Establishment of Deep Hypothermic Circulatory Arrest in Rats

Summary

This protocol presents the establishment of deep hypothermic circulatory arrest in rats, which can be applied to investigate systemic inflammatory response syndrome, ischemia/reperfusion injury, oxidative stress, neuroinflammation, etc.

Abstract

Deep hypothermic circulatory arrest (DHCA) is routinely applied during surgeries for complex congenital heart disease and aortic arch disease. The present study aims to provide a method for establishing DHCA in rats. To evaluate the impact of the DHCA process on vital signs, a normal temperature cardiopulmonary bypass (CPB) rat model without circulatory arrest was used as a control. As expected, DHCA led to a significant decrease in body temperature and mean arterial blood pressure. The blood gas analysis indicated that DHCA increased lactic acid levels but did not influence the blood pH and the concentrations of hemoglobin, hematocrit, Na⁺, Cl⁻, K⁺, and glucose. Furthermore, compared with the normal temperature CPB rats, the results of the transmission electron microscopy showed a mild increase in hippocampal autophagosomes in the DHCA rats.

Introduction

Deep hypothermic circulatory arrest (DHCA) has been used in cardiac surgery since 1953¹_. DHCA involves reducing the patient's core temperature to profoundly hypothermic levels (15-22 °C) before globally interrupting the blood flow to the body². The circulatory arrest can provide a relatively bloodless operating field. Deep hypothermia decreases the metabolism, especially in the brain and myocardium, which is an effective method of protection against ischemia³. DHCA is commonly applied during surgeries for complex congenital heart disease, aortic arch disease, and even renal or ....

Protocol

The protocols underwent an institutional review and received approval from the Institutional Animal Care and Use Committee, Fuwai Hospital, Chinese Academy of Medical Sciences (FW-2021-0005). All the experimental procedures were performed in accordance with the Guide for the Care and Use of Laboratory Animals published by the National Institutes of Health.

NOTE: Male Sprague-Dawley rats (weight: 500-600 g, age: 12-14 weeks) were kept under standard laboratory conditions with free access to food and water. The rats were randomly allocated into two groups (n = 6, each group): the DHCA group, and the normal temperature CPB group (NtCPB group).....

Results

As the control group, the normal temperature CPB (NtCPB) rats without circulatory arrest showed a stable mean arterial blood pressure (MAP) and body temperature during the whole procedure, while the MAP of the DHCA rats decreased during the cardiac arrest (p < 0.01, Figure 3A). The temperature of the DHCA rats dropped quickly during the cooling phase and recovered gradually during the rewarming phase. When weaning the rats off the DHCA circuits, the temperature of the DHCA rats r.......

Discussion

Cannulation is the most fundamental procedure for establishing DHCA in rats. Before cannulation, soaking the artery with 0.5 mL of 2% lidocaine will make it easier to cannulate. After cannulation, heparinization with 500 IU/kg heparin via the external jugular vein is necessary to avoid microthrombus formation¹⁷. We have repeatedly found that this dose of heparin can achieve the goal of an activated clotting time (ACT) >480 s. The rewarming period is the most difficult part. It took mor.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Heat Exchanger	Xi’an Xijing Medical Appliance Co., Ltd	Animal-M
Membrane Oxygenator	Dongguan Kewei Medical Instrument Co., Ltd.	Micro-M
Monitor	Chengdu Techman Co., Ltd	BL-420s
Roller Pump	Changzhou Prefluid Technology Co.,Ltd	BL100
SD Rat	HFK Bioscience Co.,Ltd.	/
Sevoflurane	Maruishi Pharmaceutical Co. Ltd	H20150020
Shaver	Hangzhou Huayuan Pet Products Co.,Ltd.	/
Vaporizer	SPACECABS	/
Ventilator	Shanghai Alcott Biotech Co., Ltd	ALC-V8S
Water Tank	Maquet Critical Care AB	Jostra HCU20-600