Department of Anaesthesia, Helsinki University Central Hospital, Helsinki University Eye Hospital, PO Box 220, FIN-00029 Helsinki, Finland
Accepted for publication: 29 June, 2000
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Abstract |
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Br J Anaesth 2000; 85: 70811
Keywords: surgery, ophthalmological; complications, haemorrhage; anaesthesia, local; non-steroidal anti-inflammatory drugs
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Introduction |
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Patients and methods |
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The appearance and size of the haemorrhages were assessed on a four-grade scale: 1=spot ecchymosis; 2=lid ecchymosis involving half the lid surface area or less; 3=lid ecchymosis all round the eye, no increase in intraocular pressure; 4=retrobulbar haemorrhage with increased intraocular pressure. Nine doctors performed the blocks; three were experienced anaesthetists and six were doctors in training (four anaesthetists and two ophthalmologists).
Transconjunctival retrobulbar/peribulbar block was performed as described previously.6 First, a medial peribulbar puncture was made with a sharp, disposable, 12-mm, 30-gauge needle (Microlance®; Becton Dickinson, Drogheda, Ireland) in the near perpendicular direction of the frontal plane, followed by inferolateral retrobulbar insertion of a sharp, disposable, 31-mm, 27-gauge needle (PrecisionGlide®; Becton Dickinson, Franklin Lakes, NJ, USA). The local anaesthetic used was a 1:1 mixture of 0.75% bupivacaine and 2% lidocaine with hyaluronidase 07.5 IU ml1. The maximum total volume of local anaesthetic was adjusted according to the lean body weight of the patient: 6 ml for patients under 70 kg body weight, 7 ml for patients between 70 and 80 kg, and 8 ml for those over 80 kg. As the local anaesthetic was injected, the anaesthetist palpated the lid with his finger, and if increased pressure was sensed the injection was stopped. Orbital compression of 25 mm Hg for 10 min was accomplished with an autopressor (Autopressor®; Storz, Heidelberg, Germany), except in patients who had had an operation on the same eye during the last 6 months. All patients were monitored using finger-pulse oximetry, continuous end-expiratory carbon dioxide using tubing in the nostril, electrocardiography, and non-invasive automatic blood pressure every 10 min. An intravenous cannula was inserted for the administration of sedatives or fentanyl as required. A stream of oxygen-enriched air (oxygen 2 litre min1 + air 8 litre min1) was directed at the patients face under the surgical drape.
The hypothesis was that use of anticoagulants and the preoperative discontinuation time do not affect the occurrence of haemorrhages (grades 14). Statistical analysis was undertaken with the MannWhitney rank sum, 2 and Fishers exact tests, using SigmaStat for Windows, version 2.0 (Jandel Corporation). Values are expressed as mean (SD, range). A P value <0.05 was considered statistically significant.
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Results |
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Use of more than one drug that may affect coagulation was characteristic of this patient population (Table 2). Also, the drug-free preoperative period varied considerably. The drug category, the time of discontinuing drug therapy and the use of various combinations of drugs did not affect significantly the occurrence of haemorrhage. Warfarin was used by 5.5% of the patients and its use did not predispose to haemorrhage (Table 2). The mean thromboplastin time value in patients who had haemorrhage (35% (19, 2056)) did not differ significantly from that of patients who had no haemorrhage: (39% (16, 1481)). The prevalence of diabetes mellitus was 22% in patients receiving warfarin, and cortisone was used continuously by 3.9% of diabetics receiving warfarin. Among the latter subgroup (three patients), none developed any detectable haemorrhage from the block. Table 2 shows the frequencies of concomitant use of warfarin with acetylsalicylic acid, NSAIDs or paracetamol.
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Discussion |
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It can be assumed that visible haemorrhages do not always appear within 10 min (duration of autopressor compression) after injecting the block and a few cases may have remained undetected, especially those presenting as minor spot-like haemorrhages. The physician performing the retrobulbar/peribulbar block graded the occurrence and size of the haemorrhage. We are aware that a non-blinded assessment could have been biased and, to some extent, led to underestimation of iatrogenic complications. But the observed frequency of haemorrhages, as evaluated 10 min after the injection, is probably accurate. It is also possible that patients who had taken acetylsalicylic acid and/or NSAIDs 12 weeks before surgery were registered as non-users. Elderly patients may not remember occasional use of these drugs. Such assumed inaccuracy of the data may make the results somewhat less powerful. Haemorrhages were as frequent in patients taking warfarin as in those who were not. More than 500 patients receiving warfarin should have been included in this study in order to make any conclusion about the necessity of stopping warfarin preoperatively. Furthermore, if more patients had been included it may have been possible to detect any interaction of warfarin and platelet aggregation inhibitors in provoking haemorrhage.
A large retrobulbar haemorrhage may delay a planned eye operation,2 and may cause compression of the circulation7 or optic atrophy8 leading to permanent blindness. The prevalence of retrobulbar haemorrhage after retrobulbar injection has been reported to vary from 0.44 to 1.7%.24 In a retrospective study 60 retrobulbar haemorrhages were induced by a retrobulbar block (1.7% of all retrobulbar blocks). Warfarin, acetylsalicylic acid and NSAIDs were stopped 14 days before surgery. The study included a control group of 60 patients. Thirty per cent of patients with haemorrhage received at least one of these drugs, whereas these drugs were taken by only 20% of the patients in the control group.4
Platelet cyclo-oxygenase is acetylated irreversibly by acetylsalicylic acid. Cyclo-oxygenase inhibition by NSAIDs leads to reversible disturbance of platelet aggregation.9 A healthy individual produces platelets at the rate of about 70x109 litre1 per day and a concentration of normal functioning platelets of 3050x109 litre1 is adequate for normal clotting.10 Forty-eight hours should, therefore, be sufficient for the recovery of clinically adequate thrombocyte function after the last mini-dose of acetylsalicylic acid.10 There have been no large-scale studies of the influence of the duration of discontinuation of acetylsalicylic acid, other NSAIDs and warfarin on haemorrhage during retrobulbar/peribulbar blocks. But there are some similarities between retrobulbar/peribulbar and epidural blocks. Whereas the use of warfarin at therapeutic doses contraindicates epidural block, the use of acetylsalicylic acid and other NSAIDs up to the day of the block may be considered safe in patients undergoing epidural block.11 12 Acetylsalicylic acid 60 mg day1 is not associated with a significant increase in bleeding during epidural anaesthesia.11 The use of antiplatelet therapy in patients undergoing spinal or epidural anaesthesia has not been found to be associated with an increased incidence of spinal haematoma.12 However, acetylsalicylic acid medication has been reported to increase bleeding at the operation site.1315 In contrast, there is some disagreement about the role of other NSAIDs in surgical bleeding, but on the whole it does not increase it.1619 The exception is a report of 41 hysterectomy patients who received indomethacin preoperatively for postoperative analgesia.20
As a result of complications associated with retrobulbar block, several alternative techniques have been developed, such as the use of a curved needle. This was associated with a very low frequency of haemorrhages (lid ecchymosis 2%).21 Topical anaesthesia is also free from anaesthesia-related haemorrhage. However, the sub-Tenon method of regional ophthalmic anaesthesia may not be an option for reducing the risk of haemorrhage when compared with retrobulbar/peribulbar anaesthesia.22
In our practice there seems to be no reason to limit the use of acetylsalicylic acid or other NSAIDs before retrobulbar/peribulbar block. On the other hand, our study supports the assumption that preoperative discontinuation of warfarin for 2 days preoperatively might be sufficient to maintain haemostasis to prevent bleeding during retrobulbar/peribulbar block.
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References |
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