Although several cases of Horner's syndrome have been reported following epidural analgesia, there has not been a case reported following low-dose epidural infusion. This case is reported in order to highlight the potential dangers of a low-dose regime which in spite of the relative lack of early warning signs may be associated with a high block.
A 31-year-old, healthy primigravida (ASA Grade 1) was scheduled for induction of labour and requested an epidural for pain relief. She was of slim build weighing 75 kg and 175 cm in height. After hydration with 1000 mL of Hartmann's solution the epidural catheter was placed with ease via a 16-gauge Tuohy needle through the L3/4 interspace. The catheter was advanced 4 cm in the epidural space with the needle pointing cephalad. Following a negative aspiration test, a test dose of 3 mL bupivacaine 0.25% ruled out a subarachnoid block. Five minutes later 8 mL of bupivacaine 0.25% was given, with the patient in the left lateral position for a period of 5 min. The patient was then sat up at an angle of 45°. Thirty minutes later the upper sensory level to cold was T8 on the left and T9 on the right. The patient remained in the semi-sitting position and a continuous infusion regime with bupivacaine 0.08% plus fentanyl 2.5 μg mL−1 was started at a rate of 10 mL h−1. The patient's blood pressure remained stable with a systolic above 110 mmHg. One and a half hours later, the patient complained of a strange feeling in her left eye'as if it was closing'. She had no other symptoms (no paraesthesia, muscle weakness, light-headedness or dyspnoea). On examination she appeared well in herself despite a drop in the blood pressure to 88/55 and an obvious left-sided Horner's syndrome. The facial skin was dry and flushed, the conjunctiva was red, and miosis with ptosis of the eyelid were present. Her upper sensory level to pinprick was T2 on the left and T3 on the right. She was able to give a good cough and move all her limbs with no evidence of any motor weakness. A total of ephedrine 20 mg was needed to restore the systolic blood pressure above 100 mmHg.
Horner's syndrome resolved 90 min after the cessation of the epidural infusion. By this time the upper sensory level to cold had fallen to T12 and analgesia was inadequate. After a bolus of 5 mL bupivacaine 0.25%, the infusion was restarted at 7 mL h−1. This resulted in an upper limit of skin analgesia to T8 with no recurrence of Horner's syndrome. The decision was made to deliver by Caesarean section, because of foetal distress, 4 h after epidural was established. In view of the unpredictable nature of the epidural block, it was decided to perform the Caesarean section under general anaesthesia. A healthy baby was delivered.
Horner's syndrome is a rare complication of lumbar epidural block , and was first reported by Kepes et al. in 1972 . Horner's syndrome is characterized by miosis, ptosis, enopthalmus, conjunctival congestion as well as vasodilatation and anhidrosis on the ipsilateral side of the face. It occurs when the sympathetic nerve supply to the pupil, levator palpebrae, conjunctiva and face is interrupted. This supply arises from the anterior horn cells of C8 and T1. The sympathetic fibres are of smaller diameter than sensory or motor fibres and are blocked at lower concentrations. This accounts for the number of cases of Horner's syndrome in whom the upper limit of skin analgesia is at the level of T7 or lower[3,4].
The incidence of Horner's syndrome after lumbar epidural block, performed for labour, is reported to be 1.33% . Almost all reported cases of Horner's syndrome after lumbar epidural block have been described in pregnant women during provision of analgesia for labour pain or for Caesarean section . This may be explained by anatomical changes resulting from the unique physiology of pregnancy and labour, which will favour cranial spread of local anaesthetics . The volume of the epidural space in pregnant women is decreased due to partial occlusion of the inferior vena cava that diverts blood through the epidural venous plexus. This space is further reduced during Valsalva manoeuvres, as can occur during the second stage of labour when the patient 'bears down' . This compresses the epidural space, and may induce extensive cephalad spread of the local anaesthetic. This did not happen in this case as the patient was still in the first stage of labour.
The occurrence of Horner's syndrome in the absence of motor blockade may be explained by the higher sensitivity of the sympathetic and sensory nerve fibres to local anaesthetics. The author believes that this is the first reported case of Horner's syndrome involving bupivacaine infusion 0.08%.
The resulting transient hypotension although asymptomatic could have been detrimental to the foetus. In this case, the hypotension associated with the Horner's syndrome did not result in foetal distress. The eventual foetal distress, 4 h after establishing the epidural block, was not associated with maternal hypotension and the Horner's syndrome had already resolved.
Low-dose epidural infusion of bupivacaine has generally been regarded as a safer alternative than bolus injection in labour. It is also the case that close supervision is not deemed necessary in some centres where the mother is receiving such an epidural infusion. The purpose of this case report is to highlight the potential dangers that could arise from a low-dose regime due to the lack of early warning signs associated with a high block. With the introduction of ropivacaine, similar problems may arise. Ropivacaine shows preferential blockade of sympathetic and sensory nerve fibres, with relative sparing of the motor nerve fibres .
It is recommended that regular testing of the sensory level, even with a low-dose regime is advisable.
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