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Department of Anesthesia and Surgical Intensive Care, Singapore General Hospital
Address correspondence and reprint requests to Ted Wong, MD, FRCPC, Department of Anesthesia and Surgical Intensive Care, Singapore General Hospital, Outram Rd., Singapore 169608. Address e-mail to wong_ted{at}hotmail.com
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Abstract |
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IMPLICATIONS: The following case report documents the anesthetic planning and management leading to and including a 5-day separation of twins joined at the head. This case report also details the difficulties encountered during the unique combination of a rarely performed procedure and a long operating time.
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Introduction |
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Case Report |
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After extensive evaluation, the only abnormality found was that Twin B had a cleft lip and palate, which contributed to her subnormal nutritional status. The girls were attached at the skull vertex and faced 180 degrees away from each other, classifying them as total vertical craniopagus.
General anesthetics were required for computed tomography (CT) scans, specialized magnetic resonance imaging (MRI) scans, and angiography. The girls were 5-mo-old with a combined weight of 9.3 kg when they were first anesthetized. After appropriate monitors were placed on both twins (electrocardiogram [ECG], pulse oximetry, and noninvasive blood pressure), Twin A was anesthetized first by mask induction with sevoflurane and 50% nitrous oxide. IV access was established and the airway secured by means of a size 1 laryngeal mask airway (Laryngeal Mask Company, Henley-on-Thames, United Kingdom). After Twin A was stabilized and no adverse effects seen in Twin B, Twin B was anesthetized in the same manner. Both airway and IV access were established with relative ease, and spontaneous respiration was maintained throughout transfers and investigations.
Anesthesia was maintained with propofol infusions of 36 µg · kg-1 · min-1 with intermittent boluses to each twin and 40% oxygen, delivered via modified T-piece, and wall source oxygen to each twin. For subsequent anesthetics in the MRI suite, anesthesia was maintained with sevoflurane and nitrous oxide delivered via a single MRI compatible anesthetic machine with a y-connector split to two modified T-pieces (Figure 1).
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On the day of the separation, the twins were 11-mo-old and weighed 13.5 kg. They were once again individually induced with sevoflurane and nitrous oxide and nasally intubated with size 4-mm endotracheal tubes. The lines included two peripheral IV catheters, a 22-g radial arterial catheter, and a 4.5F triple lumen internal jugular central catheter into each twin. The invasive monitoring lines were inserted the day before the separation under general anesthesia.
Monitors included ECG, pulse oximetry, capnography, end-tidal (ET) drug monitoring, neuromuscular blockade monitoring, esophageal and rectal temperature, somatosensory evoke potentials, and urinary catheters.
Maintenance anesthesia consisted of isoflurane (ET, 0.6%–0.75%) in an air/oxygen mixture (fraction of inspired oxygen, 40%) and intermittent individually dosed boluses of fentanyl and morphine. Muscle relaxation was provided by atracurium infusion (5 µg · kg-1 · min-1). Body temperature was maintained with the use of blankets, heated air mattresses, and adjustment of ambient temperature. Phenobarbital was provided for seizure prophylaxis, and antibiotics (vancomycin and ceftazidime) were administered at appropriate intervals. Fluid, electrolyte, and blood replacement were guided by central venous pressure (CVP), urine output, and point-of-care determinations of arterial blood gases, electrolytes, and hematocrit. A panel of laboratory studies including complete blood count, electrolytes, and prothrombin time/partial thromboplastin time was sent to the lab each day. A summary of the 5-day operation is presented in Table 1.
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Final separation occurred on the morning of Day 5. This was particularly hazardous, again requiring multiple personnel to support the twins while they were transferred to separate tables in the prone position with their brains being fully exposed. Twin A’s operation finished approximately 8 h before Twin B’s, and she required extensive chest physiotherapy and cardiorespiratory support because of copious secretions and fluid overloaded lungs as a result of the shunting during the previous days. She was transferred immediately to the intensive care unit (ICU) in stable condition but initially requiring 80% fraction of inspired oxygen and pressure support of 28/6 cm H2O.
After surgical separation, Twin B was turned supine for her surgical closure. After closure, a lumbar drain was inserted, and just before transfer, she developed hypertension and bradycardia suggestive of increased intracranial pressure. This was treated with a bolus of thiopental (3 mg/kg) and atropine (10 µg/kg) with no further complications. She was transferred from the operating room to radiology for a CT scan before transfer to the ICU. She remained in stable condition throughout. In the end, the total operating time for Twin A was 94 h, whereas for Twin B, it was 102 h (Table 2).
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On discharge at the age of 18 mo, Twin A had adequate head control, could weight bear with support, and reach for and grab objects. She had a mild residual hemiparesis but was alert and socially responsive. Her social and communicative skills were assessed as being at the developmental age of 12 mo.
Twin B
The postoperative course for Twin B was more complicated because of the more extensive neurological injury during surgery. The main problems the first few days were related to increased intracranial pressure and seizure activity. Twin B recovered well enough to be tracheally extubated on the 17th postoperative day. As with her sister, Twin B developed numerous bacterial and fungal infections and also had persistent hydrocephalus, which also required a lumbar peritoneal shunt. She would undergo a further 14 general anesthetics for various procedures after separation.
At 18 mo, Twin B had poor head control because of the weight of her head, but she could sit with support. She had increased tone in all four limbs but retained good strength. She had a significant visual defect but was able to respond to voices and noises. Her social and communicative skills were assessed at a developmental age of 6 mo.
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Discussion |
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A major concern was the unknown quantity of vascular shunting between the twins’ cerebral circulations. We noted that while the first twin was being induced, the second twin would inconsistently stop crying or become quieter. This was borne out by the preoperative cranial Doppler that showed bidirectional flow through the connected superior sagittal sinuses. During the various anesthetics before the final separation, we alternated the sequence of which twin would be anesthetized first. No clinical difference or evidence of consistent major cross transfer was seen. However, during the five-day course of surgery, the intracranial shunt flow was being altered by the progressive vascular disconnection and redistribution of the cerebral blood flow (both arterial and venous).
We theorized that after the disconnection of the superior sagittal sinus, redistributed cerebral venous blood was slowly shunting from Twin B to Twin A. Initially, this was partially compensated by a feeding cerebral artery flowing from Twin A to Twin B. Once this feeding artery was disconnected, there was relatively unopposed shunting of venous blood from Twin B to Twin A. This produced dangerous levels of hypervolemia in Twin A and hypovolemia in Twin B, requiring the use of vasoactive infusions, withdrawal of blood from Twin A, transfusion of Twin B, and tilting the bed in favor of venous drainage into Twin B. These were temporizing measures, at best, while the definitive management of surgical separation of the cerebral blood vessels took place.
The neuroradiological investigations determined the following: (a) the left cerebral hemispheres of each twin herniated into the cranial cavity of the other twin compressing the respective posterior fossa, (b) the line of separation between the two brains was at a steep diagonal to the midline, i.e., a ying-yang configuration with further axial rotation, (c) the twins shared the superior sagittal sinus, although individual deep venous drainage pathways seemed to be intact, (d) Twin A had hydrocephalus, and (e) it was estimated that 200 sq cm of exposed brain would need to be covered after the separation. The anesthetic implications of these findings included a very long operation, massive blood loss, significant fluid and electrolyte shifts, and multiple position changes with the twins at various stages of separation.
We estimated, after some practice runs, that the operation would take a total of 80 hours. We decided early that all the anesthetic care would be by a team of four anesthesiologists. We planned that all four anesthesiologists would be in attendance during the initial phases of the operation, during all position changes, and the final separation. During the rest of the time, between two and four anesthesiologists were in attendance with at least two resting before any anticipated major position change or intraoperative event.
The selected anesthetic was intended to maximize cerebral protection and minimize toxicity and potential delay in postoperative neurological assessment. Isoflurane was chosen because of the potential adverse effects of prolonged propofol infusion on the pediatric liver over the course of five days. Atracurium infusions were selected because of its spontaneous mode of metabolism and the goal of minimizing possible prolonged paralysis. We felt that laudanosine accumulation and seizure activity was not a significant risk (5,6), and we attribute the postoperative seizure activity to residual ischemic and infarcted brain tissue and meningitis. Nitrous oxide was omitted because of its potentiation of venous air embolism and its adverse affects on intracranial pressure. Mild hypothermia was maintained by use of (Bair huggers®, Eden Prairie, MN) and manipulating the ambient temperature. In the operating room, blood gas and electrolyte analysis allowed for rapid determination and replacement therapy. Flow charts were made to keep a running tabulation of fluids and timing of various drugs to be given.
The position changes were particularly hazardous because of the numerous lines and tubings in situ, compounded by the need to coordinate the turning of the two partially disconnected infants. After each repositioning, every opportunity was made to re-secure lines and tubes and provide tracheobronchial suctioning and chest physiotherapy because of accumulated secretions. Pressure points were padded and rechecked after each turn. Additional attention was given to the eyes because of the inability to perform tarsorrhaphy of Twin B’s eyes because of the extra tension on her eyebrows from her deformed skull.
This case emphasizes the importance of teamwork and communication, not only between the various departments, but also within the anesthetic team. The team was chosen based on subspecialties (pediatrics, cardiac, intensive care, and neuroanesthesia), workable numbers, and most importantly, compatibility and ability to function as a team. Expertise in cardiopulmonary bypass and circulatory arrest was required in the event of its use because the technique has been used in previous separations (7), and the extent of the connection between the twins had not been evaluated before their arrival to our center. The teamwork was critical when trying to anticipate the unique challenges mentioned and especially when we experienced the shunt problem on Day 4.
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Acknowledgments |
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Footnotes |
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References |
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This article has been cited by other articles:
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  J. L. Stone and J. T. Goodrich The craniopagus malformation: classification and implications for surgical separation Brain, May 1, 2006; 129(5): 1084 - 1095. [Abstract] [Full Text] [PDF]
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