[Alcohol and myocarditis]

The direct toxic effect of alcohol and its metabolite acetaldehyde has been demonstrated both in laboratory animals and in humans. Alterations in the mitochondrial ultrastructure and the dilatation of the sarcoplasmatic reticulum have been shown after an acute infusion of alcohol in the heart. These changes correlate with decreased mitochondrial function, defects in protein synthesis and the occurrence of arrhythmias. The risk of developing alcoholic cardiomyopathy is related to both the mean daily alcohol intake and the duration of drinking, but there is much individual susceptibility to the toxic effect of alcohol. Most patients, in whom alcoholic cardiomyopathy develops, have been drinking over 80 g/d for more than 5 years. The clinical diagnosis of alcoholic cardiomyopathy reflects the coexistence of global myocardial dysfunction in a heavy drinker in whom no other cause for myocardial disease was found. In studies focussing on alcoholic cardiomyopathy the surprising histologic findings in endomyocardial biopsy in about 30% of all cases was myocarditis with a lymphocytic infiltrate in association with myocyte degeneration or focal necrosis. In myocarditis, the network of microtubules and intermediate filaments is also disrupted by the inflammatory reaction which involves resident cells (myocytes, fibroblasts, endothel cells) and systemic cells (granulocytes, macrophages, monocytes, lymphocytes). Changes in the cardiac cytoskeleton and the extracellular matrix may affect contractile function, since the cytoskeleton organizes the intra- and intercellular architecture. After all, in patients with alcohol abuse and myocarditis the immune functioning appears to be compromised. Several studies suggest that heavy drinking alters both lymphocyte and granulocyte production and function. Alcohol consumption per se might harm the immune system. Furthermore, the myocardial damage due to alcohol consumption could initiate autoreactive mechanisms comparable to those in viral or idiopathic myocarditis. Patients with alcohol abuse and myocarditis have a poor prognosis: signs of biventricular failure including tachycardia, hepatomegaly, and peripheral and lung edema are observed. These symptoms are as nonspecific as are various echocardiographic and electrocardiographic changes such as atrial and ventricular arrhythmias which may be associated both with myocarditis, alcoholic cardiomyopathy and acute effects of drinking without hemodynamic alterations. For the management of patients with alcohol abuse the prevention of further alcohol intake is mandatory to reverse the myocardial damage and the unfavorable predisposition for infection. Specific treatment of myocarditis is the second important option, and treatment of heart failure by reducing the size of the dilated heart and alleviating the signs and symptoms of heart failure is a logical third step.

Antiproliferative effects of interferon alpha on human pancreatic carcinoma cell lines are associated with differential regulation of protein kinase C isoenzymes

BACKGROUND

The molecular mechanisms mediating the antiproliferative effects of interferon alpha on human pancreatic carcinoma cells are poorly understood.

AIM

To characterise the effects of interferon alpha on protein kinase C isoenzyme expression in interferon alpha sensitive and resistant human pancreatic tumour cell lines.

METHODS

The ductal human pancreatic carcinoma cell lines Capan 1 and Capan 2 were investigated. Anchorage dependent and independent growth was determined by cell number and a human tumour clonogenic assay. Interferon alpha receptor expression was examined by reverse-transcriptase polymerase chain reaction and electrophoretic mobility shift assay. Protein kinase C isoenzyme expression was evaluated by western blotting using monospecific polyclonal antibodies.

RESULTS

Interferon alpha treatment results in a time and dose dependent inhibition of anchorage dependent and independent growth in Capan 1 cells while Capan 2 cells were not affected by interferon alpha. Both cell lines express interferon alpha receptor mRNA transcripts. Growth inhibition by interferon alpha in Capan 1 cells was paralleled by a profound decrease of protein kinase C alpha and zeta expression while these isoenzymes were unaffected in the interferon resistant cell line Capan 2.

CONCLUSION

Inhibition of protein kinase C isoenzyme expression might determine the sensitivity of a given pancreatic carcinoma to respond to the antiproliferative action of interferon alpha.

Edema and intrapancreatic trypsinogen activation precede glutathione depletion during caerulein pancreatitis

Acute pancreatitis is characterized by hyperamylasemia, pancreatic edema, and the presence of activated digestive enzymes within the pancreas. The secretagogue-induced model of acute pancreatitis is also characterized by pancreatic acinar cell vacuolation, subcellular redistribution of lysosomal hydrolases, and a fall in pancreatic glutathione levels. We have performed time-dependence studies to determine the sequence with which these phenomena appear and to establish their cause-and-effect relationship. Evidence of lysosomal enzyme redistribution and trypsinogen activation within the pancreas could be detected within 10-15 min of the onset of supramaximal secretagogue stimulation, while hyperamylasemia (30 min), pancreatic edema (60 min), and acinar cell vacuolation (60 min) occurred at later times. Pancreatic glutathione levels were either unchanged (15 and 30 min) or elevated (60 min) during the early times of supramaximal stimulation and were only noted to be decreased at a later time. These results support the conclusion that intrapancreatic digestive enzyme activation, possibly occurring by a mechanism involving lysosomal hydrolase redistribution, is an early and likely a critical event in the evolution of secretagogue-induced pancreatitis but that glutathione depletion is neither early nor critical to the evolution of this model of pancreatitis.

Edema and intrapancreatic trypsinogen activation precede glutathione depletion during caerulein pancreatitis

Acute pancreatitis is characterized by hyperamylasemia, pancreatic edema, and the presence of activated digestive enzymes within the pancreas. The secretagogue-induced model of acute pancreatitis is also characterized by pancreatic acinar cell vacuolation, subcellular redistribution of lysosomal hydrolases, and a fall in pancreatic glutathione levels. We have performed time-dependence studies to determine the sequence with which these phenomena appear and to establish their cause-and-effect relationship. Evidence of lysosomal enzyme redistribution and trypsinogen activation within the pancreas could be detected within 10-15 min of the onset of supramaximal secretagogue stimulation, while hyperamylasemia (30 min), pancreatic edema (60 min), and acinar cell vacuolation (60 min) occurred at later times. Pancreatic glutathione levels were either unchanged (15 and 30 min) or elevated (60 min) during the early times of supramaximal stimulation and were only noted to be decreased at a later time. These results support the conclusion that intrapancreatic digestive enzyme activation, possibly occurring by a mechanism involving lysosomal hydrolase redistribution, is an early and likely a critical event in the evolution of secretagogue-induced pancreatitis but that glutathione depletion is neither early nor critical to the evolution of this model of pancreatitis.

Glucocorticoid receptor concentration modulates glucocorticoid-regulated gene expression in rat pancreatic AR42J cells

In this study we investigated the effects of altered intracellular glucocorticoid receptor (GR) concentrations on glucocorticoid-regulated gene expression in the rat pancreatic acinar cell line AR42J. Incubation of AR42J cells with dexamethasone results in a time-dependent transcriptional stimulation of amylase gene expression (about 5-fold) and a transcriptional inhibition of bombesin receptor (BR) gene expression. Decreasing the intracellular GR concentration to 50% by preincubation with RU 38486 results in a significant attenuation of dexamethasone-regulated amylase and BR gene expression. In contrast, increasing the intracellular GR concentration 2-fold by preincubation with the phosphodiesterase inhibitor IBMX significantly enhances the glucocorticoid inhibition of BR gene expression whereas amylase mRNA concentrations remain unaltered. These data demonstrate that intracellular GR concentrations determine the sensitivity of glucocorticoid-regulated gene expression in rat pancreatic AR42J cells.

Retinoids: effects on growth, differentiation, and nuclear receptor expression in human pancreatic carcinoma cell lines

BACKGROUND & AIMS

Advanced pancreatic carcinoma has a dismal prognosis despite extensive chemotherapeutic trials. The aim of this study was to evaluate the role of retinoids as an experimental therapeutic approach for pancreatic cancer.

METHODS

Four ductal and one acinar pancreatic tumor cell lines were investigated. Growth was determined by cell number and a human tumor clonogenic assay. In vivo growth was assessed by xenografts transplanted into nude mice. Differentiation was characterized by immunofluorescence microscopy and carbonic anhydrase II gene expression. Retinoid receptors were characterized by Northern blotting and reverse-transcriptase polymerase chain reaction.

RESULTS

Retinoid treatment results in a time- and dose-dependent growth inhibition in vitro and in vivo of ductal but not acinar pancreatic tumor cells. Retinoid treatment induces a more differentiated phenotype in ductal tumor cells as shown by morphological criteria and increased expression of carbonic anhydrase II. All pancreatic tumor cell lines expressed a broad panel of cellular retinoid binding proteins and nuclear retinoid receptors. Retinoic acid receptor gamma and cellular retinoic acid binding protein II were found in all retinoid-sensitive ductal tumor cell lines but not in the retinoid-resistant acinar cell lines.

CONCLUSIONS

Detailed knowledge of nuclear retinoid receptor expression may provide rational strategies for retinoid treatment of pancreatic cancer.

The potential for malaria control with the biological larvicide Bacillus thuringiensis israelensis (Bti) in Peru and Ecuador

A study on the efficacy of Bti spraying in mosquito breeding places was undertaken in the Pacific coast of Peru and Ecuador and in the Amazon area of Peru. It was shown that Bti is a powerful larvicide for Anopheles larvae, although it sinks quickly, whereas Anopheles larvae feed at the water surface. The duration of its effect was less than 7 days with the exception of the Amazon area of Peru, where it was approximately 10 days. In two study areas, Bti was sprayed weekly over periods of 10 and 7 weeks, respectively, and the adult mosquito densities were monitored. The Anopheles adult density (bites per person per hour on human baits) was reduced by an average of 70% in one area and by up to 50% in the other. This means that Bti spraying can potentially be an important component of a modified malaria control strategy.

Biochemical and morphological changes that characterise recovery from necrotising biliary pancreatitis in the opossum

The events that characterise recovery from severe biliary pancreatitis have not been defined. This study used a reversible model of necrotising pancreatitis, induced by obstructing the opossum common bile pancreatic duct (CBPD), to evaluate this phenomenon. The CBPD of opossums was obstructed with a balloon tipped catheter for five days and then decompressed by removal of the catheter. Recovery was evaluated 0-90 days after relief of obstruction. Serum bilirubin and amylase values rapidly declined, reaching control values 7-14 days after removal of the obstructing catheter. Pancreatic protein and amylase values were transiently increased shortly after relief of obstruction but returned to control values 21 days after decompression. Pancreatic ornithine decarboxylase activity and incorporation of [3H]-thymidine into DNA were transiently increased 14 days after duct decompression suggesting that regeneration occurs at approximately that time. Foci of pancreatic necrosis involved roughly 40% of the gland at time of decompression but these foci gradually disappeared and the gland resembled that of control animals 60 days after decompression. Evidence of fibrosis or collagen deposition in the pancreas was not noted at any time. These studies show that recovery after necrotising biliary pancreatitis occurs comparatively rapidly and the restitution ad integrum occurs. Recovery from necrotising acute pancreatitis in this model is not associated with the development of chronic pancreatitis.

Biochemical and morphological changes that characterise recovery from necrotising biliary pancreatitis in the opossum

The events that characterise recovery from severe biliary pancreatitis have not been defined. This study used a reversible model of necrotising pancreatitis, induced by obstructing the opossum common bile pancreatic duct (CBPD), to evaluate this phenomenon. The CBPD of opossums was obstructed with a balloon tipped catheter for five days and then decompressed by removal of the catheter. Recovery was evaluated 0-90 days after relief of obstruction. Serum bilirubin and amylase values rapidly declined, reaching control values 7-14 days after removal of the obstructing catheter. Pancreatic protein and amylase values were transiently increased shortly after relief of obstruction but returned to control values 21 days after decompression. Pancreatic ornithine decarboxylase activity and incorporation of [3H]-thymidine into DNA were transiently increased 14 days after duct decompression suggesting that regeneration occurs at approximately that time. Foci of pancreatic necrosis involved roughly 40% of the gland at time of decompression but these foci gradually disappeared and the gland resembled that of control animals 60 days after decompression. Evidence of fibrosis or collagen deposition in the pancreas was not noted at any time. These studies show that recovery after necrotising biliary pancreatitis occurs comparatively rapidly and the restitution ad integrum occurs. Recovery from necrotising acute pancreatitis in this model is not associated with the development of chronic pancreatitis.

Physiology of single putative cochlear efferents in the chicken

1. An experimental approach was developed that allowed recording of neurophysiological activity from single putative cochlear efferents in the auditory brain stem of anesthetized chickens with the use of glass micropipettes. The aim of this study was to study spontaneous and tone-evoked activity from single efferent neurons in the chick and to compare their properties with those of other vertebrate hair cell organs. Because the birds, like mammals, have a complex hearing organ with different hair cell types and different afferent and efferent innervation, the purpose of this study was also to determine whether different types of efferents exist. 2. In the same electrode penetrations, putative trapezoid fibers were also isolated. In addition, the penetration angle permitted recordings from units in both cochlear nuclei, nucleus magnocellularis and nucleus angularis (probably mostly cochlear afferents), in the same animal. This allowed monitoring of the auditory sensitivity of the individual animal during the experiment. With the use of physiological criteria, it was possible to distinguish between trapezoid fibers and putative cochlear efferents. Possible alternative origins of the responses described are discussed. 3. Tuning curve characteristics of putative efferents were determined. They were as sensitive as ascending auditory neurons. Q10 dB values of efferent tuning curves were < 2.5 and thus showed poorer frequency selectivity than ascending fibers; in some cases they covered the entire hearing range of the chicken. 4. Latencies to tone pips were different for ascending neurons and putative efferent units. For trapezoid fibers and neurons from the cochlear nuclei, latencies usually did not exceed 5 ms, whereas latencies of efferents were always longer. 5. Because of the interaural canal that connects both middle ear cavities in birds, the measurement of the lateralization of the efferents was difficult. In any case, the majority of putative cochlear efferents responded more sensitively to sound stimulation of the contralateral side. 6. Of the efferent units, 28% showed no spontaneous activity. The others either showed regular spontaneous activity, or their time-interval histograms showed longer modes than ascending fibers. In general, mean spontaneous activity was lower than in ascending fibers, being < 30 spikes/s. 7. In contrast to reports from mammalian studies, in which efferents only showed on peristimulus time (PST) response pattern to tonal stimuli (chopper), two different response types were found in this study: two excitation types (chopper and primary-like) and one suppression type.(ABSTRACT TRUNCATED AT 400 WORDS)

[Preventive digitalis therapy in open thoracotomy]

Prophylactic digitalization is still recommended after open lung surgery in order to prevent cardiac arrhythmias in the postoperative period. Since a beneficial effect of this potentially harmful medication is only poorly documented, we conducted a prospective randomized trial. Patients undergoing elective open lung surgery were divided into two groups one of which received digoxin postoperatively, the other not. Randomization was performed independently in three groups with regard to the extent of surgery, i.e. pneumonectomies in patients of any age, (bi-)lobectomies in patients > 50 and other (less extended) operations in patients > 60. Patients who were either too young for either group or who had already taken digoxin before surgery were followed separately. Monitoring was performed continuously in the ICU and conventional ECG was registered after 24, 48 and 72 hours and weekly until dismission.--Cardiac arrhythmias are very frequent in the early postoperative period with a maximum between the third and the fifth postoperative day. Any kind of arrhythmias were present in 19 of 30 patients (63%) compared to 14 of 35 patients (40%) in the control group. Symptomatic arrhythmias that needed treatment occurred in 11.4% of the control group, but in 33.3% of the patients with prophylactic digitalization. We therefore conclude that a general prophylactic digitalization after open lung surgery is not indicated, but that arrhythmias should be treated individually.

Functional imaging of the kidney by means of measurement of the apparent diffusion coefficient

PURPOSE

To determine the relationship between the apparent diffusion coefficient (ADC) and renal function.

MATERIALS AND METHODS

Twenty-three volunteers and seven pigs underwent diffusion-sensitive magnetic resonance (MR) imaging of the kidneys with a stimulated-echo acquisition mode excitation and echo-planar imaging readout under various physiologic conditions. The effect of hydration and anisotropic diffusion was studied in human subjects, and the effect of renal artery stenosis, ureteral obstruction, and diuresis was studied in the animal model.

RESULTS

The renal ADC values of dehydrated subjects were substantially increased with rehydration. Diffusion was highest in the medulla, with a pronounced radial component in the renal collecting system. In the pig model, induced renal artery stenosis resulted in immediate decrease in renal ADC; the degree of change was related to the flow deficit. The ADC also decreased with ureteral obstruction, but diuresis had no meaningful effect.

CONCLUSION

In vivo measurement of ADC has the potential for use as a noninvasive means to explore the functional status of the kidney.

Functional imaging of the kidney by means of measurement of the apparent diffusion coefficient

PURPOSE

To determine the relationship between the apparent diffusion coefficient (ADC) and renal function.

MATERIALS AND METHODS

Twenty-three volunteers and seven pigs underwent diffusion-sensitive magnetic resonance (MR) imaging of the kidneys with a stimulated-echo acquisition mode excitation and echo-planar imaging readout under various physiologic conditions. The effect of hydration and anisotropic diffusion was studied in human subjects, and the effect of renal artery stenosis, ureteral obstruction, and diuresis was studied in the animal model.

RESULTS

The renal ADC values of dehydrated subjects were substantially increased with rehydration. Diffusion was highest in the medulla, with a pronounced radial component in the renal collecting system. In the pig model, induced renal artery stenosis resulted in immediate decrease in renal ADC; the degree of change was related to the flow deficit. The ADC also decreased with ureteral obstruction, but diuresis had no meaningful effect.

CONCLUSION

In vivo measurement of ADC has the potential for use as a noninvasive means to explore the functional status of the kidney.

Transient stabilization of cholecystokinin A receptor mRNA by glucocorticoids in pancreatic AR42J cells

We have characterized the effects of glucocorticoids on gene expression of the cholecystokinin A receptor (CCK-R) using a cloned cDNA probe in the rat pancreatic acinar cell line AR42J. Dexamethasone (100 nM) resulted in a transient, time-dependent increase of CCK-R mRNA, with a maximal induction observed after 3 h of hormone treatment (238 +/- 29% of controls, n = 4). Further incubation with dexamethasone resulted in a subsequent decrease of CCK-R mRNA concentrations, which reached control values after 12 h of hormonal treatment. The increase of CCK-R mRNA was dose dependent with half-maximal effects observed at 10 nM and maximal effects observed at 100 nM of hormone. We next investigated the molecular mechanisms by which glucocorticoids induce CCK-R gene expression. Nuclear run-on analysis revealed that dexamethasone pretreatment had no significant effect on CCK-R gene transcription. Using actinomycin D, we determined the half-life for the mRNA of the CCK-R. Dexamethasone (100 nM) pretreatment for 3 h resulted in a significant increase of CCK-R mRNA stability, with a half-life of 240 min compared with 120 min in untreated control cells. These data therefore suggest that glucocorticoids transiently stimulate CCK-R mRNA concentrations by increasing the mRNA stability without affecting the receptor transcription rate.

Bombesin receptor gene expression in rat pancreatic acinar AR42J cells: transcriptional regulation by glucocorticoids

BACKGROUND/AIMS

This study investigated the correlation between glucocorticoid-regulated gene expression of the bombesin receptor (BR) and cellular sensitivity to bombesin stimulation in the rat pancreatic acinar cell line AR42J.

METHODS

BR gene expression was assessed using a cloned complementary DNA probe and radioligand binding assays. Intracellular Ca2+ mobilization was assessed by dual wavelength spectrophotometry using fura-2 in single cells.

RESULTS

Dexamethasone resulted in a rapid dose- and time-dependent decrease of BR messenger RNA levels with maximal inhibition to 25% +/- 2% of controls (n = 4) after 6 hours of hormone treatment. BR messenger RNA half-life was approximately 120 minutes and was not affected by dexamethasone pretreatment; nuclear run-on analysis showed a decreased transcription rate of the BR to approximately 25% of control after hormonal treatment. Radioligand binding studies showed a time-dependent decrease of specific bombesin binding to 25% +/- 8% of control after 48 hours of hormone treatment. Down-regulation of BR gene expression by dexamethasone resulted in a time- and dose-dependent decrease of intracellular Ca2+ mobilization after bombesin stimulation compared with untreated controls.

CONCLUSIONS

Glucocorticoids decrease BR gene transcription. The subsequent decrease in cellular BR number renders AR42J cells less sensitive for bombesin-stimulated intracellular Ca2+ mobilization.

[The value of defecography for diagnosis of rectocele and rectal prolapse]

The role of defecography with respect to rectoceles and to any grade of rectal prolapses has not been defined so far. Therefore, we studied 42 out of 45 patients that were submitted to a defecography between 1988 and 1992 for defecation disorders of unknown origin. In particular, we compared the diagnosis obtained by anamnestic data and the physical examination with the defecographic results and the definitive diagnosis with regard to the chosen therapies and the results. Rectocele and rectal prolapse were very frequent pathologies with 69% and 33% respectively. Of 23 patients with a clinically palpable rectocele, defecography was false negative in 4 and moreover, it did not provide any information about the functional relevance of the rectocele. Yet, it disproved the clinically diagnosed prolapses in 6 of 15 subjects, but revealed one in 5 of 27 patients that were presumed normal. On the other hand, a previously not diagnosed rectocele was detected in 6 out of 19 patients by means of defecography, but none of them proved to be of any clinical relevance. Of all rectoceles, only 48% were regarded responsible for the patients' symptoms and were therefore operated. Hereby, the indication for a surgical approach based more on anamnestic data and the proctological examination than on radiographic findings. Contrarily, the indication for a rectopexy--even if given only in 4 of those 14 patients with any grade of invagination--mainly based on the dynamics during defecation as documented by defecography.(ABSTRACT TRUNCATED AT 250 WORDS)

Glucocorticoid receptor gene expression in the exocrine and endocrine rat pancreas

Although pleiotropic effects of glucocorticoids on the endocrine and exocrine pancreas are well documented, it remains controversial whether these effects are due to direct interactions of glucocorticoid hormones with their receptors in the respective target cells. We therefore examined gene expression of the glucocorticoid receptor (GR) in various functional compartments of the rat pancreas. Using in situ hybridization by generating a radioactive cRNA probe from a specific cDNA clone for the rat glucocorticoid receptor we found a gradient in the expression of receptor mRNA transcripts from endocrine > acinar > ductal cells. In contrast, no specific hybridization signal was observed in the endothelial cells of vascular structures. Using a monospecific polyclonal antibody against the rat glucocorticoid receptor in Western blot analyses we found significant expression of the 94 kD receptor protein in an enriched pancreatic acinar cell preparation. This data suggest that rat pancreatic exocrine cells might serve a direct target tissue for glucocorticoid action.

[Anesthesia with flunitrazepam/fentanyl and isoflurane/fentanyl. Unconscious perception and mid-latency auditory evoked potentials]

There is a high incidence of intraoperative awareness during cardiac surgery. Mid-latency auditory evoked potentials (MLAEP) reflect the primary cortical processing of auditory stimuli. In the present study, we investigated MLAEP and explicit and implicit memory for information presented during cardiac anaesthesia. PATIENTS AND METHODS. Institutional approval and informed consent was obtained in 30 patients scheduled for elective cardiac surgery. Anaesthesia was induced in group I (n = 10) with flunitrazepam/fentanyl (0.01 mg/kg) and maintained with flunitrazepam/fentanyl (1.2 mg/h). The patients in group II (n = 10) received etomidate (0.25 mg/kg) and fentanyl (0.005 mg/kg) for induction and isoflurane (0.6-1.2 vol%)/fentanyl (1.2 mg/h) for maintenance of general anaesthesia. Group III (n = 10) served as a control and patients were anaesthetized as in I or II. After sternotomy an audiotape that included an implicit memory task was presented to the patients in groups I and II. The story of Robinson Crusoe was told, and it was suggested to the patients that they remember Robinson Crusoe when asked what they associated with the word Friday 3-5 days postoperatively. Auditory evoked potentials were recorded awake and during general anaesthesia before and after the audiotape presentation on vertex (positive) and mastoids on both sides (negative). Auditory clicks were presented binaurally at 70 dBnHL at a rate of 9.3 Hz. Using the electrodiagnostic system Pathfinder I (Nicolet), 1000 successive stimulus responses were averaged over a 100 ms poststimulus interval and analyzed off-line. Latencies of the peak V, Na, Pa were measured. V belongs to the brainstem-generated potentials, which demonstrates that auditory stimuli were correctly transduced. Na, Pa are generated in the primary auditory cortex of the temporal lobe and are the electrophysiological correlate of the primary cortical processing of the auditory stimuli. RESULTS. None of the patients had an explicit memory of intraoperative events. Five patients in group I, one patient in group II, and no patients in group III showed implicit memory of the intraoperative tape message. They remembered Robinson Crusoe spontaneously when they were asked their associations with Friday. In the awake state AEP peak latencies were in the normal range. During general anaesthesia in group I, the peaks Na, Pa did not increase in latency or decrease in amplitude before and after the audiotape presentation. The primary cortical complex Na/Pa could be identified as in the awake state. In contrast, in group II Na, Pa showed a marked increase in latency and a decrease in amplitude or were completely suppressed. CONCLUSIONS. During general anaesthesia auditory information can be processed and remembered postoperatively by an implicit memory function, when the electrophysiological conditions of primary cortical stimuli processing is preserved. Implicit memory can be observed more often when high-dose opioid analgesia is combined with receptor-binding agents like the benzodiazepines than under non-specific anaesthetics like isoflurane. Non-specific anaesthetics seem to provide a more effective suppression of auditory stimuli processing than receptor-specific agents.

Midlatency auditory evoked potentials and explicit and implicit memory in patients undergoing cardiac surgery

BACKGROUND

A high incidence of intraoperative awareness during cardiac surgery has been reported. Midlatency auditory evoked potentials (MLAEP) have been used recently as an indicator of awareness. In the current study, memory for information presented during anesthesia was investigated using MLAEP as one experimental indicator in 45 patients scheduled for elective cardiac surgery.

METHODS

In all patients general anesthesia was maintained using high-dosage fentanyl (1.2 mg.h-1). In addition, the patients of group 1 (n = 10) received flunitrazepam (1.2 mg.h-1), the patients of group 2 (n = 10) isoflurane (0.6-1.2 vol%), and the patients of group 3 (n = 10) propofol (4-8 mg.kg-1.h-1). Group 4 (n = 15) served as a control, and those patients were assigned randomly to one of the anesthetic regimes. After sternotomy and before cardiopulmonary bypass, an audiotape, which included an implicit memory task, was presented to the patients of groups 1-3. Auditory evoked potentials were recorded while the patients were awake and during general anesthesia immediately before and after the audiotape presentation. Latencies of the brain stem peak V and the early cortical potentials Na and Pa were measured.

RESULTS

Three to 5 days postoperatively no patient had a clear explicit memory of intraoperative events. However, there were statistically significant differences in the incidence of implicit recall among the groups. Five patients in the flunitrazepam-fentanyl group, 1 patient in the isoflurane-fentanyl group, 1 patient in the propofol-fentanyl group, and no patient in the control group showed an implicit memory of the intraoperative tape message. In the awake state, MLAEP showed high peak-to-peak amplitudes and a periodic waveform. In the patients with implicit memory postoperatively, MLAEP continued to show this pattern during general anesthesia. The early cortical potentials Na and Pa did not increase in latency or decrease in amplitude before or after the audiotape presentation. In contrast, in the patients without implicit memory, MLAEP waveform was severely attenuated or abolished. Na and Pa showed marked increases in latencies and decreases in amplitudes or were completely suppressed. In 9 patients, including all patients (7 of 9) with implicit memory, Pa latency increased less than 12 ms, and 21 of 23 patients without implicit memory showed a Pa latency increase of greater than 12 ms during anesthesia and the audiotape presentation. Therefore, the Pa latency increase of greater or less than 12 ms may provide sensitivity of 100% and specificity of 77% in distinguishing patients with implicit memory from patients without implicit memory postoperatively.

CONCLUSIONS

When the early cortical potentials of MLAEP are preserved during general anesthesia, auditory information may be processed and remembered postoperatively by an implicit memory task.