Cataract surgery under local anaesthesia may provoke anxiety because of the fear of the procedure itself and concerns about the outcome. Anxiety and stress are associated with systemic effects which include tachycardia, hypertension and dysrhythmias. Increased preoperative anxiety has been correlated with increased postoperative pain and increased analgesic requirement .
Plasma cortisol increases as a response to stress caused by retrobulbar block in cataract surgery and there is elevation of plasma glucose by both a direct mechanism (increasing hepatic glucose production and insulin resistance) and an indirect mechanism (increasing the effects of epinephrine and norepinephrine) . Analgesic drugs given intraoperatively can decrease metabolic and hormonal response by eliminating pain . The aim of this study was to determine the effect of intravenous (i.v.) fentanyl on the plasma cortisol response associated with retrobulbar block and intraocular surgery.
One-hundred-and-seven patients who underwent phacoemulsification of the lens of the eye under retrobulbar anaesthesia were included in the study. Diabetic patients and patients on chronic medication such as analgesics and hormones were excluded. The nature of the study was explained to each patient and informed consent was obtained.
On arrival in the anaesthetic room, a venous cannula was inserted for collection of blood samples. All patients received a balanced electrolyte solution or 0.9% sodium chloride by continuous infusion. The patients were randomly allocated to two groups in a single-blinded manner. There were 54 patients in the retrobulbar block group and 53 in the retrobulbar block + fentanyl group. The retrobulbar block group received only retrobulbar block anaesthesia using a mixture of bupivacaine 0.5% 1 mL and of lidocaine 2% 1.5 mL. In the retrobulbar block + fentanyl group, i.v. fentanyl 2 μg kg−1 was administered slowly 5 min before the retrobulbar injection.
The surgical procedure was carried out according to the standard technique. Patients underwent phacoemulsification and posterior chamber lens implantation through a 3.2 or 4.0 mm clear corneal incision and no suture was used. Mean arterial pressure, heart rate (HR) and oxygen saturation were monitored. Oxygen (4 L min−1) was given via nasal cannulae. As cortisol concentrations exhibit a circadian rhythm with decreasing levels early in the morning, all operations were performed between 9.00 a.m. and 12 noon.
Seven blood samples were taken from each patient: (a) 15 min before the block; (b) 5 min after the block; (c) during the phacoemulsification procedure; (d) at the end of surgery; (e), (f) and (g) 30, 60 and 120 min, respectively after the completion of surgery. The samples were collected in tubes containing ethylenediamine tetra-acetic acid, centrifuged immediately and the supernatant stored at −20°C. Blood glucose was measured enzymatically and cortisol concentration by radioimmunoassay.
The results within the groups were evaluated by the one-way analysis of variance post hoc test with Tukey correction. Further comparisons between groups at individual times were made using the unpaired t-test. P < 0.05 was considered as statistically significant.
Seven patients in the retrobulbar block group and five patients in the retrobulbar block + fentanyl group were excluded because of failure to collect blood samples at appropriate times. Four patients in the retrobulbar block group and three patients in the retrobulbar block + fentanyl group were excluded because of intervention with antihypertensive drugs.
The groups were similar with respect to age, weight, number of patients with hypertension and duration of operation (Table 1). Plasma cortisol concentrations were higher in the retrobulbar block group than in the retrobulbar block + fentanyl group at the end of surgery and 30, 60 and 120 min thereafter (P < 0.05) (Fig. 1). The levels of cortisol in the first three measurements were not different statistically between the groups. Plasma cortisol increased from 356 mmol L−1 at baseline to 670 mmol L−1 (normal range: 250-615 mmol L−1) at 30 min postoperatively (P < 0.05). Plasma cortisol remained stable in the retrobulbar block + fentanyl group.
The plasma glucose concentrations during phacoemulsification, after surgery, 30 and 60 min after operation were significantly higher in the retrobulbar block group compared to the retrobulbar block + fentanyl group (P < 0.05). Blood glucose was normal at 120 min after operation. Mean arterial pressure and HR increased 5 min after administration of the block only in the retrobulbar block group (P < 0.05).
Plasma cortisol and glucose are considered to reflect the metabolic and hormonal response to stress. Cortisol levels change within minutes after stress whether physical (trauma, surgery and exercise), psychological (anxiety and depression) or physiological (hypoglycaemia and fever). The hormonal and metabolic response to cataract surgery mainly results from sympathoadrenal activity [3-7]. Intravenous fentanyl given before the retrobulbar block prevented an increase in plasma cortisol and glucose levels as a metabolic and hormonal response to pain and anxiety due to the administration of the block. In the current study, metabolic and hormonal responses have been found to be improved in patients receiving low dose fentanyl than in those not receiving fentanyl.
In conclusion, we have shown that hormonal and metabolic response to intraocular surgery under local anaesthesia may be decreased by the administration of fentanyl 2 μg kg−1 which is safe, provides a marked analgesic effect and reasonable sedation.
None of the authors has proprietary interest in any product mentioned in manuscript.
R. G. Sivaci
*Department of Anesthesiology, School of Medicine, Kocatepe University, Afyon, Turkey
†Department of Ophthalmology, School of Medicine, Kocatepe University, Afyon, Turkey
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1Presented as a poster at the XIXth Congress of the ESCRS, 3-7 September 2001, Amsterdam.© 2005 European Society of Anaesthesiology