Anesth Analg 2003;97:471-474
© 2003 International Anesthesia Research Society
ANESTHETIC PHARMACOLOGY
Intraocular Pressure Changes During Laparoscopy in Patients Anesthetized with Propofol Total Intravenous Anesthesia Versus Isoflurane Inhaled Anesthesia
Hany A. Mowafi, MB Bch, MSc, MD*,
Abdulmohsin Al-Ghamdi, MD*, and
Adel Rushood, MD
Departments of *Anesthesia and
Ophthalmology, Faculty of Medicine, King Faisal University, Dammam, Saudi Arabia
Address correspondence and reprint requests to Dr. Hany A. Mowafi, Anesthesiology Department, King Fahd University Hospital, PO Box 40081, Al-Khobar 31952, Saudi Arabia. Address e-mail to hany_mowafi{at}hotmail.com
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Abstract
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We examined intraocular pressure (IOP) changes during gynecologic laparoscopy performed under either thiopental-isoflurane anesthesia or total IV propofol anesthesia. Forty adult women with no preexisting eye disease scheduled for gynecologic CO2 insufflation laparoscopy were included in the study. Heart rate, mean arterial blood pressure, peak and plateau airway pressure, ETCO2, and IOP (using a Schioetz tonometer) were measured at defined intervals during the procedure. IOP decreased significantly after the induction of anesthesia in both groups, and remained so throughout the procedure in the propofol group. In the isoflurane group, however, IOP was increased significantly above the preinduction level after pneumoperitoneum with head-down position. There was no correlation between IOP and blood pressure or airway pressure. In conclusion, propofol total IV anesthesia may be a better choice for laparoscopic surgery should control of IOP be a concern.
IMPLICATIONS: In this study, we examined the effect of two anesthetic techniques on the intraocular pressure changes during laparoscopic surgery in healthy subjects. Propofol IV anesthesia protected against increases in intraocular pressure with pneumoperitoneum and head-down position.
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Introduction
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Laparoscopic surgery is associated with many physiological changes that tend to increase the intraocular pressure (IOP) (1,2). Some authors consider laparoscopic surgery with head-down position contraindicated in patients with ocular hypertension (3). Others found that adequate general anesthesia compensated for increased IOP in young subjects with no preexisting eye disease (4). Propofol was found to decrease IOP unrelated to changes in heart rate (HR) or arterial blood pressure (BP) (5). The aim of this study was to investigate IOP changes during gynecologic laparoscopy performed under either isoflurane inhaled anesthesia or total IV propofol anesthesia (TIVA).
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Methods
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After local research committee approval and informed patient consent, 40 adult female patients, ASA physical status I or II, scheduled for elective gynecologic laparoscopy were included in the study. Patients were excluded if they were >60 yr of age, had a body weight >150% of their ideal body weight using Broca’s index, had acute or chronic eye disease, or were receiving any medication known to alter IOP. Patients were randomly allocated using an online research randomizer (http://www.randomizer.org) into 2 equal groups (20 patients each) to receive either isoflurane inhaled anesthesia or propofol TIVA. Surgery was performed early in the morning to avoid diurnal variations in IOP.
All patients were premedicated with 10 mg of diazepam orally 90 min before the induction of anesthesia. In the isoflurane group, anesthesia was induced with thiopental 5 mg/kg and maintained with isoflurane 1%–2%. In the propofol group, anesthesia was induced with propofol 2.5 mg/kg and maintained with propofol infusion 5–10 mg · kg-1 · h-1. Isoflurane and propofol concentrations were adjusted to maintain mean arterial BP within 20% of the preinduction value.
In both groups, patients were given fentanyl 2 µg/kg at induction and atracurium 0.5 mg/kg to facilitate tracheal intubation, which was done when complete suppression of train-of-four stimulation of the ulnar nerve occurred. Further boluses of atracurium 0.15 mg/kg were given depending on the degree of neuromuscular block. A peripheral nerve stimulator (Innervator; Fisher & Paykel Healthcare, Auckland, New Zealand) was used to monitor neuromuscular transmission. The lungs of the patients were mechanically ventilated with a volume-cycled ventilator (Narcomed 2B; Dräger Medical Inc., Telford, PA). In both groups, oxygen in nitrous oxide (fraction of inspired oxygen = 0.4) was administered using a semiclosed low flow circle system. Minute volume was set to maintain ETCO2 at 4–4.7 kPa throughout the procedure.
Pneumoperitoneum was created by intraperitoneal insufflation of CO2 with the patient in the supine position. Throughout surgery, intraperitoneal pressure was maintained automatically at 15 mm Hg by a CO2 insufflator (Therm-Pneu electronic; WISAP America Inc., Lenexa, KS). Fluid administration of lactated Ringer’s solution was standardized at 4 mL · kg-1 · h-1. A Capnomac Ultima respiratory in-line monitor (Datex, Finland) was used to monitor inspired and expired gases and ventilation variables in addition to plethysmographic oxygen saturation. An automatic noninvasive monitor (Dinamap; Critikon, Tampa, FL) was used to monitor HR and BP. IOP was measured with a Schioetz tonometer by an ophthalmologist who was unaware of the anesthetic technique. For this, topical oxybuprocaine hydrochloride 0.4% was applied to the cornea before measurement.
Mean arterial BP, HR, peak and plateau airway pressures (Paw), ETCO2, and IOP were recorded at the following time points:
- T1: Before the induction of anesthesia.
- T2: After the induction of anesthesia, supine, horizontal position, mechanically ventilated, before pneumoperitoneum.
- T3: After the pneumoperitoneum had been established.
- T4: Pneumoperitoneum established, with a 15°–20° head-down tilt.
- T5: Pneumoperitoneum established, after return to the horizontal position.
- T6: After the pneumoperitoneum had been evacuated.
- T7: In the recovery room, half-seated, 20 min after tracheal extubation.
After each change in position and intraperitoneal pressure, a 5-min period was allowed for stabilization before measurements were made.
Sample size was selected to detect a maximal IOP difference of 30% between the 2 groups with type I error of 0.05 and type II error of 0.20. Power analysis was based on a pilot study of 10 patients, using an online calculator for sample size (http://www.obg. cuhk.edu.hk/researchsupport/sample). Data were tested for normal distribution using the Kolmogorov-Smirnov test. Differences between the groups in demographic data were analyzed using unpaired t-test. For comparison of different observations within and between the groups, data were first analyzed by repeated measures analysis of variance, and differences were then calculated by post hoc testing (Newman-Keuls test). The association between Paw and IOP was tested for by simple linear regression. Analysis was performed using Jandel Sigma Stat software version 2.01 for Windows. Data were presented as mean ± SD in the text and Table 1, and as mean ± 95% confidence intervals in Figure 1.
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Figure 1. Changes in intraocular pressure (IOP) in the isoflurane and propofol groups. Measurements were made before anesthesia (T1), after anesthetic induction (T2), after pneumoperitoneum (T3), after head-down position (T4), after return to the horizontal position (T5), after evacuation of pneumoperitoneum (T6), and in the recovery room (T7). Vertical bars denote 0.95 confidence intervals. *Significance difference in comparison to T1. #Significant difference between the isoflurane and propofol groups.
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Results
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There were no significant differences between the two groups with respect to age, weight, height, duration of the procedure and the preoperative IOP (Table 1). There were also no significant differences in the baseline HR and BP.
Induction of anesthesia reduced IOP in both groups (Fig. 1); the reduction was more marked in patients who received propofol than in those who received isoflurane anesthesia (P < 0.001). In the isoflurane group, IOP increased significantly after pneumoperitoneum (T3 versus T2, P < 0.05). The head-down position was associated with a more marked increase in the IOP (T4 versus T2, P < 0.001), and exceeded the preoperative IOP (T4 versus T1, P < 0.05). In the propofol group, however, IOP did not increase after pneumoperitoneum or with head-down position, and was at all times less than in the isoflurane group.
With both anesthetic techniques, control of BP and ETCO2 was possible. There was no association between IOP and Paw in either the propofol group (r = 0.002, P = 0.9) or the isoflurane group (r = 0.07, P = 0.4).
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Discussion
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Laparoscopic surgery is associated with physiological changes that tend to increase IOP. These include increase of BP, increase of ETCO2, and an increase in central venous pressure (CVP) resulting from intrathoracic pressure increase and postural changes (2,6,7). These changes, together with a report of a profound increase in IOP with abdominal CO2 insufflation and head-down position in a patient with ocular hypertension (3), have raised concerns that laparoscopic surgery may aggravate intraocular hypertension in susceptible patients.
Mean arterial BP was maintained in the current study within 20% of the preoperative value. Within this range, changes in arterial BP are poorly transmitted to the eye (8). Although a good correlation was found between ETCO2 and IOP (2), ETCO2 was maintained constant in our study by varying the minute volume ventilation. The absence of correlation between plateau Paw and IOP changes in this study suggests that changes in CVP, because of pneumoperitoneum and position, may have been the main factor affecting IOP during laparoscopy. Although CVP was not measured in this study because of ethical concerns about the use of a central line, the relation between CVP and IOP has been shown by others (9).
Establishment of anesthesia, whether inhaled or TIVA, in the present study before pneumoperitoneum, resulted in a significant decrease in IOP from the preoperative values. This anesthetic effect on IOP has been well documented during non-ophthalmic surgery, and is unrelated to changes in BP or HR (10–12).
In the isoflurane group, CO2 insufflation resulted in an increase of IOP, which reached its maximum with the establishment of the Trendelenburg position. This increase in IOP, although statistically significant, may be clinically insignificant because it remained within the normal diurnal range. These findings are similar to those of Lentschener et al. (4,13), who found laparoscopic surgery safe in young patients with no preexisting eye disease. Further studies are necessary, however, to examine the effect of pneumoperitoneum and posture during laparoscopy in older patients with preexisting eye disease.
Propofol TIVA, in contrast to isoflurane, prevented the increase in IOP with pneumoperitoneum and the head-down position. The mechanism of this propofol taming effect on IOP during laparoscopic surgery is not known, but may be attributable to the effect of propofol on arginine vasopressin (AVP), which is markedly increased during laparoscopy especially postinsufflation and Trendelenburg position (14–16). AVP and its synthetic derivative desmopressin produce a dose-dependent increase in IOP (17,18). Propofol inhibits the somatodendritic AVP release from the supraoptic nucleus (19) and may therefore prevent the increase of IOP associated with pneumoperitoneum and the Trendelenburg position. Inhaled anesthetics, however, do not affect the release of AVP (20). Further investigations are required to prove this mechanism.
We conclude that: 1) laparoscopic surgery with head-down position increase IOP. 2) This increase of IOP is within the normal diurnal range in young patients without preexisting eye disease. 3) Further studies are required to prove the safety of laparoscopy in older patients and those with preexisting eye disease. 4) Propofol TIVA has an IOP taming effect during laparoscopy and may be preferred if control of IOP is a concern.
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Accepted for publication February 26, 2003.
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Abstract
Introduction
