DAO level is strongly associated with the severity of intestinal tissue damage [27]. Therefore, the activity of plasma DAO can manifest the intestinal status and will increase in case of intestinal ischemia [26]. In our study, with a smaller increase of levels of IFABP and DAO, po- tential intestinal protection by extracorporeal circuit cooling was demonstrated.

Evidence from pathologic processes, including decreasing the in- flammation of tissues, suppressing oxidative stress and decreasing the level of apoptosis, was observed in tissues of kidney and intestine in the CRRT group. According to a growing body of literature, TNF-? and IL-6 are typical indexes to manifest the inflammatory response of the whole body or certain organs [28]. With a smaller elevation of TNF-? and IL-6, extracorporeal circuit cooling might have a protective influ- ence by decreasing tissue inflammation in the kidney and small intes- tine. The levels of MDA and SOD in tissues were also determined in our study. MDA, a substance Produced by reactive oxygen after degrading polyunsaturated lipids and may lead to intracellular toxic stress, is an indicator of oxidative stress, while SOD is a pivotal antioxi- dant in cells [11]. With a smaller elevation of MDA and larger elevation of SOD, extracorporeal circuit cooling may alleviate the renal and intes- tinal injury by suppressing oxidative stress. Previous studies found that CRRT could not decrease systemic inflammation post resuscitation in both CA patients [21] and rat models [29]. Therefore, the organ protec- tive effects in our study might be mostly ascribed to the fast induction of hypothermia by extracorporeal circuit cooling using CRRT.

In the kidney and intestine tissues among 3 experiment groups, the

lowest proportions of apoptotic cells and lowest expression of cleaved

Fig. 8. The comparisons of tissue inflammation, oxidative stress and cell apoptosis in intestine in different groups. (note: except the control group containing 5 swine, the other groups have 9 swine each). (A) The levels of TNF-? and IL-6; (B) The levels of MDA and the activities of SOD; (C) Representative photomicrographs of TUNEL assay and immunostaining of cleaved caspase-3 protein; (D) The percentage of TUNEL-positive cells and the IOD values of cleaved caspase-3-positive staining. CRRT indicates continuous renal replacement therapy; IL, interleukin; IOD, integrated optical density; MDA, malondialdehyde; NT, normothermia; SC, surface cooling; SOD, superoxide dismutase; TNF, tumor necrosis factor. ^aP < 0.05 versus Control group; ^bP < 0.05 versus NT group; ^cP < 0.05 versus SC group.

caspase-3 were observed in CRRT group (P < 0.05), which contributed to strengthening the organ protective effect by fast hypothermia in- duced by extracorporeal circuit cooling using CRRT. Caspase-3 is re- quired for most of the proteolysis during apoptosis, and the cleaved caspase-3 has been used to represent the level of cell apoptosis [30]. Therefore, we can conclude that extracorporeal circuit cooling might exert the organ protective effect by inhibiting the process of apoptosis.

There were several limitations that should be stated. Firstly, a 1 ?C/h rate of rewarming was used in our study based on previous results [31], while rewarming should be achieved at rate of about 0.25-0.5 ?C per hour based on the current guideline [32]. Second, the apparatus for cooling induced by CRRT was ready in advance, so the induction of TH was started immediately ROSC was obtained. However, a longer duration of more than 15 min are required to perform CRRT in the clinical setting.

1. Conclusion

Fast hypothermia induced by extracorporeal circuit cooling was su- perior to surface cooling in mitigating renal and intestinal injury post resuscitation.

Data availability

The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.

Funding

This work was supported by the Key Program Cosponsored by Zhejiang Province and Natural Health and Family Planning Commission of China (2018271879), the Zhejiang Provincial Welfare Scientific Re- search Project of China (LGD19H150003), the Zhejiang Provincial Wel- fare Scientific Research Project of China (LGF18H150003), the Zhejiang Provincial Medical Science Foundation of China (2018KY419).

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influ- ence the work reported in this paper.

Acknowledgements

This work was supported by the Key Program Cosponsored by Zhejiang Province and Natural Health and Family Planning Commission of China (2018271879), the Zhejiang Provincial Welfare Scientific Re- search Project of China (LGD19H150003), the Zhejiang Provincial Wel- fare Scientific Research Project of China (LGF18H150003), the Zhejiang Provincial Medical Science Foundation of China (2018KY419).

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