Anesthetic concerns of achondroplastic patients with hip movement restriction scheduled for retrograde intrarenal surgery

A case report

Abstract

Achondroplasia is an autosomal dominant inherited disorder that results in premature ossification of the epiphyseal growth plates and restriction of proximal long bone movement. Herein, we report the anesthetic management of such a patient undergoing stone retrieval in the lithotomy position. He had a restricted ability to flex and abduct the hip joint and lumbar hyperlordosis. These were anticipated to be a concern for the lithotomy position and prone to positional injuries. Hence, the decision was made to position the patient before induction of anesthesia in the presence of surgeons to ensure the optimal exposure needed for the procedure while avoiding any hyperflexion or abduction of the hip and knee joints. The position tolerated by the patient when awake and unsedated should be followed intraoperatively. Achondroplasia is also associated with difficult airway features, obesity, sleep apnea, and multisystem involvement. Careful preoperative evaluation and intraoperative vigilance are needed to manage these patients undergoing surgery.

Introduction

Achondroplasia is an inherited form of skeletal dysplasia resulting in short-limbed dwarfism.[¹] There is premature ossification in epiphyseal growth plates with restriction of growth in the hip, shoulder, and proximal long bones. Achondroplasia poses unique anesthetic challenges like a difficult airway, multisystem involvement, obesity, and vertebral and joint anomalies.[¹] Herein, we report the successful anesthetic management of such a patient undergoing retrograde endoscopic stone retrieval in the lithotomy position.

Case History

A 33-year-old male achondroplastic patient with a body mass index (BMI) of 36.6, diagnosed with right renal and lower ureteric calculus was posted for retrograde intrarenal surgery. He had a history of snoring with a STOP-BANG score of 4/8 and difficulty in climbing stairs due to restricted hip flexion. Airway assessment revealed a large head, short neck with a circumference of 42.3 cm, limited neck extension, and Mallampatti grade 3. The spine examination revealed lumbar hyperlordosis. He had restricted hip joint flexion and abduction. These restrictions would pose difficulty for the lithotomy position, which required hip flexion at 80–100 degrees, abduction of the hip at 30–45 degrees from the midline, and loss of lumbar lordosis. The concerns, in this case, were a difficult airway, obesity, possible atlantoaxial instability with neck extension, difficulty in positioning, and possible positional injuries. On the day of surgery, a difficult airway cart and equipment needed for positioning were kept ready. The patient was transferred to the operating room, standard monitors were attached, and a 20G intravenous line was secured using ultrasound as there was difficulty locating the vein. The cricothyroid membrane was marked using ultrasonography. The lithotomy position was given in the presence of members of the surgery and anesthesia team to assess the optimal position needed for surgery and to prevent any injury due to hyperflexion or abduction of hip joints under anesthesia. The position was restricted in terms of abduction and flexion at the hip joint but was agreed upon by all team members [Figure 1], and general anesthesia was induced in the same position. The patient's head was positioned such that the tragus and sternal notch were at the same level. After preoxygenation, IV fentanyl and propofol were administered. A two-person mask ventilation technique was used without adjuncts while avoiding hyperextension of the neck. After adequate relaxation with IV atracurium, a size 4 i-gel supraglottic device was successfully placed. Anesthesia was maintained with isoflurane in air and oxygen (50:50), and atracurium boluses. Pressure-controlled ventilation was used targeting a tidal volume of 6–8 ml/kg IBW, and the respiratory rate was adjusted to maintain eucapnia. IV paracetamol, ketorolac, and fentanyl boluses were used for intraoperative analgesia. The patient remained hemodynamically stable intraoperatively. After surgery, the patient was made supine carefully and extubated after reversal of muscle relaxation once he was awake and responsive to commands.

Figure 1: Position of patient with restricted hip abduction before induction of anaesthesia

Postoperatively he was shifted to the post-anesthesia care unit for monitoring and a detailed examination excluded any positioning-related injuries.

Discussion

Achondroplastic patients need careful preoperative evaluation and intraoperative management for a successful postoperative outcome.[²]

These patients have difficult airway features like a premature fusion of the skull base, depressed nasal bridge, maxillary hypoplasia, macroglossia, large mandible, abnormal tooth implantation, tracheal narrowing, short neck with fat deposition, cervical osteophytes, atlantoaxial instability, and limited neck extension.[²] Neck extension during direct laryngoscopy bears the risk of cervico-medullary compression due to narrow foramen magnum causing quadriparesis or sudden death.[²] Limited neck extension poses difficulties in visualizing the larynx during direct laryngoscopy.[³] Rib hypoplasia, flattened ribcage, pectus excavatum, and obesity cause restrictive lung disease, resulting in decreased functional residual capacity, increased closing volume, atelectasis, reduced apnea time, sleep apnea, pulmonary hypertension, cor pulmonale, and increased risk of postoperative pulmonary complications.[²] Pressure-controlled ventilation with lower tidal volumes and a high respiratory rate has been advocated for ventilation in these patients.[¹] No modes of ventilation were found to be superior to the others.

In our patient, because a difficult airway was anticipated along with decreased FRC, a difficult airway cart was kept ready. Our primary plan was to place an i-gel after successful bag and mask ventilation and if it failed, the next plan was to intubate with a video-laryngoscope with stabilization of the cervical spine. The cricothyroid membrane was marked before induction of anesthesia in case a cannot intubate cannot ventilate situation arises. Although our patient did not show symptoms or signs of pulmonary hypertension which may rarely occur in achondroplasia, we still avoided using nitrous oxide, and active measures were taken to avoid hypoxia, hypotension, and hypercapnia.

Patient positioning in the operating room is a combined responsibility of surgeons and anaesthesiologists, who should cooperate and decide the optimal position while being vigilant about position-related injuries like peripheral nerve injuries, under anesthesia, and muscle relaxation. Injuries occur due to stretching, ischemia, or compression of peripheral nerves, but the precise mechanism cannot be determined in many cases. Common peroneal, sciatic, lateral femoral cutaneous, obturator, and lumbosacral nerve root injuries have been reported in the lithotomy position. Sciatic nerves can be stretched by hyperflexion of the hip or extension of the knee beyond the comfortable range. The obturator nerve can be injured by hyperflexion of the thigh to the groin.[⁴]

Vertebral, hip, and knee joint abnormalities and contractures in achondroplasia can complicate intraoperative positioning, making patients prone to nerve injuries. Spinal anomalies include kyphoscoliosis, lumbar hyperlordosis, narrow vertebral canal, spinal cord stenosis, ischemia, nerve root compression, and osteophyte formation with degenerative changes.[²] In our patient, lumbar hyperlordosis with spinal fusion, restricted hip, and knee flexion, and abduction prompted us to position the patient before anesthesia induction in the presence of surgeons to ensure optimal exposure for surgery while avoiding any positioning-related trauma.

Individual practices differ because clear information on the causes and prevention of peripheral injuries is lacking. The American Society of Anesthesiologists has published a practice advisory for the prevention of perioperative peripheral neuropathies which states appropriate judgment is required to ascertain that patients can tolerate the anticipated operative position. Documentation of the actions taken during positioning may help focus attention on important aspects and improve patient care.[⁴]

Positions that would not be tolerated by the patient when awake and unsedated increase the associated risks. Hence, the intraoperative position should be within the natural range of motion for the duration of surgery.[⁴]

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient has given his consent for his images and other clinical information to be reported in the journal. The patient understands that his name and initials will not be published and due efforts will be made to conceal identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.