Forearm Compartment Syndrome from Intravenous Mannitol Extravasation During General Anesthesia

Abstract

Compartment syndrome from extravasation of mannitol is rarely reported (1). The pathophysiology and potential therapeutic options for mannitol extravasation are not well known. We describe a case of upper-extremity compartment syndrome resulting from mannitol extravasation in a patient under general anesthesia. Case Report A 49-yr-old woman, ASA physical status IV, weighing 80 kg, with a severe headache from a posterior communicating aneurysm rupture was scheduled for aneurysm clipping. Her neurologic examination was normal. In the operating room, the usual monitors were placed, anesthesia was induced with thiopental 400 mg, lidocaine 100 mg, fentanyl 250 μg, and rocuronium 50 mg via a preexisting right antecubital 18-gauge IV catheter. The trachea was intubated, and ventilation was controlled. General anesthesia was maintained with isoflurane and remifentanil 0.125 μg · kg−1 · min−1 via a 20-gauge IV catheter in the left hand. A 20-gauge right radial arterial cannula was inserted. The right arm was laterally tucked and pressure points were padded. Sixty minutes after scalp incision, mannitol was given through the right antecubital IV at approximately 5 g/min. The surgeon noted that the brain bulk had decreased. Forty-five minutes after the initial administration of mannitol, the arterial pulse-pressure waveform and the ipsilateral pulse oximeter tracing dampened. After undraping, the forearm was discovered to be tensely swollen and cyanotic, with delayed capillary refill. There was a free flow of blood from the arterial cannula and a pulse was palpable. A hand surgeon performed a fasciotomy extending from the wrist to the forearm, after clipping of the aneurysm. The patient awoke in the operating room and was tracheally extubated. In the postanesthesia recovery unit, physical examination revealed weakness in the left lower extremity, palpable radial arterial pulses, normal capillary filling, and a normal upper-extremity neurologic examination. In the intensive care unit, forearm edema gradually decreased, over several days. She was discharged with full function of her right arm, and a well healed fasciotomy scar. Discussion Complications of IV mannitol administration range from phlebitis to extensive tissue necrosis, leading to a loss of function (1). Compartment syndromes related to anesthesia have been reported to occur with diazepam extravasation (2), pressurized IV fluids (3,4), hypertonic saline (5), packed red cells (6), radial artery cannulation (7), positioning (8), intraarterial barbiturates (9), and manual blood pressure cuffs (10). Compartment syndrome resulting from mannitol extravasation can be severe and warrant immediate surgical fasciotomy (1). Stahl and Lerner (1) proposed that the high osmolarity of mannitol (1098 mOsm/L) may cause a compartment syndrome, secondary to fluid moving out of the vasculature and cells, resulting in increased compartment pressures and eventually cell death. It is possible that mannitol extravasated from this patient’s antecubital vein, as a result of previous needle-stick trauma or during cannulation of the vein. Diagnosis of compartment syndrome is difficult in the unconscious patient (1). Increased pressure, with a palpably tense compartment, is pathognomonic of compartment syndrome (2). Compartment syndrome is considered significant if there is neurologic dysfunction and the compartmental pressures are more than 30 mm Hg (1). Peripheral arterial pulses may not be absent if arterial pressure is greater than the critical closing pressure of veins and arteries supplying that extremity (1). Elevation of the affected limb can reduce arterial pressure sufficiently to arrest circulation (8); therefore, limb elevation may be contraindicated. Frequent examination of the extremities is crucial in making a timely diagnosis and minimizing risk of permanent injury. This is critical in obtunded or anesthetized patients (11). Emergent fasciotomy is the recommended treatment for severe compartment syndrome. Early recognition, diagnosis, and surgical intervention averted potential neural and functional impairment in our patient. This is the first report of compartment syndrome after mannitol administration, in a patient under general anesthesia. Mannitol is infused frequently during neurosurgical and other operations. Although extravasation injury attributed to mannitol seldom is described, anesthesiologists may encounter this problem and should recognize potential complications. Awareness may decrease the likelihood of extravasation injury. We recommend infusing mannitol in an observed IV site, if possible, or alternatively, via a central venous catheter. Tucking of the extremities should be avoided, if possible. Systematic monitoring of an observed extremity will permit discontinuation of the infusion at the first sign of extravasation (12). Monitoring of the upper extremities with intraarterial pressure wave and pulse oximetry may lead to earlier detection of increased compartmental pressures. We are grateful to John B. Downs, MD, for his advice on manuscript preparation and Mr. Peter Shea for his editorial assistance.