Myocardial electrophysiological and mechanical changes caused by moderate hypothermia-A clinical study.

Moderate hypothermia has been used to improve outcomes in comatose out-of-hospital cardiac arrest survivors during the past two decades, although the effects remain controversial. We have recently shown in an experimental study that myocardial electrophysiological and mechanical relationships were altered during moderate hypothermia. Electromechanical window positivity increased, and electrical dispersion of repolarization decreased, both of which are changes associated with decreased arrhythmogenicity in clinical conditions. Mechanical dispersion, a parameter also linked to arrhythmic risk, remained unaltered. Whether corresponding electrophysiological and mechanical changes occur in humans during moderate hypothermia, has not been previously explored. Twenty patients with normal left ventricular function were included. Measurements were obtained at 36 and 32°C prior to ascending aortic repair while on partial cardiopulmonary bypass and at 36°C after repair. Registrations were performed in the presence of both spontaneous and comparable paced heart rate during standardized loading conditions. The following electrical and mechanical parameters were explored: (1) Electromechanical window, measured as time difference between mechanical and electrical systole, (2) dispersion of repolarization from ECG T-wave, and (3) mechanical dispersion, measured as segmental variation in time to peak echocardiographic strain. At moderate hypothermia, mechanical systolic prolongation (425 ± 43-588 ± 67 ms, p < 0.001) exceeded electrical systolic prolongation (397 ± 49-497 ± 79 ms, p < 0.001), whereby, electromechanical window positivity increased (29 ± 30-86 ± 50 ms, p < 0.001). Dispersion of repolarization and mechanical dispersion remained unchanged. Corresponding electrophysiological and mechanical relationships were present at comparable paced heart rates. After rewarming, the increased electromechanical window was reversed in the presence of both spontaneous and paced heart rates. Moderate hypothermia increased electromechanical window positivity, while dispersion of repolarization and mechanical dispersion remained unchanged. This impact of hypothermia may be clinically relevant for selected groups of patients after cardiac arrest.

Left Ventricular Function Changes Induced by Moderate Hypothermia Are Rapidly Reversed After Rewarming-A Clinical Study.

OBJECTIVES: Targeted temperature management (32-36°C) is used for neuroprotection in cardiac arrest survivors. The isolated effects of hypothermia on myocardial function, as used in clinical practice, remain unclear. Based on experimental results, we hypothesized that hypothermia would reversibly impair diastolic function with less tolerance to increased heart rate in patients with uninsulted hearts. DESIGN: Prospective clinical study, from June 2015 to May 2018. SETTING: Cardiothoracic surgery operation room, Oslo University Hospital. PATIENTS: Twenty patients with left ventricular ejection fraction greater than 55%, undergoing ascending aorta graft-replacement connected to cardiopulmonary bypass were included. INTERVENTIONS: Left ventricular function was assessed during reduced cardiopulmonary bypass support at 36°C, 32°C prior to graft-replacement, and at 36°C postsurgery. Electrocardiogram, hemodynamic, and echocardiographic recordings were made at spontaneous heart rate and 90 beats per minute at comparable loading conditions. MEASUREMENTS AND MAIN RESULTS: Hypothermia decreased spontaneous heart rate, and R-R interval was prolonged (862 ± 170 to 1,156 ± 254 ms, p < 0.001). Although systolic and diastolic fractions of R-R interval were preserved (0.43 ± 0.07 and 0.57 ± 0.07), isovolumic relaxation time increased and diastolic filling time was shortened. Filling pattern changed from early to late filling. Systolic function was preserved with unchanged myocardial strain and stroke volume index, but cardiac index was reduced with maintained mixed venous oxygen saturation. At increased heart rate, systolic fraction exceeded diastolic fraction (0.53 ± 0.05 and 0.47 ± 0.05) with diastolic impairment. Strain and stroke volume index were reduced, the latter to 65% of stroke volume index at spontaneous heart rate. Cardiac index decreased, but mixed venous oxygen saturation was maintained. After rewarming, myocardial function was restored. CONCLUSIONS: In patients with normal left ventricular function, hypothermia impaired diastolic function. At increased heart rate, systolic function was subsequently reduced due to impeded filling. Changes in left ventricular function were rapidly reversed after rewarming.

Open chest and pericardium facilitate transpulmonary passage of venous air emboli.

BACKGROUND: Transpulmonary passage of air emboli can lead to fatal brain- and myocardial infarctions. We studied whether pigs with open chest and pericardium had a greater transpulmonary passage of venous air emboli than pigs with closed thorax. METHODS: We allocated pigs with verified closed foramen ovale to venous air infusion with either open chest with sternotomy and opening of the pleura and pericardium (n = 8) or closed thorax (n = 16). All pigs received a five-hour intravenous infusion of ambient air, starting at 4-6 mL/kg/h and increased by 2 mL/kg/h each hour. We assessed transpulmonary air passage by transesophageal M-mode echocardiography and present the results as median with inter-quartile range (IQR). RESULTS: Transpulmonary air passage occurred in all pigs with open chest and pericardium and in nine pigs with closed thorax (56%). Compared to pigs with closed thorax, pigs with open chest and pericardium had a shorter to air passage (10 minutes (5-16) vs. 120 minutes (44-212), P < .0001), a smaller volume of infused air at the time of transpulmonary passage (12 mL (10-23) vs.170 mL (107-494), P < .0001), shorter time to death (122 minutes (48-185) vs 263 minutes (248-300, P = .0005) and a smaller volume of infused air at the time of death (264 mL (53-466) vs 727 mL (564-968), P = .001). In pigs with open chest and, infused air and time to death correlated strongly (r = 0.95, P = .001). CONCLUSION: Open chest and pericardium facilitated the transpulmonary passage of intravenously infused air in pigs.

Changes in left ventricular electromechanical relations during targeted hypothermia.

BACKGROUND: Targeted hypothermia, as used after cardiac arrest, increases electrical and mechanical systolic duration. Differences in duration of electrical and mechanical systole are correlated to ventricular arrhythmias. The electromechanical window (EMW) becomes negative when the electrical systole outlasts the mechanical systole. Prolonged electrical systole corresponds to prolonged QT interval, and is associated with increased dispersion of repolarization and mechanical dispersion. These three factors predispose for arrhythmias. The electromechanical relations during targeted hypothermia are unknown. We wanted to explore the electromechanical relations during hypothermia at 33 °C. We hypothesized that targeted hypothermia would increase electrical and mechanical systolic duration without more profound EMW negativity, nor an increase in dispersion of repolarization and mechanical dispersion. METHODS: In a porcine model (n = 14), we registered electrocardiogram (ECG) and echocardiographic recordings during 38 °C and 33 °C, at spontaneous and atrial paced heart rate 100 beats/min. EMW was calculated by subtracting electrical systole; QT interval, from the corresponding mechanical systole; QRS onset to aortic valve closure. Dispersion of repolarization was measured as time from peak to end of the ECG T wave. Mechanical dispersion was calculated by strain echocardiography as standard deviation of time to peak strain. RESULTS: Electrical systole increased during hypothermia at spontaneous heart rate (p < 0.001) and heart rate 100 beats/min (p = 0.005). Mechanical systolic duration was prolonged and outlasted electrical systole independently of heart rate (p < 0.001). EMW changed from negative to positive value (- 20 ± 19 to 27 ± 34 ms, p = 0.001). The positivity was even more pronounced at heart rate 100 beats/min (- 25 ± 26 to 41 ± 18 ms, p < 0.001). Dispersion of repolarization decreased (p = 0.027 and p = 0.003), while mechanical dispersion did not differ (p = 0.078 and p = 0.297). CONCLUSION: Targeted hypothermia increased electrical and mechanical systolic duration, the electromechanical window became positive, dispersion of repolarization was slightly reduced and mechanical dispersion was unchanged. These alterations may have clinical importance. Further clinical studies are required to clarify whether corresponding electromechanical alterations are accommodating in humans.

Persons injured in the 2011 terror attacks in Norway - Relationship between post-traumatic stress symptoms, emotional distress, fatigue, sleep, and pain outcomes, and medical and psychosocial factors.

Purpose: The main aim was to assess long-term post-traumatic stress symptoms, emotional distress, fatigue, sleep disturbances and pain in individuals hospitalized with physical injuries after two terror attacks in Oslo in 2011, approximately three years after the events. A secondary aim was to explore the relationship between these outcomes and medical and psychosocial factors.Materials and methods: Thirty of 43 potential persons participated. Injury characteristics were collected from medical charts. Level of post-traumatic stress, emotional distress, fatigue, sleep disturbances and pain was assessed and the association with injury severity, resilience, optimism, neuroticism and extroversion, and perceived access to social support was explored.Results: Nine of 30 met criteria for full or partial PTSD, and 14 of 30 displayed clinical levels of emotional distress. Fifteen reported moderate to severe fatigue, and 16 said sleep disturbances affected their daily life. Twelve indicated that pain affected daily activities and work ability, and 15 that pain affected their quality of life. I Resilience, optimism, neuroticism, and perceived social support, were associated with outcomes, but injury severity was not. When controlling for pain, many of the psychosocial variables failed to reach significance.Conclusions: Injury severity was not associated with outcomes. On the other hand, psychosocial factors were, but seemed to be influenced by pain.Implications for rehabilitationPersons who have obtained physical injuries under extreme psychological conditions such as terror, are at high risk of poor long-term outcomes, and will often be in need of comprehensive interdisciplinary rehabilitation services.Psychological outcomes are not associated with severity of physical injury, but premorbid and current psychological variables such as resilience, optimism, personality, and access to social support are highly associated with long-term outcome.Longstanding pain seems to diminish or weaken the role of protective psychological factors and should be addressed in the rehabilitation context.

Chronic pain among the hospitalized patients after the 22 July 2011 terror attacks in Oslo and at Utøya Island.

BACKGROUND: On 22 July 2011, 48 people were hospitalized due to physical injuries from gun shots or explosion, following 2 terror attacks in the Oslo area, Norway. In this study, we have investigated the occurrence of chronic pain, the severity and consequences of chronic pain in these patients, 3 to 4 years after the incidents. METHODS: Totally 43 eligible terror trauma patients were invited to participate in the study, 30 patients were included. They underwent a consultation with a psychologist and a physician; containing psychological assessment, neuropsychological screening, a standardized clinical interview, medical examination, and a pain protocol. RESULTS: In 18 (60%) the injury was severe, as defined by New Injury Severity Score > 15. Twenty-four patients (80%) reported injury-related chronic pain after the trauma, in 22 with consequences on daily life. Analgesics were used by 20 patients, including 5 in need of opioids. Ten patients had unmet needs of further specialist pain care. In 12 patients, the average pain score last week was above three on a 0-10 Numeric Rating Scale. In these patients, clinical signs of neuropathic pain were evident in 10, as tested by the Douleur Neuropathique score. There were significant correlations (P < 0.05) between severity of chronic pain and presence of post-traumatic stress symptoms, reduced quality of life, reduced psychosocial and physical function; but no correlation with pre-injury patient characteristics or the degree of physical injury. CONCLUSION: Chronic pain was frequent and significant, irrespective of injury severity, in these patients who obtained their physical injuries under extreme psychological conditions.

Clinical characteristics and physical functioning in persons hospitalized following the Norwegian terror attacks in July 2011: A follow up study.

OBJECTIVE: To describe the clinical characteristics and physical functioning in persons hospitalized after 2 terror attacks in Norway in 2011. DESIGN: Cross-sectional study with retrospective acute medical data. SUBJECTS: Surviving persons hospitalized with physical injuries. METHODS: Medical and psychological assessments 3-4 years after injury, with data on injury type and severity collected from medical records. RESULTS: A total of 30 out of 43 potential subjects participated (19 women, 11 men; age range 17-71 years (median 23 years)). Eighteen participants had suffered a severe injury, with New Injury Severity Scale (NISS) scores > 15. All body parts were affected. The number of surgical procedures ranged from 0 to 22 (median 3), and days in intensive care ranged from 0 to 59 (median 2.5), of which 16 had more than 24 h intensive care. Three to 4 years later, a majority of the participants had a broad spectrum of somatic and psychological problems and reduced physical functioning. Two-thirds of the participants reported their physical health to be unsatisfactory, and continuous need for healthcare and unmet needs were identified for all except 4 of the participants. CONCLUSION: Persons hospitalized following a terror attack experience a broad spectrum of somatic and psychological problems and need long-term physical and psychological follow-up. This study indicates specific needs for rehabilitation after injuries acquired under psychological traumatic circumstances.