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Biomedical subjects

M Tönz

Publications and source records attributed to M Tönz.

At least 19 recordsLinked to original sources
PubMed2001

Fluid resuscitation in infantile hypertrophic pyloric stenosis.

UNLABELLED: The purpose of this analysis was to investigate biochemical disturbances at presentation and initial fluid resuscitation before surgery in infantile pyloric stenosis. The charts of 139 consecutive infants (113 boys and 26 girls) between 7 d and 20 wk of age with hypertrophic pyloric stenosis were reviewed. The infants were treated at the Department of Pediatric Surgery, University of Bern, Switzerland, in the period between 1987 and 1997. A trend towards hypokalaemia (13 of the 139 patients), hypochloraemia (39 patients) and especially metabolic alkalosis (98 patients) was frequently noted on admission. In 84 patients, data on fluid management and on circulating sodium, potassium, chloride and the acid-base balance immediately before surgery were also available. In these patients a significant correlation was found between the parenteral chloride dose given for fluid repair (y = 0.310 x; r = 0.54; p < 0.001) and the changes in plasma bicarbonate. The equation indicates that a chloride dose of 10 mmol/kg body weight is required to reduce plasma bicarbonate on average by 3 mmol/. CONCLUSION: Since assessment of the fluid volume stated by physical examination and history is inaccurate in infants with vomiting, the severity of metabolic alkalosis helps to define the amount of fluid required for repair.

Alkalosis↗
PubMed2000

Antibiotic prophylaxis for appendectomy in children: critical appraisal.

Prophylactic antibiotics are widely used during surgery, above all for clean-contaminated or contaminated procedures. Because factors other than the degree of contamination play a critical role in regard to postoperative infectious complications, it is not evident that recommendations for antibiotic prophylaxis for an adult population can be transferred to children. The aim of the study was to analyze the incidence of postoperative infections in children undergoing appendectomy for suspected appendicitis to evaluate critically the effectiveness of prophylaxis. The charts of all children undergoing appendectomy between 1988 and 1998 were analyzed. In general, appendectomies were performed without antimicrobial prophylaxis. If a perforated appendicitis was found at operation, antibiotics were given intraoperatively. Postoperative infectious complications were defined as wound infections, intraabdominal infections, or prolonged postoperative pyrexia. During the study period of 10 years, 954 patients underwent appendectomy. In 24% of cases the appendix was perforated. Patients received prophylactic antibiotics at the surgeon's discretion. These patients were excluded from further analysis. Among those with non-perforated appendicitis (n = 633), Infectious complications occurred in 19 (3%). Analyzing subgroups according to histologic diagnosis, the incidence was 4.2% (16/382) for gangrenous appendicitis and 1.2% (3/251) for simple appendicitis or normal appendix. These figures are clearly lower than those reported from an adult population, indicating that results from adults cannot a priori be transferred to children, and that general recommendations concerning antimicrobial prophylaxis must be considered carefully for this age group.

Antibiotic Prophylaxis↗
PubMed2000

Is there a place for thoracoscopic debridement in the treatment of empyema in children?

BACKGROUND: Video-assisted thoracoscopic debridement has been shown to be a safe and efficient procedure for empyema in the adult patient. Its place in the management of childhood empyema remains controversial. METHODS: Over an 18-month period, 9 children were operated upon for pleural empyema. All children were initially treated with appropriate antibiotics and chest-tube drainage. Indication for surgery were persistent clinical symptoms and loculation of pleural fluid 5 to 7 days following initial treatment. In case of a duration of the illness of less than 14 days, an initial attempt was made to debride the pleural space by thoracoscopy. RESULTS: Mean duration of the illness prior to surgery was 15 days (range: 10-23 days), and mean duration of preoperative conservative treatment 10 days (range: 5-20 days). In five of the nine patients thoracoscopy was performed. In all patients thoracoscopy failed to provide adequate clearance of the diseased pleural space because of the advanced stage of the disease. The procedure was converted to a formal thoracotomy in four patients, the fifth patient continued to deteriorate and required formal thoracotomy and decortication seven days later. CONCLUSION: This limited experience suggests that, with the current management and indications, video-assisted thoracoscopic surgery adds little benefit to the treatment of childhood empyema.

Adolescent↗
PubMed1999

Bronchodilator responsiveness in a ventilator-dependent infant with severe tracheobronchomalacia.

A neonatal case of severe, ventilator-dependent tracheobronchomalacia (TBM) is described. The extent of the malacic segment was determined by endoscopy and tracheobronchography. Additionally, relevant and ever increasing reversible peripheral airway obstruction was documented by measuring the mechanical properties of the respiratory system before and after salbutamol. With the combination of endoscopically guided aortopexy and salbutamol infusion, the infant was eventually weaned from mechanical ventilation at the age of 86 days. We speculate that in ventilator-dependent infants with severe TBM the determination of bronchodilator responsiveness may have clinical consequences.

Albuterol↗
PubMed1999

Quality assurance in day surgery: do we do enough for the parents to prevent stress?

In order to identify and analyse the factors associated with stress for the parents during day surgery, we performed a survey analysis of 568 parents whose children underwent surgery consecutively during an 18-month period. Of 368 parents who returned the questionnaire, (follow up rate=65%), 16% experienced the stress associated with day surgery as moderate to severe. The following factors had a significant positive association with the amount of stress: feeling of insufficient preparation (odds ratio; 95% confidence interval) 3. 34 (1.36-8.26; P=0.002), insecurity in nursing care at home 3.36 (1. 43-11.01; P=0.01), problems at home such as fever, vomiting, sleep disorders and others 3.15 (1.72-5.8; P=0.0007), problems with postoperative pain at home 2.43 (1.38-4.3); P=0.008), speaking a foreign language 2.28 (1.08-4.78); P < 0.0001) and no previous surgery 1.31 (0.76-2.27); P=0.03). Analysing these factors showed that often not the problems per se, but rather the insecurity in dealing with them contributed to the experienced stress. Conclusion In order to improve the quality of health care, more pronounced attention has to be given to the parents needs and expectations.

Adolescent↗
PubMed1999

Combined coronary artery bypass grafting and repair of aneurysm of the descending aorta.

The outcome of patients with thoracic or thoracoabdominal aortic aneurysm is often determined by the concomitant coronary artery disease. Two patients with thoracic and thoracoabdominal aortic aneurysm and concomitant single-vessel coronary artery disease underwent combined myocardial revascularization and repair of aortic aneurysm. The operations were performed through a left thoracotomy and thoracoabdominal incision with distal aortic perfusion using a partial femoro-femoral bypass and selective right lung ventilation. Coronary anastomoses were performed on the beating heart, and the aneurysm was replaced with a woven Dacron tube graft.

Aged↗
PubMed1998

Pulmonary function after one-lung ventilation in newborns: the basis for neonatal thoracoscopy.

BACKGROUND: To maintain good exposure during major video-assisted thoracic surgery it is necessary to deflate completely the ipsilateral lung. However, little is known about the effects of one-lung ventilation (OLV) on pulmonary function in newborn patients. METHODS: Ten neonatal domestic pigs with a mean age of 6+/-0.6 days were intubated and ventilated in pressure-controlled mode (inspired oxygen fraction=1.0). One-lung ventilation was maintained for 120 minutes. Serial measurements of hemodynamics and gas exchange were done before, during, and until 90 minutes after OLV. Pulmonary function testing was performed before and after OLV for each lung separately. RESULTS: With the inspired oxygen fraction set at 1.0, arterial oxygen saturation remained stable at 100% during OLV. Venous admixture and alveolar-arterial oxygen tension gradient increased slightly from the baseline value of 2.6% +/-0.3% to 3.8%+/-0.3% during OLV (mean+/-standard error of the mean; p=0.02), and from 358+/-28 to 407+/-18 mm Hg (not significant), respectively. Both values returned to baseline during the subsequent ventilation of both lungs. Static compliance and resistance of the ventilated lung did not change. Compliance of the collapsed lung decreased after reexpansion from 0.42+/-0.07 to 0.29+/-0.06 mL x cm H2O(-1) x kg(-1), p=0.008). Resistance remained unchanged (0.22+/-0.02 versus 0.25+/-0.05 cm H2O x L(-1) x s(-1); not significant). CONCLUSIONS: There were only minor effects on pulmonary function during and after OLV in the neonatal piglet. Alterations in gas exchange during OLV were minimal. Prolonged collapse of the lung with subsequent reexpansion was associated with a slight decrease in compliance, indicating some mild lung injury.

Animals↗
PubMed1997

Postoperative hemodynamics depend on cardiopulmonary bypass temperature: the potential role of endothelin-1.

OBJECTIVE: There is a growing body of evidence that perfusion temperature during cardiopulmonary bypass (CPB) influences postoperative systemic vascular resistance (SVR). The reason for this is not clear. Extracorporeal circulation can provoke raised plasma levels of endothelin-1 (ET-1), a very potent vasoconstrictor peptide produced by endothelial cells. We therefore analysed the effect of CPB temperature on postoperative vascular resistance and plasma concentrations of ET-1. METHODS: Thirty four patients undergoing elective coronary artery bypass grafting procedures were randomly assigned for either normothermic (37 degrees C, n = 17) or hypothermic CPB (28 degrees C, n = 17). Serial measurements of SVR and plasma ET-1 concentrations were performed before, during, and until 9 h after CPB measured. RESULTS: As a consequence of CPB, plasma ET-1 levels increased slightly in both groups. In normothermic patients, ET-1 reached maximal levels at the end of CPB whereas ET-1 levels in patients after hypothermic CPB had a tendency to further increase during the stay in the intensive care unit. Plasma ET-1 levels were significantly higher in patients 9 h postoperatively after hypothermic CPB (1.94 +/- 0.28 vs. 1.30 +/- 0.12 pg/ml, P = 0.033), which was associated with significantly higher systemic vascular resistance index (SVRI) in these patients (area under the curve; 1978 +/- 76 vs. 1626 +/- 69 dyne s/cm5 per m2, P = 0.003). Plasma ET-1 levels showed a positive correlation with postoperative SVRI (P = 0.008, r = 0.51) and a negative correlation with minimal rectal temperature during CPB (P = 0.006, r = 0.55). CONCLUSIONS: These results suggests that the hemodynamic differences after normothermic and hypothermic CPB might be mediated, at least in part, by temperature dependent changes in ET-1 plasma levels.

Adult↗
PubMed1997

Effects of one-lung ventilation on pulmonary hemodynamics and gas exchange in the newborn.

For major thoracoscopic surgery, one-lung ventilation is mandatory. This is reasonably well tolerated in adults and children. The effects of one-lung ventilation on hemodynamics and gas exchange in newborns, however, are not known yet. Eight neonatal domestic pigs with a median age of 6 days (range: 3-9 days), and a mean body weight of 2.3 kg (1.7-2.8 kg) were intubated and ventilated in pressure-controlled mode (FIO2 = 1). Anesthesia was maintained with i.v. fentanyl/metomidate. After tracheotomy an endotracheal tube was positioned in the trachea, and a second tube in the left mainstem bronchus. One-lung ventilation was maintained for 120 min. Serial measurements were done before, during, and until 90 min. after one-lung ventilation. During one-lung ventilation, pulmonary artery pressure and intrapulmonary shunt increased from 15 +/- 1 to 18 +/- 1 mmHg (p = 0.004), and from 2.6 +/- 0.3 to 3.7 +/- 0.4% (p = 0.02), respectively. Arterial oxygen saturation remained unchanged at 100%. A slight increase in arterial PCO2 could easily be treated by increasing the respiratory rate. In conclusion, one-lung ventilation was not associated with major side effects in regard to hemodynamics and gas exchange in the neonatal pig.

Adult↗
PubMed1996

Effect of intermittent warm blood cardioplegia on functional recovery after prolonged cardiac arrest.

BACKGROUND: There is some evidence that continuous warm blood cardioplegia offers good myocardial protection; however, the effects of interrupting cardioplegia remain controversial. To study this, we compared the effects of continuous and intermittent antegrade warm (37 degrees C) blood cardioplegia on functional recovery after prolonged cardiac arrest (180 minutes). METHODS: Twenty-four juvenile pigs were randomly assigned into four groups. Group 1 received continuous cardioplegia, group 2 underwent several periods of 15 minutes of cardioplegia interrupted by 5 minutes of normothermic ischemia, and group 3 underwent several periods of 10 minutes of cardioplegia interrupted by episodes of 10 minutes. The hearts of group 4 received no cardioplegia. Left ventricular systolic function was assessed from fractional left ventricular shortening and percentage left ventricular wall thickening, and left ventricular diastolic function was determined from the time constant of relaxation and the constant of myocardial stiffness. RESULTS: Systolic and diastolic functions were slightly depressed 1 and 2 hours after cross-clamp removal in all four groups, without significant differences among the groups. CONCLUSIONS: These data suggest that antegrade warm blood cardioplegia can be interrupted for up to 10 minutes without obvious negative effects on left ventricular function in the normal myocardium, provided that the intermittent doses of cardioplegia are sufficient to restore the metabolic demands of the arrested myocardium.

Animals↗
PubMed1996

Clinical implications of phrenic nerve injury after pediatric cardiac surgery.

Phrenic nerve injury with resulting diaphragm paralysis occurred in 25 (1.5%) of 1,656 cardiac surgical procedures in children during a 10-year period. Phrenic nerve injury was most commonly noted in patients who had undergone previous cardiac surgery (16 of 165, 10%; P < .0001), typically after a previous Blalock-Taussig shunt (10 of 53, 19%; P = .007). Plication of the diaphragm (7 thoracic, 4 abdominal) was performed in 11 patients (44%). Indications for plication were inability to wean from mechanical ventilation (5 patients) and persistent or recurrent respiratory distress (6 patients). The patients who needed diaphragm plication were significantly younger than those who were managed conservatively (median, 11 months [4 days to 23 months] versus 20 months [4 months to 16 years]; P = .01). All patients older than 2 years were extubated within 3 days (mean, 1.5 days) and did not need any surgical intervention. The median follow-up period was 3.2 years, and no patient has had recurrent respiratory problems. There were no deaths as a direct result of phrenic nerve injury. Phrenic nerve injury after cardiac surgery is a serious complication that often leads to respiratory insufficiency in patients under than 2 years of age. For such patients, early diaphragm plication is a simple and effective procedure that prevents the complications of prolonged mechanical ventilation.

Adolescent↗
PubMed1995

Normothermia versus hypothermia during cardiopulmonary bypass: a randomized, controlled trial.

To evaluate the influence of perfusion temperature on systemic effects of cardiopulmonary bypass (CPB), 30 patients undergoing elective coronary artery bypass grafting were randomly assigned to either normothermic (warm, n = 14, 36 degrees C) or hypothermic (cold, n = 16, 28 degrees C) CPB. Serial hemodynamic measurements and blood samples were obtained before, during and after the CPB procedure. During CPB, there were no differences between both groups in the need for vasopressors (norepinephrine, phenylephrine), urinary output, or fluid balance. In the early postoperative period, normothermic CPB patients had significantly lower systemic vascular resistance and higher cardiac index measurements (mean +/- standard error: systemic vascular resistance, 880 +/- 27 versus 1,060 +/- 57 dyne.s.cm-5, p = 0.025; cardiac index, 3.6 +/- 0.1 versus 2.9 +/- 0.1 L.min-1.m-2, p = 0.01) without differences in the administration of vasoactive drugs. Blood loss was significantly higher in patients after hypothermic CPB (median [range] body surface area: 370 [180-560] versus 490 [280-2,120] mL/m2, p = 0.0006), with a greater need for transfusion of erythrocytes and fresh frozen plasma. Plasma levels of tumor necrosis factor and soluble tumor necrosis factor receptors increased during and after CPB, independent of perfusion temperature. This study suggests a significant influence of CPB temperature and respective perfusion management on postoperative hemodynamics and blood loss. Normothermic CPB is not associated with additional systemic adverse effects.

Blood Loss, Surgical↗
PubMed1995

Influence of hemodynamics on the performances of intravascular gas exchangers.

BACKGROUND: The intravascular gas exchanger is a lung assist device for augmentation of gas exchange in critically ill patients with severe acute respiratory failure. These patients often require inotropic support therapy due to the cardiovascular instability that almost inevitably accompanies severe respiratory failure. METHODS: We investigated the interaction of vasoactive medication (dopamine, nitroglycerin, and noradrenaline) with the gas exchange performances of the intravascular gas exchanger in a bovine experimental model. RESULTS: Dopamine administration highly increased cardiac output, caval flow rates, and diameter of vena cava inferior. These effects resulted in a significant increase in oxygen transfer (baseline, 35 +/- 6 mL/min versus 153 +/- 27 mL/min at 20 micrograms.kg-1.min-1 of dopamine, p < 0.001) and carbon dioxide elimination (baseline, 35 +/- 2 mL/min versus 47 +/- 4 mL/min at 20 micrograms.kg-1.min-1 of dopamine, p < 0.001). Administration of nitroglycerin did not cause significant changes of the hemodynamic parameters nor did it affect the oxygen transfer or carbon dioxide elimination. Noradrenaline caused a moderate increase in cardiac output and caval flow, but no changes of caval diameter. hemodynamic changes were accompanied by an increase in oxygen transfer from 38 +/- 5 mL/min to 68 +/- 7 mL/min (p < 0.01) and carbon dioxide elimination from 33 +/- 1 mL/min to 40 +/- 1 mL/min (p = 0.03). The multiple regression analysis showed significant influence of changes in cardiac output on oxygen transfer (p < 0.001) and carbon dioxide elimination (p = 0.004). The administration of vasoactive drugs induced slight changes in caval diameter that did not significantly affect the gas transfer. CONCLUSIONS: The results from our study reveal the major influence of cardiac output on efficiency of gas transfer of the intravascular oxygenator.

Animals↗
PubMed1995

The influence of leukocyte filtration during cardiopulmonary bypass on postoperative lung function. A clinical study.

The accumulation of activated leukocytes in the pulmonary circulation plays an important role in the pathogenesis of lung dysfunction associated with cardiopulmonary bypass. Animal studies have demonstrated that the elimination of leukocytes from the circulation reduces postoperative lung injury and improves postoperative pulmonary function. We conducted a prospective randomized clinical study to evaluate whether postoperative lung function could be improved by use of a leukocyte filter during cardiopulmonary bypass. Elective coronary artery bypass grafting was done with a leukocyte-depleting arterial blood filter incorporated in the extracorporeal circuit (14 patients, leukocyte filter group) or without the filter (18 patients, control group). Blood samples collected at intervals before, during, and after operation were used for analysis of blood cell counts, elastase concentrations, and arterial blood gases. The use of the leukocyte filter caused no significant reduction in leukocyte count (p = 0.86). There were no differences in postoperative lung function between the groups, as assessed through (1) oxygenation index (290 for leukocyte filter group compared with 329 for control group, 95% confidence interval, 286 to 372, p = 0.21), (2) pulmonary vascular resistance (p = 0.10), and (3) intubation time (16.6 hours for leukocyte filter group versus 15.7 hours for control group, 95% confidence interval, 12.1 to 19.1 hours, p = 0.72). The levels of neutrophil elastase were significantly higher at the end of cardiopulmonary bypass in the leukocyte filter group (460 microgram/L in leukocyte filter group versus 230 microgram/L in control group, 95% confidence interval, 101 to 359 microgram/L, p = 0.003). We conclude that the clinical use of the present form of leukocyte-depleting filter did not improve any of the postoperative lung function parameters analyzed in this study.

Cardiopulmonary Bypass↗
PubMed1995

Continuous versus bolus thermodilution cardiac output measurements--a comparative study.

OBJECTIVE: To compare the methods for continuous and bolus thermodilution cardiac output measurements. DESIGN: In vivo and in vitro experimental studies. SETTING: Surgical research division in a university hospital. SUBJECTS: Eight calves and flow bench model. INTERVENTIONS: Data were collected in vivo from eight calves instrumented with pulmonary artery catheters, which allowed both continuous and bolus thermodilution measurements. The pulmonary artery catheter was placed through the external jugular vein. All in vitro measurements were performed using a flow bench model. MEASUREMENTS AND MAIN RESULTS: A total of 232 bolus and continuous thermodilution measurements were analysed in vivo to determine the degree of agreement between the two methods. The absolute measurement bias was 0.14 L/min with 95% confidence limits ranging from -0.83 to 1.15 L/min. In vitro analysis of 576 measurements at six different temperature points (range 31 degrees to 41 degrees C), using clinically relevant flows (2 to 9 L/min), showed overestimation of flow values using continuous and bolus thermodilution methods. However, the continuous method showed better accuracy by a lower degree of overestimation. Systematic error was 9.7 +/- 8.4 (SD) % for continuous and 11.1 +/- 6.3% for the bolus method (p < .001). This effect was especially evident at lower flow rates. The influence of various temperatures on the accuracy and reproducibility of both methods of measurement was statistically significant but not clinically relevant. The infusion of lactated Ringer's lactate solution (infusion rates 100 to 1000 mL/hr) affects both methods at a low flow rate of 2 L/min, without causing a significant effect on continuous measurement at a higher flow rate (4 L/min). Shunting of 50% of circulating volume to the distal part of the thermal filament of the pulmonary catheter impaired the accuracy of continuous measurement without affecting results from bolus measurements (systematic error -26.8 +/- 8.2% for continuous and -5.2 +/- 4.1% for bolus thermodilution). CONCLUSIONS: Continuous thermodilution cardiac output measurement provided higher accuracy and greater resistance to thermal noise than standard bolus measurements. The correct placement of the catheter is essential for precise measurements.

Analysis of Variance↗
PubMed1995

Acute lung injury during cardiopulmonary bypass. Are the neutrophils responsible?

To test the hypothesis that acute lung injury during cardiopulmonary bypass (CPB) is related to the activation of neutrophils and the body temperature during bypass, we determined the differential WBC count, plasma elastase concentrations, and lung function before, during, and after CPB in 38 patients undergoing elective coronary artery bypass surgery. The patients were randomly assigned to receive either normothermic (n = 19, rectal temperature: 35.9 +/- 0.1 degrees C, mean +/- SE) or hypothermic (n = 19, 29.2 +/- 0.5 degrees C) CPB. The cellular response to the extracorporeal circulation was significantly delayed in the hypothermic group with a later onset of neutrophilia and a later increase in plasma elastase levels during bypass. Lung function deteriorated significantly after CPB as assessed by respiratory index, alveolar-arterial oxygen gradient, and intrapulmonary shunt, independent of bypass temperature. There was a positive correlation between peak elastase concentrations and postoperative respiratory index as well as intrapulmonary shunt (R2 = 0.5, p = 0.002 and R2 = 0.45, p = 0.003, respectively). Besides peak plasma elastase levels, multiple regression revealed no significant influence of other independent factors on postoperative lung dysfunction in our patients.

Body Temperature↗
PubMed1994

Quantitative gas transfer of an intravascular oxygenator.

The intravascular oxygenator is a newly developed device for intracaval gas exchange in critically ill patients with respiratory failure. In an experimental ex vivo model, performance characteristics of the intravascular oxygenator/carbon dioxide removal device were studied. With a mean hemoglobin concentration of 6.2 +/- 1.9 g/dL (mean +/- standard deviation), total O2 transfer was 21.8 +/- 4.8 mL/min at a blood flow of 1 L/min, 37.0 +/- 12.6 mL/min at 2 L/min, at 2 L/min, and 47.5 +/- 16.7 mL/min at 3 L/min. Total CO2 transfer was 27.3 +/- 6.6 mL/min at a blood flow of 1 L/min, 38.6 +/- 8.9 mL/min at 2 L/min, and 40.4 +/- 9.3 mL/min at 3 L/min. In contrast to total gas transfer, O2/CO2 transfer rates (mL/L) diminished significantly with increasing blood flow. In addition, there was a negative correlation between O2 transfer rate and venous O2 partial pressure (r = -0.73; p < 0.0001), a positive correlation between CO2 transfer rate and venous CO2 partial pressure (r = 0.65; p < 0.0001), and a positive correlation between O2 and CO2 transfer rates and blood hemoglobin level (r = 0.57 [p < 0.01] and r = 0.70 [p < 0.01], respectively). These results demonstrate that the behavior of the intravascular hollow-fiber oxygenator is similar to that of the classic membrane oxygenator used for cardiopulmonary bypass: total gas transfer correlates directly with blood flow and venous CO2 partial pressure and indirectly with venous O2 partial pressure. The O2 and CO2 transfer rates increase significantly with increasing hemoglobin content of the blood.

Animals↗