Biomedical subjects

Gunter Hempelmann

Publications and source records attributed to Gunter Hempelmann.

7 recordsLinked to original sources

PubMed1996

RETRACTED: The role of the protein C-thrombomodulin system and fibrinolysis during cardiovascular surgery: influence of acute preoperative plasmapheresis.

OBJECTIVES: To assess the benefits of withdrawn autologous plasma, the objective of this study was to investigate whether withdrawal of acutely performed platelet-rich or platelet-poor plasmapheresis allays changes in the protein C-thrombomodulin and fibrinolytic systems after retransfusion secondary to cardiopulmonary bypass (CPB). In addition, the study attempted to determine the influence of acute plasmapheresis (APP) on the protein C-thrombomodulin and fibrinolytic systems as well as on homologous blood consumption and perioperative blood loss in elective aortocoronary bypass patients. DESIGN: The investigation was scheduled as a prospective, randomized, unblinded study. SETTING: This single investigation was conducted in the Department of Anesthesiology and Intensive Care Medicine at a university in Germany. The study protocol was approved by the Ethics Committee of the hospital, and informed consent was obtained. PARTICIPANTS: Sixty male patients scheduled for elective coronary artery bypass grafting with extracorporeal circulation were included in the study. INTERVENTIONS: APP was performed between induction of anesthesia and incision, collecting either 10 mL/kg of autologous platelet-poor plasma (PPP patients, group 1; n = 20) or the same amount of platelet-rich plasma (PRP patients, group 2; n = 20). Patients of group 3 (n = 20) had no APP (control group). All patients were maintained on their usual regimen of cardiac drugs until the morning of surgery. To preserve hemodynamic stability and restore the intravascular oncotic pressure, the separated plasma was replaced by infusion of an equal amount of hydroxyethyl starch solution (HES) (6% HES, molecular weight 2 x 10(5), substitution rate 0.5%). In all operations, the same surgical procedure was chosen. For all patients, induction and maintenance of anesthesia were similar, consisting of weight-related doses of fentanyl (35 micrograms/kg), midazolam (0.65 mg/kg), and pancuronium bromide (0.15 mg/kg). The lungs of all patients were mechanically ventilated during the first 5 hours after the end of the operation. MEASUREMENTS AND MAIN RESULTS: All patients had serial coagulation studies including antithrombin (AT) III-activity, prekallikrein, factor XII, and immunologic tests such as thrombin-antithrombin III (TAT), fibrinopeptide A (FPA), protein C and S (PC and PS), thrombomodulin (TM), tissue-plasminogen-activator (t-PA), plasminogen-activator-inhibitor (PAI 1), fibrinopeptide B beta 15-42 (FPB beta 15-42), D-dimers, and hemoglobin and platelet counts determined intraoperatively and postoperatively. Chest tube drainage and transfusion requirements were recorded. APP had no negative effects on the quality of PPP and PRP plasma. The platelet count of the withdrawn plasma was 28 +/- 12 x 10(9)/L (PPP group) and 245 +/- 36 x 10(9)/L (PRP group). At the end of the operation (after retransfusion of autologous plasma) and on the morning of the first postoperative day, platelet counts were significantly higher (p > 0.05) in the PRP than in the PPP and control groups. Plasma concentrations of TAT and FPA increased (ranging from +185% to +340% from baseline values) and AT III-activity, PC, PS, and TM antigen decreased (ranging from -8% to -55% from baseline values) to a different extent for all three groups throughout CPB. t-PA-activity increased with a maximum at the end of CPB (PPP group, 6.9 +/- 1.5 IU/mL: PRP group, 3.8 +/- 0.8 IU/mL; control group, 10.9 +/- 2.8 IU/mL). Fibrin and fibrinogen degradation markers such as D-dimers and FPB beta 15 to 42 occurred in peak concentrations after neutralization of heparin by protamine. Only PRP patients showed baseline concentrations of coagulation parameters the next morning (p < 0.05). Total postoperative blood loss within the first 24 hours reached 482 +/- 273 mL (PRP group), 775 +/- 256 mL (PPP group), and 948 +/- 342 mL in the control group (p < 0.05).(ABSTRACT TRUNCATED)

Adult↗

PubMed1996

Changes in heart rate variability during induction of anesthesia with fentanyl and midazolam.

OBJECTIVE: The study was designed to evaluate changes in autonomic nervous system function during induction of anesthesia with fentanyl, midazolam, and pancuronium and to answer the question of dose-dependency of these effects. DESIGN: Prospective, randomized. SETTING: A university hospital. PARTICIPANTS: Forty consecutive cardiac surgical patients. INTERVENTIONS: Anesthesia was induced with fentanyl, midazolam, and pancuronium. The patients were assigned to four groups differing in dosages of fentanyl plus midazolam and speed of injection. Fentanyl, 7.5 micrograms/kg (group A), 12.5 micrograms/kg (group B), and 20.0 micrograms/kg (group C) plus midazolam, 0.075 mg/kg (group A), 0.125 mg/kg (group B), and 0.200 mg/kg (group C) were administered over 10 minutes; in group D, fentanyl, 7.5 micrograms/kg, and midazolam, 0.075 mg/kg, were administered within 1 minute. MEASUREMENTS AND MAIN RESULTS: Heart rate variability (HRV) was measured using parameters in the time domain and the frequency domain. The comparison of preinduction HRV with the intra-anesthetic epochs did not show significant differences with respect to heart rate, coefficient of variation, and root mean squared successive differences. Spectral analysis showed significant reductions of power in the vasomotor band (0.01 to 0.05 Hz) and the low-frequency band (0.05 to 0.15 Hz) in all groups. Power in the high-frequency band (0.15 to 0.50 Hz) decreased slightly, but this did not reach the significance level. A dose dependency of these changes was found in the low-frequency band only. CONCLUSIONS: Parameters of HRV suggest that induction with fentanyl, midazolam, and pancuronium decreases sympathetic but not parasympathetic autonomic system activity. The anesthetic induction technique's modulation of autonomic nervous system balance is better represented by means of spectral analysis than by analysis in the time domain. This modulation was largely independent of the doses administered and independent of the speed of injection.

Adult↗

PubMed1993

RETRACTED: Influence of acute preoperative plasmapheresis on platelet function in cardiac surgery.

Withdrawal of autologous plasma offers the possibility of improving patients' hemostasis and of reducing homologous blood consumption in cardiac surgery. The influence of acute, preoperatively performed plasmapheresis (APP) on platelet function was investigated in elective aortocoronary bypass patients subjected to APP producing either platelet-poor plasma (PPP; group 1; n = 12) or platelet-rich plasma (PRP; group 2; n = 12). APP-treated patients were randomly compared to patients without APP (control group; n = 12). Platelet aggregation induced by ADP (concentration 0.25, 0.5, 1.0, and 2.0 mumol/L), collagen (4 microL/mL), and epinephrine (25 mumol/L) was determined by the turbidometric method before and after APP, as well as before and after cardiopulmonary bypass (CPB) until the morning of the 1st postoperative day. APP had no negative effects on the patients' aggregation parameters (maximum aggregation and maximum gradient of aggregation). The platelet counts in the withdrawn plasma were 25 +/- 10 x 10(9)/L (PPP-group) and 250 +/- 30 x 10(9)/L (PRP-group). Platelet counts were highest in the PRP-group at the end of the operation (after retransfusion of autologous plasma). After CPB, maximum aggregation and maximum gradient of aggregation were reduced in all groups (ranging from -6% to -25% from baseline values). Retransfusion of autologous plasma improved platelet aggregability significantly only in the PRP-group. By the first postoperative day, maximum aggregation and maximum gradient of aggregation recovered in all groups (including the control group) or even exceeded baseline values (ranging from +8% to +42% from baseline values.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Coagulation Tests↗

PubMed1992

RETRACTED: Right ventricular function in patients with reduced left ventricular function undergoing myocardial revascularization.

Complex interrelationships exist between the right (RV) and the left ventricles (LV). Therefore, in 30 consecutive patients with reduced LV function (left ventricular ejection fraction [LVEF]) less than 40% undergoing myocardial revascularization, RV hemodynamics were studied from the beginning of anesthesia until the end of the operation. The data were compared with 30 consecutive patients with normal LVEF (greater than 70%). Ventricular function was assessed during left heart catheterization, which was carried out within 1 month of the operation. In addition to standard hemodynamic variables, RV ejection fraction (RVEF), RV end-diastolic volume (RVEDV), and RV end-systolic volume (RVESV) were monitored by the thermodilution technique. The two groups did not differ preoperatively with regard to RVEF, pressure (MAP, PAP, PCWP, RAP, RVPsyst, RVEDP), cardiac index (CI), and volume variables (RVESV, RVEDV). However, when the group with preoperatively reduced LVEF was subdivided into patients with severely reduced LVEF (less than 30%; n = 14; mean value 25.1%) and patients with moderately reduced LVEF (30%-40%; n = 16; mean value 37.3%), RVEF was significantly lower in the patients with a LVEF below 30% throughout the entire investigation period. RVEDV and RVESV were significantly higher in these patients. In conjunction with the lower RVEF and normal PAP, this suggests reduced RV function. It can be concluded that a severely reduced preoperative LVEF (less than 30%) may also be associated with impaired RV function.

Analysis of Variance↗

PubMed1992

RETRACTED: Age and right ventricular function during cardiac surgery.

Elderly patients undergoing cardiac surgery are reported to be at a higher risk for circulatory failure than younger patients, most likely because of ventricular decompensation. To assess the role of the right heart in these patients, right ventricular (RV) hemodynamics in 40 consecutive elderly patients (greater than 70 years; mean = 77.1 +/- 3.4 years) were compared with 40 consecutive younger patients (50 to 60 years; mean = 55.2 +/- 3.0 years) undergoing elective coronary artery bypass surgery. In addition to standard hemodynamic variables, RV ejection fraction (RVEF) and RV end-systolic and end-diastolic volumes (RVESV, RVEDV) were studied perioperatively using a thermodilution technique. None of the elderly patients died in the perioperative period. The course of RV function was comparable in both groups during the entire investigation period, but the absolute values of RVEF before the onset of cardiopulmonary bypass (CPB) were significantly higher in the younger patients (48.0 +/- 4.4%) than in the older patients (38.9 +/- 4.6%). RVEDV and RVESV were always higher in the older patients in the pre-bypass period than in the control group. None of the other hemodynamic parameters showed significant differences between the groups. Analysis of covariance showed no correlation between RV volume and pressure parameters. Inotropic support during and after termination of CPB was necessary more often in the older (epinephrine, 6.7 +/- 2.0 micrograms/min) than in the younger patients (epinephrine, 4.4 +/- 2.2 micrograms/min). It is concluded that older patients undergoing myocardial revascularization can have excellent results. However, they may be predisposed to right heart complications because of their reduced RV function.

Aged↗

PubMed1992

RETRACTED: Right ventricular function in patients with aortic stenosis undergoing aortic valve replacement.

The effects of aortic stenosis (AS) on right ventricular function during cardiac surgery are not fully understood. Forty patients undergoing aortic valve replacement with either a systolic transvalvular gradient of less than 100 mm Hg (82.1 +/- 5.5 mm Hg; group 1, n = 20) or greater than 120 mm Hg (131.1 +/- 6.9 mm Hg, group 2, n = 20) were investigated with regard to right ventricular function in the perioperative period. Right ventricular ejection fraction (RVEF), right ventricular end-systolic volume (RVESV), and right ventricular end-diastolic volume (RVEDV) were measured by means of the thermodilution technique. Before cardiopulmonary bypass (CPB), RVEF was significantly lower in group 2 patients (34% +/- 6%) than in group 1 (45% +/- 5%). After CPB, RVEF increased significantly in group 2 (28% +/- 4% to 49% +/- 5%), and no further differences were noted between the groups. In the patients with a higher systolic transvalvular gradient, RVEDV and RVESV were lower at the start of surgery, but increased after opening the pericardium. Cardiac index was also lower in these patients. Pericardiotomy resulted in a decrease in right ventricular end-systolic pressure (RVESP) only in the patients of group 2. In these patients more epinephrine was necessary to maintain stable hemodynamics during the post-bypass period. It is concluded that patients with AS are at risk of reduced right ventricular function when the systolic transvalvular pressure gradient is more than 120 mmHg. Knowledge of the complex interaction between the two sides of the heart may enable anesthesiologists to optimize management during the perioperative period.

Aged↗

PubMed1991

RETRACTED: Acute preoperative hemodilution in cardiac surgery: volume replacement with a hypertonic saline-hydroxyethyl starch solution.

Preoperative hemodilution (HD) is a recommended practice in cardiac surgery that conserves blood and reduces the complications of homologous blood transfusion. In 45 patients undergoing myocardial revascularization, HD was performed preoperatively. Withdrawn volume (10 mL/kg) was replaced either by a new hypertonic saline (HS) solution prepared in hydroxyethyl starch (HES) (2,400 mOsm/L, HS-HES group, n = 15) or by a standard low molecular weight hydroxyethyl starch solution (6% HES 200/0.5, HES group, n = 15) to maintain baseline PCWP (acute normovolemic hemodilution [ANH]). Fifteen comparable patients without HD served as controls. Significantly less HS-HES (210 +/- 20 mL) than HES 6% (890 +/- 90 mL) was necessary to sustain hemodynamics during HD. Stable cardiocirculatory conditions were obtained even after termination of bypass. Fluid balance during cardiopulmonary bypass as well as in the postoperative period was significantly lower in HS-HES-treated patients. With regard to hemodynamics, CI increased most in the HS-HES group (+36%), whereas systemic vascular resistance was lower in these patients. Right ventricular ejection fraction increased only in HS-HES patients (+15%). However, sodium concentration as well as osmolarity increased after volume replacement with HS-HES, without exceeding normal values. None of the patients suffered from organ failure. Pulmonary gas exchange (PaO2) was less compromised in the HS-HES patients. There were no renal function differences between the groups. In conclusion, HS solution prepared in HES is an attractive alternative for blood substitution in cardiac patients undergoing acute hemodilution for blood conservation.

Atrial Function, Right↗