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Biomedical subjects

P Neidhart

Publications and source records attributed to P Neidhart.

At least 19 recordsLinked to original sources
PubMed1999

Intra- and postoperative quality control in minimally invasive direct coronary artery bypass (MIDCAB) surgery.

The introduction of new techniques allowing direct coronary artery revascularisation without sternotomy and extracorporeal circulation--called Minimally (or less) Invasive Direct Coronary Artery Bypass grafting (MIDCAB)--has opened up interesting perspectives for the treatment of patients with limited coronary artery disease. However, like any newer surgical technique, this approach to myocardial revascularisation requires a critical appreciation of the results which may be obtained; when introducing the MIDCAB technique in our institution we developed a quality control protocol based on intraoperative as well as early and late postoperative parameters. This protocol is designed to detect every significant adverse event, exercise capacity and quality of life of our patients. Moreover, several invasive parameters have to be recorded in the protocol, such as intraoperative flow in the internal mammary artery conduit, the angiographic verification of anastomotic patency at one-year follow-up and determination of coronary flow reserve. The results of the first 5 patients observed up to one year postoperatively are presented: all anastomoses were patent and the flow within the internal mammary artery was 69 +/- 40 ml/min at one-year follow-up angiography; this compares very favourably with the flow measured at the end of the operation, which was 31 +/- 8 ml/min. This demonstrates very clearly that internal mammary artery flow is recruitable and usually significantly increases within the first months postoperatively. Coronary flow reserve was 3.4 +/- 1.1 (normal value > 2.5). The results obtained in this pilot study, which was designed to establish a quality control protocol, are very satisfactory and confirm previous experience that this technique may be offered to selected patients with appropriate coronary anatomy.

Coronary Artery Bypass↗
PubMed1999

Effects of unprocessed and processed cardiopulmonary bypass blood retransfused into patients after cardiac surgery.

BACKGROUND: The aim of this prospective study was to compare the effect of autologous unprocessed to processed residual cardiopulmonary bypass blood (CPB) on patients' laboratory and clinical parameters and outcome. METHODS: 20 patients undergoing elective coronary artery bypass surgery were randomized to receive either unprocessed CPB blood (control group) or processed CPB blood employing the Continuous AutoTransfusion System (CATS; Fresenius, Bad Homburg, Germany). We have shown that this method eliminated >93% of activated mediators. Serial laboratory parameters including complement activation, coagulation factors and the stimulation of IL-6 and IL-8 were compared with clinical side effects and patients' outcome. RESULTS: Compared to control patients, retransfusion of unprocessed CBP blood significantly increased heparin, free plasma hemoglobin and D-Dimers. Postoperatively, three patients in the control group and two patients in the CATS group required prolonged mechanical ventilation or developed infections associated respectively with elevated C3a (desArg) or IL-6 concentration. CONCLUSIONS: CATS-processing of CPB blood provided a high-quality red blood cell concentrate, resulting in a reduced load of retransfused activated mediators.

Blood Coagulation Factors↗
PubMed1998

[Conventional heart surgery with the fast-track-method: experiences from a pilot study].

Early release after cardiac surgery can be promoted by implementation of a standard protocol for accelerated perioperative and early postoperative care, with optimal education and support of the patient playing a key role. We report on our preliminary experience with 100 selected patients who underwent a "fast track" protocol following coronary artery bypass (n = 61), valve replacement or reconstruction (n = 34) or closure of an atrial septal defect (n = 5) between 1996 and 1998. Surgery was performed through a midline sternotomy using normothermic or mild hypothermic cardiopulmonary bypass. Patients undergoing cardiac surgery with less invasive techniques were excluded from this study. The following criteria had to be fulfilled for early hospital discharge: sinus rhythm, temperature below 37.5 degrees C, stable haematocrit around 0.30, uncomplicated wound healing and complete mobilisation including stair exercises. Mean duration of the operation was 137 +/- 24 minutes and mean intubation time was 4.5 +/- 3 hours. Mean duration of hospitalisation from the day of the operation was 4.9 +/- 2.1 days. There was no early or late mortality in this group of patients and only 2 patients had to be re-admitted on postoperative day 10 and 14 because of atrial fibrillation in one and a wound healing problem in the other. Accelerated recovery and early hospital discharge is highly attractive in selected patients; in helps to promote early cardiac rehabilitation and the costs of the procedure can be substantially reduced. According to our experience and the most recent literature, this approach does not expose patients to higher mortality or morbidity. In addition, fast-tracked patients have shown a higher level of satisfaction. Under optimal cooperation between surgery, anaesthesiology and intensive care unit, the fast-track protocol can be applied in approximately 30% of overall adult cardiac surgery patients.

Adult↗
PubMed1997

Deep accidental hypothermia and cardiac arrest--rewarming with forced air.

BACKGROUND: During the last two cold winters we have treated 5 severely hypothermic patients (temperature below 30 degrees C) with active external rewarming rather than with extracorporal circulation and heat exchanger. PATIENTS: Two patients were found in cardiac arrest, and 3 victims of mountain accidents suffered deep hypothermia without arrest. In one of them, ventricular fibrillation (VF) was converted successfully to a sinus rhythm at a core temperature of 25.9 degrees C. Both arrested patients developed an adequate hemodynamic state during resuscitation although they were at very low temperature. All the patients were warmed with a convective cover inflated with warm air of about 38 degrees C (Bair Hugger). The core temperature increased by approximately 1 degree C/h in all patients. During rewarming we observed neither an initial drop of the core temperature (afterdrop) nor cardiac arrhythmias. The outcome of all 5 patients was good without neurological sequelae. CONCLUSION: We conclude that external rewarming with forced air is a feasible alternative to cardiopulmonary bypass in severely hypothermic patients with electrical activity. This method can be used even in patients with VF because defibrillation can be successfully performed in deep hypothermia. Although after-drop during external rewarming is feared, we did not observe this phenomenon. Rewarming with forced air is inexpensive, easy to perform and direct access to the patient is possible at any time. It does not require heparinisation and can be used in hospitals where they do not have cardiopulmonary bypass facilities. Thus, this method is particularly useful in situations when the hypothermic patient cannot be transferred to a major medical center.

Accidents↗
PubMed1997

Qualitative assessment of blood washing with the continuous autologous transfusion system (CATS)

A number of different blood-processing methods can be used at the end of cardiopulmonary bypass (CPB) to improve the quality of autologous blood. They include centrifugation, hemofiltration and cell-washing. They differ in processing time required, cost of disposables and the quality of the processed autologous blood product. The newly developed continuous auto-transfusion system (CATS: Fresenius AG, Bad Homburg) uses a continuous cell-washing method. In a prospective study, the oxygenator blood of 10 patients was processed at the end of cardiac surgery with CATS and the quality of autologous blood before and after processing was compared. The processing volumes and the time required were recorded. The concentrations and elimination rates of blood parameters and waste products such as activated coagulation and complement products were measured. At the end of CPB a mean volume of 1,010 +/- 174 ml diluted oxygenator blood was processed and concentrated to 310 +/- 88 ml in 11.0 +/- 2.2 mins. Cellular elements such as erythrocytes and leucocytes were mostly retained and their concentration showed a significant increase after processing (250% and 210% respectively; p < 0.01). Thus, the blood processing with CATS resulted in an excellent hemoconcentration (hematocrit 62 +/- 3 vs. 24 +/- 4% before processing) with a consistent reproducibility. On the other hand, the CATS concentrate showed a significant loss of autologous plasma proteins. Likewise, all water soluble elements such as waste products are significantly lower in concentration after processing and, if calculated by quantity, they show a high elimination rate (> 93%). In conclusion, the continuous autologous transfusion system permits an automated, rapid and continuous processing of autologous blood yielding a standardised high quality erythrocyte concentrate.

Aged↗
PubMed1996

Preoperative inhibition of angiotensin-converting enzyme improves systemic and renal haemodynamic changes during aortic abdominal surgery.

We studied 22 patients undergoing aortic surgery, allocated randomly to receive, before induction of anaesthesia, a single i.v. dose of enalapril 50 micrograms kg-1 or saline. During infrarenal aortic cross-clamping, we observed similar reductions in oxygen uptake in the two groups, despite greater systemic oxygen delivery in enalapril-treated patients; angiotensin-converting enzyme inhibition prevented the reduction in cardiac output and attenuated the decrease in glomerular filtration. Changes in glomerular filtration secondary to aortic clamping were related positively to changes in renal plasma flow (r = 0.83 (saline group) and r = 0.65 (enalapril group)). Creatinine clearance on the first day after operation was significantly higher in the enalapril compared with the saline group. We conclude that enalapril pretreatment is effective in improving systemic oxygen delivery, renal plasma flow and glomerular filtration during aortic abdominal surgery.

Aged↗
PubMed1996

Long-term angiotensin-converting enzyme inhibitor treatment attenuates adrenergic responsiveness without altering hemodynamic control in patients undergoing cardiac surgery.

BACKGROUND: The sympathoadrenal and the renin-angiotensin systems are involved in blood pressure regulation and are known to be markedly activated during cardiac surgery. Because unexpected hypotensive events have been reported repeatedly during anesthesia in patients chronically treated with angiotensin-converting enzyme (ACE) inhibitors, the authors questioned whether renin-angiotensin system blockade would alter the hemodynamic control through attenuation of the endocrine response to surgery and/or through attenuation of the pressor effects of exogenous catecholamines. METHODS: Patients with preserved left ventricular function undergoing mitral valve replacement or coronary revascularization were divided into two groups according to preoperative drug therapy: patients receiving ACE inhibitors for at least 3 months (ACEI) group, n = 22) and those receiving other cardiovascular drug therapy (control group, n = 19). Anesthesia was induced using fentanyl and midazolam. Systemic hemodynamic variables were recorded before surgery, after anesthesia induction, during sternotomy, after aortic cross-clamping, after aortic unclamping, as well as after separation from cardiopulmonary bypass (CPB) and during skin closure. Blood was sampled repeatedly up to 24 h after surgery for hormone analysis. To test adrenergic responsiveness, incremental doses of norepinephrine were infused intravenously during hypothermic CPB and after separation from CPB. From the dose-response curves, pressor (defined as mean arterial pressure changes), and vasoconstrictor (defined as systemic vascular resistance changes) effects were analyzed, and the slopes and the dose of norepinephrine required to increase mean arterial pressure by 20% were calculated (PD(20)). RESULTS: At no time did the systemic hemodynamics and the need for vasopressor support differ between the two treatment groups. However, for anesthesia induction, significantly less fentanyl and midazolam were given in the ACEI group. Although plasma renin activity was significantly greater in the ACEI group throughout the whole 24-h study period, plasma concentrations of angiotensin II did not differ between the two groups. Similar changes in catecholamines angiotensin II, and plasma renin activity were found in the two groups in response to surgery and CPB. The pressor and constrictor effects of norepinephrine infusion were attenuated markedly in the ACEI group: the dose-response curves were shifted to the right and the slopes were decreased at the two study periods; PD(20) was significantly greater during hypothermic CPB (0.08 micro/kg in the ACEI group vs. 0.03 micro/kg in the control group; P < 0.05) and after separation from CPB (0.52 micro/kg in the ACEI group vs. 0.1 micro/kg in the control group; P < 0.05). In both groups, PD(20) was significantly less during hypothermic CPB than in the period immediately after CPB. CONCLUSIONS: Long-term ACE inhibitor treatment in patients with preserved left ventricular function alters neither the endocrine response nor the hemodynamic stability during cardiac surgery. However, a significantly attenuated adrenergic responsiveness associated with incomplete blockade of the plasma renin-angiotensin system supports the hypothesis that inhibition of angiotensin II generation and of bradykinin degradation within the vascular wall mediates some of the vasodilatory effects of ACE inhibitors.

Adult↗
PubMed1994

Dissection of the atrial septum following mitral valve surgery.

Interlayer dissection of the atrial septum resulting in the formation of a cavity developed after an attempted repair of a mitral paraprosthetic leak. Subsequent rupture of the cavity into both atria resulted in a small left-to-right shunt and significant left ventriculoatrial regurgitation. Misplaced stitches, aimed at obliterating the paraprosthetic leak, were the cause of the dissection. This case illustrates a previously unreported complication of mitral valve surgery and stresses the importance of proper exposure and handling of the mitral annulus.

Aged↗
PubMed1993

Effect of continuous positive airway pressure applied by face mask on right ventricular function after cardiac surgery.

The effect of respiratory therapy with continuous positive airway pressure (CPAP) on right ventricular function 24 hours after elective cardiac surgery was evaluated in patients with or without severe coronary artery disease. The first group included 10 patients following coronary artery bypass graft (CABG) surgery, and the second group included 10 patients following aortic valve replacement (AVR) without preexisting coronary artery disease. Patients of both groups had preoperative left ventricular ejection fractions above 40%. CPAP was applied by face mask at a flow rate of 20 L/min with 40% oxygen in nitrogen and with a positive end-expiratory pressure of 12 cmH2O. Right ventricular function was estimated at end-expiration by a fast-response thermodilution cardiac output catheter. The results demonstrate that in both groups of patients, CPAP did not significantly modify right ventricular indices, ejection fraction, end-systolic and end-diastolic volume indices, and stroke volume index, indicating that CPAP can safely be applied after elective cardiac surgery in patients with or without severe coronary artery disease and preoperative left ventricular ejection fractions above 40%. Furthermore, the concomitant postoperative intravenous infusion of nitroglycerin (to all 10 patients of the CABG group and to 4 patients of the AVR group) counteracted the expected beneficial effect of CPAP therapy on arterial oxygenation.

Adult↗
PubMed1992

Different effects of prostacyclin and phentolamine on delivery-dependent O2 consumption and skin microcirculation after cardiac surgery.

Inadequate tissue oxygen uptake autoregulation has been reported during the first hours after extracorporeal circulation for cardiac surgery. In the present study, we examined whether a dependence of oxygen consumption (VO2) on oxygen delivery (DO2) can be detected 24 hr after cardiac surgery using two different vasodilating agents. Cardiac output in triplicate was measured by thermodilution. Oxygen saturation of arterial and mixed venous blood was measured using a CO-oximeter. Oxygen consumption was assessed from the reverse Fick equation. In addition skin blood flow was assessed continuously by laser Doppler flowmetry. To investigate the VO2/DO2 relationship in 15 patients an increase in cardiac output and DO2 of at least 15% was achieved by systemic vasodilatation with iv prostacyclin (5-10 ng.kg-1.min-1) or phentolamine (5-10 g.kg-1.min-1). Infusion of phentolamine produced a 29 +/- 2% (mean +/- SE) increase in DO2 which was associated with a 20 +/- 6% increase in VO2. In contrast, prostacyclin produced a 22 +/- 3% increase in DO2 without change in VO2. Phentolamine did not alter skin microvascular blood flow, whereas prostacyclin increased skin microvascular blood flow by 33 +/- 3%. The results of the present study demonstrate a supply-dependency of VO2 in clinically stable patients 24 hr after cardiac surgery, suggesting the presence of an inadequate tissue O2 uptake autoregulation. The type of the vasodilator used to increase DO2 seems to play an important role in detecting such a supply-dependency of VO2, as well as changes of skin blood flow.

Adult↗
PubMed1989

Chest wall rigidity during fentanyl- and midazolam-fentanyl induction: ventilatory and haemodynamic effects.

In a double-blind randomised study, we examined if pretreatment with small doses of midazolam, given before anaesthesia induction with fentanyl, influences the occurrence of fentanyl-induced thoracic rigidity (FITR). At the same time, the effect of rigidity on the cardiovascular and respiratory system was assessed. Sixteen patients undergoing coronary artery bypass surgery were divided into two groups. The midazolam group (M) received 0.075 mg/kg midazolam i.v. and the placebo group (P) NaCl 0.9% 3 min before the start of fentanyl induction. During the induction period, FITR was assessed clinically on a 3-point scale. Haemodynamic and respiratory variables were collected before anaesthesia induction, at the end of the fentanyl infusion and 3 min after intubation. The incidence of FITR was high in both groups: 63% in Group M and 75% in Group P (n.s.); however, its severity was less in Group M. The appearance of rigidity affected the cardiovascular and the respiratory system: central venous and pulmonary capillary wedge pressures showed a sharp increase in patients with FITR accompanied by CO2 retention, due to an inability to ventilate these patients adequately. We conclude that small doses of midazolam do not prevent, but may attenuate, FITR and that the appearance of rigidity causes alterations of haemodynamic and respiratory variables during induction.

Clinical Trials as Topic↗
PubMed1988

[Low-dose midazolam. Effect on the induction doses of fentanyl and on hemodynamics in the coronary patient].

A study was carried out to see whether the administration of a small dose of midazolam determined a reduction of the dose of fentanyl necessary for induction of anaesthesia. Sixteen patients undergoing coronary artery bypass surgery were randomly allocated to either of two groups. Patients in group M received 0.075 mg.kg-1 midazolam intravenously 3 to 5 min prior to induction with fentanyl (5 micrograms.kg-1.min-1), whereas patients in group P only received placebo. The mean dose of fentanyl administered to obtain complete loss of reaction to a painful stimulus was 20 +/- 3 micrograms.kg-1 in group M and 21.5 +/- 2.5 micrograms.kg-1 in group P (NS). However the small dose of midazolam associated with fentanyl caused a significant drop in blood pressure by 20%. After the administration of pancuronium (0.15 mg.kg-1), the patients in group P showed a significant increase in heart rate (+ 14 b.min-1), accompanied by an increase in cardiac index (+0.45 l.min-1.m-2). Pretreatment with midazolam seemed to protect the patient from this undesirable reaction. It was concluded that induction with a combination of a small dose of midazolam and fentanyl did not lead to a reduction in the dose of fentanyl necessary to obtain profound analgesia. However, it gave rise to a haemodynamic pattern quite distinct from that seen during induction with fentanyl alone.

Anesthesia, General↗
PubMed1987

Mediastinal drainage after open heart surgery: comparison of infectious complications with two different systems.

Over the last years disposable systems have replaced in many hospitals the glass bottle drainage equipment used after cardiac surgery. The present study was designed to evaluate the incidence of postoperative infections and technical problems with 2 types of drainage systems. Positive microbial cultures and infectious complication as well as technical incidents were lower with the disposable equipment. The costs of the material alone, when infections are not taken into consideration, are slightly lower for the glass drainage system. We conclude from this survey that the incidence of superinfection of a closed, disposable system for mediastinal drainage is rare and smaller than with conventional glass bottles. When costs of different systems are compared, this consideration may be important.

Bacterial Infections↗