Wolfram Schütz

Electrocardiographic exercise stress testing for cardiac risk assessment in patients undergoing noncardiac surgery.

BackgroundThe value of exercise electrocardiography in the prediction of perioperative cardiac risk has yet to be defined. This study was performed to determine the predictive value of exercise electrocardiography as compared with clinical parameters and resting electrocardiography. MethodsA total of 204 patients at intermediate risk for cardiac complications prospectively underwent exercise electrocardiography before noncardiac surgery. Of these, 185 were included in the final evaluation. All patients underwent follow-up evaluation postoperatively by Holter monitoring for 2 days, daily 12-lead electrocardiogram, and creatine kinase, creatine kinase MB, and troponin-T measurements for 5 days. Cardiac events were defined as cardiac death, myocardial infarction, minor myocardial cell injury, unstable angina pectoris, congestive heart failure, and ventricular tachyarrhythmia. Potential risk factors for an adverse event were identified by univariate and multivariate logistic regression analysis. ResultsPerioperative cardiac events were observed in 16 patients. There were 6 cases of myocardial infarction and 10 cases of myocardial cell injury. The multivariate correlates of adverse cardiac events were definite coronary artery disease (odds ratio, 8.8; 95% confidence interval [CI], 1.1–73.1;P = 0.04), major surgery (odds ratio, 4.7; 95% CI, 1.3–16.3;P = 0.02), reduced left ventricular performance (odds ratio, 2.0; 95% CI, 1.1–3.8;P = 0.03), and ST-segment depression of 0.1 mV or more in the exercise electrocardiogram (odds ratio, 5.2; 95% CI, 1.5–18.5;P = 0.01). A combination of clinical variables and exercise electrocardiography improved preoperative risk stratification. ConclusionsThis prospective study shows that a ST-segment depression of 0.1 mV or more in the exercise electrocardio-gram is an independent predictor of perioperative cardiac complications.

Transesophageal Echocardiographic Guidance of Thoracic Aortic Stent-Graft Implantation

Purpose: To evaluate the efficacy of intraoperative transesophageal echocardiography (TEE) as an adjunctive measure in guiding the implantation of endoluminal stent-grafts in the thoracic aorta. Methods: TEE was used in 21 of 30 patients (27 men; median age 70 years; range 19–77) undergoing implantation of Excluder or Talent stent-grafts for management of 11 type B aortic dissections, 7 thoracic aortic aneurysms, 2 traumatic thoracic aortic ruptures, and an aortic coarctation. We evaluated the ability of TEE to provide evidence of (1) correct placement of the guidewire within the true lumen, (2) reduction in blood flow in the false lumen following stent deployment, and (3) early complications. Results: Definite identification of the true lumen and a reliable evaluation of the position of the stent-graft guidewire during advancement were possible in all patients. Reduction of blood flow within the false lumen following deployment of the stent-graft was visualized in >70% of patients with aortic dissection. In the patient with aortic coarctation, TEE recognized the acute onset of aortic dissection following stent dilation, which resulted in immediate management with an additional stent. Conclusions: The intraoperative use of TEE in the implantation of stent-grafts in the thoracic aorta is not significantly invasive and is easily employed. It permits excellent evaluation of the correct placement of the stent guidewire and, in patients with aortic dissection, intraoperatively visualizes effective blood flow reduction in the false lumen following stent-graft deployment. Its ability to recognize early complications may indicate the need for additional maneuvers during the surgical procedure.

perioperative Risk of Bradyarrhythmias in Patients with Asymptomatic Chronic Bifascicular Block or Left Bundle Branch Block : does an Additional First-degree Atrioventricular Block Make Any Difference?

Background The incidence of perioperative bradyarrhythmias in patients with bifascicular or left bundle branch block (LBBB) and the influence of an additional first‐degree atrioventricular (A‐V) block has not been evaluated with 24‐h Holter electrocardiographic monitoring. Therefore the authors assessed the rate of block progression and bradyarrhythmia in these patients. Methods Patients (n = 106) with asymptomatic bifascicular block or LBBB with or without an additional first‐degree A‐V block scheduled for surgery under general or regional anesthesia were enrolled prospectively. Three patients were excluded. Of the 103 remaining, 56 had a normal P‐R interval and 47 had a prolonged one. Holter monitoring (CM2, CM5) was applied to each patient just before induction of anesthesia and was performed for 24 h. The primary endpoint of the study was the occurrence of block progression. As secondary endpoints, bradycardias < 40 beats/min with hemodynamic compromise (systolic blood pressure < 90 mmHg) or asystoles > 5 s were defined. Results Block progression to second‐degree A‐V block and consecutive cardiac arrest occurred in one case of LBBB without a prolonged P‐R interval. Severe bradyarrhythmias with hypotension developed in another eight patients: asystoles > 5 s occurred in two cases and six patients had bradycardias < 40/min. Pharmacotherapy was successful in these eight patients. There was no significant difference for severe bradyarrhythmias associated with hemodynamic compromise between patients with and without P‐R prolongation (P = 1.00). Conclusions In patients with chronic bifascicular block or LBBB, perioperative progression to complete heart block is rare. However, the rate of bradyarrhythmias with hemodynamic compromise proved to be relevant. Because an additional first‐degree A‐V block did not increase the incidence of severe bradyarrhythmias and pharmacotherapy by itself was successful in nearly all cases, routine prophylactic insertion of a temporary pacemaker in such patients should be questioned.

The Erlanger Microlightguioe Photometer: A new concept for monitoring intracapillary oxygen supply of tissue — First results and a review of the physiological basis

The local oxygen supply to the skin immediately before and after withdrawal of blood was appraised in 18 healthy test subjects by measuring the intracapillary hemoglobin oxygenation (HbO2). The investigation was carried out with the Erlanger Microlightguide Photometer (EMPHO). EMPHO measurements are based on the registration of tissue remission spectra from which the HbO2 values are calculated using the Kubelka-Munk theory. The results show that global parameters do not reflect the supply of oxygen to the tissue; for example, in hypovolemia, the physiological response to the pathophysiological stimulus is centralization. This is manifested at a very early stage in the skin, before the oxygen supply to other organs (e.g., liver, kidney, gut) is affected. The disturbance of the local cutaneous oxygen supply is reflected in a change in the intracapillary hemoglobin oxygenation of the skin. Hence, one might consider measurements of the local oxygen supply to the skin as an early indicator for centralization.

Perioperative transcutaneous pacemaker in patients with chronic bifascicular block or left bundle branch block and additional first-degree atrioventricular block

Background: Complete heart block is dreaded perioperatively in patients with chronic bifascicular or left bundle branch block (LBBB) and additional first‐degree A‐V block. Our aim was to investigate the necessity as well as the efficacy and safety of transcutaneous pacing in the perioperative setting.

Left ventricular diastolic dysfunction. Implications for anesthesia and critical care

Over the last two decades there has been a growing recognition that cardiac function is not solely determined by systolic but also essentially by diastolic function. Left ventricular diastolic dysfunction is characterized by an impairment of ventricular filling caused either by abnormal relaxation, an active energy consuming process or decreased compliance, which is determined by passive tissue properties of the ventricle. Doppler echocardiography, including tissue Doppler imaging, has emerged as the preferred clinical tool for the assessment of left ventricular diastolic function. Recently the importance of left ventricular diastolic function is increasingly being recognized also during the perioperative period. Newer studies have shown that after cardiopulmonary bypass there is a significant decrease in left ventricular compliance. Experimental studies have demonstrated that sepsis is associated with a decrease in both active relaxation and ventricular compliance. Initial studies are also focusing on therapeutic options for patients with isolated diastolic dysfunction.ZusammenfassungIn den letzten beiden Dekaden wurde zunehmend erkannt, dass die Ventrikelfunktion nicht nur durch die systolische, sondern entscheidend auch durch die diastolische Funktion bestimmt wird. Eine normale diastolische Funktion ist durch die Fähigkeit gekennzeichnet, bei normalen Füllungsdrücken ausreichende Blutvolumina in die Ventrikel aufzunehmen. Bestimmt wird die diastolische Funktion durch einen aktiven, energieverbrauchenden Prozess, die Relaxation, und durch die passiven Eigenschaften des Ventrikels, die ventrikuläre Compliance. Diagnostisch nimmt die Dopplerechokadiographie durch Analyse des transmitralen sowie des pulmonalvenösen Flussprofils und durch Quantifizierung der Exkursionen des Mitralklappenanulus eine zentrale Stellung ein. In letzter Zeit wird die Bedeutung der diastolischen Ventrikelfunktion auch im perioperativen Bereich zunehmend erkannt. Neuere Studien haben gezeigt, dass es nach kardiopulmonalem Bypass zu einer Abnahme der ventrikulären Compliance kommt. Im Zusammenhang mit einer Sepsis scheinen nicht nur Störungen der aktiven Relaxation, sondern auch Veränderungen der passiven Eigenschaften des linken Ventrikels aufzutreten. Erste Arbeiten beschäftigen sich auch mit Therapieansätzen bei Patienten mit isolierter diastolischer Dysfunktion.AbstractOver the last two decades there has been a growing recognition that cardiac function is not solely determined by systolic but also essentially by diastolic function. Left ventricular diastolic dysfunction is characterized by an impairment of ventricular filling caused either by abnormal relaxation, an active energy consuming process or decreased compliance, which is determined by passive tissue properties of the ventricle. Doppler echocardiography, including tissue Doppler imaging, has emerged as the preferred clinical tool for the assessment of left ventricular diastolic function. Recently the importance of left ventricular diastolic function is increasingly being recognized also during the perioperative period. Newer studies have shown that after cardiopulmonary bypass there is a significant decrease in left ventricular compliance. Experimental studies have demonstrated that sepsis is associated with a decrease in both active relaxation and ventricular compliance. Initial studies are also focusing on therapeutic options for patients with isolated diastolic dysfunction.

Linksventrikuläre diastolische Dysfunktion

Over the last two decades there has been a growing recognition that cardiac function is not solely determined by systolic but also essentially by diastolic function. Left ventricular diastolic dysfunction is characterized by an impairment of ventricular filling caused either by abnormal relaxation, an active energy consuming process or decreased compliance, which is determined by passive tissue properties of the ventricle. Doppler echocardiography, including tissue Doppler imaging, has emerged as the preferred clinical tool for the assessment of left ventricular diastolic function. Recently the importance of left ventricular diastolic function is increasingly being recognized also during the perioperative period. Newer studies have shown that after cardiopulmonary bypass there is a significant decrease in left ventricular compliance. Experimental studies have demonstrated that sepsis is associated with a decrease in both active relaxation and ventricular compliance. Initial studies are also focusing on therapeutic options for patients with isolated diastolic dysfunction.ZusammenfassungIn den letzten beiden Dekaden wurde zunehmend erkannt, dass die Ventrikelfunktion nicht nur durch die systolische, sondern entscheidend auch durch die diastolische Funktion bestimmt wird. Eine normale diastolische Funktion ist durch die Fähigkeit gekennzeichnet, bei normalen Füllungsdrücken ausreichende Blutvolumina in die Ventrikel aufzunehmen. Bestimmt wird die diastolische Funktion durch einen aktiven, energieverbrauchenden Prozess, die Relaxation, und durch die passiven Eigenschaften des Ventrikels, die ventrikuläre Compliance. Diagnostisch nimmt die Dopplerechokadiographie durch Analyse des transmitralen sowie des pulmonalvenösen Flussprofils und durch Quantifizierung der Exkursionen des Mitralklappenanulus eine zentrale Stellung ein. In letzter Zeit wird die Bedeutung der diastolischen Ventrikelfunktion auch im perioperativen Bereich zunehmend erkannt. Neuere Studien haben gezeigt, dass es nach kardiopulmonalem Bypass zu einer Abnahme der ventrikulären Compliance kommt. Im Zusammenhang mit einer Sepsis scheinen nicht nur Störungen der aktiven Relaxation, sondern auch Veränderungen der passiven Eigenschaften des linken Ventrikels aufzutreten. Erste Arbeiten beschäftigen sich auch mit Therapieansätzen bei Patienten mit isolierter diastolischer Dysfunktion.AbstractOver the last two decades there has been a growing recognition that cardiac function is not solely determined by systolic but also essentially by diastolic function. Left ventricular diastolic dysfunction is characterized by an impairment of ventricular filling caused either by abnormal relaxation, an active energy consuming process or decreased compliance, which is determined by passive tissue properties of the ventricle. Doppler echocardiography, including tissue Doppler imaging, has emerged as the preferred clinical tool for the assessment of left ventricular diastolic function. Recently the importance of left ventricular diastolic function is increasingly being recognized also during the perioperative period. Newer studies have shown that after cardiopulmonary bypass there is a significant decrease in left ventricular compliance. Experimental studies have demonstrated that sepsis is associated with a decrease in both active relaxation and ventricular compliance. Initial studies are also focusing on therapeutic options for patients with isolated diastolic dysfunction.

Noninvasive Diagnosis of Coronary Artery Disease: A Comparison between Cardiokymographic and Electrocardiographic Stress Testing

Noninvasive cardiokymography has been further developed to be able to record wall motion abnormalities during exercise. The study was designed to evaluate the diagnostic accuracy of stress cardiokymography and electrocardiography in the diagnosis of coronary artery disease. 223 patients were included in a prospective investigation using a newly developed computerized cardiokymography device. Sensitivity, specificity, and positive predictive value were 61, 69 and 90% for exercise cardiokymography, and 57, 74 and 91% for exercise electrocardiography, respectively. There was no statistically significant difference between cardiokymography and electrocardiography. The combination of electrocardiography and cardiokymography did not produce a significant improvement in diagnostic accuracy in comparison to exercise electrocardiography alone.

Influence of intravenous calcium gluconate on saphenous vein graft flow in closed-chest patients

The effects of calcium gluconate on hemodynamics and saphenous vein graft flow in a group of patients undergoing elective coronary artery bypass grafting who developed ionized hypocalcemia at the end of the surgical procedure were examined. The patients received a central venous bolus of 15 mg/kg of calcium gluconate. Heart rate (HR), arterial pressure (AP), central venous pressure (CVP), pulmonary artery pressure (PAP), pulmonary capillary wedge pressure (PCWP), and cardiac output were measured immediately before and 30, 60, 120, 180, and 240 seconds after injection of calcium gluconate. Systemic and pulmonary vascular resistance (SVR and PVR, respectively), cardiac index (CI), stroke volume index (SVI), and right and left ventricular stroke work index (RVSWI and LVSWI, respectively), were calculated. Venous bypass flow velocity (Vbypass-flow) was assessed using a Doppler probe that was attached to the left anterior descending artery (LAD) bypass intraoperatively. Calcium gluconate significantly increased MAP, SVR, and LVSWI from 67 +/- 3 mmHg (mean +/- SEM), 1,128 +/- 128 dyne.s.cm-5 and 25 +/- 3 g.m.beat/m to a maximum of 81 +/- 5 mmHg (P < 0.01), 1,401 +/- 196 dyne.s.cm-5 (P < 0.05), and 32 +/- 4 g.m/beat/m (P < 0.01), respectively. HR, CVP, PAP, PCWP, PVR, CI, SVI, and Vbypass-flow remained unaltered. It is concluded that calcium gluconate administered to moderately hypocalcemic patients increases arterial pressure mainly by peripheral vasoconstriction. Because the increase of arterial pressure, and, thereby, coronary perfusion pressure is not associated with an increase of LAD bypass flow, vasoconstriction in the coronary vascular bed distal to the venous graft cannot be ruled out, and deterioration of the myocardial oxygen supply/demand ratio is strongly suggested.

Influence of acute changes in lung compliance on ventilation in newborns, examined with two different respirators

Zusammenfassung. An sechzehn neugeborenen Ferkeln wurde randomisiert untersucht, wie die Geräte Cicero (Dräger/Lübeck) und Servo 900 C (Siemens Elema/Schweden) auf eine durch einen definierten Spannungspneumothorax hervorgerufene Einschränkung der Lungencompliance reagieren und welchen Einfluß dies auf die Ventilation der Tiere hat. Beim Servo (n=8, Gewicht 1233±172 g) war die Anlage des Spannungspneumothorax am signifikanten Anstieg des Beatmungsspitzendrucks (PIP) zu erkennen, führte jedoch zur Hyperkapnie aller Tiere (PaCO2)=61,2±5,9 mm Hg). Exspiratorisches Tidal- (Vtex) und Atemminutenvolumen (AMVex) blieben unverändert. Durch eine Erhöhung der Atemfrequenz ließ sich das AMVex adäquat steigern und die Ventilation verbessern. Beim Cicero (n=8, Gewicht 1225±239 g) stiegen unter dem Pneumothorax AMVex, Vtex und PIP sowohl absolut als auch gegenüber dem Servo signifikant an, was zu einem signifikant niedrigerem PaCO2 (43,3±6,2 mm Hg) führte. Eine Erhöhung der Atemfrequenz war nur bei drei Tieren nötig. Bei der Beatmung Früh- und Neugeborener kann eine akute Störung der Lungencompliance bei beiden Geräten zur Hypoventilation führen, die mit dem Cicero jedoch deutlich geringer ausfällt. Dies wird auf eine geräteinterne Compliancekorrektur zurückgeführt, die das vom Gerät in das Beatmungssystem abgegebene Hubvolumen bei Abnahme der Patientencompliance automatisch erhöht und damit die alveoläre Ventilation weitgehend aufrechterhält.Abstract. In most ventilators used in anaesthesia tidal volume delivered during mechanical ventilation is different from the tidal volume preset at the respirator on the basis of respirator and circuit compliance and gas compression during inspiration. The error in ventilation due to the compressed volume is especially significant clinically when the tidal volume is very small or when the airway pressure is very high. In newborns and neonates in particular, decreasing lung compliance during a surgical procedure may contribute to marked hypoventilation. We therefore investigated ventilation in newborn piglets during decreasing lung compliance induced by tension pneumothorax. We used the anaesthesia ventilator CICERO (Dräger, Lübeck, Germany) and the SERVO 900 C ventilator (Siemens-Elema, Sweden). Materials and methods. Two anaesthesia ventilators, the CICERO (group I, n=8) and the SERVO ventilators (group II, n=8) were investigated following randomized selection in a group of 16 newborn piglets (Table 1). After normoventilation for 60 min a tension pneumothorax at +10 mbar was induced. After 15 min the pneumothorax was increased to +20 mbar and maintained at this level for the rest of the study. When hypercapnia (PaCO2>45 mm Hg) resulted, the respiratory rate was increased by +10/min after 15 min with pneumothorax at +20 mbar. When hypercapnia continued, the respiratory rate was increased again 25 min and if necessary also 35 min after the induction of pneumothorax at 20 mbar. After normoventilation for 60 min (T1) (Table 2), after 15 min with pneumothorax at +10 mbar (T2) and after 15 min (T3), 25 min (T4), 35 min (T5) and 45 min (T6) with pneumothorax at +20 mbar the following parameters were obtained: central venous (CVP) and mean arterial pressure (MAP), heart rate (HR), arterial (PaCO2 and end-tidal CO2 tension (PetCO2), peak inspiratory pressure (PIP), respiratory frequency (RF) and expiratory tidal (Vtex) and minute volume (VE). Results. In group I the pneumothorax resulted in a significantly smaller increase in PaCO2 (43.3±6.2 mm Hg) than in group II (Fig. 1), and hypercapnia was present in only 3 piglets. Vtex (Fig. 2), VE (Fig. 3) and PIP (Fig. 5) increased significantly, with significantly higher values than in group II, while PetCO2 (Fig. 6) decreased significantly. In group II the pneumothorax was attributed to a significant increase in PaCO2 and a marked hypercapnia in all piglets (PaCO2 61.2±5.9 mm Hg) (Fig. 1). Vtex (Fig. 2) and VE (Fig. 3) remained unchanged, while PIP (Fig. 5) and PetCO2 (Fig. 6) increased. Following the increase in RF (Fig. 4) in all piglets, Vtex and VE increased and PaCO2 and PetCO2 decreased. Conclusions. During ventilation of neonates with the SERVO ventilator a decrease in lung compliance will cause hypoventilation and hypercapnia. This is reflected by an increase in peak inspiratory pressure and can be corrected by increasing the respiratory rate. In contrast, the CICERO is able to preserve ventilation by an internal correction for gas compression, but it does not guarantee normoventilation in all cases. In neither group does the end-tidal PCO2 reflect the true ventilation during decreasing lung compliance, so that arterial blood gas analysis seems to be mandatory for the diagnosis of hypercapnia in such situations.