LETTERS TO THE EDITOR: Letters & Announcements
To the Editor:
We have read with great interest the article of Muñoz et al. (1), which compared the effect of propofol or sevoflurane in combination with nitrous oxide on jugular bulb oxygen saturation (Sjo2) in neurosurgical patients undergoing resection of brain tumors. The authors could demonstrate in their investigation that N2O did not reduce the incidence of low Sjo2 values (50%) in patients anesthetized with propofol.
Comparable results in neurosurgical patients were found by Jansen et al. (2). Both, (1) and (2) described low Sjo2 values in patients anesthetized with propofol and ventilated at relative low Paco2 values (30 respective 32 mmHg). We think that the patients of both studies have been moderately hyperventilated. The low Sjo2 values were the result of propofol administration, but were additionally induced by moderate hyperventilation.
We could find in our study a reduction of Sjo2 values from 67% to 50% in neurosurgical patients anesthetized with propofol and moderately hyperventilated from Paco2 40 mmHg to 29 mmHg (3). With our latest study, we could demonstrate that hyperventilation (from Paco2 38 mmg to 30 mmHg) in patients with a propofol-based anesthesia and additional N2O leads to a reduction of Sjo2values from 68% to 50%(4).
Our results correlate with studies from De Baerdemaeker et al. (5,6). The authors recommend that forced hyperventilation (Paco2 < 25 mmHg) should be reconsidered. Moderate hyperventilation (Paco2 30 mmHg) can cause cerebral hypoperfusion associated with low Sjo2(< 50%) and increased AJDo2values (> 9 ml/dl) in some patients.
We agree with Muñoz et al. (1), that additional N2O cannot prevent low Sjo2 values in hyperventilated patients under propofol-based anesthesia. In normocapnic patients (Paco2 38 mmHg) anesthetized with propofol and additional N2O we have not seen low Sjo2 values (4).
Lutz Schaffranietz, MD
Christian Rudolph, MD
Wolfgang Heinke, MD
1. Muñoz HR, Nunez GE, de la Fuente JE, Campos MG. The effect of nitrous oxide on jugular bulb oxygen saturation during remifentanil plus target-controlled infusion propofol or sevoflurane in patients with brain tumors. Anesth Analg 2002; 94: 389–92.
2. Jansen GF, van Praagh BH, Kederia MB, 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.
3. Schaffranietz L, Heinke W. The effect of different ventilation regimens on jugular venous oxygen saturation in elective neurosurgical patients. Neurol Res 1998; 20 (Suppl.1): S66–S70.
4. Schaffranietz L, Rudolph C, Heinke W, König F. Is the combination of nitrous oxide and hyperventilation in elective neurosurgical operations useful? (Article in German). Anaesthesiol Reanimat 2000; 25: 88–95.
5. De Baerdemaeker L, Van Poucke S, Van Aken J, et al. Potential for cerebral hypoperfusion during a propofol or an isoflurane based anesthesia and moderate hypocapnia in neurosurgical patients. Anesth Analg 1998; 86: S341.
6. De Baerdemaeker L, Van Aken J. CO2
-management in neuro-anaesthesia. Eur J Anaesthesiol 2000; 17 (Suppl.18): 85–96.