Bloqueo del plano del erector espinal en L4 en cirugía de artrodesis lumbar: serie de casos / L4 erector spinal plane block after lumbar spine arthrodesi: a case-series

INTRODUCCIÓN: El bloqueo en el plano del erector espinal (erector spinae plane [ESP]) a nivel torácico se ha desarrollado en los últimos años en multitud de procedimientos quirúrgicos, incluido los pacientes tratados mediante artrodesis lumbar. Nos propusimos evaluar el efecto analgésico del ESP realizado a nivel lumbar L4 en el postoperatorio inmediato en pacientes intervenidos por artrodesis lumbar. MÉTODOS Y CASOS CLÍNICOS: Descripción de una serie de 8 casos clínicos intervenidos por artrodesis lumbar a quienes se les realizó un bloqueo del ESP lumbar bilateral en L4 con 20 ml de ropivacaína al 0,2% por lado. Se describió la intensidad del dolor durante las primeras 48 h del postoperatorio mediante escala visual analógica y la analgesia de rescate empleada. El dolor postoperatorio en reposo fue controlado en todos los pacientes (entre 0 y 3), si bien el dolor en movimiento fue considerado entre leve y severo según los pacientes (entre 0 y 8). El consumo de rescate fue entre 1 y 22mg de morfina. CONCLUSIONES: El ESP lumbar parece contribuir al control del dolor postoperatorio inmediato durante las primeras 48 h en pacientes intervenidos por artrodesis lumbar

INTRODUCTION: Thoracic erector spinae plane block is now performed in many different surgical procedures, including lumbar spinal fusion. We evaluated the analgesic effect of lumbar ESP performed at L4 after lumbar spinal fusion surgery. METHODS AND CASE SERIES: Eight patients scheduled for lumbar spinal fusion were included in the case series. Erector spinae plane block was performed at L4 preoperatively, administering 20 ml of 0.2% ropivacaine on each side. We recorded patient-reported pain intensity during the first 48 postoperative hours using a visual analogue scale (VAS) and rescue analgesia requirements. Pain at rest was controlled in all patients (VAS 0 to 3), although pain on movement ranged from mild to severe (VAS 0 to 8). Rescue analgesia consumption ranged from 1 to 22mg morphine. CONCLUSIONS: Lumbar ESP appears to contribute to pain control during the first 48hours after lumbar spinal fusion

Anatomical description of anaesthetic spread after deep erector spinae block at L-4. / Estudio anatómico de la distribución del volumen administrado tras bloqueo en el plano profundo del erector espinal a nivel lumbar.

INTRODUCTION: Thoracic erector spinae plane (ESP) block is now used for postoperative analgesia. However, although reports of lumbar ESP have been published, the anesthetic spread and mechanism of action of this technique remains unclear. We describe the lumbar ESP block technique and evaluate the spread of 20ml of solution administered at the level of the transverse process of L4 in a cadaver model. METHODS: Observational study after 12 lumbar ESP blocks at L4 on a fresh cadaver model (6 bilaterally). The spread of 20ml of injected contrast solution was assessed by computed tomography in all 6 samples. Four of the samples were evaluated by anatomical study, 2 by plane dissection, and 2 others were frozen and cut into 2-2.5cm axial slices. RESULTS: The injected solution spread from L2 to L5 in a cranio-caudal direction in the erector spinae muscle, reaching the facet joints medially and the thoracolumbar fascia laterally. In 33% of cases the solution did not spread anterior to the transverse process; in 51%, spread was minimal and did not affect the corresponding spinal nerves, and in 2 samples (16%), spread was extensive and reached the corresponding spinal nerves. CONCLUSIONS: Lumbar ESP at L4 always acts on the posterior branches of the spinal nerves, but seldom spreads to the paravertebral space to block the spinal nerve.

L4 erector spinal plane block after lumbar spine arthrodesi: A case-series. / Bloqueo del plano del erector espinal en L4 en cirugía de artrodesis lumbar: serie de casos.

INTRODUCTION: Thoracic erector spinae plane block is now performed in many different surgical procedures, including lumbar spinal fusion. We evaluated the analgesic effect of lumbar ESP performed at L4 after lumbar spinal fusion surgery. METHODS AND CASE SERIES: Eight patients scheduled for lumbar spinal fusion were included in the case series. Erector spinae plane block was performed at L4 preoperatively, administering 20ml of 0.2% ropivacaine on each side. We recorded patient-reported pain intensity during the first 48 postoperative hours using a visual analogue scale (VAS) and rescue analgesia requirements. Pain at rest was controlled in all patients (VAS 0 to 3), although pain on movement ranged from mild to severe (VAS 0 to 8). Rescue analgesia consumption ranged from 1 to 22mg morphine. CONCLUSIONS: Lumbar ESP appears to contribute to pain control during the first 48hours after lumbar spinal fusion.

Evaluación del área de sección del nervio mediano tras la inyección intraneural o perineural / Cross-sectional area of the median nerve after intraneural vs perineural low volume administration

Introducción: Conocer la relación entre la aguja y el nervio durante el bloqueo de nervio periférico es de interés para evitar el daño neural; sin embargo, los signos de inyección intraneural no se hallan claramente establecidos. Nos propusimos determinar los cambios observados en el nervio periférico tras inyectar 1ml de solución en disposición intraneural o perineural de la aguja. Material y métodos: Se utilizaron 10 cadáveres frescos, a los cuales se les realizó bloqueo de nervio mediano ecoguiado en plano en 60 ocasiones (3 por brazo), realizando una punción intraneural (n=30) o perineural (n=30) según aleatorización previa. Tras el consenso de localización por 7 especialistas, se inyectó 1ml de solución y se evaluó el cambio en el área de sección del nervio y el desplazamiento a lo largo del mismo. Resultados: El área de sección del nervio mediano se aumentó en ambos grupos, sin embargo, el incremento fue significativamente mayor en el grupo intraneural (perineural 0,007+/-0,013 vs. intraneural 0,032+/-0,021cm2, p<0,0001). Un incremento superior al 27% del área de sección asegura una inyección intraneural en el nervio mediano según el análisis de la curva ROC. La difusión proximal y la distal se observó con mayor frecuencia en el grupo intraneural (proximal: 86 vs. 14%; p<0,0001. Distal: 43 vs. 4%; p<0,0001). Conclusiones: En base a nuestro estudio experimental concluimos que la inyección de un pequeño volumen (1ml) permite discriminar la disposición de la aguja intraneural vs. perineural en un porcentaje elevado de casos. Por ello, sugerimos que esta «dosis test» debe de considerarse en los algoritmos de seguridad si queremos reducir la incidencia de inyección intraneural

Introduction: To recognise the relationship between the needle tip and the median nerve during peripheral nerve block is of interest to avoid neural damage. However, signs of intraneural injection are not clearly established. The aim of this study was to define the changes observed in the peripheral nerve after the intraneural or perineural administration of 1ml of solution. Material and methods: Ultrasound guided median nerve blocks were performed in the forearm of 10 fresh cadavers on 60 occasions (3 per forearm). They were randomised into the intraneural (n=30) or perineural (n=30) location of the needle tip, after the consensus of location by 7 specialists. After 1ml of solution was injected an evaluation was made of the changes in the cross-sectional area of the nerve, as well as the displacement along the nerve. Results: The cross-sectional area of the median nerve was increased in both groups, however, the increase was significantly higher in the intraneural group (perineural 0.007+/-0.013cm2 vs. intraneural 0.032+/-0.021cm2, P<.0001). An increase of more than 27% of the area ensures an intraneural injection in the median nerve according to the ROC curve analysis. Both proximal and distal diffusion were observed more frequently in the intraneural group (proximal: 86% vs 14%, P<.0001, Distal: 43% vs 4%, P<.0001). Conclusions: Based on this experimental study, it is concluded that the injection of a small volume (1ml) allows to discriminate the disposition of the intraneural vs perineural needle in a high percentage of cases. Therefore, it is suggested that this "dose test" should be considered in the safety algorithms if it is required to reduce the incidence of intraneural injection

Cross-sectional area of the median nerve after intraneural vs perineural low volume administration. / Evaluación del área de sección del nervio mediano tras la inyección intraneural o perineural.

INTRODUCTION: To recognise the relationship between the needle tip and the median nerve during peripheral nerve block is of interest to avoid neural damage. However, signs of intraneural injection are not clearly established. The aim of this study was to define the changes observed in the peripheral nerve after the intraneural or perineural administration of 1ml of solution. MATERIAL AND METHODS: Ultrasound guided median nerve blocks were performed in the forearm of 10 fresh cadavers on 60 occasions (3 per forearm). They were randomised into the intraneural (n=30) or perineural (n=30) location of the needle tip, after the consensus of location by 7 specialists. After 1ml of solution was injected an evaluation was made of the changes in the cross-sectional area of the nerve, as well as the displacement along the nerve. RESULTS: The cross-sectional area of the median nerve was increased in both groups, however, the increase was significantly higher in the intraneural group (perineural 0.007±0.013cm2 vs. intraneural 0.032±0.021cm2, P<.0001). An increase of more than 27% of the area ensures an intraneural injection in the median nerve according to the ROC curve analysis. Both proximal and distal diffusion were observed more frequently in the intraneural group (proximal: 86% vs 14%, P<.0001, Distal: 43% vs 4%, P<.0001). CONCLUSIONS: Based on this experimental study, it is concluded that the injection of a small volume (1ml) allows to discriminate the disposition of the intraneural vs perineural needle in a high percentage of cases. Therefore, it is suggested that this "dose test" should be considered in the safety algorithms if it is required to reduce the incidence of intraneural injection.

On the multiple functional roles of the active site histidine in catalysis and allosteric regulation of Escherichia coli glucosamine 6-phosphate deaminase.

The active site of glucosamine-6-phosphate deaminase (EC 3.5.99.6, formerly 5.3.1.10) from Escherichia coli was first characterized on the basis of the crystallographic structure of the enzyme bound to the competitive inhibitor 2-amino-2-deoxy-glucitol 6-phosphate. The structure corresponds to the R allosteric state of the enzyme; it shows the side-chain of His143 in close proximity to the O5 atom of the inhibitor. This arrangement suggests that His143 could have a role in the catalysis of the ring-opening step of glucosamine 6-phosphate whose alpha-anomer is the true substrate. The imidazole group of this active-site histidine contacts the carboxy groups from Glu148 and Asp141, via its Ndelta1 atom [Oliva et al. (1995) Structure 3, 1323-1332]. These interactions change in the T state because the side chain of Glu148 moves toward the allosteric site, leaving at the active site the dyad Asp141-His143 [Horjales et al. (1999) Structure 7, 527-536]. In this research, a dual approach using site-directed mutagenesis and controlled chemical modification of histidine residues has been used to investigate the role of the active-site histidine. Our results support a multifunctional role of His143; in the forward reaction, it is involved in the catalysis of the ring-opening step of the substrate, glucosamine 6-P. In the reverse reaction, the substrate fructose 6-P binds in its open chain, carbonylic form. The role of His143 in the binding of both glucosamine 6-P and reaction intermediates in their extended-chain forms was demonstrated by binding experiments using the reaction intermediate analogue, 2-amino-2-deoxy-D-glucitol 6-phosphate. His143 was also shown to be a critical residue for the conformational coupling between active and allosteric sites. From the pH dependence of the reactivity of the active site histidine to diethyl dicarbonate, we observed a pK(a) change of 1.2 units to the acid side when the enzyme undergoes the allosteric T to R transition during which the side chain of Glu148 moves toward the active site. The kinetic study of the Glu148-Gln mutant deaminase shows that the loss of the carboxy group and its replacement with the corresponding amide modifies the k(cat) versus pH profile of the enzyme, suggesting that the catalytic step requiring the participation of His143 has become rate-limiting. This, in turn, indicates that the interaction Glu148-His143 in the wild-type enzyme in the R state contributes to make the enzyme functional over a wide pH range.

On the role of the N-terminal group in the allosteric function of glucosamine-6-phosphate deaminase from Escherichia coli.

Glucosamine-6-phosphate deaminase (EC 3.5.99.6) from Escherichia coli is an allosteric enzyme of the K-type, activated by N-acetylglucosamine 6-phosphate. It is a homohexamer and has six allosteric sites located in clefts between the subunits. The amino acid side-chains in the allosteric site involved in phosphate binding are Arg158, Lys160 and Ser151 from one subunit and the N-terminal amino group from the facing polypeptide chain. To study the functional role of the terminal amino group, we utilized a specific non-enzymic transamination reaction, and we further reduced the product with borohydride, to obtain the corresponding enzyme with a terminal hydroxy group. Several experimental controls were performed to assess the procedure, including reconditioning of the enzyme samples by refolding chromatography. Allosteric activation by N-acetylglucosamine 6-phosphate became of the K-V mixed type in the transaminated protein. Its kinetic study suggests that the allosteric equilibrium for this modified enzyme is displaced to the R state, with the consequent loss of co-operativity. The deaminase with a terminal hydroxy acid, obtained by reducing the transaminated enzyme, showed significant recovery of the catalytic activity and its allosteric activation pattern became similar to that found for the unmodified enzyme. It had lost, however, the pH-dependence of homotropic co-operativity shown by the unmodified deaminase in the pH range 6-8. These results show that the terminal amino group plays a part in the co-operativity of the enzyme and, more importantly, indicate that the loss of this co- operativity at low pH is due to the hydronation of this amino group.

Crystal structure and functional analysis of Ras binding to its effector phosphoinositide 3-kinase gamma.

Ras activation of phosphoinositide 3-kinase (PI3K) is important for survival of transformed cells. We find that PI3Kgamma is strongly and directly activated by H-Ras G12V in vivo or by GTPgammaS-loaded H-Ras in vitro. We have determined a crystal structure of a PI3Kgamma/Ras.GMPPNP complex. A critical loop in the Ras binding domain positions Ras so that it uses its switch I and switch II regions to bind PI3Kgamma. Mutagenesis shows that interactions with both regions are essential for binding PI3Kgamma. Ras also forms a direct contact with the PI3Kgamma catalytic domain. These unique Ras/PI3Kgamma interactions are likely to be shared by PI3Kalpha. The complex with Ras shows a change in the PI3K conformation that may represent an allosteric component of Ras activation.

Mapping the phospholipid-binding surface and translocation determinants of the C2 domain from cytosolic phospholipase A2.

Cytosolic phospholipase A2 (cPLA2) plays a key role in the generation of arachidonic acid, a precursor of potent inflammatory mediators. Intact cPLA2 is known to translocate in a calcium-dependent manner from the cytosol to the nuclear envelope and endoplasmic reticulum. We show here that the C2 domain of cPLA2 alone is sufficient for this calcium-dependent translocation in living cells. We have identified sets of exposed hydrophobic residues in loops known as calcium-binding region (CBR) 1 and CBR3, which surround the C2 domain calcium-binding sites, whose mutation dramatically decreased phospholipid binding in vitro without significantly affecting calcium binding. Mutation of a residue that binds calcium ions (D43N) also eliminated phospholipid binding. The same mutations that prevent phospholipid binding of the isolated C2 domain in vitro abolished the calcium-dependent translocation of cPLA2 to internal membranes in vivo, suggesting that the membrane targeting is driven largely by direct interactions with the phospholipid bilayer. Using fluorescence quenching by spin-labeled phospholipids for a series of mutants containing a single tryptophan residue at various positions in the cPLA2 C2 domain, we show that two of the calcium-binding loops, CBR1 and CBR3, penetrate in a calcium-dependent manner into the hydrophobic core of the phospholipid bilayer, establishing an anchor for docking the domain onto the membrane.