Continuous Intraocular Pressure Patterns in Spine Surgery
试验速览
- 阶段
- 不适用
- 状态
- 已完成
- 入组人数
- 10
- 试验地点
- 1
- 主要终点
- Report the physiological changes of IOP patterns during prone spinal surgery
研究概览
简要总结
Post-operative visual loss is a rare but serious complication after surgery. It is most significantly correlated with prone spinal surgery with a prolonged duration. The cause and risk factors are not elucidated, but the majority of the cases are due posterior ischaemic optic neuropathy (PION). This entity is directly related to the ocular perfusion pressure (OPP), which is estimated as the difference between mean arterial blood pressure (MAP) and intraocular pressure (IOP). Autoregulation is believed to maintain a constant perfusion to the optic nerve despite fluctuations in the perfusion pressure.
IOP is known to increase in the prone position thus putting susceptible patients at risk for inadequate ocular nerve perfusion. Most of the evidence comes from animal and healthy volunteer studies and cannot give an accurate insight into the subtle changes of intra-operative IOP. All the published studies employed the use of a tonometer, which may have rooms for measurement errors due to inadvertent pressure on the globe while retracting the eyelids, particularly when there is significant periorbital/conjunctival swelling in the prone position. The majority of the studies recruited healthy volunteers in a simulated surgical setting so other fluctuating parameters, which can affect intraoperative IOP, cannot be measured. In the few reports where patients undergoing surgery in the prone position were studies, IOP measurements were taken at non-continuous monitoring at time intervals, thus the effects of changes in blood volume, MAP, central venous pressure (CVP) and PaCO 2 could not be studied. Lastly, all the literature consists of case series only with no control group so the effect of position cannot be evaluated independently of the other factors.
The investigators therefore propose to conduct a prospective study with continuous intraoperative IOP monitoring to give us further insight into the physiological changes of IOP in patients undergoing spine surgery, and identify the risk factors related to fluctuations of IOP during prone spinal surgery.
详细描述
Post-operative visual loss (POVL) is a rare but serious complication after surgery.
One of the known associations is prone spinal surgery with a prolonged duration.
The cause is not completely understood, but some of the risk factors for developing POVL include anaemia, hypotension, the duration of surgery and patient factors such as age, hypertension and atherosclerosis. There are also some unidentifiablerisk factors that may predispose young healthy patients to POVL. Once the patient develops POVL, it is usually irreversible, and the patient is left with a permanent disability.
The majority of POVL cases that occur with prone spinal surgery are due to posterior ischaemic optic neuropathy (PION). PION is directly related to the ocular perfusion pressure (OPP), which is estimated as the difference between mean arterial blood pressure (MAP) and intraocular pressure (IOP). Autoregulation is believed to maintain a constant perfusion to the optic nerve despite fluctuations in the perfusion pressure.
However, there is a knowledge gap in the physiological changes of IOP during prone surgery. IOP is a highly dynamic parameter, and the most widely used method to measure it is using a handheld tonometer. The main limitation of this technique is the isolated nature of its measurements, as it can only be taken at regular intervals, and may not reflect the full range of IOP changes. Studies on IOP during prone position in the current literature have all used this technique. 1-5 Hence subtle changes of IOP can be undetected, as interval measurements cannot reflect short-term variations that occur within seconds or minutes. Furthermore, most of the studies are performed on animals or healthy volunteers 5,6 , which further limit the interpretation of their results. For the few studies performed on anaesthetised patients undergoing spinal surgeries, the duration of surgery is short or mixed, so the critical time point may not have been studied. The American Society of Anesthesiologists Postoperative Visual Loss Registry suggests that an anaesthetic duration of greater than 6 hours is more correlated with POVL.
研究设计
- 研究类型
- Interventional
- 分配方式
- Na
- 干预模型
- Single Group
- 主要目的
- Diagnostic
- 盲法
- None
入排标准
- 年龄范围
- 18 Years 至 80 Years（Adult, Older Adult）
- 性别
- All
- 接受健康志愿者
- 否
入选标准
- •Signed informed consent
- •Age 18 to 80 years inclusive
- •No pre-existing eye pathology (excluding refractive error), patients with glaucoma, history of eye injury or ophthalmic surgery
- •No known allergy to contact lens material
- •Patients undergoing anterior cervical spine surgery and prone spine surgery for duration of 3 hours or longer
排除标准
- •Unable to comply with follow up or give informed consent
- •Cannot tolerate wearing contact lens
- •Has active eye infection
结局指标
主要结局
Report the physiological changes of IOP patterns during prone spinal surgery
时间窗: 1 year
The outcome measure will be to report the physiological changes of IOP patterns during prone spinal surgery.
次要结局
- Correlate any intraoperative risk factors that may cause IOP fluctuations(1 year)
- Documentation of IOP changes after the surgery until the contact lens sensor is removed(1 year)
研究者
Dr. Kenny Kwan
Clinical Assistant Professor
The University of Hong Kong