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 Table of Contents  
ORIGINAL ARTICLE
Year : 2022  |  Volume : 60  |  Issue : 1  |  Page : 6-10

A comparative study of intraocular pressure and hemodynamic changes during general and regional anesthesia in abdominal and lower-limb surgeries


1 Department of Ophthalmology, GS Medical College, Hapur, Uttar Pradesh, India
2 Department of Surgery, Saraswati Institute of Medical Sciences, Hapur, Uttar Pradesh, India
3 Department of Anaesthesia, GS Medical College, Hapur, Uttar Pradesh, India

Date of Submission12-Jul-2021
Date of Decision16-Nov-2021
Date of Acceptance06-Dec-2021
Date of Web Publication22-Mar-2022

Correspondence Address:
Dr. Bhavya Mehta
Department of Ophthalmology, G.S. Medical College, Pilkhuwa, Uttar Pradesh
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/tjosr.tjosr_101_21

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  Abstract 


Context: In general anesthesia, intubation/extubation and use of succinylcholine elevate intraocular pressure (IOP). Elevation of IOP during anesthesia may be detrimental to patients with preexisting ocular conditions such as glaucoma and uveitis. Regional anesthesia (spinal) lowers mean arterial and may lead to hemodynamic changes. Aims: We aimed to study changes in IOP and mean arterial pressure (MAP) in patients undergoing abdominal and lower-limb surgery following general and regional anesthesia. Setting and Design: A prospective comparative nonrandomized study was done. One hundred and twenty patients were randomly allocated to receive either general (Group A, n = 60) or regional anesthesia (Group B, n = 60), respectively. An independent investigator recorded MAP and IOP (Perkins handheld tonometer). Statistics: A one-way repeated measures analysis of variance (ANOVA) was done to determine whether there are any significant differences between the means of three or more levels of a within-subject factor (IOP and MAP) over time. Results: In Group A, there was a significant rise in IOP (ANOVA, P = 0.007) after general anesthesia over time. In Group B, the change in IOP (ANOVA, P = 0.219) was not statistically significant over time. However, there was a significant reduction in MAP over time. Between the groups, the mean change in IOP was significantly higher in patients in Group A and mean MAP significantly lower in Group B, respectively. Conclusion: Patients with glaucoma, uveitis, and cardiovascular diseases should have IOP monitoring prior to deciding the type of anesthesia and after anesthesia for lower-limb and abdominal surgeries. Sudden loss of vision after anesthesia needs immediate attention.

Keywords: General anesthesia, glaucoma, intraocular pressure, regional anesthesia


How to cite this article:
Saquib M, Singh DP, Kumar S, Mehta B, Malik A, Bhargava R. A comparative study of intraocular pressure and hemodynamic changes during general and regional anesthesia in abdominal and lower-limb surgeries. TNOA J Ophthalmic Sci Res 2022;60:6-10

How to cite this URL:
Saquib M, Singh DP, Kumar S, Mehta B, Malik A, Bhargava R. A comparative study of intraocular pressure and hemodynamic changes during general and regional anesthesia in abdominal and lower-limb surgeries. TNOA J Ophthalmic Sci Res [serial online] 2022 [cited 2022 May 29];60:6-10. Available from: https://www.tnoajosr.com/text.asp?2022/60/1/6/340333




  Introduction Top


General and regional anesthesia or a combination of these is used for most surgical procedures. Both techniques have some pros and cons. During general anesthesia, endotracheal intubation impacts the hemodynamics and intraocular pressure (IOP) of patients. It has been observed that some pharmacological agents used in general anesthesia may lower IOP; the etiology of IOP reduction is multifactorial and is believed to be due to relaxation of extraocular muscle tone, depression of the central nervous system, reduction in mean arterial pressure (MAP), and improvement of aqueous outflow.[1],[2] However, laryngoscopy procedures, endotracheal intubation and extubation, and use of succinylcholine and ketamine elevate IOP during general anesthesia.[3]

Raised IOP is one of the most important risk factors for development of glaucoma. There exists an equilibrium between the production and drainage of aqueous. Most researchers believe that there is a correlation between IOP and MAP. Sudden rise in IOP is often an undesirable event leading to mechanical stress and ischemic effects on the retinal nerve fiber layer.

IOP changes are known to occur during general and regional anesthesia. An acute elevation in IOP may be catastrophic.[4] Succinylcholine is a depolarizing muscle relaxant with a rapid but short duration of action. It provides excellent muscle relaxation to facilitate intubation of the trachea.[5] However, it causes a transient increase in IOP (7–12 mmHg) lasting for about 4–5 min.[6] Indirect laryngoscopies, intubation, and extubation are also associated with an increase in MAP and IOP due to mechanical stimulation of soft tissues with laryngoscope and endotracheal tube blades.[5],[7] Similarly, an increase in IOP during extubation is due to straining, coughing, and vomiting due to an increase in central venous pressure.

During regional anesthesia, IOP changes and hemodynamic changes can be minimized if the patient is well hydrated, and the patient is given an optimum dose of bupivacaine.

The aim of the present study was to evaluate IOP and hemodynamic changes in patients with general anesthesia during intubation and extubation and regional anesthesia and to study the correlation between IOP and MAP so that ocular complication secondary to raised IOP could be minimized.


  Materials and Methods Top


An interventional, nonrandomized, comparative study was performed at a tertiary care teaching hospital in the northern part of the subcontinent from March 2019 to February 2020. The trial was first approved by the institutional review board. Later, the local ethics committee approved it. The study conformed to the Transparent Reporting of Evaluations with Nonrandomized Designs statement. All participating patients signed a written informed consent. The study followed the tenets of the declaration of Helsinki.

The patients were first examined by an independent investigator (not a study physician) who monitored cardiac parameters (heart rate [HR] and MAP). A detailed ophthalmic history was taken in all patients preoperatively by a single ophthalmologist (not a study surgeon); the ophthalmologist also recorded IOP in all patients in the operating room with a Perkins handheld tonometer.

Patients undergoing abdominal and lower-limb surgeries (n = 120) were randomly allocated to receive either general anesthesia (Group A, n = 60) or regional anesthesia (Group B, n = 60), respectively. Anesthesia was administered by a single anesthetist who was masked to the information obtained by the independent investigator.

The ophthalmologist was also masked to the type of anesthesia. Patients were randomly allocated to one of the two groups (general or regional anesthesia) by a parallel assignment. The allocation codes were generated by a DOS-based software in the department of community medicine. The allocation codes were sealed in blue envelopes and were opened by health-care personnel not involved in patient care.

Procedure to measure intraocular pressure with Perkins tonometer

The tonometer was checked for calibration. One eye of each patient was randomly selected for measuring IOP. IOP was measured in supine position [Figure 1]. The patient was instructed to look straight ahead or slightly upward and, if necessary, a fixating target was used. The eye was anesthetized with 2–3 drops each of proparacaine to reduce the movements of the lids during examination. A fluorescein paper strip was placed near the external canthus in the lower conjunctival sac and removed when the lacrimal fluid was sufficiently colored. All patients were repeatedly instructed to keep their eyes wide open during the examination. If required, the eyelids were held open by the examiner's fingers without applying any undue pressure to the eye. The force was adjusted by turning the thumbwheel until the inner margins of the semi-circles coincide. The tonometer was removed from the eye and the reading was noted. The large divisions of the scale represented 0.2 g. The reading was multiplied by ten to give the IOP in millimeters of mercury (mmHg). Readings were repeated until a steady value was obtained. A drop of antibiotic was instilled in both eyes after recording IOP.
Figure 1: Figure 1 a Recording of intraocular pressure with Perkins handheld tonometer and Figure 1 b Fundus photograph showing ischemic optic neuropathy following regional anesthesia in a patient with cardiovascular disease

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Preanesthetic medication

Premedication was given to all patients. Alprazolam 0.25 mg was given orally the night before surgery. Injection midazolam 0.01–0.1 mg/kg body weight and injection pethidine 0.5–1.0 mg/kg body weight was administered intravenously before shifting the patient to the operation theater.

Patients in Group A were induced with injection of thiopentone sodium (3–5 mg/kg) IV followed by injection succinylcholine. Direct laryngoscopy was done, and cuffed endotracheal tube was inserted into the trachea of patients. Maintenance with nitrous oxide, oxygen, and halothane was done. Reversal was done by injection neostigmine and injection glycopyrrolate.

In Group B, subarachnoid block with bupivacaine heavy 0.5% was given in L3-L4 spinal space by a 25-gauge spinal needle.

IOP was recorded at baseline, prior to intubation, after intubation, and at the end of surgery in Group A. In Group B, IOP was recorded at baseline, prior to subarachnoid block, after subarachnoid block, and at the end of surgery.

The cardiac readings were taken at the following intervals: baseline before premedication (T0), before induction (T1), after induction (T2), just before intubation (T3), just after extubation, and the end of surgery (T4), respectively.

Statistics

Statistical analysis was performed using IBM statistical software, SPSS Statistics version 27 (IBM Inc. NY, USA.). Normally distributed data were expressed as mean ± standard deviation. Data were expressed as median (interquartile range, IQR), when assumption of normality was violated (Shapiro–Wilk test, P < 0.001). Outliers were identified on visual inspection of the box plots. Chi-square tests were used for proportions. Independent t-tests were done to ensure group similarities at baseline. A one-way repeated measures analysis of variance (ANOVA) was done to determine whether there are any statistically significant differences between the means of three or more levels of a within-subject factor (IOP, HR, blood pressure [BP], and MAP) over time. P < 0.05 was considered statistically significant. The Pearson product-moment correlation was used to determine the strength and direction of a linear relationship between two continuous variables (IOP and MAP). Pearson correlation coefficient, denoted as r (i.e., the italic lowercase letter r), measured the strength and direction of a linear relationship between two continuous variables. Its value can range from −1 for a perfect negative linear relationship to +1 for a perfect positive linear relationship. A value of 0 indicates no relationship between two variables.


  Results Top


The mean age of patients in Group A was 29.3 ± 7.5 and in Group B was 30.5 ± 9.1 years (range, 20–54 years). The difference in age was not statistically significant (paired t-test, P = 0.375).

There were 37 males in Group A with a male–female ratio of 1:0.6 and 43 males in Group B with a male–female ratio of 0.7:1, respectively (Chi-square test, P = 0.161).

The IOP was comparable between the two groups at baseline (independent t-test, P = 0.340). The mean change in IOP in Group A is depicted in [Table 1] and [Figure 2]a.
Table 1: Mean change in intraocular pressure over time in Group A

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Figure 2: a) Mean change in intraocular pressure over time Group A. b) Mean changr in intraocullar pressure over time in Group B. c) Mean change in arterial pressure over time in Group A. d) Mean change in arterial pressure over time in Group B

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Within-group comparison

There was a significant variation in IOP over time in Group A (ANOVA, P = 0.001).

The mean change in IOP in Group B is depicted in [Table 2] and [Figure 2]b.
Table 2: Mean change in intraocular pressure over time in Group B

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Within-group comparison

The variation in IOP over time was not statistically significant in Group B over time (ANOVA, P = 0.075).

Between-group comparison

At the end of surgery, the mean IO was significantly higher (independent t-test, P = 0.029) in Group A than in Group B.

[Table 3] and [Figure 2]c show the change in MAP over time in patients in Group A. The change in MAP was statistically significant (ANOVA, P = 0.001).
Table 3: Mean change in mean arterial pressure in Group A over time

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[Table 4] and [Figure 2]d show the change in MAP over time in patients in Group B. The change in MAP was statistically significant (ANOVA, P = 0.001).
Table 4: Mean change in mean arterial pressure in Group B over time

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In Group A, there was a statistically significant correlation [Figure 3] between changes in IOP and MAP during GA (Pearson's correlation coefficient, r = 0.233, P = 0.001). In Group B, the correlation between IOP and MAP was not statistically significant (Pearson's correlation coefficient, r = 0.041, P = 0.524).
Figure 3: Scatter plot showing correlation between intraocular pressure and mean arterial pressure in Group A and Group B, respectively

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  Discussion Top


A nonrandomized comparative study was done in the departments of ophthalmology and anesthesia at a tertiary care teaching hospital in the northern part of the Indian subcontinent. Our study evaluated IOP and hemodynamic changes between general and regional anesthesia in patients undergoing abdomen and lower-limb surgeries, respectively. The results of our study suggest that intubation procedures and succinylcholine use during general anesthesia lead to elevation of IOP. The mean increase in IOP in the general anesthesia group (Group 1) was 6.5 ± 2.3 mmHg as compared to 1.1 ± 0.7 mmHg in the regional anesthesia group (Group 2), respectively (P = 0.001). On the other hand, the reduction in arterial pressure in patients in the regional anesthesia group after 30 min was 8.4 ± 16.8 mmHg as compared to 1.8 ± 1.4 mmHg in the general anesthesia group (P = 0.009), respectively.

Transient acute elevations of IOP (IOP spikes) may be deleterious to the retinal nerve fiber layer and the optic disc. Acute elevation of IOP is known to decrease perfusion pressure in human eyes leading to marked reduction in blood flow through the retina and optic nerve head. However, normal eyes have autoregulatory mechanisms to deal with such situations.[6] In contrast, eyes with vessels that are significantly damaged due to glaucoma, uveitis, or prone to anterior ischemic optic neuropathy are likely to have exhausted their autoregulatory mechanisms even at normal pressures.

General anesthesia is known to induce angle-closure glaucoma (ACG).[5],[7] Ates et al. reported two cases of bilateral simultaneous ACG following cholecystectomy and craniotomy for tumor resection under general anesthesia.[8] Raj et al. reported a case of bilateral ACG in a female patient who underwent hysterectomy under general anesthesia.[9]

It is likely that symptoms of acute ACG may be overlooked or missed in a sedated or comatose patient. Any patient who has a redness of eye and a sudden vision loss within the postoperative period should be examined urgently.

Bijker et al. found that intraoperative hypotension occurs with anesthesia administration in 5%–99% of patients.[10] Perioperative hemodynamic instability may be associated with vascular complications in the heart and eyes. Studies have found that a decrease of 40% in MAP during surgery is associated with cardiovascular events in high-risk patients; episodes of intraoperative MAP of <55 mmHg are associated with acute kidney injury and myocardial injury in noncardiac surgeries.[11]

During GA, a hypertensive response is associated with laryngoscopy and tracheal intubation because of a catecholamine release.[12]

Hypotension is the most encountered complication after spinal anesthesia. Carpenter et al. found that hypotension developed in about 33% of patients after spinal anesthesia; factors associated were age, level of spinal puncture, baseline BP, peak block height, and combination with general anesthesia.[13],[14]

Postoperative ischemic optic neuropathy is a vision-threatening complication that can occur following cardiothoracic surgery, instrumented spinal fusion, and head-and-neck surgery.[15],[16],[17] Various factors have been implicated in ischemic optic neuropathy such as hypotension, anemia, increased venous pressure, prone positioning during anesthesia, increased cerebrospinal fluid, and direct ocular compression.[18] It has been observed that prone position during anesthesia leads to increased orbital venous pressure through an increase in abdominal venous pressure, thus increasing resistance to local blood flow.[19]

Our study had several limitations. The sample size in each group was relatively small (n = 60) leading to type II error and consequently overestimation. We acknowledge the inherent limitations related to nonrandomized study design like selection bias.


  Conclusion Top


General and regional anesthesia have some disadvantages. Rise in IOP during intubation and succinylcholine use is undesirable in patients with preexisting glaucoma and history of uveitis; this may lead to vision-threatening complications. Hypotension during regional anesthesia may cause optic nerve head ischemia and optic neuropathy.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

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Raj KM, Reddy PA, Kumar VC. Bilateral angle closure glaucoma following general anesthesia. J Pharm Bioallied Sci 2015;7 Suppl 1:S70-1.  Back to cited text no. 9
    
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Bijker JB, van Klei WA, Kappen TH, van Wolfswinkel L, Moons KG, Kalkman CJ. Incidence of intraoperative hypotension as a function of the chosen definition: Literature definitions applied to a retrospective cohort using automated data collection. Anesthesiology 2007;107:213-20.  Back to cited text no. 10
    
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Gill B, Heavner JE. Postoperative visual loss associated with spine surgery. Eur Spine J 2006;15:479-84.  Back to cited text no. 16
    
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Lee LA, Roth S, Posner KL, Cheney FW, Caplan RA, Newman NJ, et al. The American Society of Anesthesiologists Postoperative Visual Loss Registry: Analysis of ninety-three spine surgery cases with postoperative visual loss. Anesthesiology 2006;105:652-9.  Back to cited text no. 18
    
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    Figures

  [Figure 1], [Figure 2], [Figure 3]
 
 
    Tables

  [Table 1], [Table 2], [Table 3], [Table 4]



 

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