Esophageal Heat Exchanger Versus Water-Circulating Cooling Blanket for Targeted Temperature Management

To date, the optimal cooling device for targeted temperature management (TTM) remains unclear. Water-circulating cooling blankets are broadly available and quickly applied but reveal inaccuracy during maintenance and rewarming period. Recently, esophageal heat exchangers (EHEs) have been shown to be easily inserted, revealed effective cooling rates (0.26-1.12 degrees C/h), acceptable deviations from target core temperature (<0.5 degrees C), and rewarming rates between 0.2 and 0.4 degrees C/h. The aim of this study was to compare cooling rates, accuracy during maintenance, and rewarming period as well as side effects of EHEs with water-circulating cooling blankets in a porcine TTM model. Mean core temperature of domestic pigs (n = 16) weighing 83.2 +/- 3.6 kg was decreased to a target core temperature of 33 degrees C by either using EHEs or water-circulating cooling blankets. After 8 hours of maintenance, rewarming was started at a goal rate of 0.25 degrees C/h. Mean cooling rates were 1.3 +/- 0.1 degrees C/h (EHE) and 3.2 +/- 0.5 degrees C/h (blanket, p < 0.0002). Mean difference to target core temperature during maintenance ranged between +/- 1 degrees C. Mean rewarming rates were 0.21 +/- 0.01 degrees C/h (EHE) and 0.22 +/- 0.02 degrees C/h (blanket, n.s.). There were no differences with regard to side effects such as brady- or tachycardia, hypo- or hyperkalemia, hypo- or hyperglycemia, hypotension, shivering, or esophageal tissue damage. Target temperature can be achieved faster by water-circulating cooling blankets. EHEs and water-circulating cooling blankets were demonstrated to be reliable and safe cooling devices in a prolonged porcine TTM model with more variability in EHE group

Intravascular Cooling Device Versus Esophageal Heat Exchanger for Mild Therapeutic Hypothermia in an Experimental Setting

BACKGROUND: Targeted temperature management is a standard therapy for unconscious survivors of cardiac arrest. To date, multiple cooling methods are available including invasive intravascular cooling devices (IVDs), which are widely used in the clinical setting. Recently, esophageal heat exchangers (EHEs) have been developed providing cooling via the esophagus that is located close to the aorta and inferior vena cava. The objective was to compare mean cooling rates, as well as differences, to target temperature during maintenance and the rewarming period of IVD and EHE. METHODS: The study was conducted in 16 female domestic pigs. After randomization to either IVD or EHE (n = 8/group), core body temperature was reduced to 33 degrees C. After 24 hours of maintenance (33 degrees C), animals were rewarmed using a target rate of 0.25 degrees C/h for 10 hours. All cooling phases were steered by a closed-loop feedback system between the internal jugular vein and the chiller. After euthanasia, laryngeal and esophageal tissue was harvested for histopathological examination. RESULTS: Mean cooling rates (4.0 degrees C/h +/- 0.4 degrees C/h for IVD and 2.4 degrees C/h +/- 0.3 degrees C/h for EHE; P < .0008) and time to target temperature (85.1 +/- 9.2 minutes for IVD and 142.0 +/- 21.2 minutes for EHE; P = .0008) were different. Mean difference to target temperature during maintenance (0.07 degrees C +/- 0.05 degrees C for IVD and 0.08 degrees C +/- 0.10 degrees C for EHE; P = .496) and mean rewarming rates (0.2 degrees C/h +/- 0.1 degrees C/h for IVD and 0.3 degrees C/h +/- 0.2 degrees C/h for EHE; P = .226) were similar. Relevant laryngeal or esophageal tissue damage could not be detected. There were no significant differences in undesired side effects (eg, bradycardia or tachycardia, hypokalemia or hyperkalemia, hypoglycemia or hyperglycemia, hypotension, overcooling, or shivering). CONCLUSIONS: After insertion, target temperatures could be reached faster by IVD compared to EHE. Cooling performance of IVD and EHE did not significantly differ in maintaining target temperature during a targeted temperature management process and in active rewarming protocols according to intensive care unit guidelines in this experimental setting

Oesophageal heat exchangers with a diameter of 11mm or 14.7mm are equally effective and safe for targeted temperature management.

BACKGROUND:Targeted temperature management (TTM) is widely used in critical care settings for conditions including hepatic encephalopathy, hypoxic ischemic encephalopathy, meningitis, myocardial infarction, paediatric cardiac arrest, spinal cord injury, traumatic brain injury, ischemic stroke and sepsis. Furthermore, TTM is a key treatment for patients after out-of-hospital cardiac-arrest (OHCA). However, the optimal cooling method, which is quick, safe and cost-effective still remains controversial. Since the oesophagus is adjacent to heart and aorta, fast heat-convection to the central blood-stream could be achieved with a minimally invasive oesophageal heat exchanger (OHE). To date, the optimal diameter of an OHE is still unknown. While larger diameters may cause thermal- or pressure-related tissue damage after long-term exposure to the oesophageal wall, smaller diameter (e.g., gastric tubes, up to 11mm) may not provide effective cooling rates. Thus, the objective of the study was to compare OHE-diameters of 11mm (OHE11) and 14.7mm (OHE14.7) and their effects on tissue and cooling capability. METHODS:Pigs were randomized to OHE11 (N = 8) or OHE14.7 (N = 8). After cooling, pigs were maintained at 33°C for 1 hour. After 10h rewarming, oesophagi were analyzed by means of histopathology. The oesophagus of four animals from a separate study that underwent exactly the identical preparation and cooling protocol described above but received a maintenance period of 24h were used as histopathological controls. RESULTS:Mean cooling rates were 2.8±0.4°C°C/h (OHE11) and 3.0±0.3°C °C/h (OHE14.7; p = 0.20). Occasional mild acute inflammatory transepithelial infiltrates were found in the cranial segment of the oesophagus in all groups including controls. Deviations from target temperature were 0.1±0.4°C (OHE11) and 0±0.1°C (OHE14.7; p = 0.91). Rewarming rates were 0.19±0.07°C °C/h (OHE11) and 0.20±0.05°C °C/h (OHE14.7; p = 0.75). CONCLUSIONS:OHE with diameters of 11 mm and 14.7 mm achieve effective cooling rates for TTM and did not cause any relevant oesophageal tissue damage. Both OHE demonstrated acceptable deviations from target temperature and allowed for an intended rewarming rate (0.25°C/h)

Positron Emission Tomography Imaging of Long-Term Expression of the 18 kDa Translocator Protein After Sudden Cardiac Arrest in Rats

Background: Knowledge about the neuroinflammatory state during months after sudden cardiac arrest is scarce. Neuroinflammation is mediated by cells that express the 18 kDa translocator protein (TSPO). We determined the time course of TSPO-expressing cells in a rat model of sudden cardiac arrest using longitudinal in vivo positron emission tomography (PET) imaging with the TSPO-specific tracer [F-18]DAA1106 over a period of 6 months. Methods: Five male Sprague Dawley rats were resuscitated from 6 min sudden cardiac arrest due to ventricular fibrillation, three animals served as shams. PET measurements were performed on day 5, 8, 14, 90, and 180 after intervention. Magnetic resonance imaging was performed on day 140. Imaging was preceded by Barnes Maze spatial memory testing on day 3, 13, 90, and 180. Specificity of [F-18]DAA1106 binding was confirmed by Iba-1 immunohistochemistry. Results: [F-18]DAA1106 accumulated bilaterally in the dorsal hippocampus of all sudden cardiac arrest animals on all measured time points. Immunohistochemistry confirmed Iba-1 expressing cells in the hippocampal CA1 region. The number of Iba-1-immunoreactive objects per mm(2) was significantly correlated with [F-18]DAA1106 uptake. Additionally, two of the five sudden cardiac arrest rats showed bilateral TSPO-expression in the striatum that persisted until day 180. In Barnes Maze, the relative time spent in the target quadrant negatively correlates with dorsal hippocampal [F-18]DAA1106 uptake on day 14 and 180. Conclusions: After sudden cardiac arrest, TSPO remains expressed over the long-term. Sustainable treatment options for neuroinflammation may be considered to improve cognitive functions after sudden cardiac arrest

Pulmonary artery temperature profile of OHE11 (N = 8) and OHE14.7 (N = 8) during cooling period, maintenance and rewarming period.

<p>Pulmonary artery temperature profile of OHE11 (N = 8) and OHE14.7 (N = 8) during cooling period, maintenance and rewarming period.</p

Mean cooling rates of OHE11 (N = 8) and OHE14.7 (N = 7) during cooling period.

<p>Mean cooling rates of OHE11 (N = 8) and OHE14.7 (N = 7) during cooling period.</p

Levels of Oesophageal Tissue Damage.

<p>Levels of Oesophageal Tissue Damage.</p

Oesophageal heat exchangers with a diameter of 11mm or 14.7mm are equally effective and safe for targeted temperature management - Fig 5

<p>(a.) Representative undamaged cranial oesophageal tissue segment after treatment with OHE11 (ep: epithelium layer, mg: mucosal glands). No damage was found in oesophageal lamina mucosa, submucosa, muscularis, and adventitia. Epithelial layer thickness was inhomogeneous since cells of the multilayered squamous epithelium are physiologically desquamating. Scale bar: 200μm; (b/c.) Laryngeal oesophageal tissue segment after treatment with OHE11. Mononuclear inflammatory cells infiltrate the epithelial layer (arrow) of the mucosa. Activated lymphoid tissue is evident transmurally in the oesophageal wall. Scale bar: 100μm; (d.) Cranial oesophageal tissue segment after treatment with OHE14.7. Submucosal glands are infiltrated with inflammatory cellular infiltrates in the lamina submucosa (arrow). Scale bar: 100μm.</p

Design of Oesophageal Heat Exchanger.

<p>The OHE consisted of silicone designated for medical use. The tube (500mm length) consisted of three integrated tubes: (a) the outlet tube supplied water from the temperature regulating device (HICO Variotherm 555, Hirtz & Co.KG, Cologne, Germany), and was connected to the inlet tube (b), which withdrew the water back to the chiller. A third tube (c) provided gastric suctioning. Purified water served as temperature regulating agent. Water temperature was assessed at the inlet (<i>T</i>_<i>in</i>) and the outlet (<i>T</i>_<i>out</i>) of the OHE. Water could be cooled down to a minimum of 3°C or warmed to a maximum of 41°C. With a feedback loop, which registered the pulmonary artery temperature (Gold standard), the water temperature was continuously adjusted to the requirements of the study protocol. Water flow rate (<i>L</i>/min) was measured in the forward line. Both OHE11 and OHE14.7 were inserted in uninflated (A) conditions to protect the oesophageal epithelium from desquamation and avoid unnecessary contact pressure. Immediately after initiation of cooling, OHE deflated (B) to their particular diameters. Under clinical circumstances, a blind advance of the OHE similar to a gastric tube may conceivable.</p