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Anesthetic Management Of Thoraco-Omphalopagus Conjoint Twins Posted For Separation Surgery

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A conjoint twin is a rare congenital anomaly. Providing anesthesia for the separation surgery of conjoined twins presents unique challenges to the anesthesiologists. We report the anesthetic management for successful separation of thoraco-omphalopagus conjoint twins, along with challenges and limitations we faced in perioperative period. We highlight the importance of a multidisciplinary approach, proper preoperative planning, and perioperative vigilance regarding monitoring and complication.

Introduction

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The incidence of conjoint twins is rare, ranging from 1 in 50,000 to 200,000 live births with thoraco-omphalophagus being the most common. It is always challenging for anesthesiologist to provide anesthesia to conjoint twins whether for diagnostic studies or for separation surgery. We describe our experience concerning the successful anesthetic management of thoraco-omphalopagus conjoint twins posted for separation surgery.

Case report

A three month old thoracoomphalophagus conjoint twin was referred to our institute for separation. The twins were active and alert, and were joined ventrally from the manubrium sterni to umbilicus. They were labeled as baby 1 and 2, weighing 6.2 Kg collectively. During pre-anesthetic assessment both babies were properly evaluated for the presence of associated anomalies, extent of organ sharing and presence of cross circulation. Routine blood investigations, arterial blood gas, babygram, echocardiogram, abdomen ultrasonography and barium study of gastrointestinal tract were done. The presence of metabolic acidosis with pH 7.308 and 7.256 in baby 1 and baby 2 respectively was discussed with neonatologist, but the cause could not be ascertained. Contrast Computed tomography scan showed fused liver parenchyma and pericardium with no other evidence of organ sharing or cross circulation. The potential problems in perioperative period anticipated were difficulty in airway management (due to close proximity of the twins), dislodgment of endotracheal tube (ETT), accidental disconnection of monitoring lines, entanglement of intravenous (IV) line leading to cross-dosing of drugs, massive blood loss (with difficulty in estimation of blood loss from each individual twin), intraoperative hypothermia, metabolic and electrolyte imbalance and patient position before and after separation. These challenges were discussed within the department, with pediatrics surgeons, and neonatologist.

There were two separate anesthesia teams with two anesthesia workstations and duplication of all the anesthetic drugs and equipment. One day prior to the surgery, rehearsal of anesthesia plan was done. Proper identification of babies was assured by color coding. The first baby was labeled as green and the second one as red. Along with the babies, color coding was also applied on the working personnel, anesthesia workstations, monitoring lines, and infusion pumps with tubing. The drug doses were calculated by half the total drug dose for combined weight of the twins. Routine anesthetic and emergency drugs including noradrenaline, dopamine and dobutamine infusion were kept ready with calculated dose for emergency use. Even though both babies had same blood group, cross matching for compatibility was done, and blood and blood products were made available in OT.

In each baby of the twin, two IV lines including 24G cannula in hand and one peripherally inserted central catheter (PICC) in lower limb were secured. Central venous catheter couldn’t be inserted because of their complex head position. In the pre-warm operating room, standard monitoring was applied along with invasive blood pressure (IBP) and BIS monitoring. The presence of cross circulation was ruled out as there was no increase in heart rate of second baby with atropine premedication of first baby. We were unable to observe bispectral index (BIS) response of second baby on induction of first baby because of technical difficulty. Both babies were pre-oxygenated and premedicated with ketamine 0.5mg/kg and dexamethasone 0.1mg/kg. Sequential inhalational induction and intubation technique was used. The first baby was induced by Sevoflurane while succinyl choline was used as a muscle relaxation. Because of complex head position, it was an anticipated difficult airway management, so second baby was elevated over the first baby in order to facilitate intubation. The airway of first baby was secured with 3mm uncuffed endotracheal tube in third attempt and properly fixed in order to avoid tube displacement or unintentional extubation. After that the second baby was induced with Sevoflurane and intubated in similar way. The anesthesia was maintained with sevoflurane, fentanyl and atracurium as per the requirement.

Intraoperative monitoring included electrocardiogram, oxygen saturation, end tidal carbon dioxide (EtCO2), temperature, invasive blood pressure, hourly blood gas, electrolyte, blood sugar and urine output. Intravenous fluid D5% with 0.45% NS was used for maintenance, Isolyte P was used for third space losses. To prevent hypothermia all IV fluids were administered through hotline tubing, forced air warmer was applied, and OT temperature was maintained at a higher level.

Intraoperatively there was massive blood loss during separation of liver parenchyma and both the babies developed severe hypotension and drop of hemoglobin (Hemoglobin 4.2gm/dl, and 4.4gm/dl respectively). It was managed by bolus IV fluids, implementing massive blood transfusion protocol (also replacing plasma and platelets), and vasopressors. The estimation of blood loss from individual baby was very difficult. In the absence of CVP monitoring, the intravascular volume assessment was done according to the vital parameter, hourly ABG and urine output monitoring and blood loss was assessed by measuring surgical sponge and calculating drain output from surgical area although accurate assessment was not possible . Because of excessive IV fluids and massive blood transfusion, patients developed metabolic acidosis (pH 7.21 and 7.23), hyperkalemia (potassium 5.68 meql/dl and 5.8 meql/dl respectively) and hyperglycemia (glucose 320 mg/dl and 350 mg/dl respectively), which were successfully managed by inj calcium gluconate (4ml), insulin infusion and salbutamol nebulization. For persistent metabolic acidosis and refractory hypotension, inj. sodium bicarbonate was given. Inj. tranemexic acid was administered for massive blood loss. Surgery lasted nearly 8 hours and the total fluid administered in first baby was 600 ml including 170 ml blood products whereas the second baby received 1250ml IV fluid including 210ml blood products.

After successful separation of both babies, second baby was shifted to another OT table. As most of the liver tissue was retained in the second twin, in an attempt of skin closure, there was increased peak and plateau pressure along with bradycardia, hypoxia and increased EtCO2. So instead of primary skin closure of the defect, laparostomy was done in second baby. At the end of surgery both babies were on vasopressor support, and shifted to neonatal ICU for elective post operative ventilation and further management. Over the next 2 days they were weaned off from vasopressors and extubated on 2nd and 3rd day postoperatively. On fourth postoperative day, laparotomy closure in second baby was done. Both the babies were discharged healthy after a month.

Discussion

The separation of conjoint twins presents a unique challenge to anesthesiologists. The key factor in the success of the separation surgery lies in the multidisciplinary team approach with meticulous preoperative planning and interdisciplinary communication. One should go through the related literature, identify all the possible potential problems in perioperative period, discussed within the department, and formulate anesthesia plan. These challenges should also be discussed with pediatrics surgeons, and the neonatologist.

These surgeries require two separate dedicated anesthesia teams for each baby with unique OT preparations including two separate anesthesia workstations, along with duplication of all the anesthetic drugs and equipment. Proper rehearsal of anesthesia plan prior to surgery is necessary in order to avoid confusion and mismanagement on the day of surgery. Proper color coding should be applied not only on each individual twin but also on anesthesia workstations, monitoring lines, and infusion pumps with tubing for proper identification. There is high possibility of entanglement of IV line leading to cross-dosing of drugs, accidental disconnection of monitoring lines and dislodgement of ET tube leading to monitoring blackout and airway mishap. Meticulous attention to detail monitoring and vigilance are mandatory.

The survival after separation surgery depends on the extent and type of organ sharing, presence of cross circulation and any associated major cardiac anomalies. The proper and detailed preoperative assessment specially to evaluate the extent of organ sharing is the first and one of the most important steps. The presence of cross circulation in conjoint twin is a challenging concern as it can lead to altered and unpredicted drug responses in second twin varying from unplanned sedation to apnea. The presence of cross circulation can be confirmed by isotopes and contrast studies with technetium-99m Sulphur colloid, radiolabeled albumin or RBC, Tc-99m HIDA scintigraphy or by injecting indigo carmine in one twin and observe for its presence in the urine of other twin. The presence of cross circulation can also confirmed by observing heart rate response of second twin with atropine premedication of first twin and by observing BIS value of second twin on inducing first twin.

The main challenges include difficult airway, presence of cross circulation, massive blood loss (with difficulty in estimation of blood loss from each individual baby), intraoperative hypothermia, metabolic and electrolyte imbalance, prolonged surgery, and increased number of medical personnel involved. In thoracoomphalophagus conjoint twins, airway management can be difficult. In order to positioning the patient for intubation, the rotation of head alone may lead to distortion of the upper airway anatomy. This can be avoided by maintaining proper alignment of airway by elevating the second baby over the first baby. Although in literature nasal intubation has been mentioned but we used oral intubation with proper tightly fixing of ETT.

Regarding the fluid management, the maintenance fluid should be kept on higher side because of large insensible fluid loss from surgical area along with ongoing blood loss. Intraoperatively it usually becomes very difficult to estimate the individual blood loss due to shared operative field. IV fluid and blood should be guided by intravascular volume status reflected by CVP monitoring and serial hematocrit measurement. Along with invasive arterial and central venous monitoring, serial estimation of haematocrit, acid–base status and electrolytes are also needed. In our case, during separation of liver tissue there was massive blood loss, which was difficult to individualize in the absence of CVP monitoring. So intravascular volume was assessed by vitals, hourly ABGs and urine output. However in order to maintain MAP and hematocrit, large amount of IV fluid and blood product were transfused which resulted in electrolyte imbalance and possibly fluid overload. There is increased risk of intraoperative hypothermia in these surgeries and measure should be taken to prevent it by maintaining higher OT temperature, using warm IV fluid, hot water tubing, and forced air warmer. These patients may require post-operative ventilator support and intensive care unit care.

Conclusion

Proper preoperative planning, multidisciplinary communication, and perioperative vigilance regarding monitoring and complication are the key of success in separation surgery in conjoint twins. Our case highlights the responsibility of anesthesia team in anaesthetizing the two individual patients simultaneously, and management of anticipated complications like difficult airway management, massive blood loss, hypotension, acid base and electrolyte imbalance. These surgeries have major blood loss and intravascular volume shift, so we emphasize on proper evaluation of intravascular volume status and quantification of blood loss for better management. We felt that even with proper planning and rehearsal and taking care of anticipated problems, it is difficult to manage unanticipated problem due to complexity of anatomy and surgical field access and sharing of physiology.

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