Studies on regional and topical ophthalmic anaesthesia. Applications related to the development of modern ophthalmology

Abstract

Retrobulbar/peribulbar block haspreviously predominated local ophthalmic anaesthesia. It is associated with certain serious, albeit infrequent complications. In order to diminish the risk of block-induced haemorrhage patients are advised to stop taking acetylsalicylic acid, nonsteroidal anti-inflammatory drugs and anticoagulants before surgery. In laser therapy of diabetic retinopathy and cyclophotocoagulation for glaucoma complete sensory block is desired, but eye mobility does not inhibit treatment and in some cases mobility is desirable. Hyaluronidase has been added to the local anaesthetic to enhance the spreading of the retrobulbarly and peribulbarly injected local anaesthetic solutions and thereby improves the block. There are also contradictory results suggesting that there is no need for hyaluronidase in local anaesthetic blocks, especially in other fields of regional anaesthesia. Because of increasing use of the faster, small incision technique in cataract surgery, topical anaesthesia has become more and more popular compared to retrobulbar/peribulbar anaesthesia. Altogether 2698 patients were enrolled into the present thesis studies. The relation of haemorrhage complications and risk factors was investigated in 1383 retrobulbar/peribulbar block patients. The suitability of ropivacaine 0.2% in retrobulbar/peribulbar block was compared to lidocaine 1% in patients with laser treatment. The effect of adding hyaluronidase to the local anaesthetic mixture was tested by using the known effective concentration of 7.5 IU/mL against the ordinary concentration used at this hospital, 3.75 IU/mL and against no hyaluronidase. The surgical difficulties andcomplications and patient satisfaction were investigated, while the surgeon was converting from operating under retrobulbar/peribulbar anaesthesia to topical anaesthesia. In another study on topical anaesthesia, lidocaine was added intracamerally in order to improve analgesia, and propofol sedation was given i.v. to improve patient satisfaction. Patients' use of acetylsalicylic acid or other nonsteroidal anti-inflammatory drugs or the duration of their preblock discontinuation did not affect the haemorrhage incidence registered by the anaesthesiologist. Compared to lidocaine 1%, ropivacaine 0.2% was associated with less depression of muscle activity (at 10 min P < 0.001 registered by the anaesthesiologist and at the end of the laser treatment P= 0.002) registered by the ophthalmologist, but with equal, but not sufficient level of analgesia registered by the ophthalmologist. Hyaluronidase improved akinesia (P < 0.001) and the success of the initial block (P < 0.001 between 0 IU/mL and 3.75 IU/mL, and P= 0.006 between 0 IU/mL and 7.5 IU/mL), but there was no difference between the two concentrations of hyaluronidase registered by the anaesthesiologist. By means of surgical outcome measures registered by the surgeon the topical anaesthesia group did not differ from the other groups in either of the cataract studies. In the first cataract surgery study, retrobulbar/peribulbar anaesthesia ensured better surgical analgesia (P < 0.001) registered by the ophthalmologist, but in spite of that the patients with bilateral operations preferred topical anaesthesia (P < 0.05). Under retrobulbar/peribulbaranaesthesia the cataract surgery wascompleted with less additional sedation (P < 0.01) as registered by the anaesthesiologist, faster (P < 0.001), and with fewer difficulties than under topical anaesthesia (4 versus 40%, P < 0.001) registered by the ophthalmologist. Propofol sedation of the patient did not alleviate the surgical difficulties registered by the ophthalmologist in the second cataract study, but otherwise the results were similar to those registered by the ophthalmologist in the first cataract study. There were significantly fewer surgical difficulties in the retrobulbar/peribulbar group (9.8%) than in the topical (26.0%, P= 0.004) or in the combined (topical anaesthesia combined with propofol sedation) groups (21%, P= 0.036) registered by the ophthalmologist. Additional sedatives were needed significantly more often in the topical group (15.6%) than in the retrobulbar/peribulbar group (2.6%, P= 0.002) registered by the anaesthesiologist. In the cataract studies, patient satisfaction was 96.1% and 99.4%, respectively. So the ophthalmologist found no difference in this respect between the study groups. In conclusion: Discontinuing medication with acetylsalicylic acid and other nonsteroidal anti-inflammatory drugs before retrobulbar/peribulbar block is not needed at all, but the same cannot be claimed about warfarin because of a lack of statistical information. In retrobulbar/peribulbar blocks for ophthalmic laser therapy the use of more concentrated solutions of local anaesthetics is suggested than ropivacaine 0.2% or lidocaine 1%. In retrobulbar/peribulbar blocks, hyaluronidase 3.75 IU/mL can be considered an essential and sufficient additive to the local anaesthetic solution. Cataract surgery can be performed under topical anaesthesia with as good a surgical outcome as under retrobulbar/peribulbar anaesthesia, but retrobulbar/peribulbar block minimises surgical difficulties. From the patient's point of view it seems to be beneficial to supplement topical anaesthesia, which does not always block all sensations during surgery, with small doses of sedative agents. This thesis is based on the following publications referred to in the text by their Roman numerals: Accepted by: Helsinki University Medical Faculty Finland, 2001 ISBN 952-91-3959-4