Biomedical subjects

S Kazmaier

Publications and source records attributed to S Kazmaier.

42 records · Page 3Linked to original sources

PubMed1995

Effects of endothelin-1 and IRL 1620 on myocardial contractility and myocardial energy metabolism.

In contrast to in vitro studies, experiments in intact animals could not detect a positive inotropic effect of endothelin-1 (ET-1). We presumed that the ET-induced direct positive inotropy is antagonized in vivo by an indirect cardiodepressant effect due to a mainly ETA-mediated and ET-induced coronary constriction, with consequent myocardial ischemia. To confirm this hypothesis we examined in thoracotomized rats the effects of a nonselective activation of ETA and ETB receptors by 1 nmol/kg ET-1 with and without the vasodilator adenosine (2.0 mg/kg/min), and the effects of a selective activation of ETB receptors by the ETB agonist IRL 1620 (2 nmol/kg) on myocardial contractility and energy metabolism (ATP, ADP, AMP). In addition to recordings in the intact circulation, isovolumic measurements (peak LVSP, peak dP/dtmax) were performed for quantification of myocardial contractility. ET-1 had no positive inotropic effect (peak dP/dtmax -2% vs. control, n.s.) due to a marked vasoconstriction with a consequent fall in the myocardial ATP content (-17%; p < 0.01). Adenosine antagonized the ET-induced vasoconstriction in part, normalized myocardial energy metabolism (ATP -7%), and thus unmasked the positive inotropic effect of ET-1 (peak dP/dtmax +20%; p < 0.01). Selective activation of ETB receptors by IRL 1620 had only a small vasoconstrictor effect, which did not produce myocardial ischemia (ATP + 10%; n.s.) and thus caused a positive inotropic effect in vivo (peak dP/dtmax +22%; p < 0.01). The positive inotropic effect of ET-1 is not detectable in vivo as its marked, mainly ETA-mediated, vaso- and coronary constriction causes myocardial ischemia that thus produces an indirect negative inotropic effect.

Adenosine Triphosphate↗

PubMed1994

Flow velocity measurements as an index of cerebral blood flow. Validity of transcranial Doppler sonographic monitoring during cardiac surgery.

BACKGROUND: Transcranial Doppler sonography is increasingly used to monitor changes in cerebral perfusion intraoperatively. However, little information is available about the validity of velocity measurements as an index of cerebral blood flow (CBF). The purpose of this study was to compare invasive and Doppler-derived measurements of cerebral hemodynamic variables during coronary artery bypass graft surgery. METHODS: In 15 male patients, measurements of CBF and middle cerebral artery flow velocity (VMCA) were performed before and after induction of fentanyl-midazolam anesthesia, during hypothermic cardiopulmonary bypass (CPB), and at the end of the surgical procedure. Transcranial Doppler sonography recordings of systolic, diastolic, and mean VMCA, and derived parameters such as pulsatility (PI) and resistance (RI) indexes were recorded from the proximal segment of the right middle cerebral artery. CBF was measured by the Kety-Schmidt inert gas saturation method with argon as a tracer. To facilitate comparisons of CBF and VMCA measurements, changes between consecutive measurements were expressed as percentage values. Calculations of cerebral perfusion pressure and cerebral vascular resistance (CVR) were based on jugular bulb pressure. The cerebral metabolic rate for oxygen was calculated from CBF and the arterial-cerebral venous oxygen content difference. RESULTS: Changes in mean VMCA paralleled changes in mean CBF except for hemodynamic changes associated with hypothermic CPB. At this stage of surgery, mean VMCA increased while actual CBF decreased. Separate analysis of the periods before and after CPB revealed a poor association between percentage changes in CBF and VMCA (r = 0.26, P = 0.36; r = 0.51, P = 0.06, respectively). Mean values of CVR, PI, and RI showed consistent changes after induction of anesthesia. After termination of CPB, mean CVR significantly decreased, whereas mean PI and RI remained virtually unchanged. Neither before nor after CPB was a clinically useful correlation found between percentage changes in PI, RI, and CVR (PI r = 0.28, P = 0.34; r = -0.47, P = 0.09, respectively; RI r = 0.16, P = 0.59; r = -0.53, P = 0.06, respectively). CONCLUSIONS: Hypothermic CPB seems to alter the relation between global CBF and flow velocity in basal cerebral arteries. Inconsistency in directional changes in CBF and VMCA at this stage of surgery might be attributable to changes in middle cerebral artery diameter, red blood cell velocity spectra, and regional flow distribution. Although changes in mean VMCA before and after CPB appear to parallel changes in mean CBF, individual responses of VMCA cannot reliably predict percentage changes in CBF. Furthermore, Doppler sonographic PI and RI cannot provide an approximation of changes in CVR during cardiac surgery.

Aged↗

PubMed1994

A rational basis for the measurement of free phenytoin concentration in critically ill trauma patients.

Phenytoin binding to serum proteins and factors influencing protein binding were investigated in 38 critically ill trauma patients. In 24% of these patients, the free fraction of phenytoin was < or = 10%, whereas in 76%, the free phenytoin fraction was increased > 10%--up to 24%. Nonantiepileptic comedication, sex, or age had no influence on phenytoin binding in any of the 38 patients. Elevated free phenytoin fraction was found in those with hypoalbuminemia and hepatic and renal impairments. In these patients, the free phenytoin fraction should be measured routinely.

Adolescent↗

PubMed1994

Effects of enoximone and R 80122, a new selective phosphodiesterase III inhibitor, on hemodynamics and myocardial energetics in patients with ischemic heart disease.

The present study was designed to compare the effects of enoximone and R 80122, a highly selective phosphodiesterase (PDE) III inhibitor, on left ventricular hemodynamics and myocardial blood flow and metabolism in patients with coronary artery disease. Twenty male, anesthetized patients, ASA physical status III, were studied before they underwent coronary artery bypass grafting (CABG) surgery. They were allocated randomly to receive either 0.3 mg/kg R 80122 (Group 1) or 1 mg/kg enoximone (Group 2) intravenously (IV). All patients were taking maintenance doses of either beta-receptor antagonists or calcium-channel-blocking drugs and nitrates. After receiving flunitrazepam, 2 mg orally, anesthesia was induced with fentanyl, midazolam, and pancuronium IV. Following control measurements after the induction of anesthesia, the PDE III inhibitor was infused over 2 min and measurements were repeated 5, 30, and 60 min after drug administration. There were no external stimuli to the patients during any of the measurement periods. R 80122 and enoximone decreased mean arterial pressure (MAP) by 20% and systemic vascular resistance (SVR) by 36% and 38%, respectively, while cardiac index (CI) increased by 27% and 30%, respectively. There were increases in heart rate (HR) by 10% and 19%, respectively, and in contractility (dp/dtmax) by 18% and 38%, respectively. Coronary perfusion pressure (CPP) decreased by 23% and 22%, respectively, and coronary vascular resistance (CVR) by 38% and 21%, respectively. Myocardial blood flow (MBF) and myocardial oxygen uptake (MVO2) increased in both groups, the increase in MBF being statistically significant (+34%) only in Group 1, whereas the changes in myocardial metabolism were not significant in either group.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1992

Acid-base management during hypothermic cardiopulmonary bypass does not affect cerebral metabolism but does affect blood flow and neurological outcome.

In order to compare the effects of blood-gas management on cerebral blood flow, metabolism and neurological outcome after hypothermic cardiopulmonary bypass (CPB) we have studied 65 patients undergoing aorto-coronary bypass surgery allocated randomly to either a pH-stat (temperature-corrected blood-gas management) or an alpha-stat (temperature-uncorrected blood-gas management) group. All patients were examined neurologically on the day before and the 7th day after operation. In 20 patients of the pH-stat group and in 15 patients of the alpha-stat group we measured cerebral blood flow (CBF), using the argon washin technique, and also cerebral oxygen (CMRO2) and glucose (CMRg) uptake. Measurements were performed in awake patients, after induction of anaesthesia with fentanyl, midazolam and pancuronium under normothermic conditions, during CPB at a venous blood temperature of 26 degrees C and at the end of surgery. Compared with postinduction values, hypothermia was associated with an 18% reduction in CBF and decreases in CMRO2 and CMRg of 61% and 60%, respectively, in the alpha-stat group. In the pH-stat group, CMRO2 and CMRg decreased also, by 58% and 74%, respectively, whereas CBF increased by 191%, indicating uncoupling of flow and metabolism. As there were no statistically significant differences between the metabolic variables in both groups, we conclude that acid-base management did not affect cerebral metabolism, despite its influence on blood flow. After rewarming, CBF and cerebral metabolism normalized independently of acid-base management during hypothermia. Nevertheless, neurological dysfunction occurred more often in the pH-stat group (P = 0.036).

Acid-Base Equilibrium↗

PubMed1990

[Extracardiac risk factors in heart surgery--significance of anesthesia].

Concerning perioperative risk, the choice of anaesthetic is of minor importance in cardiac surgery, whereas concomitant diseases of other organ systems and kind and degree of the cardiac disease can negatively influence the risk. The risk can be reduced by adequate preoperative diagnosis and pharmacotherapy, as well as by perioperative continuation of antianginal and antihypertensive drug treatment. The qualification of the anaesthetist and optimal cooperation between surgeon and anaesthetist are essential for the perioperative patient's management. Careful preoperative medical evaluation and adequate monitoring during operation and postoperative period are further cornerstones to improve outcome as far as the anaesthesiologist's duties are concerned. Old age itself does not enhance the risk, but operative mortality is enhanced in this group due to a higher frequency of multimorbidity and emergency operations, and to more advanced symptoms of heart disease in these patients. The long-term survival of geriatric patients, however, differs not substantially from the expected survivals in this age group, and their quality of life becomes improved to the same extent as in younger patients.

Anesthesia, General↗