Effect of adenosine on the expression of beta(2) integrins and L-selectin of human polymorphonuclear leukocytes in vitro

Adenosine has been shown to inhibit the adhesion of polymorphonuclear leukocytes (PMNL) to the vascular endothelium. Because the underlying molecular mechanisms have not been fully understood, the present study characterizes the effect of adenosine on the expression of adhesion molecules of human PMNL. When PMNL were activated by N-formyl-methionyl-leucyl-phenylalanine the number of cell surface beta2 integrins increased fivefold, whereas L-selectin molecules were completely shed. Activation-dependent numerical up-regulation Of beta2 integrins and shedding of L-selectin were inhibited by exogenously applied adenosine receptor agonists in a concentration-dependent fashion. The rank order of potencies of adenosine receptor agonists, measured by the agonists' half-maximal inhibitory concentrations, revealed that adenosine inhibited the numerical up-regulation of beta2 integrins and shedding of L-selectin most likely via an A2(a) receptor site. When extracellular concentrations of endogenously formed adenosine were enhanced by the nucleoside uptake inhibitor dipyridamole, up-regulation of beta2 integrins, and shedding of L-selectin was again inhibited. Both effects were reversed by the enzyme adenosine deaminase, which degrades active adenosine to inactive inosine, suggesting that endogenously formed adenosine may play an important role in the regulation of beta2 integrins and L-selectin of human PMNL.

[Venovenous extracorporeal membrane oxygenation (ECMO) with a heparin-lock bypass system. An effective addition in the treatment of acute respiratory failure (ARDS)]

Mortality of severe acute respiratory distress syndrome (ARDS) in Germany is about 60%. Respiratory therapy can make the lung injury worse by high positive airway pressures, high tidal volumes and high inspiratory oxygen concentrations. Extracorporeal membrane oxygenation (ECMO) was employed to reduce aggressive mechanical ventilation, but it has not been proved to be superior to conventional ventilation. However, encouraged by recently developed improvements in the technique and concept of ECMO, we introduced this therapy into our program for the treatment of ARDS. PATIENTS AND METHODS. All patients with severe ARDS (lung injury score > 2.5) admitted to our multidisciplinary intensive care unit from March 1992 to March 1995 were evaluated prospectively. After admission, the patients first underwent a conventional therapeutic approach, including pressure-controlled inverse-ratio ventilation, permissive hypercapnia, changes in body position (in particular, the prone position), negative fluid balance, anti-biotics, and low-dose hydrocortisone infusion. ECMO via a covalently heparin-coated, venovenous bypass-system with a vortex pump and two membrane lungs was performed if ARDS did not improve after 24-96 h of conventional therapy and if two of three of the slow-entry criteria for ECMO were fulfilled: (1) PaO2/FiO2 < 150 mmHg at PEEP > 5 mbar; (2) semistatic compliance < 30 ml/mbar; (3) right-left shunt > 30%. Only in cases of life-threatening hypoxemia (PaO2 < 50 mmHg at FiO2 1.0 and PEEP > 5 mbar for > 2 h (fast-entry criteria) was ECMO instituted immediately. RESULTS. Sixty patients fulfilled the entry criteria for our study. Thirty-nine patients were treated with a conventional protocol, 37 after improvement of ARDS and 2 who had not improved but in whom there were contraindications to the use of ECMO. ECMO was performed in 10 patients who had not improved, but who fulfilled the slow-entry criteria and in 11 primarily hypoxemic patients who fulfilled the fast-entry criteria. The survival rate was 30/39 (77%) for the conventional therapy group, 6/10 (60%) for the slow-entry group, and 11/11 (100%) for the fast-entry group. The onset of ECMO allowed a significant decrease in peak and mean airway pressures, tidal volume, ventilatory rate, minute volume and inspiratory oxygen concentration. Sufficient gas exchange was provided, and pulmonary artery pressures significantly decreased on bypass. The most frequent complications on bypass were pneumothorax (15/21 patients) and bleeding (7/21 patients). CONCLUSION. In comparison with the historical results at our own institution, the present study demonstrates an improvement in the survival rate from 56% to 78% since ECMO has become available. We conclude that venovenous ECMO with a heparin-bonded bypass circuit is an effective additional option for the treatment of patients with severe ARDS.

[Serum protein binding of fentanyl. The effect of postoperative acute phase reaction with elevated alpha 1-acid glycoprotein and methodologic problems in determination by equilibrium dialysis]

Numerous basic drugs are extensively bound to alpha 1-acid glycoprotein. Fentanyl, with a pKa value of 8.43, is also a basic drug. Protein binding studies have yielded contradictory results concerning binding of fentanyl to alpha 1-acid glycoprotein. In this study we investigated time courses of serum protein concentrations and serum protein binding of fentanyl during postoperative acute phase reaction, assuming that an increase of alpha 1-acid glycoprotein is accompanied by an increase of serum protein binding, if fentanyl is extensively bound to alpha 1-acid glycoprotein. Fentanyl protein binding measurements using equilibrium dialysis can be affected by volume shifts and pH changes. Therefore, volume shifts from buffer to serum and the influence of various phosphate buffers on increasing pH due to loss of CO2 were also evaluated. METHODS. Thirteen patients with no history of renal or hepatic disease undergoing an operation with a significant acute phase reaction were studied. Preoperatively and on the first 3 postoperative days serum concentrations of alpha 1-acid glycoprotein, albumin, total protein and apolipoprotein A and B were determined by rocket immunoeolectrophoresis, biuret method and laser nephelometry, respectively. Corresponding serum protein binding of fentanyl was measured by adding 40 ng of fentanyl to 1 ml serum followed by equilibrium dialysis at 37 degrees C for 4 h. A 0.167 M phosphate buffer (pH 7.27), which gave a final pH of 7.40, was used. Volume shifts from buffer to serum were measured. Fentanyl concentration in serum before dialysis (FS) was determined by gas chromatography, and fentanyl concentration in buffer after dialysis (FB) was determined by radioimmunoassay. Serum protein binding (SPB) was calculated by the formula: SPB = (FS - FB - FB*c)/(FS - FB) where c is a correction factor. Ten randomly selected patient sera were dialyzed against four phosphate buffers of different pH values and molarities, and the serum pH at the end of equilibrium dialysis was measured. RESULTS. Postoperatively, the serum concentration of alpha 1-acid glycoprotein rose to 151% of the control value. In contrast, serum protein binding of fentanyl did not change significantly, with a slight decrease to 96% of control value. There was a significant decrease in serum concentrations of albumin (3rd postoperative day), total protein (2nd postoperative day) and apolipoprotein B (1st-3rd postoperative day) to 85%, 90% and 75% of control values, respectively. Changes in apolipoprotein A concentration were not significant. Protein binding of fentanyl did not correlate with alpha 1-acid glycoprotein and apolipoprotein A, but there was a positive linear relationship between protein binding of fentanyl and albumin, total protein and apolipoprotein B. At the end of equilibrium dialysis the mean volumes of the serum and buffer compartments were 1114 +/- 72 and 834 +/- 68 microliters, respectively. The two phosphate buffers, with pH 7.30 (0.15 M) and pH 7.27 (0.167 M), gave final serum pH of 7.42 and 7.40, respectively. CONCLUSIONS. Present findings suggest that in contrast to other basic drugs, fentanyl binding to alpha 1-acid glycoprotein is of minor importance. In agreement with the findings of former studies, protein binding of fentanyl depended on albumin, total protein and apolipoprotein B concentrations. Due to unspecific binding of fentanyl by hydrophobic interactions, a major role of albumin, which amounts to about 60% of total protein, seems to be evident. Determining fentanyl protein binding by equilibrium dialysis, volume shifts must be taken into account if calculation is based on fentanyl concentrations in plasma (serum) and buffer after dialysis, and an appropriate buffer must be used.

[A comparative study of intravenous opioid analgesia. Sufentanil and alfentanil for extracorporeal shock-wave lithotripsy in urologic patients]

Extracorporeal shock-wave lithotripsy (ESWL) is the method of choice for the treatment of solitary stones in the kidney or ureter. Early lithotripters required prolonged immobility of the patient and caused considerable pain, necessitating general or epidural anaesthesia during the procedure. Modern lithotripters are quicker, but still require analgesia. Intravenous opioids are currently the drugs in favour. The opioids most commonly used are fentanyl and its shorter-acting analogue, alfentanil. The latter has a more rapid onset and, because of its reduced lipid solubility, is less cumulative. Sufentanil is a new opioid that is also of the phenylpiperidone group and has been recently licensed and introduced in Germany. Its pharmacokinetic and pharmacodynamic properties suggest an intermediate duration of action, high analgesic potency, and cardiovascular stability with diminished respiratory depression. In this prospective double-blind study, the effects of alfentanil and sufentanil on cardiovascular and respiratory parameters, the quality of analgesia, degree of sedation and the number and type of side-effects were compared.

PATIENTS AND METHODS

After giving informed consent and with the approval of the hospital ethics committee, 62 patients (ASA I or II) were investigated. They were randomly allocated to two groups, either receiving sufentanil (n = 32) or alfentanil (n = 30) during ESWL. No premedication was given. Excluded were patients with pain prior to treatment, patients treated with a spasmolytic or analgesic drug and those who had undergone ESWL within the last 6 months. The loading dose was given as a 5-min infusion to each group. The heart rate, systolic and diastolic blood pressure, percutaneous oxygen saturation (SpO2), and the transcutaneous capillary carbon dioxide tension (PicCO2) were recorded prior to the procedure (i.e. before administration of opioid), after 1000 and after 2000 shock waves and then 1 and 2 h after the end of lithotripsy. After 1000 and 2000 shock waves, and 1 an 2 h after the treatment, the patients were asked to express their degree of tiredness and pain on a visual analogue scale (VAS). The occurrence of side-effects such as nausea, vomiting, pruritus or other unpleasant sensations were noted by an anaesthesia nurse. Simultaneously, the anaesthetist recorded his/her impression of the patient's tiredness and degree of pain, both by using the VAS. He was not allowed to question the patient, nor was he aware of the patient's own scores. At the end of the observation period both the patient and the anaesthetist related their overall satisfaction with the anaesthetic procedure, again by using the VAS. Data were analysed with the Mann-Whitney-U for comparisons between groups and with the Wilcoxon test within each group. The side-effects were analysed with the Chi-square test.

RESULTS

The systolic and diastolic blood pressure remained stable in both groups during and after treatment. The mean heart rate was different between the two groups at the beginning, and after the end of the treatment it dropped in both groups, but no significant difference was seen between groups. The PicCO2 rose from an initial mean of 36.8 mm Hg to a maximum of 44.6 mm Hg after 1000 shock waves in the sufentanil group, and from 37.8 mm Hg to 46.0 mm Hg after 2000 shock waves in the alfentanil group. The differences were significant within groups until 1 h after the end of the treatment, but there was no significant difference between groups. The oxygen saturation SpO2 dropped slightly in both groups. The differences were not significant between groups. In the alfentanil group, one patient had a maximum carbon dioxide tension of 83 mm Hg after 2000 shock waves, whereas in the sufentanil treated group the oxygen saturation fell to 72% in one case. (ABSTRACT TRUNCATED)

A deletion in the alpha subunit locks platelet integrin alpha IIb beta 3 into a high affinity state

The integrin alpha IIb beta 3 (GPIIb/IIIa) mediates platelet aggregation by a change in affinity for the ligand fibrinogen. The amino acids 991-995 (GFFKR) at the NH2-terminus of the cytoplasmic domain are highly conserved in all known integrin alpha subunits. We postulated that the GFFKR-region is important for the inside-out signal transduction and has an influence on the affinity state of integrins. To test this hypothesis, a mutant with a deletion in the GFFKR region was designed. The DNA-constructs were constructed by PCR, sequenced, cotransfected with the beta 3 subunit into CHO cells and cell surface expression was proven with immunoprecipitation and flow cytometry. The GFFKR-deletion mutant demonstrated a high affinity binding of the mAb PAC-1 and I125-labeled fibrinogen. The metabolic inhibitors 2-deoxyglucose and NaN3 did not change the affinity state of the deleted receptor. Neither did the truncation of the cytoplasmic domain of the beta 3 subunit. Additionally, expression of the deleted integrin in the erythropoetic cell line K562 revealed a high affinity state. A deletion of the GFFKR-region in the cytoplasmic domain of the alpha subunit locks integrin alpha IIb beta 3 in a high affinity state. This is an intrinsic property of the deleted receptor since there is no energy dependence and no cell type specifity. Thus, the GFFKR-region is involved in inside-out signaling in alpha IIb beta 3. Furthermore, cell lines expressing this activated alpha IIb beta 3 integrin may be used as models for activated platelets.

Time discrete, near infrared photoplethysmography (NIRP) for non-invasive investigation of the volume pulse in man

In pulse oximetry the principles of photoplethysmography are used for determination of heart rate and in some devices to also display the volume pulse. It has been suggested, that a more detailed analysis of the signal may allow quantitative analysis of peripheral hemodynamic events. We describe a new computer assisted time discrete analysis of the volume pulse, studying its reliability and the method s fundamental assumption of a linear relationship between changes in amplitude and changes in time sequences of the volume pulse.

METHOD

In a finger clip two diodes emit near infrared (840 nm, NIR) and red light (640nm, RED) into the finger tip, where it is remitted mainly by the erythrocytes. 70 sec of recorded signal is filtered and the resulting volume pulse analysed off-line using a computer. On each volume pulse the time of the first (Tmax), the second maximum (time of dicrote, Td) and the duration of the volume pulse (Tp) are measured and the mean values displayed. In addition, the fundamental arterial oscillation Tag = Td - Tmax and all the above values in relation to Tp are calculated. Using NIRP, 54 healthy young volunteers (19 female, mean age 27.0 +/- 3.4 years) were studied and the individual mean values calculated from 960 measurements. The reliability during 10 repetitive measurements was investigated in 26 of the 54 volunteers. In 12 subjects 5 repetitive measurements were obtained from each finger and compared with each other. In 11 subjects the linear relationship between amplitude and time sequence was tested on > 30 000 single volume pulses. The finger clip photoelectrode was levelled with the right atrium in all measurements, skin close to the clip and room temperature were recorded.

RESULTS

From the mean individual values the following time discrete values were calculated for the NIR signal (n = 41): Tp = 882.3 +/- 142.6 ms, Tmax = 214.8 +/- 28.3 ms, Td = 452.7 +/- 32.4 ms, Tdec = 667.4 +/- 133.6 ms, Tag = 237.9 +/- 36.3 ms, Tmax/Tdec = 0.34 +/- 0. 07, Td/Tdec = 0.7 +/- 0.11. For each parameter the individual standard deviation during 10 repetitive measurements (26 subjects) ranged between 2.2 and 6.1%. The time sequences found were not significantly different between the individual fingers. A linear relationship between changes in time sequence and changes in amplitude was found in all tested subjects (mean r = 0.96).

CONCLUSION

These results show, that the values obtained with time discrete NIRP are highly reproducible and show an individual SD of less than 6.5% under steady state conditions. The linear relationship between time sequence and amplitude found in the present study has to be confirmed in further studies on patients with pathologies of the macro- and microcirculation.

Quantification of zidovudine and individual zidovudine phosphates in peripheral blood mononuclear cells by a combined isocratic high performance liquid chromatography radioimmunoassay method

Zidovudine (ZDV, AZT) is the first clinically effective drug licensed for use in the treatment of human immunodeficiency virus (HIV) infection. Activation of ZDV requires phosphorylation to ZDV triphosphate by cellular kinases. It is important, therefore, to determine the intracellular levels of the active form because measurement of ZDV concentrations in plasma have not reflected any direct relationship with activity or toxicity. In this paper a validated assay for the measurement of both ZDV and its three phosphorylated anabolites, ZDV mono-, di- and triphosphate, in peripheral blood mononuclear cells (PBMCs) is described. The method consisted of a combination of isocratic high performance liquid chromatography (HPLC) separation and radioimmunoassay (RIA). The PBMCs were separated from whole blood and ZDV and ZDV nucleotides were extracted and separated by isocratic elution with an ion-pairing mobile phase on a reversed-phase HPLC column. The collected ZDV and individual ZDV nucleotide fractions were dephosphorylated to ZDV, cleaned by solid phase extraction and assayed by a commercially available RIA kit. The assay developed was successfully used to determine intracellular ZDV and anabolite concentrations of 10 PBMC samples taken from HIV positive patients on ZDV treatment.

[Fluoride-induced nephrotoxicity: factor fiction?]

In the 1960s, the widespread use of the inhalational anaesthetic methoxyflurane was associated with a significant occurrence of postoperative renal dysfunction. This was attributed to hepatic biotransformation of methoxyflurane and subsequent release of inorganic fluoride ions into the circulation. Based upon the clinical experience with methoxyflurane, serum fluoride concentrations exceeding 50 mumol/l were considered to be nephrotoxic. Without further reevaluation, this 50 mumol/l threshold was subsequently applied to other fluorinated anaesthetics as well. Enflurane and even isoflurane may, when used during prolonged operations, also yield anorganic fluoride levels in excess of 50 mumol/l. Nevertheless, no cases of renal dysfunction attributable to prolonged use of these anesthetics have been reported. About 4% of the new inhalational anaesthetic sevoflurane is metabolized, and fluoride concentrations exceeding those after enflurane are frequently measured. Numerous studies have examined the nephrotoxic potential of sevoflurane degradation products. However, fluoride-related toxicity has been observed neither in animal nor in clinical studies, including prolonged administration and patients with pre-existing renal disease. New insights into the intrarenal metabolisation of volatile anaesthetics may well explain the absence of nephrotoxicity after sevoflurane. The threshold for fluoride nephrotoxicity of 50 mumol/l, still given in many medical text-books, can no longer be applied as an indicator of nephrotoxicity after isoflurane, enflurane or sevoflurane. Therefore, the elevated serum fluoride concentrations consistently recorded following anaesthesia with sevoflurane are devoid of clinical significance.

[The role of polymorphonuclear neutrophilic leukocytes in the pathogenesis of acute respiratory distress syndrome (ARDS)]

Polymorphonuclear leukocytes (PM-NL) constitute the first line of defence in the protection of the host from invading microorganisms. PMNL also contribute to the removal of cellular debris from necrotic tissues during reparative processes. For these purposes PMNL are armed with highly efficient bactericidal mechanisms which, under certain pathophysiological conditions, can be turned against the host himself. A vast body of evidence indicates that PMNL are able to cause lung injury which may be followed by the development of acute respiratory distress syndrome (ARDS). Accordingly, in patients with ARDS blood concentrations of inflammatory activators of PMNL are elevated, cytotoxic mechanisms of PMNL are enhanced and sequestration of these cells has been demonstrated to be inversely proportional to gas exchange. The manifestation of ARDS in leukopenic patients, however, indicates the development of this clinical syndrome independently of the presence of PMNL. The ability to differentiate between PMNL-dependent and PMNL-independent pathways in the pathogenesis of this syndrome is not only of theoretical interest but also of therapeutic significance. Since the patient's systemic inflammatory response may vary according to the stage and type of the underlying disease, an exact qualitative and quantitative analysis of PMNL functions may provide the rationale for new anti-inflammatory drug regimens aimed at modifying the host's response without increasing the risk of infection.

Midlatency auditory evoked potentials during anaesthesia with increasing endexpiratory concentrations of desflurane

BACKGROUND

Under general anaesthesia with the volatile anaesthetics halothane, enflurane and isoflurane, midlatency auditory evoked potentials (MLAEP) are suppressed dose-dependently. Therefore, MLAEP have been used to measure depth of anaesthesia and to indicate intraoperative awareness. Desflurane is a new volatile anaesthetic and its effect on MLAEP have not been studied previously.

METHODS

We have studied MLAEP during general anaesthesia with increasing endexpiratory concentrations of desflurane in 12 patients scheduled for elective gynaecological surgery. Auditory evoked potentials were recorded in the awake state and during anaesthesia with endexpiratory steady state concentrations of 1.5, 3.0, 4.5 and 6.0 vol % of desflurane on vertex (positive) and mastoids on both sides (negative). Latencies of the peaks V, Na, Pa, Nb, Pl (ms) and amplitudes Na/Pa, Pa/Nb and Nb/Pl (micro V) were measured.

RESULTS

In the awake state, MLAEP had high peak-to-peak amplitudes and a periodic waveform. During general anaesthesia with increasing endexpiratory concentration of desflurane, the latency of the brainstem response V increased only slightly. In contrast, MLAEP showed a marked dose-dependent and statistically significant increase in latencies of Na, Pa, Nb and Pl and decrease in amplitudes of Na/Pa, Pa/Nb and Nb/Pl. Under 6.0 vol % of desflurane MLAEP were severely attenuated or even abolished.

CONCLUSION

Based on these observations, endexpiratory concentrations of > or = 4.5 vol % desflurane should suppress awareness phenomena such as auditory perceptions during anaesthesia.

[Awakening from anesthesia and recovery of cognitive function after desflurane or isoflurane]

Desflurane is a new volatile anaesthetic with an extremely low blood/gas partition coefficient of 0.42. This should provide a rapid recovery from anaesthesia.

METHODS

We studied 100 adult patients, ASA class I or II, undergoing elective orthopaedic surgery randomly assigned to anaesthesia with desflurane (n = 50) or isoflurane (n = 50) supplemented by nitrous oxide in oxygen. Clorazepat was given for premedication, fentanyl and thiopental for induction of anaesthesia, followed by maintenance with desflurane or isoflurane as clinically appropriate. Emergence from anaesthesia was measured as well as return of cognitive functions (extended Aldrete score, digit symbol substitution test, and visual analogue scales [VAS]).

RESULTS

While the demographic characteristics and administrated doses of fentanyl and thiopental were comparable, the recovery profiles in both groups were different. After discontinuation of the volatile anaesthetics, times to extubation and ability to follow simple commands were significantly shorter after desflurane than after isoflurane. Extended Aldrete scores, estimation of the patients' physical condition, results of the digit symbol substitution test, measuring cognitive functions, and rates of drowsiness and weakness on VAS showed better recovery with less impairment of cognitive function in the desflurane group than in isoflurane patients even 120 min after anaesthesia. VAS pain scores and doses of analgesic drugs given within the first 2 postoperative hours, however, showed no significant differences. Desflurane patients were also judged fit for discharge from the recovery room significantly faster.

CONCLUSIONS

Our results demonstrate that desflurane anaesthesia, even when supplemented by premedication, intraoperative opioids, and nitrous oxide may offer clinical advantages over isoflurane as far as the post-anaesthetic recovery profile is concerned.

[Intraoperative awareness and auditory evoked potentials]

Midlatency auditory evoked potentials (MLAEP) are suppressed dose-dependently during anaesthesia with a variety of general anaesthetics. Therefore, MLAEP have been proposed to measure depth of anaesthesia and to indicate intraoperative awareness. Several studies give evidence of a close relationship between MLAEP and motor signs of wakefulness, intraoperative awareness, and explicit and implicit memory functions during general anaesthesia. Summarising these data, one may conclude that there is a close hierarchical relation between cognitive function, memory and wakefulness during anaesthesia, and MLAEP latencies. A short Nb latency below 45 ms is consistent with conscious awareness and unimpaired memory function with explicit recall and adequate response to commands. When Nb latency increases to 45-50 ms, it may be associated with conscious awareness. Patients still respond to commands, but memory formation is impaired and explicit recall is lost. A further increase of Nb latencies seems to be consistent with unconscious awareness, characterised by implicit memory of intraoperative events; 60 ms seems to be the threshold value for motor signs of wakefulness during anaesthesia. With a further increase of MLAEP latency during anaesthesia, conscious awareness and memory formation, explicit and implicit recall, response to commands, and spontaneous purposeful movements during anaesthesia are blocked. The new volatile anaesthetic sevoflurane leads to a dose-dependent increase in MLAEP peak latencies and a decrease in MLAEP amplitudes. At about 1.5 vol.% end-expiratory sevoflurane concentration, MLAEP are significantly suppressed and Nb latency is in the range of 68-80 ms. Therefore, from the present data and those from the literature, one may expect that sevoflurane at concentrations greater than 1.5 vol.% for general anaesthesia would be able to suppress awareness phenomena such as purposeful movements, auditory perception, intraoperative wakefulness and awareness, memory formation, and explicit and implicit recall of intraoperative events.

Enteral versus parenteral nutrition: effects on gastrointestinal function and metabolism

The effects of total parenteral nutrition (TPN) versus enteral nutrition (TEN) were studied in 34 patients following major neurosurgery. Measurements were made of resting energy expenditure (REE), urea production rate (UPR), visceral proteins, parameters of liver and pancreas function, as well as gastrointestinal absorption. To predict nutritional status, nutritional index (NI) was calculated. UPR revealed no significant differences between the groups. After 12 days of TEN, however, synthesis of visceral proteins increased significantly. In addition, NI improved after TEN (p < 0.05), whereas it remained unchanged after TPN. Thrombocyte and lymphocyte counts rose predominately during enteral nutrition. Only in the TEN group was REE increased by 18% and Glasgow Coma Scale (GCS) enhanced from Day 6 on. Exogenous insulin demand was enhanced in the parenterally fed group, and bilirubin (p < 0.05), amylase (p < 0.05), and lipase (p < 0.01) rose significantly, as did gamma-glutamyl-transferase (p < 0.0005) and alkaline phosphatase (p < 0.0005). After 12 d of TPN, vitamin A absorption was significantly attenuated, indicating reduced fat absorption compared to TEN. Carbohydrate absorption did not show significant changes between the groups. Only during TPN did mean values of xylose absorption remain below the normal range. Therefore, enteral nutrition following neurosurgical procedures is associated with an accelerated normalization of nutritional status and an improved substrate tolerance. TEN opposes early postoperative absorption disturbances of the small intestine.

Perioperative mucosal pH and splanchnic endotoxin concentration in orthotopic liver transplantation

Although impairment of splanchnic perfusion may induce mucosal hypoxia and endotoxaemia during orthotopic liver transplantation (OLT), little is known about the changes in mucosal oxygenation during and after the procedure. To study the effects of liver surgery itself on mucosal pH (pHi) and the response of pHi to acute changes in portal flow, we measured gastric pHi during six liver resections using tonometry: in two patients, after clamping of the hepatoduodenal ligament, pHi decreased within 30 min and recovered promptly after reperfusion. We then investigated gastric and sigmoid pHi (pHig, pHis) during the perioperative phase in 18 OLT. Median pHi values were low before surgery (pHig 7.28 (first/third quartiles 7.22/7.34); pHis 7.27 (7.12/7.36)). Although global oxygen delivery and haemodynamic variables remained constant and veno-venous bypass (VVB) was used to maintain portal flow, pHi declined during the anhepatic phase (pHig 7.19 (7.13/7.23), P < 0.01; pHis 7.13 (7.06/7.24), P < 0.05). After reperfusion of the graft, pHi recovered and did not differ from baseline values by the end of OLT. After operation pHig increased further, reaching the highest values 30 h after ICU admission (7.34 (7.26/7.38)). In the intraoperative period, no significant endotoxaemia was observed either in portal or systemic blood. The maximum reduction in pHi was related neither to the duration of VVB and OLT nor to the number of red cell units transfused. pHi after reperfusion did not correlate with graft viability or dysfunction of the lung or kidney. We conclude that pHi indicates mucosal ischaemia during OLT which is not necessarily associated with endotoxaemia, and intraoperative pHi monitoring does not appear to be a valuable predictor of postoperative graft failure and organ dysfunction.

Thermodilution cardiac output may be incorrect in patients on venovenous extracorporeal lung assist

Cardiac output measurement is part of routine monitoring in critically ill patients. In patients on extracorporeal lung assist, thermodilution cardiac output measurement may lead to erroneous results caused by indicator loss into the extracorporeal circuit. Seven patients on venovenous extracorporeal lung assist were studied using different extracorporeal blood flows. We compared conventional thermodilution cardiac output determinations with dye dilution cardiac output measurement, with dye injection into the pulmonary artery. The latter method is not affected by the extracorporeal circuit. The conventional thermodilution method overestimated cardiac output up to a maximum of 300%, providing results up to 10 L/min higher than true cardiac output. The mean difference between thermodilution and true cardiac output as determined by dye dilution with pulmonary artery indicator injection was 3.0 +/- 2.41 L/min. There was no correlation between thermodilution cardiac output values and true cardiac output (r = 0.06). We conclude that conventional thermodilution is not a suitable method for cardiac output measurement in patients on extracorporeal lung assist, especially if high extracorporeal blood flows are applied.

[Awareness during general anesthesia. Definition, incidence, clinical relevance, causes, avoidance and medicolegal aspects]

The possibility that a patient during general anaesthesia is aware of the operation going on and aware of severe pain that might be remembered postoperatively must be very alarming to patients and anaesthetists alike. Furthermore, there is experimental evidence showing that conscious recall of intraoperative events is only the tip of an iceberg; it seems very probable that there is even a higher incidence of unconscious perception during general anaesthesia. Therefore, the following stages of intraoperative awareness must be distinguished: (1) conscious awareness with explicit recall and with severe pain; (2) conscious awareness with explicit recall but no complaints of pains; (3) conscious awareness without explicit recall and possible implicit recall; (4) subconscious awareness without explicit recall and possible implicit recall; (5) no awareness. The incidence of conscious awareness with explicit recall and severe pain has been estimated at less frequent than 1/3000 general anaesthetics. Conscious awareness with explicit recall but no complaints of pain has been reported in the literature with an incidence of 05-2%. With 7-72%, conscious awareness without explicit recall and possible implicit recall shows a very wide range of variation and its occurrence probably depends on the anaesthetic drugs used. Subconscious awareness with possible implicit recall has an incidence of up to 80%, but there are many methodological problems in demonstrating implicit memory of intraoperative events. Reports of intraoperative awareness do not come exclusively from cardiac surgery and obstetrics, but also from all other operative specialties. Postoperatively, patients who experience intraoperative awareness may develop a so-called post-traumatic stress syndrome. Symptoms involve re-experiencing the event awake or in dreams, sleep disturbances, depression, avoidance of stimuli associated with the event. The probability of the development of the post-traumatic stress syndrome seems to coincide with the experience of severe pain. When a patient complains of intraoperative awareness postoperatively the anaesthesiologist should discuss the event frankly with the patient. When the symptoms of the post-traumatic stress syndrome persist a psychotherapy should follow. Causes for intraoperative awareness may be: equipment failure, too-light anaesthesia, e.g. for a caesarean section or for emergency surgery in severely injured or polytraumatized patients, during cardiac surgery, bronchoscopy of difficult intubation. There is interindividual variability in anaesthetic effect; for example, chronic drug or alcohol abuse or overweight may make increased anaesthetic doses necessary. They are at risk for intraoperative awareness. Some general anaesthetics or anaesthetic procedures, e.g. the combination of a relaxant and N2O, opioid mono-anaesthetics, or opioids combined with benzodiazepines, seem to involve a higher risk of intraoperative awareness than do volatile anaesthetics. The bases of litigation are medical malpractice, breach of contract by the anaesthesiologist or lack of informed consent from the patient. Therefore, patients who are at risk of intraoperative awareness should be given detailed information on this special risk before the operation.

Inhalation anaesthesia at the extremes of age: geriatric anaesthesia

No single anaesthetic technique is superior for all elderly patients, although the prognosis is improved if minor surgical procedures are performed with local anaesthesia rather than with general or major regional anaesthesia. If general anaesthesia is required, which specific inhalation anaesthetic can improve the prognosis of the geriatric patient? The low solubility of desflurane and its resistance to biodegradation would seem to recommend its use in the geriatric patient. However, these theoretical advantages remain to be adequately documented.