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Biomedical subjects

N Rolf

Publications and source records attributed to N Rolf.

At least 37 records · Page 2Linked to original sources
PubMed1998

[Cardiovascular effects of sevoflurane].

The cardiovascular effects of sevoflurane are similar to those of isoflurane with some minor exceptions. In contrast to isoflurane and particularly to desflurane, sevoflurane has not been associated with increases in heart rate in healthy volunteers and in patients. The coronary vasodilatory potency of sevoflurane appears to be lower than that of isoflurane and it has not been associated with a reduction of blood flow to collateral myocardium in dogs with steal-prone anatomy. In several multi-center studies of patients with coronary artery disease or at high risk for coronary artery disease receiving either sevoflurane or isoflurane for either cardiac or non-cardiac surgery, the incidence of myocardial ischemia and infarction did not differ between treatment groups. In both human and animal models, sevoflurane preserves cerebral blood flow and reduces cerebral metabolic rate, much like isoflurane.

Anesthetics, Inhalation↗
PubMed1998

Thoracic epidural anesthesia does not affect functional recovery from myocardial stunning in sevoflurane-anesthetized dogs.

OBJECTIVE: A beneficial effect of thoracic epidural anesthesia (TEA) on recovery from myocardial stunning was previously shown in awake dogs. The aim of this study was to investigate the effects of TEA on recovery from myocardial stunning in sevoflurane-anesthetized dogs. DESIGN: Randomized animal study. SETTING: Animal laboratory of a university hospital. PARTICIPANTS: Chronically instrumented mongrel dogs. INTERVENTIONS: Six dogs were chronically instrumented for measurement of hemodynamics and myocardial wall thickening fraction (WTF). The following experiments were performed on separate days in a crossover fashion: (1) 10 minutes of ischemia of the left anterior descending (LAD) coronary artery during sevoflurane anesthesia without TEA and (2) 10 minutes of ischemia during sevoflurane anesthesia with TEA. MEASUREMENTS AND MAIN RESULTS: WTF was measured awake (baseline) and at predetermined time points until complete recovery of myocardial function occurred. Induction of anesthesia led to a decrease of WTF compared with baseline. Induction of ischemia led to a further decrease of WTF to negative values, which returned to positive values within the first minute of reperfusion. There were no differences between the two experimental conditions at any of the time points measured. In awake dogs, TEA improved the recovery from myocardial stunning compared with the control experiment. There was no difference between conscious dogs with TEA or sevoflurane-anesthetized dogs with or without TEA. CONCLUSION: TEA has no additional protective effect on the recovery of WTF during sevoflurane anesthesia.

Anesthesia, Epidural↗
PubMed1998

Central neuroaxis blockade and coronary circulation.

The coronary circulation is subject to modulation by the autonomic nervous system. Thus, sympathetic stimulation causes coronary vasodilation in healthy humans, whereas stenotic coronary arteries react by vasoconstriction in response to sympathetic stimulation. It is for this reason that experimental studies and clinical evidence revealed beneficial effects of a blockade of cardiac sympathetic drive by thoracic epidural anaesthesia on coronary perfusion and myocardial function in normal and in ischaemic myocardium. In contrast, segmental lumbar epidural anaesthesia leads to a compensatory increase in cardiac sympathetic outflow which may jeopardize myocardial areas dependent on perfusion by stenotic coronary arteries.

Journal Article↗
PubMed1998

Comparative hemodynamic effects of three different parenterally administered lipid emulsions in conscious dogs.

OBJECTIVE: To compare the hemodynamic side effects of three structurally different lipid emulsions. DESIGN: Randomized, controlled, prospective animal study. SETTING: University research laboratory. SUBJECTS: Six chronically instrumented mongrel dogs. INTERVENTIONS: On separate days, all animals were submitted to three different treatments, in a randomized order. After baseline measurements, either a long-chain triglyceride emulsion (treatment 1), a mixed medium-chain triglyceride/long-chain triglyceride emulsion (treatment 2), or an omega3 polyunsaturated fatty acid long-chain triglyceride (PUFA) emulsion (treatment 3) was administered intravenously over 30 mins. MEASUREMENTS AND MAIN RESULTS: Global and regional hemodynamics (sonomicrometry) were recorded for 2 hrs after baseline measurements. Arterial blood gases and plasma concentrations of hemoglobin, triglycerides, total protein, and glucose were recorded for 2 hrs. Long-chain triglycerides did not affect the cardiovascular performance in awake animals. However, medium-chain triglycerides/long-chain triglycerides and omega3 PUFA caused marked increases in systemic vascular resistance (from 1833 +/- 154 to 3277 +/- 163 mm Hg/dynexsec5, p < .05), heart rate (from 89 +/- 6 to 158 +/- 10 beats/min, p < .05), and depressed ventricular performance (wall-thickening fraction [as percentage from baseline] decreased to 53 +/- 9%, p < .05). CONCLUSIONS: Commercially available lipid emulsions can cause profound cardiovascular side effects at high doses, depending on their composition. Whereas long-chain triglyceride emulsions have virtually no effects on hemodynamics in normal dogs, medium-chain triglyceride/long-chain triglyceride, and omega3 PUFA emulsions should be used with caution in critically ill patients with compromised cardiovascular function.

Acidosis↗
PubMed1998

Clonidine improves recovery from myocardial stunning in conscious chronically instrumented dogs.

UNLABELLED: Clonidine, an alpha2-adrenergic agonist, has been widely used in anesthesia because of its sedative, analgesic, sympatholytic, and specific hemodynamic effects. The use of clonidine in myocardial ischemia is controversial because of its bradycardic and hypotensive effects. In the present study, we tested the hypothesis that clonidine improves recovery from myocardial stunning in conscious dogs. Seven dogs were chronically instrumented to allow measurement of left atrial pressure (LAP), aortic blood pressure (ABP), left ventricular pressure (LVP), maximal rate of increase of LVP (LVdP/dtmax), and myocardial wall thickening fraction (WTF). The myocardial blood flow was measured using colored microspheres. To compensate for any potential interaction between the two ischemic episodes, experiments were performed on separate days in a cross-over fashion (four animals underwent Condition 1, and three underwent Condition 2 as their first experiment). The ischemic episodes involved 1) 10 min of ischemia of the left anterior descending (LAD) coronary artery without any intervention, and 2) 10 min of LAD ischemia 30 min after 10 microg/kg iv clonidine. WTF was measured before the induction of ischemia or the application of clonidine (baseline) and at predetermined time points until complete recovery of myocardial function. WTF recovered faster during the first 2 h of reperfusion when clonidine was administered. The increase in plasma epinephrine was attenuated by clonidine during ischemia, but there was no change during reperfusion. The increase of plasma norepinephrine levels was attenuated during ischemia and reperfusion. The hemodynamic effects of clonidine did not depress myocardial perfusion or impair myocardial function. IMPLICATIONS: In this study, we investigated the effects of IV clonidine on myocardial stunning in chronically instrumented dogs. Clonidine improved the recovery from myocardial stunning and attenuated increases in catecholamine plasma levels.

Adrenergic alpha-Agonists↗
PubMed1997

[Preoperative evaluation and preparation. The view of the anesthetist].

Besides other reasons, cost containments mandate the rational use of preoperative screening tests which should be adapted to the risk of the individual patient. Since the perioperative cardiac risk increases with age, elderly patients in particular require a thorough evaluation of their perioperative risk. Routine ECG, however, is not indicated in patients under 45 years of age who do not present with signs or history of preexisting cardiac diseases but should be performed on a routine basis in all patients over 45 years of age. The validity of an ergometer test as a preoperative indicator of myocardial ischemia is limited due to high incidence of false negative results. By preoperative routine chest radiography previously unknown findings are only detected in a small number of patients; thus, in patients of ASA-risk groups I-II younger than 74 years of age routine chest-x-ray cannot be justified. In patients whose perioperative cardiac risk as assessed clinically and by ECG is ambiguous, dipyridamole-thallium-myocardial scintigraphy (DTMS) and dobutamine-stress-echocardiography may contribute valuable information regarding the prediction of perioperative adverse cardiac events. In that respect, dobutamine-stress-echocardiography appears to be superior to DTMS. The laboratory tests required in patients of different ASA-risk groups and according to their age are presented in an overview.

Anesthesia↗
PubMed1997

[Interaction of nimodipine and propofol in dogs. Hemodynamics and cardiodynamics].

UNLABELLED: Nimodipine is frequently used for treatment of cerebral vasospasm in patients undergoing intracerebral vascular surgery and during intensive care therapy of patients with subarachnoid haemorrhage. Propofol is being increasingly used as a hypnotic drug in neuroanaesthesia and for sedation in critically ill patients. There is evidence of a propofol effect on voltage-dependent calcium channels; hence, the administration of propofol may interact with the haemodynamic effects of nimodipine. We investigated the haemodynamic interactions of both compounds in chronically instrumented dogs. METHODS: Five mongrel dogs were chronically instrumented for measurement of heart rate (HR), left atrial (LAP), aortic (ABP), and left ventricular pressure (LVP), LV dP/dt, cardiac output (CO), systemic vascular resistance (SVR), coronary blood flow velocity (CBFV), and myocardial wall-thickening fraction (WTF). After complete recovery from surgery and assessment of normal resting blood gas values and temperature, all animals received on separate days either propofol 30 mg/kg.h (P), nimodipine in two maintenance doses in the awake state (N), or the combination of nimodipine and propofol (N+P). The maintenance doses of nimodipine in N and N+P were 1 and 2 micrograms/kg.min for 40 min each after a bolus of either 10 or 20 micrograms/kg min over 2 min. Measurements were performed as controls, in the middle (20 min), and at the end (40 min) of each maintenance infusion of nimodipine or at equivalent points in time in group P (Fig. 1). Animals receiving propofol were mechanically ventilated after endotracheal intubation. Blood gas values were kept within the normal range. All data were analysed with repeated measures of ANOVA followed by student's t-test with Bonferroni correction. RESULTS: There was no statistically significant difference for any of the measured parameters between N and N+P or between the two maintenance doses of nimodipine (Table 1). HR was significantly higher with both doses of nimodipine in the awake state compared to the control values (123 +/- 7.1 and 146 +/- 6.4 vs 78 +/- 2.4/min). The administration of nimodipine with and without propofol led to a significant increase in CBFV (Fig. 2). However, there was no difference in CBFV between nimodipine in the awake state and in combination with propofol (Fig. 2). CONCLUSIONS: We conclude that administration of propofol does not alter the systemic haemodynamic and regional myocardial effects of a nimodipine infusion in a dose of 1 or 2 micrograms/kg.min in chronically instrumented dogs.

Anesthetics, Intravenous↗
PubMed1997

[Thoracic epidural anesthesia--more than an anesthesia technique].

Thoracic epidural anaesthesia (TEA) faces growing interest as an adjuvant anaesthetic and postoperative analgesic regimen. The procedure allows a specific blockade of nociceptive reflex arches and may exert beneficial effects on stress-induced alterations of organ function. Myocardial blood flow to areas at risk is improved, and paradoxical reactions of atherosclerotic coronary arteries after sympathetic stimulation are suppressed. After cardiac surgery, TEA improved postoperative recovery and resulted in better haemodynamic stability and allowed earlier extubation. During vascular surgery, the graft occlusion rate was significantly decreased. The improved pulmonary function after TEA is due to superior pain relief which allows the patients to breathe and cough sufficiently. After upper abdominal surgery, TEA leads to improved recovery of gastrointestinal function which reduces the risk of bacterial translocation. Although lumbar epidural anaesthesia is preferred by many anaesthesiologists as there is no risk of traumatizing the spinal cord, many positive effects are forgone. With insufficient rostral spread of a lumbar epidural block above the fifth thoracic level, cardiac complications can occur due to reflex activation of sympathetic outflow in unblocked thoracic regions. When the contraindications are carefully observed, TEA can be safely performed in most patients.

Anesthesia, Epidural↗
PubMed1997

[Anesthesia for minimal invasive coronary surgery without employing extracorporeal circulation].

In the course of present reevaluation of aortocoronary bypass grafting a minimal invasive surgical procedure avoiding the use of cardiopulmonary bypass has been revised. It is suitable born for palliative treatment of patients with coronary multi-vessel-disease and compromised left ventricular function, and likewise for curative treatment of patients with single-vessel disease of a left coronary artery branch and unimpaired ventricular function. Avoiding possible complications of cardiopulmonary bypass can minimise morbidity and lethality of aortocoronary bypass grafting procedure and can help to lower costs. Anaesthesia for minimal invasive direct coronary artery bypass grafting needs an anaesthesiological concept differing from anaesthesia for conventional coronary artery bypass surgery. This concept, considering the special aims of minimal invasive technique, is discussed and demonstrated by means of case reports.

Anesthesia, General↗
PubMed1997

The effects of thoracic epidural anesthesia on functional recovery from myocardial stunning in propofol-anesthetized dogs.

The purpose of this investigation was to examine the effects of thoracic epidural anesthesia (TEA) on myocardial stunning during propofol anesthesia. Six dogs were chronically instrumented for measurement of left atrial, aortic, and left ventricular pressure, maximal rate of increase of left ventricular pressure, and myocardial wall-thickening fraction (WTF). Myocardial blood flow was determined with colored microspheres. Experiments were performed on separate days with 1) 10 min of left anterior descending artery (LAD) ischemia during propofol anesthesia without TEA, and 2) 10 min of LAD ischemia during propofol anesthesia with TEA. WTF was measured as baseline (BL) prior to propofol anesthesia and at predetermined time points until complete recovery from stunning. Propofol anesthesia caused a significant decrease of WTF in the LAD-perfused myocardium (LAD-WTF) compared to BL in awake animals. LAD ischemia led to a further significant decrease of LAD-WTF. There were no significant differences in LAD-WTF between the two experimental conditions at any of the time points measured. TEA did not change subendocardial blood flow in nonischemic myocardium. During ischemia neither the subendocardial/subepicardial nor the occluded/normal zone blood flow ratio were affected by TEA. After myocardial ischemia during propofol anesthesia TEA does not affect functional recovery of stunned myocardium in dogs.

Anesthesia, Epidural↗
PubMed1996

Long-chain triglycerides improve recovery from myocardial stunning in conscious dogs.

OBJECTIVES: Free fatty acid (FFA) oxidation is depressed in the postischaemic stunned myocardium and recovers in parallel with the normalization of contractile performance. Assuming a causal role for this metabolic disturbance in the pathogenesis of stunning, we questioned whether exogenous administration of high dose triglycerides during reperfusion of postischaemic myocardium, could improve its functional recovery. METHODS: Thirteen dogs were chronically instrumented to measure global and regional haemodynamics and to produce a 10 min episode of regional myocardial ischaemia. In 7 dogs, Intralipid 20% was administered i.v. during the reperfusion phase. Contractile recovery of stunned myocardium was compared with control saline treatments. The series were repeated in another 6 animals, but oxfenicine (CPT I inhibitor) preceeded Intralipid during reperfusion. RESULTS: Contractile recovery of stunned myocardium was faster and more extensive when Intralipid was administered during reperfusion than with saline treatment (wall thickening fraction 86 +/- 6% of preischaemic controls versus 52 +/- 11% at 90 min post-reperfusion; P < 0.05). Oxfenicine pretreatment completely abolished this beneficial effect. CONCLUSIONS: Exogenous administration of triglycerides during reperfusion of postischaemic myocardium improves functional recovery from stunning. This beneficial effect most likely operates through enhanced FFA availability and/or oxidation since it could be abolished by selective inhibition of the carnitine palmitoyl I enzyme.

Animals↗
PubMed1996

Thoracic epidural anesthesia improves functional recovery from myocardial stunning in conscious dogs.

The effects of thoracic epidural anesthesia (TEA) on the contractile performance of ischemic and postischemic myocardium have not been well investigated. The purpose of this investigation was to examine the effects of TEA on severity and duration of myocardial stunning in an experimental model for sublethal acute myocardial ischemia. Seven dogs were chronically instrumented for measurement of heart rate (HR), left atrial (LAP), aortic and left ventricular pressure (LVP), LV dP/dtmax' and myocardial wall-thickening fraction (WTF). An occluder around the left anterior descending artery (LAD) allowed induction of reversible LAD ischemia. TEA was performed with lidocaine 4 mg/kg through a chronically implanted epidural catheter at the second thoracic level. Regional myocardial blood flow was determined with colored microspheres. Two experiments were performed in a cross-over design on separate days: Experiment 1, induction of 10 min of LAD ischemia without TEA; and Experiment 2, induction of 10 min of LAD ischemia with TEA. WTF was measured at baseline (BL) and predetermined time points until complete recovery from ischemic dysfunction occurred. LAD ischemia caused a significant decrease of LAD-WTF with (-28% +/- 5.1% versus BL) and without TEA (-15.5% +/- 5.3% versus BL). After 3 h of reperfusion, WTF as percent of BL values was significantly higher with TEA (P < 0.001). BL values of WTF were reached after 24 h with TEA and after more than 48 h without TEA (P < 0.05). There were no significant differences for mean arterial pressure (MAP), heart rate (HR), LVP, LAP, and LVdP/dtmax between the groups during ischemia and reperfusion. In nonischemic myocardium TEA caused an increase of subendocardial blood flow. During ischemia neither the subendocardial/subepicardial nor the occluded/ normal zone blood flow was affected by TEA. TEA attenuates myocardial stunning in conscious dogs. This finding is consistent with data regarding a reduction of infarct size due to TEA.

Anesthesia, Epidural↗
PubMed1996

[The cardiovascular effects of sevoflurane].

The cardiovascular effects of sevoflurane as published from clinical and experimental studies are reviewed with respect to general haemodynamics and organ perfusion. Sevoflurane appears to be quite similar to isoflurane, with some minor exceptions. In adult patients and volunteers, sevoflurane has not been associated with increases in heart rate, whereas isoflurane and desflurane caused significant increases in heart rate at higher concentrations. The coronary vasodilatory potency of sevoflurane appears to be lower than that of isoflurane, and sevoflurane has not been associated with a reduction of blood flow to collateral-dependent myocardium in dogs with steal-prone anatomy. In several multi-center studies where patients with coronary artery disease or at high risk for coronary artery disease were randomised to receive either sevoflurane or isoflurane for cardiac or non-cardiac surgery, the incidence of myocardial ischaemia and infarction did not differ between treatment groups. In both human and animal models, sevoflurane preserves cerebral blood flow and reduces cerebral metabolic rate much like isoflurane. Considering its favourable pharmacokinetic properties, the introduction of sevoflurane into clinical practice appears to be a promising extension of the anaesthetic spectrum.

Adolescent↗