Effect of ropivacaine infiltration on muscle regeneration: a morphometric analysis.

BACKGROUND/AIM: Local anaesthetic myotoxicity is a well described phenomenon resulting in reversible muscle damage. Considering that in previous studies microscopic images were evaluated without quantification of morphologic characteristics, the aim of the present study was evaluate muscle regeneration after local anaesthetic infiltration. MATERIALS AND METHODS: Wistar rats underwent injection of the left tibialis anterior muscle with ropivacaine (0.75%, group HC or 0.375%, group LC), while the contralateral muscle was injected with saline (group SL). Six weeks later, the muscles were dissected, stained using acid ATPase and examined under light microscope coupled with a computer imaging system for morphometric analysis. Sections were evaluated regarding the content of different muscle fibre types (type I, IIa and IIb), fibre cross-section area and perimeter. RESULTS: Groups were comparable regarding the ratio of different muscle fibre types. Regenerated type I fibres of both HC and LC groups had significant greater mean cross-sectional area and perimeter, compared to SL fibres. No signs of necrosis or inflammation were observed. Type IIa and IIb fibres didn't show significant differences. CONCLUSIONS: Regenerated muscles, following local anaesthetic application, showed long-term morphological differences, which could lead to impaired function. Further studies are needed, in order to clarify the underlying cellular mechanisms and the subsequent possible functional impairment.

Comparison between intubation through ILMA and Airtraq, in different non-conventional patient positions: a manikin study.

BACKGROUND: Tracheal intubation is often difficult in the prehospital setting, especially in trapped casualties, when long extrication time is anticipated and conventional laryngoscopy cannot be achieved. The aim of the present study was the comparison of applicability and efficacy of two alternative techniques: intubation using a laryngeal mask airway (ILMA) or an Airtraq laryngoscope in different patient positions, using an airway management manikin. METHODS: 20 anaesthetists attempted manikin intubations standing behind the manikin (Sup), standing in front and facing the manikin's head (Fac), facing the manikin in the sitting position (Sit) and facing the manikin lying in the lateral decubitus position (Lat), using either Airtraq or ILMA techniques. The intubations were evaluated regarding the success rate, number of attempts and time needed for successful intubation, teeth damage and overall difficulty. RESULTS: All intubation attempts were successful for both techniques. Intubations through ILMA were completed with a significantly greater number of attempts and longer time in the Lat position, compared to Fac, Sit and Sup (p<0.05), whereas intubations using Airtraq in the Sup and Fac positions were completed with a significantly greater number of attempts and longer time, compared to Sit and Lat positions (p<0.05). Both ILMA and Airtraq can be used for securing the airway when direct laryngoscopy is impossible due to patient position. ILMA seems to cause greater difficulty in the Lat position, whereas Airtraq intubation is more easily performed in the Sit and Lat positions. CONCLUSIONS: These preliminary data in manikins could indicate the applicability of the methods to the prehospital setting.

The effect of intra-abdominal hypertension alone or combined intra-abdominal hypertension-endotoxemia in cerebral oxygenation in a porcine model.

BACKGROUND: Abdominal compartment syndrome (ACS) has been recognized as an entity, affecting cardiovascular, pulmonary, and cerebral function, while it is often complicated with sepsis. Goal of the study was the evaluation of brain oxygenation during ACS alone and in combination with endotoxinemia. MATERIALS AND METHODS: Sixteen pigs, undergone intra-abdominal hypertension, were allocated to receive intravenous administration of either saline or endotoxin. Pigs were evaluated regarding brain tissue oxygenation (PbrO2), systemic oxygenation (PaO2) and regional cerebral blood flow (rCBF). RESULTS: Statistical analysis revealed significant reduction of PbrO2 over time for sepsis group, after endotoxin administration. Regarding differences between groups, sepsis group experienced lower PbrO2 values, compared to saline group, only after endotoxin administration. Both groups experienced reduction in arterial oxygenation, with greater pertubations seen after sepsis induction. Regarding rCBF, septic pigs showed greater flow values, while ACS alone did not influence rCBF. ACS has no deleterious effects in cerebral oxygenation and flow, provided systemic oxygenation and CPP are maintained above normal value. CONCLUSIONS: Combined sepsis-ACS lead to perturbations in cerebral oxygenation, in conjunction with greater rCBF values. The latter could be ascribed to abnormalities in oxygen extraction.

Comparison between newer local anesthetics for myofascial pain syndrome management.

Myofascial pain syndromes are characterized by the presence of painful loci within muscles, tendons or ligaments, called trigger points. Infiltration of these points with local anesthetics is often used as a treatment modality. The aim of the study was to comparatively evaluate 0.25% levobupivacaine and 0.25% ropivacaine for trigger point injection regarding pain on injection, treatment efficacy and duration of symptoms remission. Sixty-eight patients, suffering from myofascial pain syndromes, were randomly assigned to two groups to receive either levobupivacaine or ropivacaine for trigger-point injection. After completion of the procedure, patients were asked to rate pain during injection and efficacy of the treatment, based on immediate relief. Two weeks later, they were asked about the duration of this relief. Statistical analysis did not reveal significant differences between groups with respect to pain during injection, efficacy of the treatment and duration of pain relief. The two local anesthetics seem to be equally effective for trigger point infiltration.

Ropivacaine myotoxicity after single intramuscular injection in rats.

BACKGROUND AND OBJECTIVE: We conducted this study in order to evaluate the potential myotoxic effects of ropivacaine after single injection in rats and the time-course of the possible damage. METHODS: One hundred and twenty-eight male Wistar rats were allocated to four different groups. The first three groups received intramuscular injections with ropivacaine 0.75%, ropivacaine 0.5% and normal saline, respectively, into the right tibialis anterior muscle. The fourth group received needle puncture without injection. Eight rats from each group were sacrificed 2, 4, 7 and 30 days after injection. Samples were blindly examined under light microscope for evidence of myotoxicity, scored as 0 = no damage to 3 = myonecrosis and statistically analysed. Samples obtained 7 days after injection were also examined under transmission electron microscope. RESULTS: Ropivacaine 0.75% and ropivacaine 0.5% caused extensive destruction to muscles fibres, compared to saline or needle on days 2, 4 and 7. Statistically significant differences were found in muscle damage by drug injections among all groups except for saline vs. needle groups. Thirty days after injections all sample appearances had returned to normal. CONCLUSIONS: Ropivacaine after single intramuscular injection caused reversible muscle damage in a dose-dependent manner.

Rocuronium duration of action under sevoflurane, desflurane or propofol anaesthesia.

BACKGROUND AND OBJECTIVE: We conducted a prospective randomized study to evaluate whether the duration of action of a single bolus dose of rocuronium is influenced by maintenance of anaesthesia with sevoflurane, desflurane or propofol infusion. METHODS: Fifty-seven ASA I-II patients undergoing elective abdominal surgery were enrolled in this study. Anaesthesia was induced with thiopental 3-5 mg kg(-1) or propofol 2.5 mg kg(-1) and fentanyl 5 microg kg(-1) and tracheal intubation was facilitated with rocuronium 0.9 mg kg(-1). Thereafter patients were randomly allocated to three different groups to receive sevoflurane, desflurane or propofol for maintenance of anaesthesia. Recovery of neuromuscular function was monitored by single twitch stimulation of the ulnar nerve and by recording the adductor pollicis response using accelerometry. Intergroup recovery times to 5% of control value of single twitch were analysed using analysis of variance with Bonferroni correction. RESULTS: The mean (95% confidence interval) recovery time to 5% of control value of single twitch during desflurane anaesthesia was 90.18 (86.11-94.25) min. Significantly shorter recovery times were observed during sevoflurane or propofol anaesthesia, 58.86 (54.73-62.99) min and 51.11 (45.47-56.74) min, respectively (P < 0.001). There were also significant differences in the recovery time between groups receiving desflurane vs. sevoflurane (P < 0.001) and desflurane vs. propofol (P < 0.001). CONCLUSIONS: Desflurane anaesthesia significantly prolongs the duration of action of rocuronium at 0.9 mg kg(-1) single bolus dose, compared to sevoflurane or propofol anaesthesia maintenance regimens.