Hypotension and anaemia--a blinding combination.
We present a case of complete blindness following severe dengue haemorrhagic fever complicated by anaemia and a dialysis-related episode of profound hypotension. The clinical and radiological features indicated an optic neuropathy, most likely ischaemic in aetiology The features of posterior ischaemic optic neuropathy and differential diagnosis are discussed
Key Words: posterior ischaemic optic neuropathy, dengue fever
Posterior ischaemic optic neuropathy (PION) is a relatively rare but often devastating complication of hypotensive episodes during surgery, critical illness or dialysis. Associated anaemia, blood loss and cardiovascular risk factors are contributory to the condition. A case is presented in which permanent, total blindness followed such a hypotensive episode during a time of severe anaemia. Consent for publication was obtained.
A 63-year-old woman was transferred to our hospital by air ambulance with an acute, severe illness and multiple organ failure. Seventeen days previously she had developed fever, malaise, myalgia and headache following a mosquito bite in a dengue-endemic area. Her symptoms had worsened over the subsequent week and she was admitted to a local medical centre with confusion, vomiting and transient left-sided weakness. A CT brain scan was reported as normal and dengue serology was IgM positive. Several days later she deteriorated, developing acute renal failure (creatinine 500 mg/l), acidosis, thrombocytopenia (18 x [10.sup.9]/l) and anaemia (5.9 g/dl). She had widespread petechial haemorrhages consistent with dengue haemorrhagic fever. High dose corticosteroids were commenced with the aim of improving the thrombocytopenia. Intermittent haemodialysis was commenced at the local medical centre during which she developed severe hypotension and respiratory problems necessitating emergency intubation, ventilation and vasopressor support.
On arrival at our hospital she was intubated and sedated, and haemodynamically stable with mean arterial pressure of 75 mmHg. She was noted at the time to have unreactive mid-dilated pupils and optic nerve-head swelling. A CT brain scan showed a right frontal intracerebral haemorrhage with some associated mass effect, but no midline shift and a small left occipital subdural haemorrhage (Figure 1). Over the subsequent two weeks her general condition slowly improved. She remained on prednisolone 60 mg daily, but on regaining consciousness she complained of complete loss of vision. Examination revealed that she was unable to perceive even the brightest light in either eye and the pupils were mid-dilated and unreactive. Ocular movements were full and there was no sign of orbital pathology. Intraocular pressures were 12 mmHg in either eye and there was no intraocular inflammation. There was mild, haemorrhagic swelling of both optic nerve heads and occasional peripheral retinal haemorrhages but no maculopathy. T2 weighted MRI scanning showed localised intrinsic high signal in both optic nerves posteriorly and partial resolution of frontal and subdural haemorrhages (Figure 2). There was no evidence of watershed ischaemia in the remainder of the central nervous system on imaging. The systemic corticosteroids were tailed off and after three months of follow-up she has remained completely blind.
[FIGURE 1 OMITTED]
[FIGURE 2 OMITTED]
This patient developed irreversible blindness in both eyes following a period of profound hypotension during a haemodialysis session at a time of severe anaemia (Hb 5.9g/dl). The unreactive pupils localise the pathology to the anterior visual pathway, which was confirmed by the finding of high signal in the posterior optic nerves on MRI. The patient had severe dengue haemorrhagic fever and while dengue optic neuropathy remains an unlikely possibility, the authors believe that the case described has features most consistent with PION.
PION is a rare condition in which there is infarction of the posterior portion of the optic nerve either following a hypotensive episode occurring intraoperatively or during a critical illness, when it is usually bilateral, or occurring spontaneously in the presence of atheromatous vascular disease or giant cell arteritis, when it typically affects just one eye. The exact reasons for the posterior optic nerve's susceptibility to watershed infarction in certain individuals are unclear, but typically the remainder of the central nervous system is spared (1). Anatomical studies have shown that there is significant variation in the vascular supply of the optic nerve (2), and while the anterior portion receives blood centripetally from the pial supply and centrifugally from the central retinal artery, in the majority of individuals the posterior portion relies solely upon the pial vasculature. Optic nerve head swelling and haemorrhages are not a feature of PION and in this case these features could have been caused by raised intracranial pressure (due to the intracranial haemorrhage), the bleeding tendency associated with dengue infection and/or concomitant anterior ischaemic optic neuropathy (AION).
Perioperative PION is most commonly seen after spinal surgery (0.1% risk) and radical neck dissection (0.08% risk) when raised orbital pressure (due to prone positioning and jugular vein ligation respectively) is thought to exacerbate the effects of blood loss and hypotension (3). The mean intraoperative blood loss in perioperative PION is 3.7 litres. Haemodialysis is also a recognised precipitant of both PION and AIONQ (4-7) with all reports citing anaemia (reduced oxygen carrying capacity) and hypotension as co-existing factors. Ischaemic optic neuropathy complicating perioperative or dialysis-related hypotensive episodes is usually bilateral (61%), with no proven effective therapy. The prognosis is poor: 55% are left with a final visual acuity of hand movements (*) or worse (3).
Dengue fever, an acute flaviviral illness transmitted by the Aeries mosquito, is prevalent in Africa, South-east Asia and both Central and South America and the Caribbean. The great majority of the estimated 100 million infections annually worldwide are either asymptomatic or cause a mild 'undifferentiated' fever but the more severe forms of the disease, dengue haemorrhagic fever and dengue shock syndrome have significant morbidity and mortality. Ophthalmic complications are rare in dengue, with a transient exudative or haemorrhagic maculopathy, arising approximately one week after the onset of symptoms, being the most commonly described finding (8,9). Case reports have been published of dengue-associated optic neuritis and neuromyelitis optica (10,11) presenting 10 and 14 days after the onset of the illness respectively. In both cases there was bilateral optic nerve involvement with MRI-confirmed lesions but in contrast to our case, there was a good response to treatment with systemic corticosteroids with an excellent final visual acuity both individuals.
This case illustrates a rare but devastating complication of an intermittent dialysis-associated hypotensive episode in the presence of severe anaemia. While adverse clinical events are inevitable in patients requiring critical care, transfusion to improve the anaemia or the use of a continuous renal replacement technique may have prevented this unfortunate outcome.
* 'Hand movements' indicates a level of vision so poor that the eye in question is, at best, able to see the shadow of a hand moving directly in front of that individual's face
Accepted for publication on April 27, 2007.
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E.H. HUGHES *, E.M. GRAHAM ([dagger]), D. L. A. WYNCOLL ([double dagger]) Adult Intensive Care Unit, St. Thomas' Hospital, London, United Kingdom
* M.B., B.S., M.D., M.R.C.P., M.R.C.Ophth., Fellow, Ophthalmology Department.
([dagger]) M.B., B.S., F.R.C.P., F.R.C.Ophth., Consultant, Medical Eye Unit.
([double dagger]) M.B., B.S., F.R.C.A., D.I.C.M., Consultant.
Address for reprints: Mr E.H. Hughes, Medical Eye Unit, St. Thomas' Hospital, Lambeth Palace Road, London SE 17EH, U.K.
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|Author:||Hughes, E.H.; Graham, E.M.; Wyncoll, D.L.A.|
|Publication:||Anaesthesia and Intensive Care|
|Article Type:||Clinical report|
|Date:||Oct 1, 2007|
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