Hyperpolarized Polarized arrest as an alternative to Depolarized arrest Guo Wei Zhejiang University School of Medicine
Hyperpolarized / Polarized arrest as an alternative to Depolarized arrest Guo Wei Zhejiang University School of Medicine
Cardiac Arrest You have t值e right to remain silent.. e Rick London and Edith Snew
Elective cardiac arrest can be achieved by inducing depolarization,polarization, hyperpolrization or influencing calcium mechanisms
◆ Elective cardiac arrest can be achieved by inducing depolarization, polarization, hyperpolrization or influencing calcium mechanisms
Depolarized arrest Depolarized arrest:induced by elevating the extracellular potassium concentration,is currently the most commonly used technique. Hyperkalemia:usually within 15 to 40 mmol/L
Depolarized arrest Depolarized arrest: induced by elevating the extracellular potassium concentration, is currently the most commonly used technique. Hyperkalemia: usually within 15 to 40 mmol/L
Depolarized arrest ◆Hyperkalemia leads aitioeingpoionial,voitage-gatodNarchanets 150Ng to a depolarization of Na the membrane potential (Em)from 15 Na about-80 mv to around 50 my in 44 g￥9 cardiac tissue Nemst=+62mV
Depolarized arrest ◆ Hyperkalemia leads to a depolarization of the membrane potential (Em) from about - 80 mv to around - 50 mv in cardiac tissue
At this depolarized potential,the fast Na+ channels are inactivated (since the threshold is 70 to -65 mv,resulting in diastolic arrest However The reversal potential of the Na+-Ca 2+exchanger also occurs at-50 mv
◆ At this depolarized potential, the fast Na+ channels are inactivated (since the threshold is - 70 to - 65 mv, resulting in diastolic arrest ◆ However ,The reversal potential of the Na+– Ca 2+ exchanger also occurs at - 50 mv
The Role of Na/Ca2+Exchanger in Intracellular Ca2+Homeostasis Calmodulin CELL DEATH≤
Depolarized arrest Moreover,higher potassium concentrations, which depolarize the membrane further (to around -40 mv),would tend to activate the slow calcium channel and cause calcium influx into the myocyte Other ionic mechanisms also exist (such as Na- H exchange)
Depolarized arrest ◆ Moreover, higher potassium concentrations, which depolarize the membrane further (to around -40 mv), would tend to activate the slow calcium channel and cause calcium influx into the myocyte ◆ Other ionic mechanisms also exist (such as Na– H exchange)
hyperkalemia disadvantages Other ionic currents remain active Energy-dependent transmembrane pumps remain active in an attempt to correct these abnormal ionic gradients,depleting critical energy supplies High potassium-induced endothelial injury
hyperkalemia disadvantages ◆ Other ionic currents remain active ◆ Energy-dependent transmembrane pumps remain active in an attempt to correct these abnormal ionic gradients, depleting critical energy supplies ◆ High potassium-induced endothelial injury
A potentially beneficial alternative to hyperkalemic cardioplegia is to arrest the heart in a hyperpolarized or polarized state,which maintains the membrane potential of the arrested myocardium at or near to the resting membrane potential
◆ A potentially beneficial alternative to hyperkalemic cardioplegia is to arrest the heart in a hyperpolarized or polarized state, which maintains the membrane potential of the arrested myocardium at or near to the resting membrane potential