[Positioning therapy in intensive care medicine in Germany. Results of a national survey]. / Einsatz der Lagerungstherapie auf deutschen Intensivstationen. Ergebnisse einer Umfrage.

BACKGROUND: The effects of a systematic change in a patient's position [prone position, continuous lateral rotational therapy (CLRT)] have been investigated in recent years in acute lung injury and have shown an improvement in oxygenation, but controversial results regarding duration of mechanical ventilation, intensive care treatment and mortality compared to conventionally treated patients. We were interested in the practice and acceptance of positioning therapy in German intensive care units (ICU) and performed a national postal survey with respect to evaluation of indications, preference of particular positions, observed complications and additional aspects (costs, influence on other intensive care measures etc.). METHODS: A questionnaire (12 multiple choice items) was sent to 1,763 ICUs, which were identified from the "Deutsches Krankenhausadressbuch" (German hospital address book 2005). The analysis was performed anonymously. RESULTS: A total of 702 questionnaires (40.4%) were returned and analysed. The 135 degrees position (incomplete prone position) was most frequently used (50%), while the prone position (25%) and CLRT (18%) were less frequent. The improvement in oxygenation (95%) and the prevention of ventilator-associated complications (75.7%) were important indications for positioning therapy. Results of a blood gas analysis provided the necessary criteria for determining positional therapy. Supporters of the prone position advocated lower cost and better efficacy in comparison to CLRT. The frequency of complications during positioning therapy was reported to be high: hemodynamic instability (73.6%), accidental loss of tube/catheters (50.4%) and patient intolerance (40.7%) were often observed, and complication-free positioning therapy was reported in only 8.6%. CONCLUSIONS: The 135 degrees position (incomplete prone position) is the most frequently used positioning therapy in Germany for improvement of oxygenation in patients with acute lung injury. Prone position and CLRT are less frequently used, probably due to an increased frequency of (expected) complications. The authors assume that clear guidelines and algorithms are needed to establish a more routine, safe practical application and a reduction in the complication rate.

Impact of the Narcotrend Index on propofol consumption and emergence times during total intravenous anaesthesia with propofol and remifentanil in children: a clinical utility study.

BACKGROUND AND OBJECTIVE: The electroencephalographic Narcotrend Index (NI) is a measure of the hypnotic component of general anaesthesia. The purpose of this study was to evaluate the impact of Narcotrend guidance on propofol consumption and emergence times in children receiving total intravenous anaesthesia with propofol and remifentanil. METHODS: Thirty children, aged 1-11 yr, scheduled for paediatric urological surgery were enrolled. Remifentanil was given to all patients at a constant infusion rate of 0.3 microg kg [-1] min[-1] throughout anaesthesia. Patients were randomly allocated to receive a continuous propofol infusion adjusted either according to a conventional clinical practice (Group C: n=15) or guided by Narcotrend monitoring (Group NI: n=15; target NI 60+/-5). All patients were connected to the Narcotrend Monitor, but in Group C the anaesthetist was blinded to the screen of the monitor. Propofol consumption (mg kg[-1]h[-1]) and emergence times (min) were the primary and secondary outcome measures. RESULTS: Propofol consumption (median [inter-quartile range]) was significantly lower in Group NI compared to Group C (NI: 7.0 [6.4--8.2] vs. C: 9.3 [8.3--11.0] mg kg[-1]h[-1]; P<0.001), whereas Log-Rank-analysis revealed no intergroup difference in emergence times (Group NI: mean [95% confidence interval (CI)] 12.8 [11.2--14.4] min; Group C: 16.4 [12.6--20.2] min; P=0.10). Haemodynamic variables remained stable within age-related limits, and there were no observations of adverse events, especially no clinical signs of intraoperative awareness in any patient. CONCLUSION: Narcotrend monitoring for guidance of propofol/remifentanil anaesthesia in children results in reduced propofol consumption compared to a conventional clinical practice.

Clearance of moxifloxacin during continuous haemofiltration (CVVHF) in vitro.

BACKGROUND/AIMS: The clearance of moxifloxacin is reported to be unaltered in the presence of renal insufficiency. There is little information about the clearance of intravenous moxifloxacin in renal replacement therapies during intensive care. The aim of this study was to determine the clearance of moxifloxacin during continuous veno-venous haemofiltration (CVVHF) in vitro. METHODS: The elimination of moxifloxacin (reservoir with 600 mL of washed human erythrocytes, 100 mL of NaHCO3 and various amounts of Ringer solution and human albumin to give a total volume of 1000 mL, pH 7.35 +/- 0.5; haematocrit 41 +/- 2) during CVVHF in vitro with two filter conditions (during priming, after priming), three protein concentrations (human albumin: 0 g/L, 20 g/L, 40 g/L) and two filtration velocities [(i) standard condition: blood flow at 100 mL/min and turnover of 2 L/h; (ii) blood flow at 50 mL/min and turnover of 1 L/h] were investigated. RESULTS: A new filter needs 20 min of priming before moxifloxacin reaches a steady relative filtration rate. The sieving coefficient with 0 g/L albumin was 1.07, with 20 g/L 0.90 and with 40 g/L 0.80. Under standard filtration conditions (i) the renal clearance was between 26.7 and 35.7 mL/min, and under the altered conditions (ii) it was 15.2 mL/min. CONCLUSION: During CVVHF in vitro we found filtration clearances of moxifloxacin of the same order as its renal clearance in healthy subjects. The high sieving coefficient, nearly independent of blood protein concentration, would suggest that moxifloxacin is filtered almost as freely as creatinine. These results do not indicate a need for dose adjustment under appropriate haemofiltration conditions and normal hepatic function.

[Comparison of incomplete (135 degrees ) and complete prone position (180 degrees ) in patients with acute respiratory distress syndrome. Results of a prospective, randomised trial]. / Vergleich von inkompletter (135 degrees) und kompletter Bauchlage (180 degrees) beim schweren akuten Lungenversagen. Ergebnisse einer prospektiven, randomisierten Untersuchung.

BACKGROUND: Ventilation in the prone position is carried out for improvement of pulmonary gas exchange in patients with acute respiratory distress syndrome (ARDS). We compared the effects of an incomplete prone position (IPP, 135( degrees )) with a complete prone position (CPP, 180( degrees )) in patients with ARDS. PATIENTS AND METHODS: For this trial 59 patients with ARDS were randomly assigned and were positioned in a "cross-over" design: patients of group A were placed in IPP for 6 h and then immediately positioned in CPP for another 6 h. Patients in group B were positioned in reverse order. Blood gases, hemodynamic measurements, quasistatic respiratory compliance and assessments of side effects were performed before begin, 30 min and 6 h after first positioning, then 30 min and 6 h after second positioning and 2 after repositioning. RESULTS: Turning patients in IPP and CPP resulted in a significant increase in the arterial oxygenation index (p(a)O(2)/F(I)O(2)), but this effect was more pronounced in the CPP (before: 142+/-46 mm Hg, 6 h: 253+/-107 mm Hg) than in the IPP (before: 139+/-54 mm Hg, 6 h: 206+/-75 mm Hg), and compliance was improved only in CPP. The improvement in arterial oxygenation persisted 2 h after repositioning in the supine position in both groups. The oxygenation responder rate was lower during the IPP (70.3%) in comparison with the CPP (84.0%, p<0.05). The incidence of side effects tended to be increased during the CPP. CONCLUSION: Incomplete prone position improves oxygenation in ARDS patients, but less effectively than a "classic" CPP. In these patients the use of a CPP should be preferred.

[Pumpless extracorporeal lung assist using arterio-venous shunt in severe ARDS. Experience with 30 cases]. / Pumpenfreie extrakorporale Lungenunterstützung mit arteriovenösem Shunt beim schweren akuten Lungenversagen des Erwachsenen. Bericht über 30 Einsätze.

BACKGROUND: Extracorporeal lung assist has been proposed as an invasive measure in patients with acute respiratory distress syndrome (ARDS) when oxygenation is critically impaired. However, this technique generally requires high personnel and technical resources. We report on a new system, which is characterised by a short circuit arterio-venous shunt using arterio-venous pressure gradient as driving force (pumpless extracorporeal lung assist [pECLA]). PATIENTS AND METHODS: In 30 patients with ARDS due to multitrauma, pneumonia or after surgery (p(a)O(2)/F(I)O(2)-ratio 67+/-23 mmHg) pECLA was established by insertion of cannulae to the femoral artery and vein followed by connection with a membrane gas exchanger. For this system, only "low dose" continuous heparin infusion is required. RESULTS: Arterial oxygenation was acutely and significantly increased by pECLA (p(a)O(2)/F(I)O(2)=103+/-56 mmHg 2 h after begin) and carbon dioxide removal was markedly enhanced in 25 out of 30 patients (87%) allowing a lung protective ventilation strategy. The mean duration of pECLA therapy was 6.5 days, 15 patients (50%) died due to ARDS or non-ARDS related reasons. CONCLUSION: pECLA represents a feasable and effective treatment in patients with severe ARDS. Compared with pump-driven systems pECLA is characterised by low costs and reduced personnel requirements. However, mortality remains high in patients suffering from severe ARDS despite newer treatment modalities.

[Anaesthesia for radiation therapy of brain tumours in children. A multidisciplinary challenge]. / Anästhesie zur Radiotherapie kindlicher Hirntumoren. Eine multidisziplinäre Herausforderung.

Radiation therapy of childhood intracranial malignancies is always a challenge for radiation oncologists, anaesthetists and paediatric oncologists. Detailed knowledge of the course of the disease prior to radiation therapy and a critical evaluation of the child's actual physical status are mandatory in each case. Furthermore the anaesthetist should be informed about the child's individual preferences and aversions. The optimum prearrangement of the radiation therapy is of paramount importance. Interdisciplinary communication structures which must always involve the child's parents have to be established. Perfect adjustment of the mask that fixes the head during each radiation procedure is necessary to give the child the possibility to breathe spontaneously without an endotracheal tube or a laryngeal mask. Two case reports highlight these aspects of the complex procedure of paediatric radiation therapy which are relevant for the anaesthetist.

[Hb 1.1 g/dl: successful treatment of a polytraumatized patient in hemorrhagic shock]. / Hb=1,1 g/dl: erfolgreiche Behandlung nach Polytrauma mit schwerem hämorrhagischen Schock. Effektives Zusammenspiel von präklinischer Versorgung, Schockraummanagement und Intensivtherapie.

We report on the successful treatment of a seriously traumatized patient (injury severity score=59) who presented with exsanguinating hemorrhage in the emergency room. Preclinical and emergency room management included "small volume" hypertonic resuscitation as well as massive transfusion, C-clamp stabilization of a pelvic ring instability, and attachment of external fixators to multiple bone fractures. During the intensive care period,we started enteral immunonutrition immediately after an abdominal compartment syndrome was removed by laparotomy and a jejunal catheter had been inserted. Multiple fractures were stabilized rapidly and the soft tissue wounds were covered by split skin grafts. Additionally, we provided sufficient analgesia with few side effects using an epidural catheter for continuous application of local anesthetics. In summary, an effective synthesis of up-to-date strategies for preclinical, emergency room, and intensive care management prevented multiple organ failure and achieved survival with good quality of life after a "fatal" multiple trauma.

[ARDS and severe brain injury. Therapeutic strategies in conflict]. / ARDS und schweres Schädelhirntrauma. Therapiestrategien im Konflikt.

The development of adult respiratory distress syndrome (ARDS) complicates the treatment of patients with severe head injury, since special therapeutic strategies for both conditions might lead to a "conflict of interest". We report on the intensive care treatment of a young man who suffered severe brain injury (Glasgow Coma Scale = 3) due to a traffic accident and simultaneously developed ARDS from the aspiration of gastric content. We performed extensive monitoring of cerebral hemodynamics and metabolism (intracranial pressure measurement, jugular bulb oxymetry, estimation of arterial-jugular bulb lactate concentration difference) to prevent cerebral hypoxia and to control cerebral hyperemia. The application of a "lung protective strategy" with "permissive hypercapnia" led to a conflict, since the development of cranial hyperemia combined with cranial hypertension a few days after trauma, warranted the concept of controlled, temporary hyperventilation. Therefore, we applied a pumpless extracorporeal lung assist to improve carbon dioxide elimination. Furthermore, we started the ventilation in the prone position, since arterial oxygenation continued to deteriorate, although there is a lack of data describing the effect of a prone position on acute cerebral injury. Positioning the patient prone, we observed a prompt increase in intracranial pressure, which resulted in pharmacological intervention (mannitol). Treating the patient by intermittent prone position, by continuous extracorporeal lung assist and aerosolized prostacyclin administration in the following period, lung function improved and ARDS was treated successfully. After withdrawing the analgo-sedation the patient's vigilance rose continuously. The patient was transferred to a rehabilitation ward 33 days after admission to the intensive care unit. The combination of ARDS and severe brain injury needs special treatment, which includes extensive monitoring techniques to find a solution for therapeutic conflicts.

Thiopental impairs neutrophil oxidative response by inhibition of intracellular signalling.

BACKGROUND AND OBJECTIVE: Thiopental in clinically relevant concentrations inhibits the oxidative function of neutrophils, whereas only very high, non-therapeutic concentrations of methohexital induce a similar effect. The study characterized the molecular basis of this differential action of oxy- and thiobarbiturates on neutrophils. METHODS: Neutrophils were incubated in vitro with thiopental or methohexital using concentrations within the therapeutic range. Neutrophil responses were induced using different stimuli: N-formyl-L-methionyl-L-leucyl-L-phenylalanine (FMLP), C5a and 1,2-dioctanoyl-sn-glycerol (DiC8-DAG). FMLP and C5a bind to specific G-protein-coupled receptors that share the same second messenger cascade. In contrast, DiC8-DAG, an activator of protein kinase C, bypasses the signal transduction pathway downstream of the receptors. Hydrogen peroxide production by neutrophils was assessed using flow cytometry. To characterize the localization of the interaction site, FMLP receptor expression and cytosolic-free calcium were further analysed. RESULTS: FMLP and C5a-induced hydrogen peroxide production were both significantly impaired by thiopental, but not by methohexital. When postreceptor signalling was bypassed, by stimulation with DiC8-DAG, neither thiopental nor methohexital affected hydrogen peroxide production. Additionally, neither of the barbiturates impaired the cytosolic Ca2+ response. CONCLUSIONS: We conclude that neither protein kinase C nor the hydrogen peroxide-generating enzymes are affected by thiopental or methohexital. The unimpaired Ca2+ response suggests that the function of the receptors and G-proteins were also unimpaired. Taken together, this indicates that the site of action of thiopental is in the cellular signalling upstream of protein kinase C.

Effect of three different doses of urapidil on blood glucose concentrations in the streptozotocin diabetic rat.

BACKGROUND AND OBJECTIVE: Diabetes mellitus associated with hypertension often causes perioperative complications. The alpha1-adrenoceptor antagonist/5-hydroxytryptamine-1A receptor agonist urapidil is an approved drug used in hypertension and hypertensive emergencies. 5-Hydroxytryptamine-1A (5-HT1A) receptor agonists impair glucose metabolism. To evaluate a possible dose-dependent hyperglycaemic effect of urapidil due to its 5-HT1A receptor agonistic properties, the effect of three doses of urapidil on hyperglycaemia in the streptozotocin diabetic rat was investigated. METHODS: Male Wistar-Kyoto rats were made diabetic by streptozotocin and randomly allocated to the following daily treatments for 7 days (n = 6 each): urapidil 6 mg kg(-1), urapidil 20 mg kg(-1), urapidil 60 mg kg(-1), insulin 4 IU kg(-1) subcutaneously. One diabetic group and one non-diabetic healthy group served as controls. RESULTS: Treatment for 7 days with urapidil 20 mg kg(-1) and urapidil 60 mg kg(-1) reduced mean glucose concentrations significantly (urapidil-20: 15.6 +/- 1.1 mmol L(-1), P = 0.023; urapidil-60: 15.8 +/- 0.8 mmol L(-1), P = 0.04) compared with diabetic controls (20.9 +/- 0.8 mmol L(-1)), whereas those after urapidil 6 mg kg(-1) were similar to diabetic controls. Insulin treatment normalized blood glucose concentrations. CONCLUSIONS: The alpha1-adrenoceptor antagonist/5-HT1A receptor agonist urapidil has no hyperglycaemic effect on experimental diabetes mellitus, even in high doses, despite its 5-HT1A receptor agonistic properties.

Lung recruitment maneuver in patients with cerebral injury: effects on intracranial pressure and cerebral metabolism.

OBJECTIVE: To investigate the effects of a lung recruitment maneuver on intracranial pressure (ICP) and cerebral metabolism in patients with acute cerebral injury and respiratory failure. DESIGN: Prospective investigation. SETTING: Ten-bed intensive care unit of a university hospital. PATIENTS: Eleven patients with acute traumatic or non-traumatic cerebral lesions, who were on mechanical ventilation with acute lung injury. INTERVENTIONS: Hemodynamics, ICP, cerebral perfusion pressure (CPP), jugular venous oxygen saturation (SJO(2)), and arterial minus jugular venous lactate content difference (AJDL) were measured before, during and after a volume recruitment maneuver (VRM), which included a 30-s progressive increase in peak pressure up to 60 cmH(2)O and a sustained pressure at the same level for the next 30 s. RESULTS: At the end of VRM, ICP was elevated (16+/-5 mmHg vs 13+/-5 mmHg before VRM, P<0.05) and mean arterial pressure was reduced (75+/-10 vs 86+/-9 mmHg, P<0.01), which resulted in a decrease of CPP (60+/-10 vs 72+/-8 mmHg, P<0.01). SJO(2) deteriorated at the end of the procedure (59+/-7 vs 69+/-6%, P<0.05), AJDL was not altered. In the following period all parameters returned to normal values. An improvement in arterial oxygenation was observed at the end, but not in the period after the maneuver. CONCLUSIONS: Our VRM reduced cerebral hemodynamics and metabolism. We conclude that our VRM with high peak pressure effects only a marginal improvement in oxygenation but causes deterioration of cerebral hemodynamics. We therefore cannot recommend this technique for the ventilatory management of brain-injured patients.

Downregulation of angiotensin II type 1 receptors during sepsis.

Our study aimed to characterize the mechanisms underlying the attenuated cardiovascular responsiveness toward the renin-angiotensin system during sepsis. For this purpose, we determined the effects of experimental Gram-negative and Gram-positive sepsis in rats. We found that sepsis led to a ubiquitous upregulation of NO synthase isoform II expression and to pronounced hypotension. Despite increased plasma renin activity and plasma angiotensin (Ang) II levels, plasma aldosterone concentrations were normal, and the blood pressure response to exogenous Ang II was markedly diminished in septic rats. Mimicking the fall of blood pressure during sepsis by short-term infusion of the NO donor sodium nitroprusside in normal rats did not alter their blood pressure response to exogenous Ang II. Therefore, we considered the possibility of an altered expression of Ang II receptors during sepsis. It turned out that Ang II type 1 receptor expression was markedly downregulated in all organs of septic rats. Further in vitro studies with rat renal mesangial cells showed that NO and a combination of proinflammatory cytokines (interleukin-1beta, tumor necrosis factor-alpha, and interferon-gamma) downregulated Ang II type 1 receptor expression in a synergistic fashion. In summary, our data suggest that sepsis causes a systemic downregulation of Ang II type 1 receptors that is likely mediated by proinflammatory cytokines and NO. We suggest that this downregulation of Ang II type 1 receptors is the main reason for the attenuated responsiveness of blood pressure and of aldosterone formation to Ang II and, therefore, contributes to the characteristic septic shock.

A follow-up study on occupational exposure to inhaled anaesthetics in Eastern European surgeons and circulating nurses.

OBJECTIVE: Although no dose-response relationship exists for the health risks associated with the occupational exposure to inhaled anaesthetics, public health authorities recommend threshold values. The aim of the present study was to assess whether and to what extent these threshold values are exceeded in surgeons and circulating nurses of an Eastern European university hospital, before and after measures had been taken to reduce occupational exposure. METHODS: At nine workplaces, occupational exposure to nitrous oxide and the volatile anaesthetic used (halothane or isoflurane) was measured within the breathing zones of surgeons and circulating nurses by means of photoacoustic infrared spectrometry. The measurements were carried out in 1996 and were repeated in 1997 after the installation of active scavenging devices at five workplaces, and an air-conditioning system at one workplace. RESULTS: Occupational exposure to nitrous oxide and halothane or isoflurane was lower in 1997 compared with that of 1996. In 1996, 89% of the nitrous oxide values were above the European threshold value of 100 ppm, whereas in 1997 approximately 50% were above this limit. In 1996 the majority of the measurements for the volatile anaesthetics were already below 5 ppm halothane and 10 ppm isoflurane and the number of measurements exceeding these limits was further reduced in 1997. CONCLUSION: The measures taken were effective in reducing waste gas exposure. Nevertheless, further efforts are necessary, especially for nitrous oxide, to reach Western European standards and to minimise possible health risks. These efforts comprise the installation of (active) scavenging devices, air-conditioning systems and new anaesthesia machines at all workplaces, the use of low-flow anaesthesia, the replacement of inhaled anaesthetics by intravenous anaesthetics and an appropriate working technique.

[Acute Leriche's syndrome in a patient undergoing coronary artery bypass grafting with extracorporeal circulation]. / Akutes Leriche-Syndrom bei Aorto-Coronarer-Bypass-Operation mit Extrakorporaler Zirculation.

We are reporting a case of an acute thromboembolic obstruction of the aortic bifurcation in a 66-year-old patient undergoing coronary artery bypass grafting with extracorporeal circulation. After declamping of the aorta, the arterial pressure measured in the femoral artery suddenly dropped, whereas the pressure measured in the aortic cannula and in both radial arteries stayed normal. Transoesophageal echocardiography was performed to exclude an acute aortic dissection. While the patient always had a constant sinus rhythm, an angiography following the end of surgery, showed a complete obstruction of the abdominal aorta. Subsequent embolectomy through bifemoral arteriotomies was performed and a histologically fresh embolus (6,5 g in weight) was extracted. Neither the pre- and intraoperative echocardiography, nor the preoperative ventriculography showed signs of an intracardiac thrombus. Insufficient anticoagulation and a lack of inhibitor potential were almost excluded. Considering the histological findings, we assumed that the embolus was formed intraoperatively. Without further complications the patient left our department on the 8th postoperative day.

A new endotoxin adsorber: first clinical application.

In an open, uncontrolled pilot study, 5 men and 1 woman with suspected gram-negative sepsis were treated with a new whole-blood endotoxin adsorption system. Lipopolysaccharide (LPS) adsorption was carried out by hemoperfusion over high-affinity polymethacrylate-bound albumin (Fresenius Endotoxin Adsorber EN 500). All patients suffered from endotoxemia (>20 pg/ml LAL) and met at least two systemic inflammatory response syndrome (SIRS) criteria. Four patients suffered from pneumonia due to mechanical ventilation, one from peritonitis, and one from pneumonia and peritonitis. Endotoxin adsorption was very well tolerated, and efficient LPS removal was shown in all patients. Apache II score immediately before immunoadsorption was 23.5 and was 22.3 after the last treatment. All 6 critically ill patients improved substantially and were discharged from the intensive care unit. LPS whole blood immunoadsorption is a promising new method. No side effects have been observed thus far. A large controlled study to prove clinical efficacy in patients with severe sepsis is under way.

A cytogenetic study on the teaching staff of a polluted school with a questionable increased incidence of malignancies.

Exposure to pollutants, in particular polychlorinated biphenyls (PCB), was established at a school built in 1966. Because of a statistically conspicuous increased frequency of breast cancer observed in the teachers of the school this study was performed to ascertain whether the teachers in the polluted school have an increased level of micronucleated cells (MN) or sister chromatid exchanges (SCE) as an expression of a raised cytogenetic risk. Teachers in a directly adjacent school served as one control group and those from a school about 30 km away as a second one. Each teacher had to answer a questionnaire and after venous blood samples had been taken, the number of MN and SCE in peripheral lymphocytes were determined. For the teachers in the polluted school, in addition, the length of stay in the building during the last month and year was recorded. Thereby no correlation with the number of MN and SCE was proven. In comparison with the two control groups, neither the number of MN nor SCE was increased in the teachers of the polluted school. Even if their predictive value for cancer risk assessment is disputed, MN and SCE have a high rating as standard procedures in the proof of an exposure to genotoxic agents. This study thus does not provide any evidence that, for the teachers in the polluted school, a relevant exposure to genotoxic agents exists.

Occupational exposure to inhaled anaesthetics: a follow-up study on anaesthetists of an eastern European university hospital.

BACKGROUND: Although no dose-response relationship for the health risks associated with the occupational exposure to inhaled anaesthetics exists, public health authorities recommend threshold values. The aim of the present study was to assess if and to what extent these threshold values are exceeded in an eastern European university hospital before and after measures had been taken to reduce occupational exposure. METHODS: At nine workplaces occupational exposure of anaesthetists to nitrous oxide and halothane or isoflurane was measured by means of photoacoustic infrared spectrometry. The measurements were carried out in 1996 and were repeated in 1997 after the installation of active scavenging devices at five workplaces and an air-conditioning system at one workplace. RESULTS: Occupational exposure to nitrous oxide and halothane or isoflurane was lower in 1997 compared to 1996. In 1997 most of the nitrous oxide values still exceeded the threshold value of 100 ppm, whereas most of the halothane and isoflurane values were already below the threshold values of 5 ppm and 10 ppm in 1996. CONCLUSION: The measures taken were effective in reducing waste gas exposure. Nevertheless, further efforts are necessary, especially for nitrous oxide, to reach western European standards. These efforts comprise structural measures such as active scavenging devices and air-conditioning systems at all workplaces, the use of total intravenous anaesthesia, low-flow anaesthesia and an appropriate working technique.

Pharmacokinetics of human cerebral opioid extraction: a comparative study on sufentanil, fentanyl, and alfentanil in a patient after severe head injury.

BACKGROUND: The pharmacodynamic differences in time to onset and dissipation of effect of sufentanil, fentanyl, and alfentanil probably result from different rates of blood-brain equilibration. The authors investigated this hypothesis in humans. METHODS: After simultaneous central venous bolus application of sufentanil (10 microg), fentanyl (100 microg), and alfentanil (1,000 microg), arterial and jugular bulb blood samples were drawn simultaneously at 20, 30, 45, 60, 75, 90, 105, 120, 140, 160, 180, 210, 240, 300, 360, and 420 s from 19 patients during the postacute stage of head injury with normal intracranial pressure, cerebral perfusion pressure, and cerebral oxygen metabolism during normocapnia. RESULTS: Peak brain concentration, indicated by equilibrium between arterial and jugular bulb opioid concentrations, was achieved for alfentanil at 45 s, for sufentanil at 5 min, and for fentanyl at 6 min. The corresponding median time intervals (fifth and ninety-fifth percentiles) to reach 50% of peak brain concentration were 15 (14-18), 25 (18-38) and 35 (25-45) s, respectively. Uptake was highest 20 s after bolus and decreased continuously for fentanyl and sufentanil, whereas alfentanil uptake was biphasic. The ratio of the relative amounts of sufentanil, fentanyl, and alfentanil retained in the brain at peak brain concentration was 1x:x6x:x90. CONCLUSIONS: The differences in the time lag between changes in serum concentrations and drug effect after bolus application of nearly equipotent doses of sufentanil, fentanyl, and alfentanil originate from the different times required to reach blood-brain equilibration, mainly depending on different levels and different time profiles of arterial blood concentrations caused by the different tissue distribution volumes.

[Head-brain injury and cerebral hypoxia. Diagnosis--monitoring--therapy]. / Schädelhirntrauma und zerebrale Hypoxie. Diagnostik-Monitoring-Therapie.

The main reason for posttraumatic secondary brain damage is cerebral hypoxia. Both, severity and duration of hypoxia are crucial in determining wether irreversible cerebral infarction will occur or not. For the clinical routine, the diagnosis of hypoxia is indirectly made by low CPP, low jugular-venous oxygen saturation (SjO2) or low tissue PO2. To minimize misleading false negative SjO2, the CT-Approach for the side of monitoring and calculation of arterial-jugular-venous lactate content for detection of anaerobic metabolism is recommended. Targeted treatment of hypoxia according to the underlying cause is mandatory. Primary goal is to increase cellular oxygen delivery by correction of low arterial oxygen content and elevation of regional CBF. Within the autoregulatory range decreasing CPP causes vasodilation and increasing CPP vasoconstriction with increasing or decreasing cerebral blood volume respectively. Initially elevation of the lower autoregulatory threshold often requires CPP 70 mmHg. Targeted treatment of intracranial hypertension must avoid decreasing CPP. In the early posttraumatic phase prevention of cerebral hypoxia relies on management of CBF by means of CPP and cerebral vascular resistance. Thereafter targeted treatment of intracranial hypertension caused by cerebral edema and hypervolemia are increasingly important.