[Intraoperative calorimetry in aortic bifurcation reconstruction]. / Intraoperative Kalorimetrie bei Aortengabelrekonstruktion.

Oxygen uptake (VO2) and carbon dioxide elimination (VCO2) can be measured with an indirect calorimeter, this method is well established in routine monitoring of ICU patients to evaluate metabolic state as a reflection of stress. In various experimental studies it was demonstrated that anaesthetics can influence whole-body metabolism. The purpose of this study was to examine whether indirect calorimetry can be used intraoperatively during routine anaesthesia and whether presumable changes in metabolism can be detected immediately. Abdominal aortic cross-clamping changes circulation, nutritional supply of the lower extremities and thus VO2 and VCO2. We therefore used this operation for our study. METHOD. Eleven patients, mean age 64 years, undergoing reconstruction of the aortic bifurcation, were studied. After premedication with piritramid and atropine, total intravenous anaesthesia (TIVA) was performed with fentanyl and midazolam after an induction with thiopental. Patients were ventilated with a Servo-Ventilator 900 D and a constant FiO2 of 0.5, without N2O. Routine monitoring consisted of ECG, pulsoximetry, CVP and continuous AP. VO2 and VCO2 were measured with a Deltatrac (Datex), and data were registered every minute. For statistical evaluation we used a Wilcoxon-Ranksum test for matched pairs, p < 0.05 was considered significant. Data from specific time (5 min after intubation, 5 min before clamping; 5, 10 and 15 min after clamping, before declamping and 5 and 10 min after declamping and at the end of surgery) were calculated. In addition to absolute values, we compared the measured VO2 and VCO2 to baseline (5 min before clamping = MP2). RESULTS. Mean operating time was 139 min +/- 37; aortic cross-clamping time for the first extremity was 38 min and 55 min for the second. As expected, there was a significant decrease in VO2 (90% of baseline) and VCO2 (75% of baseline) during aortic cross-clamping. After declamping VO2 again rose to 110% of baseline, or to 103% for the second limb. VCO2 increased to only 90% and 82%, respectively. At the end of surgery VO2 reached baseline, whereas VCO2 remains at 83%. The respiratory quotient VCO2: VO2 was markedly reduced from 0.95 +/- 0.156 to 0.73 +/- 0.06 during surgery. The Deltatrac showed every change in VO2 without delay; changes in VCO2 seem to occur somewhat retarded. DISCUSSION. Aortic cross-clamping leads to a marked decrease in VO2 and VCO2 reflecting the temporary reduction in whole-body metabolism. Declamping results in a compensatory rise, especially in VO2. VCO2 seems to increase less after declamping, perhaps due to the CO2 pool of the organism or to a change in metabolism from carbohydrate to mainly fat oxidation. The results of this study demonstrate that indirect calorimetry can easily be performed during anaesthesia and surgery. Preconditions are a non-rebreathing system without airleak, constant FiO2 < 0.6 and no use of nitrous oxide.

Complete prosthetic valve thrombosis despite several thrombolytic treatments after tricuspid valve replacement.

We discuss the case of a 50-year-old man who underwent tricuspid valve replacement with a mechanical prosthesis (Duromedics) due to traumatic tricuspid insufficiency following a blunt chest trauma fifteen years previously. Despite correct anticoagulation therapy several events of prosthetic valve thrombosis occurred in the following years. The patient was treated four times by thrombolytic therapy. Finally, seven years after the initial operation the mechanical valve was replaced by a Carpentier-Edwards bioprosthesis because of complete blockage.

[Late valvular dysfunction after mechanical mitral valve replacement]. / Späte Klappendysfunktion nach mechanischem Mitralklappenersatz.

14 years after a Björk-Shiley prosthesis had been implanted because of combined mitral failure, a 68-year-old woman complained of progressive decrease of physical powers combined with apnoea, retrosternal feeling of pressure and tachycardiac atrial fibrillation. Five weeks later, onset of cardiac decompensation with dyspnoea at rest and signs of congested pulmonary circulation were noted. Echocardiography revealed stenosis of the mitral valve prosthesis. The patient was operated on two days later. It became evident that the patency of the prosthesis was greatly obstructed by connective tissue which had proliferated at the ventricular side. The original valve prosthesis was replaced by a St. Jude bi-leaflet valve. The likelihood of prosthesis dysfunction must always be considered if there is a deterioration in the patient's condition after a long uncomplicated postoperative course following cardiac valve replacement.

[Bioprosthesis degeneration in the aortic and mitral valve position. Results and problems from the cardiosurgical viewpoint]. / Bioprothesendegeneration in Aorten- und Mitralposition. Ergebnisse und Probleme aus kardiochirurgischer Sicht.

38 patients (20 men, 18 women) underwent reoperation between July 1989 to September 1992 because of degeneration of bioprosthetic valves implanted in aortic or/and mitral position. Retrospective analysis revealed a mean implantation time of 116.5 +/- 31.5 months for the bioprostheses (median 116). At reoperation 63.2% of them had a single valve replacement, 36.8% a more complex cardiac procedure (double or triple valve replacement, valve replacement and coronary bypass grafting). 50% (n = 9) of the reoperation cohort were symptomatic (NYHA III), 16 (42.1%) were serious symptomatic (NYHA IV). All deaths were NYHA IV preoperatively. Early mortality was 18.4% (n = 7). Mean age at the time of first operation was 51 +/- 10.7, mean age at reoperation was 60.5 +/- 10.6. There was a significantly longer aortic clamp time (AKT, p = 0.0005) and bypass time (BPT, p = 0.0000) compared to first operation, also a significantly longer BPT of the deads confronted with the survivors (p = 0.0075). Bioprosthetic valves in mitral position were significantly longer implanted (p = 0.0416) than in aortic position. But there was no difference in implantation time of commercially available Carpentier-Edwards- or Ionescu-Shiley grafts. At reoperation we changed more than 95% of the degenerated valves to mechanical devices--corresponding to international tendencies. We discuss the early tissue degeneration of bioprosthetic valves and their increasing problem during reoperation.

[Pacemaker implantation via a persistent left superior vena cava in atresia of the true superior vena cava]. / Schrittmacherimplantation über eine persistierende linke obere Hohlvene bei Atresie der eigentlichen Vena cava superior.

Implantation of a single-chamber pacemaker was planned in an 83-year-old woman with sick-sinus syndrome causing dizziness, bradycardia and tachycardia. After puncture of the right subclavian vein it proved impossible to advance a guide-wire into the superior vena cava, under fluoroscopy the wire always being seen to coil in the left subclavian vein and hence passing into a caudally directed vein. This vessel proved to be a persistent left superior vena cava (PLSVC) which connected to a markedly dilated coronary sinus (2 cm diameter) opening into the right atrium. An 85-cm electrode was then passed via the PLSVC and right atrium into the right ventricle without difficulty and was anchored in its apex. Echocardiography failed to reveal any further anomaly. Three-dimensional computed tomographic reconstruction established atresia or agenesis of the (right) superior vena cava. Normal pacemaker function freed the patient of all symptoms postoperatively.

Graft replacement of post-traumatic thoracic aortic aneurysm: results without bypass or shunting.

From 1986 to 1991 13 cases of post-traumatic thoracic aneurysm were treated at our department. All patients had apparent thoracic injury at the time of trauma, and their mean age was 35 years. The mean time between trauma and operation was 3 years and six patients were asymptomatic. In all patients the diagnosis was made by computed tomography and angiography and all post-traumatic thoracic aneurysms were located at the aortic isthmus. No spinal cord protection by bypass or shunting was used during surgery and the clamp-and-repair method with a mean clamping time of 38 min was used in all 13 patients. No renal or neurological complications were observed postoperatively and there were no hospital deaths. The data of 202 patients who had been operated upon for post-traumatic thoracic aneurysms since 1981 have been reviewed with regard to the relationship between spinal cord protection and the incidence of postoperative paraplegia. Different methods of spinal cord protection were used in 121 patients resulting in paraplegia rate of 1.6%. In 81 patients the clamp-and-repair method was used and no case of paraplegia was observed in this group.

[Impairment of the cognitive faculties and the reaction capability caused by midazolam despite reversal using flumazenil]. / Beeinträchtigung der kognitiven Fähigkeiten und des Reaktionsvermögens durch Midazolam trotz Reversion mit Flumazenil.

Imidazobenzodiazepine (flumazenil) is a specific competitive benzodiazepine antagonist. It antagonizes the sedative-hypnotic, anticonvulsive, anxiolytic and the muscle-relaxant effects of benzodiazepines. Its efficacy is prompt and complete. In several studies rebound phenomena have been observed. It was the aim of this randomized double blind study to investigate the efficacy of flumazenil by psychometric tests. The psychometric parameters we used were cognition and choice reaction time of 12 young and healthy volunteers. Three medication groups (A, B and C) were formed for this investigation. In a cross over design all volunteers had to be treated in each of these three medication groups. Between the groups we set a test-free interval of 7 days for every volunteer. In medication group A (midazolam/flumazenil) we applied 15 mg midazolam. Reversion was performed after 60 min with 0.5 mg flumazenil. In medication group B (placebo/flumazenil) midazolam was replaced by a physiological solution of sodium chloride. In medication group C (placebo/placebo) midazolam and flumazenil were substituted by a physiological solution of sodium chloride. For the investigation of the psychometric parameters (cognition and choice reaction time) we used the so called syndrome kurz test (SKT) and the decision reaction time measuring instrument ("Entscheidungs-Reaktionszeit-Messgerät"; ERM). Psychometric investigations were performed in all groups at intervals of 5, 30, 60, 90, 120, 180 and 240 min. Our results show that cognitive abilities remain impaired up to 60 min after the administration of flumazenil. Decision time and choice reaction time improved 120 min after administration of the antagonist. In our investigation neither rebound phenomena nor agonistic reactions of flumazenil were observed.(ABSTRACT TRUNCATED AT 250 WORDS)

[Plasma levels of atrial natriuretic peptide, cyclic guanosine monophosphate and renin following 7.5% NaCl + 6% hydroxyethyl starch or Ringer's lactate. A comparative study of 6 normal subjects]. / Plasmaspiegel des Atrialen-Natriuretischen-Peptids (ANP), des zyklischen-Guanosin-Mono-Phosphats (cGMP) sowie des Renins nach Gabe von 7.5% NaCl + 6% Hydroxyäthylstärke (HH) oder Ringer-Laktat (RL). Vergleichsstudie an 6 gesunden Probanden.

Small-volume resuscitation with hypertonic saline in combination with dextran appears to be very successful in experimental animals, where better results are achieved than in animals treated with a traditional infusion regime. This effect is apparently related to improved organ blood flow due to reflex vasodilatation. This reflex is based on the arrival of hypertonic solution in the pulmonary circulation. The expansion of intravascular volume would seem to be of secondary importance. Atrial natriuretic peptide (ANP) is released from secretory granules located in atrial cardiocytes. Atrial distention appears to be the predominant stimulus triggering ANP production. In addition to the natriuretic and diuretic effects, ANP leads to vasodilation, especially when vascular tone is elevated; the sympathetic reflex seems to be attenuated. Cyclic Guanosine Monophosphate (cGMP) is an intracellular messenger and is partly released by ANP in the membrane-bound form. Renin excretion is highly influenced by ANP. The object of this study was to evaluate the influence of a hypertonic solution on this hormonal regulatory system. METHOD. This study compared a hypertonic sodium chloride solution (7.5%) in combination with hydroxyethyl starch (6%) (HH) to Ringer's lactate (RL). Six healthy volunteers received 4 ml/kg HH and 1 week later 500 ml RL. The infusion was administered in 20 minutes via a central venous catheter 70 cm in length. Blood pressure, heart rate, hemoglobin (Hb), hematocrit (Hk), colloid osmotic pressure (COP), sodium (Na+), chloride (Cl-), and plasma osmolarity were measured before starting and 5 and 30 min following infusion. At the same times ANP, cGMP, and plasma renin were also determined. RESULTS. Both groups showed no change in blood pressure or heart rate. The decrease of Hb, Hk, and COP in the HH and RL groups indicated the expansion of circulating plasma volume. HH infusion caused significant increases in ANP and cGMP, whereas plasma renin declined significantly. After RL infusion, ANP and renin values were very similar to the HH group except in one volunteer, who showed an extreme increase in ANP (760 pg/ml) 5 min after HH infusion. cGMP did not increase significantly in the RL group. On comparison of the two groups, only a significant difference in plasma osmolarity and in sodium and chloride levels was noted. CONCLUSION. We found that hypertonic NaCl (7.5%) with HH was well tolerated. Release of ANP and cGMP after HH infusion in healthy volunteers was not as high as expected, and the vasodilatory effect of hypertonic solutions was not explained by ANP or cGMP release in this investigation.

[Possibilities for saving homologous blood in heart surgery]. / Möglichkeiten des Fremdblutsparens in der Herzchirurgie.

The risks of blood transfusion in context with the increasing number of operative open-heart procedures and the linked increased demand for blood products present a challenge to find methods of saving homologous blood. On the one hand there is increasingly less blood at the surgeon's disposal and on the other hand there is the threat of infectious complications with viruses of the HIV or the hepatitis group, as well as allergic reactions. At present we are developing the concept of blood saving as a programme which should work without excess demands on the staff and which can be adjusted to the needs of the individual patient. The programme consists of the following components: preoperative self donation, use of cell saver, acceptance of e relatively low hematocrit, medication to alter the coagulation process and blood-less priming.

[Differentiated enteral feeding in the post-aggression phase in polytrauma patients. Comparison of a high calorie nutritionally defined diet (whole protein high calorie diet) with a peptide diet]. / Differenzierte enterale Ernährung in der Postaggressionsphase bei Polytraumatisierten. Vergleich einer hochkalorischen nährstoffdefinierten Diät (WPHC-Diät) mit einer Peptid-Diät.

Two groups of 10 patients with an identical mean injury score (25 + 5) were treated from day 3 after injury until day 10 with a whole protein high caloric (WPHC) diet (group A) or with a peptide diet (PD) (group B). Intake of calories, protein, water, Na+ and K+ was measured daily as well as excretion of urine, Na+ and K+. Gastric reflux, bowel movement and plasma levels of Na+ and K+ were registered and the nitrogen balance and Na+/K+ quotient in urine were calculated daily. Clinically both diets were well tolerated, with low gastric reflux and no diarrhea. The calculated caloric demand could be covered in group A on day 7 post-injury (or day 4 of enteral nutrition) and in group B on day 11 post-injury (or day 7 of enteral nutrition). The caloric intake in group A remained significantly higher on days 4-10. There was no difference in nitrogen balance. Total enteral Na+ and fluid intake were significantly lower in group A, but some additional parenteral Na+ had to be given to keep plasma Na+ levels in the normal range. There was no difference in urine output between the 2 groups; therefore, there was a significant fluid retention in group B. Interestingly, the Na+/K+ quotient in urine was significantly higher in group A. The low Na+ intake might influence the back flow of interstitial edema in the 'flow phase'. This diet seems to be adequate, especially for the nutrition of burn patients and of patients with cardiac disease, and can cover the high caloric needs of polytraumatised patients within a few days.