The Use of Somatosensory Evoked Potentials to Determine the Relationship Between Intraoperative Arterial Blood Pressure and Intraoperative Upper Extremity Position-Related Neurapraxia in the Prone Surrender Position During Spine Surgery: A Retrospective Analysis.

BACKGROUND: Peripheral nerve injury is a significant perioperative problem. Intraoperative position-related neurapraxia may indicate impending peripheral nerve injury and can be detected by changes in somatosensory evoked potentials (SSEP). The purpose of this retrospective analysis of spine surgeries performed under general anesthesia with SSEP monitoring was to determine the relationship between intraoperative mean arterial blood pressure (MAP) and intraoperative upper extremity position-related neurapraxia in the prone surrender (superman) position. METHODS: We reviewed a computerized database of spine surgeries performed on adult patients in the prone surrender position. The authors reviewed intraoperative SSEP monitoring reports to identify the patients who developed intraoperative upper extremity position-related neurapraxia (case group) and patients who did not (control group). Propensity matching was performed to derive 2 demographically matched groups. Preoperative and intraoperative variables were included in the univariate Cox regression analysis of risk factors associated with neurapraxia. Multivariate Cox regression models were used to identify the independent risk factors. RESULTS: One hundred fifty-two patients were included in the analysis. The case group included 32 patients, whereas the control group included 120 matched patients. Intraoperative MAP <55 mm Hg for a total duration of ≥5 minutes was an independent risk factor associated with a greater incidence of upper extremity position-related neurapraxia compared with a duration of <5 minutes with MAP <55 mm Hg (hazard ratio, 3.43; confidence interval, 1.445-8.148; P = 0.0052). Intraoperative MAP >80 mm Hg for a total duration of >55 minutes was an independent predictor associated with a lower incidence of neurapraxia compared with a total duration ≤55 minutes (hazard ratio, 0.341; confidence interval, 0.163-0.717; P = 0.0045). CONCLUSIONS: In this study, we identified the changes in intraoperative MAP as independent predictors associated with upper extremity position-related neurapraxia in the prone surrender position under general anesthesia.

Synthesis and structure of analogues for the Ni-Fe site in hydrogenase enzymes.

Dithiolate bridging Ni-Fe complexes [(dppe)Ni(II)(mu-SEt)(2)Fe(II)(CN)(2)(CO)(2)](6) and [(dppe)Ni(II)(mu-pdt)Fe(II)(CN)(2)(CO)(2)] [dppe = 1,2-bis(diphenylphosphino)ethane and pdt = 1,3-propanedithiolate] have been synthesized and structurally characterized as structural analogues of the active site of Ni-Fe hydrogenase enzymes. The synthesis starts from key intermediate fac-[Fe(CN)(2)(CO)(3)I](-). [(dppe)Ni(II)(mu-SEt)(2)Fe(II)(CN)(2)(CO)(2)](6), which features a near-planar diethanethiolate-bridged Ni-Fe rhomb, and the arrangement of 2CN(-) ligands is cis to each other. In contrast, [(dppe)Ni(II)(mu-pdt)Fe(II)(CN)(2)(CO)(2)] shows a much more folded NiS(2)Fe rhomb, a short Ni-Fe distance, trans 2CN(-) ligands, and a semibridging CN(-) between Ni and Fe.

[FeIII(SR)4]1- complexes can be synthesized by the direct reaction of thiolates with FeCl3.

It is shown that the previously characterized [Fe(III)(SR)(4)](1-) (R=Et, i-Pr, Ph) complexes can be synthesized by the direct reaction of 4equiv. of LiSR with FeCl(3) in DMF solution. [Fe(III)(SR)(4)](1-) complexes are synthetic analogs for the [Fe(III)(S-Cys)(4)] center in rubredoxin proteins.

Electronic structure and FeNO conformation of nonheme iron-thiolate-NO complexes: an experimental and DFT study.

Reactions of NO and CO with Fe(II) complexes of the tripodal trithiolate ligands NS3 and PS3* yield trigonal-bipyramidal (TBP) complexes with varying redox states and reactivity patterns with respect to dissociation of the diatomic ligand. The previously reported four-coordinate [Fe(II)(NS3)](-) complex reacts irreversibly with NO gas to yield the S = 3/2 {FeNO}(7) [Fe(NS3)(NO)](-) anion, isolated as the Me(4)N(+) salt. In contrast, the reaction of NO with the species generated by the reaction of FeCl(2) with Li(3)PS3* gives a high yield of the neutral, TBP, S = 1 complex, [Fe(PS3*)(NO)], the first example of a paramagnetic {FeNO}(6) complex. X-ray crystallographic analyses show that both [Fe(NS3)(NO)](-) and [Fe(PS3*)(NO)] feature short Fe-N(NO) distances, 1.756(6) and 1.676(3) A, respectively. However, whereas [Fe(NS3)(NO)]- exhibits a distinctly bent FeNO angle and a chiral pinwheel conformation of the NS3 ligand, [Fe(PS3*)(NO)] has nearly C(3v) local symmetry and a linear FeNO unit. The S = 1 [Fe(II)(PS3)L] complexes, where L = 1-MeIm, CN(-), CO, and NO(+), exhibit a pronounced lengthening of the Fe-P distances along the series, the values being 2.101(2), 2.142(1), 2.165(7), and 2.240(1) A, respectively. This order correlates with the pi-backbonding ability of the fifth ligand L. The cyclic voltammogram of the [Fe(NS3)(NO)](-) anion shows an irreversible oxidation at +0.394 V (vs SCE), apparently with loss of NO, when scanned anodically in DMF. In contrast, [Fe(PS3*)(NO)] exhibits a reversible {FeNO}(6)/{FeNO}(7) couple at a low potential of -0.127 V. Qualitatively consistent with these electrochemical findings, DFT (PW91/STO-TZP) calculations predict a substantially lower gas-phase adiabatic ionization potential for the [Fe(PS3)(NO)](-) anion (2.06 eV) than for [Fe(NS3)(NO)](-) (2.55 eV). The greater instability of the {FeNO}(7) state with the PS3* ligand results from a stronger antibonding interaction involving the metal d(z(2)) orbital and the phosphine lone pair than the analogous orbital interaction in the NS3 case. The antibonding interaction involving the NS3 amine lone pair affords a relatively "stereochemically active" dz2 electron, the z direction being roughly along the Fe-N(NO) vector. As a result, the {FeNO}(7) unit is substantially bent. By contrast, the lack of a trans ligand in [Fe(S(t)Bu)3(NO)](-), a rare example of a tetrahedral {FeNO}(7) complex, results in a "stereochemically inactive" d(z(2)) orbital and an essentially linear FeNO unit.

The use of somatosensory evoked potentials to determine the relationship between patient positioning and impending upper extremity nerve injury during spine surgery: a retrospective analysis.

Somatosensory evoked potential (SSEP) monitoring is used to prevent nerve damage in spine surgery and to detect changes in upper extremity nerve function. Upper extremity SSEP conduction changes may indicate impending nerve injury. We investigated the effect of operative positioning on upper extremity nerve function retrospectively in 1000 consecutive spine surgeries that used SSEP monitoring. The vast majority (92%) of upper extremity SSEP changes were reversed by modifying the arm position and were therefore classified as position-related. The incidence of position-related upper extremity SSEP changes was calculated and compared for five different surgical positions: supine arms out, supine arms tucked, lateral decubitus position, prone arms tucked, and the prone "superman" position. The overall incidence of position-related upper extremity SSEP changes was 6.1%. The lateral decubitus position (7.5%) and prone superman position (7.0%) had a significantly more frequent incidence of position-related upper extremity SSEP changes (P < 0.0001, Z-test for Poisson counts) compared with other positions (1.8%-3.2%). No patient with a reversible SSEP change developed a new postoperative deficit in the affected extremity. SSEP monitoring is of value in identifying and reversing impending upper extremity peripheral nerve injury.

Further study of the reaction of Fe2+ with CN-: synthesis and characterization of cis and trans [FeII,III(CN)4L2]n- complexes.

The reaction of Fe2+ with CN-, which was first performed in 1704, has been used to synthesize a new series of basic [FeII,III(CN)4L2]n- complexes, where L is a monodentate ligand. trans-Na2[FeII(CN)4(DMSO)2] and cis-[NEt4]2[FeII(CN)4(pyridine)2] are synthesized by the direct reaction of FeCl2 with 4 equiv of CN- in DMSO or pyridine. Air oxidation of the latter compound gives cis-[NEt4][FeIII(CN)4(pyridine)2]. The non-cyanide ligands in these complexes undergo facile ligand exchange reactions with solvent. Reaction of cis-[NEt4]2[FeII(CN)4(pyridine)2] with CO at room temperature gives trans-[NEt4]2[FeII(CN)4(pyridine)(CO)].

Two-dimensional materials based on trans-[FeII(CN)4(CO)2]2- building blocks; first structural evidence for a hydrated metal carbonyl ligation.

Analogues to the Hofmann-type clathrates have been characterized using trans-[FeII(CN)4(CO)2]2- as the building blocks.

fac-[Fe(II)(CN)(3)(CO)(3)](-) and cis-[Fe(II)(CN)(4)(CO)(2)](2)(-): new members of the class of [Fe(II)(CN)(x)(CO)(y)] compounds.

The reaction of Fe(CO)(4)I(2) with NaCN or KCN in methanol gives M[Fe(II)(CN)(3)(CO)(3)] (M = Na, K), which can be converted to [Ph(4)E][Fe(II)(CN)(3)(CO)(3)] (E = P, As). The structure of the fac-[Fe(II)(CN)(3)(CO)(3)](-) (1) anion was established by the X-ray crystal structures of K-1 and [Ph(4)As]-1.H(2)O. Compound 1 has also been characterized by IR, Raman, and (13)C NMR. The coupling of the CO and CN stretching modes in the vibrational spectra of 1 have been analyzed. The reaction of Na-1 with NaCN gives Na(2) cis-[Fe(II)(CN)(4)(CO)(2)] (Na-2), which has been structurally characterized as [Ph(4)P][Et(4)N]-2. Compounds 1 and 2 are additional members of the series of compounds of general formula [Fe(II)(CN)((6-x))(CO)(x)](x-4). [Fe(CN)(x)(CO)(y)] compounds are of interest due to the occurrence of such coordination modes in hydrogenase enzymes.

trans-[Fe(CN)4 (CO)2 ]2- , a 21st Century [Fe(CN)(CO)] Compound.

In 1887, more than a century after the synthesis of [FeII (CN)6 ]4- , the complex [FeII (CN)5 (CO)]3- , in which a CN- ligand is replaced by CO, was reported. It has taken an additional century for the synthesis of the complex in which a second CN- ligand is substituted by CO: trans-[FeII (CN)4 (CO)2 ]2- (structure shown). Remarkably, this anion is prepared by the simple reaction of FeCl2 with NaCN and CO in water. [Fe(CN)x (CO)y ] complexes are of interest as models for the active site of hydrogenase enzymes.

Single-Crystal, Solid-State, and Solution (113)Cd and (77)Se NMR and X-ray Single-Crystal Study of a [Cd(SeR)(2)(N-donor)(2)] Complex.

[Cd(Se-2,4,6-i-Pr(3)-C(6)H(2))(2)(bpy)] (1) has been characterized by X-ray crystallography and studied by solution and solid-state (113)Cd and (77)Se NMR to serve as an analog for biologically occurring [M(S-Cys)(2)(His)(2)] centers. The unit cell parameters for 1 are as follows: a = 21.99(2) Å, b = 21.43(4) Å, c = 16.72(3) Å, V = 7881.3(4) Å(3), Z = 8, orthorhombic space group, Pccn. Two chemically inequivalent cadmiums and seleniums are found per unit cell. The principal values of the cadmium chemical shift tensors are (delta(11) = 752 ppm, delta(22) = 570 ppm, delta(33) = 93 ppm) and (delta(11)= 733 ppm, delta(22) = 547 ppm, delta(33) = 100 ppm) with respect to 0.1 M aq. Cd(ClO(4))(2). Those for selenium are (delta(11) = -950 ppm, delta(22) = -1040 ppm, delta(33) = -1599 ppm) and (delta(11) = -933 ppm, delta(22) = -1069 ppm, delta(33) = -1586 ppm) with respect to solid (NH(4))(2)SeO(4). The orientation of the cadmium chemical shift tensor is similar to that of the previously published sulfur analog.