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* From the Division of Respirology, Department of Medicine, University of Toronto; the
Department of Anesthesia, St. Michael’s Hospital; the
Forensic Pathology Unit, Office of the Chief Coroner for Ontario and Department of Laboratory Medicine and Pathobiology, University of Toronto; and the
Department of Anesthesia, St. Michael’s Hospital and University of Toronto, Toronto, Ontario, Canada.
Address correspondence to: Dr. Kieran McIntyre, 1642 Bathurst St. Toronto, Ontario M5P3J7, Canada. Fax: 519-756-1101; E-mail: kieran.mcintyre{at}utoronto.ca
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Abstract |
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Clinical features: A 34-yr-old man with myotonic dystrophy underwent uneventful tendon contracture release under regional anesthesia. In the immediate postoperative period, neurological and respiratory complications developed, requiring intensive care support. The patient showed the classical clinical triad of hypoxemia, neurological impairment and a petechial rash associated with the FES. A diagnosis of FES was made and, despite therapy including fluid and inotropic support, the patient succumbed to the condition. There was no demonstrated intracardiac shunt, suggesting a physiological intrapulmonary shunt was responsible for the development of systemic manifestations of FES.
Conclusions: Postoperative neurological dysfunction is a difficult condition with numerous possible causes. All possible etiologies, including FES, need to be considered in the differential diagnosis and postoperative management of patients developing acute postoperative neurological impairment and hypoxemia.
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Case report |
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In consultation with an orthopedic surgeon, the patient chose to proceed with surgery. His only medication at the time of admission was acetaminophen prn for joint and muscle pain. The patient’s preoperative laboratory investigations revealed: hemoglobin (Hgb) = 139g·L–1, platelet count = 309 x109·L–1, leukocyte count (WBC) = 10.0 x109·L–1, international normalized ratio (INR) = 1.2, activated partial thromboplastin time = 29.6 sec, and creatinine = 63 umol·L–1.
Given the patient’s significant contractures and possible difficult airway, a spinal anesthetic was planned for the short procedure. In the operating room, and under routine monitoring, midazolam 1 mg iv was given for anxiolysis, and a 25G Whitacre needle was used to administer 7.5 mg hyperbaric bupivacaine with 20 µg of fentanyl intrathecally at the L3-4 interspace. The patient underwent dissection and release of adductor tendon contractures bilaterally. The patient’s vital signs were stable throughout the 30 min operation, and he was interacting appropriately with the operating room personnel. On completion of surgery, the patient was transferred to the postanesthesia care unit (PACU) for monitoring, with both legs casted in their new positions.
It was noted in the PACU that the patient was not responding to stimulation and so flumazenil 0.5 mg iv and naloxone 0.4 mg iv were given, with no improvement in his neurological status. The patient’s heart rate fluctuated between 100 and 140 beats·min–1 and his systolic blood pressure between 110 and 130 mmHg, though his hemodynamic status improved immediately after the administration of intravenous normal saline. Six hours postoperatively, he remained unresponsive and had developed hypoxia requiring increasing amounts of oxygen by face-mask to maintain his Hgb saturation above 95%. At this point, an analysis of the patient’s arterial blood gas revealed a pH of 7.36, pCO2 34 mmHg, pO2 85 mmHg, base excess -5.6, with saturation 97% on 50% inspired oxygen. The remainder of his laboratory investigations revealed the following: Hgb 137 g·L–1, WBC 24.71 x 109·L–1, platelets 78 x 109·L–1; lactate 5.5mmol·L–1, creatinine 120 umol·L–1 and troponin-T of 11.05 µg·L–1. His INR had increased to 1.40. The patient’s electrocardiogram demonstrated a preexisting elevated R wave in lead V1 and sinus tachycardia at 140 beats·min–1. The neurological examination elicited response only to painful stimulation; the pupils were equal and reacted appropriately to light. Examination of the upper limbs revealed hyperreflexia but no spasticity or rigidity. There were bilateral extensor plantar responses but further assessment of the lower limbs was restricted by the plaster casts.
Given the patient’s deterioration, he was transferred to the intensive care unit where his trachea was intubated, guided by fibreoptic bronchoscopy, and a central venous line was inserted. A chest x-ray revealed diffuse bilateral airspace disease (Figure 1
). Non-contrast computed tomography of the head approximately ten hours postoperatively revealed areas of bilateral symmetrical low density with diffuse lucency of the cerebral cortex and loss of density involving both thalami (Figures 2a and 2b). Upon his return from the radiology department, a new petechial rash was noted across his face, anterior chest and axillae bilaterally. The possible diagnosis of fat embolism syndrome was entertained. Portable x-rays of his legs confirmed the presence of a displaced subcapital fracture of the right femur and a non-displaced intertrochanteric fracture of the left femur (Figure 3). Over the following 12 hr, the patient remained hypoxic and became progressively hypotensive and tachycardic, unresponsive to fluid and combined dobutamine and norepinephrine infusions. His blood work had significant abnormalities consistent with disseminated intravascular coagulation; his hemoglobin had decreased to 100 g·L–1, his platelet count was 43 x 109·L–1, the INR was 2.05 with an elevated D-dimer of > 5000 ng·mL–1 and red blood cell fragments were seen on a film of his peripheral blood. Multi-organ system failure developed and he experienced three cardiopulmonary arrests. Despite resuscitative efforts, the patient died within 24 hr of his initial surgery.
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), brain (Figure 4b) and kidneys (Figure 4c). Microscopic examination of the patient’s skeletal muscles revealed atrophy and extensive fatty replacement.
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The patient in this case may have been at higher risk for FES given the microscopically documented replacement of skeletal muscle with fat, in combination with surgical manipulation of his lower limbs. Schwartz-Jampel or myotonic chondrodystrophy is a progressive condition which demonstrates autosomal recessive inheritance.12,13 Affected individuals have radiological evidence of osteochondrodysplasia, often resulting in reduced stature, kyphoscoliosis, bowing of the diaphyses, and irregular epiphyses.13 Patients are often diagnosed early in childhood after failing to meet age-appropriate motor milestones, and as adults demonstrate muscle stiffness particularly in the legs.
There was a gradual deterioration over several hours postoperatively, a finding consistent with other reports. This timeline suggests that the neurological impairment was due not to the embolic load in the cerebral circulation, but rather, to the gradual development of cerebral edema after embolization, or the release of free-fatty acids and glycerin from the fat cells and resulting toxic effect on the brain cells.14 Neurological symptoms associated with FES have also sbeen described as late as three hours after orthopedic surgery, suggesting such patients should have frequent monitoring including periodic assessment of level of consciousness, so that deterioration in mental function can be detected early and supportive care instituted. 14 It is possible that the pulmonary circulation is able to accommodate a threshold embolic load until increased pulmonary pressures overcome the changes via recruitment of vascular beds, thus providing a mechanism for a dynamic transpulmonic shunt. The patient’s hemodynamic collapse was most likely due to right ventricular failure from acute pulmonary hypertension. Of interest, in an animal model of LME, cerebral circulation of the microemboli occurred only in the animals that received fluid and epinephrine resuscitation. 10 The authors suggest that resuscitation may enhance transpulmonary lipid passage either through increased pulmonary blood flow, pulmonary vascular recruitment, or a direct epinephrine effect. Perhaps the mechanism required for transpulmonary shunting is an acute increase in pulmonary arterial pressure, and not necessarily the means by which it is achieved.
The treatment of FES has been limited to supportive measures, since the responsible mechanisms are already established by the time a diagnosis is suspected. The emphasis remains on prevention with modified surgical techniques, corticosteroid therapy in high risk patients, and intravascular volume replacement in all patients.15–17
This case report demonstrates the importance of including FES in the differential diagnosis of acute postoperative neurological dysfunction. Unfortunately, even if FES is recognized in a monitored setting as we have described, there are limited means of prevention or effective treatment. Therapy for FES remains supportive, and the outcome depends on the patient’s age and underlying condition.
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Footnotes |
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Accepted for publication October 26, 2006. Revision accepted January 6, 2007.
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