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Biomedical subjects

W Russ

Publications and source records attributed to W Russ.

At least 37 records · Page 2Linked to original sources
PubMed1988

[Somatosensory evoked potentials in obliterating interventions of the carotid bifurcation].

A prospective study was undertaken to determine the prognostic value of somatosensory evoked potentials during carotid artery surgery in patients where an intraluminal shunt was not used. During a three-year period 167 patients underwent 193 consecutive carotid endarterectomies under general anaesthesia. The somatosensory evoked potential after median nerve stimulation including calculation of central conduction time was used to assess cerebral function intraoperatively. Early postoperative neurologic morbidity was 3.6%, mortality 0.6%. Evoked potential changes in these patients were uniform and consisted of an increase in central conduction time of more than 20% from control (anaesthetic baseline), a decrease of the amplitude of the primary cortical response exceeding 50% and a loss of middle latency components. In subsequent recordings complete loss of the entire cortical evoked potential was observed in 5 of 7 patients. Sensitivity of CCT prolongation was 100%, specificity 89% (18 false positives). For amplitude reduction sensitivity was 86% (1 false negative), specificity 96% (7 false positives). For loss of the entire cortical response sensitivity was 71% (2 false negatives), specificity 99% (2 false positives). The above mentioned parameters correlated with postoperative neurologic state (Chi-square, p = 0.0001). Since the effects of potentially confounding variables (anaesthetics, temperature) are well known, the somatosensory evoked response, especially central conduction time, can be used as a reliable guide for brain supporting procedures.

Brain Ischemia↗
PubMed1988

[Reaction of the sympathetic nervous system, cardiovascular parameters and endocrine stress response in disobliterating interventions of the carotid arteries. A comparison of isoflurane anesthesia and modified neurolepto-anesthesia].

In order to investigate whether the increases in mean arterial pressure (MAP) and HR during carotid endarterectomy are due to a systemic, sympathicotonic stress response and to compare two anesthetic regimens for this operation, 20 patients were randomly allocated to the following groups: (1) modified neuroleptanesthesia with midazolam, fentanyl, and vecuronium: and (2) isoflurane anesthesia with vecuronium relaxation. Premedication (pethidine, promethazine) and induction of anesthesia were similar in both groups. The plasma levels of epinephrine and norepinephrine (by HPLC/ECD), ADH, ACTH, and cortisol (by RIA), glucose, lactate, and free glycerol were determined before and after induction of anesthesia, 7 times during the operation, and 30 min after extubation. MAP and HR were measured continuously. Statistical evaluation was undertaken by analysis of variance with repeated measures on 1 factor, considering P values of less than 0.05 as significant. The endocrine parameters failed to show any remarkable increase during the entire operation period. After the end of the operation all hormones rose significantly (P less than 0.001). No correlation was found between plasma catecholamines and increases in MAP and HR. Group levels of norepinephrine and ADH were higher in the isoflurane group (P less than 0.04). It is concluded that cardiovascular reactions during carotid endarterectomy are not caused by systemic stress. Neuroleptanesthesia leads to better stress protection in the postoperative period, while isoflurane anesthesia has some advantages for the intraoperative control of arterial pressure.

Adult↗
PubMed1987

Effects of hypothermia on somatosensory evoked responses in man.

Somatosensory evoked responses after median nerve stimulation were recorded in 21 patients during hypothermic cardiopulmonary bypass. During hypothermia a significant linear correlation (P less than 0.001) was found between evoked potential latency and temperature. Correlation was best for tympanic membrane temperature during cooling and for perfusate temperature (arterial, venous) during rewarming. The increase in latency was more pronounced for middle latency components (N2, N3) and for the early cortical N1 than for the cervical N0 and central conduction time. In all patients N1 was detectable at 26 degrees C, with slightly reduced amplitude. In the rewarming period the changes occurred in the reverse order and pre-bypass values were achieved at normothermia. The slopes of the regression lines were different during cooling and rewarming, when latencies were related to patient (tympanic, nasopharyngeal, rectal) temperature, but identical when arterial or venous blood temperature was used as the reference. No correlation was found between latency and perfusion pressure. We conclude that sophisticated temperature measurement is required to aid the interpretation of evoked responses used during hypothermia.

Aged↗
PubMed1987

Spectral analysis of the EEG during hypothermic cardiopulmonary bypass.

In 39 patients undergoing aorto-coronary-bypass grafting, spectral analysis of the EEG (compressed spectral array: CSA) and calculation of spectral edge frequency (SEF) were performed. The effects of different temperatures and of perfusion pressure (PP) were analyzed. Predictable patterns were observed. During cooling on cardiopulmonary bypass (CPB), linear regression analysis revealed a close correlation between SEF and tympanic membrane (Tty) or nasopharyngeal temperature (Tnp). During rewarming, a nonlinear correlation between SEF and Tty or Tnp was found. Rectal temperature as well as blood temperature in the arterial or venous line of the oxygenator seemed to be less useful. The independence of SEF and PP was demonstrated during the whole procedure. At the onset of CPB, after correction of the aortic clamp for performance of the aortic anastomosis and after removal of the aortic clamp, bilateral EEG slowing of varying duration occurred in 20 patients. Comparison of mean SEF before and after CPB revealed a difference of about 5 Hz. In no patient were major neurological abnormalities observed postoperatively.

Body Temperature↗
PubMed1987

[Effect of isoflurane and enflurane on somatosensory evoked potentials following stimulation of the median nerve].

The effects of enflurane and isoflurane on somatosensory evoked potentials (SEP) after median nerve stimulation were studied in 25 healthy adult patients. Cervical and cortical SEP were recorded simultaneously. pCO2 and tympanic membrane temperature were kept constant. Following induction of anaesthesia with thiopentone, fentanyl and succinylcholine SEP were recorded during normoventilation with 100% oxygen and after inhalation of 66.6% nitrous oxide. Isoflurane at inspired concentrations of 0.8, 1.65, 2.5, 3.3% was given to 10 patients at 15 minutes intervals and was reduced after nitrous oxide had been replaced by oxygen. 15 patients received equipotent doses of enflurane (1.1, 2.2, 3.25, 4.3%.) SEP were recorded at the end of each interval. Isoflurane and enflurane caused dose dependent increases in latency of the cortical SEP. This effect was more pronounced with enflurane. Isoflurane reduced amplitude of the primary cortical response more than enflurane, when ventilation was performed with 66.6% nitrous oxide in oxygen. High doses of enflurane in oxygen augmented cortical SEP amplitudes associated with a marked increase in latency. Isoflurance and enflurance anaesthesia slightly altered cervical SEP. Middle latency components of the cortical SEP were progressively diminished with increasing isoflurane or enflurane concentrations. The effect of both agents in terms of delayed latencies and reduced amplitudes should be considered when recordings are performed intraoperatively.

Adolescent↗
PubMed1987

[Endocrine stress response in halothane, enflurane and isoflurane anesthesia in surgical interventions].

The endocrine stress response under inhalation anesthesia with halothane, enflurane, and isoflurane was investigated in 30 patients during and after orthopedic surgery (Table 2). Plasma levels of adrenaline and noradrenaline (by HPLC/ECD), ADH, ACTH, and cortisol (by RIA), glucose, lactate, and free glycerol were determined before induction of anesthesia, 10 min after intubation, 10 min before the end of the operation, and 5 and 30 min after extubation. Statistical evaluation was undertaken by analysis of variance with repeated measures on one factor. P values of less than 0.05 were considered significant. There were no significant differences in the concentrations of plasma catecholamines (Table 4, Figs. 1 and 2), ADH, ACTH (Table 5, Figs. 3 and 4), or cortisol before and during surgery between the groups. ADH was lower in the halothane group 5 and 30 min after extubation (P = 0.05), which might be due to the prolonged elimination of halothane after anesthesia. Blood pressure, heart rate (Table 3), and plasma concentrations of glucose, lactate, and free glycerol (Table 6) were comparable in all groups. It is concluded that for clinical practice halothane, enflurane, and isoflurane are comparable in their influence on the surgical stress response.

Adrenocorticotropic Hormone↗
PubMed1987

[Hemodynamic effects of the anti-arrhythmia agent flecainide (Tambocor) in coronary surgery patients].

Flecainide, a new antiarrhythmic drug (group 1 according to the classification after Vaughan Williams), is used in the treatment of atrial and ventricular arrhythmias. Cardiac patients are compromised by arrhythmia during operative procedure. The haemodynamic effects of 1 mg/kg b.w. flecainide compared to a placebo solution were studied randomised in 20 patients undergoing coronary artery surgery (before cannulation of the large vessels). Mean arterial pressure, PAP, PCP, PRA and TPR remained unchanged, whereas heart rate (-12%), cardiac index (-17%) and dp/dtmax (-35%) decreased significantly. Total systemic resistance increased by 14%. The results show that it is possible to use flecainide during coronary artery surgery. In patients with reduced myocardial function it should be injected carefully and a decreased dose is recommended with regard to deterioration of left ventricular contractility.

Arrhythmias, Cardiac↗
PubMed1987

Low-dose fentanyl analgesia modified by calcium channel blockers in cardiac surgery.

The hypothesis that calcium channel blockers can potentiate and prolong the anti-nociceptive effects of opioids was tested. Forty-five men scheduled for aorto-coronary bypass operation received fentanyl according to their individual demands (haemodynamics, clinical parameters). The patients were allocated at random into three groups receiving either nimodipine 1.0 microgram kg-1 min-1 (Group 1, n = 15), nifedipine 0.70 microgram kg-1 min-1 (Group 2, n = 15), or no calcium channel blocker (Group 3, n = 15). Cerebral activity was monitored using a computerized spectral analysing system before and during the operation. The total amount of fentanyl required was significantly lower in the nimodipine group than the control group (-71%, P less than 0.001), whereas the nifedipine group did not differ from the control group. Quality of intra-operative anaesthesia was comparable in the three groups with respect to clinical observations (amnesia, sweat, tears, pupils), and the post-operative course was similar in all patients as well. Cerebral activity during the nimodipine-supplemented opioid anaesthesia was higher in the faster frequency bands (13-30 Hz). Power level in the beta range was most pronounced in Group 1, whereas power in the alpha range was similar in the calcium channel-blocker groups. The major conclusion was that nimodipine but not nifedipine administration can reduce fentanyl requirements during surgical procedures without influencing the quality of anaesthesia.

Analgesia↗
PubMed1987

[Nitrous oxide: modification of the hemodynamics in patients with coronary heart disease].

The haemodynamic effects of 70%, 50% and 30% N2O--compared to 100% O2--were studied in 20 patients undergoing coronary artery bypass grafting. The measurements-performed after an equilibration phase of 10 minutes--were made preoperatively but after induction of anaesthesia with 0.3 mg/kg bw etomidate, 0.01 mg/kg bw fentanyl and 0.1 mg/kg bw pancuronium bromide. In relation to N2O concentrations, mean arterial pressure (-4.8%), total systemic resistance (-7.9%) and stroke volume index (-6.4%) decreased moderately, whereas the cardiac index remained unchanged and the heart rate increased (+9.7). Total pulmonary vascular resistance was always within the physiological range, as were the triple index and the rate pressure product. In patients with coronary heart disease cardiovascular functions are compromised in close relation to the degree of the underlying disease. In accordance with other investigators, nitrous oxide should not be used in patients with impaired left ventricular function because of the possibility of deterioration of myocardial function. In such cases, amnesia should be achieved by means of other agents.

Anesthesia↗
PubMed1987

[Effect of premedication and fentanyl administration on the endocrine stress reaction during halothane anesthesia].

The influence of two different premedication regimens (diazepam versus pethidine/promethazine with fentanyl substitution before induction) on the endocrine stress-response during halothane anaesthesia was investigated in twenty orthopedic surgery patients. After premedication, the levels of plasma catecholamines, ADH, ACTH and cortisol were lower in the pethidine/promethazine-than in the diazepam-group. The levels of adrenaline remained significantly lower during the whole observation period. Thirty minutes after extubation all endocrine parameters except noradrenaline were lower in the pethidine/promethazine-group than in the diazepam-group.

Adolescent↗
PubMed1986

[Somatosensory evoked potentials under thiopental and etomidate].

The somatosensory evoked potential in response to median nerve stimulation was recorded in 42 patients during infusion of either 15 mg/kgbw thiopentone (TH) or 1 mg/kgbw etomidate (E) within 15 min and before and after injection of 0.3 mg/kgbw etomidate bolus. Cortical and cervical responses were analysed simultaneously and central conduction time (CCT) was calculated. Marked alterations of waveforms and an increase in latency of the primary cortical SEP and of CCT were observed in all patients. Infusion of TH or E was followed by a diminution of middle and long latency components. Amplitude of the cortical N20 was found to be unchanged during and after TH and to be increased after infusion or injection of E, indicating the synchronizing properties of this drug. The cervical SEP (N14) remained entirely unchanged in response to both agents. During hypnotic drug administration a pronounced increase in latencies and CCT as well as a decrease in the number of identifiable peaks has to be considered when SEP monitoring is performed intraoperatively or in intensive care treatment.

Anesthesia↗
PubMed1985

Intraoperative somatosensory evoked potentials as a prognostic factor of neurologic state after carotid endarterectomy.

Somatosensory evoked cervical and cortical potentials (SEP) were analyzed under general anesthesia in 106 patients undergoing carotid endarterectomy. Cortical electrical silence occurred in 5 patients without an inlying shunt; all developed a new neurologic deficit postoperatively. Analysis of the SEP in these patients revealed progredient cerebral ischemia as indicated by an increase in central conduction time (CCT) and a decrease in amplitude of the primary cortical response N20P25 resulting in a complete loss of cortical SEP later on during the clamping period. In 6 patients the insertion of a shunt restored the deteriorated SEP, these patients and those with unchanged SEP after carotid clamping showed an uneventful postoperative recovery. Taking the presence or absence of N20P25 as the sole parameter, the sensitivity of this technique was 83%, specificity 99% and predictability 83%. A normal range for CCT and amplitude of N20P25 during anesthesia and criteria for shunt insertion were developed. The presented monitoring regimen appears to be rational and is based on current concepts of cerebrovascular physiology and pathophysiology.

Adult↗
PubMed1985

[Experiences with a new EEG spectral analyzer in carotid surgery].

Spectral analysis with the compressed spectral array display (CSA) and calculation of spectral edge frequency (SEF) was performed in 43 cases undergoing endarterectomy of the carotid bifurcation. New neurologic deficit appeared in 2 patients (= 4.6%). One of them died postoperatively (= 2.3%), the other suffered from permanent paralysis of the hand. Another 9 patients showed loss of high frequency activity (= decrease in SEF) without a new deficit in the postoperative period. A significant EEG event was defined as a decrease in SEF after carotid cross clamping for at least 5 min. Fisher's exact probability test revealed a close correlation between these EEG events and neurologic outcome. The sensitivity of the test, which was calculated on true positive and false negative events, was 100%, the specificity, based on true negative and false positive events, was 76%. The predictability of the test, based on all EEG events, was 18%; respectively 40% when calculated on significant events.

Anesthesia↗
PubMed1985

[Effects of nitrous oxide and halothane on somatosensory evoked potentials after stimulation of the median nerve].

In 10 healthy adult subjects cervical and cortical somatosensory evoked responses (SEP) after median nerve stimulation were recorded. The recordings were performed before and after inhalation of 66 2/3% nitrous oxide (and 33 1/3% oxygen) and during additional inhalation of halothane in concentrations ranging from 0,5 to 2,0 vol%; end tidal paCO2 and tympanic membrane temperature were kept constant. Nitrous oxide caused a 50% amplitude reduction of the cortical responses while latencies remained unchanged. Latency of the primary cortical response N20 and central conduction time increased continuously with increasing halothane concentration, amplitude N20P25 and amplitude ratio R showed a further decrease. The sensitivity of SEP components to halothane anaesthesia increased with peak latency: Cervical SEP remained relatively constant even during deep anaesthesia, early cortical potentials showed latency prolongation and amplitude reduction, middle and long latency components were progressively diminished with increasing halothane concentration. These changes have to be considered, when interpreting cervical and cortical SEP recorded intraoperatively.

Adolescent↗
PubMed1985

[Experiences with "etomidate pro infusione" in heart surgery interventions with extracorporeal circulation].

The results of experimental studies with etomidate demonstrating positive hemodynamic effects as well as a decrease in intracranial pressure induced a study using etomidate during cardiac surgery. This randomized study including 506 patients should prove the influence of etomidate on the rate of psychic disturbances after cardiac surgery. Patients treated with etomidate received a loading dose of 1 mg/kg b.w. etomidate within 15 minutes followed by a continuous infusion of 1 mg/kg b.w./h until the end of ECC. Patients without etomidate were the control group. Psychic disturbances were observed in 25% of the control group and in 30% of the etomidate group. In both groups of patients there was a fair number of patients with perioperative cardiopulmonary problems (artificial ventilation longer than 24 hours; catecholamine therapy: epinephrine greater than 5 micrograms/min longer than 3 hours): 8% in the control group and 20% in the etomidate group. These results indicate that etomidate does not beneficially influence the rate of psychic disturbances after open-heart surgery; it may induce, however, cardiopulmonary side effects after cardiac surgery. The results of recent studies indicating drug induced adrenal insufficiency are discussed.

Adolescent↗
PubMed1984

Intraoperative detection of cerebral ischemia with somatosensory cortical evoked potentials during carotid endarterectomy--presentation of a new method.

Somatosensory evoked potentials (SEP) are an objective measure of cerebral function. They depend on the integrity of cortical blood flow. After stimulation of the median nerve, SEP of subcortical and cortical origin can be recorded within a short time during carotid surgery by means of 3 scalp electrodes. Intraoperative SEP recordings are more resistant to anesthetic influence than is the EEG. In a 69-year-old woman, monitoring with SEP gave an early warning of cerebral ischemia during carotid endarterectomy. The cortical SEP disappeared immediately after carotid cross-clamping. The entire loss of the cortical SEP was associated with a new neurologic deficit postoperatively. This technique is simple and convenient to use and appears to be predictive of neurologic outcome.

Aged↗
PubMed1984

[Visual evoked potentials (VEP) in anesthesia and intensive care].

Methodological considerations and different stimulation techniques of visual evoked potentials (VEP) are described. VEP can provide information about neurological function during anaesthesia, surgery and in the unconscious patient after head injury. The feasibility of the method for intraoperative monitoring in neuro- and cardiac surgery and the influence of general anaesthetics and other contributing factors such as temperature, paCO2, pO2, part are discussed.

Anesthesia↗