A rare case of abdominal compartment syndrome following repair of large myelomeningocele.

Abdominal compartment syndrome is a rare entity that can be life-threatening if not diagnosed and correctly managed in time. We report a case of abdominal compartment syndrome following an apparently uneventful excision and repair of myelomeningocele (MMC). Though MMC is the most complex congenital spinal cord malformation compatible with life and early surgery is recommended to decrease the risk of meningitis and sepsis but generally surgery is safe without major perioperative turbulence. The majority of the skin defects following excision of MMC are repaired by primary skin closure, but large defects may require secondary closure by skin grafts or rotational flaps. We report a case of an infant with large MMC, who developed abdominal compartment syndrome following excision and repair of the swelling. Intraoperatively, it manifested as bradycardia, hypotension, and ventilatory difficulty which were managed successfully. Subsequently, in the postoperative period, the presence of tight abdomen and fall in urine output raised strong suspicion regarding development of abdominal compartment syndrome. Condition of infant improved following the release of flap sutures. A high index of suspicion along with early management is imperative for a successful outcome in such cases.

Introduction

Although the incidence of congenital spinal cord malformations is decreasing in developed world, it is not uncommon in developing world.[12] Myelomeningocele (MMC) is the most complex congenital spinal cord malformation compatible with life and presents as congenital swelling, containing spinal cord, cerebrospinal fluid, and meninges in the midline of the back. The associated Arnold-Chiari malformations (ACM) affecting the brainstem and cerebellum may or may not be symptomatic.[3] As infants with MMC are susceptible to the development of hydrocephalus, neurological damage, and meningitis, early surgery is recommended. Surgery is usually considered safe with minimal life-threatening perioperative complications. The majority of skin defects created by MMC excision are repaired by primary skin closure, but large defects require secondary closure by skin grafts or rotational flaps. We report a patient with large MMC, who developed catastrophic bradycardia, hypotension, and respiratory compromise due to abdominal compartment syndrome following an apparently uneventful excision and secondary repair of MMC.

Case Report

A 6-month-old, 5 kg, male patient presented with a history of swelling in dorsolumbar region (7 cm × 9 cm) since birth and progressive weakness of bilateral lower limbs. He was diagnosed to have of MMC with ACM for which ventriculoperitoneal shunting was done at postnatal age of 20 days. On examination, the infant was playful with a head circumference of 39 cm, and no movement in bilateral lower limbs. The child also had dorsal kyphoscoliosis. Laboratory investigations including hematology and biochemical parameters were within normal limits. Electrocardiogram and chest X-ray were unremarkable. Magnetic resonance imaging confirmed dorsolumbar spinal dysraphism, MMC, ACM (type II), and a ventriculoperitoneal shunt in situ [Figure 1].

Figure 1

Magnetic resonance image of the patient showing dorsolumbar spinal dysraphism, meningomyelocele, and Arnold-Chiari malformation (type II)

The infant was posted for excision and repair of dorsolumbar MMC under general anesthesia. Monitoring included 5 lead electrocardiography, noninvasive blood pressure, and pulse oximetry. Induction of anesthesia was achieved using increasing concentration of sevoflurane in oxygen with patient in supine position and the swelling placed in a donut. After securing an intravenous access fentanyl (2 mcg/kg) and rocuronium (1 mg/kg) were administered intravenously, and trachea was intubated with a 3.5 mm (internal diameter) microcuff endotracheal tube and bilaterally equal air entry were confirmed. Anesthesia was maintained with sevoflurane in O2:N2O (50:50) and intermittent boluses of rocuronium and fentanyl. Volume controlled mode (tidal volume – 40 ml and respiratory rate 22/min) was used. After induction invasive blood pressure, esophageal temperature and urinary output recording were also started. Thereafter, the child was placed in prone position. The incision of around 10 cm was made, and surgical repair included excision of the sac and dural repair. Postexcision, as the defect was large - a bilateral latissimus dorsi flap was used to achieve closure. During application of wound dressing, peak airway pressures increased up to 25 mm of Hg (from 12 to 13) associated with progressive bradycardia up to 65/min from 110/min, arterial hypotension 50/34 mmHg (from 74/38 mmHg), and desaturation up to 89% (from 99% to 100% on FiO2 0.5). There was no mechanical obstruction in breathing circuit or endotracheal tube. Chest auscultation revealed bilaterally equal but reduced air entry. The surgeon was immediately informed, and 100% oxygen was started. Intravenous atropine 0.2 mg and mephentermine 1.0 mg was administered, which temporary improved the hemodynamic status (BP 82/46 mmHg). The patient was turned supine and re-evaluated. Tracheal suction was done. Oxygen saturation came up to 93–94% (on FiO2 1.0) but peak airway pressures were still on the higher side (20–22 cm H2O). The total duration of surgery was 5 h, estimated blood loss 200 ml, total fluid intake was 400 ml, blood transfusion 170 ml, and urine output 20 ml. Neuromuscular blockade was not reversed, and he was shifted to neurosurgical Intensive Care Unit for further evaluation and management.

The child was nursed in lateral position and pressure control mode (inspiratory pressure of 18 cm H2O and respiratory rate of 26 breaths/min) was used for ventilation. The patient had poor lung compliance and soon there was fall in tidal volume delivered to patient and O2 saturation. The abdomen was tense so a nasogastric tube was placed, and 10 ml gastric contents were aspirated. It relieved the abdominal distension and slightly improved the respiratory compliance. Digital evacuation of impacted stools gave symptomatic benefit for another few hours. However, this was followed by bradycardia (57 bpm) along with fall in oxygen saturation to 80%. There was also associated drop in urine output. Tracheal tube was changed to rule out blockade along with necessary resuscitative measures for bradycardia and hypoxia were taken. Now, the flap was considered as prime culprit for decreased intra-abdominal volume, and the consequences. The lateral sutures of flap were removed which relieved abdominal distension and gradually patient's hemodynamic parameters and pulmonary compliance improved. The child was eventually extubated on the 2nd postoperative day and was fully intact neurologically. In following days, the defect was covered by skin graft and infant was discharged from the hospital on the 10th postoperative day.

Discussion

Rising airway pressures along with falling saturation in mechanically ventilated pediatric patients is not a rare finding and is largely attributed to positioning, ventilatory, and respiratory complications. Rare and uncommon complications may begin with such common symptoms and if missed can rapidly deteriorate to life-threatening situations. Tracheal tube/breathing circuits kinking or blockage, excessive pulmonary secretions, compression of the abdominal wall in prone position, and a lighter plane of anesthesia are usual culprits but were absent in this case. Initial findings such as high peak airway pressures, fall in saturation, and an episode of bradycardia and hypotension at the application of dressing were actually pointing toward a more serious pathology such as abdominal compartment syndrome. The presence of ACM II and kyphoscoliosis can also cause bradycardia and lung compliance-related complications, respectively. The episodes of intraoperative bradycardia were presumed to be a manifestation of ACM. However, subsequently in the postoperative period, the presence of tight abdomen and fall in urine output raised strong suspicion regarding the development of ACS.

Abdominal compartment syndrome is defined as sustained intra-abdominal pressure (IAP) >20 mmHg. Without appropriate management, this condition carries high morbidity and mortality. No standardized definition of ACS specifically for infants and children is available. ACS in children may occur at lower IAP cutoff values of 12 and 15 mmHg.[4] For an individual child, the actual IAP value may be less important than the impact of pressure on organ function. The risk factors for ACS include diminished abdominal wall compliance with primary facial or tight closure, major trauma/burns, prone positioning, elevation of head of bed >30°, high body mass index, increased intraluminal contents or abdominal contents, capillary leak/aggressive fluid resuscitation, systemic inflammatory response syndrome, and sepsis.[5] The incidence of ACS in these high-risk pediatric patients has been reported from 0.6% to 4% in various populations. Patients with trauma, ileus, necrotizing enterocolitis, abdominal wall defects, diaphragmatic hernia, and septic shock with massive fluid resuscitation are at higher risk.[67] To the best of our knowledge, there are no similar case reports of ACS following MMC repair. We believe that acute onset of ACS in this patient was secondary to decrease in intra-abdominal volume due to bilateral latissimus dorsi flap rotation. Other contributing factors could be slight perioperative fluid imbalance and diminished abdominal compliance due to prone positioning and kyphoscoliosis. Though the IAP was not measured, in this case, a tight abdomen, falling saturation, hypotension, decreased urine output and improvement in condition following flap release clearly pointed toward ACS. ACS has been reported after scoliosis correction surgery in a child in the prone position, and a similar mechanism of alteration in intra-abdominal volume relationship was defined as culprit.[8]

Sustained high IAP can have multisystem effects. It decreases perfusion to intra-abdominal organs, reduces renal blood flow and glomerular filtration rates. It increases systemic vascular resistance, pulmonary artery pressure, pulmonary artery wedge pressure, central venous pressure, and consequently fall in cardiac output. A diaphragmatic elevation increases intrathoracic pressure and decreases pulmonary compliance exerting a restrictive effect on lungs, and consequently increased airway pressures is common.[9]

Diagnosis is essentially clinical. A high index of suspicion is required for early recognition and timely intervention. Though direct measurement of IAP is the gold standard but intravesical pressure measurements are frequently used. The management includes a reduction in intraluminal content using gastric suctioning, rectal enemas, and gastroprokinetic and coloprokinetic agents; evacuation of any intra-abdominal space occupying lesions, optimal fluid resuscitation, and avoidance of fluid overload. In addition, abdominal wall compliance can be improved by adequate sedation and analgesia. If supportive measures fail then surgical measures such as open laparotomy are recommended. In our case, aspiration of gastric contents and digital evacuation of rectum did not help but flap release, restored the intra-abdominal volume, and improved the situation. This case report intends to raise concern about a rare, malignant but treatable complication following flap repair of large MMC in pediatric patients.

Conclusion

The secondary closure of large skin defects in pediatric patients should be meticulous. ACS may be life-threatening if not recognized and treated promptly. ACS should be considered in differential diagnosis in pediatric patients who develop poor lung compliance and hemodynamic instability following repair of large MMC defect. A high index of suspicion and focused assessment can help in the management of this potentially catastrophic complication.

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Conflicts of interest

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