Central A1-receptor activation associated with onset of torpor protects the heart against low temperature in the Syrian hamster

Body temperature drops dramatically during hibernation, but the heart retains the ability to contract and is resistant to induction of arrhythmia. Although adaptive changes in the heart prior to hibernation may be involved in the cold-resistant property, it remains unclear whether these changes are sufficient for maintaining cardiac pulsatility under an extreme hypothermic condition. We forcibly induced hypothermia in Syrian hamsters by pentobarbital anesthesia combined with cooling of the animals. This allows reproduction of a hypothermic condition in the absence of possible hibernation-specific reactions. Unlike hypothermia in natural hibernation, the forced induction of hypothermia caused atrioventricular block. Furthermore, J-waves, which are typically observed during hypothermia in nonhibernators, were recorded on an ECG. The origin of the J-wave seemed to be related to irreversible injury of the myocardium, because J-waves remained after recovery of body temperature. An abnormal ECG was also found when hypothermia was induced in hamsters that were well adapted to a cold and darkened environment or hamsters that had already experienced hibernation. These results suggest that acclimatization prior to hibernation does not have a crucial effect at least on acquisition of cardiac resistance to low temperature. In contrast, an abnormal ECG was not observed in the case of hypothermia induced by central administration of an adenosine A1-receptor agonist and subsequent cooling, confirming the importance of the adenosine system for inducing hibernation. Our results suggest that some specific mechanisms, which may be driven by a central adenosine system, operate for maintaining the proper cardiac pulsatility under extreme hypothermia.     

J deflections on ECG in severe hypothermia and hypokalaemia: a case report

The J wave, also known as Osborn wave, is a deflection that can be observed on the surface ECG as a late delta wave, seen at the end of the QRS complex. In this case, a 75-year-old woman, after 1 day of continuous haemodialysis, showed a marked hypothermia (28.5°C) and severe hypokalaemia (1.7 mEq/l). Bradycardia was seen on the monitor and J waves were recognised on the ECG recording. After appropriate replacement of potassium and treatment of hypothermia, the J waves disappeared spontaneously.     

Heart rate variability and electrocardiogram waveform as predictors of morbidity during hypothermia and rewarming in rats

This study examined electrocardiogram (ECG) waveform, heart rate (HR), mean blood pressure (BP), and HR variability as potential autonomic signatures of hypothermia and rewarming. Adult male Sprague-Dawley rats had telemetry transmitters surgically implanted, and 2 weeks were allowed for recovery prior to induction of hypothermia. Rats were lightly anesthetized (sodium pentobarbital, 35 mg/kg i.p.) and placed in a coil of copper tubing through which temperature-controlled water was circulated. Animals were cooled to a core temperature (Tc) of 20 degrees C, maintained there for 30 min, and then rewarmed. Data (Tc, BP, HR from ECG, and 10-s strips of ECG waveforms) were collected every 5 min throughout hypothermia and rewarming. Both HR and BP declined after initial increases with the drop in HR starting at a higher Tc than the drop in BP (29.6 +/- 2.4 degrees C vs. 27.1 +/- 3.3 degrees C, p < 0.05). Animals that were not successfully rewarmed exhibited a significant (p < 0.05) increase in the normalized standard deviation of interbeat intervals (IBI) throughout cooling compared with animals that were successfully rewarmed. The T wave of the ECG increased in amplitude and area with decreasing Tc. T-wave amplitude and IBI variability show potential as predictors of survival in hypothermic victims.     

Moderate hypothermia prevents neural cell apoptosis following spinal cord ischemia in rabbits

Paraplegia is a disastrous complication after operations of descending and thoracoabdominal aortic aneurysm. Regional hypothermia protects against spinal cord ischemia although the protective mechanism is not well know. The objective of this study is to examine whether hypothermia protects the spinal cord by preventing apoptosis of nerve cell and also investigate a possible mechanism involved in hypothermia neuroprotection. Cell apoptosis with necrosis was evident in the spinal cord 24 h after 30 min of ischemia. Moderate hypothermia decreased the incidence of apoptotic nerve cells. Both cell apoptosis and necrosis were attenuated by hypothermia, p53 expression increased and bcl-2 expression declined after ischemia, while hypothermia mitigated these changes. This study suggests that apoptosis contributes to cell death after spinal cord ischemia, and that moderate hypothermia can prevent nerve cell apoptosis by a mechanism associated with bcl-2 and p53 genes.     

Accidental deep hypothermia with cardiac arrest. Prompt complete recovery after rewarming by extracorporeal circulation. Case report

BACKGROUND: Deep accidental hypothermia (core temperature <28 degrees C) is an uncommon medical emergency requiring rapid active core rewarming. Extracorporeal circulation has become the treatment of choice for deep hypothermic patients with cardiac arrest. CASE REPORT: We report on a 30-year-old patient who suffered from deep accidental hypothermia (core temperature 24.8 degrees C) and cardiac arrest by prolonged exposure to a cold urban environment as a consequence of severe ethylalcohol intoxication. The rewarming with the aid of extracorporeal circulation was initiated shortly after his arrival at the hospital. External cardiac massage was maintained until full ECC fl ow was established. The patient was weaned from extracorporeal circulation after 157 min, awaked 4 hours later and consequently extubated within 16 hours after rewarming with no neurological impairment. At 3-week follow-up, the patient was fully re-integrated in his work and personal life. CONCLUSION: This case demonstrates the excellent prognosis of a young victim in the case of deep accidental hypothermia with cardiac arrest, provided that deep hypothermia precedes the cardiac arrest and rewarming by extracorporeal circulation is immediately applied. Simultaneous ethyl alcohol intoxication can be considered a protective factor improving the patient's outcome. Complete recovery was achieved within 24 hours after the accident.     

A microarray analysis of the effects of moderate hypothermia and rewarming on gene expression by human hepatocytes (HepG2)

The gene expression changes produced by moderate hypothermia are not fully known, but appear to differ in important ways from those produced by heat shock. We examined the gene expression changes produced by moderate hypothermia and tested the hypothesis that rewarming after hypothermia approximates a heat-shock response. Six sets of human HepG2 hepatocytes were subjected to moderate hypothermia (31°C for 16 h), a conventional in vitro heat shock (43°C for 30 min) or control conditions (37°C), then harvested immediately or allowed to recover for 3 h at 37°C. Expression analysis was performed with Affymetrix U133A gene chips, using analysis of variance-based techniques. Moderate hypothermia led to distinct time-dependent expression changes, as did heat shock. Hypothermia initially caused statistically significant, greater than or equal to twofold changes in expression (relative to controls) of 409 sequences (143 increased and 266 decreased), whereas heat shock affected 71 (35 increased and 36 decreased). After 3 h of recovery, 192 sequences (83 increased, 109 decreased) were affected by hypothermia and 231 (146 increased, 85 decreased) by heat shock. Expression of many heat shock proteins was decreased by hypothermia but significantly increased after rewarming. A comparison of sequences affected by thermal stress without regard to the magnitude of change revealed that the overlap between heat and cold stress was greater after 3 h of recovery than immediately following thermal stress. Thus, while some overlap occurs (particularly after rewarming), moderate hypothermia produces extensive, time-dependent gene expression changes in HepG2 cells that differ in important ways from those induced by heat shock.     

Percutaneous closure of a coronary fistula between the right coronary artery to the left atrium

We describe a case of a congenital coronary artery fistula of the right coronary artery draining into the left atrium in an eight-year-old boy. The initial diagnosis was made after the detection of a continuous cardiac murmur at the age of six years. Transthoracic echocardiography showed the right coronaric ostium dilatation, the site of drainage in the left atrium and left ventricle volume overload. Catheterization confirmed the diagnosis. The patient underwent percutaneous closure by PDA occluder device. Immediate post-closure angiograms showed complete occlusion of the fistula. The patient showed transient ischemic changes on ECG associated to an increase of plasmatic levels of the cardiac enzyme. ECG and cardiac enzyme were normal one week after the procedure.     

Physiology and Pharmacology of Hypothermia

Homoiothermic organisms react to hypothermia by shivering and thermogenesis to retain their euthermic state. This reactive homeostatic mechanism recruits a strong sympathetic response, which must be suppressed by anesthesia and adjuvants during induced hypothermia. Below 30° C there is significant neural and organ depression associated with cold narcosis. Cardiac arrhythmias and ventricular fibrillation are grave developments when the core temperature is below 28° C. Proper cardiopulmonary support must be instituted in a patient who has induced or accidental hypothermia at these severely hypothermic levels.Although clinical hypothermia is used to protect the brain and the heart from ischemic insults during an operation, it induces a complex array of physiologic changes in the body that must be appreciated so that optimal care may be provided to a patient.     

Effects of hypothermia and re-warming on the inflammatory response in a murine multiple hit model of trauma

INTRODUCTION: Although, hypothermia is a frequent event after trauma, it is unclear whether its beneficial or detrimental effects are more important. This study aims to quantify the effects of hypothermia and re-warming on the inflammatory response after fracture/hemorrhage and subsequent fracture stabilization with resuscitation. MATERIALS AND METHODS: Eighty-one male C57Bl/6 mice (aged 8-10 weeks, weighing 22.0+/-3.0 g) underwent femoral fracture and hemorrhage followed by resuscitation and splint fixation of the fracture. Animals were sacrificed 3h after induction of hemorrhage and fracture. Besides a sham group (n=6), four experimental groups were created: A: normothermia (n=12), B: hypothermia after trauma (n=21), C: re-warming after resuscitation and before stabilization (n=21), and D: hypothermia before trauma (n=21). Groups B-D were further subdivided into three subgroups according to the degree of hypothermia (subgroup 1: 35-33 degrees C, subgroup 2: 32.9-30.0 degrees C, and subgroup 3: 29.9-27.0 degrees C). Plasma cytokine (TNF-alpha, IL-6, and IL-10) and chemokine (MCP-1) concentrations were determined by ELISA, pulmonary permeability changes were quantified, and histological analysis of lung and liver tissues was performed. RESULTS: Normothermia resulted in a significantly increased early mortality rate. A significantly increased pro-inflammatory and decreased anti-inflammatory responses were also observed in normothermia as compared to hypothermia. The extent of these changes was most pronounced in the severe hypothermic group. Re-warming after mild hypothermia resulted in a pro-inflammatory response comparable to normothermia. CONCLUSION: Hypothermia has a beneficial effect on early survival after trauma, which appears to be independent of the level of hypothermia and re-warming. Re-warming, however, enhanced the pro-inflammatory response. Further studies with a longer posttraumatic observation period are required to investigate the long term effects of the hypothermia and re-warming-induced changes on the pro- and anti-inflammatory responses.     

Proteomic analysis of global protein expression changes in the endothelin-1 rat model for cerebral ischemia: Rescue effect of mild hypothermia

Mild hypothermia is a promising neuroprotective therapy in stroke management. However, little is known about its effects on the global protein expression patterns in brain regions affected by ischemic stroke. We investigated protein expression changes associated with the neuroprotective effects of hypothermia via a functional proteomics approach through the analysis of the core (striatum) and the penumbra (cortex) after an ischemic insult in rats induced by endothelin-1 (Et-1). Functional outcome, infarct volume and related global protein expression changes were assessed 24 h after the insult using two-dimensional difference gel electrophoresis. Mild hypothermia, induced 20 min after endothelin-1 infusion, improved the neurological outcome, reflected by a 36% reduction in infarct volume and a significantly better neurological deficit score. Hypothermia was typically associated with opposite protein expression changes inthe cortex to those induced by stroke under normothermic conditions, but not in the striatum. The main cellular processes rescued by hypothermia and potentially involved in the protection of the cortex are cellular assembly and organization, followed by cell signaling, thereby confirming that hypothermia is neuroprotective through multiple molecular and cellular pathways.     

Exercise ECG changes in normal women

Submaximal and/or maximal exercise was carried out by 357 women without a history of cardiovascular disease, using a bicycle ergometer and/or treadmill while monitored by a bipolar ECG lead CM₅. In 40- to 60-year-old women the incidence of an ischemic ECG pattern during or after exercise ranged from 20 to 50%. Because clinical coronary disease can be expected in less than 10% of normal women followed for 16 years, most of these ECG changes were not considered to be due to occult coronary disease. At the present time exercise ECG changes in women cannot be used with any reliability as an aid in the diagnosis of chest pain or in screening normal female populations for coronary heart disease.     

低硒对大鼠心电图的影响及补硒后的变化

目的:探讨低硒对大鼠心电图的影响及补硒后心电图的变化。方法:将30只SD大鼠随机分为对照组、低硒组及补硒组,每组各10只,对照组喂养标准饲料,低硒组喂养低硒饲料,补硒组喂养低硒饲料14周后再给予亚硒酸钠补硒3周,各组喂养17周后,检测大鼠的血硒、血清谷胱甘肽过氧化物酶及心电图的变化。结果:低硒组大鼠血硒水平和血清谷胱甘肽过氧化物酶水平与对照组相比明显降低(P0.05),补硒后两者又明显增加(P0.05)。正常对照组大鼠心电图大部分正常,低硒组大鼠心电图多数为异常心电图,主要表现为室性早搏、室性心动过速、交界性房性早搏、T波低平等,补硒组大鼠心电图大部分恢复正常心电图,仅有少部分表现为异常心电图。结论:低硒可导致大鼠谷胱甘肽过氧化物酶活性减低,低硒饮食后,大鼠心电图明显发生异常,多表现为室性心律失常,补硒可使低硒所致的心电图变化多数恢复正常。     

Drastic hypothermia after intraperitoneal injection of okadaic acid,a diarrhetic shellfish poisoning toxin,in mice

The mouse bioassay for diarrhetic shellfish poisoning (DSP) toxins had been used as the official method in Japan and also used in the world. In this study, hypothermia, one of the symptoms observed in mice after inoculation with DSP toxins, were characterized. Lethal and sublethal doses of okadaic acid (OA), a representative component of DSP toxins, were inoculated intraperitoneally into mice. Body-temperature changes over time were measured by an electronic thermometer or monitored by an infrared camera. Drastic hypothermia (<30°C in some mice) was observed in a few hours after administration of a lethal dose of OA. Dose-dependency was clearly seen between doses of OA inoculated and body-temperature decrease. Drastic hypothermia was also detected by using an infrared camera. These results suggest that hypothermia could be used as an index for the humane endpoint in experimental animal toxicological studies.     

Emotional problems in children; the uses of drugs in therapeutic management

The repair of intracardiac defects under direct vision by opening the heart to expose the operative field, with the aid of hypothermia or a pump-oxygenator, is now a practical clinical method. Twelve patients were operated upon by this method. In eight patients an atrial septal defect was repaired during total circulatory occlusion under hypothermia. The seven patients in this group who had uncomplicated atrial defects survived the operation and are doing well after a short follow-up period. One patient with an unrecognized, associated ventricular defect died at the time of operation. Four patients were operated upon during total cardiac by-pass with the DeWall bubble-oxygenator. The first three patients survived operation and are continuing to do well after a brief follow-up period. In the fourth patient an atrioventricularis communis was repaired by the reconstruction of an atrial and ventricular septum with a plastic prosthesis. This patient died at the end of operation.     

The effect of X-rays and artificial hypotermia on lipids in rat neocortex

Lipid content of tissue and of fraction of microsomes in neocortex of Wistar rats was studies under artificial hypothermia, after X-ray irradiation in dose 8 Gy under conditions of normothermia and artificial hypothermia in 48 h. The condition of artificial hypothermia get by cooling of rats to 15-18 degrees C. It was shown, that in fraction of microsomes of hypothermia rats the content of phosphatidylinositol was decreased, and in 48 h after cooling of rats the amount of protein, total and individual phospholipids was increased. The lipid content in tissue and in fraction of microsomes of rats, which were irradiated in normotermia, had no changes after 48 h. In fraction of microsomes of rats, which were irradiated after hypothermia, the amount of protein, total phospholipids, sphingomyelin, phosphatidylcholine and phosphatidylserine is increased trustworthy. Thus, we think, that radioprotective effect of hypotermia may be connected with the accumulation of proteins and of phospholipids in the endoplasmic reticulum membranes of neocortex.     

Aprotinin reverses ECG abnormalities induced by Mesobuthus tamulus concanesis, Pocock venom in adult rats

The kinins are implicated in the pathogenesis of scorpion envenomation. Therefore, this study was carried out to examine the involvement of kinins for the ECG abnormalities induced by M. tamulus concanesis, (BT) venom in anaesthetized rats. ECG was recorded using needle electrodes with limb lead II configuration. The PR interval, QRS wave pattern, QRS duration, ST segment and heart rate were examined in saline only, venom alone, and venom after aprotinin groups. BT venom (5 mg/kg) produced heart block of varying degree and ischemia-like changes in ECG wave pattern and the animals died within 30 min after exposure to venom. In aprotinin pretreated animals, the initial ECG changes produced by venom persisted, but after 15 min the ECG pattern improved and the animals survived for the entire period of observation (120 min). The results indicate that aprotinin protected the rats against the cardiotoxicity induced by BT venom.     

Pitfalls in cardiology: myocardial ischaemia in carbon monoxide poisoning

Carbon monoxide poisoning is a major cause of morbidity and mortality worldwide. Immediate and proper treatment is crucial for prognosis and is merely dependent on accurate diagnosis. However, correct diagnosis can be difficult due to the aspecific symptomatology in CO poisoning. In this report a case is discussed in which a patient with accidental CO poisoning presented primarily with syncope, extensive ECG changes and elevated troponin levels. In addition, a limited review of the current literature is provided.     

Patient safety in plastic surgery

LEARNING OBJECTIVES: After reading this article, the participant should be able to: 1. Recognize risk factors for venous thromboembolism and identify patients who would benefit from prophylactic anticoagulation; 2. Describe the effects of hypothermia in the perioperative period. 3. Understand the importance of blood pressure control in the plastic surgery patient. SUMMARY: This article provides a summary of important factors that contribute to improved patient safety in plastic surgery. The identification of patients and procedures that have an increased risk of complications enables the physician to carry out prophylactic measures to reduce the rate of these complications. Venous thromboembolism, hypothermia, bleeding diathesis, and perioperative hypertension are identifiable risks of plastic surgery, which can lead to significant morbidity and mortality. An evidence-based system and individual practice measures can help to decrease these risks. Thorough preoperative patient evaluation, detailed informed consent, and perioperative care delivered in a safe environment can contribute to improved safety in plastic surgery.