Effects of dopamine on porcine myocardial action potentials and contractions at 37 °C and 32 °C

Roscher, Roger; Arlock, Per; Sjöberg, Trygve; Steen, Stig

doi:10.1034/j.1399-6576.2001.045004421.x

Cited by 20 publications

(14 citation statements)

References 31 publications

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“…Cooling of the myocardium also impacts both upon the contractility and the pacemaker function of the heart. In vitro cooling of porcine myocardium to 32°C causes a prolongation of contraction and an increase in contractile force by almost 40% 9. The hypertension of mild hypothermia is therefore a product of tachycardia, increased contractility and increased systemic vascular resistance.…”

Section: Resultsmentioning

confidence: 99%

Critical care at extremes of temperature: effects on patients, staff and equipment

Hindle

Henning

2013

J R Army Med Corps

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Modern travel and military operations have led to a significant increase in the need to provide medical care in extreme climates. Presently, there are few data on what happens to the doctor, their drugs and equipment when exposed to these extremes. A review was undertaken to find out the effects of ‘extreme heat or cold’ on anaesthesia and critical care; in addition, subject matter experts were contacted directly. Both extreme heat and extreme cold can cause a marked physiological response in a critically ill patient and the doctor treating these patients may also suffer a decrement in both physical and mental functioning. Equipment can malfunction when exposed to extremes of temperature and should ideally be stored and operated in a climatically controlled environment. Many drugs have a narrow range of temperatures in which they remain useable though some have been shown to remain effective if exposed to extremes of temperature for a short period of time. All personnel embarking on an expedition to an extreme temperature zone should be of sufficient physical robustness and ideally should have a period of acclimatisation which may help mitigate against some of the physiological effects of exposure to extreme heat or extreme cold. Expedition planners should aim to provide climatic control for drugs and equipment and should have logistical plans for replenishment of drugs and medical evacuation of casualties.

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Section: Resultsmentioning

confidence: 99%

Critical care at extremes of temperature: effects on patients, staff and equipment

Hindle

Henning

2013

J R Army Med Corps

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“…[21][22][23] In both animal experiments and human studies, these effects are dependent on the degree and duration of the hypothermia 22 23 ; all these findings are from anaesthetised or sedated subjects. During mild hypothermia, however, there is evidence of both increased 24 and reduced 25 contractility. We found that the stroke volume did not change with mild hypothermia, therefore changes in CO were fully explained by changes in HR.…”

Section: Discussionmentioning

confidence: 99%

Cardiac output, pulmonary artery pressure, and patent ductus arteriosus during therapeutic cooling after global hypoxia-ischaemia

Fugelseth

2003

Archives of Disease in Childhood - Fetal and Neonatal Edition

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Objective: To assess by Doppler echocardiography the effects of 24 hours of whole body mild hypothermia compared with normothermia on cardiac output (CO), pulmonary artery pressure (PAP), and the presence of a persistent ductus arteriosus (PDA) after a global hypoxic-ischaemic insult in unsedated newborn animals. Design: Thirty five pigs (mean (SD) age 26.6 (12.1) hours and weight 1.6 (0.3) kg) were anaesthetised with halothane, mechanically ventilated, and subjected to a 45 minute global hypoxic-ischaemic insult. At the end of hypoxia, halothane was stopped; the pigs were randomised to either normathermia (39°C) or hypothermia (35°C) for 24 hours. Rewarming was carried out for 24-30 hours followed by 42 hours of normothermia. Unanaesthetised pigs were examined with a VingMed CFM 750 ultrasound scanner before and 3, 24, 30, and 48 hours after the hypoxic-ischaemic insult. Aortic valve diameter, forward peak flow velocities across the four valves, and the occurrence of a PDA were measured. Tricuspid regurgitation (TR) velocity was used to estimate the PAP. Stroke volume was calculated from the aortic flow. Results: Twelve animals (seven normothermic, five hypothermic) had a PDA on one or more examinations, which showed no association with cooling or severity of insult. There were no differences in stroke volume or TR velocity between the hypothermic and normothermic animals at any time point after the insult. CO was, however, 45% lower at the end of cooling in the subgroup of hypothermic pigs that had received a severe insult compared with the pigs with mild and moderate insults. CO and TR velocity were transiently increased three hours after the insult: 0.38 (0.08) v 0.42 (0.08) litres/min/kg (p = 0.007) for CO; 3.0 (0.42) v 3.4 (0.43) m/s (p < 0.0001) for TR velocity (values are mean (SD)). Conclusions: The introduction of mild hypothermia while the pigs were unsedated did not affect the incidence of PDA nor did it lead to any changes in MABP or PAP. Stroke volume was also unaffected by temperature, but hypothermic piglets subjected to a severe hypoxic-ischaemic insult had reduced CO because the heart rate was lower. Global hypoxia-ischaemia leads to similar transient increases in CO and estimated PAP in unsedated normothermic and hypothermic pigs. There were no signs of metabolic compromise in any subgroup, suggesting that 24 hours of mild hypothermia had no adverse cardiovascular effect. M ild hypothermia is currently one of the most promising clinically feasible "neural rescue therapies" for full term infants with hypoxic-ischaemic encephalopathy.1 In cardiac surgery, severe to moderate (20-32°C) hypothermia during the operation has been associated with adverse cardiovascular effects.2 Less attention has been given to the possible adverse physiological effects of mild-that is, rectal temperature of 33-35°C-hypothermia. Recently we showed that hypothermia after hypoxia in unsedated piglets increased cortisol levels significantly, and cortisol is a good marker of stress in pigs.3 In our pilot study of cardiova...

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“…Even though the time elapsed for delivery of 3 pulses with 30 ms duration would be shorter that the reported action potential duration recorded in vitro in swine ventricle at physiological temperatures (> 100 ms; Roscher et al, 2001), it is possible that the in vivo conditions, such as transient myocardial ischemia and increased catecholamine release, resulting from the interruption of cardiac pumping during VF, may have resulted in action potential shortening (Christé et al, 2006;Hoeker et al, 2014). In this case, it is likely that defibrillatory pulses would reach some cells during the relative refractory period (vulnerable period), which would favor arrhythmia reinitiation (Corbisiero et al, 1999), thus masking or even reverting the beneficial effect of multidirectional defibrillation.…”

Section: Discussionmentioning

confidence: 99%

“…Pulse transformers (TP-1:1/4T, Thornton, Vinhedo, SP, Brazil) were used with chopped pulses to ensure that switching was triggered, and to isolate the high-voltage switching circuit from the low-voltage control circuit. The discharge switching circuit (one for each output, Figure 5a) was implemented by using bidirectional thyristors (triodes) for alternating current (TRIAC 226M, Power Innov., Inc., Lindon, UT, USA) sufficiently fast for delivery of up to 3 shocks within 60 ms (Figure 5b, c), i.e., in a shorter period than the duration of the absolute refractory period of action potential in the swine ventricle (Roscher et al, 2001). This ensures that a cardiac myocyte excited by one of the shocks will not be reexcited by the subsequent stimulus.…”

Section: The Multidirectional Defibrillatormentioning

confidence: 99%

System for open-chest, multidirectional electrical defibrillation

et al. 2016

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Introduction: Cardiomyocytes are more sensitive to stimulatory electrical fields when the latter are applied longitudinally to the cell major axis. In the whole heart, cells have different spatial orientations, which may limit the effectiveness of conventional electrical defibrillation (i.e., shock delivery in a single direction). This article describes the constructive aspects of a portable system for rapidly-switching, multidirectional stimulus delivery, composed of an electrical defibrillator and multielectrode-bearing paddles for direct cardiac defibrillation. Methods:The defibrillator delivers monophasic, truncated monoexponential waveforms with energy up to 7.3 J. Upon selection of the defibrillation modality (unidirectional or multidirectional), shock delivery is triggered through 1 or 3 outputs. In the latter case, triggering is sequentially switched to the outputs, without interval or temporal overlap. Each paddle contains 3 electrodes that define shock pathways spaced by 60°. The system was tested in vivo for reversal of experimentally-induced ventricular fibrillation in healthy swine, using 30-and 20-ms long shocks (N= 4 in each group). Results: The defibrillator delivers identical stimulus waveforms through all outputs in both stimulation modalities. In all animals, successful defibrillation required lower shock energy when 20 ms-long stimuli were applied in 3 directions, compared to a single direction. However, performance was poorer with multidirectional defibrillation for 30 ms-long shocks. Conclusion: The delivery of identical shock waveforms allowed confirmation that multidirectional defibrillation can promote restoration of sinus rhythm with lower shock energy, which may reduce myocardial electrical damage during defibrillation. Nevertheless, increase in shock duration greatly impairs the effectiveness of this defibrillation modality.

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Effects of dopamine on porcine myocardial action potentials and contractions at 37 °C and 32 °C

Abstract: Cooling to 32 degrees C significantly prolongs the myocardial action potential and the contraction duration. Dopamine increases the contractile force and prolongs the action potential both at 37 degrees C and at 32 degrees C.

Cited by 20 publications

References 31 publications

Critical care at extremes of temperature: effects on patients, staff and equipment

Critical care at extremes of temperature: effects on patients, staff and equipment

Cardiac output, pulmonary artery pressure, and patent ductus arteriosus during therapeutic cooling after global hypoxia-ischaemia

System for open-chest, multidirectional electrical defibrillation

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