[Humidification and heating of anesthetic gases during pediatric anesthesia using the Cicero Anesthesia Workstation]

A series of 52 infants underwent general or urological surgery; all were ventilated with the CICERO. Two different flows of fresh gas were used. In group I (n = 21) the fresh gas flow was set exactly at the level of the minute volume, representing a half-open, non-rebreathing system. In group II (n = 31) the fresh gas flow was adjusted to 10% of the required minute volume. Temperature and relative humidity of the inspired gas were measured continuously close to the tracheal tube. Anaesthesia was accomplished with 2 vol% isoflurane, 21-30 vol% oxygen in nitrous oxide. The results were compared with those achieved with our time-tested paediatric equipment, a SERVO 900D ventilator with a Fisher-Paykel humidifier (Group III, n = 35). Using a high fresh gas flow, no increase in relative humidity in the inspired gas could be detected. The values varied between 12% and 25% (group I). Reducing the flow of fresh gas as indicated above resulted in an increase in the relative humidity (group II). Over the evaluated period of 2 h, humidity increased slowly from an initial mean value of 20% to a maximum of something over 70%. Using the SERVO 900D ventilator combined with the Fisher-Paykel humidifier, humidity reached a value of greater 90% within 10 min after activation of the heated cascade. Humidity in the inspired gas should exceed 70% to avoid damage to infant airways. This will not be attained until after more than 2 h with unaided breathing systems, by when most operations performed on paediatric patients will already be over. Condensed water may aspirated by small infants. This potentially dangerous situation was only encountered in the CICERO circuit, and not in the system protected by the Fisher-Paykel cascade. Dry gases can result in thickened mucous and in obstruction of a small tracheal tube, which requires emergency reintubation. With artificial airways dry gases damage the ciliated epithelia of the trachea and cause loss of water and body heat. The temperature of the "cold" gases varied within a range of 21-33 degrees C and could not be adjusted by the anaesthetist. In the CICERO system, heating the gases at the valve only prevents mechanical failure caused by water condensation. In pediatric anaesthesia, variable heating and non-condensing humidity are essential. The dry and heated gases of the CICERO are not acceptable in the daily practice of paediatric anaesthesia.

[Measurement of end-expiratory carbon dioxide values in pediatric anesthesia]

This study dealt with two principles of the evaluation of end-expiratory CO2 in pediatric anaesthesia: detection of CO2-influenced infrared rays with a full stream analyzer attached to the tracheal tube; CO2 measurement with a side-stream analyzer connected to the breathing and ventilating system by a small tube. The linearity of the analyzers was tested with gas mixtures containing 3.0/5.0/7.0 vol% of CO2 cycling at an increasing rate. Additional mass-spectrometry has proven that the instruments are accurate within the clinical range of pediatric anesthesia. A maximal deviation of 8% develops when cycling rates increase to 40 per min. To detect quality differences in the analyzers, tangential constructions onto the CO2 curves plotted by the capnographs provided valuable quotients. Depending on the length of the tubing that feeds samples of respiratory gas into the side-stream analyzer, the CO2 curves were subject to sinus degradation with increasing respiratory rates. Capnography with full-stream analyzers depended on inspiratory zero CO2 content for reference purposes.

[Comparison of volume substitutes 5 percent human albumin and 6 percent hydroxyethyl starch (40,000/0.5) in pediatric anesthesia]

Human albumin 5% (HA), frequently used in paediatric anaesthesia as a human plasma substitute, could be replaced by hydroxyethyl starch 6% (HES) 40,000/0.5 provided its use would not entail any disadvantages but rather advantages instead. This problem was studied by examining 30 children (mean body weight 32.5 kg) in general anaesthesia. During about 3 hours of surgery the patients lost up to 15 per cent (approx. 400 ml) of blood volume. In a randomised study the blood loss was compensated either via HA or HES with 14 ml/kg body weight each, respectively. Blood pressure and pulse rate remained within the normal range. Haemodilution was represented by a drop in the erythrocyte count to about 3 million/microliter, haematocrit (HCT) to about 30% and haemoglobin to approx. 10 g/100 ml. Slight metabolic acidosis (Bodansky unit = -4 mmol/l) was found to be statistically not significant (= n.s.) with both methods, as was the difference in serum albumin and during serum electrophoresis. Serum [Na+] was reduced in those children who had been treated with HES, to 137.33 +/- 33.30 mmol/l; however, in those children who received HA with low sodium content (statistically significant difference = s.s.) the corresponding level was 134.15 +/- 2.36 mmol/l. Serum creatinine rose in each case from 60 to 80 mmol/l (s.s.), renal function being slightly impaired probably due to the anaesthesia and surgery. The value according to Quick's test and the partial thromboplastin time (PTT) remained in the normal range both with HA and HES treatment (in each case over 70% and below 25s, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

[Isoflurane in pediatric anesthesia]

Seventy patients 1-10 years of age were submitted to isoflurane (I) or halothane (H) anaesthesia (O2:N2O = 1:3); H was used as a reference substance. Under I anaesthesia, haemodynamic parameters proved to be well preserved. While the pulse rate under I increased significantly, the diastolic pressure decreased as a result of peripheral vascular dilatation. Baroceptor reflexes seemed to function more properly under the effect of I. Spontaneous respiration was definitely depressed by I. Respiratory rate, minute volume, end-expiratory CO2 and pCO2 values indicated CO2 accumulation. Younger children breathing spontaneously were subject to airway problems in I more than in H anaesthesia by decreasing negative occlusion pressures. Increasing doses of vecuronium bromide (5, 10, 15 and 70 micrograms/kg body wt.) accomplished muscular relaxation of various degrees, as tested by the train-of-four (TOF) method. The use of I in two age groups resulted in faster onset, more profound muscular relaxation, and longer duration in comparison with H; these results were statistically significant.

[Pseudarthrosis of the clavicle - an unnecessary complication? (author's transl)]

The pseudarthrosis of the clavicle is a rare complication of trauma surgery. The pseudarthrosis is mainly situated in the two medial quarters of the bone. The stable plate-osteosynthesis is regarded as the best treatment in combination with an autologous bone grafting in cases of atrophic or defect-pseudarthrosis. From 1970 to 1981 20 patients were treated at the BG Unfallklinik Tübingen, indication, operative procedures and the results are given. A bony union was achieved in all cases.

Extracellular K+ concentration and K+ balance of the gastrocnemius muscle of the dog during exercise

Exercise-induced changes of the extracellular and the venous K+ concentrations ([K+]e, [K+]ven) were measured continuously in autoperfused dog gastrocnemii using PVC liquid membrane electrodes. O2 consumption (VO2), blood flow and performance of the muscles were also determined. The muscles were stimulated indirectly and isotonic tetanic contractions (0.2 s) were produced every 0.7 s for more than 45 min. 1. [K+]e started to increase immediately after the onset of exercise and reached a maximal value of 7.4 meq/l after 4 min of exercise, thereafter it decreased, reaching 5.3 meq/1 at the end of the 12 min exercise. After 6 min of recovery [K+]e became lower than the control level. [K+]ven reached maximal values of 5.0 meq/l after 30 s of exercise and thereafter decreased slowly to 3.8 meq/l at the end of exercise. Thus, a K+ gradient of up to 3 meq/l was observed between the interstitial space and the venous blood. About 30 s after the end of exercise a net K+ uptake of up to 0.3 mu eq per min per g was observed. 2. The K+ loss of the muscle fibres reached maximal values of 1.5 mu eq per min per g at 1.5 min after the onset of exercise. Total K+ loss was 7% during 12 min of exercise and 12.5% of intracellular K+ during 45 min of exercise. 3. The changes of [K+]e correlated closely with performance and VO2 during exercise but not during recovery. On the other hand, blood flow correlated with the changes of [K+]e during both exercise and recovery. These results support the hypothesis that changes of [K+]e of the working muscle might be an important factor regulating exercise hyperemia.

[Indication, technique, and results for high tibial osteotomies (author's transl)]

In degenerative and posttraumatic osteoarthritis of the knee joint pain is a major indication for correctional osteotomy. In additon, the degree of arthrosis, axis deviation, range of motion and derangement of ligaments must be considered. In the cases reviewed supracondylar femur osteotomy, extraligamentar and high interligamentar osteotomy of the tibial head were utilized for correction. High tibial osteotomies were performed without using stabilizing plates. Autologous as well as homologous bone implants were added as needed. From the results presented we conclude, that the different methods of correctional osteotomies are equivalent, as long as the axis deviation, which is present in most cases, is corrected into a physiological valgus position. About 3/4 of the patient operated upon were improved as far as pain, range of motion and weigthbearing are concerned. Regression of the arthrotic structural changes could be demonstrated in a few cases only.

[Local contractility and acidosis in the ischemic myocardium of the dog (author's transl)]

In open chest dogs up to 8 side branches of the R, circumflexus and descendens were embraced and could selectively be occluded. With a new developed method local myocardial length changes in the ischemic areas, and with H+-sensitive minielectrodes the interstitial H+-activities were measured. All changes which were observed during the 3-30 min lasting coronary artery occlusions (H+-increases to about 500 neq/1, increases of diastolic length, decreases of the contraction amplitude, ST-elevations) returned to preocclusion levels during reperfusion. LVP and dp/dt remained unchanged during ischemia and reperfusion.