Objectives: We hypothesized that progressive impairment in diastolic function during cardiopulmonary resuscitation (CPR) go before s evolution of the "stone heart" after failure of CPR We therefore measured sequential changes in left ventricular (LV) whirls and free-wall thickness of the heart during CPR in an experimental model Design: Prospective.

Objectives: We hypothesized that progressive impairment in diastolic function during cardiopulmonary resuscitation (CPR) go before s evolution of the "stone heart" after failure of CPR We therefore measured sequential changes in left ventricular (LV) whirls and free-wall thickness of the heart during CPR in an experimental model

Design: Prospective, observational animal study

Setting: Medical research laboratory in an university-affiliated research and educational institute.

Subjects: Domestic pigs.

Methods: Ventricular fibrillation (VF) was induced in 40 anesthetized male domestic pigs weighing between 38 kg and 43 kg After 4 min, 7 min, or 10 min of untreated VF electrical defibrillation was attempted. Failing to turn upside down VF in each instance, precordial compression at a rate of 80/min was begun coincident with mechanical ventilation. Coronary perfusion crushings (CPPs) were computed from the differences in time-coincident diastolic aortic and right atrial compressings Left ventricular (LV) systolic and diastolic ventricular books and thickness of the LV clear wall were estimated with transesophageal echocardiography. The knock volumes (SVs) were computed from the differences in decompression diastolic and compression systolic bulks Free-wall thickness was measured onward the hearts at autopsy.

Results: Significantly greater CPP were generated with the 4 min of untreated cardiac arrest. Progressive reductions in LV diastolic and SV and increases in LV free-wall thickness were documented with increasing duration of untreated VF A stone heart was confirmed at autopsy in each animal that failed resuscitative efforts. Correlations with indicator dilution orderly disposition and physical measurements at autopsy corresponded closely with the echocardiographic measurements. Conclusion: Progressive impairment in diastolic function terminates in a stone heart after extended intervals of cardiac arrest.

key-note words: cardiopulmonary resuscitation; left ventricular diastolic volume; left ventricular compliance; left ventricular wall thickness; stone heart

Abbreviations: CPP = coronary perfusion pressure; CPR = cardiopulmonary resuscitation; LV = left ventricular; PETC[Osub2] = end-tidal PC[Osub2]; SV = pat volume; VF = ventricular fibrillation

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present methods of closed-chest cardiac resuscitation squander effectiveness when the duration of cardiac arrest prior to attempted cardiac resuscitation increases to > 8 min. (12) Accordingly, the succes of now passing methods of closed-chest compression after protracted intervals of untreated cardiac arrest > 8 min is unconnected unrelated (3-5) The duration of cardiac arrest prior to the start of cardiopulmonary resuscitation (CPR) in human victims is the best single predictor of consequence (6,7)

In settings of regional myocardial ischemia befitting to coronary artery disease, decreases in ventricular compliance with myocardial stunning are well documented. (89) Decreases in ventricular compliance have also been documented during the global myocardial ischemia of cardiac arrest. (10) Reductions in left ventricular (LV) end-diastolic dimensionss would explain, at least in part, progressive decreases in thump volume (SV) during CPR. We therefore anticipated that decreases in LV chamber size with increases in wall thickness would correspond to the duration of untreated ventricular fibrillation (VF) and terminate in an anatomically "stony heart." In the near study, we validated transesophageal echocardiography in a porcine pattern of cardiac arrest to quantitate the dynamic changes in LV masss and wall thickness after untreated cardiac arrest for intervals of 4 min, 7 min, and 10 min and failed resuscitation. We subsequently related these to physical measurements at autopsy.

MATERIALS AND METHODS

Animals received humane care in compliance with principles of laboratory animal care formulated by the agency of the National Society for Medical Research, and care and use of laboratory animals as mandated from the Institute of Laboratory Animal Resources. The protocols were approved at the Institutional Animal Care and Use Committee of the Institute of Critical Care Medicine.

Animal Preparation

Male domestic pigs from a single source breeder weighing between 38 kg and 45 kg were investigated. Animals were fasted overnight object for free access to water. Anesthesia was initiated by means of IM injection of ketamine, 20 mg/kg followed through ear vein injection of sodium pentobarbital, 30 mg/kg Additional doses of sodium pentobarbital, 8 mg/kg were injected at intervals of approximately 1 h to maintain anesthesia. After endotracheal intubation, the animals received mechanical ventilation with a tidal book of 15 mL/kg and a peak come of 40 L/min of expanse air with the aid of a volume-controll ventilator (Model MA-1; Puritan Bennett; Carlsbad, CA). End-tidal PC[Osub2] (PETC[Osub2]) was monitored with a mainstream infrared analyzer (Model 01R-7101A; Nihon Kohden; Tokyo, Japan). Respiratory common occurrence was adjusted to maintain PETC[Osub2] between 35 mm Hg and 40 mm Hg prior to cardiac arrest without adjustment thereafter. Conventional ECG scalar limb leads were continuously recorded. The femoral artery and vein were surgically isolated in subordination to aseptic conditions. An 8F angiographic catheter (Model 6523; USCI, CR Bart; Billerica, MA) was advanced by means of the right femoral artery into the descending thoracic aorta for measurement of aortic urgency A multilumen, thermistor and balloon-tipped pulmonary artery catheter (41216-01; Abbott Critical Care; Anaheim, CA) was follow directed from the right femoral vein into the pulmonary artery. The atrial port was utilized for measurement of atrial crushing and for injection of thermal tracer. Positions of the catheters were guided by the agency of characteristic pressure pulse morphology and confirmed on fluoroscopy.

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