Anaesthetic management of a parturient with spondylothoracic dysostosis

Abstract

Spondylothoracic dysostosis is a rare congenital disorder characterised by multiple vertebral malformations, shortening of the spine and fusion of the ribs at the costovertebral junction. These abnormalities create anaesthetic challenges due to difficult airway, severe restrictive lung disease and spine deformity necessitating a multidisciplinary approach and careful perioperative planning. We present the perianaesthetic management of a parturient with spondylothoracic dysostosis who successfully underwent preterm caesarean delivery under general anaesthesia with awake videolaryngoscopy-assisted tracheal intubation.

Background

First described by Lavy in 1966 and then by Moseley in 1969, spondylothoracic dysostosis (STD) is a rare autosomal-recessive disorder characterised by multiple malformations of the vertebrae, severe shortening of the spine and complete bilateral fusion of the ribs at the costovertebral junction.^{1 2} The condition is associated with a mutation in the MESP2 gene, a Notch pathway gene.² STD affects about 1 in 200 000 people worldwide. However, it is much more common in people of Puerto Rican ancestry, affecting approximately 1 in 12 000 people.³

There has been confusion in the naming and distinction between STD and Jarcho-Levin syndrome, which is known as spondylocostal dysostosis (SCD).^{4 5} STD is a separate clinical entity with distinct molecular aetiology, natural history, prognosis and mode of inheritance from SCD. STD involves spine and costal fusion with greater thoracic insufficiency, higher mortality rate and higher rate of neural tube defects than SCD.⁵

STD patients have a small physical stature, short and rigid neck due to occiput and first cervical vertebra fusion, increased anteroposterior (AP) thoracic diameter, kyphoscoliosis, high arched palate, protruding abdomen with inguinal/umbilical hernias and normal-length extremities.⁶ Spine defects include sickle‐shape vertebrae, block and wedge vertebrae, unsegmented bars, hemivertebrae and spina bifida.⁶ Chest roentgenogram of STD patients shows fusion of the ribs at the costovertebral junction leading to a ‘fan-like’ or a ‘crab-like’ thorax. The malformations can lead to respiratory insufficiency, recurrent lung infections and a high rate of early childhood mortality (44%).^{1 6}

STD creates anaesthetic challenges due to a difficult airway, restrictive lung disease and vertebral anatomy. The literature is scarce regarding the anaesthetic care of pregnant patients with STD.

We discuss the perianaesthetic management of a parturient with STD who successfully underwent the caesarean delivery under general anaesthesia (GA) of a preterm fetus. Written informed consent was obtained from the patient.

Case presentation

A 30-year-old Puerto Rican woman G2P1 at 34 weeks of gestation with STD and fetal cardiac malformations was referred to our tertiary care centre for obstetric management. During the pregnancy, the patient did not tolerate lying supine because of dyspnoea and increased pressure in her chest. She slept leaning forward over a five-pillow tower and intermittently used home oxygen therapy (2 L/minn) while walking and sleeping. Her medical history consisted of asthma, recurrent pneumonia and a caesarean delivery under GA that required awake fiberoptic intubation (FOI) and postoperative mechanical ventilation.

Physical examination revealed a short neck with limited extension and a Mallampati class 4 airway. Her thorax was protruding with a wide AP diameter. Her spine was short with kyphoscoliosis (figures 1 and 2). She had a body mass index of 31.5 kg/m² with a height of 126 cm and a weight of 50 kg.

Figure 1.

Postoperative photograph of the patient with spondylothoracic dysostosis. Note the short neck, and the protruding thorax and abdomen.

Figure 2.

Photograph of the back of the patient with spondylothoracic dysostosis.

Investigations

The preoperative workup included echocardiography, pulmonary function tests (PFTs) and arterial blood gas analysis (ABG). Echocardiography was normal with a mildly increased right ventricle systolic pressure and no pulmonary hypertension. PFTs performed at 36 weeks of gestation showed severe restrictive lung disease with forced vital capacity (FVC) 27%, forced expiratory volume in 1 s (FEV₁) 25%, FEV₁/FVC 90%, Total lung Volume (TLV) 29%, vital capacity (VC) 28% and diffusing lung capacity for carbon monoxide (DLCO)74% of the predicted values. ABG analysis on room air showed a pH 7.43, partial pressure of carbon dioxide 39 mm Hg, partial pressure of oxygen 90 mm Hg, HCO₃ 25 meq/L, BE 1, arterial oxygen saturation 97% and haematocrit of 33 g/dL. Pulmonology consultation recommended the use of bronchodilators prior to surgery, the application of lung protective strategies during the mechanical ventilation and the likely need of postoperative ventilatory support.

Treatment

A multidisciplinary meeting was organised with a maternal–fetal specialist, obstetric anaesthesiologist, neonatologist and paediatric cardiologist. The anaesthetic plan concentrated on the patient’s challenging airway, severe restrictive lung disease and difficulty of using neuraxial techniques. Surgical concerns centred on inability to retract the abdomen for proper visualisation of the suprapubic area due to restrictive lung disease. Fetal care focused on the availability of a paediatric cardiologist and neonatologist on the day of surgery.

Due to maternal medical condition, a caesarean section was scheduled at 37 weeks of gestation under GA. We decided to perform awake videolaryngoscopy-assisted tracheal intubation because of patient’s previous upsetting experience with awake FOI. After preoperative administration of albuterol, nebulised 3 mL lidocaine 4%, intravenous glycopyrrolate 0.2 mg and 30 mL oral sodium citrate/citric acid were given. Topical anaesthesia of the the vocal cords was achieved with lidocaine 2% and the patient was positioned in a semireclining, ramped supine position. A remifentanil infusion was started at 0.2 μg/kg/min and oxygen at 2 L/min was established via a nasal cannula along with CO₂ monitoring. Using a C-MAC (Karl Storz, Tuttlingen, Germany) videolaryngoscope D blade, a grade 1 laryngoscopic view was obtained, and a size 6 endotracheal tube was placed on the first attempt. Afterwards, anaesthesia was induced with intravenous propofol (60 mg) and rocuronium (20 mg). Propofol and remifentanil infusions were used for maintenance of anaesthesia.

Mechanical ventilation was initiated with pressure control ventilation-volume guaranteed mode using a tidal volume of 280 mL, respiratory rate of 22/min, PEEP of 5 cmH2O, peak airway pressure of 30 cmH₂O and fractional inspired oxygen of 60%. Due to difficulty retracting the abdomen, a supraumbilical midline vertical skin incision was performed versus the Pfannenstiel incision that the patient previously had. Using a classical uterine incision, a baby girl was delivered with Apgar scores of 8 and 9 at one and 5 min, respectively. The baby was admitted to the neonatal ICU and underwent surgical repair of tetralogy of Fallot at 2 months of age. The total operative duration was 56 min with an estimated blood loss of 1 L. One unit of blood and 2 L of crystalloid (Isolyte B. Braun Medical) were given. Postoperative haemoglobin level was 110 g/L.

For postoperative pain control, 0.6 mg of hydromorphone and 1 g of acetaminophen were given intravenously. Due to inadequate respiratory effort, the patient was kept intubated and transferred to the intensive care unit (ICU). She was extubated 24 hours later and given, as necessary, oral oxycodone/acetaminophen (5/325 mg), ibuprofen (800 mg) and intravenous morphine (0.5 mg) for pain.

Outcome and follow-up

Similar to her preoperative status, she required supplemental oxygen postoperatively. She was discharged home 7 days after surgery on home oxygen therapy (2 L/min).

Genetic analysis of the newborn was highly emphasised due to autosomal recessive inheritance and a founder effect leading to the relatively high prevalence of this disorder in Puerto Rico.⁶

Discussion

Practitioners taking care of patients with STD perioperatively need to address difficulties posed by vertebral anatomy, airway and severe restrictive lung disease. In the context of pregnancy, these challenges are amplified secondary to perinatal physiological effects.⁷

Neuraxial anaesthesia in patients with vertebral abnormalities like STD can be challenging and require multiple considerations.^8–10 In a series of patients with severe restrictive lung disease and spinal column deformity, neuraxial techniques failed or were not possible in one-half of the patients.⁸ Our patient’s vertebral malformations, kyphoscoliosis and inability to lie flat due to respiratory insufficiency precluded the use of neuraxial anaesthesia.

Patients with STD have a difficult airway since fusion of the cervical vertebrae and occiput prevents extension of the atlanto-occipital/atlantoaxial joints and flexion of the lower cervical spine (sniffing position).^{10 11} In the context of pregnancy and STD, an awake intubation by an experienced practitioner is recommended due to difficult airway and high risk of aspiration. The awake C-MAC intubation was shown to be of comparable efficacy to awake FOI and proved to be a successful approach in our STD patient.¹²

Restrictive lung disease in STD patients increases risk of hypoxic and hypercapnic respiratory failure during the pregnancy. Preoperatively, echocardiography to exclude pulmonary hypertension, PFTs and ABG analysis are needed. Intermittent monitoring of oxygen saturation is necessary and supplemental oxygen therapy may be required as oxygen demands increase after the first trimester.¹³ Mild-moderate relative hypercapnia results from limited ability of parturient to increase minute ventilation, as seen in our patient.^{7 8}

Mechanical ventilation in STD patients with severe restrictive lung disease requires lung protective strategies with a tidal volume of 6–8 mL/kg of ideal body weight, moderate PEEP and plateau pressure of less than 30 cm of water.¹⁴ In that regards, pressure-controlled ventilation is superior to volume-controlled ventilation in providing adequate oxygenation and ventilation at lower inspiratory pressures.¹⁵ Patients may need ventilatory support due to respiratory insufficiency postoperatively.⁸ Given that our patient had a prolonged postoperative intubation previously, a difficult airway anatomy and an extensive vertical abdominal incision we chose to keep her intubated. Extubation in STD patients requires planning with the presence of personnel trained in advanced airway management, the availability of the necessary equipment and appropriate postextubation monitoring.^{9 16} Risk of postoperative respiratory depression could be reduced by decreasing opioid administration and using multimodal pain control approaches (acetaminophen, non-steroidal anti-inflammatory drugs, transverse abdominis plane block, local anaesthetic infiltration).¹⁷

Surgically, caesarean delivery is preferred since patients with STD may not tolerate the increased work and oxygen consumption during labour and delivery. In a series of patients with restrictive lung disease, 9 out of 10 pregnant women with chest wall or neuromuscular disease had to undergo preterm caesarean delivery.⁸ Difficult access to the uterus and need for a modified surgical approach using a vertical supraumbilical incision may lead to excess blood loss. Early intervention for blood loss is necessary since patients with STD have a small body habitus with a low ideal body weight, plasma volume and medication requirements.¹⁸ Attention to amount of fluids administered is essential to avoid fluid overload and pulmonary oedema.

Learning points.

• Patients with spondylothoracic dysostosis presenting for surgery require a multidisciplinary approach for safe perioperative management.

• General and neuraxial anaesthesia are challenging in such patients due to difficult airway, respiratory compromise and vertebral anomalies.

• Surgery may be complicated by difficult uterine exposure.

• The low body weight and circulating blood volume of these patients require early intervention for blood loss and judicious fluid administration.

• Adequate respiratory care and pain management are crucial for quick recovery.