Successful Defibrillation of Four Hypothermic Patients with Witnessed Cardiac Arrest.

BACKGROUND: Because of the limited evidence available, recommendations for defibrillation of hypothermic patients vary among published guidelines. AIM: To report successful defibrillation of four severely hypothermic patients with witnessed cardiac arrest. RESULTS: During a four-year period from 2014 to 2017, four of five hypothermic patients admitted to our institution with a history of sudden, unexpected ventricular fibrillation (core temperature: 24°C-27°C) were successfully defibrillated. Restoration of spontaneous circulation (ROSC) was possible after a single defibrillator shock (two patients) or during prolonged advanced life support cardiopulmonary resuscitation (two patients). Our patients and additional cases identified in the literature indicate that successful defibrillation is predominantly found in hypothermic patients with a core temperature above 24°C. CONCLUSIONS: Our data demonstrate that successful defibrillation and ROSC are possible in selected patients with severe accidental hypothermia and are perhaps more common than widely believed. These findings are of particular importance for mountain and wilderness rescue missions when transfer of an arrested patient to the nearest hospital providing extracorporeal rewarming is not possible. An automatic external defibrillator should be part of the medical equipment on any search or mountain rescue mission, in which the victim may have sustained accidental hypothermia.

Outcome of avalanche victims with out-of-hospital cardiac arrest.

STUDY BACKGROUND: Previous studies focused on the outcome of avalanche victims with out-of-hospital cardiac arrest (OHCA) after long duration of burial (>35min); the outcome of victims with short duration (≤35min) remains obscure. AIM OF THE STUDY: To investigate outcome of avalanche victims with OHCA. METHODS: Retrospective analysis of avalanche victims with OHCA between 2008 and 2013 in the Tyrolean Alps. RESULTS: 55 avalanche victims were identified, 32 of whom were declared dead after extrication without cardiopulmonary resuscitation (CPR), all with long duration of burial. In the remaining 23 CPR was initiated at scene; three were partially and 20 completely buried, nine of whom suffered short and 11 long duration of burial. All nine victims with short duration of burial underwent restoration of spontaneous circulation (ROSC) at scene, four of them after bystander CPR, five after advanced life support by the emergency physician. Two patients with ROSC after short duration of burial and bystander CPR survived to hospital discharge with cerebral performance category 1. None of the 11 victims with long duration of burial survived to hospital discharge, although six were transported to hospital with ongoing CPR and three were supported with extracorporeal circulation. CONCLUSIONS: In this case series survival with favourable neurological outcome was observed in avalanche victims with short duration of burial only if bystander CPR was immediately performed and ROSC achieved. Strategies for reducing avalanche mortality should focus on prompt extrication from the snow and immediate bystander CPR by uninjured companions.

Is extracorporeal rewarming indicated in avalanche victims with unwitnessed hypothermic cardiorespiratory arrest?

International guidelines recommend using extracorporeal rewarming in all hypothermic avalanche victims with prolonged cardiac arrest if they have patent airways and a plasma potassium level≤12 mmol/L. The aim of this study was to evaluate outcome data to determine if available experience with extracorporeal rewarming of avalanche victims supports this recommendation. At Innsbruck Medical University Hospital, 28 patients with hypothermic cardiac arrest following an avalanche accident were resuscitated using extracorporeal circulation. Of these patients, 25 were extricated from the snow masses with no vital signs and did not survive to hospital discharge. Three patients had witnessed cardiac arrest after extrication and a core temperature of 21.7°C, 22°C, and 24.0°C, two of whom survived long-term with full neurological recovery. A search of the literature revealed only one asystolic avalanche victim with unwitnessed hypothermic cardiac arrest (core temperature 19°C) surviving long-term. All other avalanche victims in the medical literature surviving prolonged hypothermic cardiac arrest suffered witnessed arrest after extrication with a core temperature below 24°C. Our results suggest that prognosis of hypothermic avalanche victims with unwitnessed asystolic cardiac arrest and a core temperature>24°C is extremely poor. Available outcome data do not support the use of extracorporeal rewarming in these patients.

Age-related efficacy of parathyroid hormone on osseointegration in the rat.

OBJECTIVE: Aging is a physiological determinant that can distinguish the outcome of a pharmaceutical therapy to improve osseointegration of titanium implants. Here we examined the possible interaction of intermittent parathyroid hormone (PTH) and the age of the recipient on the parameters of osseointegration in a rat tibia implantation model. MATERIAL AND METHODS: Twenty female Wistar rats aged 8 months and 20 female rats aged 2 months received PTH at 60 microg/kg body weight or a vehicle by a subcutaneous injection three times a week. After 4 weeks, histomorphometric analysis of the peri-implant area was performed. The possible interaction of the two factors on 'bone volume per tissue volume' (BV/TV) and 'bone-to-implant contact' (BIC) was tested by two-way analysis of variance. RESULTS: Based on data from the medullary compartment, two-way analysis of variance revealed that the effect of 'intermittent PTH' depends on the 'age of the recipient' when BV/TV is considered the dependent variable (P=0.04). Post hoc tests indicated that PTH leads to an increase of BV/TV of adult and young rats. However, when BIC was considered the dependent variable, no interaction was observed (P=0.14). PTH but not aging has a significant impact on BIC. In the cortical compartment, no effects of PTH on osseointegration were observed. CONCLUSIONS: The findings indicate that treatment with PTH is more effective on the peri-implant bone regeneration in adult than in young animals, supporting the importance to consider the influences of age on the development of pharmaceutical therapies to increase the process of osseointegration.

Simultaneous in vivo comparison of bone substitutes in a guided bone regeneration model.

A direct, simultaneous comparison of bone substitutes is hampered by the limited number of samples that can be tested simultaneously. The goal of this study was to establish a preclinical model for guided bone regeneration that offers testing of different bone substitutes in a one-wall defect situation. We show here that up to eight titanium hemispheres can be placed on the calvaria of minipigs. To establish our model, titanium hemispheres were filled with and without Bio-Oss, a deproteinized bovine bone mineral, Ostim, an aqueous paste of synthetic nanoparticular hydroxyapatite, and Osteoinductal, an oily calcium hydroxide suspension, before being positioned on the calvaria. After 6 and 12 weeks, titanium hemispheres were subjected to histological and histomorphometric analysis. We show here that bone filled approximately one-tenth of the area below the hemispheres which were left empty, indicating a critical size model for guided bone regeneration. In accordance with the documented osteoconductive properties of Bio-Oss and Ostim, titanium hemispheres were almost completely filled with bone. Moreover, the expected degradation profile of Bio-Oss and Ostim could be confirmed by histologic and histomorphometric analysis. Under the same conditions, Osteoinductal failed to exert osteoconductive properties, rather a progressive resorption of the host bone was observed. These results demonstrate that the preclinical model presented here is suitable to simultaneously compare bone substitutes with different material properties. Our model based on the titanium hemispheres allows evaluation of graft consolidation under standardized conditions thereby avoiding intra-individual variations.

The anti-angiogenic substance TNP-470 impairs peri-implant bone formation: a pilot study in the rabbit metaphysis model.

OBJECTIVES: To study the osseointegration of dental implants under the conditions of impaired blood vessel formation in a rabbit model. MATERIAL AND METHODS: Twenty-four titanium implants were placed in the diaphyses of 12 rabbits, two in each tibia. After 2 days, six animals received TNP-470, an anti-angiogenic substance, 10 mg/kg body weight, three times a week, by subcutaneous injection. The remaining six animals served as controls. All animals were sacrificed 6 weeks post implantation. RESULTS: The amount of newly formed bone (NFB) within a peri-implant distance of 0.2 mm and the percentage of bone-to-implant contacts (BIC) were determined in undecalcified ground sections. In both groups, appositional bone growth originating from the cortex was associated with a dense network of blood vessels. Within 1 mm apical from the implant shoulder, NFB was 29.3+/-6.7% in TNP-470 treated animals vs. 44.2+/-13.1% in the controls (P=0.03). In the adjacent cortical area NFB was 46.1+/-10.0% in TNP-470 treated animals and 58.4+/-3.0% in the control group (P=0.02). In the endosteal area, 3 mm from the implant shoulder NFB was 24.8+/-11.8% in TNP-470-treated animals and 27.0+/-9.6% in controls (P=0.73) and in the most apical peri-implant area corresponding to the bone marrow cavity 4.3+/-3.2% in TNP-470-treated animals and 10.5+/-5.2% in the controls (P=0.03). No decrease in BIC in response to TNP-470 was observed. CONCLUSION: The data suggest that TNP-470 decreases the formation of peri-implant bone, whereas BIC overall are not affected by it. The rabbit model presented here supports the importance of angiogenesis in the process of peri-implant bone formation.

Age-related changes of cell outgrowth from rat calvarial and mandibular bone in vitro.

AIM: To establish whether within an autograft ageing has an impact on the number of cells capable of responding to growth and differentiation factors released at defect sites. MATERIAL AND METHODS: The number of cells that grow out from calvarial and mandibular explants of rats 6 weeks and 9 months of age was evaluated and their response to mitogenic, chemotactic, and differentiation factors was characterized in vitro. The cell number was determined by automated counting, proliferation was evaluated by measuring the amount of (tritiated) (3)[H]thymidine incorporated into the DNA, and migration was assessed with the modified Boyden chamber assay. Alkaline phosphatase activity served as a marker of osteogenic differentiation. RESULTS: A confluent layer of cells was observed in mandibular and calvarial explant cultures derived from young rats within 10 days, while only sporadic cells were counted in cultures from adult animals. The number of cells derived from calvarial and mandibular bone of young rats was nine and five times higher, respectively, than that in explants from adult rats. Cells isolated from calvarial and mandibular explants responded to platelet-released supernatant by increased proliferation and migration in both age groups. Upon incubation with bone morphogenetic protein (BMP-6), the alkaline phosphatase activity of calvaria-derived cells from both age groups was higher than in unstimulated controls. Only one sample of cells derived from mandibular explants showed responsiveness to BMP-6 in the young age group, whereas none of the cell samples responded to BMP-6 in the adult age group. CONCLUSION: The number of cells capable of growing out from mandibular and calvarial grafts in vitro is lower in adult animals than in young animals. However, bone-derived cells from both young and adult rats respond to growth and differentiation factors present at defect sites, while there are topographic differences in the responsiveness to BMP-6.