Intraocular Pressure Changes To Peribulbar Anaesthesia And The Effect Of Digital Massage

摘要

Background: To observe the effects of peribulbar injection of local anaesthetic agent and digital massage on intraocular pressure in patients undergoing elective cataract surgery. Methods: 35 eyes of patients for elective cataract surgery were recruited for the study. Each received a fixed volume local anaesthetic agent by the peribulbar technique and subsequent external digital massage. IOP was measured immediately before and after the injection was given, and at 5and 10 minutes of digital massage.Results: 32(91.47%) of the eyes had a rise in intraocular pressure. There was a mean IOP rise of 8.68mmHg from a mean pre-injection IOP of 11.26 mmHg. This was statistically significant, (P=0.000).The mean IOP recorded at 5 and 10 minutes of massage were 6.57mmHg and 3.37mmHg.The fall from the immediate post injection pressure were statistically significant, (P=0.000).Conclusion: Our findings show that intraocular pressure rises in great majority of eyes following peribulbar injection for cataract extraction. External digital massage is effective in lowering this pressure. Introduction Peribulbar injection of local anaesthetic agent is one of the techniques of anaesthesia in cataract surgery 1,2 . It is used to achieve akinesia and anaesthesia of the globe. It involves injection of the agent into the extraconal space, a tissue compartment3. This compartment is confined centrally by the muscle cone, laterally by the periosteum and bony wall of the orbit, and anteriorly by the orbital septum and conjunctiva. This method of block was developed to avoid some of the complications associated with retrobulbar anaesthesia 4,5 in which the agent is deposited in the intraconal space. Because of the confinement of these boundaries, orbital pressure rise which is transmitted to the globe thus raising the intraocular pressure (IOP) is expected. The extent to which the IOP rises following the injection, and external digital massage reduces it in Nigerians is what this study is designed to show. Materials And Methods The study was carried out on 35 eyes of 35 patients admitted for elective cataract surgery. During the period of the study, all admitted patients were selected who met the requirements. Patients with a history of glaucoma, previous ocular surgery , secondary cataract and those under general anaesthesia were excluded from the study. Informed consent was obtained from the patients .Each patient was placed in a prone position. The periocular and preauricular areas were wiped with spirit swab. 5ml of 2% Lignocaine with adrenaline (1:100,000 dilution) was administered into the peribulbar space through two injection sites. 3ml was delivered through the skin from the junction between the middle and lateral 1/3rd of the inferior orbital margin. 2ml was given at the junction between the middle and nasal 1/3rd of the superior orbital margin. 5ml of the agent was used for facial block by the O'Brien's method to achieve orbicularis akinesia. A 23guage needle measuring 30mm was used for the injections, mounted on a ten ml syringe. The IOP was measured with the handheld Perkin's applanation tonometer immediately before and after the injections. Digital massage was then commenced. The massage was carried out with the index and middle fingers of both hands, with the former resting on the cornea. Firm pressure was applied for two seconds and then released for the next two seconds and continued in this manner. The IOP was taken at the end of 5 and 10 minutes of massage. All the procedures and observations were carried out by the same observer for uniformity and elimination of interobserver error. The results were analysed using the Student's T-test. Results 35 eyes of 35 patients were studied. The results are summarised in tables 1 and 2.