Peri-operative visual loss following total knee arthroplasty – A case report

Abstract

Perioperative visual loss (POVL) following non-ocular surgery is a rare but significant complication. This report describes a case of ischaemic optic neuropathy following total knee arthroplasty which resulted in permanent blindness.

1. Case report

A 68 year old gentleman with osteoarthritis of the left knee presented for total knee arthroplasty (TKA). He had a history of hypertension and non insulin dependent diabetes but no other significant cardiac or medical problems and no documented eye problems. His pre-operative blood pressure was 170/92 but ranged from 144/76 to 168/83 (despite medical treatment). TKA was performed under spinal anaesthetic. During the procedure a temporary drop in systolic blood pressure (<100 mmHg) was recorded, which responded to intravenous fluids. Immediate post-operative recovery was uneventful. Post-operatively his haemoglobin was 6.6 g/dl. Blood transfusion was considered at this point but due to the absence of cardiac symptoms was withheld. Four days post-operatively the patient complained of blurred vision in his right eye. However as he was mobilising well he was discharged home later this day. The patient's vision subsequently deteriorated and he presented to an Accident and Emergency department six days post-operatively. Ophthalmology assessment confirmed complete loss of vision in his right eye and 80 percent loss of left visual field, with macular sparing and visual acuity 6/7.5 in the left eye. Ischaemic optic neuropathy (ION) was diagnosed and attributed to intra-operative hypotension and post-operative anaemia. At this stage intravenous methylprednisolone and packed red cells were given but unfortunately the patient never regained vision in his right eye.

2. Discussion

POVL is a very rare but serious complication following non-ocular surgery. The incidence of POVL ranges from 0.002% of all surgeries and can be as high as 0.2% in spinal and cardiac surgery patients.¹ The principal causes of POVL after non-ocular surgery are retinal vascular occlusion and ischaemic optic neuropathy (ION). ION patients usually develop visual loss after a prolonged, major surgical procedure resulting in complete blindness that is usually permanent. The pathophysiology is multifactorial and involves an ischaemic process affecting the anterior or posterior circulation of the optic nerve.² There are numerous other possible causative factors in ION, including prone positioning, hypotension, haemodilution, blood loss, anaemia, altered venous haemodynamics as well as systemic vascular risk factors including hypertension, hyperlidiaemia, diabetes and smoking.³ In this case, blood loss, hypotension and anaemia following TKA may have precipitated haemodynamic changes which could have led to failure in the autoregulation of the blood flow in the optic nerve resulting in an ischaemic injury to the optic nerve and subsequent loss of vision.⁴

ION has been reported following hip arthroplasty⁵ and hip resurfacing⁶ procedures. There has been a single reported case of ION following bilateral simultaneous TKA⁵ but to the authors knowledge this is the first case of ION reported in a patient following unilateral TKA.

There are currently no effective treatments for ION.⁴ Prevention through careful intra-operative and post-operative assessment and management of anaemia, fluid balance and blood pressure are essential in association with raised awareness of this condition. Systemic steroids have been used in treating some forms of ION but Hayreh has shown that no improvement was obtained in the surgical posterior ION group.

Blood transfusion of packed red cells (PRC) following TKA carries a heightened risk of deep infection in addition to the other transfusion related problems, which are associated with significant morbidity and mortality.⁷ Protocol in our unit indicates that PRC transfusion is considered if haemoglobin values drop below 8 g/dl in a fit patient, but transfusion is avoided in the absence of clinical symptoms and/or significant cardiac history. This protocol is designed to reduce the risk of post-operative infection following total joint replacement. Therefore although the patient's haemoglobin dropped to 6.6 g/dl, the absence of cardiac symptoms and his good mobilisation meant no transfusion was given. Neither nursing nor medical staff had any awareness of the possibility of ION and therefore the significance of the patient's complaint of blurred vision was not appreciated.

Although there is no conclusive evidence that transfusion would have altered the clinical course in this case we feel that the important lesson is to consider urgent blood transfusion as well as prompt ophthalmology review in a patient who complains of blurred vision following total joint replacement.

Conflicts of interest

All authors have none to declare.