Fiberoptic Intubation And Monitoring Of Somatosensory Evoked Potentials In Children With Mucopolysaccharidoses

Abstract

The management of children with mucopolysaccharidosis (MPS) is a challenge for the anesthesiologist, primarily because of difficult airways. Furthermore, cert ain types of MPS (I,VI, VII) are at risk for cervical spine compression. Theref ore, we recommend monitoring of somatosensory potentials during intubation and during positioning of these patient for surgery. Two case reports are presented to demonstrate the perioperative management. Water intoxication (restlessness, frothing, retching, tremor and twitching of muscles) was first described by Wier et al. in 1922 (1). In 1998 we are still diagnosing and treating iatrogenic water intoxication described as TURP Syndrome. The presented case describes a typical TURP syndrome, which was diagnosed early, treated aggressively, and which led to a good outcome for the patient. Transurethral resection of the prostate consists of removal of prostatic tissue by means of electro-cautery. The electrocautery wire loop is positioned in the patient’s urethra through a special sheath. The surgical field is visualized through a scope. Irrigation solution is used to distend the bladder, clear the surgical site, and remove blood and resected tissue. Normal saline cannot be used as irrigation solution because the dissemination of the electric current would be dangerous to both, surgeon and patient. A variety of irrigation solutions have been used in the past. 80 min into the case the patient was noted to be markedly hypothermic. This may reflect the large amount of cold solute absorbed by the patient and confirmed by the Na measurement of 109 mEq/L. A decrease in serum Na of 20-30 mEq/L (preoperative Na was 138 mEq/L) implies absorption of 3-4 liters of fluid (dilutional hyponatremia) (2). All other vital signs remained stable. Another clue to a hypervolemic state might be hypertension and reflex bradycardia. Several factors contribute to the rapid volume expansion, namely the intravesicular pressure (governed by the height of the irrigation bag above the prostatic sinuses), the number of prostatic sinuses opened and maybe most important the duration of the surgical procedure. Surgery was terminated at this point and the patient was transferred intubated and sedated to the ICU. Figure 1 Chest X-ray at arrival SICU: Slightly incresed pulmonary vasculature suggesting fluid overload. Fiberoptic Intubation And Monitoring Of Somatosensory Evoked Potentials In Children With Mucopolysaccharidoses 2 of 4 Figure 2 EKG at arrival SICU: Sinus bradycardia of 52 bpm without QTor STabnormalities The patient was still intubated and sedated. Therefore, we were unable to assess his neurological function, but we can assume that secondary to his profound hyponatremia, hypoosmolality and high ammonia levels he would have had some neurological abnormality. Some anesthesiologists and urologists would prefer regional (epidural or spinal anesthesia) compared to general anesthesia in order to early recognize mental changes in their awake patients. Neurologic changes (confusion, agitation, or other mental changes) are among the first clinical signs of water intoxication. Early recognition and early treatment of a TURP syndrome is an extremely important factor in its therapy. Neurological symptoms vary through a spectrum from mild confusion and encephalopathy through to seizures and coma. The neurological effects may result from cerebral edema associated with acute hypotonicity or from toxicity of glycine. If glycine concentrations are 30 times the normal value, visual impairment may occur (2). Visual impairment also ranges across a spectrum from blurred vision through blindness, as glycine is a major inhibitory neurotransmitter in the retina (3). Our patient did exhibit some confusion and agitation after awakening. This resolved completely within 48 hours. No visual impairment was noted. The patient was extubated after 24 hours. The vital signs were stable, the lung clear to bilateral auscultation, and the chest x ray negative for pulmonary edema. Figure 3 Chest X-ray after 24 hours in SICU: