Electroencephalographic Changes from Hyponatremia During Transurethral Resection of the Prostate

0022-5347/93/1495-ll44$03.00/0 THE JOURNAL OF UROLOGY Copyright © 1993 by AMERICAN UROLOGICAL ASSOCIATION, INC.

Vol. 149, ll44-ll45, May 1993 Printed in U. S. A.

ELECTROENCEPHALOGRAPHIC CHANGES FROM HYPONATREMIA DURING TRANSURETHRAL RESECTION OF THE PROSTATE R. V. REDDY, S. S. MOORTHY

AND

S. F. DIERDORF

From the Departments of Neurology and Anesthesiology, Indiana University School of Medicine, and Department of Veterans Affairs, Richard L. Roudebush Medical Center, Indianapolis, Indiana

ABSTRACT

A patient undergoing transurethral resection of the prostate suffered hyponatremia during the peri operative period. Electroencephalography demonstrated diffuse slowing although the patient was not clinically encephalopathic. The serum sodium level may indicate a trend toward development of the transurethral resection syndrome but the sodium level does not necessarily parallel metabolic changes in brain tissue. Consequently, electroencephalography may aid in the early diagnosis and treatment of encephalopathy during the early phases of the transurethral resection syndrome. KEY WORDS: prostatic resection, electroencephalography, hyponatremia, sodium, brain

Central nervous system complications after intravascular absorption of irrigation fluid during transurethral resection of the prostate range in severity from minor to life-threatening, and depend on the rate of absorption and the amount of fluid absorbed.' Hoekstra et al noted that 1 of 30 patients had altered sensorium after transurethral resection of the prostate using 1.5% glycine as the irrigation fluid. 2 The onset of altered sensorium, including coma, is variable and ranges from 15 minutes after initiation of the procedure to 10 hours postoperatively. Visual disturbances have also been reported as complications of transurethral resection of the prostate when glycine solutions have been used as irrigating fluid and hyponatremia develops.3 Descriptions of visual disturbances include dimming of vision, light perception only and no light perception for several hours. 4 The patients are generally alert but nauseated when altered vision is reported. Vision returns to normal within 2 to 3 hours. Severe hyponatremia can cause focal or generalized seizures. Early detection of symptoms is essential to prevent major neurological and cardiovascular complications. Measurement of serum sodium levels will indicate a trend toward hyponatremia. We report a case in which electroencephalographic changes preceded clinical signs and symptoms of encephalopathy.

went a posterior fusion of vertebrae C5 and C6. Postoperatively, he had difficulty voiding and was discovered to have urinary tract obstruction from an enlarged prostate. On hospital day 18 he underwent transurethral resection of the prostate with spinal anesthesia. At the conclusion of the procedure the patient complained of dizziness and blurred vision. The serum sodium level was 118 mmo!./!. (see table). During transport to the recovery room he complained of difficulty with focusing of vision and severe nausea. Electroencephalography in the recovery room showed slowing of the a rhythms with diffusely intermingled e slow activity (fig. 1). At this time the serum sodium level was 123 mmo!./!. and the ammonia level was 74 /-Lmo!./!. The symptoms abated 5 hours after diuresis with furosemide. The next day electroencephalography (fig. 2) and the serum sodium level were norma!' FPI-Al

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CASE REPORT

A 62-year-old man presented to the emergency room with complaints of severe neck pain and arm weakness after a fal!. Diagnosis was C5 and C6 unilateral locked facet and he underAccepted for publication October 16, 1992.

Preoperative, intraoperative, recovery room and postoperative laboratory studies ECG

Postop. Laboratory Study

Preop. Intraop. Recovery Room Day 1

Sodium (normal 135-145 mmol./l.) Potassium (normal 3.5-5 mmol./l.) Blood urea nitrogen (normal 5-20 mg./dl.) Creatinine (normal 0.81.4 mg./dl.) Glucose (normal 65-ll0 mg./dl.) Ammonia (normalll-35 I'mol./l.) Electroencephalography Anion gap (normal 5-15 mmol./l.)

137 4.4 17 0.9 125

ll8 5.4 14 0.8 99

123 5.3 15 0.9 99 74

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FIG. 1. Electroencephalogram done in recovery room shows slowing of a activity (arrows). Approximately 5 Hz. diffuse 0 activity is mixed with background rhythms (arrowheads).

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FIG. 2. Electroencephalogram 18 hours later shows normal a activity (arrows).

DISCUSSION

The transurethral resection syndrome, comprised of central nervous system and cardiovascular alterations, occurs when the serum sodium level decreases by 15 to 20 mmol./I. Obtundation is nearly always present when the sodium level decreases to 120 mmol./!. or less. Although the patient may be alert and oriented during the operation, coma may develop within a few hours. 5 The margin of tolerance of the brain as detected by the appearance of electroencephalographic alterations is narrow when hyponatremia develops.6 A 10% decrease in sodium may

HYPOj\JATR£IVIIA

1145

be followed within a few hours substantia! electroencephalographic changes. Although parameters measured in the peripheral blood may indicate trend, these parameters do not necessarily parallel metabolic changes in the brain. When our patient became symptomatic with dizziness, blurred vision and nausea electroencephalography showed diffuse slowing in the absence of clinical signs of encephalopathy. It is likely that the symptoms experienced by the patient were secondary to glycine toxicity in the presence of hyponatremia. Although the ammonia level was elevated, changes in electroencephalography from hyperammonemia are expected only when blood ammonia levels reach 117 /-Lmo!./L (200 /-Lg.jdl.) or more.? A number of studies correlate electroencephalographic changes and hyponatremia. However, to our knowledge there are no studies that monitored electroencephalography during transurethral resection of the prostate to detect hyponatremia and encephalopathy secondary to water intoxication during transurethral resection of the prostate. This is especially true for awake patients during spinal anesthesia. A prospective electroencephalographic study of patients undergoing transurethral resection of the prostate is warranted. Ms. Linda Link provided technical assistance. REFERENCES

1. Jensen, V.: The TURP syndrome. Canad. J. Anaesth., 38: 90,1991. 2. Hoekstra, P. T., Kahnoski, R., McCamish, M. A., Bergen, W. and Heetderks, D. R.: Transurethral prostatic resection syndromea new perspective: encephalopathy with associated hyperammonemia. J. Urol., 130: 704, 1983. 3. Kay, M. C., Kay, J., Begun, F. and Yeung, J. E.: Vision loss following transurethral resection of the prostate. J. Clin. Neurol. Ophthalmol., 5: 273, 1985. 4. Creel, D. J., Wang, J. M. and Wong, K. C.: Transient blindness associated with transurethral resection of the prostate. Arch. Ophthalmol., 105: 1537, 1987. 5. Henderson, D. J. and Middleton, R. G.: Coma from hyponatremia following transurethral resection of prostate. Urology, 15: 267, 1980. 6. Pampiglione, G.: The effect ofmetaholic disorders on brain activity. J. Roy. ColI. Phys. Lond., 7: 347, 1973. 7. Kiloh, L. G., McComas, A. J., Osselton, J. W. and Upton, A.: Clinical EEG, 4th ed. Woburn, Massachusetts: Butterworths, p. 180, 1981.