Difficult intubation in a case of ankylosing spondylitis: a case report.US Kamarkar, LS Chaudhari, H Hosalkar, M Budhi, D Venkataraghavan
Department of Anaesthesia and Orthopaedics, Seth G.S. Medical College, Mumbai.
A case of severe ankylosing spondylitis involving the entire spine was to be operated for lumbar osteotomy. She had fixed rigidity of the cervical spine with minimal rotational movement, inability to lie down supine and severe restrictive lung disease with hypoxemia (pO2 = 65 mmHg). An awake intubation was performed and the patient was operated under general anaesthesia in the prone position. Intraoperative "wake-up" test was performed to judge whether extent of straightening was excessive. Postoperatively, she was electively ventilated and extubated uneventfully after 24 hours.
Keywords: Adult, Anesthesia, General, methods,Case Report, Female, Human, Intubation, Intratracheal, methods,Osteotomy, Spondylitis, Ankylosing, surgery,
Ankylosing spondylitis involving the cervical spine can result in decreasing mobility and in severe cases, total fixity. The cricoarytenoid joints and temporomandibular joints may also be involved resulting in a difficult airway, which may not be evident on conventional airway scoring systems. Ankylosis involving the thoracic cage may result in rigidity of the costovertebral and costochondral joints. Restrictive lung disease with irreversible changes set in after a period of time. This report describes a case of ankylosing spondylitis with fixed rigidity of the cervical spine and exaggerated thoracic kyphosis resulting in severe restrictive lung disease, who was operated for lumbar osteotomy in prone position.
A 24 year old, 61 kg female patient who was diagnosed to have ankylosing spondylitis was referred to the Neuro-spine surgical unit. She had been having gradual onset of deformity which was painless since 4 years and progressive, with involvement of all the facet joints of spine resulting in thoraco-lumbar kyphosis so that she was unable to look up and unable to straighten herself while walking. Her gaze was thus fixed on the ground while walking and she could compensate the neck and back rigidity by flexing her knees and marginally looking up.
She could not squat or sit cross-legged thus imposing restrictions in her lifestyle. Due to the exaggerated curvature of the spine and fixed rigidity of the neck, the patient could not lie down supine, but needed two thick pillows, beneath her head to support it. Her sleep at night had to be in the lateral position.
There was no family history, and she had no other concurrent medical problems, besides being minimally obese.
She was married and had history of one pregnancy, which had progressed full-term, culminating in a Caesarean Section done under General anaesthesia 4 years ago. It was a still birth. Details of the surgery and anaesthesia were unavailable. Since the last 4 years, she had progressive worsening of her condition with decreasing mobility of the joints, onset of dyspnoea and increasing dependence on others for simple daily activities.
She was scheduled for surgery of a corrective osteotomy in prone position at the lumbar level, which would consequently bring her thoracic and cervical spine in line with the lumbar spine. Excessive correction could compress the cord and therefore, an intraoperative “wake-up” test was required to ascertain that straightening was not resulting in a neurological deficit.
On clinical examination, patient was found to have normal parameters, as far as her pulse and blood pressure were concerned. Her respiratory system was clear and heart sounds were normal. There were no signs of right ventricular failure. Neck movements were restricted in anteroposterior as well as lateral position, with no extension and minimal flexion possible. Mouth opening was normal. An indirect laryngoscope revealed marginal vision of the epiglottis and the cords. Laboratory studies including Haemoglobin, liver function tests and renal chemistry, Serum electrolyte profiles were normal.
The Arterial blood gases showed mild hypoxemia (pH 7.41, pO2 65 mm Hg, pCO2 39.5 mm Hg, HCO3 25.8 and SaO2 92.6%).
The Pulmonary function tests showed FEV1 1.36 L (45%), FVC 1.40L (39%), FV1/FVC 92%, FEF25-75 2.4L% (54%), i.e. severe restrictive disease.
A lumbar osteotomy was planned. The plan of anaesthetic management was to perform an awake intubation. Accordingly, to ascertain the degree of difficulty, the patient was brought to the recovery room one day prior to the surgery. In supine position 2 pillows were placed under the head. The procedure of awake intubation and the need to do a direct laryngoscopy was explained to the patient. The patient breathed through an oxygen mask with 4% lignocaine spray added to the nebuliser. Repeated gargles of 4% viscous lignocaine were done and after lightly depressing the tongue the area around the epiglottis was sprayed with 4% lignocaine. When the patient confirmed numbness in the oral cavity, the larygoscope was gently inserted inside and then slowly advanced inside. The vocal cords were clearly visualised.
On the day of surgery, the patient was pre-medicated with Atropine 0.6 mg. intramuscularly. Monitoring include a five lead ECG, pulse oximetry ETCO2.
The procedure of the previous day was repeated and with the patient reclining in supine position, an awake intubation was performed uneventfully with 32 No. armoured tube. Induction was done with intravenous Thiopentone sodium (275 mg) and Suxamethonium Chloride (100 mg) along with Buprenophine 120?g.
Atracurium 25 mg was given with 5 mg supplemental doses to maintain relaxation along with Nitrous oxide, oxygen mixture of 60%:40% ratio. Myovin ointment applied to the forehead was sufficient to maintain an intraoperative Blood pressure between 90 and 100 mm systolic. Patient required careful handling and extra care as the ankylosis made her rigid, so that prior to positioning, the curvature of the operating table and the bolsters had to confirm to the spine curvature of the patient. Moreover, the ankylosis of the spine increased the chances of accidental fracture, especially of the rigid cervical spine, should there be any error in the position.
A C-shaped head ring under the head prevented kinking of the ET tube which remained central as the patient’s head could not be turned. Adequate care of the eyes, nose and pressure points was taken. Intraoperatively, after lumbar osteotomy was performed, a “wake-up test” was done. After an elapse of 20 minutes since last dose of Atracurium, the patient was given intravenous Neostigmine (1.0mg) slowly. Satisfactory movement of the lower limbs was noted as per the verbal command and the patient was given relaxant again.
The surgery lasted 7 hours and the intraoperative blood loss was 550 cc, which was replaced with one unit of fresh blood. Intraoperative ETCO2 was maintained between 20-35 mm Hg and central venous pressure between 12-15 cm H2O keeping in mind the patients tendency to pulmonary hypertension. Her postoperative blood gas showed pH 7.45, PCO2 21.6 mmHg, PO2 147 mmHg, HCO3 15.3, and SaO2 99.4%. The patient was electively ventilated for 24 hours, following which she was weaned off & extubated uneventfully. Post extubation, her blood gas on FIO2 30% showed pH 7.45, PCO2 35.5 mmHg, PO2 108 mmHg, HCO3 25.5, and SaO2 98.5%.
Ankylosing spondylitis affects 0.40% men and 0.05% women, with a maximum incidence between 25-40 years of age. A strong genetic influence exists and is evident by the HLA B-272 factor, which is positive in 96% of cases. The clinical spectrum of the disease is wide. The skeletal system is extensively affected. Involvement of the costochondral and costocervial joints results in limited chest expansion and impaired movement of the ribs. The temporomandibular, cricoarytenoid and sacroiliac joints are also involved. The cervical spine may be significantly involved with varing degrees from mild limitation to total ankylosis. This is of great concern to the anaesthetist. The degree of difficulty of intubation may not be evident on a Mallampatti score.
Besides, all involved joints are brittle and are predisposed to easy fractures. These problems can be further compounded by cardio-pulmonary and hepato-renal dysfunctions that are seen in some cases of Ankylosing spondylitis.
This patient was scheduled for a lumbar osteotomy for correction of deformity. The operative mortality for this surgery is 10% due to spinal cord injury or cerebral anoxia. A detailed preoperative examination was performed with a request for indirect laryngoscopy and cardiovascular, pulmonary and hematological abnormalities looked for. The airway was also assessed. Although literature on this subject suggests that due to the high risk involved, cases of lumbar osteotomy have been performed under local anaesthesia with minimal sedation and brief periods of intravenous anaesthesia for some phase of surgery. We opted for general anaesthesia in this case, for the patient’s comfort.
This patient had to be managed from the point of view of her severe ankylosing spondylitis [Figure - 1] which prevented her from lying supine and also restricted her neck movements in all directions thus making her intubation difficult. Furthermore, her restrictive lung disease with mild hypoxemia left her with very little reserve to withstand any degree of hypoxia in the event of any failure to intubate her after administering relaxant. Our decision to perform an awake intubation was influenced by the above; as we felt that it was hazardous to the patient and is well tolerated if intubation fails.
The prolonged nature of surgery and prone position required meant that the patient would require good relaxation, adequate analgesia and also sufficient oxygenation to tide her over the preoperative phase.
The need for “wake-up” test and the general condition of the patient made us opt for atracurium as relaxant and Buprenorphine in a dose of 2 mg/kg was decided as most beneficial.
Fluid calculations and management of blood pressure were very important in a patient with severe lung disease. Prone position had to be given carefully, bolsters confirming to the contours of the patient to avoid fractures.
Post-operatively, the decision to electively ventilate the patient was taken mainly for two reasons. We felt that in the immediate post-operative period, this patient who had withstood the stress of a prolonged surgery and anaesthesia and was still under the influence of narcotic, could have further deterioration of hypoxemia with complication of CO2 retention due to her restrictive lung disease. Moreover, the surgical correction had involved correction of the lumbar level only and the thoracic and cervical spine pathology which was a major influence on our anaesthetic plan remained unchanged. Had we extubated her, the chances of reintubation in the immediate postoperative period were high and would have been stormy as the reintubation in awake state would be difficult.
After a period of elective ventilation, the patient was extubated uneventfully.
We thank the Department of Orthopaedics and the Department of Chest Medicine extending their co-operation in the management of this patient.
[Figure - 1]