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Description / Table of Contents: Abstract Post-dural puncture headache (PDPH) is a significant complication of spinal anaesthesia. Diameter and tip of the needle as well as the patient′s age have been proven to be important determinants. The question of whether post-operative recumbency can reduce the risk of PDPH has not been answered uniformly. And besides, some studies referring to this subject reveal methodical failures, for example, as to clear definition and exact documentation of post-operative immobilization. Furthermore, fine-gauge needles (26G or more) have not been investigated yet. The first aim of our study was therefore to examine the role of recumbency in the prevention of PDPH under controlled conditions using thin needles. Secondly, we wanted to confirm the reported prophylactic effect of needles with a modified, atraumatic tip (Whitacre and Atraucan) by comparing them to Quincke needles of identical diameter. Most of the former investigators compared Quincke with atraumatic needles of different size regardless of the known influence of the diameter on PDPH. Patients and methods: In a prospective study we included 481 consecutive patients undergoing a total of 500 orthopaedic operations under spinal anaesthesia. The latter was performed in a standardized manner (patient sitting, midline approach, needle with parallel bevel direction), using four different needles allocated randomly (26-gauge and 27-gauge needles with Quincke tip, 26-gauge Atraucan and 27-gauge Whitacre cannula). Half of the patients were instructed to stay in bed for 24 h (horizontal position without raising head), the others to get up as early as possible. An anaesthesiologist visited the patients on the fourth postoperative day or later and questioned them about headache and duration of recumbency. Additionally, the patients had to fill out a questionnaire 1 week after surgery. Any postural headache was considered as PDPH. Results: The four groups of different needles had homogeneous demographic characteristics (see Table 1). A total of 47 patients (9.4%) developed PDPH. The incidence was highest after puncture with a 26-gauge Quincke cannula (17.6%) with a significant difference compared to the other needles (see Table 2). PDPH incidence correlated well with increasing age and number of dural punctures, but showed no relation to sex, patient´s history of headache or experience of the anaesthesiologist. Only about half of the patients (60.5%) followed the instructions regarding mobilization or recumbency. The duration of strict bed rest did not influence the development of PDPH: The overall incidence was 9.4% in the recumbency group and 8.8% in the group of early ambulation. In all, 45 patients suffered from ordinary not posture-related headache. Conclusions: The significantly higher incidence of PDPH after spinal anaesthesia with 26-gauge Quincke needles compared to the 27-gauge Quincke and the 26-gauge Atraucan group confirmed the importance of both needle diameter and design of its tip. The Atraucan cannula has not been examined in a controlled study (in comparison with Quincke needle of the same diameter) before. In accordance with other investigators we found patient′s age and number of puncture attempts as additional predictors of PDPH. Consequent bed rest, however, was not able to reduce its incidence. Our studies reveal the poor compliance of patients with regard to mobilization/immobilization, a problem which possibly has not been considered enough in former studies examining the influence of bed rest on PDPH. Based on the literature and the present findings, we recommend using thin needles with atraumatic tips for spinal anaesthesia if possible. Recumbency presents an avoidable stress for patients as well as medical staff and should no longer be ordered.

Description / Table of Contents: Abstract During pressure support ventilation (PSV), the timing of the breathing cycle is mainly controlled by the patient. Therefore, the delivered flow pattern during PSV might be better synchronised with the patient's demands than during volume-assisted ventilation. In several modern ventilators, inspiration is terminated when the inspiratory flow decreases to 25% of the initial peak value. However, this timing algorithm might cause premature inspiration termination if the initial peak flow is high. This could result not only in an increased risk of dyssynchronization between the patient and the ventilator, but also in reduced ventilatory support. On the other hand, a decreased peak flow might inappropriately increase the patient's inspiratory effort. The aim of our study was to evaluate the influence of the variation of the initial peak-flow rate during PSV on respiratory pattern and mechanical work of breathing. Patients. Six patients with chronic obstructive pulmonary disease (COPD) and six patients with no or minor nonobstructive lung pathology (control) were studied during PSV with different inspiratory flow rates by variations of the pressurisation time (Evita I, Drägerwerke, Lübeck, Germany). During the study period all patients were in stable circulatory conditions and in the weaning phase. Method. Patients were studied in a 45° semirecumbent position. Using the medium pressurization time (1 s) during PSV the inspiratory pressure was individually adjusted to obtain a tidal volume of about 8 ml/kg body weight. Thereafter, measurements were performed during five pressurization times (〈0.1, 0.5, 1, 1.5, 2 s defined as T 0.1, T 0.5, T 1, T 1.5 and T 2) in random order, while maintaining the pressure support setting at the ventilator. Between each measurement steady-state was attained. Positive end-exspiratory pressure (PEEP) and FIO2 were maintained at prestudy levels and remained constant during the study period. Informed consent was obtained from each patient or his next of kin. The study protocol was approved by the ethics committee of our medical faculty. Gas flow was measured at the proximal end of the endotracheal tube with a pneumotachometer (Fleisch no. 2, Fleisch, Lausanne, Switzerland) and a differential pressure transducer. Tracheal pressure (Paw) was determined in the same position with a second differential pressure transducer (Dr. Fenyves & Gut, Basel, Switzerland). Esophageal pressure (Pes) was obtained by a nasogastric balloon-catheter (Mallinckrodt, Argyle, NY, USA) connected to a further differential pressure transducer of the same type as described above. The balloon was positioned 2–3 cm above the dome of the diaphragm. The correct balloon position was verified by an occlusion test as described elsewhere. The data were sampled after A/D conversion with a frequency of 20 Hz and processed on an IBM-compatible PC. Software for data collection and processing was self-programmed using a commercially available software program (Asyst 4.0, Asyst Software Technologies, Rochester, NY, USA). Patient's inspiratory work of breathing Wpi (mJ/l) was calculated from Pes/volume plots according to the modified Campbell's diagram. Dynamic intrinsic PEEP (PEEPidyn) was obtained from esophageal pressure tracings relative to airway pressure as the deflection in Pes before the initiation of inspiratory flow Patient's additive work of breathing (Wadd) against ventilator system resistance was calculated directly from Paw/V tracings when Paw was lower than the pressure on the compliance curve. Two-way analysis of variance (ANOVA) was used for statistical analysis, followed by post hoc testing of the least significant difference between means for multiple comparisons. Probability values less than 0.05 were considered as significant. Results. COPD patients had significantly higher pressure support than control patients. With decreasing inspiratory flow, Wpi increased significantly in COPD patients. Additionally, the duct cycle (Ti/Ttot) significantly increased with decreased flow rates which resulted in a higher PEEPidyn compared to the baseline. At T 1.5 and T 2 with lower flow rates, the pre-set pressure support level was not achieved within inspiration in the COPD patients. Wadd increased significantly at T 1, T 1.5 and T 2 in COPD patients and at T 1.5 and T 2 in the control group. In one patient, premature termination of inspiration owing to high initial peak flow was corrected by adjustment of the inspiratory flow. Conclusion. Our results demonstrate that a decreased peak flow during PSV resulted in increased patient's work of breathing in COPD patients. During lower flow, the pre-set pressure support level was not attained and additional work had to be done on the ventilator system. Furthermore, the higher PEEPidyn during lower flow rates indicates a higher risk of dynamic pulmonary hyperinflation in patients with COPD. We conclude that the use of pressurization times ≥1 s to decrease inspiratory peak flow during PSV is of no benefit and should be avoided, particularly in COPD patients. However, in selected cases, slight decrease of inappropriately high peak flows might be useful for optimization of PSV setting to avoid premature termination of inspiration.

Description / Table of Contents: Abstract Objective: The aim of this study was to in- vestigate preliminarydose-range effects of clonidine added to ropivacaine for epidural analgesia in elective orthopedic surgery of the lower limbs with doses, causing a minimum of cardiovascular side effects. Methods: 60 patients were randomly assigned to receive in a double-blind fashion a mixture of 1 mg/cm height ropivacaine plus saline or 1 mg/cm ropivacaine plus 25 µg, 50 µg, 75 µg, 100 µg or 150 µg clonidine for epidural analgesia. The sensory and motor function were determined at defined time intervalls for 30 minutes. Heart rate and blood pressure were controlled and sedation score was judged. The postoperative 2-segment-regression of pin-prick and the onset of pain were recorded. Results: The six groups were comparable in demographic datas and in term of onset time. The prolongation of analgesia reached 513 ± 92 min (p = 0,002) for 150 µg clonidine, 460 ± 148 min (p = 0,073) for 100 µg clonidine, 440 ± 86 min (p = 0,057) for 75 µg clonidine compared with 347 ± 114 min for saline. In an equal manner, 2-segment- regression for pin-prick was extended to 251 ± 47 min (p = 0,018) for 150 µg clonidine, 238 ± 33 min (p = 0,034) for 100 µg clonidine, 229 ± 29 min (p = 0,027) for 75 µg clonidine and 178 ± 43 min for saline. Heart rate dropped down in all groups. Mean arterial pressure decreased significantly in the groups with 75, 100 and 150 µg clonidine. Sedation score increased continously from 0,6 ± 0,5 (saline) to 1,8 ± 0,8 (150 µg clonidine). Conclusion: We conclude that 150 µg clonidine significantly enhances the duration of analgesia of epidurally administered ropivacaine in a mean of 171 mg. This time intervall is longer than the one with 200 mg ropi-vacaine alone. But, there are side effects in form of decrease of arterial pressure. Cardiovascular monitoring seems to be essential. Because of the enhanced analgesia duration, the time interval for reloading epidural anaesthesia are increased.

Description / Table of Contents: Abstract Introduction: The influence of kolloids on the immune system is not well documented. In this study we investigated the effects of gelatine, hydroxyethylstarch (HES), human albumine, and dextrane on neutrophil function and receptor expression by flow cytometry. Methods: Whole blood of healthy volunteers was incubated for 30 minutes with either gelatine, HES (6% and 10%), dextrane 40 and 60, or human albumin 20%. Phagocytic capacity was determined by uptake of fluorescein-isothiocyanate labeled bacteria, the conversion of dihydrorhodamine 123 into fluorescent rhodamine 123 was used for oxidative burst measurements. Expression of complement receptors CD 11b and CD35 was investigated using fluorescein-isothiocyanate labeled antibodies. Results: Incubation with gelatine significantly increased expression of complement receptors and oxidative burst. Dextranes and HES had no influence on neutrophil function. Human albumin reduced the oxidative burst, whereas CD 35 expression was increased. Conclusion: The physiological significance of these changes in a range of 10% has to be clarified in further investigations.