- Consider Avoiding Alfentanil (Increased ICP possible)
- Assess VP shunt (ask about headache, vision, cough etc); if concerned speak to neurosurgeons.
- Local Anaesthetic if possible?
Adult Spina Bifida in Anaesthesia - click here (Anaesthesia)
A 17-year-old A-level student with spina bifida aperta coned and died after general anaesthesia (GA) for cystoscopy. The case provides invaluable lessons.
Pre-operative assessment in the day unit revealed an anxious, obese girl of short stature with thoracic kyphoscoliosis. She was born with a large, inoperable, open spina bifida aperta and a ventriculo-peritoneal (VP) shunt had been inserted during infancy. Her past case notes were unavailable. In the operating theatre, intravenous access was difficult and the injected propofol tissued. She therefore received a gas induction with sevoflurane under full standard monitoring. She was breathing spontaneously through a laryngeal mask. She was placed in the lithotomy position, and the cystoscopy lasted less than 10 min. Oxygen saturation was 97%, end-tidal CO2 was 7 kPa and systolic blood pressure was 85 mmHg throughout the procedure. However, in the recovery area she suddenly coned and died. A post-mortem revealed cerebrospinal fluid (CSF) under high pressure and an Arnold–Chiari malformation. The posterior cranial fossa was very small and the brain had herniated through a large foramen magnum. The ventricular end of the shunt was outside the brain tissue. There was no pumping chamber on the VP shunt.
The term spina bifida includes a group of developmental anomalies  that result from defects in neural tube closure. Spina bifida occulta is generally an incidental finding in which only a bony defect is present. The meningocele has a meningeal sac but intact neural elements. Spina bifida cystica (myelomeningocele) has a skin-covered intact sac containing neural elements. In spina bifida aperta, the skin is open. The high incidence of spina bifida noted in the United Kingdom  in 1982 has steadily declined since folic acid supplementation in the maternal diet was introduced. Spina bifida may be associated with CNS anomalies such as hydrocephalus and Arnold–Chiari malformation. There is a high incidence of neurovesical dysfunction in these patients requiring repeat catheterisation. Nearly 69% of patients with spina bifida require urological assessment, care and follow-up . Cystoscopic procedures for these patients are often carried out in day theatres.
In this fatal case, the patient had been asymptomatic despite the nonfunctioning shunt. If a patient is shunt dependent once, he or she usually remains shunt dependent for life. Shunt independence should not be assumed .
The Arnold–Chiari malformation was only evident at post-mortem in this patient. The essential feature of this malformation is an elongation of the cerebellar vermis with herniation of its caudal extreme through the foramen magnum. Development of the surrounding skull during early childhood is influenced by the need to accommodate the displaced contents of the posterior fossa. Arnold–Chiari malformation would facilitate herniation of the brain contents through the foramen magnum as it is enlarged and the overall volume of the posterior fossa is diminished. Every patient with myelomeningocele has some degree of Arnold–Chiari malformation , though not always symptomatic. Hydrocephalus is commonly associated with the Arnold–Chiari malformation.
This patient most certainly coned towards the end of the procedure due to rising intracranial pressure and reduced cerebral perfusion. Spontaneous respiration under GA, the nonfunctioning shunt and the Arnold–Chiari malformation all contributed to the herniation. A fibreoptic cystoscopy under local anaesthesia could have avoided the complication of the GA. In the absence of any sensations below the hip, this could have been done under simple sedation. However, one must be aware of autonomic dysreflexia in a patient with a chronic spinal lesion . A short general anaesthesia would be the first choice of most anaesthetists for such a short procedure, particularly when the patient is anxious and tense. Intubation and controlled ventilation would help control Paco2 and ICP. Alfentanil  is known to raise ICP and is best avoided.
All patients with VP shunt require neurosurgical review and a CT scan before their GA if their shunt status is not known. A poor history and lack of neurosurgical follow-up must be an indication for neurosurgical referral. This is recommended even for asymptomatic patients coming in for short procedures under GA. A neurosurgeon would be able to assess the shunt and if required insert a new one. A poorly assessed shunt could be a death trap and a hurried GA is not advised.
Article Here (Anaesthesia)
The letter by Dr Radhakrishna (Radhakrishna. Anaesthesia 2000; 55: 295–6) highlighted several problems of anaesthesia in adult spina bifida patients, in particular the need for vigilance when congenital hydrocephalus has been treated by a shunt, even if performed many years previously. Sudden death has been previously reported in these patients , and the death reported in the letter may well have been unrelated to anaesthesia.
Long-term survival of spina bifida patients is not normal, the Cambridge database suggesting a reduced life expectancy of 79% survival at 1 year, but only 50% survival at age 30 years . Renal failure is a major factor, and several patients are now having renal transplants.
Anaesthesia for adult spina bifida patients is particularly demanding, and has recently been reviewed . Although autonomic hyper reflexia has been reported in 85% of spinal cord injury patients with levels of T4 and above , it is virtually unheard of in spina bifida patients, presumably because the lesions are usually more caudad than this, and also because initial surgery to above the myelomeningocoele defect may damage the nervous tissue, preventing such reflexes.
Assessing the function of hydrocephalus shunts may not be easy clinically, although any change in behaviour or performance, especially if associated with headaches, needs further investigation. Examination of the optic discs via an ophthalmoscope is one simple screening test if the patient is co-operative, and may help in the selection of those patients who need referral. It has been said before that all people with a shunt to control hydrocephalus and chronic neurological problems must receive continuing comprehensive medical cover . Sadly, many have not received this since leaving the support of children's hospitals. Anaesthetists beware.
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