Adrenocortical function and multiple organ failure in severe sepsis

BACKGROUND

Some patients with severe sepsis may have relative adrenocortical insufficiency, although not all studies confirm this finding. Corticosteroids play an important role in controlling excessive immune response, and they may reduce the severity of organ dysfunction in critical illness. In this prospective study, we investigated the incidence of adrenal insufficiency in severe sepsis and its relation to the development of multiple organ failure.

METHODS

Forty-one patients meeting the criteria for severe sepsis were studied. A short ACTH stimulation test was carried out within 24 h of the diagnosis of sepsis. Peak serum cortisol level < 680 nmol/L and a rise of less than 260 nmol/L were used as the criteria for relative adrenocortical insufficiency.

RESULTS

Relative adrenocortical insufficiency was detected in six patients. Duration of the ICU stay (P = 0.002) and mechanical ventilation (P = 0.024) were significantly longer in patients with impaired adrenal function. In the survivors, SOFA scores were significantly higher in patients with impaired adrenal function. The plasma ACTH levels were normal in most of the patients with relative adrenal insufficiency, whereas most patients with normal adrenal function had extremely low plasma ACTH levels.

CONCLUSION

The ICU stay was longer and multiple organ failure more severe in patients with impaired adrenocortical function. There was a clear dissociation between ACTH and cortisol levels in AAR patients. This finding suggests that the integrity of the hypothalamic-pituitary-adrenal axis may be impaired in severe sepsis.

Mismatch negativity is unaffected by top-down predictive information

The mismatch negativity (MMN) event-related brain potential is assumed to reflect a stimulus-driven change detection process. We examined whether MMN is sensitive to volitional control by testing whether MMN is affected by the subject's foreknowledge of the sound changes. Subjects were instructed to produce a sequence of button presses by pressing one button frequently and another infrequently. In the predictable condition, the frequently pressed button triggered the standard tone, the other button the deviant tone. In the unpredictable condition, each button press triggered the next tone of a prearranged standard/deviant sequence. No difference was found in the MMN amplitude, latency, or scalp distribution between the predictable and unpredictable conditions. This suggests that there is no direct top-down control over the MMN-generating process.

Effects of acoustic gradient noise from functional magnetic resonance imaging on auditory processing as reflected by event-related brain potentials

The processing of sound changes and involuntary attention to them has been widely studied with event-related brain potentials (ERPs). Recently, functional magnetic resonance imaging (fMRI) has been applied to determine the neural mechanisms of involuntary attention and the sources of the corresponding ERP components. The gradient-coil switching noise from the MRI scanner, however, is a challenge to any experimental design using auditory stimuli. In the present study, the effects of MRI noise on ERPs associated with preattentive processing of sound changes and involuntary switching of attention to them were investigated. Auditory stimuli consisted of frequently presented "standard" sounds, infrequent, slightly higher "deviant" sounds, and infrequent natural "novel" sounds. The standard and deviant sounds were either sinusoidal tones or musical chords, in separate stimulus sequences. The mismatch negativity (MMN) ERP associated with preattentive sound change detection was elicited by the deviant and novel sounds and was not affected by the prerecorded background MRI noise (in comparison with the condition with no background noise). The succeeding positive P3a ERP responses associated with involuntary attention switching elicited by novel sounds were also not affected by the MRI noise. However, in ERPs to standard tones and chords, the P1, N1, and P2 peak latencies were significantly prolonged by the MRI noise. Moreover, the amplitude of the subsequent "exogenous" N2 to the standard sounds was significantly attenuated by the presence of MRI noise. In conclusion, the present results suggest that in fMRI the background noise does not interfere with the imaging of auditory processing related to involuntary attention.

Changes in acoustic features and their conjunctions are processed by separate neuronal populations

We investigated the relationship between the neuronal populations involved in detecting change in two acoustic features and their conjunction. Equivalent current dipole (ECD) models of the magnetic mismatch negativity (MMNm) generators were calculated for infrequent changes in pitch, perceived sound source location, and the conjunction of these two features. All of these three changes elicited MMNms that were generated in the vicinity of auditory cortex. The location of the ECD best describing the MMNm to the conjunction deviant was anterior to those for the MMNm responses elicited by either one of the constituent features. The present data thus suggest that at least partially separate neuronal populations are involved in detecting change in acoustic features and feature conjunctions.

Bedside percutaneous tracheostomy: clinical comparison of Griggs and Fantoni techniques

Elective tracheostomy is widely considered the preferred airway management of patients on long-term ventilation. In addition to open tracheostomy, a number of percutaneous procedures have been introduced during the last two decades, among them techniques according to Griggs (guidewire dilating forceps, or GWDF) and to Fantoni (translaryngeal tracheostomy, or TLT). The aim of the study was to evaluate these two techniques in terms of perioperative complications, risks, and benefits in critically ill patients. A series of 100 critically ill adult patients on long-term ventilation underwent elective percutaneous tracheostomy, either according to the Griggs (n = 50) or Fantoni (n = 50) technique. Tracheostomy was performed under general anesthesia at the patient's bedside. The mean (+/-SD) operating times were short, 9.2 +/- 3.9 minutes (TLT) and 4.8 +/- 3.7 minutes (GWDF) on average. Perioperative complications were noted in 4% of patients during either TLT or GWDF and included massive bleeding, mediastinal emphysema, posterior tracheal wall injury, and pretracheal placement of the tracheostomy tube. With regard to oxygenation, pre- and postoperative arterial oxygen tension divided by the fraction of inspired oxygen (PaO2/FiO2) ratios did not vary significantly, and no perioperative hypoxia was noted regardless of the technique used. We conclude that both TLT and GWDF represent attractive, safe alternatives to conventional tracheostomy or other percutaneous procedures if carefully performed by experienced physicians and under bronchoscopic control.

Audiovestibular findings and location of an acoustic neuroma

Forty-one patients with unilateral acoustic neuroma (AN) were diagnosed by magnetic resonance imaging (MRI) between 1992 and 1997. All cases were analyzed with respect to tumor location and the results of audiometric examinations, auditory brainstem response (ABR) testing, and electronystagmography (ENG). Tumor location was determined by MRI and cases were divided into intracanalicular and extracanalicular sites. Intracanalicular tumors were significantly smaller than the extracanalicular ones The pure-tone hearing thresholds were better in ears with intracanalicular lesions than in those with extracanalicular ones. Respectively, speech reception thresholds were 33 dB and 45 dB, and speech discrimination scores 79% and 65%. ABR was abnormal in 98% of ANs, but was insufficient for determining tumor location. The ENG pursuit test was more frequently normal and the caloric side difference was smaller in ears with intracanalicular than extracanalicular AN. These findings show that the results of pure-tone and speech audiometry and ENG are better in ears with intracanalicular AN, while ABR results are similar regardless of tumor location.

Vitamins C and E protect isolated cardiomyocytes against oxidative damage

There is considerable evidence that oxygen free radicals are involved in reperfusion injury of ischemic myocardium. Epidemiologic studies showed an inverse correlation between plasma levels of alpha-tocopherol (vitamin E) and ascorbic acid (vitamin C) and mortality from ischemic heart disease. The present study examines the influence of both vitamins on the toxic effects of singlet oxygen on isolated rat cardiomyocytes. Freshly isolated cardiomyocytes from adult rats were exposed to singlet oxygen which was generated by photoactivation of the photosensitive dye rose bengal (10(-7) M). This procedure induced irreversible hypercontracture in about 95% of rod-shaped cardiomyocytes within 15 min after onset of photoactivation of rose bengal. Pretreatment with vitamin C (10(-5) to 10(-2) M) or E (10(-6) to 10(-3) M) reduced the number of hypercontracted cells after exposure to singlet oxygen in a concentration-dependent manner. Simultaneous application of both vitamins (vitamin E 10(-6) M plus vitamin C 10(-5) M or vitamin E 10(-5) M plus vitamin C 10(-4) M) revealed a marked overadditive protective effect against oxidative damage as compared with the single application of each vitamin. Our data show that alpha-tocopherol and ascorbic acid exert direct protective actions on isolated cardiomyocytes against oxidative damage and provide an overadditive effect if administered simultaneously.

Early percutaneous tracheostomy after median sternotomy

OBJECTIVE

Tracheostomy offers significant advantages over endotracheal intubation in patients requiring long-term assisted ventilation. However, in patients who have undergone median sternotomy, it is believed that the danger of microbial contamination and consecutive infection of the sternal wound with microbes from the tracheostomy is high when conventional tracheostomy is performed. In contrast, percutaneous techniques are less likely to result in tracheostomy infection and thus bacterial contamination of neighboring structures. Nonetheless, to date there has been no prospective study confirming or disproving this assumption. Our study evaluated outcome after percutaneous tracheostomy in patients with a median sternotomy.

METHODS

A total of 144 cardiac surgical patients had elective percutaneous tracheostomy at the bedside until postoperative day 14, with 4 different techniques. Systematic microbiologic monitoring of the sternal and tracheal wounds was used.

RESULTS

In 13 patients sternal wound infection was suspected, but was confirmed in only 4 (2.8%) patients who actually showed microbial contamination of the sternum. In 2 of these patients, the identified microbes were not identical to those cultured from the trachea. The other 2 patients had sternal and tracheal cultures positive for methicillin-resistant Staphylococcus aureus. Cross-contamination of the sternotomy with microbes from the patient's airways was therefore ruled out. No patient had clinical signs of tracheostomy infection. Likewise, there were no cases of mediastinitis.

CONCLUSIONS

On the basis of our data, we conclude that cross-contamination of the sternal wound with microbes from the trachea is not a problem. Elective percutaneous tracheostomy is safe, even if performed during the first 14 days after median sternotomy.

Separate time behaviors of the temporal and frontal mismatch negativity sources

It has been proposed that mismatch negativity (MMN) is generated by temporal and frontal lobe sources, the former being associated with change detection and the latter with involuntary switching of attention to sound change. If this switching of attention is triggered by the temporal cortex change-detection mechanism, one would expect that the frontal component of MMN is activated later than the temporal one. This was studied by using 64-channel electroencephalography (EEG) and 122-channel magnetoencephalography (MEG) with realistically shaped head models to determine the source current distribution in different lobes as a function of time. Minimum-norm estimation (MNE) was performed, constraining the solution to the reconstructed cortical sheet. The results support the hypothesis that the frontal MMN generator is activated later than the auditory cortex generator.

Esmolol cardioplegia in unstable coronary revascularisation patients. A randomised clinical trial

BACKGROUND

Esmolol has been studied and applied to control hypertension and tachycardia during open heart surgery. Esmolol has been used on a minor scale as a single cardioplegic agent. Little information is available on esmolol as a component of blood cardioplegia. In this prospective, randomised, double-blind clinical study we investigated whether esmolol improves cardioprotection in patients scheduled for an urgent coronary operation.

METHODS

Forty patients with unstable angina were operated using cold blood cardioplegia as the basic cardioprotective method. Cardioplegia was infused intermittently, and esmolol was given into the cardioplegia line (15 mg/min) during cold infusions. Patients with ongoing myocardial infarction were excluded.

RESULTS

The arrest time during the cardioplegic induction or the rate of spontaneous resumption of the heart rhythm did not differ significantly between the groups. The serial measurements of plasma creatine kinase MB-fraction activity (P=0.27), serum creatine kinase MB-fraction mass assay (P=0.16), troponin I (P=0.41) and myoglobin (P=0.14) similarly did not differ between the groups, nor did myocardial lactate extraction (P= 0.12).

CONCLUSION

Esmolol addition to blood cardioplegia did not increase the efficacy of cardioprotection in the present study setting in unstable patients during urgent coronary revascularisation.

Serotonergic blunting to meta-chlorophenylpiperazine (m-CPP) highly correlates with sustained childhood abuse in impulsive and autoaggressive female borderline patients

BACKGROUND

Disturbances of affect, impulse regulation, and autoaggressive behavior, which are all said to be related to an altered function of the central serotonergic (5-HT) system, are prominent features of borderline personality disorder (BPD). A high coincidence of childhood physical and sexual abuse is reported in these patients. Animal studies indicate that early, sustained stress correlates with a dysfunctional central 5-HT system. Therefore, we hypothesize that sustained traumatic stress in childhood affects the responsivity of the postsynaptic serotonergic system of traumatized BPD patients.

METHODS

Following Axis I, Axis II, and trauma assessment, a neuroendocrine challenge test was performed with the postsynaptic serotonergic agonist meta-chlorophenylpiperazine (m-CPP) in 12 impulsive and autoaggressive female patients with BPD and 9 matched healthy volunteers.

RESULTS

The cortisol and prolactin responses to the m-CPP challenge in BPD patients were significantly lower compared to those in controls. Within the group of patients with BPD, the net prolactin response showed a high inverse correlation with the frequency of the physical (r = -.77) and sexual abuse (r = -.60).

CONCLUSIONS

Our data suggest that severe and sustained traumatic stress in childhood affects the 5-HT system and especially 5-HT(1A) receptors. This finding confirms the data from animal research. The blunted prolactin response to m-CPP appears to be the result of severe traumatization and independent of the BPD diagnosis.

Adenosine with cold blood cardioplegia during coronary revascularization

OBJECTIVE

To investigate whether adenosine in association with blood cardioplegia results in more rapid cardiac arrest or improved myocardial protection.

DESIGN

A prospective, randomized, placebo-controlled double-blind clinical study.

SETTING

Operative and intensive care units in a university hospital, Finland.

PARTICIPANTS

Forty patients undergoing primary, elective coronary revascularization.

INTERVENTION

Adenosine as a bolus dose, 12 mg intravenously, was given immediately before the induction of blood cardioplegia.

MEASUREMENTS AND MAIN RESULTS

There were nonsignificantly higher serial serum values of CK (MB) (p = 0.33), troponin-T (p = 0.23), and troponin-I (p = 0.10) in the adenosine group. There were no differences between the groups in arrest time, blood pressure decrease, or lactate extraction.

CONCLUSIONS

The adenosine regimen used in this study did not cause more rapid arrest with blood cardioplegia. The effect on cardioprotection was insignificant.

Tracheostomy in cardiosurgical patients: surgical tracheostomy versus ciaglia and fantoni methods

BACKGROUND

Patients requiring prolonged mechanical ventilation are not uncommon in a cardiosurgical intensive care unit. Elective tracheostomy is considered the airway treatment of choice in these patients.

METHODS

To evaluate different techniques for tracheostomy, we prospectively investigated 120 patients who had conventional open (n = 40), minimally invasive percutaneous dilatational (n = 40), or translaryngeal (n = 40) tracheostomy techniques. The main areas of investigation included oxygenation index (partial pressure of arterial oxygen divided by fraction of inspired oxygen), complications, infection, and cost.

RESULTS

The oxygenation index decreased in almost every patient, regardless of the technique used, but the extent of decrease was significantly lower in both minimally invasive techniques compared with the conventional method. Overall complication rate was 12.5% both in open tracheostomy and in percutaneous dilatational tracheostomy, whereas no complications occurred in translaryngeal tracheostomy procedures. Bacterial contamination of the tracheostomy site was found in 35% of the open tracheostomies, whereas no infection was seen in percutaneous dilatational or translaryngeal tracheostomies. In terms of costs, PDT ($506) and TLT ($362) were both much cheaper than open tracheostomy ($699).

CONCLUSIONS

Percutaneous dilatational and translaryngeal tracheostomies are safe and cost-effective procedures that can be done easily at the patient's bedside and thus are attractive alternatives to conventional surgical tracheostomy in long-term airway access in a cardiosurgical intensive care unit.

Analysis of speech sounds is left-hemisphere predominant at 100-150ms after sound onset

Hemispheric specialization of human speech processing has been found in brain imaging studies using fMRI and PET. Due to the restricted time resolution, these methods cannot, however, determine the stage of auditory processing at which this specialization first emerges. We used a dense electrode array covering the whole scalp to record the mismatch negativity (MMN), an event-related brain potential (ERP) automatically elicited by occasional changes in sounds, which ranged from non-phonetic (tones) to phonetic (vowels). MMN can be used to probe auditory central processing on a millisecond scale with no attention-dependent task requirements. Our results indicate that speech processing occurs predominantly in the left hemisphere at the early, pre-attentive level of auditory analysis.

Effect of internal thoracic artery preparation on blood loss, lung function, and pain

BACKGROUND

Postoperative blood loss, respiratory distress, and pain after coronary artery operation were assessed in a prospective, randomized, clinical study comparing two techniques of internal thoracic artery preparation.

METHODS

In group A (n = 57) the internal thoracic artery was dissected with the entire surrounding connective tissue after opening the pleura, using routine lateral pleural drainage. In group B (n = 55) a venoarterial pedicle was prepared without surrounding muscle leaving the pleura intact. We assessed blood loss, clinical outcome, lung function, location, intensity, and quality of pain 6 days and 3 months after the operation.

RESULTS

Significantly higher blood loss was observed in group A (A, 608+/-58 mL; B, 470+/-48 mL; p = 0.027). Forced expiratory volume in 1 second was significantly decreased in group A 6 days after surgery (A, 76.0%+/-1.6%; B, 83.2%+/-1.6%; p = 0.020). The forced expiratory volume in 1 second correlated to inspiratory vital capacity, which confirmed the advantage of the venoarterial technique (A, 0.771+/-0.021; B, 0.832+/-0.020; p = 0.003). Vital capacity was significantly higher in the venoarterial group at 3 months (A, 85.2%+/-2.1%; B, 98.5%+/-1.2%; p = 0.009), but not on postoperative day 6. The incidence of pleural effusion and atelectasis was significantly higher in group A (effusion: A, 52.6%; B, 23.6%; p = 0.002; atelectasis: A, 42.1%; B, 20.0%, p = 0.015). Sternal pain (A, 36.8%; B, 9.1%; p = 0.001) and suspenders pain (A, 33.3%; B, 7.3%; p = 0.001) occurred more often in group A. When using a multidimensional pain score, patients in group A experienced significantly sharper (6 days: A, 6.7+/-0.3; B, 3.3+/-0.2; p = 0.018; 3 months: A, 3.5+/-0.3; B, 1.4+/-0.3; p = 0.046) and more annoying pain (6 days: A, 7.6+/-0.2; B, 2.7+/-0.1; p = 0.036; 3 months: A, 6.6+/-0.3; B, 2.3+/-0.2; p = 0.040).

CONCLUSIONS

These results demonstrate that the venoarterial preparation technique is superior to conventional internal thoracic artery preparation regarding postoperative blood loss, lung function, and pain.

Does lidocaine protect the heart during coronary revascularisation?

BACKGROUND

Lidocaine has been used as the primary antiarrhythmic agent for ventricular arrhythmias during acute myocardial infarction (MI) and open heart surgery. Its cardioprotective effects have been studied in experimental settings and also during angioplastic reperfusion and coronary revascularisation. The basic mechanism of action, probably also involved with cardioprotection, has been demonstrated to be blockade of cardiac sodium channels. In this open study we investigated the contribution of continuous lidocaine infusion to cardioprotection during coronary revascularisation with blood cardioplegia.

METHODS

During coronary revascularisation with cold blood cardioplegia, a study group of 50 patients received a prophylactic lidocaine infusion for 20 h started with a bolus dose before aortic clamping; another group of 50 patients without the infusion served as a control group. Serum troponin T concentration, serum creatine kinase MB activity and electrocardiography were the main parameters recorded.

RESULTS

Serial measurement of Troponin T (P = 0.06) and CK-MB values: (P = 0.09) were slightly lower in the lidocaine group, but the differences were not statistically significant.

CONCLUSION

Lacking statistically significant evidence of improved cardioprotection, lidocaine infusion cannot be recommended as a routine treatment during coronary revascularisation.

Bilateral loss of vestibular function: clinical findings in 53 patients

The clinical presentations and aetiologies of a series of 53 cases of bilateral vestibular failure (BVF) seen by the authors over a decade were evaluated by retrospective review of the medical records. Thirty-nine per cent of patients had associated neurological disease; 13% had a progressive cerebellar syndrome with disabling gait ataxia, abnormal eye movements and cerebellar atrophy on neuro-imaging. BVF was usually unsuspected. Nine per cent had cranial or peripheral neuropathies and in this group there was no abnormality of brain stem/cerebellar oculomotor function, but hearing loss was common. Eleven per cent revealed BVF and hearing loss secondary to meningitis, and 6% had other neurological disorders. Idiopathic BVF was found in 21% of cases, characterised by paroxysmal vertigo and/or oscillopsia, but no abnormal clinical signs. Gentamicin ototoxicity accounted for a further 17%, while autoimmune disease was present in 9% of patients. Otological or neoplastic disease was diagnosed in the remaining 13% of patients. It was concluded that neurological, audiological and ocular motor assessments allow the probable cause of BVF to be defined in approximately 80% of cases. A group of BVF related to autoimmune pathologies is reported for the first time, indicating the need for immunological screening. Idiopathic BVF may present with only minor visual or vestibular symptoms, while in patients with cerebellar degeneration, BVF may be unsuspected and, thus, underdiagnosed.

The mismatch negativity for duration decrement of auditory stimuli in healthy subjects

The amplitude and latency of the mismatch negativity (MMN) elicited by occasional shorter-duration tones (25 and 50 ms) in a sequence of 75 ms standard tones were studied in 40 healthy subjects (9-84 years). The replicability and age dependence of the MMN-responses were determined. The 25 ms deviant tone evoked a clear response in 39 of the subjects, while the 50 ms deviant tone evoked an observable MMN only in 32 of the subjects. The MMN peak amplitude for the 25 ms deviants was significantly larger than for the 50 ms deviants. There was no significant difference in the peak latencies (measured from stimulus offset). For the 25 ms deviant, the amplitude diminished with increasing age. The MMN curves for the 25 ms deviant, measured on separate days in 14 subjects, looked very replicable. As a result of noise and filtering effect, the product-moment correlations were poor. The results indicate that the signal-to-noise ratio for the MMN to 25 ms deviants, obtained even in a 25 min recording session, is large enough for clinical use and individual diagnostics when undetectable (or very low amplitude) MMN is used as a sign of pathology. However, judged from the low correlation coefficients, despite the good replicability in visual evaluation, better methods for MMN quantification have to be used for clinical follow-up.

Electrophysiological evidence for cross-modal plasticity in humans with early- and late-onset blindness

It is commonly believed that sensory deprivation can lead to cross-modal reorganization in an immature but not in a mature brain. The results of the present study suggest, however, that plasticity between sensory modalities is possible even in adults: activity indicating involvement of parietal or occipital brain areas in pitch-change discrimination was found in individuals blinded after childhood. Event-related brain potentials of early blinded (before the age of 2 years), late-blinded (12-28 years of age), and sighted adults were recorded to stimulus sequences consisting of standard tones occasionally replaced by deviant tones. Even when participants were not attending to auditory stimuli, the deviant tones elicited the mismatch negativity (MMN) in each group. There were no significant MMN front-back scalp distribution differences among the groups. However, when participants were detecting deviant stimuli, these stimuli elicited N2 and P3 waves that were posterior in distribution in both groups of blind participants relative to those of the sighted participants. These results suggest that cross-modal reorganization may occur even in the mature human brain.

MEG-compatible multichannel EEG electrode array

We describe an EEG electrode array, which is designed to facilitate simultaneous multichannel EEG and MEG recordings. The special electrode design allows shorter preparation times and more reliable contacts than commercially available solutions. The electrode array is magnetically compatible with MEG and the low-profile electrodes consume minimal space inside the magnetometer.

Protective action of hydroxyethyl rutosides on singlet oxygen challenged cardiomyocytes

1. The effect of a standardized mixture of beta-hydroxyethyl rutosides against oxidative damage in singlet oxygen-challenged isolated cardiac myocytes from adult rats was investigated. The morphology of the myocytes was evaluated as an indicator for cell viability (elongated, rod shaped cells vs. hypercontracted, rounded cells). The determination of the production of thiobarbituric acid reactive substances served as an indicator for lipid peroxidation. 2. Exposure to singlet oxygen which was generated by photo-excitation of rose bengal (10(-7) M) reduced the number of rod shaped (vital) cardiomyocytes by 78.5 +/- 2.5% and increased the production of thiobarbituric acid reactive substances by 1180 +/- 150% in comparison to incubation with control buffer. 3. Coincubation of the cells with beta-hydroxyethyl rutosides (concentration range: 6.7 pg ml-1 to 670 micrograms ml-1) increased the number of rod shape cardiomyocytes after exposure to singlet oxygen in a dose-dependent bell-shaped manner. A significant protective effect was observed at beta-hydroxyethyl rutosides concentrations ranging from 0.67 ng ml-1 to 67 ng ml-1. 4. In spite of their protective action, beta-hydroxyethyl rutosides did not reduce the accumulation of thiobarbituric acid reactive substances, used as an indicator for lipid peroxidation. 5. The data suggest that beta-hydroxyethyl rutosides exert a protective action against oxygen radical-induced damage of cardiac myocytes at very low concentrations without interfering with lipid peroxidation.

The ontogenetically earliest discriminative response of the human brain

Speech sounds elicited electric brain responses in healthy premature infants born 30-35 weeks after conception, demonstrating that the human brain is able to discriminate speech sounds even at this early age, well before term, and supporting previous results suggesting that the human fetus may learn to discriminate sounds while still in the womb. We presented preterm infants with stimulus sequences consisting of a repetitive vowel that was occasionally replaced by a different vowel. This infrequent vowel elicited a response resembling the adult mismatch negativity, which is known to reflect the brain's automatic detection of stimulus change. The present results constitute the ontogenetically earliest discriminative response of the human brain ever recorded.

Aging effects on auditory processing: an event-related potential study

Deviant tones randomly embedded in a sequence of standard tones elicit an event-related potential (ERP) called the mismatch negativity (MMN), which reflects automatic stimulus-change detection in the human auditory system. When the tones are attended, deviant tones elicit also an N2b component that partly overlaps the MMN. Sequences of standard and deviant (probability 0.15) tones were presented to 13 healthy younger and 13 older subjects. Deviant stimuli were, in separate blocks, either occasional shorter duration or higher frequency tones. The interstimulus interval (ISI) was, in separate blocks, either 0.5 s or 1.5 s, and in the frequency-change condition also 4.5 s. Aging affected neither frequency nor duration of MMN with the 0.5 s ISI. This finding indicates that automatic stimulus discrimination per se is not impaired with normal aging. However, with a 4.5-s ISI the MMN/N2b-complex attenuated significantly more in the older than younger subjects. This suggests that the stimulus trace decays faster or that involuntary attention switching is less sensitive with aging.

Variability and replicability of the mismatch negativity

The interindividual variation and test-retest stability of the mismatch negativity (MMN) and N1 components of the event-related potential (ERP) were investigated by presenting standard (85%) and deviant tones (15%) to 10 young subjects in 2 sessions separated by 1 month. Deviant tones in different blocks were either frequency or duration changes with interstimulus intervals (ISIs) of 0.5 and 1.5 sec. The results showed a fairly good test-retest stability of the MMN amplitude for both types of changes with each ISI at the group level. The amplitude of the duration MMN showed significant individual test-retest stability. The N1 amplitude showed high stability at both the group and individual levels. Both the MMN and N1 showed considerable interindividual variation. The results suggest that MMN and N1 can be used in follow-up studies not only at the group level but possibly at the individual level also.

Age-related functional differences between auditory cortices: a whole-head MEG study

Auditory evoked magnetic fields (AEFs) were recorded from 10 healthy younger and 10 older subjects using a whole-head magnetometer. Two blocks of tone pips were presented to the left ear with constant inter-stimulus intervals (ISIs) of 0.5 and 2.5 s. The amplitude of P50m, unlike that of N100m, was larger in the older subjects. In both groups, the peak latencies of P50m and N100m responses were significantly shorter over the contralateral than ipsilateral cortex. The interhemispheric latency difference of N100m was significantly increased with age. These findings suggest that ageing delays signal processing in the ipsilateral auditory cortex and that ageing affects consecutive AEFs in a different manner.

Bilateral loss of vestibular function

The clinical findings in 53 patients with bilateral vestibular failure (BVF) seen in a neurological hospital are reported. Bilateral acoustic neuromas were excluded. Seven patients (13%) had progressive cerebellar degeneration; these patients had no hearing complaints but showed gait ataxia, abnormal eye movements and cerebellar atrophy on neuro-imaging. Referral in these patients was primarily for eye movement assessment, and BVF was usually unsuspected. Neuropathies were present in 5 patients (9%), usually with normal central (brainstem-cerebellar) ocular motor function and variable patterns of hearing loss. The single largest group was idiopathic BVF (11 patients, 21%), patients presenting with vertiginous episodes, progressive unsteadiness or brief paroxysms of oscillopsia; auditory function, eye movements, neurological examination and imaging were usually normal. Nine patients (17%) suffered ototoxicity, mostly due to gentamicin; hearing was normal or mildly impaired. In 6 patients (11%) BVF was post-meningitic, with concomitant auditory loss. Autoimmune disease was found in 5 patients (9%); other organs were involved by the disease, and hearing was impaired but eye movements were spared. Miscellaneous neurological, otological or neoplastic diseases accounted for the remaining 10 patients. This study suggests that i) in patients with cerebellar degenerations, BVF may be underdiagnosed as the unsteadiness may be attributed only to the cerebellar disorder, ii) some patients with idiopathic BVF present with only minor visual or vestibular symptoms, and iii) detailed immunological screenings should be undertaken more often, in view of the significant proportion of patients with autoimmune and idiopathic BVF.

Comparison of cardioprotection with crystalloid and blood cardioplegia in CABG patients

One hundred patients scheduled for elective coronary artery bypass grafting (CABG) were randomly allocated to two groups for myocardial preservation:blood cardioplegia (BCP) or crystalloid cardioplegia (CCP). The study protocol comprised recording of the following parameters: mode of resumption of cardiac rhythm, CK-MB analysis, ECG recording, cardiac output measurement, cross-clamping and perfusion times, and clinical outcome. The study period covered the time from commencement of anesthesia to the first postoperative morning. Spontaneous resumption of sinus rhythm was recorded only in the BCP group (22/51 v 0/49, P < 0.001). CK-MB values were similar in both groups, but 1 hour postoperatively the BCP group had lower values (58.8 +/- 26.7 v 74.5 +/- 31.5 U/L, P = 0.0098 by t test). Fifteen patients in the BCP group did not receive any electric countershock; this subgroup had very low CK-MB values. There were four intraoperative myocardial infarctions in the BCP group and two in the CCP group (BCP: 3/51 v CCP: 3/49, P = 0.68). The results suggest better cardioprotection with blood cardioplegia in this subgroup of patients. Spontaneous resumption of normal cardiac rhythm seems to indicate good myocardial preservation, as reflected in markedly lower CK-MB values in this subgroup.