Abstract
Objective
Perioperative eye injuries, although rare, often lead to great discomfort and anxiety for patients. The purpose of this study was to explore the incidence and related risk factors of perioperative eye injuries.
Methods
We retrospectively analyzed the records of inpatients who underwent nonocular surgery under general anesthesia with intubation between October 2006 and December 2008. Incidents of eye injuries were extracted from the Department of Anesthesiology Quality Assurance Database of Chang Gung Memorial Hospital. Univariate analysis and logistic regression modeling were used to assess the risk factors.
Results
A total of 75,120 cases were included in the study, of whom 17 (0.023%) were identified to have sustained perioperative eye injury. Corneal abrasion was the most common form of eye injury (10 patients; 59%). Patients who had been operated on in the prone position [odds ratio (OR), 10.8; 95% confidence interval (CI), 2.4–48.8] or lateral position (OR, 7.1; 95% CI, 1.2–43.2), those who had undergone head and neck surgery (OR, 9.3; 95% CI, 2.3–38.0), sustained intraoperative deliberate hypotension (OR, 8.7; 95% CI, 2.4–31.8), or who had preoperative anemia (OR, 5.3; 95% CI, 1.8–15.4) were more susceptible to eye injuries. The duration of anesthesia was not an independent risk factor (OR per hour, 0.9; 95% CI, 0.8–1.7).
Conclusion
In addition to head and neck surgery, operations in the lateral or prone position, preoperative anemia and intraoperative deliberate hypotension are also precipitating factors for perioperative eye injuries. For patients who are at high risk or for procedures that are apt to cause injury, preoperative recognition and intraoperative caution are of paramount importance.
Keywords
anesthesia, general; eye injuries; perioperative care; postoperative complications;
1. Introduction
With adequate protection, eye injuries are seldom seen in anesthetic practice. Although corneal abrasion is thought to be the most common type of eye injuries, the exact mechanisms by which it is caused are still unknown.1−4 Studies have shown that prolonged exposure of the cornea to the atmosphere,due to absence of voluntary protection as a consequence of the inability to close the eyelids following induction of general anesthesia, could be prevented.Nevertheless, the application of eye ointment did not significantly reduce the incidence of eye injuries.5−10 To survey the risk factors of perioperative eye injuries, Roth et al1 conducted a retrospective study consisting of 60,965 consecutive heterogeneous patients who underwent nonocular surgery. The overall incidence of perioperative eye injuries was 0.056%, and the authors concluded that long surgical procedures, lateral positioning, head and neck surgeries, general anesthesia and surgeries on Monday were independent risk factors.1 Studies that focused on perioperative vision loss indicated that incidence ranged from 0.001% in all nonocular surgeries to 0.2% in cardiopulmonary bypass or spinal surgery.11,12 Conversely, in one small prospective study, 3 of 100 patients (3%) whose eyes were left unprotected during general anesthesia had corneal abrasions with foreign body sensation and watering of the eyes postoperatively.5 Aside from direct injury and chemical harm by topical agents,8,13 decreased basal tear production during general anesthesia has been proposed as a possible mechanism,14 and diabetic patients have been shown to have reduced tear production and corneal sensi tivity.15 Hypertension, anemia, cardiac disease, prolonged hypotension, great blood loss, transfusion and hypoxia were also associated with vision loss.11,12,16,17 Here, we present a retrospective study that examined the risk factors of perioperative eye injuries after nonocular surgery in our anesthetic practice.
2. Methods
2.1. Study setting, patient sample and data collection
After obtaining approval from the institutional review board of Chang Gung Memorial Hospital, we analyzed all anesthetic cases who had received nonocular surgeries, recorded in the Quality Assurance (QA) Database of the Department of Anesthesiology, between October 1, 2006 and December 31, 2008. As is our practice, recorded on the anesthetic database card for each anesthetic patient were the following: demographic data, ASA physical status, comorbidities,types of surgery and anesthesia, details of intraoperative anesthetic management, urine output, blood loss, blood and fluid administered, and minor or major perioperative complications. The information on each database card was immediately entered into the QA Database using a computer in the operating room by anesthetic nurses after every anesthesia.Any incidents that occurred in the postanesthetic recovery unit were also recorded on these database cards and entered into the QA Database. On the next day, a trained continuous quality improvement coordinator compared the anesthesia records, database cards and computer database to ensure that all the entries were complete and correct.
In the postanesthetic recovery unit, each patient was asked if he/she had any ocular discomfort or changes in vision. In the postanesthetic visit on the day after surgery, the interviewer, a nurse anesthetist, conversed with the patient and queried about the discomforts centering on anesthesia-related complications, pursuant to a preformed questionnaire.Any type of eye injury possibly (or plausibly) related to anesthesia that occurred in the perioperative period was recorded in the QA Database, and successive treatments and outcomes were traced by members of the QA team.
Seventeen patients with perioperative eye injuries after nonocular surgery were identified, all of whom were inpatients who had received general anesthesia with endotracheal tube intubation. The anesthetic and hospitalization records of the patients suspected to have anesthetic-related eye injuries were reviewed by two anesthesiologists.In this study, ambulatory surgical patients wereexcluded due to limitation of follow-ups.
2.2. Methods of eye protection
In our clinical practice, eye protection was achieved primarily by adhesive taping of the eyelids with or without application of petroleum-based eye ointments following anesthetic induction. Some anesthesiologists taped the patient’s eyes soon after unconsciousness was induced. Tegaderm (3M, St Paul,MN, USA) was used selectively, instead of common adhesive tape, in patients who were operated on in the prone or lateral positions or who were undergoing head and neck surgery or prolonged procedures.In patients whose eyelids could not be taped (i.e. in some facial bone surgeries or in patients with facial burn injuries), only eye ointment was applied.Adequate positioning and intermittent checks were performed to prevent inadvertent eyeball compression in the prone or lateral position. After the operation was completed, the tape was removed before emergence from anesthesia was started.
2.3. Statistical analysis
SPSS version 16.0 (SPSS Inc., Chicago, IL, USA) was used for the statistical analyses. Patients were divided into two groups: those with eye injuries and those without eye injuries. Continuous variables are presented as mean ± standard deviation, and categorical variables as frequency and percentage.Univariate analysis was performed for every variable. The χ2 test or Fisher’s exact test was used for categorical variables; for variables with more than two categories, we used logistic regression. The t test or Wilcoxon rank sum test was applied for continuous variables.
Next, multivariate logistic regression modeling was conducted for variables with p < 0.05, which was considered statistically significant in this study. The odds ratios (OR) and their 95% confidence intervals (CI) were summarized, and the area under the receiver operating characteristic curve of the model was calculated.
The assessed variables included age, sex, body weight, duration of anesthesia (hour), blood loss(mL), ASA physical status, day of the week of surgery, surgical scheduling (emergent vs. non-emergent), surgical position (supine, prone, lateral, sitting), surgical method (head and neck surgery or not), anesthetic techniques applied (neck central vein catheterization, fiberoptic intubation, deliberate hypotension), comorbidities (history of cerebrovascular accident, ischemic heart disease, hypertension, end-stage renal disease, anemia, diabetes mellitus), and intraoperative transient hypotension (< 80/40 mmHg for less than 5 minutes) and hypoxia(PaO2 < 60 mmHg). Deliberate hypotension was established when deeper anesthetic levels, intravenous anesthetic agents, calcium channel blockers or beta-blockers were applied to achieve a mean blood pressure of around 50 mmHg during the operation, and this was recorded on the anesthetic database card as intraoperative deliberate hypotension”. Comorbidities were recorded according to the patient’s medical history, and anemia was defined as a preoperative hemoglobin level < 12 g/dL for adults and the respective standard levels for children according to their ages.
3. Results
A total of 75,120 cases were included in this study. Seventeen patients with eye injuries were identified, and 24 eyes were subjected to injury (Table 1). The overall incidence was 0.023%. Of these 17 patients, 9 were found to have injury in the postanesthetic recovery room, while the others complained of ocular discomfort in the wards. Corneal abrasion was the most common injury (10 patients). Five patients had conjunctivitis, one patient sustained prolonged blurred vision, and one patient suffered blindness.
Comparing the patients with eye injuries to those without eye injuries (Tables 2 and 3), we found that the former had been subjected to longer duration of anesthesia, and the percentages of head and neck surgery, preoperative anemia, the use of fiberoptic bronchoscope for intubation, intraoperative deliberate hypotension, and being in the prone position were greater; all of which were found to be risk factors. The variables independent of risks included age, sex, body weight, ASA physical status, comorbidities other than preoperative anemia, surgical scheduling, day of the week of surgery, neck central vein catheterization and intraoperative blood loss, transfusion, transient hypotension and hypoxemia.
The regression model (Table 4) shows that the patients who underwent head and neck surgery, who had preoperative anemia, who were subjected to intraoperative deliberate hypotension and who received operations in the lateral or prone position were more susceptible to eye injuries. The duration
of anesthesia and the use of fiberoptic intubation were not independent risk factors. The area under the receiver operating characteristic curve of this model is 0.770.
The two patients who were operated on in the lateral position suffered from bilateral eye injuries. Of the five patients operated on in the prone position, one had injury to both eyes, and the other four suffered injury to the eye pressing closest to the surface of the operating table. Ten patients developed eye injuries in the supine position, of whom four had injury to both eyes, five had injury to the right eye and one had injury to the left eye. After treatment suggested by ophthalmologists, all the patients recovered within 3 days without sequelae, except for one patient who developed permanent blindness in the right eye. Specific causes responsible for injury were found in four cases (23.5%), among which one was due to talcum powder accidentally falling into the patient’s eyes from the gloves of the anesthetic nurse during emergence from general anesthesia. In another patient, corneal injury was caused by incomplete closure of the eyelids due to presence of facial burn, although eye ointment had been applied. In one patient, the surgeon requested that the eyes be left uncovered after eye ointment application, and exposure keratopathy occurred after functional endoscopic sinus surgery. Unilateral blindness occurred in one patient who was operated on in the prone position. Intraoperative deliberate hypotension had been induced in this patient during lumbar spinal surgery, and central retinal artery occlusion was diagnosed by the ophthalmologist.
4. Discussion
Compared with the previous study conducted by Roth et al,1 we did not include ambulatory patients and those who had received anesthesia other than general anesthesia with tracheal intubation, and we also added some variables (including comorbidities, anesthetic techniques and intraoperative conditions) in the risk analysis. In addition to head and neck surgery and lateral or prone position, we found that preoperative anemia and application of intraoperative deliberate hypotension were also precipitating factors.
Sex and age were not associated with increased risk of perioperative eye injuries. While the volume, evaporation rate and osmolality of tears as well as basal tear production remain unchanged with age, an increase in tear flow and lower tear osmolality are observed in women under the age of 41.18 In the female patients in our study, none younger than 41 years old sustained eye injuries (p = 0.051). The roles of serum prolactin and sex hormone levels in the influence of tear production before and during menopause have been demonstrated.19 Whether or not reduction in basal tear production under general anesthesia is less prominent in young females may need further investigation. In contrast, premature infants, regardless of sex, exhibit reduced tear production until they are at a mean postconceptional age of 8.5 months.20 Eye injuries may be neglected in this population because they cannot communicate verbally. Concerning perioperative vision loss (POVL), male sex was found to be a significant positive predictor.12
Among the comorbidities examined, we found that only preoperative anemia was the most risky factor for perioperative eye injuries. Anemia is a common condition, but its importance has largely been ignored. One retrospective study showed that preoperative anemia was independently associated with increased mortality in non-cardiac surgery.21The association between anemia and POVL has also been demonstrated.12 The mechanism relating preoperative anemia with higher mortality and increased eye injuries is not yet understood, and the pros and cons of various methods of preoperative correction of anemia need further evaluation. Comorbidities of poor vascular qualities (cerebrovascular disease, ischemic heart disease, hypertension, end-stage renal disease, diabetes mellitus) did not have any significant influence on eye injuries in our study. This may be due to the small number of patients with eye injuries. Beta-blockers and the diuretic hydrochlorothiazide, which can decrease tear production, are often used to control cardiovascular diseases.22,23 However, more evidence is needed to evaluate the impacts of these diseases on perioperative eye injuries.
Deliberate hypotension is often employed to reduce bleeding from surgical fields to achieve better operative visualization, less surgical blood loss and less usage of blood products. However, our data suggest that this technique could increase the risk of eye injuries. The cornea is very sensitive to hypoxia. Deliberate hypotension may potentially cause hypoperfusion of ocular tissues, especially when atherosclerotic changes exist. Its influence on basal tear production is also of interest. The amount of intraoperative blood loss was not different between the two groups in our study, and according to our data, blood transfusion did not increase eye injuries.However, greater blood loss has been considered to be one of the risk factors of POVL,11,17 and POVL was found to be more prevalent in patients receiving transfusion in another study.12 We also surveyed intraoperative hypoxemic and transient hypotensive episodes, but no significant associations with eye injuries were found.
Patients undergoing head and neck surgery may have an increased risk of perioperative eye injuries.1 Since the surgical fields are near the eyes, direct trauma by the surgical team and inadvertent instillation of antimicrobial preparation solutions may occur.8,13,24 Zygomaticomaxillary complex fractures frequently coexist with minor (55%) and major (10%) ocular injuries, and preoperative ophthalmologic examination is warranted for postoperative comparison.25 Taping the eyelids close to the operative site is not allowed in some surgical procedures, and thus the risk of eye injuries increases. Many anesthetic procedures, although brief, are performed around patients’ head and neck (e.g. endotracheal intubation, laryngeal mask insertion, mask ventilation, airway placement, suction, central venous catheter insertion). Direct trauma by the tools the operators use and the miscellaneous articles they wear (watches, identification badges, stethoscopes, protective face shields) have been observed.13,26 Endotracheal intubation, compared with mask ventilation, was found to increase the risk of eye injuries, but it was not an independent risk factor due to the inability to distinguish its effect from that of general anesthesia, an independent risk factor demonstrated by that study.1 We found that fiber optic intubation had a greater risk initially, but the regression model revealed that it was not independent. Direct trauma by patients themselves may also occur when they rub their eyes after emergence from general anesthesia with the index finger to which a pulse oximeter probe is attached.27
Surgeries performed in the lateral and prone positions are associated with higher risks of eye injuries.1,9,16,17,28 The proposed mechanisms include direct compression of the orbit, increased intracranial pressure resulting from decreased venous return from the head and direct injury to the eyes during positioning.1,16 Whether or not the eye of the dependent side is more susceptible to injuries is controversial.1,9 In any event, proper positioning is imperative. In some posterior cervical spine and brain surgeries, pins are used to support the head.
Recently, we have employed a special cushion pad to allow the patient’s neck to rest in the neutral position in the prone position. Further studies are needed to evaluate the effects of these two methods on eye injuries. Many patients tend to lie laterally after emergence from anesthesia. Attention should be paid to prevent direct compression or trauma of the eyes because the patients may still be in a slightly sedated state. If vision loss occurs, electroretinography can be used to rule out or confirm perioperative ocular compression.29
Longer surgical duration was thought to be a risk factor for eye injuries.1,17 Corneal abrasion is unlikely to occur in patients undergoing anesthesia for less than 1 hour.5 Reduction in basal tear production becomes more prominent as the duration of anesthesia increases.14 However, the duration of anesthesia was not an independent risk factor according to our data. One possible explanation is that we excluded ambulatory patients who tended to undergo brief procedures. The roles of anemia and deliberate hypotension might be more causal with perioperative eye injuries as well.
Several techniques have been suggested and thoroughly reviewed for perioperative eye protection(e.g. manual closure of the eyelids, taping the eyelids shut, use of a protective ointment or aqueous gels, placement of methylcellulose, wearing protective goggles, tarsorrhaphy sutures, use of soft contact lenses, and protective corneal shells).24,30 Ointments have been associated with more postoperative morbidity (blurred vision).8 One of our cases falsely denied wearing contact lenses before the operation, and the patient complained of eye pains in the recovery room. The contact lenses were hard to remove due to dryness until normal saline irrigation was performed, and corneal abrasion was then diagnosed by the ophthalmologist. Geliperm, a sterile, transparent, pliant hydrogel dressing, has been proposed as a corneal protector during endonasal surgery and offers continuous observation of the eye.31 Bio-occlusive dressings, such as Tegaderm (3M) and Opsite (Smith & Nephew, Largo,FL, USA), can also be used to tape the eyelids shut.These dressings not only offer closure of the eyelids but also prevent drying of the cornea and exposure of the eyes to various contaminants. In one medical center, Tegaderm and Opsite are routinely used to protect the eyes during general anesthesia for head and neck surgeries, and perioperative ocular injuries occurred in only 12 of 40,089 cases (0.03%) over a 66-month period.24 The benefits of these new methods should be further investigated.Taping the eyelids may cause ocular injuries if patients open their eyes prematurely beneath the tape.4 Eyelid abrasions are also observed from time to time after removal of the tape.
POVL has the worst prognosis among perioperative eye injuries and often leads to claims for damage.One of our patients had POVL, in whom several risk factors could be found. This male patient was anemic, operated on in the prone position and subjected to intraoperative deliberate hypotension. His male sex and age (> 50 years), the operation he underwent (spinal surgery), and intraoperative blood transfusion are also precipitating factors according to Shen et al’s study.12 Preoperative discussion with patients and their family concerning the risks of eye injuries, particularly POVL, should not be omitted because some of the factors may not be modified at the present time.12
This study has several limitations. First, this was a retrospective study, so causality could not be determined.Second, the duration of the tested diseases and their treatments were not known. Third, the detailed medication and techniques of each anesthesia, operation and methods of eye protection for each patient were not recorded. Fourth, there may have been unknown or unmeasured but important confounders. For example, reduced tear production may be observed in patients with rheumatic arthritis,32 and preoperative dry eye and recurrent corneal erosion syndrome may increase the risk of perioperative corneal injury.33,34 Fifth, ambulatory patients were not included in the analysis, so a reporting system by ambulatory patients themselves should be set up for understanding the complications in this group of patients. Finally, the Trendelenburg position could not be identified because some patients might be shorter or longer placed in the Trendelenburg position pronely, laterally or supinely. The degrees and duration of head-up or head-down tilt were also not recorded.Because there was no documental information concerning the details of the Trendelenburg position, the associated risk with this position could not be evaluated.
In conclusion, eye injuries mostly occur in association with head and neck surgery. Being operated on in the lateral or prone position, anesthesia with intraoperative deliberate hypotension, and preoperative anemia are also precipitating factors. In future prospective studies, these factors should be included in the study design. The mechanism of ocular complications is not well understood; therefore, better strategies for eye protection may be hard to form, and injuries will still emerge. For patients and procedures with greater risks, obtaining preoperative information and intraoperative caution are both important.
Acknowledgments
The authors wish to thank all of the anesthesiologists and staff of nurse anesthetists of the Department of Anesthesiology, and the nursing staff of the postoperative recovery unit of Chang Gung Memorial Hospital, Taoyuan, Taiwan.