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Anesthetic management of a parturient with cerebellopontine-angle meningioma
International Journal of Obstetric Anesthesia (2002) 11, 219–221 ° C 2002 Published by Elsevier Science Ltd. doi:10.1054/ijoa.2001.0941, available online http://www.idealibrary.com on
CASE REPORT
Anesthetic management of a parturient with cerebellopontine-angle meningioma N. Bharti, L. Kashyap, V. K. Mohan Indian Institute of Medical Sciences, New Delhi, India SUMMARY. Cerebellopontine-angle meningioma is a rare intracranial neoplasm. It presents a difficult problem in pregnancy. A 27-year-old multigravida presented with headache, vomiting and visual disturbances at 30 weeks’ gestation and cerebellopontine angle meningioma and hydrocephalus were diagnosed. A ventriculoperitoneal shunt was placed under general anesthesia to reduce the symptoms of raised intracranial pressure and to prevent the risk of cerebellar herniation. At 32 weeks a cesarean section was performed under general anesthesia and a healthy baby delivered. A smooth induction and maintenance of anesthesia along with lidocaine and mannitol were used to prevent a rise in intracranial pressure. The intraoperative and postoperative course was uneventful. Thus, immediate neurosurgical decompression improved the patient’s condition, and allowed time for fetal maturity and uneventful delivery by cesarean C 2002 Published by Elsevier Science Ltd. section under general anesthesia. °
of the conflicting requirements of neuroanesthesia and obstetric anesthesia. A smooth induction and adequate depth of anesthesia are necessary to prevent a rise in ICP, but for the safety of the fetus it is often thought that minimal drug should be administered before delivery. Anesthesia is a reversible process, so should not do lasting damage to the fetus; light anesthesia, on the other hand, risks stressing the mother, which is bad for the fetus. We report here anesthetic management of a patient with cerebellopontineangle meningioma and increased intracranial pressure during the pregnancy.
INTRODUCTION Primary brain tumors are uncommon during pregnancy and meningioma is even rarer.1–3 The management of a parturient with an intracranial tumor is a challenge to anesthesiologists, obstetricians and neurosurgeons. During pregnancy, intracranial tumors may become symptomatic or there may be aggravation of presenting signs and symptoms.2,3 A large cerebellopontine-angle meningioma can compress brain stem structures and may be fatal if not treated immediately.4 In the management of such patients, judging the best time for neurological studies, surgical intervention, interruption of pregnancy and mode of delivery is difficult and occasionally controversial. Labor and bearing-down may increase intracranial pressure (ICP) and cause neurological deterioration in a rapidly growing tumor. The choice of anesthetic technique depends upon the status of the fetus, the type and location of the tumor, the neurological condition of the mother and the urgency of surgery. It is an anesthetic challenge because
CASE REPORT A 27-year-old multigravida presented at 30 weeks’ gestation with generalised headache, vertigo and hearing impairment for five months. Her symptoms worsened over a period of one month with blurring of vision and vomiting. Past medical and obstetric history was unremarkable except that she had occasional generalized headache over the preceding ten months, which increased on bending forward and straining during defecation. She weighed 45 kg and her height was 152 cm. The gestational age of fetus was 30 weeks and the fetal heart rate was 136 beats per min (bpm). On clinical examination, the maternal heart rate was 68 bpm and the blood pressure 140/90 mmHg. Respiratory and cardiovascular systems were clinically normal. The Glasgow Coma Scale was 15. She had mental confusion and difficulty in voice discrimination. Sensation was decreased over the right
Accepted December 2001 N. Bharti, Senior Resident, L. Kashyap, Associate Professor, V. K. Mohan, Assistant Professor, Department of Anesthesiology and Intensive Care, All India Institute of Medical Sciences, New Delhi-110029, India. Correspondence to: Dr Lokesh Kashyap, Associate Professor of Anesthesiology, A-1/250 Safdarjung Enclave, New Delhi-110029, India. Fax: 91-11-6862663, 6521041; E-mail: [email protected] 219
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International Journal of Obstetric Anesthesia
forehead and cheek. The corneal reflex in the right eye and the right extensor planter reflex were absent. The patient had a right-sided sensory neural deafness, ataxia and dysdiadochokinesia. There was bilateral papilledema and vision in the right eye was 6/24. On laboratory evaluation the hemoglobin was 10.8 mg/dL and there was no biochemical evidence of hepatic or renal disorder. A computerized axial tomography scan (CT scan) revealed a leftsided large cerebellopontine-angle meningioma with hydrocephalus. Dexamethasone 8 mg was given i.v. and a left ventriculoperitoneal shunt placement was planned under general anesthesia to decrease ICP. After preoxygenation and rapid sequence induction with thiopentone 250 mg, lidocaine 100 mg and vecuronium 5 mg, the trachea was intubated. Anesthesia was maintained with isoflurane 1% and 50% nitrous oxide in oxygen, vecuronium and meperidine 40 mg. The lungs were ventilated to maintain an end-tidal carbon dioxide (EtCO2 ) of 25 mmHg. Mannitol 50 g was given intraoperatively. Monitoring included electrocardiogram, invasive blood pressure, oxygen saturation (SaO2 ), EtCO2, fetal heart rate, urine output and blood loss. The fetal heart rate was monitored intraoperatively and the mother’s mean blood pressure was maintained above 90 mmHg to maintain cerebral perfusion pressure and uterine blood flow. The intraoperative course was uneventful. The trachea was extubated after reversal of neuromuscular paralysis with neostigmine 2.5 mg and atropine 1 mg. Postoperatively the patient was given prednisolone 10 mg 8-hourly and phenytoin 300 mg orally once a day. After placement of the ventriculoperitoneal shunt the mother’s clinical condition improved, but at 32 weeks’ gestation she became disoriented and confused, therefore the neurologists and obstetrician planned a cesarean section. The patient was given oral phenytoin 300 mg at night. Ranitidine 50 mg, dexamethasone 8 mg and metoclopramide 10 mg were given i.v. before surgery. The preoperative heart rate was 88 bpm and the blood pressure 120/80 mmHg. The patient was positioned supine with lateral tilt to prevent aorto-caval compression. Non-invasive blood pressure, pulse oximetry and electrocardiogram were monitored. The patient was given 100% oxygen for 3 min. The trachea was intubated after rapid sequence induction with thiopentone 250 mg and vecuronium 5 mg i.v. using the priming principle. Anesthesia was maintained with nitrous oxide 50% and isoflurane 0.5–1% using a semi-closed circuit. During surgery the maternal heart rate varied between 88 and 104 bpm and the blood pressure between 110/70 and 150/90 mmHg. EtCO2 was maintained at 28–32 mmHg. A healthy female baby, weighing 2.35 kg was delivered 8 min after induction of anesthesia. Her Apgar scores were 7 at 1 min and 9 at 5 min. After delivery of the baby a 5-unit bolus of Syntocinon was followed by a 15-unit infusion. Meperidine 25 mg was given i.v. for analgesia. The blood loss was 200 mL. At the
end of surgery, the trachea was extubated after reversal of neuromuscular blockade with neostigmine 2.5 mg and atropine 1.2 mg. The patient was transferred to the recovery room and monitored for 24 h. Her postoperative vital signs were stable. Diclofenac 75 mg was given i.m. 8-hourly for postoperative analgesia. On the third postoperative day she developed an upper respiratory tract infection that was treated with antibiotics. She was discharged after seven days. She was advised to take phenytoin 300 mg orally once a day. Radiation therapy was planned for further management of the meningioma. DISCUSSION Tumors like meningiomas, gliomas and neurinomas may enlarge and show accelerated growth during pregnancy.3 Meningiomas have steroid receptors and their enlargement during pregnancy is secondary to intracellular fluid retention and engorgement of intratumoral vasculature.5 The nonspecific symptoms of brain tumors such as headache, nausea and vomiting must be differentiated from common headache and morning sickness of pregnancy. A thorough neurological examination followed by CT scan, magnetic resonance imaging and isotope scanning help to confirm the diagnosis. The management of a brain tumor during pregnancy depends on location, histological type of tumor, neurological condition of the mother and gestational age of the fetus. If possible, surgery should be avoided until delivery of the baby. When absolutely necessary, surgery can be performed with extreme caution.6 In this patient the tumor was big and excision could have endangered the life of mother and fetus. Thus, a ventriculoperitoneal shunt was established to reduce ICP and radiotherapy was planned after delivery of the baby. Corticosteroids and mannitol were administered to control cerebral edema. Corticosteroids also accelerate fetal lung maturation by stimulating the lecithin-sphingomyelin index and have been found to be safe for the fetus.7 Phenytoin was started after placement of the ventriculoperitoneal shunt to prevent convulsions, which may cause fetal hypoxia and acidosis. An increase in ICP should be avoided in these patients. Therefore a rapid sequence induction was performed without the use of succinylcholine, which may increase ICP. Lidocaine and mannitol were used intravenously during ventriculoperitoneal shunt placement to prevent a rise in ICP. Hyperventilation to maintain a PaCO2 of 25–30 mmHg is necessary to decrease ICP but it may be harmful for the fetus as it may decrease uteroplacental perfusion. Isoflurane is beneficial in neurosurgical procedures because it reduces cerebral metabolic rate and oxygen consumption (CMRO2 ) and therefore cerebral ischemia is better tolerated.8 Meticulous monitoring of
Cerebellopontine-angle meningioma mother and fetus is important. A timely cesarean section is necessary as fetal well-being is ultimately dependent on the health of the mother. General anesthesia remains a safe and reliable method for operative delivery in parturients with intracranial neoplasms.9,10 During general anesthesia hemodynamic parameters, ICP and hypocarbia can be well controlled. The disadvantages of general anesthesia are the risk of unexpected difficult airway, pulmonary aspiration and increase in blood pressure and ICP during induction or emergence from anesthesia. Use of regional anesthesia in a patient with a brain tumor is controversial. It has been mainly used for labor analgesia. Epidural anesthesia in these patients carries the risk of increasing ICP following local anesthetic injection into the epidural space. Also, inadvertent dural puncture may be fatal in patients with increased ICP.11,12 Cerebellopontine-angle meningioma is rare during pregnancy. It constitutes a difficult problem requiring a multidisciplinary approach. The management has to be individualized according to the patient’s signs and symptoms and the duration of pregnancy. In a parturient with a large tumor and signs of increased ICP or focal neurological signs, a ventriculoperitonial shunt can reduce intracranial pressure. An elective cesarean section should preferably be done under general anesthesia after the fetus has attained maturity. ACKNOWLEDGEMENTS Thanks to Dr Vatsala from the Department of Obstetrics and Gynecology and the members of the Department of Neurosurgery for
221
their assistance and contribution in the sections related to their speciality
REFERENCES 1. Isla A, Alvarez F, Gangalez A, Garcia-Grande A, Perez-Alvarez M, Garcia-Blazquez M. Brain tumor and pregnancy. Obstet Gynecol 1997; 89: 19–23. 2. Haas J F, Janisch W, Staneczek W. Newly diagnosed primary intracranial neoplasms in pregnant women: a population-based assessment. J Neurol Neurosurg Psychiatry 1986; 49: 874– 880. 3. Roelvink N C, Kamphorst W, Van Alphen H A, Rao B R. Pregnancy related primary brain and spinal tumours. Arch Neurol 1987; 44: 209–215. 4. Goldstein P J, Rosenberg S, Smith R W. Maternal death and brain tumor: case report. Am J Obstet Gynecol 1972; 112: 297–298. 5. Benzel E C, Gelder F B. Correlation between sex hormone binding and peritumoral edema in intracranial meningiomas. Neurosurg 1988; 23: 169–174. 6. Giannini A, Bricchi M. Posterior fossa surgery in the sitting position in a pregnant patient with cerebellopontine angle meningioma. Br J Anaesth 1999; 82: 941–944. 7. NIH Consensus Development Conference Statement: Effect of corticosteroids for fetal maturation on perinatal outcomes. Am J Obstet Gynecol 1995; 173: 246–253. 8. Madsen J B, Cold G E, Hansen E S, Bardrum B. The effect of isoflurane on during craniotomy for small supratentorial cerebral tumors. Anesthesiology 1987; 66: 332–336. 9. Chang L, Looi-Lyons L, Bartosik L, Tindal S. Anesthesia for cesarean section in two patients with brain tumours. Can J Anaesth 1999; 46: 61–65. 10. Bedard J M, Richardson M G, Wissler R N. General anesthesia with remifemtanil for cesarean section in a parturient with an acoustic neuroma. Can J Anaesth 1999; 46: 576–580. 11. Finfer S R. Management of labour and delivery in patients with intracranial neoplasms. Br J Anaesth 1991; 67: 784–787. 12. Hilt H, Gramm H J, Link J. Changes in intracranial pressure associated with extradural anaesthesia. Br J Anaesth 1986; 58: 676–680.
CASE REPORT
Anesthetic management of a parturient with cerebellopontine-angle meningioma N. Bharti, L. Kashyap, V. K. Mohan Indian Institute of Medical Sciences, New Delhi, India SUMMARY. Cerebellopontine-angle meningioma is a rare intracranial neoplasm. It presents a difficult problem in pregnancy. A 27-year-old multigravida presented with headache, vomiting and visual disturbances at 30 weeks’ gestation and cerebellopontine angle meningioma and hydrocephalus were diagnosed. A ventriculoperitoneal shunt was placed under general anesthesia to reduce the symptoms of raised intracranial pressure and to prevent the risk of cerebellar herniation. At 32 weeks a cesarean section was performed under general anesthesia and a healthy baby delivered. A smooth induction and maintenance of anesthesia along with lidocaine and mannitol were used to prevent a rise in intracranial pressure. The intraoperative and postoperative course was uneventful. Thus, immediate neurosurgical decompression improved the patient’s condition, and allowed time for fetal maturity and uneventful delivery by cesarean C 2002 Published by Elsevier Science Ltd. section under general anesthesia. °
of the conflicting requirements of neuroanesthesia and obstetric anesthesia. A smooth induction and adequate depth of anesthesia are necessary to prevent a rise in ICP, but for the safety of the fetus it is often thought that minimal drug should be administered before delivery. Anesthesia is a reversible process, so should not do lasting damage to the fetus; light anesthesia, on the other hand, risks stressing the mother, which is bad for the fetus. We report here anesthetic management of a patient with cerebellopontineangle meningioma and increased intracranial pressure during the pregnancy.
INTRODUCTION Primary brain tumors are uncommon during pregnancy and meningioma is even rarer.1–3 The management of a parturient with an intracranial tumor is a challenge to anesthesiologists, obstetricians and neurosurgeons. During pregnancy, intracranial tumors may become symptomatic or there may be aggravation of presenting signs and symptoms.2,3 A large cerebellopontine-angle meningioma can compress brain stem structures and may be fatal if not treated immediately.4 In the management of such patients, judging the best time for neurological studies, surgical intervention, interruption of pregnancy and mode of delivery is difficult and occasionally controversial. Labor and bearing-down may increase intracranial pressure (ICP) and cause neurological deterioration in a rapidly growing tumor. The choice of anesthetic technique depends upon the status of the fetus, the type and location of the tumor, the neurological condition of the mother and the urgency of surgery. It is an anesthetic challenge because
CASE REPORT A 27-year-old multigravida presented at 30 weeks’ gestation with generalised headache, vertigo and hearing impairment for five months. Her symptoms worsened over a period of one month with blurring of vision and vomiting. Past medical and obstetric history was unremarkable except that she had occasional generalized headache over the preceding ten months, which increased on bending forward and straining during defecation. She weighed 45 kg and her height was 152 cm. The gestational age of fetus was 30 weeks and the fetal heart rate was 136 beats per min (bpm). On clinical examination, the maternal heart rate was 68 bpm and the blood pressure 140/90 mmHg. Respiratory and cardiovascular systems were clinically normal. The Glasgow Coma Scale was 15. She had mental confusion and difficulty in voice discrimination. Sensation was decreased over the right
Accepted December 2001 N. Bharti, Senior Resident, L. Kashyap, Associate Professor, V. K. Mohan, Assistant Professor, Department of Anesthesiology and Intensive Care, All India Institute of Medical Sciences, New Delhi-110029, India. Correspondence to: Dr Lokesh Kashyap, Associate Professor of Anesthesiology, A-1/250 Safdarjung Enclave, New Delhi-110029, India. Fax: 91-11-6862663, 6521041; E-mail: [email protected] 219
220
International Journal of Obstetric Anesthesia
forehead and cheek. The corneal reflex in the right eye and the right extensor planter reflex were absent. The patient had a right-sided sensory neural deafness, ataxia and dysdiadochokinesia. There was bilateral papilledema and vision in the right eye was 6/24. On laboratory evaluation the hemoglobin was 10.8 mg/dL and there was no biochemical evidence of hepatic or renal disorder. A computerized axial tomography scan (CT scan) revealed a leftsided large cerebellopontine-angle meningioma with hydrocephalus. Dexamethasone 8 mg was given i.v. and a left ventriculoperitoneal shunt placement was planned under general anesthesia to decrease ICP. After preoxygenation and rapid sequence induction with thiopentone 250 mg, lidocaine 100 mg and vecuronium 5 mg, the trachea was intubated. Anesthesia was maintained with isoflurane 1% and 50% nitrous oxide in oxygen, vecuronium and meperidine 40 mg. The lungs were ventilated to maintain an end-tidal carbon dioxide (EtCO2 ) of 25 mmHg. Mannitol 50 g was given intraoperatively. Monitoring included electrocardiogram, invasive blood pressure, oxygen saturation (SaO2 ), EtCO2, fetal heart rate, urine output and blood loss. The fetal heart rate was monitored intraoperatively and the mother’s mean blood pressure was maintained above 90 mmHg to maintain cerebral perfusion pressure and uterine blood flow. The intraoperative course was uneventful. The trachea was extubated after reversal of neuromuscular paralysis with neostigmine 2.5 mg and atropine 1 mg. Postoperatively the patient was given prednisolone 10 mg 8-hourly and phenytoin 300 mg orally once a day. After placement of the ventriculoperitoneal shunt the mother’s clinical condition improved, but at 32 weeks’ gestation she became disoriented and confused, therefore the neurologists and obstetrician planned a cesarean section. The patient was given oral phenytoin 300 mg at night. Ranitidine 50 mg, dexamethasone 8 mg and metoclopramide 10 mg were given i.v. before surgery. The preoperative heart rate was 88 bpm and the blood pressure 120/80 mmHg. The patient was positioned supine with lateral tilt to prevent aorto-caval compression. Non-invasive blood pressure, pulse oximetry and electrocardiogram were monitored. The patient was given 100% oxygen for 3 min. The trachea was intubated after rapid sequence induction with thiopentone 250 mg and vecuronium 5 mg i.v. using the priming principle. Anesthesia was maintained with nitrous oxide 50% and isoflurane 0.5–1% using a semi-closed circuit. During surgery the maternal heart rate varied between 88 and 104 bpm and the blood pressure between 110/70 and 150/90 mmHg. EtCO2 was maintained at 28–32 mmHg. A healthy female baby, weighing 2.35 kg was delivered 8 min after induction of anesthesia. Her Apgar scores were 7 at 1 min and 9 at 5 min. After delivery of the baby a 5-unit bolus of Syntocinon was followed by a 15-unit infusion. Meperidine 25 mg was given i.v. for analgesia. The blood loss was 200 mL. At the
end of surgery, the trachea was extubated after reversal of neuromuscular blockade with neostigmine 2.5 mg and atropine 1.2 mg. The patient was transferred to the recovery room and monitored for 24 h. Her postoperative vital signs were stable. Diclofenac 75 mg was given i.m. 8-hourly for postoperative analgesia. On the third postoperative day she developed an upper respiratory tract infection that was treated with antibiotics. She was discharged after seven days. She was advised to take phenytoin 300 mg orally once a day. Radiation therapy was planned for further management of the meningioma. DISCUSSION Tumors like meningiomas, gliomas and neurinomas may enlarge and show accelerated growth during pregnancy.3 Meningiomas have steroid receptors and their enlargement during pregnancy is secondary to intracellular fluid retention and engorgement of intratumoral vasculature.5 The nonspecific symptoms of brain tumors such as headache, nausea and vomiting must be differentiated from common headache and morning sickness of pregnancy. A thorough neurological examination followed by CT scan, magnetic resonance imaging and isotope scanning help to confirm the diagnosis. The management of a brain tumor during pregnancy depends on location, histological type of tumor, neurological condition of the mother and gestational age of the fetus. If possible, surgery should be avoided until delivery of the baby. When absolutely necessary, surgery can be performed with extreme caution.6 In this patient the tumor was big and excision could have endangered the life of mother and fetus. Thus, a ventriculoperitoneal shunt was established to reduce ICP and radiotherapy was planned after delivery of the baby. Corticosteroids and mannitol were administered to control cerebral edema. Corticosteroids also accelerate fetal lung maturation by stimulating the lecithin-sphingomyelin index and have been found to be safe for the fetus.7 Phenytoin was started after placement of the ventriculoperitoneal shunt to prevent convulsions, which may cause fetal hypoxia and acidosis. An increase in ICP should be avoided in these patients. Therefore a rapid sequence induction was performed without the use of succinylcholine, which may increase ICP. Lidocaine and mannitol were used intravenously during ventriculoperitoneal shunt placement to prevent a rise in ICP. Hyperventilation to maintain a PaCO2 of 25–30 mmHg is necessary to decrease ICP but it may be harmful for the fetus as it may decrease uteroplacental perfusion. Isoflurane is beneficial in neurosurgical procedures because it reduces cerebral metabolic rate and oxygen consumption (CMRO2 ) and therefore cerebral ischemia is better tolerated.8 Meticulous monitoring of
Cerebellopontine-angle meningioma mother and fetus is important. A timely cesarean section is necessary as fetal well-being is ultimately dependent on the health of the mother. General anesthesia remains a safe and reliable method for operative delivery in parturients with intracranial neoplasms.9,10 During general anesthesia hemodynamic parameters, ICP and hypocarbia can be well controlled. The disadvantages of general anesthesia are the risk of unexpected difficult airway, pulmonary aspiration and increase in blood pressure and ICP during induction or emergence from anesthesia. Use of regional anesthesia in a patient with a brain tumor is controversial. It has been mainly used for labor analgesia. Epidural anesthesia in these patients carries the risk of increasing ICP following local anesthetic injection into the epidural space. Also, inadvertent dural puncture may be fatal in patients with increased ICP.11,12 Cerebellopontine-angle meningioma is rare during pregnancy. It constitutes a difficult problem requiring a multidisciplinary approach. The management has to be individualized according to the patient’s signs and symptoms and the duration of pregnancy. In a parturient with a large tumor and signs of increased ICP or focal neurological signs, a ventriculoperitonial shunt can reduce intracranial pressure. An elective cesarean section should preferably be done under general anesthesia after the fetus has attained maturity. ACKNOWLEDGEMENTS Thanks to Dr Vatsala from the Department of Obstetrics and Gynecology and the members of the Department of Neurosurgery for
221
their assistance and contribution in the sections related to their speciality
REFERENCES 1. Isla A, Alvarez F, Gangalez A, Garcia-Grande A, Perez-Alvarez M, Garcia-Blazquez M. Brain tumor and pregnancy. Obstet Gynecol 1997; 89: 19–23. 2. Haas J F, Janisch W, Staneczek W. Newly diagnosed primary intracranial neoplasms in pregnant women: a population-based assessment. J Neurol Neurosurg Psychiatry 1986; 49: 874– 880. 3. Roelvink N C, Kamphorst W, Van Alphen H A, Rao B R. Pregnancy related primary brain and spinal tumours. Arch Neurol 1987; 44: 209–215. 4. Goldstein P J, Rosenberg S, Smith R W. Maternal death and brain tumor: case report. Am J Obstet Gynecol 1972; 112: 297–298. 5. Benzel E C, Gelder F B. Correlation between sex hormone binding and peritumoral edema in intracranial meningiomas. Neurosurg 1988; 23: 169–174. 6. Giannini A, Bricchi M. Posterior fossa surgery in the sitting position in a pregnant patient with cerebellopontine angle meningioma. Br J Anaesth 1999; 82: 941–944. 7. NIH Consensus Development Conference Statement: Effect of corticosteroids for fetal maturation on perinatal outcomes. Am J Obstet Gynecol 1995; 173: 246–253. 8. Madsen J B, Cold G E, Hansen E S, Bardrum B. The effect of isoflurane on during craniotomy for small supratentorial cerebral tumors. Anesthesiology 1987; 66: 332–336. 9. Chang L, Looi-Lyons L, Bartosik L, Tindal S. Anesthesia for cesarean section in two patients with brain tumours. Can J Anaesth 1999; 46: 61–65. 10. Bedard J M, Richardson M G, Wissler R N. General anesthesia with remifemtanil for cesarean section in a parturient with an acoustic neuroma. Can J Anaesth 1999; 46: 576–580. 11. Finfer S R. Management of labour and delivery in patients with intracranial neoplasms. Br J Anaesth 1991; 67: 784–787. 12. Hilt H, Gramm H J, Link J. Changes in intracranial pressure associated with extradural anaesthesia. Br J Anaesth 1986; 58: 676–680.