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LETTERS TO THE EDITOR

Jugular Bulb Desaturations During Propofol Anesthesia in Neurosurgical Procedures

Department of Anesthesia and Critical Care ZOL Campus Sint-Jan Genk, Belgium

Michel Struys, MD, PhD

Department of Anesthesia University Hospital UZG Gent, Belgium

We read with interest the article by Jansen et al. (1) concluding that, during propofol anesthesia administration with normoventilation, 50% of patients with brain tumor showed signs suggestive of cerebral hypoperfusion. However, under a propofol/opioid anesthesia for cerebral aneurysm clipping, we seldomly observe jugular desaturations (i.e., jugular saturation [SjO₂] less than 50%) that cannot be attributed to a PaCO₂ less than 32 mm Hg or to a mean arterial pressure less than 90 mm Hg. Especially the role of PaCO₂ on jugular desaturations should be better analyzed. We noticed from their data that PaCO₂ was lower (although not significantly) in the propofol compared with the isoflurane-group and was more just around 32 mm Hg, which might already reach the critical level of cerebral hypoperfusion for some patients. Therefore, we think that the conclusion should include a warning for the use of even moderate hyperventilation during propofol/opioid anesthesia in neurosurgical patients.

A second remark concerns the respective depth of anesthesia in both groups. As the dose-dependent change of global cerebral metabolism induced by both anesthetics is essential for the correct interpretation of SjO₂ data, it is crucial to know whether depth of anesthesia was equal in both groups. Currently available Bispectral Index electroencephalogram monitoring offers the best method to evaluate depth of anesthesia, and therefore we think that all current (and future) studies comparing the effects of different anesthetics on SjO₂ should include BIS monitoring.

References

1. Jansen GFA, Van Praagh BH, Kedaria MG, Odoom JA. Jugular bulb oxygen saturation during propofol and isoflurane/nitrous oxide anesthesia in patients undergoing brain tumor surgery. Anesth Analg 1999;89:358–63.[Abstract/Free Full Text]

Response

Department of Anesthesiology Academic Medical Centre University of Amsterdam Amsterdam, The Netherlands

Bas van Praagh, MD

Department of Anesthesiology Ziekenhuis Centrum Apeldoorn Apeldoorn, The Netherlands

We greatly appreciate the interest of Dr. De Deyne et. al. in our study (1). A study by Moss et. al. (2) in patients with a subarachnoid hemorrhage showed that 23% of patients had a jugular bulb venous oxygen saturation (SvjO₂) of less than 50% under propofol/opioid anesthesia under circumstances that are normal during neuroanesthesia. In that study, in 8 of 9 patients the SvjO₂ improved to values higher than 54% on increasing mean arterial pressure with phenylephine. In our patients with brain tumors, in the propofol/opioid group with PaCO₂ of 32 mm Hg or higher, three patients showed SvjO₂ of 50 mm Hg or less. Conclusions of both studies could be that, in order to avoid an SvjO₂ of less than 50% during propofol/opioid anesthesia in patients with brain tumors, even moderate hyperventilation (PaCO₂ 32–35 mm Hg) is questionable, and that pharmacologically induced increases in arterial blood pressure should become a standard procedure during anesthesia. However, we still have no exact explanation why, during propofol/opioid anesthesia, the cerebral blood flow should be increased by using increased PaCO₂ and mean arterial pressure levels in order to avoid excessively low SvjO₂ levels of less than 50 mm Hg and not during isoflurane/nitrous oxide/fentanyl.

However, we do not know if it is justified to transfer the SvjO₂ of 50–55 mm Hg, marking the upper limit for hypoperfusion/ischemia, from the brain trauma arena to the brain tumor population. Although patients with brain trauma show worse outcome if SvjO₂ is less than 50 mm Hg for a certain period, no data are known that show an adverse outcome in patients with brain tumors who are receiving propofol/opioid anesthesia under moderate hyperventilation (PaCO₂ of 32 mm Hg or less, which is commonly accepted in neuroanesthesia) and who may have had SvjO₂ values of less than 50 mm Hg. More studies are required before propofol can be implicated in creating possible brain ischemia from hypoperfusion.

References

1. Jansen GFA, van Praagh BH, Kedaria MB, Odoom JA. Jugular bulb oxygenation during propofol and isoflurane/nitrous oxide anesthesia in patients undergoing brain tumor surgery. Anesth Analg 1999;89:358–3.
2. Moss E, Dearden NM, Berridge JC. Effects of changes in mean arterial pressure during cerebral aneurysm surgery. Br J Anaesth 1995;75:527–30.[Abstract/Free Full Text]

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