Clinical and surgical factors and intraoperative complications in patients who underwent penetrating keratoplasty

Objective to identify the main intraoperative complications of patients who underwent keratoplasty and relationship between these complications and clinical and surgical factors. Method cross-sectional observational study. A census of the patients submitted to keratoplasty was carried out, which totaled 258 procedures. Results twenty-two intraoperative complications were recorded, all in penetrating keratoplasty surgeries, of which 59.09% were performed in male patients with a mean age of 58.5 years. The main intraoperative complication was vitreous loss (36.36%). A statistically significant relationship was found between the variable “intraoperative complication” and the variables “previous surgery”, “combined keratoplasty and cataract extraction” and “corneal host button greater than 8.0 mm”. Conclusion identifying the main intraoperative complications of keratoplasty enables nurses to understand which factors may interfere with these procedures, point out possible predictors of complications, and seek control measures so that such complications do not occur.


Introduction
Corneal transplantation is primarily aimed at visual rehabilitation. The procedure itself can often cause refractive abnormality, such as high degrees of astigmatism, irregularity or anisometropia, which may hinder the restoration of satisfactory vision (1) .
With the evolution of corneal transplantation techniques, more lamellar surgeries have been performed around the world and the safety of transplantation has increased. In addition to other advantages, lamellar surgery has shown fewer complications, since the integrity of the patient's globe is preserved (2) .
Penetrating keratoplasty is considered a successful intraocular procedure, with a high success rate in lowrisk corneal diseases. It can be performed under general or local anesthesia. There are, however, intraoperative complications of keratoplasties that can seriously impair vision, cause rejection episodes and/or even graft failure (1)(2)(3) .
According to the American Academy of Ophthalmology, the main intraoperative complications in keratoplasty refer to graft centralization, irregular trepanation, damage to lens, damage to donor tissue, choroidal bleeding and effusion, and incarceration of the iris and vitreous tissue in the anterior chamber.
Although the literature shows the main intraoperative complications during a keratoplasty, there is no current data on the epidemiological profile of the subjects exposed to these complications. However, the monitoring and prophylaxis of complications during keratoplasty includes elements involved in the preoperative and intraoperative periods (4)(5) .
The nursing appointment is an important tool for the investigation and implementation of care that guarantees to the patient the ideal conditions for performing the transplantation and maintenance of the graft in the postoperative period. In the state of Rio Grande do Norte, the follow-up of these patients from the preoperative to the postoperative period is performed by the medical ophthalmologic team, while the nursing team acts during intraoperative care (6)(7) .
Nurses' performance must cover all surgical periods, from the indication to the transplantation to the patient's discharge. The nursing appointment enables identifying risk factors, comorbidities, therapeutic adherence, adequate use of medications, physical ophthalmologic examination, and control of modifiable risk factors and, consequently, improving graft quality and transparency for a longer time and avoiding possible complications (7) .

Method
This is a quantitative, epidemiological, observational, cross-sectional study carried out at a university hospital of Natal, Brazil, which is a public reference in the performance of keratoplasty. The main intraoperative complications were vitreous loss (36.36%), followed by expulsion of intraocular/crystalline lens (13.64%), vitreous hypertension (9.09%) and bleeding (9.09%). Table 1 presents the bivariate analysis of the variable "intraoperative complications" with the clinical and surgical characteristics of patients submitted to keratoplasty. Patients with a host button above 8.0 mm had 5.26 times more intraoperative complications than those with a host button less than or equal to 8.0 mm.
When keratoplasty was combined with cataract extraction, it had 7.09 times more complications when compared to keratoplasty performed alone. Table 2 presents the prevalence ratio of the variables "previous surgery", "host button size" and "combination with cataract extraction" versus the presence of "intraoperative complications".
New positive results were achieved with the adoption of the deep anterior lamellar keratoplasty (DALK). Because it is an extraocular procedure, it presents important safety and survival advantages of the corneal endothelium (9) .
However, penetrating keratoplasty is still performed by many surgeons and the prevention of the serious complications deriving from this procedure is of great interest to all who promote eye health (2) .
In this study, the main intraoperative complication of penetrating keratoplasty was the vitreous loss (36.36%).
Vitreous loss is an intraoperative complication that occurs in high-risk penetrating keratoplasty because this is a procedure in which the anterior chamber is exposed to open air (8) .
As a solution to this intraoperative complication, some studies propose innovative surgical techniques that promote intraoperative safety of the anterior chamber and consequently reduce the risk of vitreous complications (8) .
The graft-over-host technique aims to overcome positive vitreous pressure during penetrating keratoplasty as an alternative to minimize anterior chamber exposure.
The tecnique deals with a type of adapted penetrating keratoplasty, whose graft of the donor is initially superimposed on that of the host and only later this latter is removed (2) .
The inferential analysis of the variable "intraoperative once it does not expose the patient to two procedures at different times and presents a good ocular prognosis (12)(13) .
A study carried out in Saudi Arabia aimed to evaluate the results of surgeries of corneal grafts in which patients had undergone cataract surgery simultaneous to penetrating keratoplasty. As a result, the study presented evidence that the accomplishment of a combined procedure results in a faster visual rehabilitation and a graft with good clarity (12) .
In Japan, the Tohoku Graduate School of Medicine presented a surgical technique called Chandelier Illumination for performing keratoplasty surgery combined with cataract extraction. It is a technique in which the anterior chamber is not exposed, which minimizes intraoperative and postoperative complications. The rate of successful surgeries was significantly higher in the group that used the Chandelier technique than in the non-Chandelier group, with rates of 86% and 30%, respectively (13) .
Literature shows that the use of a corneal button 0.25-0.50 mm larger than the host's diameter should be recommended for preventing and reducing corneal excessive flattening in the postoperative period, and for reducing secondary glaucoma and improving conditions for wound closure (4,14) . However, the association of the defects, therapy with autologous serum dropper or amniotic membrane patches are valid options. Immune reactions should be diagnosed and treated immediately (5) .
The necessary care for the prevention and control of complications in keratoplasty includes attention and multiprofessional management. During the appointments, the nursing team should be attentive to the identification of risk factors for complications in keratoplasty, management of exposed patients, and prevention of modifiable risk factors.
Since it is a documentary research whose source of data collection originated from secondary data, like any study that uses this technique, it may have some limiting factors, such as loss of important information, inaccuracy of data, and the weaknesses of information systems records.
Another limiting factor of this study is the crosssectional design. Therefore, longitudinal studies could be performed in order to identify the relationship of the variables whose statistical analysis inferred association.

Conclusion
The present study verified that vitreous loss was the Therefore, preventive mechanisms should be used for these complications, such as the use of new surgical procedures that minimize such damages, as well as multidisciplinary care that guarantees continued care to the patient from the preoperative and intraoperative period until the postoperative period.