Biomedical subjects

Mark Li

Publications and source records attributed to Mark Li.

3 recordsLinked to original sources

PubMed2006

Neurophysiological identification of position-induced neurologic injury during anterior cervical spine surgery.

This study was a retrospective review of 3,806 patients who underwent anterior cervical spine surgery with multi-modality neurophysiological monitoring consisting of transcranial electric motor evoked potentials, somatosensory evoked potentials and spontaneous electromyography between 1999-2003. The objectives of this study were twofold: (1) to evaluate the role of transcranial electric motor evoked potential tceMEP and ulnar nerve somatosensory evoked potential (SSEP) monitoring for identifying impending position-related stretch brachial plexopathy, peripheral nerve entrapment/compression or spinal cord compression and (2) to estimate the point-prevalence of impending neurologic injury secondary to surgical positioning effects. Sixty-nine of 3,806 patients (1.8% showed intraoperative evidence of impending neurologic injury secondary to positioning, prompting interventional repositioning of the patient. The brachial plexus was the site of evolving injury in 65% of these 69 cases. Impending brachial plexopathy was most commonly noted immediately following shoulder taping and the application of counter-traction. Brachial plexus stretch upon neck extension for optimal surgical access and visualization was second in frequency-of-occurrence. Evolving traction injury to the ulnar nerve attributed to tightly-wrapped or malpositioned arms was observed in 16% of alerted cases, whereas evolving spinal cord injury following neck extension accounted for an additional 19%. This study highlights the role of tceMEP and ulnar nerve SSEP monitoring for detecting emerging peripheral nerve injury secondary to positioning in preparation for and during anterior cervical spine surgery.

Adult↗

PubMed2004

Initial head computed tomographic scan characteristics have a linear relationship with initial intracranial pressure after trauma.

BACKGROUND: Despite current recommendations by the Brain Trauma Foundation regarding the placement of intracranial pressure (ICP) monitoring devices, advances in computed tomographic (CT) scan technology have led to the suggestion that increased ICP may be predicted by findings on admission head CT scan and that patients without such findings do not require such monitoring. A linear relationship exists between characteristics of admission head CT scan and initial ICP level, allowing for selective placement of ICP monitoring devices. METHODS: From 1997 to 2001, a retrospective review of patients admitted with a Glasgow Coma Scale (GCS) score < 8 and head CT scan who underwent ventriculostomy placement at our institution, was conducted. Patients undergoing craniotomy with evacuation of mass lesions before ventriculostomy placement were excluded. Age, sex, mechanism of injury, anoxia, osmotic treatment, presence of drugs/alcohol, initial mean arterial pressure, initial GCS score, and initial ICP were recorded. Initial head CT scans were reviewed independently by two neuroradiologists who were blinded to ICP measurements, neurosurgical treatment, patient outcome, and each other's interpretation. Initial CT scans were evaluated and scored on a 1 (normal) to 3 (abnormal) scale with respect to ventricle size, basilar cistern size, sulci size, degree of transfalcine herniation, and gray/white matter differentiation. Initial ICP readings and CT scan findings were compared to determine whether a significant linear relationship existed between the above CT scan findings and ICPs. Logistic and univariate linear regression were used to compare averaged radiologist score versus dichotomized ICP at baseline. RESULTS: Initial head CT scan characteristics show a linear relationship to baseline ICPs. These findings are associative, but are not uniformly predictive. CONCLUSION: Therefore, the current Brain Trauma Foundation recommendation of ICP monitoring in those patients presenting with a GCS score < 8 with an abnormal CT scan or a normal CT scan with age > 40 years, systolic blood pressure < 90 mm Hg, or exhibiting posturing should be followed.

Adolescent↗

PubMed2003

Tailoring structure-function and pharmacokinetic properties of single-chain Fv proteins by site-specific PEGylation.

The utility of single-chain Fv proteins as therapeutic agents would be realized if the circulating lives of these minimal antigen-binding polypeptides could be both prolonged and adjustable. We have developed a general strategy for creating tailored monoPEGylated single-chain antibodies. Free cysteine residues were engineered in an anti-TNF-alpha scFv at the C-terminus or within the linker segments of both scFv orientations, V(L)-linker-V(H) and V(H)-linker-V(L). High-level expression of 10 designed variant scFv proteins in Pichia pastoris allowed rapid purification. Optimization of site-specific conjugate preparation with 5, 20 and 40 kDa maleimide-PEG polymers was achieved and a comparison of the structural and functional properties of the scFv proteins and their PEGylated counterparts was performed. Peptide mapping and MALDI-TOF mass spectrometric analysis confirmed the unique attachment site for each PEG polymer. Independent biochemical and bioactivity analyses, including binding affinities and kinetics, antigenicity, flow cytometric profiling and cell cytotoxicity rescue, demonstrated that the functional activities of the 10 designed scFv conjugates are maintained, while scFv activity variations between these alternative assays can be correlated with conjugate and analytical designs. Pharmacokinetic studies of the PEGylated scFv in mice demonstrated up to 100-fold prolongation of circulating lives, in a range comparable to clinical antibodies.

Animals↗