Effects of Aminoglycoside Antibiotics on the Auditory Brainstem Response and Post Rotatory Nystagmus in Rats

Effects of three aminoglycoside antibiotics, amikacin (AMIK),tobramycin (TOB), and gentamicin (GM), on the auditory and vestibularfunctions were assessed in rats, the most frequently used speciesin toxicity studies. Chronic electrodes for auditory brainstemresponse (ABR) recording were implanted on the epidural surface,and those for post rotatory nystagmus (PRN) were implanted atthe nictitating membrane and the outer canthus. AMK, TOB, andGM were given intramuscularly twice daily for 3–4 weeksat a daily dose of 350, 150, and 100 mg/kg, respectively. Theamplitude of each wave of the ABR was decreased or disappearedin the groups treated with AMK, TOB, and GM. In the PRN, theduration of the nystagmus was decreased in the TOB group andcompletely lost in the GM group. No abnormality was observedin the PRN in the AMK group. These results were similar to thosereported in the ototoxicity studies of these drugs in guineapigs and indicate that ototoxicity can be evaluated in ratsas successfully as in guinea pigs by this procedure.     

Left ventricular assistance using a catheter-mounted coaxial flow pump (Hemopump) in a canine model of regional myocardial ischaemia

The global and regional effects of left ventricular circulatoryassistance were examined in dogs during acute myocardial infarctionusing a new coaxial flow device (Hemopump). In 12 dogs the leftanterior descending coronary artery was occluded for 4 h andsubsequently reperfused for 12 h. In six dogs, left ventricularassistance was started 90 min after coronary artery occlusionand maintained for several hours; six control animals receivedno circulatory support. Survival rate in the animals receivingmechanical support was 100% vs 0% in the control group. TheHemopump reduced left ventricular stroke work up to 80% andmaintained blood flows to the brain, kidneys, liver and intestinethroughout the experiment. Infarct size, expressed as a percentageof the left ventricle, however, was not mod(fied (12% in supportedanimals vs 13% in control dogs). Side effects of the coaxialfiowpump were thrombocytopaenia, occurring in all six dogs, andhaemolysis, which was demonstrated in one animal. It was concludedthat the Hemopump provides effective global and regional circulatorysupport in a canine model of severe cardiogenic shock. However,the value of left ventricular support to modify infarct sizecould not be demonstrated in this experimental model.