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1/9. Ocular explosion during cataract surgery: a clinical, histopathological, experimental, and biophysical study.

    INTRODUCTION: An increasing number of cases are being recognized in which a peribulbar anesthetic for cataract surgery has been inadvertently injected directly into the globe under high pressure until the globe ruptures or explodes. We reviewed the records of 6 such cases (one of which was reported previously by us), and one additional case has been reported in the literature. Surprisingly, 2 of these 7 cases went unrecognized at the time, and the surgeons proceeded with the cataract operation; all of the patients ultimately developed severe visual loss and/or loss of the eye. OBJECTIVES: To reproduce this eye explosion in a live anesthetized rabbit model and to perform a clinical, histopathological, experimental, biophysical, and mathematical analysis of this injury. methods: Eyes of live anesthetized rabbits were ruptured by means of the injection of saline directly into the globe under high pressure. The clinical and pathological findings of the ruptured human and animal eyes were documented photographically and/or histopathologically. An experimental, biophysical, and mathematical analysis of the pressures and forces required to rupture the globe via direct injection using human cadavers, human eye-bank eyes, and classic physics and ophthalmic formulas was performed. The laws of Bernoulli, LaPlace, Friedenwald, and Pascal were applied to the theoretical and experimental models of this phenomenon. RESULTS: The clinical and pathological findings of scleral rupture, retinal detachment, vitreous hemorrhage, and lens extrusion were observed. In the exploded human and rabbit eyes, the scleral ruptures appeared at the equator, the limbal area, or the posterior pole. In 2 of the 7 human eyes, the anterior segments appeared entirely normal despite the rupture, and cataract surgery was completed; surgery was canceled in the other 4 cases. In 4 of the 5 injected and ruptured rabbit eyes, the anterior segments appeared essentially normal. The experiments with human eye-bank eyes and the theoretical analyses of this entity show that the pressure required to produce such an injury is much more easily obtained with a 3- or 5-mL syringe than with a syringe 10 mL or larger. CONCLUSIONS: Explosion of an eyeball during the injection of anesthesia for ocular surgery is a devastating injury that may go unrecognized. The probability of an ocular explosion can be minimized by careful use of a syringe 10 mL or larger with a blunt needle, by discontinuing the injection if resistance is met, and by inspecting the globe prior to ocular massage or placement of a Honan balloon. When ocular explosion occurs, immediate referral to and intervention by a vitreoretinal surgeon is optimal. Practicing ophthalmologists should be aware of this blinding but preventable complication of ocular surgery.
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keywords = animal
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2/9. Intracarotid abciximab injection to abort impending ischemic stroke during carotid angioplasty.

    BACKGROUND: Abciximab, a platelet glycoprotein IIb/IIIa receptor antagonist, prevents ischemic complications during percutaneous transluminal coronary angioplasty and was recently shown to open occluded vessels in patients with acute myocardial infarction when used alone or in combination with other thrombolytic agents. In an animal model of arterial thrombosis, abciximab was found to be safe and effective for the prevention of carotid artery thrombosis. However, the safety and efficacy of abciximab in the treatment of acute ischemic cerebrovascular events is unknown at present. CASE DESCRIPTION: We describe 3 patients who experienced ischemic cerebrovascular events with symptoms involving the middle cerebral artery territory while undergoing percutaneous angioplasty and stenting to their internal carotid arteries. Abciximab was administered to each patient within 10 min of symptom onset as a bolus (0.25 mg/kg) into the ipsilateral common carotid artery followed by continuous intravenous infusion (9 microg/min) for 12 h. All patients' symptoms resolved completely (by 25 min, 40 min and 5 h, respectively) with no further neurological complications. CONCLUSIONS: Our preliminary observation suggests that abciximab may improve neurological outcome following middle cerebral artery ischemic events associated with carotid angioplasty and stenting. Large prospective studies are warranted to establish the safety and efficacy of abciximab in acute ischemic stroke, either as a primary treatment modality or an adjunct to carotid angioplasty and stenting.
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3/9. A new instrument for drainage or injection of fluid within subretinal space.

    PURPOSE: To describe a new instrument, the subretinal aspiration and injection device (SR-AID), designed to facilitate the controlled external drainage or injection of fluid in the subretinal space. methods: The SR-AID is formed by an assembly of a probe, handle body, and a driving unit. The curved conduit within the probe segment forms a curved tunnel and acts as a guide along which a needle moves back and forth. The feasibility of fluid injection beneath the attached retina was tested in animal eyes. The efficacy of subretinal fluid drainage with the SR-AID were assessed in six cases of clinical retinal detachment. RESULTS: External approach to the subretinal space under ophthalmoscopic monitoring can be achieved by oblique angle penetration of the scleral wall with a needle from the SR-AID. Fluid was injected successfully into the subretinal space in three of six rabbit eyes and in two of two pig eyes. The mean duration required for the drainage of subretinal fluid with the SR-AID was 127 seconds. There was no incidence of significant subretinal hemorrhage or retinal perforation in the animal experiments and in human cases. CONCLUSION: Our case series suggests that the SR-AID provides an efficient and safe means of access to the subretinal space.
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keywords = animal
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4/9. Leaflet arrest in St Jude Medical and CarboMedics valves: an experimental study.

    OBJECTIVE: Two patients who suffered acute failure of their St Jude Medical Masters aortic valve prostheses due to leaflet arrest that were unrelated to suture material are presented. It was hypothesized that the valves failed because force applied to bear upon the valve annulus caused the hinge mechanism to become restricted or to arrest. methods: A study was designed to measure the force that would cause leaflet arrest in three sizes of St Jude Medical Masters valves and CarboMedics mechanical valves. A specially manufactured pushrod device was used to apply a variable force to the sewing cuff, low annulus level, or to the pivot guards of all the valves. RESULTS: For every valve size tested, the St Jude Medical Masters valves required significantly less force applied than did the CarboMedics valves to cause one or both leaflets to arrest (P < 0.0004). CONCLUSIONS: A force applied on the valve ring of mechanical valves can cause leaflet arrest. The force required to arrest the leaflets is within an order of magnitude of that measured in other in vivo animal studies. We conclude that force on the valve rings in patients after aortic valve surgery could cause leaflet malfunction and even arrest in some patients.
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5/9. vestibular nerve injury as a complication of microvascular decompression.

    We report a case of hemifacial spasm in which hearing was well preserved after microvascular decompression, but the vestibular nerve was injured selectively. We review the pathophysiological mechanisms relevant to this complication in the light of results of animal experimental studies we have conducted. In addition, we discuss the clinical significance of this particular type of cranial nerve injury.
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keywords = animal
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6/9. pulmonary edema following air embolism.

    Venous air embolism is a major hazard during surgical procedures in the sitting position and is known to cause acute pulmonary edema in animal experiments (6, 7, 17). In man some cases of pulmonary edema immediately following air embolism have been described (10, 15, 16). In this case report we present a patient that developed pulmonary edema which became apparent several hours after the occurrence of air embolism.
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7/9. Heterotopic bone formation occurring near a ligated ureter.

    A case of heterotopic bone formation found in juxtaposition to an accidently ligated ureter is reported. This case may represent a human equivalent of induction of bone formation by urothelium, which was documented previously in experimental animals.
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8/9. Complete neurological recovery after 13 minutes of hypovolemic hypotension.

    It has been shown experimentally that irreversible brain injury and death may follow after 5-7 min of cerebral ischemia and that even brief periods, 2 min or less, can produce focal damage to the nervous system. All published studies demonstrating a protective effect of barbiturates have been performed in animals. A patient is presented who recovered full neurological function after 13 min of hypovolemic hypotension. This remarkable outcome may have been due to the rapid institution of high-dose barbiturate therapy. The extent to which such therapy affected his outcome is unclear, but does add to the growing body of evidence suggesting a favorable effect from this type of barbiturate therapy.
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keywords = animal
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9/9. Combined effects of compression and hypotension on nerve root function. A clinical case.

    Previous animal experiments suggest that mild compression may increase susceptibility of nerve roots to the effects of hypotension. The authors report the case of a patient with an unstable L2 burst fracture whose motor skills and senses were intact. During fracture reduction and spinal distraction, sensory-evoked potentials were recorded from the epidural space after right and left femoral and tibial nerve stimulation. Induced hypotension was used during the surgery. All responses were normal at the outset of the surgery. With hypotension, a marked drop in the amplitude of the right femoral evoked potential amplitude occurred; left femoral and both tibial responses remained unchanged. Evoked potential changes were reversible with reversal of hypotension. Postoperatively, the patient was neurologically intact. Further analysis revealed a significant correlation between the right femoral evoked potential amplitude and systolic blood pressure (r = 0.63, P < 0.005), whereas amplitudes of the other responses were not significantly correlated with systolic blood pressure. This report provides clinical evidence to support the hypothesis that hypotension and local compression exert additive adverse effects on nerve root function.
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