Elisabeth Kornberger

Prognostic markers in patients with severe accidental hypothermia and cardiocirculatory arrest

The aim of this retrospective study was to investigate whether plasma potassium, pH and activated clotting time (ACT), obtained from a central venous blood sample immediately after admission to hospital, could predict outcome in patients with severe accidental hypothermia and cardiocirculatory arrest. Twenty-two patients rewarmed with cardiopulmonary bypass were studied retrospectively (12 patients after avalanche accidents, seven patients after cold water submersion and three patients after prolonged exposure to cold). In 12 patients stable spontaneous circulation could not be restored. In 10 patients stable spontaneous circulation could be restored. Two of these 10 patients survived long-term. Plasma potassium, central venous pH and ACT were clinically useful prognostic markers in hypothermic arrest victims after avalanche accidents: a plasma potassium value exceeding 9 mmol/l, a pH equal to or less than 6.50 or an ACT exceeding 400 s was seen in patients in whom spontaneous circulation could not be restored. Plasma potassium, central venous pH and ACT were of only limited prognostic value in hypothermic arrest victims following cold water submersion or prolonged exposure to cold. In hypothermic arrest victims after cold water submersion a central venous pH as low as 6.51 on admission did not exclude long-term survival. Moderate and severe hyperkalemia in arrest victims after prolonged exposure to cold need not necessarily indicate postmortem autolysis. A decision to continue or terminate resuscitation cannot be based on laboratory parameters. Nevertheless, our data suggest that plasma potassium, central venous pH and ACT on admission can be used to identify hypothermic arrest victims in whom death preceded cooling. If several hypothermic arrest victims are admitted simultaneously after avalanche accidents, these 3 parameters can help not to waste limited cardiopulmonary bypass facilities for patients with no hope of survival.

Forced air surface rewarming in patients with severe accidental hypothermia

Methods of rewarming patients with severe accidental hypothermia remain controversial. This paper reports our experience with the use of forced air rewarming in patients with severe accidental hypothermia and a body core temperature below 30 degrees C. Fifteen hypothermic patients (body core temperature 24-30 degrees C) were successfully treated with forced air rewarming to a body core temperature above 35 degrees C (mean rewarming rate 1.7 degrees C/h, range from 0.7 to 3.4 degrees C/h). An afterdrop phenomenon was not observed in any of the patients. Nine hypothermic patients (group 1) had no prehospital cardiac arrest, all nine were long-term survivors and made a full recovery. Six patients (group 2) had prehospital cardio circulatory arrest with restoration of spontaneous circulation. None of the group 2 patients survived long-term. Group 1 and group 2 patients did not differ in core temperature (26.6+/-1.6 degrees C group 1 and 27.0+/-1.8 degrees C group 2). Group 2 patients needed catecholamine support during rewarming more frequently (83 versus 22%) and had higher lactate levels and lower pH values at all points of observation. In conclusion our preliminary data indicate that forced air rewarming is an efficient and safe method of managing patients with severe accidental hypothermia. The poor outcome of patients with a history of prehospital cardiopulmonary resuscitation is probably due to irreversible ischaemic brain damage in primarily asphyxiated avalanche and near-drowning victims, rather than the consequence of the rewarming method used.

Effects of epinephrine in a pig model of hypothermic cardiac arrest and closed-chest cardiopulmonary resuscitation combined with active rewarming

OBJECTIVE The aim of the current study was to assess the effects of epinephrine in a pig model of hypothermic cardiac arrest followed by closed-chest cardiopulmonary resuscitation combined with active rewarming, simulating the clinical management of an arrested hypothermic patient in a hospital without cardiopulmonary bypass facilities. DESIGN Prospective, randomized animal study. SETTING University research laboratory. SUBJECTS Twelve 12- to 16-week-old domestic pigs. INTERVENTIONS Pigs were surface cooled to a body core temperature of 28 degrees C. After 4 min of untreated cardiac arrest, manual closed-chest CPR and thoracic lavage with 40 degrees C warmed fluid were started. After 3 min of external chest compression animals were randomly assigned to receive epinephrine (45, 45 and 200 microg/kg) or saline placebo in 5-min intervals. MEASUREMENTS AND MAIN RESULTS Coronary perfusion pressure was about 15 mmHg in placebo group pigs. Coronary perfusion pressure was significantly higher after epinephrine, but restoration of spontaneous circulation was not more frequent (one of six epinephrine versus three of six saline placebo pigs, P=0.34). After 45 microg/kg epinephrine the arterial PO(2) was significantly lower when compared to the saline placebo. The third 200 microg/kg epinephrine dose resulted in a significantly enhanced mixed venous hypercarbic acidosis. CONCLUSIONS After a short 4-min period of hypothermic cardiac arrest, epinephrine may not be necessary to maintain coronary perfusion pressure around the threshold usually correlating with successful defibrillation, even during prolonged closed-chest CPR combined with active rewarming. The enhanced mixed venous hypercarbic acidosis in epinephrine-treated animals may support the argument against repeated or high dose epinephrine administration during hypothermic CPR.

Vasopressin-mediated adrenocorticotropin release increases plasma cortisol concentrations during cardiopulmonary resuscitation.

ObjectiveVasopressin is a possible stimulus for both adrenocorticotropin (ACTH) and endothelin-1 release. The aim of this study was to compare plasma concentrations of ACTH, cortisol, and endothelin-1 after epinephrine or vasopressin administration in an experimental animal model of cardiopulmonary resuscitation (CPR). DesignProspective, randomized, controlled animal study. SettingA university research laboratory. SubjectsFourteen 12- to 14-wk-old domestic pigs. InterventionsAfter 4 mins of cardiac arrest and 3 mins of external chest compression, the pigs were randomly assigned to receive either 0.045 mg/kg epinephrine (n = 7) or 0.4 units/kg vasopressin (n = 7). At 5 mins after drug administration, defibrillation was attempted. Measurements and Main ResultsCoronary perfusion pressure, ACTH, cortisol, and endothelin-1 were measured before cardiocirculatory arrest, during CPR before drug administration, and at 90 secs and 5 mins after drug administration. Coronary perfusion pressure was comparable between groups. All seven animals in the vasopressin group survived, but only one pig in the epinephrine group survived (p = .005). ACTH and cortisol concentrations remained unchanged in epinephrine-treated animals, but increased significantly after vasopressin administration and were significantly higher than in epinephrine-treated animals 5 mins after drug administration. Endothelin-1 concentrations remained unchanged during the study period and were comparable between both groups. ConclusionsVasopressin is a potent stimulus for ACTH secretion, but does not trigger endothelin-1 release from vascular cells during cardiac arrest and CPR. The increased plasma cortisol concentrations caused by the enhanced ACTH release after vasopressin may be one factor contributing to the improved outcome repeatedly observed with vasopressin in animal models of CPR.

Forward blood flow during cardiopulmonary resuscitation in patients with severe accidental hypothermia: An echocardiographic study

Background: The mechanism responsible for the forward blood flow associated with external chest compression is still controversial. Evidence for both blood flow caused by direct cardiac compression and blood flow generated by a general increase in intrathoracic pressure has been found in experimental as well as clinical studies. No data are available concerning the mechanism causing forward blood flow in hypothermic patients undergoing cardiopulmonary resuscitation. Therefore, echocardiographic findings during external chest compression in seven hypothermic arrest victims are reported.

Intraosseous blood gases during hypothermia: correlation with arterial, mixed venous, and sagittal sinus blood.

ObjectiveEspecially in pediatric patients with severe hypothermia, intraosseous access may be more readily available than intravascular access during an early phase of treatment and therefore, may be helpful to optimize management. The purpose of this study was to determine whether intraosseous blood gases are comparable with arterial, mixed venous, and sagittal sinus blood gases during different degrees of hypothermia. DesignProspective, descriptive laboratory investigation using a porcine model. SettingUniversity hospital laboratory. SubjectsTwelve anesthetized, 12- to 16-wk-old domestic pigs weighing 30–35 kg. InterventionsVolume-controlled ventilated animals were instrumented with arterial, pulmonary artery, sagittal sinus, and 16-gauge intraosseous catheters. Blood samples were obtained from each site every 15 mins during surface cooling with crushed ice until mean ± sem core temperature decreased from 38.5 ± 0.1°C [101.3 ± 0.2°F] to 27 ± 0.5°C [80.5 ± 0.9°F] over 2 hrs. Measurements and Main ResultsIntraindividual correlation of Pco2 and pH values were determined as the difference (&Dgr;) between intraosseous and reference blood samples. With hypothermia, absolute values of Pco2 decreased and pH increased in samples from all sites. At 27°C, intraosseous − arterial &Dgr; Pco2 and &Dgr; pH (mean ± 95% confidence intervals) were 2.6 ± 10.6 torr [0.35 ± 1.4 kPa] and −0.11 ± 0.07 units; intraosseous − mixed venous were 0.4 ± 12.2 torr [0.05 ± 1.6 kPa] and −0.06 ± 0.08 units; and intraosseous − sagittal sinus were −7.3 ± 16 torr [−0.97 ± 2.1 kPa] and 0.001 ± 0.14 units, respectively. Intraosseous Pco2 was not comparable to end-tidal values (&Dgr;Pco2 17.4 ± 14.6 torr [2.3 ± 1.9 kPa]), and intraosseous lactate did not correlate with arterial, mixed venous, or sagittal sinus values. ConclusionsDuring hypothermia, intraosseous Pco2 values were predictable for mixed venous Pco2 and arterial Pco2. Intraosseous pH values also correlated with mixed venous and sagittal sinus blood samples. Accordingly, interpretation of blood gas values obtained from bone marrow aspirates may be helpful to adjust ventilation and optimize fluid and drug therapy during the early treatment of patients with severe hypothermia.

CASE 5--1997 Successful Resuscitation of a Patient With Severe Accidental Hypothermia and Prolonged Cardiocirculatory Arrest Using Cardiopulmonary Bypass

Case Presentation A poorly equipped 54-year-old man without climbing experience crossed a heavily crevassed glacier in the Austrian Alps. After a few minutes walk, he fell into a narrow crevasse about 4 meters deep. A rescue team was immediately summoned and arrived about 50 minutes later. The victim in the crevasse was conscious when the rescue team arrived but had slipped farther down the crevasse, by melting the ice around him with his body temperature. In the following hour, several efforts to reach the victim and to tie a rope around his body failed because the crevasse was too narrow. Meanwhile, the victim in the crevasse had become unresponsive, and occasional sighing remained the only visible sign of life. Finally, a very small member of the rescue team managed to fix a rope around the man, and the victim was removed from the crevasse within a few minutes. Rough handling of the patient during rescue and postural changes could not be totally avoided. Meanwhile, an emergency physician had arrived by helicopter. He immediately evaluated the patient removed from the crevasse. The patient was in deep coma, had no spontaneous breathing, no palpable pulses, and fixed, dilated, pupils. Electrocardiogram (ECG) demonstrated ventricular fibrillation. The patient was endotracheally intubated, artificially ventilated, and external chest compression was started. Tympanic temperature was measured and demonstrated severe accidental hypothermia with a body core temperature of 23°C. Therefore, the emergency physician decided to transport the patient immediately to this center by helicopter for rewarming with extracorporeal circulation (ECC). No medication was given on the scene or during air transport, and there were no attempts at defibrillation at the scene. After a 20-minute flight with ongoing cardiopulmonary

Hemodynamics and oxygen metabolism in the pig during long-term hypothermia: comparison of 2 pH strategies

The aim of this study was to investigate the influence of acid-base management (pH stat or alpha stat) on hemodynamics and oxygen metabolism during long-term hypothermia in the pig. Seventeen female pigs were anesthetized, slowly cooled to 28 degrees C with cooling mats and kept at this temperature for 36 h. Thereafter, slow rewarming was performed with inhalation of a 40 degrees C warm air/oxygen mixture and insulation. Eight of the 17 pigs were ventilated according to the pH stat strategy and 9 according to the alpha stat strategy. Both groups were compared 4 times each for hemodynamics and metabolism during cooling, hypothermia and rewarming. The 2 strategies showed no significant difference in cardiac output, heart rate or mean arterial pressure. The only difference in hemodynamics was observed in mean pulmonary artery pressure and pulmonary artery resistance during hypothermia, showing higher values in pH stat animals. As for oxygen metabolism, oxygen consumption during hypothermia was significantly higher in alpha stat animals. Long-term hypothermia with spontaneous circulation revealed significant differences in oxygen metabolism and pulmonary artery pressure as well as resistance between alpha and pH stat acid-base management. These differences may be of importance when using moderate hypothermia in a clinical or experimental setting.