Abstract
Objectives
No guidelines are available in France for peribulbar block for eye procedures. It is our hypothesis that continued use of acetyl salicylic acid for forestalling myocardial or cerebrovascular ischemic events does not increase the risk of hemorrhage, compared with discontinuation of its use in patients who undergo eye procedures under peribulbar block.
Methods
For this prospective control study we enrolled two groups of 500 patients scheduled for intra-ocular eye surgery requiring a peribulbar block. Patients treated with acetyl salicylic acid were included in group A (500 patients). Patients who had never been treated with acetyl salicylic acid constituted the control group (group B: 500 patients). Hemorrhages were graded as follows: 1 = spot ecchymosis; 2 = lid ecchymosis involving half of the lid surface area or less; 3 = lid ecchymosis all around the eye, without increase in intra-ocular pressure; 4 = retrobulbar hemorrhage with increased intraocular pressure.
Results
In group A, lid hemorrhages (grade 1) were observed in 30 patients (6.0%). No grade 2, 3 or 4 hemorrhages were encountered in this group. In group B, lid hemorrhage (grade 1) was observed in 20 patients (4.0%) and grade 2 in one patient (0.2 %), but no grade 3 or 4 hemorrhages were encountered. Statistical tests showed the absence of significance between both groups.
Conclusion
We conclude that between the groups with and without pre-operative acetyl salicylic acid the occurrence rate of lid hemorrhage was not significant in peribulbar block.
Keywords
aspirin; hemorrhage; nerve block: peribulbar; ophthalmologic surgical procedures;
1. Introduction
Patients scheduled for intra-ocular surgery are often elderly and may have concurrent diseases. A low dose of acetyl salicylic acid is used in France to prevent myocardial infarction and cerebrovascular ischemic events. Continuation or discontinuation of the use of acetyl salicylic acid in these patients is always a huge concern. Individuals with a history of cardiovascular events who stop taking low-dose aspirin are at increased risk of nonfatal myocardial infarction compared with those who continue treatment.1 Meta-analysis of randomized controlled trials has shown that low-dose aspirin is protective in most types of patient at increased risk of occlusive vascular events, including those who have had an acute myocardial infarction or ischemic stroke and those who have stable or unstable angina, peripheral artery disease, or atrial fibrillation.2
Phacoemulsification of the lens with topical anesthesia is recognized as safe3 in patients treated with acetyl salicylic acid. Guidelines for the observance of peribulbar block for ophthalmic procedures in patients who are under treatment with acetyl salicylic acid do not exist.
Our hypothesis is that the continuation of acetyl salicylic acid treatment in patients does not increase the risk of hemorrhage, compared with those who are not treated with acetyl salicylic acid, in eye procedures under peribulbar block. The continuation or discontinuation of acetyl salicylic acid before ophthalmic procedures under peribulbar block is hotly debated. Some teams replace acetyl salicylic acid with heparin or low-molecular-weight heparin, which differs in mechanism of action. This default choice is not suitable for an antiplatelet effect. Szalat et al stated that the possible use of low-molecular-weight heparin to replace aspirin should be further evaluated in a controlled clinical study.4 Therefore, we undertook a prospective case control study to ascertain the relationship between the continuation of acetyl salicylic acid and bleeding associated with a peribulbar block. The aim of the study was to assess the safety of the peribulbar block in patients treated with acetyl salicylic acid.
2. Methods
Approval of our hospital ethics committee was obtained for this prospective case control study. Patients who received elective ophthalmic surgery under peribulbar block from January 2006 to December 2009 were recruited. Patients were allocated to two groups on the basis of their antiplatelet therapy.
A total of 500 consecutive patients who continued to receive acetyl salicylic acid were allocated to group A with their written consent after verbal explanation of the risk of hemorrhage.
A total of 500 consecutive patients fulfilling the following criteria were allocated to group B, the control group, in which the participants never received acetyl salicylic acid. We checked that acetyl salicylic acid was not given at least 10 days before surgery. The same number of patients in group A (aspirin) and group B were chosen on the same day, with patients devoid of treatment with aspirin, randomly selected. The patients undergoing the same surgery in group A and group B were paired up. The surgery and anesthesia were performed by the same surgeon and the same anesthetist, respectively.
Patients treated with another anticoagulant drug such as warfarin or clopidogrel were excluded. Patients with pre-existing disorders, such as congenital coagulopathy, deficit in blood factors of coagulation, renal dysfunction, and unstable high blood pressure with treatment, were likewise excluded from both groups. Patients who had taken acetyl salicylic acid for a reason other than anti-aggregant therapy (chronic pain) and patients who had sometimes taken acetyl salicylic acid less than 10 days before surgery were excluded.
All patients received oral hydroxyzine (UCB Pharma SA) (0.5–1 mg/kg) or alprazolam (Pharmacia–Upjohn ) (0.01 mg/kg) 1 hour before surgery. A short-acting sedative drug (midazolam) 0.5 or 1 mg was intravenously administered 5 minutes before the peribulbar block to patients who seemed very anxious.
Two anesthesiologists were present in the operating room. The first anesthesiologist checked the anesthesia file and the second performed the peribulbar block. Both anesthesiologists were blinded to whether the patient was a user or nonuser of acetyl salicylic acid. The first anesthetist was in charge of data collection. The surgeon was blinded to the continuation of acetyl salicylic acid and assessed bleeding according to the defined protocol. Bleeding was assessed till the 24th hour after the peribulbar anesthesia. Hemorrhage was graded as follows: 1 = spot ecchymosis; 2 = lid ecchymosis involving half of the lid surface area or less; 3 = lid ecchymosis all around the eye with no increase in intra-ocular pressure and 4 = retrobulbar hemorrhage with increased intraocular pressure. We adopted the method of gradation of hemorrhage that Kallio et al had used for assessing their patients.
Peribulbar blocks were entrusted to three seasoned anesthesiologists familiar with Hamilton’s technique,5 as described in our previous studies.6, 7 The first percutaneous insertion of the needle (25 gage, 32 mm long) was parallel to the orbital floor at the lateral aspect of the inferior orbital rim (maximal depth 25 mm), and the second (maximal depth 25 mm) at level of supraorbital notch. The first injection was immediately stopped when the eye globe seemed tense. Once the eye globe became soft, the second injection was started until the sensation of the eye globe was tense. A Tono-Pen XL (Reichert Technologies, USA), which could offer intra-ocular pressure (IOP) reading that correlates closely with that by Goldmann Tonometry, is commonly used for checking suspected high IOP.
We used a mixed anesthetic solution comprising equal quantities of 2% lidocaine (20 mg/mL) and 0.5% bupivacaine (5 mg/mL). We never applied pressure by an ocular cuff after the peribulbar block. We never administered more than 10 mL of 2% lidocaine (200 mg) and 10 ml of 0.5% bupivacaine (50 mg).
A Fisher exact test was chosen to compare both groups.
3. Results
Both group A and group B comprised 500 patients. No patient was excluded from group A, because of interrupted acetyl salicylic acid treatment, nor was in group B because of having taken acetyl salicylic acid less than 10 days before surgery.
The volume of local anesthetic was 15 ± 5 mL in group A and 14 ± 6 mL in group B. No misacts were found among the three anesthesiologists. No patient expressed mild or severe cardiac or neurologic complication, nor was there any other side effect. The demographic and physical characteristics as well as ophthalmic procedures and hemorrhagic complication of both groups are shown in Table 1 and Table 2, respectively. Group A: lid hemorrhage (grade 1) was observed in 30 patients (6.0%). No grade 2, 3 or 4 hemorrhages were encountered. Group B: lid hemorrhage (grade 1) was observed in 20 patients (4.0%) and grade 2 in one patient. No grade 3 or 4 hemorrhagia was encountered. Statistical tests did not show significant differences between both groups.
Daily doses of acid acetyl salicylic acid were 75, 150 or 300 mg. Only patients chronically (more than 3 months) treated with acetyl salicylic acid were retained.
4. Discussion
Management of eye procedures under peribulbar block in patients who need treatment with acetyl salicylic acid is not standardized in ophthalmology. Each center has its own protocol. Dick et al8 reported in a multicentric retrospective study (172,880 surgeries in 1995) that 63% of surgeons advised their patients to continue acetyl salicylic acid treatment. They concluded that antiplatelet therapy could influence the anesthetic technique and the surgical approach. Carter et al9 noticed that in patients taking acetyl salicylic acid (62 patients, 82 eyes) 8.5% of them experienced subconjunctival hemorrhage. No patients developed lid ecchymosis or retrobulbar hemorrhage. In 482 patients taking acetyl salicylic acid, Kallio et al10 observed that only 3.7% of them developed hemorrhage and concluded that the continuation of acetyl salicylic acid would not predispose patients to hemorrhage when a retrobulbar/peribulbar block was undertaken. A retrospective survey carried out by Ong-Tone et al, in Canada showed that 25.6% surgeons routinely stopped acetyl salicylic acid prior to cataract surgery. The majority of surgeons who discontinued this therapy usually did so about 3–7 days before surgery. Topical anesthesia and clear corneal incision were preferred in cataract surgery by most surgeons.11 In a non-randomized case series, Kobayashi concluded that patients taking warfarin, acetyl salicylic acid, or both, up to the time of phacoemulsification had a significantly higher incidence of subconjunctival hemorrhage than those who discontinued the therapy before surgery.12 The great majority of these studies were retrospectively done or few patients were reported. We were not of the same opinion with those on the pessimistic side in the literature. Thus we ventured to clarify this dilemma. Does, the materiality of peribulbar block in patients treated with acetyl salicylic acid, really increase the risk of hemorrhage? To solve the predicament, we chose to carry out a prospective case control, monocentric study with a control group.
The overall incidence of hemorrhage in our study was 6% (30/500) in group A and 4.2% (21/500) in group B. The incidence rate of hemorrhage in our study (6%) was higher than that of Kallio et al (3.7%), but lower than that of Carter et al (8.5%). Our incidence rate is within the range reported in the literature. The variation is probably because of the different, nonstandard methods used to assess the hemorrhage. The size of patient sample and the absence of statistical significance between both groups seem convincing to conclude that the continuation of acetyl salicylic acid, in patients scheduled for eye procedures under peribulbar block, does not predispose patients to hemorrhage. Furthermore thromboembolic complications in elderly patients can be forestalled by the continuation of acetyl salicylic acid treatment. We were aware that a control group of patients who had discontinued acetyl salicylic acid would increase the power of the study. Our study of 500 patients treated with acetyl salicylic acid did not show difference from the control group. These results are reassuring and support the clinical practice.
Peribulbar block can be safely performed in patients treated with acetyl salicylic acid scheduled for eye procedures and does not predispose them to hemorrhage.