Epidural Steroid Injection Complicated by Intrathecal Entry, Pneumocephalus, and Chemical Meningitis.

BACKGROUND: Epidural steroid injections are frequently used to treat back and extremity pain. The procedure is generally safe, with a low rate of adverse events, including intrathecal entry, pneumocephalus, and chemical meningitis. CASE REPORT: We report a case of a 45-year-old woman who presented to the emergency department (ED) with headache, nausea, vomiting, and photophobia after a lumbar epidural steroid injection. She was afebrile and had an elevated white blood cell count. A non-contrast computed tomography scan of the head revealed pneumocephalus within the subarachnoid space and lateral ventricles. The patient was admitted to the ED observation unit for pain control and subsequently developed a marked leukocytosis and worsening meningismus. A lumbar puncture was performed yielding cerebrospinal fluid (CSF) consistent with meningitis (1,000 total nucleated cells, 89% neutrophils, 85 mg/dL total protein, and no red blood cells). Gram stain revealed no bacteria. The patient was admitted on empiric vancomycin and ceftriaxone. Antibiotics were discontinued at 48 h when CSF cultures remained negative and the patient was clinically asymptomatic. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: Emergency physicians should consider intrathecal entry and pneumocephalus in patients who present with a headache after an epidural intervention. The management of pneumocephalus includes supportive therapies, appropriate positioning, and supplemental oxygen. These symptoms can be accompanied by fever, leukocytosis, and markedly inflammatory CSF findings consistent with bacterial or chemical meningitis. Empiric treatment with broad-spectrum antibiotics should be initiated until CSF culture results are available.

Analysis of a pentacoordinate iron dicarbonyl as synthetic analogue of the Hmd or mono-iron hydrogenase active site.

Pentacoordinate iron dicarbonyls, (NS)Fe(CO)(2)P (NS=2-amidothiophenylate, P=PCy(3) (4), PPh(3), (5), and P(OEt)(3) (6)) were prepared as potential biomimetics of the active site of the mono-iron hydrogenase, [Fe]-H(2)ase. Full characterization including X-ray diffraction, density functional theory (DFT) computations, and Mössbauer studies for complexes 5 and 6 find that, despite similar infrared v(CO) pattern and absorption frequencies as the active site of the [Fe]-H(2)ase, the geometrical distortions towards trigonal bipyramidal, the negative isomer shift parameters, and the differences in CO-uptake reactivity are due to the "non-innocence" of the NS ligand. Ligand-based protonation with a strong acid, HBF(4).Et(2)O, interrupted the extensive pi-delocalization over Fe and NS ligand of complex 4 and switched on CO uptake (1 bar) to form a CO adduct, mer-[(H-NS)Fe(CO)(3)(PCy(3))](+) or 4(CO)-H(+). The extrinsic CO is reversibly removed on deprotonation with Et(3)N to regenerate complex 4. In a (13)CO atmosphere, concomitant CO uptake by 4-H(+) and exchange with intrinsic CO groups provide a facile route to (13)C-labeled 4(CO)-H(+) and, upon deprotonation, (13)C-labeled complex 4. DFT calculations show substantial Fe character in the LUMO of 4-H(+) typical of the d(6) Fe(II) in a regular square-pyramidal geometry. Thus, the Lewis acidity of 4-H(+) makes it amenable for CO binding, whereas the dianionic NS ligand renders the iron center of 4 insufficiently electrophilic and largely of Fe(I) character.

Synthesis and Mössbauer characterization of octahedral iron(II) carbonyl complexes FeI2(CO)3L and FeI2(CO)2L2: developing models of the [Fe]-H(2)ase active site.

A series of mono- and disubstituted complexes, FeI(2)(CO)(x)L(4-x), x = 2 or 3, is conveniently accessed from simple mixing of N-heterocyclic carbenes, phosphines, and aromatic amines with FeI(2)(CO)(4), first reported by Hieber in 1928. The highly light sensitive complexes yield to crystallization and X-ray diffraction studies for six complexes showing them to be rudimentary structural models of the monoiron hydrogenase, [Fe]-H(2)ase or Hmd, active site in native (Fe(II)(CO)(2)) or CO-inhibited (Fe(II)(CO)(3)) states. Diatomic ligand (nu(CO)) vibrational and Mossbauer spectroscopies are related to those reported for the Hmd active site. The importance of a serial approach for relating such parameters in model compounds to low spin Fe(II) in the diverse ligation of enzyme active sites is stressed.