AN INDIRECT METHOD FOR ESTIMATING TISSUE PRESSURE WITH SPECIAL REFERENCE TO TISSUE PRESSURE IN MUSCLE DURING EXERCISE

[Acute extremity compartment syndrome: current concepts in diagnostics and therapy]

Acute compartment syndrome of the upper and lower limbs is observed following trauma, reperfusion or as an intraoperative complication caused by positioning. The pathophysiology of the disorder has been extensively described and is well known as a loss of perfusion due to rising compartmental pressures. It is a serious and potentially limb- and life-threatening complication. Early diagnosis is made primarily based on clinical findings. Early and focused therapy is crucial to prevent the devastating complications of this acute condition. However, diagnosis can be difficult, particularly in unconscious patients. Thus, in uncertain cases, pressure measurements are essential. Dermato-fasciotomy is the routine method to decompress the compartmental space. This review article examines the clinical findings, diagnostic techniques, and management options for the patient with musculoskeletal injuries.

The functional coupling of the deep abdominal and paraspinal muscles: the effects of simulated paraspinal muscle contraction on force transfer to the middle and posterior layer of the thoracolumbar fascia

The thoracolumbar fascia (TLF) consists of aponeurotic and fascial layers that interweave the paraspinal and abdominal muscles into a complex matrix stabilizing the lumbosacral spine. To better understand low back pain, it is essential to appreciate how these muscles cooperate to influence lumbopelvic stability. This study tested the following hypotheses: (i) pressure within the TLF's paraspinal muscular compartment (PMC) alters load transfer between the TLF's posterior and middle layers (PLF and MLF); and (ii) with increased tension of the common tendon of the transversus abdominis (CTrA) and internal oblique muscles and incremental PMC pressure, fascial tension is primarily transferred to the PLF. In cadaveric axial sections, paraspinal muscles were replaced with inflatable tubes to simulate paraspinal muscle contraction. At each inflation increment, tension was created in the CTrA to simulate contraction of the deep abdominal muscles. Fluoroscopic images and load cells captured changes in the size, shape and tension of the PMC due to inflation, with and without tension to the CTrA. In the absence of PMC pressure, increasing tension on the CTrA resulted in anterior and lateral movement of the PMC. PMC inflation in the absence of tension to the CTrA resulted in a small increase in the PMC perimeter and a larger posterior displacement. Combining PMC inflation and tension to the CTrA resulted in an incremental increase in PLF tension without significantly altering tension in the MLF. Paraspinal muscle contraction leads to posterior displacement of the PLF. When expansion is combined with abdominal muscle contraction, the CTrA and internal oblique transfers tension almost exclusively to the PLF, thereby girdling the paraspinal muscles. The lateral border of the PMC is restrained from displacement to maintain integrity. Posterior movement of the PMC represents an increase of the PLF extension moment arm. Dysfunctional paraspinal muscles would reduce the posterior displacement of the PLF and increase the compliance of the lateral border. The resulting change in PMC geometry could diminish any effects of increased tension of the CTrA. This study reveals a co-dependent mechanism involving balanced tension between deep abdominal and lumbar spinal muscles, which are linked through the aponeurotic components of the TLF. This implies the existence of a point of equal tension between the paraspinal muscles and the transversus abdominis and internal oblique muscles, acting through the CTrA.

Effect of rhythmic tetanic skeletal muscle contractions on peak muscle perfusion

The purpose of this investigation was to examine the effect of rhythmic tetanic skeletal muscle contractions on peak muscle perfusion by using spontaneously perfused canine gastrocnemii in situ. Simultaneous pulsatile blood pressures were measured by means of transducers placed in the popliteal artery and vein, and pulsatile flow was measured with a flow-through-type transit-time ultrasound probe placed in the venous return line. Two series of experiments were performed. In series 1, maximal vasodilation of the muscles' vascular beds was elicited by infusing a normal saline solution containing adenosine (29.3 mg/min) and sodium nitroprusside (180 microg/min) for 15 s and then simultaneously occluding both the popliteal artery and vein for 5 min. The release of occlusion initiated a maximal hyperemic response, during which time four tetanic contractions were induced with supramaximal voltage (6-8 V, 0.2-ms stimuli for 200-ms duration at 50 Hz, 1/s). In series 2, the muscles were stimulated for 3 min before the muscle contractions were stopped for a period of 3 s; stimulation was then resumed. The results of series 1 indicate that, although contractions lowered venous pressure, muscle blood flow was significantly reduced from 2,056 +/- 246 to 1,738 +/- 225 ml x kg(-1) x min(-1) when contractions were initiated and then increased significantly to 1,925 +/- 225 ml x kg(-1) x min(-1) during the first 5 s after contractions were stopped. In series 2, blood flow after 3 min of contractions averaged 1,454 +/- 149 ml x kg(-1) x min(-1). Stopping the contractions for 3 s caused blood flow to increase significantly to 1,874 +/- 172 ml x kg(-1) x min(-1); blood flow declined significantly to 1,458 +/- 139 ml x kg(-1) x min(-1) when contractions were resumed. We conclude that the mechanical action of rhythmic, synchronous, maximal isometric tetanic skeletal muscle contractions inhibits peak muscle perfusion during maximal and near-maximal vasodilation of the muscle's vascular bed. This argues against a primary role for the muscle pump in achieving peak skeletal muscle blood flow.

The effects of creatine dietary supplementation on anterior compartment pressure in the lower leg during rest and following exercise

OBJECTIVE

To examine the effects of creatine supplementation on anterior compartment pressure of the lower leg at rest and following exercise.

DESIGN

14 college-age males received creatine or placebo supplementation for 34 days. At baseline, anterior compartment pressure was measured preexercise, immediately postexercise, and 1, 5, and 15 minutes postexercise after a level treadmill run for 20 minutes at 80% of maximal aerobic power.

INTERVENTION

Following baseline testing, subjects began a 6-day creatine or placebo loading phase at a dosage of 0.3 g x kg body mass(-1) x d(-1). This was followed by a 28-day maintenance phase at a dosage of 0.03 g x kg body mass(-1) x d(-1). Subjects and investigators were blinded as to treatment administration. Subjects continued to exercise during the supplementation period. After 6 days and 34 days of supplementation. anterior compartment pressure was measured at rest and following exercise.

RESULTS

Creatine supplementation for 6 days significantly increased compartment pressure compared with the placebo group at rest (76%), immediately post- (150%), 1 minute post- (125%), 5 minute post- (106%), and 15 minute postexercise (77%). Anterior compartment pressures continued to remain significantly higher for the creatine group compared with the placebo group at rest (72%), immediately post- (125%) and 1 minute postexercise (180%) after 34 days of creatine supplementation.

CONCLUSIONS

These data indicate that creatine supplementation abnormally increases anterior compartment pressure in the lower leg at rest and following 20 minutes of level running at 80% of maximal aerobic power.

Lymph flow in sheep limbs during local exposure to subatmospheric pressure

1. Lymph flow and pressure were measured via cannulae inserted into afferent lymphatics draining the feet of anaesthetized sheep. 2. When the cannula outlet was at limb level, local exposure of the limb to graded decreases in ambient pressure caused graded increases in lymph flow with pressure values down to -50 mmHg. 3. When the cannula outlet was lowered below limb level to offset the negative pressure gradient imposed on the lymphatic vessels by suction, lymph flow rose progressively with decreasing ambient pressure values down to -70 mmHg. 4. When negative pressure gradients were imposed on the lymphatic vessels by raising the lymphatic cannula outlet in progressive steps above limb level, the vessels were able to expel lymph against gradients of up to 50 mmHg but lymph flow was greatly reduced against a gradient of 70 mmHg. 5. The results suggest that subatmospheric pressure may affect local lymph flow in two ways. By increasing blood capillary transmural pressure it may increase lymph flow by increasing tissue fluid formation. By imposing a negative pressure gradient along the lymphatics it may decrease lymph flow, especially at the most negative pressures, and the lymph flow response to subatmospheric pressure may be the algebraic sum of both effects.

Intramuscular pressure in the burned arm: measurement and response to escharotomy

Using a wick catheter technique, sequential measurements of intramuscular pressure were obtained in 31 burned arms in 18 patients. Abnormally high pressures were recorded in 90 percent of extremities and exceeded the potentially harmful level of 30 mm Hg in 42 percent. Correlation of intramuscular pressure with signs and symptoms of extremity compression, including Doppler pulses, was poor. Intramuscular pressure elevation appeared to parallel edema formation beneath the burn wound. A high incidence of pressure measurements in excess of 30 mm Hg was found in patients who had 30 percent or greater total body surface area injury (67 percent), 10 percent or greater full-thickness burns (75 percent), and extremities with circumferential involvement (57 percent). In every case echarotomy produced a dramatic decrease in intramuscular pressure, while a randomized group of extremities that were not decompressed developed sustained pressures as high as 64 mm Hg despite the presence of intact Doppler pulses. Extremities treated in this manner appeared slower in resolving edema and regaining motion and strength. Measurement of intramuscular pressure beneath the burn eschar is recommended in evaluating all patients at risk from extremity burns.

Recurrent Anterior Compartmental Syndromes

Vigorous exercise may raise compartmental pressure enough to compromise blood flow. Recurrent compartmental syndromes may be treated by altering the exercise program, but serious athletes require surgical decompression.

Simultaneous measurement of pressure in the interstitium and the terminal lymphatics of the cat mesentery

1. Simultaneous measurements of the pressure in terminal lymphatics and interstitial tissue have been made in the exteriorized cat mesentery superfused with either physiological salt solution (Krebs solution) or a water-immiscible fluorocarbon, FC-80. 2. The pressures within individual terminal lymphatics were measured using glass micropipettes attached to a servo pressure-measuring system. Tissue pressures were recorded using saline-filled cotton-wool wicks. 3. Mean pressure recorded in the terminal lymphatics of the Krebs-superfused mesentery were slightly above atmospheric (+0.2 mmHg, n = 45), while those recorded in the FC-80-superfused mesentery were slightly below atmospheric (-0.2 mmHg, n = 46). 4. Tissue pressures were also slightly subatmospheric in the in situ mesentery, and the recently exposed tissue. Continuous superfusion with Krebs solution caused the tissue pressure to rise to atmospheric pressure or above; with FC-80-superfusion the tissue pressure also rose, but never to above atmospheric pressure. 5. Isolated strips of mesentery immersed in Krebs solutions of different concentrations gained weight, but when immersed in FC-80 no change in weight was detected. 6. It was concluded that the interstitial gel of the mesentery is normally unsaturated and that superfusion with Krebs solution leads to tissue oedema. This tendency is less marked in FC-80-superfused preparations. Possible mechanisms for lymph formation and propulsion are discussed.

Measurement of the interstitial pressure in subcutaneous tissue in dogs

A probe consisting of a cotton thread fitted inside a 15-cm Teflon tube with an inner diameter of 0.8 mm and connected to a transducer was used to measure the interstitial pressure in the subcutaneous tissue in six anesthetized dogs. The measurements were reproducible with a standard deviation of ±0.64 mm Hg. In six dogs the mean pressure in the subcutaneous tissue of the thorax was --2.74 mm Hg (range --3.25 to --1.99 mm Hg). After hemorrhage and dextran (10%) infusion, the mean pressure decreased by 1.70 mm Hg. After infusion of lactated Ringer's solution, the pressure increased to the control values.