Nursing care of the Paratrend 7 sensor.

The Paratrend 7 sensor is a continuous intravascular blood gas sensor that consists of a miniaturized Clark-type PO2 electrode, fibreoptic pH and PCO2 optodes and a thermocouple, the monitor continuously displays the measured pH, PaO2 PaCO2 and temperature of the blood, and the calculated oxygen saturation, BE and SBC. After 7 years of caring for over 200 patients following insertion of the sensor, we describe our nursing experience with particular emphasis on the adequate fixation of the cannula, sensor system and connectors. The maintenance of the sensor through adequate flushing of the arterial line and care of the insertion site is described. Also outlined are the potential advantages to nursing practice of this new monitoring system, with particular reference to early warning of deterioration in respiratory function, closer control of mechanical ventilation and reduction in blood gas sampling and the errors inherent therein.

Continuous intra-arterial blood gas monitoring.

OBJECTIVE: To review the technology, clinical trials and current status of continuous blood gas monitoring in intensive care. DESIGN: The review describes the history, technology, various clinical trials on continuous blood gas monitoring and discusses the various factors which might affect their performance characteristics and outlines their potential role in intensive care and during anaesthesia. CONCLUSIONS: Over the past 10 years a number of continuous intra-arterial blood gas monitoring systems have been developed. The performance characteristics of these systems are comparable. Their levels of accuracy as measured in bench tonometry are not consistently achieved in clinical trials. The potential usefulness of these monitors in various clinical situations has been described in case studies. Controlled studies demonstrating an improvement in outcome with the use of these monitors have not been published.

Continuous measurement of arterial blood gas status during total hip replacement: a prospective study.

The arterial blood gas chemistry was measured continuously in ten patients during primary cemented total hip replacement in order to define more precisely the patterns of changes in blood gases during various stages of the operation. All ten patients demonstrated significant drops in PaO2 after femoral cement implantation and nine of the ten after acetabular cement implantation. The mean drop in PaO2 following acetabular cement expressed as mean +/- SD was 18 +/- 8 mmHg (16 +/- 6%) (P < 0.05) and femoral cement application was 25 +/- 11 mmHg (23 +/- 9%) (P < 0.05). For changes in PaO2 there were corresponding drops in SpO2 in all patients with the femoral cement and in eight patients with the acetabular cement. The mean drop in SpO2 following the application of acetabular and femoral cements respectively were 1.7 +/- 1.5% and 3 +/- 2.45%. No changes in blood PaO2 were observed during dislocation of the hip joint or reaming of acetabulum and femur. In vitro studies revealed no effect of the liquid monomer or the cured cement on the performance of the Clark electrode of the sensor. We suggest that significant drops in PaO2 occur with both acetabular and femoral cement implantation and that the derangements in blood PaO2 last longer than detected by pulse oximetry following cement implantation.

Evaluation of the Paratrend 7 intravascular blood gas monitor during cardiac surgery: comparison with the C4000 in-line blood gas monitor during cardiopulmonary bypass.

OBJECTIVE: To evaluate the performance of the Paratrend 7 intravascular blood gas monitor (Biomedical Sensors, High Wycombe, UK, Ltd) during cardiac surgery and compare it with that of an in-line blood gas monitor placed in the arterial limb of an extracorporeal circuit during cardiopulmonary bypass. DESIGN: A prospective study. Consecutive patient enrolment. SETTING: In the cardiac surgical intensive care units at a tertiary referral center. INTERVENTION: Insertion of the Paratrend 7 intravascular sensor through the radial arterial catheter after induction of anesthesia. MEASUREMENTS AND MAIN RESULTS: Simultaneous measurements of pH, PCO2, and PO2 were made from the sensor and the blood gas analyzer, and the bias and precision were calculated on all the measured parameters. The bias and precision of the intravascular sensor during bypass for pH, PCO2, and PO2 were 0.01 and 0.06 pH units, 0.5 and 2.5 mmHg (2% and 8%), and 3 and 45 torr (0.5% and 14%), respectively. The bias and precision for the prebypass and the postbypass phases were comparable. The bias and precision of the extracorporeal monitor for pH, PCO2, and PO2 were 0.04 and 0.1 pH units, -0.3 and 4 mmHg (-1% and 15%) and 8 and 48 mmHg (4 and 18%), respectively. There were no instances of any complications attributable to the intravascular sensor. CONCLUSIONS: The intravascular sensor used in this study functioned well during cardiopulmonary bypass and the postbypass phase. The performance of the intravascular sensor was better than the in-line blood gas monitor during cardiopulmonary bypass.

The evaluation of a new intravascular blood gas monitoring system in the pig.

OBJECTIVE: Our objective was to investigate the accuracy of a new intravascular blood gas sensor, the Paratrend 7 (P7) (Biomedical Sensors Ltd, Pfizer Hospital Products Group, High Wycombe, England) in a porcine model. METHODS: A total of 12 sensors were inserted into 10 animals under total intravenous anesthesia. Changes in blood gas chemistry were produced over a wide range by manipulating the inspired oxygen and carbon dioxide concentrations and by adjustments in minute ventilation. Blood gas samples (BGA) were taken and analyzed during periods of stability; the results obtained were compared with the readings from the intravascular sensor. RESULTS: A total of 292 blood gas samples were taken and analyzed for pHa, PaCO2, and Po2; the results were compared with the readings from the intravascular sensor. Correlation coefficients of r = 0.98 for PCO2 and r = 0.99 for PO2 were obtained. Analysis of bias and precision as mean +/- SD of the difference (P7 - BGA) gave the following results: pH bias = -0.03, precision = +/- 0.04; PCO2 bias = 0.65 mm Hg, precision = +/- 3.1 mm Hg; and PO2 bias = -6.50 mm Hg, precision = +/- 0.6 mm Hg. No problems with clot formation on the sensor were seen, and the sensors did not appear to show the "wall effect" seen with other systems. CONCLUSIONS: The results obtained were well within the requirements for a clinically useful blood gas monitoring system.

Continuous measurement of blood gases using a combined electrochemical and spectrophotometric sensor.

The use of a combined electrochemical and fibreoptic continuous intra-arterial blood gas sensor is described. The purpose of the study was to evaluate the performance of the sensor in 10 patients in the intensive therapy unit following insertion through a femoral arterial cannula. To our knowledge this is the first published study on the valuation of an intravascular blood gas sensor through a femoral arterial cannula. A total of 71 sets of data comparing the sensor with the blood gas analyser were obtained. The bias and precision for pH, PCO2 and PO2 were 0.006 and 0.07 pH units, 0.2 and 1.65 kPa (4.6% and 29%) and 0.8 and 2.7 kPa (5.1% and 14.3%) respectively. There was a degree of imprecision of the PCO2 sensor, the reasons for which are discussed. In summary, the intra-arterial sensor functioned well when inserted into the femoral artery in post-cardiopulmonary bypass patients. There were no complications attributable to sensor placement.

A multiparameter sensor for continuous intra-arterial blood gas monitoring: a prospective evaluation.

OBJECTIVE: To compare measurements of arterial blood gases made by a new continuous intra-arterial blood gas monitor with measurements in a standard blood gas analyzer in patients in the general and cardiac intensive care units. DESIGN: Criterion standard study. SETTING: The cardiac surgical and the general medical intensive care units of a tertiary referral center. PATIENTS: Thirteen consecutive patients requiring mechanical ventilation and blood gas monitoring. INTERVENTIONS: All patients had a blood gas sensor placed through a 20-gauge cannula inserted into the radial artery. The duration of monitoring ranged from 9.42 to 117.45 hrs. MEASUREMENTS AND MAIN RESULTS: A total of 158 simultaneous measurements of pH, PCO2, and PO2 were made from the sensor and the blood gas analyzer, and the bias and precision were calculated on all measured parameters. The overall bias +/- precision values were 0.01 +/- 0.06 for pH, 1.4 +/- 4.8 torr (0.2 +/- 0.7 kPa) for PCO2, and 2.8 +/- 25.6 torr (0.4 +/- 3.4 kPa) for PO2. The bias and precision for PO2 measurements that were < 150 torr (< 20 kPa) were 0.45 +/- 20.7 torr (0.1 +/- 2.8 kPa). The bias and precision for values of PO2 that were > 150 torr (> 20 kPa) were -8.1 +/- 28 torr (-1.1 +/- 3.8 kPa). The mean in vitro 90% response times of pH, PCO2, and PO2 sensors were found to be 78, 143, and 70 secs, respectively. There were no instances of any complications attributable to the sensor. CONCLUSIONS: The continuous intra-arterial blood gas monitor tested in this study measures and trends arterial blood gases with an acceptable level of clinical accuracy. Longevity and safety of sensor function have also been demonstrated.

A glucose sensor utilising tetracyanoquinodimethane as a mediator.

This paper describes an amperometric enzyme electrode for glucose analysis. The electrode utilised the mediator tetracyanoquinodimethane (TCNQ) to facilitate electron transfer from glucose oxidase to a pyrolytic graphite carbon electrode. The electrode demonstrated a response to glucose in a clinically relevant range (0-70 mM). Results concerning the direct current cyclic voltammetry of TCNQ and the electrodes' response to glucose, pH profile and the effect of temperature are presented.