Time course of mitochondrial metabolism alterations to repeated injections of bupivacaine in rat muscle.

PURPOSE: Bupivacaine-induced myotoxicity is associated with mitochondrial bioenergetic alterations. The impact of the duration of bupivacaine treatment on mitochondrial energy production remains undetermined. Here, we assessed, in vivo, the alteration of mitochondrial metabolism following different durations of bupivacaine exposure (40, 56, or 112 hr) that correspond to 5, 7, or 14 repeated injections of 0.25% bupivacaine, respectively. METHODS: Rats were divided randomly into seven different groups: one control group (no catheter); three groups with normal saline injections (1 mL x kg(-1)) every eight hours via a femoral nerve catheter for 40, 56, and 112 hr, respectively; and three groups with 0.25% bupivacaine injections (1 mL x kg(-1)) every eight hours via a femoral nerve catheter for 40, 56, and 112 hr. Psoas and gracilis muscle samples located within the bupivacaine infusion-diffusion space were investigated. To estimate mitochondrial respiratory capacity, the protein content of the mitochondrial respiratory chain apparatus was evaluated by measuring citrate synthase activity. To measure mitochondrial respiratory function, adenosine diphosphate-stimulated oxygen consumption was measured by polarography in saponin-skinned muscle fibres using glutamate-malate or succinate as energy substrates. RESULTS: In psoas and gracilis muscles, saline solution had no effect on the two mitochondrial parameters. Bupivacaine induced a significant decrease in the citrate synthase activity in psoas (r(2) = 0.74; P < 0.001) and gracilis muscle (r(2) = 0.52; P < 0.001), and there was a significant decrease in the adenosine diphosphate-stimulated oxygen consumption using glutamate or succinate as substrates in both muscles (P < 0.001). CONCLUSIONS: The severity of bupivacaine-induced myotoxicity is closely linked to the duration of bupivacaine exposure in the muscle fibres located close to the catheter tip.

Effects of controlled mechanical ventilation on respiratory muscle contractile properties in rabbits.

OBJECTIVE: We examined in rabbits the effects of more than 48 h of mechanical ventilation on the contractile properties and fiber type adaptations of the respiratory muscles. DESIGN AND SETTING: Experimental prospective study in a university laboratory. ANIMALS AND INTERVENTIONS: Nineteen rabbits were randomly allocated to two groups: control (n=10) or mechanically ventilated (MV; n=9) for 51+/-3 h. MEASUREMENTS AND RESULTS: Respiratory muscles contractile properties were analyzed before and after a fatigue protocol using in vivo isometric 1-s tetanic contraction characteristics in both muscles: peak tetanic force, contraction time, relaxation time, and total contraction time. Both muscle fiber type proportions, diameter, and cross-sectional areas were measured using ATPase staining. The MV rabbits showed significant weight loss in both muscles, accompanied by a reduced peak tetanic force (9.96+/-3.2 vs. 7.44+/-2.2 N for diaphragm of control and MV animals respectively), fatigue resistance index, and increased relaxation time (57.5+/-8.7 vs. 85.8+/-9.4 ms for diaphragm of control and MV animals) and contraction time. These impairments in the MV group worsened after the fatigue runs. Both muscle showed a significant atrophy of type IIa and IIb fibers but a stability in type I fibers cross-sectional area. CONCLUSIONS: Mechanical ventilation in rabbits produces alterations in contractile properties of the diaphragm and 5th external intercostal muscle, increases both muscles fatigue, and promotes atrophy of type II fibers.

Effects of prolonged mechanical ventilation on respiratory muscle ultrastructure and mitochondrial respiration in rabbits.

OBJECTIVE: To investigate in rabbits whether prolonged mechanical ventilation (PMV) leads to ultrastructural changes in respiratory muscles and alters diaphragm mitochondrial respiration. DESIGN AND SETTING: Experimental prospective study in a university laboratory. ANIMALS AND INTERVENTIONS: We studied respiratory muscles of seven rabbits after 49+/-1 h of controlled mechanical ventilation. Ten nonventilated rabbits were used as a control group. MEASUREMENTS AND RESULTS: After mechanical ventilation electron-microscopic observations of the diaphragm and the external intercostal muscles revealed disrupted myofibrils, increased number of lipid vacuoles in the sarcoplasm, and smaller mitochondria with focal membrane disruptions. Volumetric and numerical densities of the mitochondria were significantly lower in the PMV group than the control group. Mitochondrial respiration was quantified in isolated diaphragm muscle-cell mitochondria using two respiratory substrates. There was no difference in oxygen consumption values in the three states of mitochondrial respiration between the two groups except for state 2 (basal state) with pyruvate/malate parameter (53.5+/-20 for the ventilated group vs. 33.8+/-10.2 nmol atom O/mg per minute for the control group). There was no significant difference between groups in ADP/O ratio or respiratory control ratio. CONCLUSIONS: PMV leads to respiratory muscle cell degeneration and minor changes in oxidative phosphorylation coupling in diaphragmatic mitochondria. These phenomena may mediate part of damage of respiratory muscles after inactivity related to PMV.

Fascia iliaca compartment block for femoral bone fractures in prehospital care.

BACKGROUND AND OBJECTIVES: The fascia iliaca compartment block provides a faster and more consistent simultaneous blockade of the lateral cutaneous and femoral nerves than the "3 in 1" block. We studied the effectiveness of this technique for analgesia after a femoral bone fracture in pre-hospital care. METHODS: Patients with an isolated femoral shaft fracture were included. A fascia iliaca compartment block was performed on all of them. Twenty milliliters of lidocaine 1.5 % with epinephrine were injected under the fascia iliaca. The intensity of pain was measured using a simplified verbal scale (SVS) from 0 (no pain) to 4 (extreme pain). The SVS was noted before the block was performed, 10 minutes later, and then on admission to the trauma care center. Sensory blockade was evaluated using cold perception in the lateral, medial, and internal part of the thigh 10 minutes after block performance and on arrival at the trauma care center. RESULTS: Twenty-seven patients were enrolled in this study. The SVS was 3 (3-4) before the block, 1 (0-2) 10 minutes after the block, and 0 (0-1) when arriving at the trauma care center (P <.05). The SVS was lower when the internal part of the thigh was blocked. CONCLUSION: The fascia iliaca compartment block is a simple, inexpensive, and effective method of prehospital analgesia for femoral shaft fracture. A sensory block of the internal part of the thigh is an early predictive sign of optimal pain relief.

Percutaneous electrode guidance using the insulated needle for prelocation of peripheral nerves during axillary plexus blocks.

BACKGROUND AND OBJECTIVES: Short reports have noted that percutaneous prelocation is helpful in determining the anatomic course of a peripheral nerve, and, thereby, may serve as a guide for block needle insertion. We prospectively studied percutaneous electrode guidance to assist axillary brachial plexus blocks. METHODS: In 131 consecutive patients, the tip of an insulated needle emitting 5 mA was placed on the skin above and below the axillary artery to obtain a hand motor response characteristic of the median, ulnar, and radial nerves in succession. The current was reduced until all movement had ceased. The needle was then inserted toward the nerve to be blocked, decreasing the intensity from 2 mA to 0.5 mA, so that the same selected motor response was still obtained. The length of the needle inserted was noted, and 1.5% lidocaine was injected. Pain verbal analogic score (VAS) values were noted during both procedures. Complete sensory blockade was evaluated at 30 min. RESULTS: Rates of successful percutaneous electrode guidance were 94.6% for the median nerve, 89.4% for the radial nerve, 88.5% for the ulnar nerve, and 85.5% for all 3 nerves together. A significant correlation was found between the lowest percutaneous current applied and the depth of the nerve stimulated at 0.5 mA. Pain VAS values were significantly lower during percutaneous stimulation than during needle insertion (P <.05). Sensory block for all 3 nerves was noted in 92% of patients. CONCLUSIONS: Percutaneous electrode guidance using the insulated needle enabled clinicians to locate the terminal branches of the plexus in the axilla and appreciate their depth. This method could, therefore, minimize patient discomfort and perhaps the risk of nerve trauma.

Comparison of continuous 3-in-1 and fascia Iliaca compartment blocks for postoperative analgesia: feasibility, catheter migration, distribution of sensory block, and analgesic efficacy.

BACKGROUND AND OBJECTIVES: Efficacy and technical aspects of continuous 3-in-1 and fascia iliaca compartment blocks were compared. METHODS: Forty-four patients scheduled for cruciate ligament repair or femur surgery were randomly divided into 2 groups. After surgery with the patient anesthetized, catheters were placed for continuous 3-in-1 blocks by means of a nerve stimulator (group 1). In group 2, the catheter was inserted for continuous fascia iliaca compartment block without the use of a nerve stimulator. In both groups, a 5-mg/kg bolus of 0.5% ropivacaine was administered followed by continuous infusion of 0.1 mL/kg/h of 0.2% ropivacaine for 48 hours. In the postoperative period, all the patients received parenteral propacetamol (6 g daily) and ketoprofen (200 mg daily) and 0.1 mg/kg of subcutaneous morphine as rescue analgesia if the visual analog scale (VAS) pain values were greater than 30 mm. We evaluated the technical difficulties relative to catheter placement, the location of the catheter, the analgesic efficacy, and the distribution of the sensory block at 1 hour, 24 hours, and 48 hours. RESULTS: Catheter placement was faster in group 2, and the absence of nerve stimulation decreased material costs (P <.05). No significant difference was observed between groups concerning location of the catheter tip under the fascia iliaca. In both groups, the distribution of the sensory block and its course were similar except for those of the obturator nerve (more sensory blocks in group 1, P <.05). No significant difference was noted between the groups regarding median VAS pain values and consumption of morphine during the 48-hour period. No major side effect was observed. CONCLUSIONS: The authors conclude that a catheter for continuous lumbar plexus block can be placed more quickly and at lesser cost using the fascia iliaca technique than the perivascular technique with equivalent postoperative analgesic efficacy.

Intrathecal bupivacaine protects against extension of lesions in an acute photochemical spinal cord injury model.

PURPOSE: The photochemical spinal-cord injury model reproduces extensive secondary lesions that occur after spinal injury. We have evaluated in 27 rats the functional, electrophysiological and anatomical consequences of a photochemical spinal-cord lesion induced before or after intrathecal injection of bupivacaine. METHODS: After randomization, nine rats received 20 micro L of intrathecal bupivacaine 0.5% 15 min before a photochemical spinal-cord lesion (Group I) and eight rats received 20 micro L intrathecal bupivacaine 15 min after such a lesion (Group II). Ten rats received 20 micro L of saline 15 min before the photochemical injury (control group). Paraplegia was tested on days one, three, five, seven, nine, 12, 15 and 18 using an evaluation of hindlimb movements and an inclined plane stability test. Sensory block was evaluated by the animal's response when each hindlimb was brought into contact with a hot plate. Sympathetic injury was evaluated in terms of bladder voiding dysfunction. On day 18, residual somatosensory evoked potentials (SEP) were measured and the area of the intact spinal cord was determined using a digitalized system. RESULTS: Early paraplegia recovery was found in the two bupivacaine groups (P < 0.05). On day 12, motor recovery was complete in both bupivacaine groups whereas recovery was not complete on day 18 in the control group. Compared to the control group, inclined plane stability recovered earlier in Groups I and II, from day three to day 15. Sensory and sympathetic block scores were not different in the three groups. Nevertheless, SEP latencies were longer and amplitudes were lower in control group rats compared with the two bupivacaine groups on day 18. The intact spinal-cord cross-sectional area around the lesion was not different in the three groups. CONCLUSION: Twenty microlitres of intrathecal bupivacaine before or after acute photochemical spinal injury improves hindlimb motor recovery and SEP parameters in rats.

Continuous three-in-one block for postoperative pain after lower limb orthopedic surgery: where do the catheters go?

UNLABELLED: Continuous three-in-one block is widely used for postoperative analgesia after proximal lower limb surgery, but location of the catheter has not been well addressed in the literature. We prospectively studied, in 100 patients, the characteristics of catheter threading under the iliac fascia and the correlations between catheter tip location and effective sensory and motor blockade of the three principal nerves of the lumbar plexus. Postoperatively, in conscious patients, 16 to 20 cm of a catheter was placed in the fascial sheath after femoral nerve location with a nerve stimulator. Contrast media (3 mL Iopamidol 390) was injected, and the catheter tip was located by means of an anteroposterior pelvic radiograph. An equal-volume mixture of 0.5% bupivacaine/2% lidocaine with epinephrine (30 mL) was injected through the catheter. Patient and catheter-insertion characteristics were noted. Thirty minutes after injection, sensory blockade was evaluated in the cutaneous territories of the lateral femoral cutaneous, femoral, and obturator nerves, along with motor blockade of the last two nerves. Pain scores at 30 min were also recorded. Seven block failures were noted. The tip of the catheter reached the lumbar plexus (Group 1) in 23% of the patients and lay deep to the medial (Group 2) or lateral (Group 3) part of the fascia iliaca in 33% and 37% of the patients, respectively. Demographic data and catheter threading characteristics were comparable among the groups. A three-in-one block was noted in 91% of Group 1 patients, but in only 52% and 27% of Group 2 and 3 patients, respectively (P < 0.05). Comparing Group 2 and 3 patients, sensory block was achieved in respectively 100% and 94% for the femoral nerve, 52% and 94% for the lateral femoral cutaneous nerve (P < 0.05), and 82% and 27% for the obturator nerve (P < 0.05). Visual analog scale pain scores on movement were significantly lower in Group 1 patients (P < 0.05). We conclude that during a continuous three-in-one block, the threaded catheter rarely reached the lumbar plexus. The quality of sensory and motor blockade and initial pain relief depend on the location of the catheter tip under the fascia iliaca. IMPLICATIONS: The course of a continuous three-in-one block catheter is unpredictable. Only 23% of the catheters lie near the lumbar plexus. The success of sensory and motor blocks, as well as postoperative analgesia, depend on the position of the catheter under the fascia iliaca.