Continuous arterial blood gas monitoring during bilateral sequential lung transplantation

Accuracy and performance of a modified continuous intravascular blood gas monitoring device during thoracoscopic surgery

OBJECTIVE

The only commercially available continuous intravascular blood gas monitoring system for adults, the Paratrend (Diametrics Medical Inc, High Wycombe, UK), was modified by the manufacturer to the Paratrend 7+ (PT7+) in 1999. The aim of this study was to evaluate the modified probe over a wide range of blood gas and pH values during thoracoscopic surgery in a similar setup as done with the previous model.

DESIGN

Prospective methods comparison study.

SETTING

University hospital.

PARTICIPANTS

Twenty-three patients.

INTERVENTIONS

Elective thoracoscopic surgery.

MEASUREMENTS AND MAIN RESULTS

One hundred thirteen PT7+ readings and their corresponding arterial blood gas and pH measurements (ABGA) were evaluated. The ranges for ABGA values were 50 to 474 mmHg for PO(2), 29 to 58 mmHg for PCO(2), and 7.28 to 7.49 for pH. Bland and Altman analysis revealed a bias +/- 2 standard deviation of -20 +/- 86 mmHg for PO(2), 3 +/- 9 mmHg for PCO(2), and -0.01 +/- 0.06 for pH. No specific complications attributable to the probe were observed.

CONCLUSION

In patients undergoing thoracoscopic surgery with rapidly changing blood gas parameters, the PT7+ device is a valuable trend indicator and hence may be helpful for clinical decision making. However, the underestimation of PO(2) values by 20 mmHg on average and the wide limits of agreement documented in this study must be regarded as limiting factors.

Continuous intravascular blood gas monitoring: development, current techniques, and clinical use of a commercial device

This review focuses on the development, current techniques, and clinical use of continuous intravascular blood gas monitoring (CIBM) devices in anaesthesia and intensive care. The operating principles, range of application, performance, limitations, costs, and impact on patient treatment and outcome, are discussed. Studies of early and currently available CIBM devices were analysed. At present, the Paratrend 7+ (PT7+) for adults and Neotrend (NT) for newborns are the only commercially available CIBM systems. The PT7+ contains three optical sensors to measure PO(2), PCO(2) and pH, as well as a thermocouple to measure temperature. The NT is a modification of the PT7+ to continuously monitor PO(2), PCO(2), pH and temperature in newborns. Under laboratory conditions, good performance over a wide range of blood gas values was observed with the Paratrend 7 (PT7. Performance in the clinical setting was not as satisfactory, especially for PO(2) values. However, the performance and accuracy of CIBM devices appear to be sufficient for clinical use and they are being used clinically in selected patient groups. Several factors affecting the performance of CIBM are considered.

Continuous intra-jugular venous blood-gas monitoring with the Paratrend 7 during hypothermic cardiopulmonary bypass

We measured the accuracy of the continuous intra-vascular blood-gas monitoring system (Paratrend 7, PT7) placed in the jugular venous bulb in 18 adult patients having cardiac or aortic surgery with hypothermic cardiopulmonary bypass (CPB). After induction of anaesthesia, a PT7 sensor was inserted through a 20-gauge venous catheter into the right jugular venous bulb. Blood samples were drawn from the venous catheter and measured with a blood gas analyser (BGA). Five to eight paired measurements using the PT7 and blood samples were made per patient, and bias and precision were calculated for each patient using the Bland-Altman method. The ranges for the blood sample measurements were: pH 7.12 to 7.59, PCO(2) 3.7 to 9.6 kPa, PO(2) 3.5 to 16.0 kPa, oxygen saturation 40 to 99%, bicarbonate 18.6 to 34.4 mmol l(-1), and base excess -7.8 to 12.5 mmol l(-1). Bias and precision values were 0.014/0.071 for pH, 0/0.90 kPa for PCO(2), and -0.16/1.18 kPa for PO(2). These values were comparable with those previously made on arterial blood. However, precision for oxygen saturation in each patient varied 2.3 to 23.6% (95% CI: 6.3 to 12.9%), which was unsatisfactory for clinical measurements. Deep hypothermia ( approximately 19.6 degrees C) and marked haemodilution ( approximately 13.5%) during CPB did not influence the reliability of the PT7 sensor. Thus, we concluded that continuous intra-jugular venous blood-gas monitoring is clinically feasible using the PT7 and may provide valuable information during CPB.

Monitoring of Organ Dysfunction in Sepsis/Systemic Inflammatory Response Syndrome: Novel Strategies

Abstract. Sepsis and systemic inflammatory response syndrome—induced severe disruption of microcirculation and consecutive tissue hypoxia is considered a key factor in the development of organ dysfunction and multiple organ failure. The conventionally measured global variables such as lactate or macrohemodynamic parameters using a pulmonary artery catheter do not adequately mirror microcirculatory disturbances. Evaluation of the severity of microcirculatory distress and the effectiveness of resuscitation strategies requires new clinical technologies aimed at the microcirculation. It is anticipated that novel techniques such as optical spectroscopy and intelligent biosensors will play a major role in the development of new monitoring systems. In general, the current monitoring of organ dysfunction is characterized by a trend from invasive to noninvasive and “safe” techniques, which provide bedside or even on-line monitoring and allow a more precise and earlier detection of organ dysfunction. Techniques for the assessment of regional perfusion and microcirculatory bioenergetics to direct therapeutic procedures are expected to refine and optimize clinical treatment of critically ill patients in the future. This article addresses the question of which variables should be monitored, what is feasible, and what is valid for therapeutic consequences. Recent developments in monitoring of macro- and microcirculation and organ-specific dysfunction, e.g., lung, kidney, are described with respect to their advantages and limitations, and future directions are outlined.