Efficacy of a mephentermine-based product as a vasopressor and a cardiac performance enhancer when given intramuscularly to cattle.

The goal of this study was to confirm the vasopressor and cardiac effects of POTENAY® INJETÁVEL (POT), a mephentermine-based product, given to cattle with induced vascular/cardiac depression. Ten healthy Holstein cattle (206 ± 13 kg) followed a randomized-complete-block design (RCBD) utilizing crossover study design. Each animal randomly received (1 ml/25 kg, IM) of either POT (n = 10) or volume-matched placebo control (0.9%NaCl, CP, n = 10). A subset of animals (n = 5) received POT first (day 0) while the remaining (n = 5) received CP; after a six-day washout period, cattle received the opposite compound. Animals were anesthetized and catheterized for systemic/left ventricular hemodynamic monitoring. Myocardial dysfunction/hypotension was induced by increasing the end-tidal isoflurane concentration until arterial blood pressure was 20% lower than at baseline and remained stable. Once the animal was determined to be hypotensive and hemodynamically stable, steady-state hypotensive baseline data (BL2) were acquired, and treatment with either POT or CP was given. Data were acquired post-treatment at every 15 min for 90 min. POT improved cardiac output (+68 L/min, ±14%, p < 0.05), MAP (+14 mmHg, ±4%, p < 0.05), HR (+22 bpm, ±8%, p < 0.05), and peak rates of ventricular pressure change during both systole (dP/dtmax : +37 mmHg/s ±13%, p < 0.05) and diastole (dP/dtmin : +31 mmHg/s, ±7%, p < 0.05). No improvements were noted following placebo-control administration. Results indicate that POT improves cardiac performance and systemic hemodynamics in cattle with induced cardiovascular depression when given as single intramuscular injection.

Myocardial electrical impedance correlates with ischemic ECG ST-segment changes in humans.

Electrocardiogram (ECG) ST-segment changes are commonly used to diagnose myocardial ischemia. In this study we compared ST-segment changes with changes in myocardial electrical impedance (MEI)--an electrical parameter that also responses to ischemia--during off-pump coronary artery bypass graft (OPCABG) surgery of the left anterior descending coronary artery (LADa). We recorded MEI and ST-segment changes in eight patients during OPCABG surgery and compared the change in MEI that occurred when the LADa was occluded just prior to the beginning of the revascularization procedure with the ST-segment changes during the same period. Myocardial electrical impedance changes were directly and significantly correlated with ST-segment changes in our patient population. Our results indicate that MEI is equivalent to ST-segment changes as a measure of myocardial ischemia.