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Biomedical subjects

W Hess

Publications and source records attributed to W Hess.

At least 19 recordsLinked to original sources
PubMed1992

[The concentration of atrial natriuretic peptides (ANP). ANP in different sections of the circulation during atrial volume load with and without anesthesia].

We studied the effect of a volume load induced by a 45 degrees Trendelenburg position on atrial natriuretic peptide (ANP) secretion in awake and anaesthetized patients with coronary artery disease undergoing aortocoronary bypass surgery. ANP was measured in different parts of the circulation before and after induction of high dose fentanyl anaesthesia at fixed times prior to and after extracorporeal circulation. METHOD. In eight patients with coronary artery disease (NYHA classification II-III), who received neither diuretic nor positive inotropic therapy, ANP was measured in the various parts of the circulation: in a peripheral vein, a radial artery, in the pulmonary artery and in the coronary sinus. The measurements were made in the supine and 45 degrees Trendelenburg position. Measurements of mean arterial pressure (MAP), central venous pressure (RAP), pulmonary arterial pressure (PAP), pulmonary capillary wedge pressure (PCWP), cardiac index (CI) and heart rate (HR) were taken simultaneously. The measurements were taken in the awake patient, during steady-state high-dose fentanyl anaesthesia with 50% O2 in N2O and after extracorporeal circulation. RESULTS. Compared to measurements in a control group, ANP levels were significantly higher in all parts of the circulation in patients with coronary artery disease, although clinical symptoms of heart failure were absent. After extracorporeal circulation, significantly higher levels of ANP were found at all measurement sites; however the concentration gradient of ANP between coronary sinus and arterial or venous blood was reduced. In awake and anaesthetized patients a change in body position, causing a significant increase in filling pressures, did not produce an increase in ANP levels at all measurement sites. The induction of high-dose fentanyl anaesthesia did not have an influence on plasmatic ANP levels. CONCLUSION. The results of this study lead to the following conclusions: 1. ANP levels in patients with CAD are increased, even if clinical heart failure symptoms are absent. 2. ANP is secreted in the coronary vessels. Following dilution in the atrial blood, it is metabolized to inactive compounds in the periphery. 3. Basic ANP levels are not changed by high-dose fentanyl anaesthesia. Marked increases of the filling pressures do not correlate with atrial ANP levels either before or after induction of anaesthesia. 4. After extracorporeal circulation ANP levels are significantly increased in all parts of the circulation. The concentration gradient between coronary sinus blood, on the one hand, and arterial and venous blood on the other hand is reduced. This phenomenon is probably caused by an alteration in the metabolism of ANP during hypothermic extracorporeal circulation.

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PubMed1992

[Hemodynamics of coronary surgery patients following magnesium aspartate infusion].

Hypertension is a common phenomenon in patients undergoing aortocoronary bypass grafting. This hypertension increases myocardial oxygen consumption and can be prevented by application of vasodilators. A possible cause is activation of the renin angiotensin system. Magnesium is a potent vasodilator and has a beneficial effect after myocardial ischaemia. The study was performed to analyse the influence of magnesium infusion on the haemodynamic status and plasma renin activity in patients undergoing aortocoronary bypass grafting. METHODS. Eighteen patients (NYHA classification II-III) undergoing bypass surgery were divided into two groups, a magnesium and a control group. The magnesium group (n = 9) received 0.8 mEq/kg per h magnesium aspartate as an infusion for 15 min while still awake. After induction of anaesthesia, the magnesium infusion was reduced to 0.2 mEq/kg per h and stopped after aortic cannulation was completed. Plasma magnesium levels and concentrations within erythrocytes were measured. Anaesthesia was induced by flunitrazepam (0.01 mg/kg), fentanyl (0.005 mg/kg) and pancuronium (0.1 mg/kg). After intubation, patients were normoventilated with N2O/O2 = 1:1 and isoflurane (0.5-1.0 vol%). Additional doses of fentanyl (0.0025 mg/kg) were injected before the incision and before sternotomy. Mean arterial pressure, heart rate, cardiac index, total peripheral resistance, pulmonary vascular resistance, mean pulmonary arterial pressure, pulmonary capillary wedge pressure, left ventricular stroke work index, right ventricular stroke work index, intrapulmonary shunt and plasma renin activity were evaluated at five predefined points: (1) prior to magnesium infusion; (2) after magnesium infusion; (3) 10 min following induction of anaesthesia under steady-state conditions; (4) after sternotomy; (5) after aortic cannulation. RESULTS. Concerning the haemodynamic parameters (MAP, RAP, PAP, PCWP) no significant difference between the two groups could be demonstrated. In the control group peripheral resistance (TPR) was higher following sternotomy and aortic cannulation than in the magnesium group. Magnesium prevented decrease of the cardiac index (CI) under steady-state conditions, during sternotomy and following aortic cannulation. Left and right ventricular stroke work indexes (LVSWI and RVSWI) were higher in the magnesium group. Plasma renin levels were not significantly different between the two groups. CONCLUSION. Patients undergoing cardiac surgery benefit from magnesium administration in the pre-bypass phase. Due to its vasodilating effect, magnesium lowers the output impedance of the left ventricle and improves cardiac pumping function. It opposes detrimental cardiovascular responses to sternotomy and following aortic cannulation. Also of importance is the advantageous effect of magnesium on cardiac arrest elicited by cardioplegia and for reactivation of the ischaemic myocardium.

Aspartic Acid↗
PubMed1992

[Successful therapy of a cardiac arrest during accidental hypothermia using extracorporeal circulation].

We report the case of a 59-year-old woman suffering from profound accidental hypothermia promoted by intoxication with codeine, sedatives, and a beta-blocking agent ingested in a suicidal attempt. Treatment was further complicated by ventricular fibrillation and asystole that was refractory to therapeutic interventions. The comatose patient (Glasgow score 3) was found outdoors in rainy weather--environmental temperature approximately 10 degrees C (50 degrees F)--by children. The skin was rosy when the emergency team arrived. The respiratory rate was low and the ECG showed sinus rhythm with a heart rate of 28/min. No arterial pulsations were detectable, even at the carotid and femoral sites. Because catecholamine therapy failed to increase the heart rate, the patient was suspected to be profoundly hypothermic. After confirming core hypothermia with a rectal temperature of 25 degrees C (77 degrees F) at the initial receiving hospital, transfer to an institution with cardiac surgery facilities was initiated. During this transport and after arrival, ventricular fibrillation occurred at decreasing intervals followed by asystole, which was refractory to large doses of epinephrine. The patient was transferred to the operating room under continuous resuscitation maneuvers and cardiopulmonary bypass was instituted via the femoral vessels. After 110 min of extracorporeal circulation (ECC, flow 4.5 l/min) normothermia was achieved and the asystole reverted spontaneously to sinus rhythm. The patient's course was subsequently complicated by worsening pulmonary gas exchange with signs of pulmonary edema on X-ray films and cardiac failure, which was treated successfully with epinephrine and dopamine. No neurological deficits were detectable after consciousness had returned.(ABSTRACT TRUNCATED AT 250 WORDS)

Extracorporeal Circulation↗
PubMed1991

Comparison of severity of illness indicators in an intensive care unit.

Meaningful comparison of patient outcomes requires an assessment of the severity of illness for the patients being compared. The more severe the underlying illness, the worse the expected outcome. We studied several severity of illness indicators derived from different methodologies in a medical intensive care unit. We compared the Acute Physiologic and Chronic Health Evaluation II, the accepted benchmark indicator for intensive care units, with one complex indicator, Computerized Severity Score, and three simpler indicators, Comorbidity, McCabe-Jackson, and American Society of Anesthesiologists. We found that all correlated well with a comorbidity index. We conclude that the Acute Physiologic and Chronic Health Evaluation II, the Computerized Severity Score, and the McCabe-Jackson scoring systems appear to be comparable predictors of comorbidity in a medical intensive care unit. Selection of a severity indicator will depend on the resources available and the intended uses.

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PubMed1990

The influence of pancuronium and vecuronium combined with balanced anaesthesia on haemodynamics and myocardial oxygen balance.

The effects of the non-depolarizing muscle relaxants pancuronium (Pancuronium) and vecuronium (Norcuron) (0.1 mg/kg) on myocardial blood flow, myocardial oxygen consumption, myocardial lactate balance, cardiovascular dynamics and electrocardiogram were studied in two groups of eight patients undergoing coronary artery bypass surgery. After induction of anaesthesia with 0.015-0.02 mg/kg flunitrazepam, isoflurane (0.5 vol%) and N2O/O2 (l/l), neuromuscular blockade was induced with pancuronium or vecuronium (0.1 mg/kg) combined with a single dose of 0.005 mg/kg fentanyl. Haemodynamic measurements were performed and the electrocardiogram was recorded before anaesthesia, in steady-state anaesthesia, after relaxation with pancuronium or vecuronium combined with fentanyl, and after intubation. The haemodynamic data consisted of heart rate, cardiac index, stroke volume index, mean arterial pressure, total peripheral resistance, pulmonary arterial pressure, pulmonary capillary wedge pressure, right atrial pressure, myocardial blood flow, coronary vascular resistance, myocardial oxygen consumption, coronary aterio-mixed venous content difference, myocardial lactate extraction and rate pressure product. In the vecuronium group, heart rate decreased significantly more (21%) than in the pancuronium group (9%). Therefore myocardial oxygen consumption (48% resp. 35%) and coronary blood flow (31% resp. 18%) decreased more in the vecuronium than in the pancuronium group. The higher metabolic demand in the pancuronium group induced a significantly lower coronary vascular resistance, because the decrease in coronary perfusion pressure was similar in both groups. None of the other haemodynamic parameters differed significantly in either patient group. We did not observe ST-segment depressions or elevations in the ECG, increases in PCWP or myocardial lactate production. Therefore extended myocardial ischaemia can be excluded in our patients who received pancuronium or vecuronium for neuromuscular blockade.

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PubMed1990

[Hemodynamics and myocardial energy balance in coronary surgery patients during high-dose fentanyl-pancuronium anesthesia and modified neurolept-pancuronium anesthesia].

In 8 patients with coronary artery disease (CAD) classed as NYHA II or III, anesthesia was induced with high-dose fentanyl (0.05 mg/kg) and pancuronium (0.1 mg/kg). The patients were ventilated normally with the aid of a mask (O2: air 1:1, tidal volume 10 ml/kg with a rate of 10/min) for 5 min and then intubated. In 8 further patients with CAD NYHA class II or III, anesthesia was induced with 0.02 mg/kg flunitrazepam, N2O/O2 1:1 and isoflurane 0.5 vol%; they were relaxed with pancuronium (0.1 mg/kg) in combination with a bolus of 0.005 mg/kg fentanyl. These patients were also ventilated normally for 5 min and then intubated. Measurements of cardiovascular dynamics included cardiac output (CO), heart rate (HR), arterial pressure (AP), pulmonary artery pressure (PAP), pulmonary capillary wedge pressure (PCWP), right atrial pressure (RAP), myocardial blood flow (MBF), and arterial and coronary sinus oxygen and lactate contents. Cardiac index (CI), stroke volume index (SVI), total peripheral resistance (TPR), myocardial oxygen consumption (MVO2), coronary vascular resistance (CVR), coronary perfusion pressure (CPP), myocardial oxygen content difference (AVDO2cor) and myocardial lactate extraction rate (LE) were calculated from standard formulas. Measurements and an electrocardiogram were taken before anesthesia, after induction of anesthesia and after intubation. The hemodynamic parameters HR, AP, CI, CPP were relatively stable in patients anesthetized with high-dose fentanyl and pancuronium, whereas we found greater decreases in these parameters with the balanced anesthesia technique. Determinants of myocardial oxygen demand were higher in the high-dose fentanyl group; therefore, myocardial blood flow and oxygen consumption did not decrease to the same extent as in the balanced anesthesia group.(ABSTRACT TRUNCATED AT 250 WORDS)

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PubMed1989

Effects of amrinone on the right side of the heart.

Unlike the left ventricle, the right ventricle is a thin-walled, low-pressure, volume-displacement pump that ensures adequacy of left ventricular filling and maintains a low pressure in the venous system. In healthy human subjects, there is no burden for right ventricular systolic emptying, because normal pulmonary vessels have a low impedance and show a passive recruitment when cardiac output increases. However, under a pathological condition like right-sided heart failure, the right ventricle may exert profound influences on the circulatory state. Right-sided heart failure most often results from primary or secondary pulmonary arterial hypertension. Pharmacologic vasodilation of the hypertensive pulmonary vascular bed is an ideal therapy for right-sided heart failure. The bipyridine derivative amrinone has positive inotropic and direct vasodilator properties, and therefore seems suitable for the therapy of right ventricular dysfunction accompanied by pulmonary arterial hypertension. In one study, 12 patients with right ventricular failure due to mitral valve stenosis were evaluated, and it was found that amrinone increased cardiac output by 25% and decreased pulmonary artery pressure by 30% to 50%. In a second study, the hemodynamic properties of amrinone versus sodium nitroprusside were compared in patients with aortic or mitral valve failure (n = 17), when both agents lowered systemic vascular resistance equally. Pulmonary vascular resistance decreased significantly (25%) only in the amrinone group.

Amrinone↗
PubMed1989

[The effect of pancuronium and norcuron on hemodynamics, coronary circulation and myocardial oxygen consumption in coronary surgery patients].

The effects of the non-depolarizing muscle relaxants pancuronium (Pancuronium) and vecuronium (Norcuron) (0.1 mg/kg) on myocardial blood flow, myocardial oxygen consumption, myocardial lactate balance, cardiovascular dynamics and electrocardiogram were studied in two groups of eight patients undergoing coronary artery bypass surgery. After an introduction of anaesthesia with 0.015-0.02 mg/kg rohypnol, isoflurane (0.5 Vol%) and N2O/O2 neuromuscular blockade was induced with pancuronium or vecuronium combined with a single dose of 0.005 mg/kg fentanyl. Measurements and electrocardiogram were performed before anaesthesia, in steady state of anaesthesia and after relaxation with pancuronium or vecuronium, combined with fentanyl. The measurements consisted of heart rate (HR), cardiac index (CI), stroke volume index (SVI), mean arterial pressure (AP), total peripheral resistance (TPR), pulmonary arterial pressure (PAP), pulmonary capillary wedge pressure (PCWP), right atrium pressure (RAP), myocardial blood flow (MBF), coronary vascular resistance (CVR), myocardial oxygen consumption (MVO2), coronary ateriomixed venous oxygen content difference (AVDO2cor), myocardial lactate extraction (LE) and rate pressure product (RPP). In the vecuronium group heart rate (HR) decreased significantly greater (21%) than in the pancuronium group (9%). Therefore myocardial oxygen consumption (MVO2) and coronary blood flow (CBF) diminished more in the vecuronium (48% resp. 35%) than in the pancuronium group (31% resp. 18%). The higher metabolic demand in the pancuronium group induced a significantly lower coronary vascular resistance (CVR). All the other hemodynamic parameters did not differ significantly in both patients groups. In all the patients we could not observe ST-segment depressions or elevations in the ECG, increases of PCWP or myocardial lactate productions.(ABSTRACT TRUNCATED AT 250 WORDS)

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PubMed1988

[Amrinone (Wincoram)--a new positive inotropic and vasodilator agent].

The bipyridine derivative amrinone is a specific phosphodiesterase III blocking agent. In vitro and in vivo studies show a dose-dependent increase in myocardial contractility induced by amrinone. In patients with congestive heart failure, the inotropic and vasodilator effects of amrinone contribute to cardiac improvement. When amrinone is used, the increase in myocardial oxygen consumption due to increased contractility is offset by the reductions in preload and afterload. In hearts with very high wall tension, myocardial oxygen consumption may even decrease with amrinone. Amrinone therapy is not accompanied by significant increases in heart rate. Tachyphylaxis has not been observed. The elimination half-life ranges between 2.5 and 3.5 h. A large quantity of amrinone is excreted unchanged, and therefore in cases of renal impairment the possibility of cumulation exists. The main adverse reaction of amrinone is a reversible thrombocytopenia induced by a dose-dependent decrease in platelet survival time. Therefore, frequent platelet counts are necessary when amrinone is administered. Numerous studies in patients with chronic congestive heart failure confirmed the beneficial hemodynamic effects of amrinone. Experience in the treatment of acute perioperative heart failure with amrinone are still limited, but the present results are encouraging; an additive effect of amrinone to catecholamines seems especially promising in the therapy of severe postoperative low-cardia-output syndrome.

Amrinone↗
PubMed1988

[Pulmonary artery rupture caused by a Swan-Ganz catheter during heart surgery. A successful therapeutic procedure].

A patient with mitral valve stenosis (NYHA IV) suffered a pulmonary artery rupture after valve replacement and weaning from bypass. This event coincided with the measurement of pulmonary capillary wedge pressure. Anticoagulation aggravated the endobronchial bleeding to a near fatal outcome. By intubating with a double-lumen endobronchial tube and clamping the right pulmonary artery, the pulmonary hemorrhage and its complications could be controlled. After antagonizing the heparin dose and supporting the right heart with epinephrine bleeding was reduced substantially, following which the right pulmonary artery was declamped. In older patients or patients with pulmonary hypertension the following procedures for preventing pulmonary artery rupture should be taken: before inflating the balloon the catheter should be withdrawn into a large vessel; after inflation the balloon the catheter can be advanced to the wedge position.

Catheterization, Swan-Ganz↗
PubMed1987

Preliminary results with amrinone in perioperative low cardiac output syndrome.

The hemodynamic parameters of 24 cardiosurgical patients with low cardiac output syndrome (LCOS) after weaning from bypass were evaluated retrospectively. These patients were additionally treated with amrinone if the conventional therapy with catecholamines and vasodilators did not reach satisfying hemodynamic results. 14 patients underwent aorto-coronary bypass surgery, 10 patients underwent valve repair. Their disability by NYHA class was III and IV. One third of these patients died between the first and the fifth day postoperatively. Hemodynamic assessment was performed after weaning from bypass and after the start of amrinone therapy and was continued the first 24 hours in the intensive care unit, as long as the patients were dependent on amrinone. The platelet count was determined every eight hours after surgery. Under the supplementary therapy with amrinone we found an increase of the arterial pressure and cardiac index and decrease of heart rate and total peripheral resistance. These salutary hemodynamic changes could be sustained in the postoperative period. The platelet count dropped from nearly 100,000/mm3 in mean (first measurement post-op.) to 58,000 in mean (the lowest value during 48 hours on intensive care). 2 patients showed a decrease to 11,000 and 15,000/mm3 with petechial bleedings. These findings indicate that on the one hand amrinone seems to be a promising drug in cases of severe LCOS when conventional therapy fails, but on the other hand a marked decrease of the platelets can occur. Therefore a frequent control of platelet count has to be performed when using amrinone.

Aged↗
PubMed1987

[Affinity of oxygen for hemoglobin--its significance under physiological and pathological conditions].

Hemoglobin as a vehicle for oxygen carries roughly 65 times the volume of oxygen that would otherwise be transported by simple solution in plasma. Conformational shifts of the molecule induce a cooperative oxygen-hemoglobin affinity. This property is reflected in the sigmoidal shape of the oxygen-hemoglobin dissociation curve. The affinity of hemoglobin is affected by temperature, hydrogen ions, carbon dioxide, and intraerythrocytic 2,3-DPG, with all these factors mutually influencing each other. Physiologic conditions associated with shifts in hemoglobin-oxygen affinity are oxygen uptake in the lung, oxygen delivery in the capillaries, and particularly oxygen delivery in working muscle, diaplacental oxygen transfer, and the regulation of erythropoesis. Hemoglobin-oxygen affinity attains pathological significance for oxygen supply during respiratory or metabolic alkalosis when the hemodynamic and tissue responses of the individual are limited: the increased affinity can critically lower capillary oxygen tension. Methemoglobin and carbon monoxide shift the oxygen dissociation curve to the left, so that intoxication with both substances reduces both total oxygen capacity and oxygen delivery of the remaining hemoglobin able to bind oxygen. This effect of methemoglobin and carbon monoxide must be considered in intensive care of intoxicated victims. Transfusions of large volumes of stored red cells, whose hemoglobin shows high affinity, can force the capillary oxygen tension down, especially in patients with impaired cardiac performance. The lowered oxygen affinity of patients with chronic renal disease and anemia must be preserved by avoiding an increase in the acidotic plasma pH. In the neonate, hemoglobin possesses a high affinity for oxygen physiologically; the hemodynamic reserve of the neonate is limited. Therefore, the hemoglobin content plays a crucial role in oxygen transport capacity during the initial months of extrauterine life. Consequently, red cell transfusion must be started much earlier in neonatal surgery than in adults. The red cells must be fresh, or at best "rejuvenated". Normally, oxygen affinity is not relevant for oxygen supply, but the position of the oxygen-hemoglobin dissociation curve may be a critical factor in the situations described above, particularly when blood flow is additionally restricted.

Hemoglobins↗
PubMed1987

[Evoked potentials in intracranial operations: current status and our experiences].

Intraoperative neuromonitoring, especially evoked potential monitoring, has gained interest in recent years for both the anesthesiologist evaluating cerebral function and the neurosurgeon wishing to avoid neuronal lesions during intracranial operations. Before evoked potential monitoring can be introduced as a routine method of intraoperative management, experience with this method particularly in intensive care units, is imperative. We recorded evoked potentials with the Compact Four (Nicolet) and Basis 8000 (Schwarzer Picker International) computer systems. Preoperative derivations should be done with the same apparatus used intraoperatively and parameters of peri- and intraoperative derivations should not be changed. The patient's head must be fixed in a Mayfield clamp in order to avoid artefacts during trepanation. The possible artefacts due to apparatus, patient, or anesthesia are summarized in the tables. The derivations of evoked potentials should be supervised by a person who is not involved in the anesthesia or the surgical procedure; this condition may change in the future with full automatization of the recording technique and alarms. Good communication between surgeon, anesthesiologist, and neurophysiological assistant is a prerequisite. The modality is chosen in accordance with the affected neuronal system: visual-evoked potential (VEP) monitoring in the management of processes affecting the visual pathway, brain stem auditory-(BAER) and somatosensory-evoked potential (SSEP) monitoring in lesions affecting these pathways, in particular space-occupying lesions of the posterior fossa. VEP monitoring may be useful, but we observed alterations of the responses without changes in the level of anesthesia or manipulation of the visual pathways. In space-occupying processes of the cerebellopontine angle, BAER could not be developed in nearly all cases because the large underlying tumor had caused the disappearance of waves II-V. In these cases SSEP monitoring could be carried out. Despite these difficulties, evoked potential monitoring seems useful. We believe, however, that it is not routinely used in operating rooms at present because alterations of the responses can be due to different causes; for the neurosurgeon, the problem as to which interdependent degrees of alteration in evoked potentials are related to neuronal disturbances remains unsolved.

Brain↗