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Biomedical subjects

M Menzel

Publications and source records attributed to M Menzel.

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

Validating of a transoesophageal ultrasonic-Doppler-probe to the detection of air in the venous blood.

OBJECTIVES: The aim of this study was to compare the sensitivity of a newly applied transoesophageal ultrasonic Doppler sensor for detection of air with the traditional precordial ultrasonic Doppler sensor in clinical use. METHODS: We studied 16 patients undergoing neurosurgical procedures in a sitting position. Two ultrasonic Doppler devices were compared as to their ability to detect venous air embolisms (VAE): transoesophageal (ODM II, co. Abbott) versus a precordial ultrasonic Doppler sensor (Parks Medical Electronics Inc.). After establishing general anaesthesia and endotracheal intubation, we applied an ultrasonic Doppler sensor to the right sternal border of the patient's chest and inserted an ultrasonic Doppler probe into the oesophagus. With the patient in the sitting position, microparticularly d-galactose was injected to verify the efficacy of both ultrasonic Doppler devices. RESULTS: Using ODM II by positioning the probe toward the azygos vein, a dosage of 1 ml microparticularly d-galactose was detected in every patient. When adjusting the ODM II-probe on the right myocardial wall or using the precordial ultrasonic Doppler sensor, the administration of microparticularly d-galactose was detected by the devices in only 11 patients. CONCLUSIONS: This study demonstrates that a transoesophageal ultrasonic Doppler sensor (ODM II) is more efficient than the precordial ultrasonic Doppler sensor for monitoring patients who are at risk of VAE by sonification of the azygos vein.

Air↗
PubMed1998

Temperature of the cerebrovenous blood in a model of increased intracranial pressure.

UNLABELLED: Hypothermia has a considerable protective effect during brain ischemia. On the other hand small increases of brain temperature have a remarkable effect on the exacerbation of neurological damage following an ischemic event. Hyperthermia of the brain tissue after severe head injury is described. The effect of acutely increased intracranial pressure on cerebrovenous blood temperature is not described yet. The aim of this study was to investigate the relationship between temperature in the cerebrovenous compartment (Tcv) and changes of the CPP in an animal model of raised intracranial pressure. METHODS: A thermocouple was inserted in the sagittal sinus in 9 pigs under general anesthesia. By stepwise inflating a supracerebral and infratentorial placed balloon catheter intracranial pressure (ICP) was increased and CPP concomitantly decreased. The central body temperature was measured simultaneously in the abdominal aorta (Ta) with a second thermocouple. RESULTS: In our model th Tcv was lower than Ta at the beginning of the ICP increase. The mean difference between Ta and Tcv, (delta Ta-cv) was 0.86 degree C (+/- 0.44) prior to ICP increase and 1.19 degrees C (0.58) at the maximum ICP increase. Thus, delta Tav increased during CPP reduction. This relation was represented by an adjusted R(square) of r2 = 0.89 (p < 0.001). CONCLUSIONS: The CPP decrease, caused by an increasing ICP, results in changes of the cerebrovenous blood temperature. Interpreting the present results the experimental situation of a relative colder cerebral compartment in comparison to the central body temperature has to be considered. However, the results imply, that simultaneous temperature monitoring of the central body temperature and the cerebrovenous blood temperature is an additional source of information about relative changes of the CBF.

Animals↗
PubMed1998

[Cisatracurium in patients with compromised kidney function. Pharmacodynamic and intubation conditions under isoflurane-nitrous oxide anesthesia].

OBJECTIVES: The choice of cisatracurium, especially for patients with organ dysfunction, seems to be beneficial, because of organ-independent Hofmann-elimination and less histamine release propensity. This study was designed to investigate pharmacodynamics and intubating conditions after bolus administration of 0.15 mg/kg cisatracurium (3 x ED95) in patients with renal failure and maintained with isoflurane/N2O in oxygen. METHODS: 20 patients with renal failure and 19 patients with normal renal function were studied. Anaesthesia was induced with fentanyl (2-3 micrograms/kg) and thiophentone (4-7 mg/kg). After rapid bolus administration of 0.15 mg/kg cisatracurium (3 x ED95), onset time and intubating conditions were assessed. Clinical duration (DUR 25%), recovery index and duration 90% were investigated by acceleromyography. Changes of mean arterial blood pressure and/or heart rate > or = 20% were defined as clinically significant. RESULTS: The onset time (3.1 +/- 0.8 min) was shorter in patients without renal failure (Cis-1) than in patients with normal renal function (3.6 +/- 0.8 min), but without statistical significance. Intubating conditions, scored according to a 3-step scale, were slightly better in patients with normal renal function. Other pharmacodynamic parameters did not differ significantly. However, a small tendency to a prolonged recovery with a wide inter-individual variety was characteristic for patients with renal failure. Regarding the hemodynamic actions, only minor individual cardiovascular changes occured. No clinical evidence of histamine release was observed in any patient. CONCLUSIONS: The result of this clinical study suggest, that cisatracurium is a suitable choice for patients with renal failure. The necessity for an intraoperative neuromuscular monitoring is given by the marked heterogeneity in the recovery parameters in patients with renal failure.

Adolescent↗
PubMed1998

Extended neuromonitoring: new therapeutic opportunities?

In order to optimize therapy for the injured brain it is desirable to continuously monitor substrate delivery in the critically ill patient. Interruption of substrate delivery is a major factor of the great vulnerability to ischemic damage, which affects a majority of patients after severe head injury, stroke or subarachnoid hemorrhage. An approach to protecting the brain during ischemia is to increase the delivery of oxygen via residual blood flow through ischemic tissue. Hypothermia is also an important means of protecting brain cells from the deleterious effects of ischemia, after severe head injury, because it reduces metabolic demands. In this study we continuously measured brain oxygen, brain CO2, brain pH and brain temperature, as well as hourly brain glucose and lactate. A multiparameter sensor was inserted into brain tissue, via a three lumen bolt, along with a ventriculostomy catheter and a microdialysis probe in 60 severely head injured patients. Brain oxygen delivery was increased by stepwise increase of inspired oxygen (FiO2) from 30% to 60% to 100% over a period of 6 h, in order to test the effect of enhanced oxygen tension, on tissue oxygen. In most patients brain oxygen was initially low, and progressively increased, over the monitoring period, to a steady state level, around 30-40 mmHg. In those who died or remained vegetative, brain oxygen fell to anerobic levels. Episodes of increased ICP (n = 25), hypotension (n = 15), and respiratory difficulties (n = 9) caused an immediate increase in brain CO2. Multiple logistic regression analysis showed brain oxygen to be the strongest predictor for outcome in these patients. By increasing FiO2, an increase in oxygen delivery of more than 100%, and a simultaneous decline in lactate production was seen (p < 0.01). Brain temperature was closely related to rectal temperature, brain oxygen, and cerebral blood flow. Patients who were spontaneously hypothermic had a poor outcome (p < 0.01). A fuller understanding of dynamic factors affecting brain metabolism and substrate delivery may be obtained with extended neuromonitoring.

Adolescent↗
PubMed1998

Comparison between continuous brain tissue pO2, pCO2, pH, and temperature and simultaneous cerebrovenous measurement using a multisensor probe in a porcine intracranial pressure model.

Local brain tissue oxygenation (p(ti)O2) and global cerebrovenous hemoglobin saturation (SjO2) are increasingly used to continuously monitor patients after severe head injury (SHI). In patients, simultaneous local and global oxygen measurements of these types have shown different results regarding the comparability of the findings during changes in CPP and ICP. This is in contrast to theoretical expectations. The aim of this study was to compare p(ti)O2 measurement with cerebrovenous oxygen partial pressure measurement (p(cv)O2) in an animal intracranial pressure model. To this end, a multisensor probe was placed in the left frontoparietal white matter to measure p(ti)O2, pCO2 (p(ti)CO2), pH (pH[ti]), and temperature (t[ti]) while simultaneously measuring these same parameters (p(cv)O2, p(cv)CO2 pH(cv), t[cv]) in the sagittal sinus of 9 pigs under general anesthesia. By stepwise inflating a balloon catheter, placed in supracerebellar infratentorial compartment, ICP was increased and CPP was decreased. The baseline levels of p(ti)O2, p(ti)CO2, and pH(ti) in the noninjured brain tissue showed more heterogeneity compared to the findings in cerebrovenous blood. Both, p(ti)O2 and p(cv)O2 were significantly correlated to the induced CPP decrease. PCO2 was inversely correlated to the course of CPP in both measurement compartments. Temperature measurement showed a positive correlation with CPP in both compartments. These findings demonstrate that brain tissue oximetry and cerebrovenous PO2 measurement are sensitive to CPP changes. The newly available continuous parameters in multisensor probes could be helpful in interpreting findings of cerebral oxygen measurement in man by analyzing the interrelationship of these parameters.

Anesthesia, General↗
PubMed1997

[Cerebrovascular fiberoptic catheter oximetry in an intracranial pressure model in swine. New aspects of a clinical routine].

UNLABELLED: The reliability of continuous fibreoptic oximetry in cerebral venous blood and its correlation with intracranial and cerebral perfusion pressures (pressure-volume curve) were examined in an experimental porcine study. METHODS: The pressure in the infratentorial compartment of 13 domestic pigs (18-24 kg) was gradually increased by inflating a Fogarty balloon catheter placed on the surface of the right cerebellar hemisphere and below the tentorium. Single volumes of 0.4 ml saline were injected into the inflatable balloon at 1-min intervals up to a total volume of 7 ml. Intracranial pressure (ICP), arterial blood pressure, cerebral perfusion pressure (CPP), and cerebral venous saturation measured continuously by fibreoptic oximetry and intermittent blood-gas analyses (SjO2 superior sagittal sinus) were monitored during balloon inflation. All data were down-loaded onto a PC and evaluated off-line by a commercial statistical software package. RESULTS: Over the whole pressure-volume curve, two phases of SjO2 behaviour were registered by continuous fibreoptic oximetry (Oximetrix 3, Abbott) (Fig. 1). CPP ranges of less than 50% reduction from the initial value showed a linear correlation (rmittl. = 0.712, P < 0.01) between both parameters (CPP-SjO2). In CPP ranges below a crucial point of about 50 mmHg no such correlation was found (rmittl = 0.176, P < 0.5). In contrast, in 3 pigs a very good correlation was found between CPP and SjO2 over the whole pressure-volume curve as measured by blood-gas analyses of samples from the cerebrovenous catheter (rmittl. = 0.84, P < 0.05). DISCUSSION: We conclude that in physiological CPP ranges down to 50 mmHg, SjO2 measurement is a reliable method of detecting oxygen desaturation in cerebrovenous blood. Below that CPP value, the fibreoptic catheter showed repeated false-high oxygen saturation values. The accuracy of SjO2 measurement seems to depend on sufficient cerebral blood flow (CBF): with decreasing CBF the amount of cerebral venous outflow is diminished. We believe this is why we could not find a correlation in low CPP ranges with the oximetry catheter. This flow-dependency is a new aspect of fibreoptic cerebrovenous oximetry. The authors recommend that rising SjO2 values after desaturation events be confirmed by blood-gas analyses.

Animals↗
PubMed1997

[Continuous measurement of jugular venous blood gas. A case of subarachnoid bleeding].

INTRODUCTION: Recently, a compact multisensor device 0.5 mm in diameter has become available with a miniaturised Clark electrode for measuring blood oxygen tension and two optical fibres for measuring CO2 tension, pH, and temperature (Paratrend 7, Biomedical Sensors, High Wycombe, UK). We used this new probe for continuous blood gas monitoring in the jugular bulb as an alternative to the commonly used fiberoptic spectrophotometric oximetric measurement of haemoglobin saturation. RESULTS: A 64-year-old patient was admitted for surgery of a right-sided intracranial aneurysm. During surgery, with no artefacts or evidence of catheter drift, a normal jugular venous pO2 (pjvO2) of 39 +/- 3 mmHg was measured. Over the period of weaning, two declines in pjvO2 occurred (22.5 and 18.7 mm Hg) associated with a decline in CO2 tension and a rise in pH. We treated these events successfully by analgosedation, controlled ventilation with an inspired oxygen fraction of 70%, and elevation of the mean arterial blood pressure to over 100 mmHg. Extubation was possible about 24 h later. Furthermore, 3 h after extubation pjvO2 values could be monitored without difficulty despite movement of the patient. DISCUSSION: The technique of polarographically measuring pjvO2 with a Clark-type probe appears superior to fibreoptic jugular venous oximetry due to the clearly lower incidence of faulty measurements, especially in the intensive care unit, where patients undergo frequent nursing interventions and tend to awaken. We did not even observe artefacts due to patient movement after extubation. A limitation of the new multisensor system might be the distance of 4 cm between the sensor tip and the end of the insertion catheter, which makes samples drawn for in vitro blood gas analyses to control the continuous monitoring less comparable. Improvements in the construction of the probe are recommended.

Blood Gas Analysis↗
PubMed1997

Continuous monitoring of the partial pressure of oxygen in cerebral venous blood.

OBJECTIVE: Clinical oxygen monitoring in the injured brain is somewhat difficult. However, ischemia is one of the major factors responsible for secondary tissue damage after head injury or subarachnoid hemorrhage. Therefore, the aim of the present study was to investigate the value of continuously monitoring the partial pressure of oxygen in cerebral venous blood (PcvO2) during changes in intracranial pressure (ICP). METHODS: In eight domestic pigs with Clark type probes placed in the posterior third of the superior sagittal sinus, PcvO2 was continuously registered while ICP was stepwise elevated by an inflatable balloon placed below the tentorium. Arterial blood pressure was continuously monitored, cerebral perfusion pressure (CPP) was calculated, and arterial partial carbon dioxide pressure and partial pressure of oxygen were registered intermittently. RESULTS: The mean intraparenchymal ICP before the start of balloon inflation was 5 +/- 1 mm Hg, the mean CPP was 80 +/- 15 mm Hg, and the mean PcvO2 was 36 +/- 3 mm Hg. At maximum ICP elevation, CPP decreased to 20 +/- 12 mm Hg, PcvO2 decreased to 10 +/- 6 mm Hg, and ICP increased to 90 +/- 10 mm Hg. Strong linear correlations between ICP and PcvO2 and between CPP and PcvO2 were revealed, and mean correlation coefficients of 0.89 for ICP/PcvO2 and 0.73 for CPP/PcvO2 were calculated. CONCLUSION: The present study demonstrates that polarographic PcvO2 monitoring in the superior sagittal sinus is a reliable method for the early detection of reduced CPP during ICP elevation. This technique is capable of registering the global oxygen supply and oxygen consumption of the brain. It seems superior to jugular venous oxymetry and is better suited for clinical use because of a somewhat low artifact susceptibility.

Animals↗
PubMed1997

Comparison between continuous brain tissue measurement and cerebrovenous measurement of pO2, pCO2 and pH in a porcine intracranial pressure model.

Simultaneous oxygen measurements in brain tissue (p(ti)O2) and hemoglobin saturation measurement in cerebrovenous blood in patients after severe head injury have shown different results regarding the comparability of the findings in respect to CPP and ICP. This is contrast to theoretical expectations. The aim of this study was to compare continuous ptiO2 measurement with oxygen partial pressure measurement in sagittal sinus (pO2cv) during simultaneously performance in an animal intracranial pressure model. For continuous measurement we used a newly available multisensor probe. We placed a Paratrend 7 probe (BSL, High Wycombe, UK) in the left frontoparietal white matter and measured ptiO2, pCO2 (ptiCO2) pH (pHti) and temperature (t(ti)) while simultaneously measuring these parameters (pcvO2, pcvCO2, pHcv, tcv) in the sagittal sinus in 9 pigs under general anaesthesia. A fogarty balloon catheter was placed supracerebellar infratentorial and inflated stepwise in order to increase ICP. The baseline levels of pO2ti, pCO2ti und pHti in the non-injured brain tissue showed a more extended heterogeneity compared to the findings in cerebrovenous blood. Both, pO2ti and pO2cv were significant correlated to the CPP decrease. In both measurement compartments pCO2 was inverse correlated to the course of CPP and seems the course of pH mainly to determine. p(ti)O2 as well as p(cv)O2 showed a close correlation to the CPP course and have proven to be qualified to indicate metabolic information about the relation of cerebral blood flow and metabolic cerebral demands. The measurement of CO2 tension in both measurement compartments shows a distinct heterogeneity of the absolute values and the results are only weak correlated to CPP. Metabolic influence on this parameter could not be revealed in the used experimental approach.

Animals↗
PubMed1997

Continuous pO2 and pCO2 measurement in brain tissue and cerebrovenous blood during different inspired oxygen settings. A porcine model.

The clinical use of brain tissue oxygen measurement in patients with severe head injury is increasing. It is important to compare the findings in brain tissue with jugular bulb oximetry, to obtain normal values and to find out limitations of the method. We evaluated a newly available multisensor probe simultaneously in the brain tissue and in the sagittal sinus in a porcine animal model. We placed the Paratrend 7-probe (BSL, High Wycombe, UK) in the left frontoparietal white matter and measured pO2 (ptiO2), pCO2 (pti CO2), pH and temperature while simultaneously measuring these parameters (pcvO2, pcvCO2) in the sagittal sinus in 7 pigs under general anaesthesia during a 100% oxygen enhancement. The relation between oxygen increase in brain tissue and in the sagittal sinus showed a coefficient of correlation (CCmean) r(mean) = 0.96. The quantitative response in brain tissue was much more sensitive than in the sinus. A close correlation between pCO2 in brain tissue and sagittal sinus and the increase of the inspired oxygen was seen: CC ptiCO2 to arterial oxygen pressure (paO2) - r(mean) = 0.67, CC pcvCO2 to paO2 - r(mean) = 0.88. This is important for interpreting measured values and introducing new coefficients for patient monitoring. Newly available continuous brain oxygen measurement methods will allow better understanding of brain metabolism in the future.

Algorithms↗
PubMed1997

[Artificial humidification of inspired gas--status of knowledge and technique].

Artificial humidification of inspired air serves to maintain or restore physiological heat and moisture conditions in the bronchial system in intubated or tracheotomized patients. The need to condition the respiratory gases in these patients is undisputed. The present paper reviews the pathophysiology and methods of the artificial active and passive humidifying of inspired gases. The various advantages and disadvantages of the individual methods and techniques of humidifying inspired gases are compared and discussed. Present-day medical knowledge indicates that passive artificial humidifying of respiratory gases (heat and moisture exchanger, HME) is adequate to meet most requirements for warming and moistening the inspiratory air in patients whose upper airways are devoid of natural conditioning of respiratory gases in consequence of intubation and tracheotomy. This applies to artificial ventilation in prehospital situations, artificial ventilation in anaesthesia and long-term artificial ventilation on the intensive care unit. With appropriate restrictions, the respiratory air of patients who breathe spontaneously via an artificial air vent (e.g. tracheal cannula) can also be conditioned by HME.

Equipment Design↗
PubMed1996

[The perioperative use of recombinant erythropoietin (rhEPO) in Jehovah's witnesses].

UNLABELLED: Erythropoietin, the hematopoietic growth factor, is synthesised in the kidneys and liver and regulates red blood cell production. Within the last few years, recombinant DNA technology has produced synthetic erythropoietin (rhEPO). Some patients, especially Jehovah's Witnesses, will not accept blood transfusion. The perioperative administration of rhEPO increases the patients' hematocrit (HCt) to a higher than physiological level. METHODS AND RESULTS: We report a case of a 66-year-old female Jehovah's Witness who refused blood transfusions and responded favourably to rhEPO treatment. A total hip arthroplasty was planned. A pretreatment hemoglobin level (Hb) of 13.7 g/dl and HCt of 43% were documented. After preoperative subcutaneous application of 5000 I.E. rhEPO three times per week and daily oral substitution of 300 mg ferrous sulfate over a period of 3 weeks, the Hb increased to 15.5 g/dl and the HCt to 49%. The operation was carried out after the ninth application of rhEPO. Postoperatively, the Hb concentration was 11.8 g/dl and the HCt 35%. Therefore, postoperative administration of rhEPO was not considered indicated. No side effects of rhEPO application were noted. The patient left hospital on the 10th postoperative day. CONCLUSIONS: The case report describes perioperative management using human rhEPO in Jehovah's Witnesses. Treatment with rhEPO increases preoperative Hb levels to a point making it possible to compensate for operative blood loss. RhEPO combined with daily iron substitution may be useful in patients who refuse transfusion based on religious convictions.

Aged↗
PubMed1995

Relative risks of age, gender, nationality, smoking, and Helicobacter-pylori-infection in duodenal and gastric ulcer and interactions.

A logistic regression model was applied to assess risk factors and diagnostic predictors in duodenal and gastric ulcer, as well as in unspecific changes of gastric mucosa. In the latter group smoking, epigastric distress, and pain were associated with elevated relative risks. In the gastric ulcer model, increased odds were found for age, German nationality, smoking, and low and high urease activity of antral mucosa. This holds for duodenal ulcer, too; however interactions between complaints, urease activity, and nationality must be considered. In each case odds depend from the composition of the control group. Therapeutic implications have been considered.

Adult↗
PubMed1992

Use of moclobemide in children with attention deficit hyperactivity disorder.

A monoamine oxidase hypothesis for the cause of attention deficit hyperactivity disorder has recently been established (Shekim et al. 1986). To test this, moclobemide, a new and reversible inhibitor of monoamine oxidase-A, was administered to 12 children between the ages of 6 and 13 years, diagnosed as attention deficit hyperactive according to DSM III-R, in a 4-week study. All had previously discontinued treatment with methylphenidate due to side-effects. A 40% improvement in parental assessment of children's behaviour occurred among those who received moclobemide as outpatients, and a 31% improvement among the five in-patients. There was a general increase in concentration and attention span at the end of the trial, but mood changes and explosive behaviour continued to be present at a low level. Brain mapping after moclobemide treatment showed an overall reduction in frontal lobe delta activity. Moclobemide was well tolerated by these patients, although two complained of mild gastrointestinal disturbances during the first week of therapy.

Adolescent↗
PubMed1991

[Effectiveness and tolerance of the selective MAO-A inhibitor moclobemide in children with hyperkinetic syndrome].

The pharmacotherapy of the hyperkinetic syndrome with amphetamines was inaugurated by Bradley in 1937. As a rule, methylphenidate is prescribed today, although some side effects limit its use. Tests carried out by Zametkin in 1985 showed that clorgyline and tranylcypromine are effective in hyperkinetic children, but not deprenyl. In an open clinical study we administered moclobemide, a new reversible MAO-A inhibitor, to children who fulfilled the diagnostic criteria for hyperkinetic syndrome according to ICD-9 (314). An extensive examination was made to evaluate the efficacy and safety of the substance in this disorder. In addition to subjective ratings on the behavioral level a number of objective neuropsychological tests were used. Moclobemide proved to be effective in the treatment of the hyperkinetic syndrome, and side effects were surprisingly rare. EEGs performed during treatment showed a considerable decrease in delta waves in the frontal lobe region.

Attention↗
PubMed1991

[Encopresis in children. Preliminary report of new therapeutic and diagnostic aspects].

There appears to be no strict boundary between encopresis, which is defined as a psychogenic disorder, and incontinence, in which there is an inability to retain faeces voluntarily. Our findings over an 8-year period suggest that unrecognized functional or organic retention disorders are present in encopresis more often than previously thought. Of 16 children with encopresis who were examined by perfusion manometry 14 were found to have disorders of anorectal functions. Of these, 7 showed pathologically low sphincteral pressure rates and 3 abnormally high rates with coordination disorders. Four had normal sphincteral pressure rates but considerably disturbed sensitivity. In the 3 children examined by MRI so far clear morphological changes were found. The question of whether the deviations found were the result of primary or secondary changes could not be clarified. However, of key importance is that these additional findings enable the use of a combined course of treatment (passive sphincter training by electrostimulation and active sphincter training with biofeedback) that seemed to bring improvement quickly and reliably.

Adolescent↗