Acute cervical spinal cord injury and extubation failure: A systematic review and meta-analysis.

PURPOSE: Respiratory complications are the most significant cause of morbidity and mortality in acute cervical spinal cord injury (CSCI). The prevalence of extubation failure (EF) and factors associated with it are unclear. This research aimed to systematically synthesise and pool literature describing EF and associated risk factors in acute CSCI. METHODS: A systematic review was performed using medical literature analysis and retrieval system online, cummulative index of nursing and allied health literature, excerpta medica dataBASE, and Cochrane library. Articles were screened using the preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines. A proportion meta-analysis was conducted to pool rates of EF. Odds ratios and weighted mean differences were calculated to evaluate risk factors. The R statistical software package was used. RESULTS: Of the 347 articles that were identified, six articles satisfied the inclusion criteria (387 participants). The pooled EF rate was 20.25% (10.13-36.38%). Type of CSCI was the only statistically significant risk factor. The odds of EF occurring were 2.76 [95% confidence interval (CI): 1.14; 6.70] times greater for complete CSCI than for incomplete CSCI. CONCLUSIONS: One in five patients with acute cervical SCI fails extubation. The odds of EF occurring are almost three times greater in complete CSCI. Future research should aim to improve standard data sets and prospective evaluation of adjuvant therapy in the peri-extubation period.

The anatomic rationale for transforaminal endoscopic interbody fusion: a cadaveric analysis.

OBJECTIVE The authors describe a cadaveric analysis to determine the ideal dimensions and trajectory for considering endoscopic transforaminal interbody implantation. METHODS The soft tissues of 8 human cadavers were removed from L-1 to the sacrum, exposing the posterior bony elements. Facetectomies were performed bilaterally at each lumbar level with resection of the pars interarticularis, revealing the pedicles, nerve roots, and interbody disc space. Each level was digitally photographed with a marker for scale and evaluated with digital analysis software. The traversing and exiting nerve roots and pedicle margins were identified, and the distances between these structures and their relationships to the surrounding structures were documented. RESULTS The dimensions of 2 areas were measured: the working triangle and safe zone. The working triangle is the triangle between the exiting and traversing nerve roots above the superior margin of the inferior pedicle. The safe zone is the trapezoid bounded by the widths of the superior and inferior pedicles between the exiting and traversing nerve roots. The mean surface area for the working triangle was 1.83 cm(2), with L5-S1 having the largest area at 2.19 cm(2). The mean surface area of the safe zone was 1.19 cm(2), with L5-S1 having the largest area at 1.26 cm(2). At the medial border of the pedicle extending superiorly, there were no nerve structures within 1.19 cm at any level. On the lateral border of the pedicle, the exiting nerve root was closer superiorly, with the closest being 0.3 cm. CONCLUSIONS The working triangle is a relatively large area. The safe zone, just superior to the pedicle, is free of nerve structures. By utilizing the superior border of the pedicle, the disc space can be accessed within this safe zone without risk of injury to the nerves. A thorough understanding of foraminal anatomy is fundamental for considering how to safely access the disc space, thereby utilizing less invasive endoscopic techniques, and is an important first step in considering what shapes and sizes of interbody implants and retractors are feasible for use in the foramen.

Catalytic mechanism of the tryptophan synthase alpha(2)beta(2) complex. Effects of pH, isotopic substitution, and allosteric ligands.

The mechanism of the tryptophan synthase alpha(2)beta(2) complex from Salmonella typhimurium is explored by determining the effects of pH, of temperature, and of isotopic substitution on the pyridoxal phosphate-dependent reaction of L-serine with indole to form L-tryptophan. The pH dependence of the kinetic parameters indicates that three ionizing groups are involved in substrate binding and catalysis with pK(a)1 = 6.5, pK(a)2 = 7.3, and pK(a)3 = 8.2-9. A significant primary isotope effect (approximately 3.5) on V and V/K is observed at low pH (pH 7), but not at high pH (pH 9), indicating that the base that accepts the alpha-proton (betaLys-87) is protonated at low pH, slowing the abstraction of the alpha-proton and making this step at least partially rate-limiting. pK(a)2 is assigned to betaLys-87 on the basis of the kinetic isotope effect results and of the observation that the competitive inhibitors glycine and oxindolyl-L-alanine display single pK(i) values of 7.3. The residue with this pK(a) (betaLys-87) must be unprotonated for binding glycine or oxindolyl-L-alanine, and, by inference, L-serine. Investigations of the temperature dependence of the pK(a) values support the assignment of pK(a)2 to betaLys-87 and suggest that the ionizing residue with pK(a)1 could be a carboxylate, possibly betaAsp-305, and that the residue associated with a conformational change at pK(a)3 may be betaLys-167. The occurrence of a closed to open conformational conversion at high pH is supported by investigations of the effects of pH on reaction specificity and on the equilibrium distribution of enzyme-substrate intermediates.