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LETTER TO THE EDITOR

Precipitous Bispectral Index Decline and Delayed Emergence After Lumbar Puncture

Department of Anesthesiology, Baystate Medical Center, Springfield, Massachusetts, Tufts University School of Medicine, Boston, Massachusetts, Jordan.Blinder{at}bhs.org (Blinder) Department of Anesthesiology, Baystate Medical Center, Springfield, Massachusetts (Seaman, Ghandour) Division of Neurosurgery, Baystate Medical Center, Springfield, Massachusetts (Oh)

To the Editor:

A 36-yr-old female presented for lumbo-peritoneal shunting to treat chronically increased cerebrospinal fluid (CSF) pressure, caused by cryptococcal meningitis. The preoperative neurologic examination was unremarkable except for diplopia and nystagmus. Neuroradiology revealed normal ventricles and no mass lesions. We elected to monitor with a bispectral index (BIS) in addition to standard hemodynamic monitors. We induced general anesthesia, intubated the patient’s trachea, and placed her in a left lateral decubitus position. She was maintained on sevoflurane at a stable inspired concentration. As part of the procedure we inserted a 14-G Tuohy needle into the intrathecal space at the L4-5 interspace. One-hundred milliliters of CSF was lost rapidly, and the BIS almost immediately decreased to values in the 5–20 range for approximately 12 min (Fig. 1. The patient’s vital signs remained stable. The procedure was completed without incident, and she awoke without deficit. Although we cannot exclude an artifact, there was no evidence that the abrupt decrease in BIS was due to equipment defect. We believe that the decrease in BIS reflected acute global hypoperfusion precipitated by the abrupt decrease in CSF, which rapidly resolved (1–4).

View larger version (105K): [in this window] [in a new window]   Figure 1. Intraoperative BIS.

REFERENCES

1. Czosnyka M, Pickard JD. Monitoring and interpretation of intracranial pressure. J Neurol Neurosurg Psychiatr 2004;75:813–21.[Abstract/Free Full Text]
2. Miller RD. Miller’s anesthesia. 6th ed. New York: Churchill Livingstone, 2005:1250–6.
3. Han CY, Backous DD. Basic principles of cerebrospinal fluid metabolism and intracranial pressure homeostasis. Otolaryngol Clin North Am 2005;38:569–76.[Web of Science][Medline]
4. Samadani U, Huang JH, Baranov D, et al. Intracranial hypotension after intraoperative lumbar cerebrospinal fluid drainage. Neurosurgery 2003;52:148–51.[Web of Science][Medline]

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