Anaesthetic Management of an Achondroplastic Dwarf

ANAESTHETIC MANAGEMENT OFAN ACHONDROPLASTIC DWARF

CHANDRAKANT P GOSAVI*, LS CHAUDHARI**,RASHMI PODDAR***
*Registrar, KB Bhabha Hospital, Kurla 400 070. **Professor in Anaesthesia, KEM Hospital, Parel 400 012. ***Anaesthetist, Lotus Eye Hospital, VN Desai Hospital, Mumbai.

This report describes successful management of an 11-year-old achondroplastic dwarf who was operated for bilateral Illizarove ring fixation for limb lengthening under general anaesthesia. Endotracheal intubation was not difficult. The reaction of the patient to drugs such as thiopentone and vecuronium was normal. His perioperative and postoperative courses were uneventful. The existing literature on the anaesthetic management of achondroplastic dwarf is reviewed and considerations are presented concerning general and regional anaesthesia.

INTRODUCTION

The anaesthetic management of achondroplastic dwarf offers a considerable challenge to anaesthesiologists. Achondroplasia, which is the commonest form of short-limbed dwarfism (1:10000 live births) resulting from a failure of endochondral bone formation. The basic abnormality is a disturbance of cartilage formation, mainly at epiphysical growth plates and at the base of skull. Orthopaedic sequelae, such as kyphoscoliosis and genu varum are common. Mental and sexual functions are normal. Muscular development is normal. Prematurity is frequent, but those surviving first year of life generally have a normal life expectancy.

CASE REPORT

An 11-year-old boy presented with short-limbed dwarfism to orthopaedic department, where he was diagnosed as achondroplastic dwarf.

On examination his height was 125 cm (4’2") and wt 30 kg. Examination of his chest revealed pectus excarinatum, a type of a deformity with bilaterally reduced expansion but otherwise normal breath sounds. He had short limbs, short cranium and a depressed bridge of the nose. Trunk was normal. His heart rate was 84 per minute and regular. Arterial pressure was 110/70 mm of Hg. Heart sounds were found to be normal on auscultation. The trachea was centrally placed Chest movements were symmetrical.

Preoperative investigations were normal with haemoglobin of 10 gm%.

An 18 gauge intravenous cannula was inserted. Premedication consisted of atropine 0.3 mg intravenously. Following pre-oxygenation for 5 minutes, anaesthesia was induced with 150 mg thiopentone. Suxamethonium 60 mg was used to facilitate the insertion of 7.5 mm portex cuffed endotracheal tube. Intubation was not difficult. Anaesthesia was maintained with nitrous oxide 4 litres: oxygen 3 litres in a semi-opened circuit. Vecuronium was used to provide adequate muscle relaxation and intermittent positive pressure ventilation was established. Arterial pressure remained around 90-110 mm of Hg throughout the surgery. The entire operation lasted for 6 hrs 30 minutes. The total vecuronium administered was 12 mg. Reversal of residual neuromuscular blockade was achieved satisfactorily with neostigmine 1.5 mg and atropine 0.6 mg. Spontaneous ventilation was quickly established. After extubation of the trachea the patient was given oxygen by face mask for 10 minutes in the operation theatre. Patient was monitored with cardioscope and pulse oximeter. He remained clinically well and his oxygen saturation was satisfactory throughout the procedure.

Postoperatively analgesia was provided by injection diclofenac 50 mg intramuscularly thrice a day. Patient was given chest physiotherapy to avoid postoperative respiratory complications.

DISCUSSION

Achondroplasia is the most common form of dwarfism with an incidence of 1 in 10000 live births. Transmission is by autosomal dominant gene. Approximately 80% of cases represent spontaneous mutation, 20% are familial. Females are affected more frequently than males. Achondroplastic dwarfs have low fertility rates. [3] The basic defect is caused by poor development and premature ossification of bones that form from cartilage coupled with normal periosteal bone formation. This leads to the characteristic craniofacial and spinal abnormalities. [3]

Anaesthesia both regional and general poses problems for achondroplastic dwarf. The trachea may be difficult to intubate due to craniofacial deformity and a small tracheal tube may be required. [3,4] Review of the data for patients with achondroplasia by Mayhew et al suggest that age based formula for selecting endotracheal tube size for children i.e. {tube size (mm ID) = [age (yr) + 16]/4} usually predicts the correct endotracheal tube size. [1 ,6] These patients may have narrow nasal passages and pharyngeal hypoplasia as a result of dysplasia and angulation of cranial base and hypoplasia of maxilla; airway can readily be managed with face mask. [1] The sternal prominence associated with pectus carinatum can interfere with the midline positioning of the laryngoscope. So use of laryngoscope with sturdy handle is indicated. Hyperextension of the neck should be avoided during tracheal intubation to prevent cervical cord compression because foramen magnum stenosis is common. [1,3] The requirement for thiopentone for the induction of anaesthesia, as judged on body weight basis, was normal. Similarly, the requirement of vecuronium on a body weight basis was normal in this patient. This suggests that drugs should be administered on a precised body weight basis in achondroplastic patients. The patient may suffer from mild restrictive lung disease from rib hypoplasia, thoracic lordosis and Cor pulmonale from restrictive lung disease. Also central and obstructive sleep apnoea is common. It is suggested that pre oxygenation before anaesthesia and the administration of oxygen by face mask for some time after endotracheal extubation may be beneficial. Because of the diminished respiratory function postoperative management should include adequate physiotherapy to avoid any possible postoperative respiratory complications. [7]

Regional anaesthesia may be technically difficult because of poor landmarks, but many achondroplastic dwarfs have normal spine. A relatively narrow spinal canal may result in cord compression, prolapsed discs and deformed vertebral bodies. [3 ,7] In elderly achondroplastics the possibility of disc herniation with resultant paraplegia may warn against the use of subarachnoid blockade. [8] A narrow epidural space may make catheter insertion difficult and a subarachnoid tap more likely. Recognition of subarachnoid tap may be difficult because free flow of CSF may be difficult to obtain. [3] Attempting an epidural puncture above the lordotic space. Epidural anaesthesia is preferable to spinal anaesthesia because it helps in titration of the dose of local anaesthetic according to the height of block; prevents marked hypotension and its associated complications.

The anaesthetic management of the achondroplastic dwarf is a challenge. All patients must be assessed preoperatively to identify potential hazards. The risks incurred with epidural anaesthesia and the possibility of general anaesthesia must be discussed. Finally adequate time must be made available for the insertion of the epidural catheter and establishment of adequate block.

The anxiety shown by these patients is much greater than that observed in normal adults. A good rapport between anaesthetists and patients may prove useful in elective cases. [7]

REFERENCES

1.Brimacombe JR, Caunt JA. Anaesthesia in a gravid achondroplastic dwarf. Anaesthesia 1990; 45 : 132-34.

2.Jan Carstoniu, Irvan Yee, Stephen Halpern. Epidural anaesthesia for caesarean section in an achondroplastic Dwarf. Canadian Journal of Anaesthesia 1992; 39 : 708-11.

3.Ivar D, Berkowitz, Srinivasa N Raja, Karen S Bender, Steven E Koptis. Dwarfs : pathophysiology and anaesthetic implications. Anaesthesiology 1990; 73 : 739-59.

4.Mayhew JF, Katz J, Miner M, Leiman BC, Hall ID. Anaesthesia for the achondroplastic dwarf. Canadian Anaesthetist’s Society Journal 1986; 33 : 216-21.

5.Cohen SE. Anaesthisa for cesarean section in achondroplastic dwarfs. Anaesthesiology 1980; 52 : 264-66.

6.Wardall GJ, Frame WT. Extradural anaesthesia for caesarean section in achondroplasia. British Journal of Anaesthesia 1990; 64 : 367-70.

7.Kalla GN, Fening E, Obiaya MO. Anaesthetic management of achondroplasia. British Journal of Anaesthesia 1986; 58 : 117-19.

8.Fairbank TJ. The heriditory chondrodysplasias. In : Sir Ronald Bodely Scot, Ed. Price’s Textbook of the Practice of Medicine. 12th Edn. London : Oxford University Press. 1978; 981.

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