[Continuous measurement of jugular venous blood gas. A case of subarachnoid bleeding].

INTRODUCTION

Recently, a compact multisensor device 0.5 mm in diameter has become available with a miniaturised Clark electrode for measuring blood oxygen tension and two optical fibres for measuring CO2 tension, pH, and temperature (Paratrend 7, Biomedical Sensors, High Wycombe, UK). We used this new probe for continuous blood gas monitoring in the jugular bulb as an alternative to the commonly used fiberoptic spectrophotometric oximetric measurement of haemoglobin saturation.

RESULTS

A 64-year-old patient was admitted for surgery of a right-sided intracranial aneurysm. During surgery, with no artefacts or evidence of catheter drift, a normal jugular venous pO2 (pjvO2) of 39 +/- 3 mmHg was measured. Over the period of weaning, two declines in pjvO2 occurred (22.5 and 18.7 mm Hg) associated with a decline in CO2 tension and a rise in pH. We treated these events successfully by analgosedation, controlled ventilation with an inspired oxygen fraction of 70%, and elevation of the mean arterial blood pressure to over 100 mmHg. Extubation was possible about 24 h later. Furthermore, 3 h after extubation pjvO2 values could be monitored without difficulty despite movement of the patient.

DISCUSSION

The technique of polarographically measuring pjvO2 with a Clark-type probe appears superior to fibreoptic jugular venous oximetry due to the clearly lower incidence of faulty measurements, especially in the intensive care unit, where patients undergo frequent nursing interventions and tend to awaken. We did not even observe artefacts due to patient movement after extubation. A limitation of the new multisensor system might be the distance of 4 cm between the sensor tip and the end of the insertion catheter, which makes samples drawn for in vitro blood gas analyses to control the continuous monitoring less comparable. Improvements in the construction of the probe are recommended.