Charles A. Owen's research while affiliated with University of California, San Diego and other places

The two basic research tools developed to measure tissue fluid pressure (wick catheter) and osmotic pressure (colloid osmometer) have undergone extensive validation and refinement over the past 20 years. Using these techniques, basic science investigations were undertaken of edema in Amazon reptiles, pressure-volume relations in animals and plants, adaptive physiology of Antarctic penguins and fishes, edema in spawning salmon, tissue fluid balance in humans under normal conditions and during simulated weightlessness, and orthostatic adaptation in a mammal with high and variable blood pressures--the giraffe. Following and sometimes paralleling this basic research have been several clinical applications related to use of our colloid osmometer and wick technique. Applications of the osmometer have included insights into (a) reduced osmotic pressure of sickle-cell hemoglobin with deoxygenation and (b) reduced swelling pressure of human nucleus pulposus with hydration or certain enzymes. Clinical uses of the wick technique have included (a) improvement of diagnosis and treatment of acute and chronic compartment syndromes, (b) elucidation of tissue pressure thresholds for neuromuscular dysfunction, and (c) development of a better tourniquet design for orthopaedics. This article demonstrates that basic research tools open up areas of basic, applied, and clinical research.

To study muscle necrosis due to prolonged limb compression, we measured intramuscular pressure by inserting wick catheters into 10 volar forearms and 10 anterior tibial compartments of adult volunteers. We then placed the subjects in positions in which victims of drug overdose are commonly found. Intramuscular pressures in the area of direct compression on hard surfaces ranged from 26 to 240 mm Hg, and averaged 101 mm Hg. Most remarkable was a mean pressure of 180 mm Hg on compression of the forearm by the rib cage. These pressures are sufficient to cause muscle and capillary ischemia and necrosis by local obstruction of the circulation. This local injury by limb compression may produce edema sufficient to start compartment tamponade and consequent muscle-compartment and crush syndromes.

Intracompartmental pressures were measured by the wick catheter technique in sixty-five compartments of twenty-seven patients who were clinically suspected of having acute compartment syndromes. A pressure of thirty millimeters of mercury or more was used as an indication for decompressive fasciotomy. The range of normal pressure was from zero to eight millimeters of mercury. Eleven of these patients were diagnosed as actually having compartment syndromes and in these patients, twenty-seven compartments were decompressed. Only two patients had significant sequelae. In the sixteen patients (thirty-eight compartments) whose pressures remained less than thirty millimeters of mercury, fasciotomy was withheld and compartment syndrome sequelae did not develop in any patient. Intraoperatively the wick catheter was used continuously in eight patients to document the effectiveness of decompression. Fasciotomy consistently restored pressures to normal except in the buttock and deltoid compartments, where epimysiotomy was required to supplement the fasciotomy. Continuous intraoperative monitoring of pressure by the wick catheter technique allowed us to select the few cases in which primary closure of wounds was appropriate and to decide which patients were best treated with secondary closure.

This case report of an acute exertional compartment syndrome involving predominantly the superficial posterior compartment emphasizes several important facts: (1) The subacute recurring syndromes, if left untreated, may develop into an acute syndrome. (2) The diagnostic findings separating the acute syndrome from the chronic forms are marked pain with passive stretch of the involved muscles, paresis, and sensory deficit.8,12,15, (3) In the acute form, immediate fasciotomy is mandatory and often results in full recovery. (4) All four major compartments of the leg are susceptible to chronic or acute compartment syndromes initiated by exertion. These compartments can be decompressed as necessary through a limited skin incision as recently reported.11 (5) The need for an easily obtainable and reproducible method for measuring intracompartment pressures (e.g., the wick catheter technique) is indicated.

Fluid homeostasis within muscle compartments is maintained by four pressures: capillary blood pressure, capillary blood oncotic pressure, tissue-fluid pressure, and tissue fluid oncotic pressure. As determined in the canine anterolateral compartment, capillary blood pressure is 25 +/- 3 millimeters of mercury; capillary blood oncotic pressure, 26 +/- 3 millimeters of mercury, tissue-pbessure, -2 +/- 2 millimeters of mercury; and tissue-fluid oncotic pressure, 11 +/- 1 millimeters of mercury. The wick technique allows direct measurement of tissue-fluid pressure in skeletal muscle and, with minor modifications, is adapted to collect microsamples of interstitial fluid for determinations of tissue-fluid oncotic pressure. The wick technique detects very slight fluctuations in intracompartmental pressure such as light finger compression, injection of small volumes of fluid, and even pulsation due to adjacent arterial pressure. Adjacent muscle compartments may contain different tissue-fluid pressure due to impermeable osseofascial barriers. Our results obtained in canine muscle compartments pressurized by infusion of autologous plasma suggest that risks of muscle damage are significant at intracompartmental pressures greater than thirty millimeters of mercury.

Contusion or prolonged compression of the buttock produced severe local injury in 3 cases. Rhabdomyolysis with acute renal failure occurred in 2 of these cases, and one of them had an associated sciatic nerve palsy. The affected muscles included the gluteus maximus, gluteus medius, and the tensor fascia latae. Clinically and experimentally, these muscles were shown to be functionally enclosed within separate compartments like the peripheral limb muscles. Prompt decompression in the two cases with pressures exceeding 30 mm Hg resulted in muscle and nerve recovery.

The wick technique for measuring muscle-compartment pressure is an accurate measurement for early diagnosis of compartment syndromes in man. The technique is highly reproducible and offers numerous advantages including rapid and long-term equilibrium recordings of fluid pressure. Normal human intracompartmental pressures of −3 to +5 mm Hg rise to between 60 and 95 mm Hg during isometric contraction, suggesting muscle ischemia during contractile episodes. As determined by the wick technique, patients with compartmental pressures over 30 mm Hg are at substantial risk of incurring a syndrome. Fasciotomy immediately relieves the high intracompartmental pressure.

Chronic compartment syndromes of the leg are characterized by recurrent symptoms of exertionally precipitated pain and paresthesia, and are frequently associated with muscle hernias over the anterolateral compartments. In case report of a 19-yr-old woman this symptom complex was associated with entrapment of the superficial peroneal nerve.

Surgical decompression remains the only effective treatment for the ischemia of the muscles and nerves of the leg that constitutes the principal defects in the compartment syndromes. Recently, partial fibulectomy has been proposed as a good way to decompress all four compartments instead of the older double incision. Both methods are effective in satisfactorily reducing intracompartmental pressures, as documented by our wick catheter measurements. However, the double-incision technique is easier, faster, safer, and is the treatment of choice when four-compartment decompressive fasciotomy is indicated.