- Email: [email protected]
Use of spontaneous ventilation to monitor the effects of posterior fossa surgery in the sitting position
968
Case Reports / Journal of Clinical Neuroscience 16 (2009) 968–969
the lower limbs. He also described intermittent double vision, typically precipitated by prolonged periods of reading. Examination revealed a right-sided ptosis (no diplopia) with a positive Cogan’s sign, and proximal fatigability in all limbs (Myasthenia Gravis Foundation of America Class IIIa). Subsequent testing confirmed the presence of AChRabs. Repetitive stimulation of trapezius and abductor digiti minimi revealed abnormal decrement, up to 86%, consistent with a diagnosis of MG (Fig. 2). CT scans with intravenous contrast failed to show recurrence of the tumour within the neck or thorax. The patient’s symptoms improved with institution of pyridostigmine treatment. 3. Discussion The exact mechanisms that trigger the onset of MG after thymectomy remain uncertain. Long-lived functional lymphocytes might be released intraoperatively,3 or ectopic thymic tissue, found in 20% of humans,2 continues to be the focus of autoimmune reactions. However, the existence of residual thymic tissue following incomplete surgery, and the possibility of tumour recurrence, need to be ruled out. Interestingly, Tanimura et al. described a thymoma recurrence, despite extended total thymectomy for stage III disease, with the development of MG 3 months after re-excision.4 A large retrospective study by Evoli et al. identified 13 cases of post-thymectomy MG, two of whom had recurrent tumour.6 The onset of MG in the remaining 11 patients ranged from 6 months to 10 years. Pointing against recurrence in the present case are the findings that Stage II tumours are almost always resectable and recur infrequently, and that no thymoma with original histology subtype AB has ever been reported to relapse.6 In the present case, repeat structural imaging remained negative for tumour. Muscle antibodies directed against titin and ryanodine receptors may be sensitive markers of thymoma7 and may prove useful where there is diagnostic ambiguity. A small tumour in our patient might have escaped detection in the absence of a high-resolution MRI scan and testing for serological markers other than AChRabs. Nevertheless, his post-operative radiotherapy makes this unlikely. Thymomas are moderately radiosensitive and adjuvant radiotherapy can reduce recurrence of Stage II neoplasms.1
Although continued vigilance for late-onset MG, and indeed thymoma recurrence, is important in post-thymectomy patients, MG is not the only paraneoplastic condition associated with thymomas (albeit the most common). About 10% of thymoma patients will develop at least one of many other disorders including pure red cell aplasia, hypogammaglobulinaemia, glomerulonephritis and myocarditis.1,6 Thymoma patients also have a 20% risk of second malignancy, including colorectal, breast and thyroid, independent of any chemoradiotherapy for the thymoma.6,8 As such, meticulous life-long follow-up and surveillance must be encouraged post-thymectomy. Performing a battery of autoantibody screens in newly diagnosed but otherwise asymptomatic thymoma patients, however, appears of limited value as AChRabs and various other auto-antibodies may be raised anyway.9 Although no relationship has been identified between autoantibody levels and the stage or grade of thymoma, research into pre-thymomectomy auto-immune profiles and tumour histology may yet predict onset of post-operative MG or associated paraneoplastic and malignant conditions.
References 1. Thomas CR, Wright CD, Loehrer PJ. Thymoma: state of the art. J Clin Oncol 1999;17:2280–9. 2. Namba T, Brunner NG, Grob D. Myasthenia gravis in patients with thymoma, with particular reference to onset after thymectomy. Medicine 1978;57:411–33. 3. Kondo K, Monden Y. Myasthenia gravis appearing after thymectomy for thymoma. Eur J Cardiothorac Surg 2005;28:22–5. 4. Tanimura S, Tomoyasu H, Banaba J, et al. Two cases of postthymectomy myasthenia gravis. Nippon Kyobu Geka Gakkai Zasshi 1992;40:1778–83. 5. Mineo T, Biancari F, D’Andrea V. Late onset of myasthenia gravis after total resection of thymoma: report of two cases. J Cardiovasc Surg 1996;37: 531–3. 6. Evoli A, Minisci C, Di Schino C, et al. Thymoma in patients with MG. Neurology 2002;59:1844–50. 7. Romi F, Skeie GO, Aarli JA, et al. Muscle autoantibodies in subgroups of myasthenia gravis patients. J Neurol 2000;247:369–75. 8. Pan CC, Chen PC, Wang LS, et al. Thymoma is associated with an increased risk of second malignancy. Cancer 2001;92:2406–11. 9. Vernino S, Lennon VA. Autoantibody profiles and neurological correlations of thymoma. Clin Cancer Res 2004;10:7270–5.
doi:10.1016/j.jocn.2008.09.019
Use of spontaneous ventilation to monitor the effects of posterior fossa surgery in the sitting position Mihir Prakash Pandia a,*, Parmod Kumar Bithal a, Manish Singh Sharma b, Hemant Bhagat a, Bidkar Prasanna a a b
Department of Neuroanaesthesiology, Neurosciences Centre, All India Institute of Medical Sciences, New Delhi 110 029, India Department of Neurosurgery, All India Institute of Medical Sciences, New Delhi, India
a r t i c l e
i n f o
Article history: Received 7 June 2008 Accepted 21 September 2008
Keywords: Spontaneous ventilation Posterior fossa Sitting position
a b s t r a c t We describe the successful excision, guided by spontaneous ventilation, of a cervico-medullary hemangioblastoma in a 22-year-old female in the sitting position. A balanced anesthesia technique comprising an oxygen, nitrous oxide, sevoflurane, fentanyl and vecuronium mixture was used. Apart from routine monitors, electroencephalographic spectral entropy monitoring was used to determine the depth of anesthesia and transesophageal echocardiography for detection of venous air embolism. The patient remained in spontaneous ventilation for 235 min during tumor excision. The intraoperative and postoperative course were uneventful. The patient recovered without any major neurological deficit. Ó 2008 Elsevier Ltd. All rights reserved.
* Corresponding author. Tel.: + 91 98 68398203; fax: 91 11 26588663. E-mail address: [email protected] (M.P. Pandia). .
Case Reports / Journal of Clinical Neuroscience 16 (2009) 968–969
969
1. Introduction
3. Discussion
Despite the concern of complications, posterior fossa neurosurgical procedures in the sitting position are still performed in several centers because of their distinct advantages. The use of spontaneous ventilation to monitor the integrity of vital brain stem structures has been described in various posterior fossa procedures.1,2 Here we describe the successful excision, guided by spontaneous ventilation, of a hemangioblastoma involving the brain stem with the patient in the sitting position.
The only strategy to deal with a hemangioblastoma is en bloc excision after circumferential dissection and devascularisation, as even an accidental entry into the tumor substance can cause torrential hemorrhage. The decision to use spontaneous ventilation was taken to avoid a high chance of injury to vital cardiorespiratory structures during surgery. In addition, any changes in the respiratory pattern during surgery would provide the surgeon with a warning signal of any potential damage of these structures. Evoked potentials are useful in monitoring the integrity of the brainstem, but they have their own limitations.2,3 Motor evoked potentials would not have been useful in this patient as the motor tracts were located ventral to the tumor. Brainstem auditory evoked potentials would also not have been useful, as the cochlear nuclei are present in the pontomedullary junction that was superior to the tumor. The incidence of false positives is very high during somatosensory evoked potential monitoring for brainstem tumors. This may prevent the progression of surgery and thereby interfere with the complete excision of the tumor.3 There is a theoretical possibility of an increased chance of air embolism during spontaneous ventilation in sitting neurosurgical patients. However, the available literature does not support this assertion.2,4,5 With the use of TEE, air embolism can be diagnosed at an early stage and appropriate corrective steps can be taken to prevent subsequent air entrainment. Sevoflurane seems to be the ideal volatile anesthetic agent because of its distinct physical properties. Rapid adjustment of inspired concentration of sevoflurane can be made by changing the dial setting of the vaporizer, thereby maintaining a stable depth of anesthesia. Monitoring EEG spectral entropy helps to maintain a satisfactory depth of anesthesia with a lower concentration of sevoflurane.6 The maintenance of an adequate depth of anesthesia was essential to avoiding coughing and patient movement. The use of a lower concentration of sevoflurane prevented the adverse effects of a deep plane of anesthesia, such as respiratory depression and hypercarbia. We believe that spontaneous breathing has a place in the monitoring of the structural and functional integrity of the brain stem, as it can greatly assist neurophysiological monitoring. With the use of better anesthetic and monitoring techniques, complications associated with spontaneous ventilation can be averted.
2. Case report A 22-year-old female, weighing 55 kg with a cervico-medullary hemangioblastoma was scheduled for midline suboccipital craniotomy and tumor excision. The tumor was 4.5 cm 3.5 cm 3.9 cm, and was centered in a subpial location around the obex, separated from the dorsal medulla by a cyst with a large blood vessel running over its dorsal surface (Fig. 1). The patient had no other systemic illness. She was premedicated with intramuscular glycopyrrolate (0.2 mg) an hour before surgery. Anesthesia was induced with fentanyl 150 lg and sodium thiopental 350 mg. Intravenous rocuronium (60 mg) was given to facilitate endotracheal intubation. Anesthesia was maintained with 66% nitrous oxide in oxygen, sevoflurane (inspired concentration between 1.5% and 2%), fentanyl and vecuronium. Apart from routine monitors, electroencephalographic (EEG) spectral entropy monitoring was used to determine the depth of anesthesia. Transesophageal echocardiography (TEE) was used for the detection of venous air embolism (VAE). The presence of a patent foramen ovale was ruled out by TEE. Intermittent positive pressure ventilation (IPPV) was maintained until the dura was opened. During removal of the bone flap, mannitol (1 g/kg) was infused. After the dura was opened and the tumor was exposed, muscle paralysis was reversed and the patient was allowed to breathe spontaneously. Neuromuscular monitoring at this point showed a train of four ratio of >0.9. An adequate depth of anaesthesia was ensured by keeping the state and response entropy level between 40 and 60. The partial pressure of arterial carbon dioxide (PaCO2) remained between 34 mmHg and 41 mmHg during spontaneous ventilation. The duration of spontaneous ventilation was 235 min. Cardiovascular and respiratory parameters remained stable during the intraoperative period. One episode of VAE detected by TEE was managed with temporary withdrawal of nitrous oxide and aspiration of air through the subclavian catheter. The patient’s intraoperative brain condition remained excellent. After the excision of the tumor, the patient was paralyzed and put on IPPV. The estimated blood loss during the procedure was 200 mL. The patient was electively ventilated overnight and extubated the next day without any major neurological deficit except for the loss of proprioception in both upper limbs from which she recovered completely after 6 weeks. A postoperative contrast enhanced CT scan confirmed total excision of tumor. doi:10.1016/j.jocn.2008.09.019
References 1. Millar RA. Neurosurgical anaesthesia in the sitting position. A report of experience with 110 patients using controlled or spontaneous ventilation. Br J Anaesth 1971;44:495–505. 2. Manninen PH. Spontaneous ventilation is a useful monitor of brain stem function during posterior fossa surgery. J Neurosurg Anesthesiol 1995;7:63–5. 3. Wiedemayer H, Sandalcioglu IE, Armbruster W, et al. False negative findings in intraoperative SEP neurosurgical cases and review of published monitoring: analysis of 658 consecutive reports. J Neurol Neurosurg Psychiatry 2004;75:280–6. 4. Tateishi H. Prospective study of air embolism. Br J Anaesth 1972;44:1306–10. 5. Hunter AR. Air embolism in the sitting position. Anaesthesia 1962;17:467–73. 6. Aimé I, Verroust N, Masson-Lefoll C, et al. Does monitoring bispectral index or spectral entropy reduce sevoflurane use? Anesth Analg 2006;103:1469–77.
Case Reports / Journal of Clinical Neuroscience 16 (2009) 968–969
the lower limbs. He also described intermittent double vision, typically precipitated by prolonged periods of reading. Examination revealed a right-sided ptosis (no diplopia) with a positive Cogan’s sign, and proximal fatigability in all limbs (Myasthenia Gravis Foundation of America Class IIIa). Subsequent testing confirmed the presence of AChRabs. Repetitive stimulation of trapezius and abductor digiti minimi revealed abnormal decrement, up to 86%, consistent with a diagnosis of MG (Fig. 2). CT scans with intravenous contrast failed to show recurrence of the tumour within the neck or thorax. The patient’s symptoms improved with institution of pyridostigmine treatment. 3. Discussion The exact mechanisms that trigger the onset of MG after thymectomy remain uncertain. Long-lived functional lymphocytes might be released intraoperatively,3 or ectopic thymic tissue, found in 20% of humans,2 continues to be the focus of autoimmune reactions. However, the existence of residual thymic tissue following incomplete surgery, and the possibility of tumour recurrence, need to be ruled out. Interestingly, Tanimura et al. described a thymoma recurrence, despite extended total thymectomy for stage III disease, with the development of MG 3 months after re-excision.4 A large retrospective study by Evoli et al. identified 13 cases of post-thymectomy MG, two of whom had recurrent tumour.6 The onset of MG in the remaining 11 patients ranged from 6 months to 10 years. Pointing against recurrence in the present case are the findings that Stage II tumours are almost always resectable and recur infrequently, and that no thymoma with original histology subtype AB has ever been reported to relapse.6 In the present case, repeat structural imaging remained negative for tumour. Muscle antibodies directed against titin and ryanodine receptors may be sensitive markers of thymoma7 and may prove useful where there is diagnostic ambiguity. A small tumour in our patient might have escaped detection in the absence of a high-resolution MRI scan and testing for serological markers other than AChRabs. Nevertheless, his post-operative radiotherapy makes this unlikely. Thymomas are moderately radiosensitive and adjuvant radiotherapy can reduce recurrence of Stage II neoplasms.1
Although continued vigilance for late-onset MG, and indeed thymoma recurrence, is important in post-thymectomy patients, MG is not the only paraneoplastic condition associated with thymomas (albeit the most common). About 10% of thymoma patients will develop at least one of many other disorders including pure red cell aplasia, hypogammaglobulinaemia, glomerulonephritis and myocarditis.1,6 Thymoma patients also have a 20% risk of second malignancy, including colorectal, breast and thyroid, independent of any chemoradiotherapy for the thymoma.6,8 As such, meticulous life-long follow-up and surveillance must be encouraged post-thymectomy. Performing a battery of autoantibody screens in newly diagnosed but otherwise asymptomatic thymoma patients, however, appears of limited value as AChRabs and various other auto-antibodies may be raised anyway.9 Although no relationship has been identified between autoantibody levels and the stage or grade of thymoma, research into pre-thymomectomy auto-immune profiles and tumour histology may yet predict onset of post-operative MG or associated paraneoplastic and malignant conditions.
References 1. Thomas CR, Wright CD, Loehrer PJ. Thymoma: state of the art. J Clin Oncol 1999;17:2280–9. 2. Namba T, Brunner NG, Grob D. Myasthenia gravis in patients with thymoma, with particular reference to onset after thymectomy. Medicine 1978;57:411–33. 3. Kondo K, Monden Y. Myasthenia gravis appearing after thymectomy for thymoma. Eur J Cardiothorac Surg 2005;28:22–5. 4. Tanimura S, Tomoyasu H, Banaba J, et al. Two cases of postthymectomy myasthenia gravis. Nippon Kyobu Geka Gakkai Zasshi 1992;40:1778–83. 5. Mineo T, Biancari F, D’Andrea V. Late onset of myasthenia gravis after total resection of thymoma: report of two cases. J Cardiovasc Surg 1996;37: 531–3. 6. Evoli A, Minisci C, Di Schino C, et al. Thymoma in patients with MG. Neurology 2002;59:1844–50. 7. Romi F, Skeie GO, Aarli JA, et al. Muscle autoantibodies in subgroups of myasthenia gravis patients. J Neurol 2000;247:369–75. 8. Pan CC, Chen PC, Wang LS, et al. Thymoma is associated with an increased risk of second malignancy. Cancer 2001;92:2406–11. 9. Vernino S, Lennon VA. Autoantibody profiles and neurological correlations of thymoma. Clin Cancer Res 2004;10:7270–5.
doi:10.1016/j.jocn.2008.09.019
Use of spontaneous ventilation to monitor the effects of posterior fossa surgery in the sitting position Mihir Prakash Pandia a,*, Parmod Kumar Bithal a, Manish Singh Sharma b, Hemant Bhagat a, Bidkar Prasanna a a b
Department of Neuroanaesthesiology, Neurosciences Centre, All India Institute of Medical Sciences, New Delhi 110 029, India Department of Neurosurgery, All India Institute of Medical Sciences, New Delhi, India
a r t i c l e
i n f o
Article history: Received 7 June 2008 Accepted 21 September 2008
Keywords: Spontaneous ventilation Posterior fossa Sitting position
a b s t r a c t We describe the successful excision, guided by spontaneous ventilation, of a cervico-medullary hemangioblastoma in a 22-year-old female in the sitting position. A balanced anesthesia technique comprising an oxygen, nitrous oxide, sevoflurane, fentanyl and vecuronium mixture was used. Apart from routine monitors, electroencephalographic spectral entropy monitoring was used to determine the depth of anesthesia and transesophageal echocardiography for detection of venous air embolism. The patient remained in spontaneous ventilation for 235 min during tumor excision. The intraoperative and postoperative course were uneventful. The patient recovered without any major neurological deficit. Ó 2008 Elsevier Ltd. All rights reserved.
* Corresponding author. Tel.: + 91 98 68398203; fax: 91 11 26588663. E-mail address: [email protected] (M.P. Pandia). .
Case Reports / Journal of Clinical Neuroscience 16 (2009) 968–969
969
1. Introduction
3. Discussion
Despite the concern of complications, posterior fossa neurosurgical procedures in the sitting position are still performed in several centers because of their distinct advantages. The use of spontaneous ventilation to monitor the integrity of vital brain stem structures has been described in various posterior fossa procedures.1,2 Here we describe the successful excision, guided by spontaneous ventilation, of a hemangioblastoma involving the brain stem with the patient in the sitting position.
The only strategy to deal with a hemangioblastoma is en bloc excision after circumferential dissection and devascularisation, as even an accidental entry into the tumor substance can cause torrential hemorrhage. The decision to use spontaneous ventilation was taken to avoid a high chance of injury to vital cardiorespiratory structures during surgery. In addition, any changes in the respiratory pattern during surgery would provide the surgeon with a warning signal of any potential damage of these structures. Evoked potentials are useful in monitoring the integrity of the brainstem, but they have their own limitations.2,3 Motor evoked potentials would not have been useful in this patient as the motor tracts were located ventral to the tumor. Brainstem auditory evoked potentials would also not have been useful, as the cochlear nuclei are present in the pontomedullary junction that was superior to the tumor. The incidence of false positives is very high during somatosensory evoked potential monitoring for brainstem tumors. This may prevent the progression of surgery and thereby interfere with the complete excision of the tumor.3 There is a theoretical possibility of an increased chance of air embolism during spontaneous ventilation in sitting neurosurgical patients. However, the available literature does not support this assertion.2,4,5 With the use of TEE, air embolism can be diagnosed at an early stage and appropriate corrective steps can be taken to prevent subsequent air entrainment. Sevoflurane seems to be the ideal volatile anesthetic agent because of its distinct physical properties. Rapid adjustment of inspired concentration of sevoflurane can be made by changing the dial setting of the vaporizer, thereby maintaining a stable depth of anesthesia. Monitoring EEG spectral entropy helps to maintain a satisfactory depth of anesthesia with a lower concentration of sevoflurane.6 The maintenance of an adequate depth of anesthesia was essential to avoiding coughing and patient movement. The use of a lower concentration of sevoflurane prevented the adverse effects of a deep plane of anesthesia, such as respiratory depression and hypercarbia. We believe that spontaneous breathing has a place in the monitoring of the structural and functional integrity of the brain stem, as it can greatly assist neurophysiological monitoring. With the use of better anesthetic and monitoring techniques, complications associated with spontaneous ventilation can be averted.
2. Case report A 22-year-old female, weighing 55 kg with a cervico-medullary hemangioblastoma was scheduled for midline suboccipital craniotomy and tumor excision. The tumor was 4.5 cm 3.5 cm 3.9 cm, and was centered in a subpial location around the obex, separated from the dorsal medulla by a cyst with a large blood vessel running over its dorsal surface (Fig. 1). The patient had no other systemic illness. She was premedicated with intramuscular glycopyrrolate (0.2 mg) an hour before surgery. Anesthesia was induced with fentanyl 150 lg and sodium thiopental 350 mg. Intravenous rocuronium (60 mg) was given to facilitate endotracheal intubation. Anesthesia was maintained with 66% nitrous oxide in oxygen, sevoflurane (inspired concentration between 1.5% and 2%), fentanyl and vecuronium. Apart from routine monitors, electroencephalographic (EEG) spectral entropy monitoring was used to determine the depth of anesthesia. Transesophageal echocardiography (TEE) was used for the detection of venous air embolism (VAE). The presence of a patent foramen ovale was ruled out by TEE. Intermittent positive pressure ventilation (IPPV) was maintained until the dura was opened. During removal of the bone flap, mannitol (1 g/kg) was infused. After the dura was opened and the tumor was exposed, muscle paralysis was reversed and the patient was allowed to breathe spontaneously. Neuromuscular monitoring at this point showed a train of four ratio of >0.9. An adequate depth of anaesthesia was ensured by keeping the state and response entropy level between 40 and 60. The partial pressure of arterial carbon dioxide (PaCO2) remained between 34 mmHg and 41 mmHg during spontaneous ventilation. The duration of spontaneous ventilation was 235 min. Cardiovascular and respiratory parameters remained stable during the intraoperative period. One episode of VAE detected by TEE was managed with temporary withdrawal of nitrous oxide and aspiration of air through the subclavian catheter. The patient’s intraoperative brain condition remained excellent. After the excision of the tumor, the patient was paralyzed and put on IPPV. The estimated blood loss during the procedure was 200 mL. The patient was electively ventilated overnight and extubated the next day without any major neurological deficit except for the loss of proprioception in both upper limbs from which she recovered completely after 6 weeks. A postoperative contrast enhanced CT scan confirmed total excision of tumor. doi:10.1016/j.jocn.2008.09.019
References 1. Millar RA. Neurosurgical anaesthesia in the sitting position. A report of experience with 110 patients using controlled or spontaneous ventilation. Br J Anaesth 1971;44:495–505. 2. Manninen PH. Spontaneous ventilation is a useful monitor of brain stem function during posterior fossa surgery. J Neurosurg Anesthesiol 1995;7:63–5. 3. Wiedemayer H, Sandalcioglu IE, Armbruster W, et al. False negative findings in intraoperative SEP neurosurgical cases and review of published monitoring: analysis of 658 consecutive reports. J Neurol Neurosurg Psychiatry 2004;75:280–6. 4. Tateishi H. Prospective study of air embolism. Br J Anaesth 1972;44:1306–10. 5. Hunter AR. Air embolism in the sitting position. Anaesthesia 1962;17:467–73. 6. Aimé I, Verroust N, Masson-Lefoll C, et al. Does monitoring bispectral index or spectral entropy reduce sevoflurane use? Anesth Analg 2006;103:1469–77.