A prospective study of catheter-related complications of intrathecal drug delivery systems.

Intrathecal drug administration via implanted pump is an effective treatment for intractable pain and spasticity but can be compromised by catheter-related complications. To determine the etiology of catheter-related complications, we have conducted a multicenter, prospective study of the long-term performance of a one-piece catheter system. Data pertaining to catheter-related complications were collected at implant and at specified times during the follow-up period. Catheter implantation characteristics that might affect complications were assessed. Two hundred nine patients were studied at 22 participating centers, with 1764 cumulative patient-months of catheter experience. Forty-nine catheter system complications occurred in 37 patients (7 complications related to the catheter itself, and 42 complications related to the implantation procedure). The 9-month complication-free "survival" rate was 78.9% overall (95.5% for the catheter itself). No specific catheter implantation characteristics were associated with the occurrence of complications. These data indicate that the incidence of complications for a one-piece catheter system is similar to that of commercially available two-piece systems, and highlight the need for careful surgical technique during implantation.

Oxygen uptake and static lung compliance during automatic ventilation.

Oxygen uptake is an important parameter to control proper tissue oxygen delivery. Oxygen uptake is dependent on adequate lung function and easily disturbed by changes in lung compliance and related parameters such as the tidal volume controlling pressure support. Simultaneous on-line registration of oxygen uptake and lung compliance together with ventilatory pressures applied to achieve preset tidal volumes has been made possible using the computer feedback controlled closed circuit ventilatory system Physio-Flex (Physio Co, Hoofdorp, The Netherlands). The system guarantees for leakage free functioning (maximal leakage 7 mL gas loss/minute) and, therefore, patient oxygen consumption measurements with an accuracy of more than 95%. A specially developed membrane ventilation mode registers on-line flow and displaced volume automatically corrected for temperature, pressure and compressible volume. The current investigation has shown: Decrease oxygen consumption versus oxygen delivery supply dependency may be induced by reflectory decreases of heart rate and cardiac output; in this case a reactive pulmonary parameter change is preceding the event in form of a drop in compliance and corresponding changes in ventilatory pressures necessary to maintain the preset tidal volume. In contrast, decrease of oxygen uptake following changes in cardiac output due to acute hypovolemia has no effect on pulmonary function parameters. This can be diagnostically used as moderate changes of tidal volume also have no significant influence on pulmonary parameters. However, changes due to reduction in depth of anesthesia and relaxation have some influence and need to be excluded.

pO2-profiles in human muscle tissue as indicator of therapeutical effect in septic shock patients.

Automatically stepwise driven pO2 electrodes were transcutaneously inserted into muscle tissue of severely ill septic shock patients. The pO2 profile was plotted from 200 individual measurements registered during 5 minutes and a histogram plotted for documentation. Arterial and venous blood gases, cardiac output, systemic and pulmonary vascular resistance were measured continuously on-line. In septicemia multiple drug schemes are suggested all intending to increase oxygen supply to the tissue and to improve oxygen demand/supply mismatch. So far the attending physician is bound to conclude and continue respectively change the treatment scheme according to the above described macrophysiological parameters. Perfusion distribution and local inhomogenities of tissue oxygen supply remain undetected. In the described study pretreatment pO2 profiles in musculus quadriceps femoris were obtained and measurements repeated in intervals of 10 minutes after start of pharmacological treatment. The changes of pO2 profiles of 20 patients, monitored in such a way over days and weeks, were carefully correlated to the described cardiocirculatory parameters and blood gas analyses. Dopamine was used to improve cardiac function and tissue oxygen supply as well. The investigations show that resulting changes of cardiovascular and blood gas parameters do not always indicate that tissue oxygen supply has really improved. On the other hand there was never an improvement in tissue oxygen supply when no changes of the other parameters had occurred. It is advised to add as a further diagnostic parameter tissue pO2 measurements to get insight if improvement in cardiac and pulmonary function really has the intended effect of improvement of tissue oxygen supply.