[Aventilatory mass flow during apnea : investigations on quantification]. / Aventilatorischer Massenfluss während Apnoe : Untersuchungen zur Quantifizierung.

BACKGROUND: Aventilatory mass flow (AVMF) is routinely used for apneic oxygenation in various clinical procedures but no data exist to quantitatively describe the gas flow. This study was designed to determine the amount of AVMF during the clinical situation of apnea to force spontaneous respiration at the end of anaesthesia with controlled ventilation. MATERIALS AND METHODS: A total of 200 patients undergoing anesthesia for routine surgery were examined. AVMF was analyzed with a high resolution, low gas stream, thermal mass flow analyzer. The intended recording time was 3 min. RESULTS: Measurement was reliably successful and suitable for evaluation in only 23 patients. AVMF-induced gas flow started on average 17.9 + or - 9.4 s after onset of apnea. Maximum flow was reached within 158 + or - 20 s and determined to be 135 + or - 32 ml/min. The slope of increase of gas flow showed a rapid oscillation corresponding to the heart rate in all patients and in 14 out of 23 patients a slow oscillation with a frequency of 8.9 + or - 1.8/min. CONCLUSIONS: During apnea AVMF develops in a non-linear fashion. The maximum flow observed is closely related to the estimated oxygen consumption. Heart rate synchronous flow variations are probably caused by intrathoracic volume variations due to heart action. The low frequency oscillations correspond to the frequency of Traube-Hering-Mayer waves.

[Anesthesia for cesarean section in a patient with Lobstein's syndrome]. / Anästhesie zur Sectio caesarea bei einer Patientin mit Osteogenesis imperfecta.

We report on a 21-year-old woman with a severe form of Lobstein's syndrome, who underwent a Cesarean section. The following issues are discussed: the risk of sustaining fractures during positioning, fractures by automatic blood pressure measurement, an almost always existing latex allergy, a susceptibility for malignant hyperthermia, potential cardiac defect, difficult endotracheal intubation, lowering of the conus medullaris to an area usually used for spinal puncture, severe spinal deformities resulting in difficult puncture, hemorrhagic diathesis, and unpredictability of the expansion of local anesthetics in the vertebral canal. In this case the procedure could be carried out in spinal anesthesia without encountering major problems.

[The use of pulse oximetry in prilocaine induced methemoglobinemia]. / Untersuchungen zum Einsatz der Pulsoxymetrie bei prilocaininduzierter Methämoglobinämie.

During the last 15 years pulse oximetry has become a widely accepted method of monitoring during general and local anaesthesia. Pulse oximeters measuring with two wave-lengths are considerably affected by dyshaemoglobin. At concentrations up to 30%, CO-Hb cannot be distinguished from O2-Hb. Met-Hb, even in low concentrations, leads to a constant error of measurement; some authors recommended exploiting this for estimation of the Met-Hb concentration. To prove the aim of the present study was to test whether this error in measurement can be defined with one formula for different pulse oximeters. PATIENTS AND METHODS. In a prospective, randomized, double-blind study, 171 non-smoking patients with healthy lungs (ASA 1-3) who had received a plexus block for hand surgery were investigated. After premedication with 3.75-15 mg medazolam p.o. each patient received a total of 6 1O2 via a Hudson mask during the investigation. After 10 min the following pulse oximeters were put on the index finger: (1) Ohmeda BIOX 3700e, (2) Critikon Oxyshuttle, (3) Nellcor N 180. Simultaneously a venous blood sample was taken and analysed immediately with a Radiometer OSM3. The procedure was repeated 15, 30, 60 and 120 min after the plexus block. In 41 patients the plexus block was carried out with lidocaine (6 mg/kg body weight) and in 130 patients, with prilocaine (7 mg/kg body weight). RESULTS. There were no significant differences in age, sex and risk groups between the lidocaine and the prilocaine group. In the lidocaine group we were able to show that hyperoxic conditions can be maintained for 2 h with the method described. In the lidocaine group none of the pulse oximeters showed a psO2 less than 99%. Our results show significant differences between the three pulse oximeters. Therefore, in contrast to the convention followed in the literatur, the relation between Met-Hb and psO2 under hyperoxic conditions must be described with different formulas for each pulse oximeter as follows: (1) Ohmeda BIOX 3700e: Met-Hb = (101-psO2).0.6 (r = 0.94); (2) Critikon Oxyshuttle: Met-Hb = (101-psO2).0.7 (r = 0.83); (3) Nellcor N 180: Met-Hb = (101-psO2).0.9 (r = 0.92). DISCUSSION. Our results show that it is not possible to describe the connection between Met-Hb and psO2 for all pulse oximeters with only one formula, but it is possible to set up different formulas with good correlations for each of the three pulse oximeters. The reasons for the different sensitivity are probably the different algorithms used by the manufacturers. In spite of the good correlations we can not recommend Met-Hb estimation by pulse oximetry measurement with two wave-lengths, because the distinction of hypoxia and Met-Hb its not possible when hyperoxic conditions are not stable as they were in our controlled study. A low psO2 measured in patients with normal arterial blood gases can be an indication of Met-Hb, but the exact measurement of dyshaemoglobin is only possibly by using a co-oximeter.

[In vivo detection of the Christiansen-Douglas-Haldane effect in clinical conditions]. / In-vivo-Nachweis des Christiansen-Douglas-Haldane-Effektes unter klinischen Bedingungen.

The Christiansen-Douglas-Haldane effect, also termed Haldane effect, describes the dependence of CO2 absorption by blood on the degree of hemoglobin oxygenation. Under the physiological condition of an "open" system between blood and alveolus, the arterial partial pressure of CO2 (paCO2; mmHg) must range below the mixed-venous (pvCO2; mmHg) value. During the nonphysiological situation of a "closed" system, e.g. hyperoxic apnea after adequate pre-oxygenation (O2 uptake with lack of CO2 delivery), paCO2 can assimilate to pvCO2 and even exceed it. The remainder has often been termed a "paradoxical phenomenon". It was the aim of this study to prove the Haldane effect in vivo in the "closed" system of hyperoxic apnea. Eighty patients (ASA II-IV, NYHA II-III) scheduled for coronary surgery gave written informed consent and were examined. Following the preparations for induction (venous and arterial cannulas, pulmonary artery catheter), they were pre-oxygenated with 6 l O2/min until induction of anesthesia was achieved. Pre-oxygenation was maintained actively/passively until intubation. At the onset and the end of intubation the arterial (a) and mixed-venous (v) blood gas status (pHa, pHv, saO2 and svO2 (%), paO2 and pvO2, paCO2 and pvCO2 were determined using the Corning 170 pH/blood gas analyzer and the Corning 2500 CO-oximeter. Statistical analysis of the data was based on Student's t-test for paired samples. Periods of apnoea ranged between 60 and 180 s. The data were allocated to three groups, depending on the duration of apnea: Group I: 60-100 s; Group II: 101-140 s; Group III: 141-180 s.(ABSTRACT TRUNCATED AT 250 WORDS)

[Effect of different pre-oxygenation procedures on arterial oxygen status]. / Der Einfluss unterschiedlicher Präoxygenationsverfahren auf den arteriellen Sauerstoffstatus.

There are different opinions regarding efficiency, duration, and techniques of preoxygenation. It was the aim of our study to systematically investigate the effectiveness of different preoxygenation methods by means of arterial blood gas parameters (paO2, SaO2, and CaO2). METHODS. After receiving informed consent, 80 patients undergoing coronary bypass grafting (NY-HA II-III, ASA III-IV, mean age 57 years) were randomized in eight groups, each with a different preoxygenation technique (Table 1). During normocapnic preoxygenation (Table 2), the following parameters were compared: duration of preoxygenation (3 vs. 5 min), manner of holding the face mask (tightly fitting vs. one digit away from mouth and nose), and oxygen flow (6 vs. 10 l/min) via anesthesia circuit system. Arterial blood gases were analyzed with a Corning 170 pH/blood gas analyzer and a Corning 2500 CO-oximeter. For statistical analysis Student's t-test was used. P less than or equal to 0.01 was considered to be significant (*). RESULTS. As Fig. 1 shows, the different preoxygenation techniques affected paO2 values differently: oxygen flow had a greater influence than duration of preoxygenation. Most important was the manner of holding the face mask. With a tightly fitting mask, preoxygenation was more effective than with the face mask one digit away from mouth and nose, independent of preoxygenation time and oxygen flow (Table 3). The SaO2 (Fig. 2) increased in the same manner with the different preoxygenation techniques from 94.0% to 97.5% (Table 3); CaO2 (Fig. 3) was influenced in a similar way (16.7 ml/dl to 17.4 ml/dl).(ABSTRACT TRUNCATED AT 250 WORDS)

[Increase of prilocaine-induced methemoglobinemia following anesthesia induction]. / Verstärkung der prilocain-induzierten Methämoglobin-ämie durch Narkoseeinleitung?

Although the local anaesthetic prilocaine is less cardio- and neurotoxic than lidocaine, it bears the disadvantage of the formation of methaemoglobin by the metabolite o-toluidine. Prilocaine is often successfully used, especially for the blockade of the brachial plexus, but one problem of this technique is the failure rate of 3-10%, with the consequence that general anaesthesia after administration of prilocaine is frequently necessary. Methaemoglobin formation after prilocaine administration has been thoroughly investigated. Nothing is known, however, about the interactions of prilocaine and the induction of general anaesthesia relative to methaemoglobinaemia. CASE REPORT. Two patients (47 and 52 years old) each received 500 mg prilocaine for the axillary blockade of the brachial plexus. After 100 and 120 min respectively, it was necessary to induce general anaesthesia, for which 350 mg thiopental, 1 mg alfentanil and 45 mg atracurium were used. At 15 min after induction, methaemoglobin levels had increased by 70% and 25%, respectively, from baseline before general anaesthesia. CONCLUSION. It is not possible to explain these findings conclusively with the present method. To check whether displacement of o-toluidine from the plasma protein binding might have been responsible, we provoked methaemoglobinaemia in vitro by adding o-toluidine to heparinised blood. Thiopental was then added to half the specimens. Subsequently, methaemoglobin levels were lower in the samples with thiopental. Three explanations seem plausible: (1) Thiopental blocks the hydroxylase of the endoplasmic reticulum, with the result that o-toluidine cannot be further metabolised, leading to higher o-toluidine and methaemoglobin levels. (2) Isoflurane improves the blood supply of the liver. This results in increased metabolism of prilocaine to o-toluidine. (3) The results were accidental. To clarify which of these explanations is correct, further investigation is necessary.

[Insertion of a fiber optic catheter into the hepatic veins of patients with multiple organ dsfunction syndrome (MODS)]. / Anlage eines Fiberoptik-katheters in eine Lebervene bei Patienten mit Multiorgandysfunktions-syndrom (MODS) ohne Einsatz bildgebender Diagnostikverfahren.

As it is the driving force in the development of a multiorgan dysfunction syndrome (MODS), the gastro-intestinal region is at the centre of current discussion. Recently, hepatovenous oximetry has been used increasingly to monitor the relationship between oxygen supply and consumption in the splanchnic system. In the present paper we report an exclusively oximetrically controlled catheterisation procedure that can be carried out at the bedside without the use of imaging procedures. In the inferior vena cava a typical venous oxygen saturation profile can be expected. Near the opening of renal veins there is a peak in venous saturation due to the large extent to which the kidneys partake in the cardiac output and their relatively low oxygen consumption. Correspondingly there is a significant drop in saturation in the area around the opening of the hepatic veins. At the right atrium the oxygen saturation increase again due to admixing of more highly saturated blood from the superior vena cava. Taking these physiological facts into consideration it was attempted to find the opening of the hepatic veins into the inferior vena cava using only continuous in vivo oximetry and to insert a hepatovenous catheter. MATERIAL AND METHODS. In 14 patients with postoperative MODS (Apache II score > or = 20) a fibreoptic pulmonary catheter for the continuous evaluation of oxygen saturation was inserted via the inferior vena cava (entrance through the femoral vein). First the catheter was pushed forward into the wedge position in the usual way. Subsequently it was pulled back up to the region of high renal venous saturation. At this point the catheter, now unblocked, was pushed forward again with gentle twisting motions until a distinct decrease in saturation was reached well below the value of the mixed-venous saturation which can be taken as an indication for having entered the hepatic vein. Using a CO oximeter a slowly aspirated blood specimen was taken from the distal line of the catheter and analysed. The placement of the hepatovenous catheter was verified by radiograph of the abdomen. In most cases the catheter had to be readjusted several times before it reached its final position. RESULTS. Of the 14 patients, 13 showed the saturation course in the inferior vena cava that could theoretically be expected. In 12 patients (85.7%) we succeeded in placing the hepatovenous catheter correctly by applying this procedure. The average depth of insertion of the catheter after final positioning was 57 +/- 4 cm. Initial values of hepatovenous saturation (ShvO2) amounted to an average of 35.1 +/- 9.4%. The minimum value was 19%; the maximum ShvO2 came to 59%. DISCUSSION. With the procedure presented it was possible in 12 of 14 patients to position a hepatovenous catheter oximetrically controlled without further means. A precondition for this is a typical saturation profile of the inferior vena cava, which, however, was not found in one of the patients. A possible explanation for this could be an increased shunt volume in the hepatosplanchnicus area, which can lead to high ShvO2 values. For this reason the opening of the hepatic veins could not be recognized by a decrease in saturation using the oximetric procedure. Placement of a catheter was not possible. Future studies on larger groups of patients will be required to show to what extent monitoring of ShvO2 can lead to an efficient therapy specific for this part of the cardiovascular system in patients with sepsis and MODS.