Arnulf Benzer

Noise in the ICU

ObjectiveThe growing number of technical devices in ICUs makes noise exposure a major stressor. The purpose of this study was to assess noise levels during routine operation in our ICU.DesignOur ICU is an open ward with four rooms, constructed in the 1960s. During the study period, 4 patients were in the controlled room and were treated by 4 nurses during the day and by 2 at night. A-weighted sound pressure levels (SPL) were measured continuously for 2 days and nights. Also measured were the alarms of various appliances. For gross overall evaluation it is customary to state the Leq, i.e. the energy-averaged level during measurement. The annoyance caused by noise depends more on rare events of high intensity. Therefore, the distribution of SPL values (Ln) over time was also analysed.ResultsSPL was roughly the same during the day and at night, with Leq between 60–65 dB(A) and peaks up to 96 dB(A). Most alarms reach an SPL of 60–70 dB(A), but some exceed 80 dB(A). During teaching rounds Leq exceeds 65 dB(A).ConclusionDuring the day and at night SPL always surpasses the permissible noise exposure for 24 h of 45 db(A) recommended by the US Environmental Protection Agency. Alarms cause the most irritating noise. Hospital management should pay attention to internal noise, and SPL should be measured routinely.

Molecular characterization of immunoreactivities of peptides derived from chromogranin a (GE-25) and from secretogranin II (secretoneurin) in human and bovine cerebrospinal fluid

Chromogranin A and secretogranin II are members of the so-called chromogranins, the acidic proteins stored in neuroendocrine large dense-core vesicles. We characterized chromogranin A and secretogranin II immunoreactivities in cerebrospinal fluid by radioimmunoassays using synthetic peptides derived from these components (GE-25 for chromogranin A and secretoneurin for secretogranin II). In lumbar cerebrospinal fluid, high levels (more than 1000 fmol/ml) of these two components were found, whereas in ventricular cerebrospinal fluid the secretoneurin levels were relatively low. The cerebrospinal fluid/serum ratio for secretoneurin was close to 170. High-performance liquid chromatography revealed that in both cerebrospinal fluid and extracts from human brain secretoneurin was the predominant immunoreactive component. In cerebrospinal fluid chromogranin A immunoreactivity was present as intermediate-sized peptides with little intact chromogranin A and free GE-25 peptide. In human brain samples smaller peptides including GE-25 were more predominant. Analogous findings for secretoneurin and chromogranin A were obtained for bovine brain samples. We can conclude that chromogranins are present in cerebrospinal fluid in concentrations much higher than those of classical neuropeptides also stored in large dense-core vesicles. Therefore, their degree of proteolytic processing can be analysed with small samples of cerebrospinal fluid. A possible disturbance of proteolytic processing in large dense-core vesicles in various pathological conditions can now be discovered.

CSF of neuroleptic-naive first-episode schizophrenic patients: Levels of biogenic amines, substance P, and peptides derived from chromogranin A (GE-25) and secretogranin II (secretoneurin)

Lumbar cerebrospinal fluid (CSF) was collected from controls and neuroleptic-naive patients with their first acute schizophrenic episode. The CSF was analyzed for several biogenic amines and their metabolites [dopamine,dihydroxyphenylacetic acid (DOPAC), noradrenaline, 5-hydroxytryptamine (5-HT), 5-hydroxyindolacetic acid (5-HIAA)]. For these transmitters, which are stored and secreted from synaptic vesicles, there was no significant difference between controls and schizophrenic patients. As constituents of large dense-core vesicles substance P (SP) and GE-25 (derived from chromogranin A)-and secretoneurin (derived from secretogranin 11)-immunoreactivities were determined. SP-like immunoreactivity levels did not differ between controls and patients; however, GE-25 was elevated and especially the GE-25/secretoneurin ratio was significantly (p < .001) higher in patients. Characterization of the immunoreactivities by high-performance liquid chromatography did not reveal any difference between patients (n = 3) and controls in the processing of the two proproteins chromogranin A and secretogranin II. These data indicate that proteolytic processing of the two widespread constituents of large dense-core vesicles, i.e., chromogranin A and secretogranin II, is not altered in schizophrenic patients. The increase in the chromogranin A /secretoneurin ratio in schizophrenic patients deserves further investigation in order to elucidate its possible pathogenetic significance.

The influence of hyperoxia on regional cerebral blood flow (rCBF), regional cerebral blood volume (rCBV) and cerebral blood flow velocity in the middle cerebral artery (CBFVMCA) in human volunteers

Conflicting results reported on the effects of hyperoxia on cerebral hemodynamics have been attributed mainly to methodical and species differences. In the present study contrast-enhanced magnetic resonance imaging (MRI) perfusion measurement was used to analyze the influence of hyperoxia (fraction of inspired oxygen (FiO2) = 1.0) on regional cerebral blood flow (rCBF) and regional cerebral blood volume (rCBV) in awake, normoventilating volunteers (n = 19). Furthermore, the experiment was repeated in 20 volunteers for transcranial Doppler sonography (TCD) measurement of cerebral blood flow velocity in the middle cerebral artery (CBFV(MCA)). When compared to normoxia (FiO2 = 0.21), hyperoxia heterogeneously influenced rCBV (4.95 +/- 0.02 to 12.87 +/- 0.08 mL/100g (FiO2 = 0.21) vs. 4.50 +/- 0.02 to 13.09 +/- 0.09 mL/100g (FiO2 = 1.0). In contrast, hyperoxia diminished rCBF in all regions (68.08 +/- 0.38 to 199.58 +/- 1.58 mL/100g/min (FiO2 = 0.21) vs. 58.63 +/- 0.32 to 175.16 +/- 1.51 mL/100g/min (FiO2 = 1.0)) except in parietal and left frontal gray matter. CBFV(MCA) remained unchanged regardless of the inspired oxygen fraction (62 +/- 9 cm/s (FiO2 = 0.21) vs. 64 +/- 8 cm/s (FiO2 = 1.0)). Finding CBFV(MCA) unchanged during hyperoxia is consistent with the present studys unchanged rCBF in parietal and left frontal gray matter. In these fronto-parietal regions predominantly fed by the middle cerebral artery, the vasoconstrictor effect of oxygen was probably counteracted by increased perfusion of foci of neuronal activity controlling general behavior and arousal.

Extended duration of action of rocuronium in postpartum patients.

We studied the time course of action of a single bolus of 600 micro g/kg rocuronium given during anesthesia with propofol, fentanyl, and nitrous oxide was studied in 12 nonpregnant and 12 postpartum patients.Neuromuscular effects were quantified by recording the indirectly evoked twitch response of the adductor pollicis muscle after ulnar nerve stimulation. In all patients, the trachea was intubated 60 s after administration of rocuronium. Onset time was similar in both groups (nonpregnant: 91 +/- 28 s vs. postpartum: 95 +/- 30 s), with the time to 25% twitch recovery being significantly longer (P < 0.001) in the postpartum patients (31.1 +/- 3.6 min) compared with the nonpregnant group (24.9 +/- 4.0 min). The time required for recovery from 25% to 75% of the control twitch response after reversal with neostigmine and atropine was significantly longer (P = 0.003) in postpartum (4.8 +/- 0.9 min) than in nonpregnant patients (3.2 +/- 0.6 min). These data suggest that pregnancy-induced changes result in prolonged effects of rocuronium in postpartum patients. (Anesth Analg 1997;84:352-4)

Phase-contrast MRI measurement of systolic cerebrospinal fluid peak velocity (CSFVPeak) in the aqueduct of Sylvius : A noninvasive tool for measurement of cerebral capacity

BACKGROUND Cerebrospinal fluid (CSF) outflow to intra- and extracranial subarachnoid spaces caused by arterial inflow to the brain predominantly compensates systolic increases in cerebral blood volume. Phase-contrast magnetic resonance imaging is a new tool for noninvasive assessment of CSF displacement by measuring CSF peak velocity (CSFV(Peak)). The authors tested this new tool in an experimental human model of increased intracranial pressure and reduced cerebral capacity by means of continuous positive airway pressure (CPAP) breathing. METHODS The authors investigated systolic CSFV(Peak) in the aqueduct of Sylvius in 11 awake, normocapnic (end-tidal carbon dioxide [ET(CO2)] = 40 mmHg) volunteers without CPAP and at two different CPAP levels (6 and 12 cm H2O) by means of electroencephalography-gated phase-contrast magnetic resonance imaging. RESULTS Administration of 6 cm H2O CPAP did not change systolic CSFV(Peak) (-4.9+/-2.8 cm/s vs. control: -5.1+/-2.7 cm/s), whereas 12 cm H2O CPAP significantly reduced systolic CSFV(Peak) (-4.0+/-1.8 cm/s vs. control: -5.1+/-2.7 cm/s; P < 0.05). CONCLUSIONS These findings in awake volunteers show that monitoring CSFV(Peak) in the aqueduct of Sylvius is a sensitive method for detecting even minor impairment of cerebral capacity caused by experimentally induced increases in intracranial pressure.

The influence of nitrous oxide and remifentanil on cerebral hemodynamics in conscious human volunteers.

Remifentanil is increasingly used in the context of anesthesia, e.g., in patients presenting for MRI examinations, not only as an analgesic but also to replace nitrous oxide. Therefore, a comparative analysis of the effects of commonly used doses of remifentanil and of nitrous oxide on cerebral hemodynamics is warranted. The present study used contrast-enhanced magnetic resonance (MR) perfusion measurement to compare the effects of nitrous oxide (N(2)O/O(2) = 50%; n = 9) and remifentanil (0.1 microg/kg/min; n = 10) on regional cerebral blood flow (rCBF), regional cerebral blood volume (rCBV), and regional mean transit time (rMTT) in spontaneously breathing human volunteers. Remifentanil increased rCBF above all in basal ganglia, whereas in supratentorial gray matter the increase in rCBF was equal or even more pronounced when using nitrous oxide. In contrast, nitrous oxide produced a greater increase in rCBV in gray-matter regions than did remifentanil. In summary, nitrous oxide increased rCBV in all gray-matter regions more than did remifentanil. However, the increase in rCBF, especially in basal ganglia, was typically less pronounced than during infusion of remifentanil.

Routine handling of propofol prevents contamination as effectively as does strict adherence to the manufacturer’s recommendations

PurposePropofol is a potential vector of infection, because it contains no preservative. Thus, the manufacturer’s specific recommendations for preparing injections or infusions go beyond the guidelines commonly used in our operating rooms for preparing other iv drugs. The purpose of the present study was to determine whether in the daily routine of an operating theatre a modified propofol handling technique can prevent contamination as effectively as do the manufacturer’s handling recommendations.MethodsA total of 160 consecutive neurosurgical patients were allocated to either Group I (manufacturer’s handling recommendations: i.e., 1) disinfecting propofol vials and ampoules before filling syringes; 2) replacing empty syringes; 3) discarding all material at the end of surgery); or Group II (modified propofol handling protocol: i.e., I) refilling empty syringes; 2) renewing only the infusion line to the patient).ResultsTotal contamination rates were comparable in both groups (Group I: 14/160 (8.75%), Group II: 13/160 (8.13%) (χ2 = 0.074; P = 0.96). Frequency of contamination was not different between groups; either in sample I taken at the beginning of the procedure, (Group I: 5/80 (6.25%) vs Group II: 6/80 (7.5%); χ2 = 0.098; P = 0.76) or in sample 2, taken at the end, (Group I: 9/80 (11.25%) vs Group II: 7/80 (8.75%); χ2 = 0.278; P = 0.598).ConclusionWe conclude that in the daily routine of the operating theatre following a modified propofol handling protocol prevents contamination of propofol syringes as effectively as does adhering to the manufacturer’s specific handling recommendations. However, neither of the tested guidelines completely prevented contamination.RésuméObjectifLe propofol, ne contenant aucun agent de conservation, est un vecteur potentiel d’infection. C’est pourquoi les recommandations spécifiques du fabricant au sujet de la préparation d’injections ou de perfusions vont au delà des directives habituellement suivies dans nos salles d’opération pour la préparation d’autres médicaments intraveineux. Nous avons voulu déterminer si, en modifiant le maniement du propofol en salle d’opération, nous pouvions prévenir la contamination aussi efficacement qu’en suivant à la lettre les recommandations du fabricant.MéthodeUn total de 160 patients successifs de neurochirurgie ont été répartis en deux groupes. Pour le Groupe I on a suivi les recommandations du fabricant en 1) désinfectant les flacons et les ampoules de propofol avant de remplir les seringues; 2) remplaçant les seringues vides; 3) jetant tout le matériel à la fin de l’intervention chirurgicale. Pour le Groupe II, on a modifié le maniement du propofol en 1) remplissant les seringues vides et 2) en renouvelant seulement les tubulures à perfusion des patients.RésultatsLes taux de contamination totale sont comparables : 14/160 (8,75 %) dans le Groupe I et 13/160 (8,13 %) dans le Groupe II (χ2 = 0,074; P = 0,96). La fréquence de contamination ne diffère pas d’un groupe à l’autre, pour l’échantillon I prélevé au début de l’opération (Groupe I : 5/80 (6,25 %) vs Groupe II : 6/80 (7,5 %); χ2 = 0,098; P = 0,76) ou l’échantillon 2 à la fin (Groupe I : 9/80 (11,25 %)vs Groupe II : 7/80 (8,75 %); χ2 = 0,278; P = 0,598).ConclusionLusage quotidien d’un protocole modifié de maniement du propofol en salle d’opération prévient aussi efficacement la contamination des seringues que l’adhésion aux recommandations spécifiques du fabricant. Aucune des directives testées n’a permis d’éliminer complètement la contamination.

The impact of increased mean airway pressure on contrast‐enhanced MRI measurement of regional cerebral blood flow (rCBF), regional cerebral blood volume (rCBV), regional mean transit time (rMTT), and regional cerebrovascular resistance (rCVR) in human volunteers

Contrast‐enhanced magnetic resonance imaging (MRI) measurement of cerebral perfusion is a diagnostic procedure increasingly gaining access to clinical practice not only in spontaneously breathing patients but also in mechanically ventilated patients. Effects of increased mean airway pressure on cerebral perfusion are entirely possible. Therefore, the present study used continuous positive airway pressure (CPAP) (12 cm H2O) to study the effects of increased mean airway pressure on cerebral perfusion in volunteers. CPAP significantly reduced regional cerebral blood flow (rCBF) and regional cerebral blood volume (rCBV) but increased regional mean transit time (rMTT) and regional cerebrovascular resistance (rCVR). Active vasoconstriction (e.g., arterial) and/or passive compression of capillary and/or venous vessel areas are the most likely underlying mechanisms. The number of interhemispheric differences in rCBF, rCBV, rMTT, and rCVR found at baseline rose when mean airway pressure was increased. These results, although obtained in volunteers, should be taken into consideration for the interpretation of contrast‐enhanced MRI perfusion measurements in mechanically ventilated patients with an increased positive airway pressure. Hum. Brain Mapping 11:214–222, 2000.

A subanesthetic concentration of sevoflurane increases regional cerebral blood flow and regional cerebral blood volume and decreases regional mean transit time and regional cerebrovascular resistance in volunteers.

Inhaled anesthetics exert metabolically mediated effects on cerebral blood vessels both directly and indirectly. We investigated the effects of a 0.4 minimum alveolar subanesthetic concentration of sevoflurane on regional cerebral blood flow (rCBF), regional cerebral blood volume (rCBV), regional cerebrovascular resistance (rCVR), and regional mean transit time (rMTT) in volunteers by means of contrast-enhanced magnetic resonance imaging perfusion measurement. Sevoflurane increased rCBF by 16% to 55% (control, 55. 03 +/- 0.33 to 148.83 +/- 1.9 mL. 100 g(-1). min(-1); sevoflurane, 71.75 +/- 0.36 to 193.26 +/- 2.14 mL. 100 g(-1). min(-1)) and rCBV by 7% to 39% (control, 4.66 +/- 0.03 to 10.04 +/- 0.12 mL/100 g; sevoflurane, 5.04 +/- 0.03 to 13.6 +/- 0.15 mL/100 g); however, sevoflurane decreased rMTT by 7% to 18% (control, 3.75 +/- 0.04 to 5. 39 +/- 0.04 s; sevoflurane, 3.4 +/- 0.03 to 4.44 +/- 0.03 s) and rCVR by 22% to 36% (control, 0.74 +/- 0.01 to 1.9 +/- 0.2 mm Hg/[mL. 100 g(-1). min(-1)]; sevoflurane, 0.54 +/- 0.01 to 1.41 +/- 0.01 mm Hg/[mL. 100 g(-1). min(-1)]). Interhemispheric differences in rCBF, rCBV, and rCVR were markedly reduced after the administration of sevoflurane. These findings are consistent with the known direct vasodilating effect of sevoflurane. The decrease in rMTT further shows that rCBF increases more than does rCBV. Furthermore, we can show that the observed increase in rCBF during inhalation of sevoflurane is not explained by vasodilation alone.