Biomedical subjects

Michael J Black

Publications and source records attributed to Michael J Black.

5 recordsLinked to original sources

PubMed2006

Local/cervical block anesthesia versus general anesthesia for minimally invasive parathyroidectomy: what are the advantages?

BACKGROUND: Minimally invasive parathyroidectomy (MIP) under local/cervical block anesthesia (LA) is safe and effective for patients with primary hyperparathyroidism (HPT). Advantages of LA versus general anesthesia (GA) for these focused procedures have not been clearly demonstrated. METHODS: Between 3/01 and 6/04, 177 consecutive patients with primary HPT and positive localization studies underwent MIP. Seventy-three (41%) had surgery under LA while 104 (59%) had GA. Primary endpoints were IV narcotic use, anti-emetic use, nausea, vomiting, and post-operative pain. RESULTS: Patients who had parathyroidectomy under LA were older (64 +/- 2 vs. 57 +/- 2 years, P = 0.001). Cure and complication rates were identical between the two groups. Patients who had parathyroidectomy under LA required less IV narcotic pain mediation (mean morphine equivalents 11.4 +/- 1.3 mg vs. 22.5 +/- 1.1 mg; P < 0.001) compared to GA patients. The LA patients had better pain control as shown by lower post-operative peak pain scores (2.9 +/- 0.3 vs. 5.0 +/- 0.4; P < 0.001) and lower overall pain scores (mean 1.9 +/- 0.2 vs. 3.1 +/- 0.2; P < 0.001). The LA group required fewer anti-emetic medications compared to the GA patients (mean 0.4 +/- 0.1 vs. 1.7 +/- 0.1 doses; P < 0.001). Fewer LA patients experienced post-operative nausea (16% vs. 49%; P < 0.001), and vomiting (7% vs. 24%; P = 0.002). Length of stay was similar between the groups (0.4 +/- 0 vs. 0.3 +/- 0; P = 0.22). CONCLUSIONS: In this study the choice of anesthesia did not affect surgical cure rate, morbidity, or length of stay. LA was associated with significantly lower post-operative pain, nausea, and vomiting. LA appears to offer specific advantages more than GA for patients undergoing MIP.

Anesthesia, General↗

PubMed2006

Bayesian population decoding of motor cortical activity using a Kalman filter.

Effective neural motor prostheses require a method for decoding neural activity representing desired movement. In particular, the accurate reconstruction of a continuous motion signal is necessary for the control of devices such as computer cursors, robots, or a patient's own paralyzed limbs. For such applications, we developed a real-time system that uses Bayesian inference techniques to estimate hand motion from the firing rates of multiple neurons. In this study, we used recordings that were previously made in the arm area of primary motor cortex in awake behaving monkeys using a chronically implanted multielectrode microarray. Bayesian inference involves computing the posterior probability of the hand motion conditioned on a sequence of observed firing rates; this is formulated in terms of the product of a likelihood and a prior. The likelihood term models the probability of firing rates given a particular hand motion. We found that a linear gaussian model could be used to approximate this likelihood and could be readily learned from a small amount of training data. The prior term defines a probabilistic model of hand kinematics and was also taken to be a linear gaussian model. Decoding was performed using a Kalman filter, which gives an efficient recursive method for Bayesian inference when the likelihood and prior are linear and gaussian. In off-line experiments, the Kalman filter reconstructions of hand trajectory were more accurate than previously reported results. The resulting decoding algorithm provides a principled probabilistic model of motor-cortical coding, decodes hand motion in real time, provides an estimate of uncertainty, and is straightforward to implement. Additionally the formulation unifies and extends previous models of neural coding while providing insights into the motor-cortical code.

Action Potentials↗

PubMed2004

Modeling and decoding motor cortical activity using a switching Kalman filter.

We present a switching Kalman filter model for the real-time inference of hand kinematics from a population of motor cortical neurons. Firing rates are modeled as a Gaussian mixture where the mean of each Gaussian component is a linear function of hand kinematics. A "hidden state" models the probability of each mixture component and evolves over time in a Markov chain. The model generalizes previous encoding and decoding methods, addresses the non-Gaussian nature of firing rates, and can cope with crudely sorted neural data common in on-line prosthetic applications.

Action Potentials↗

PubMed2004

On the variability of manual spike sorting.

The analysis of action potentials, or "spikes," is central to systems neuroscience research. Spikes are typically identified from raw waveforms manually for off-line analysis or automatically by human-configured algorithms for on-line applications. The variability of manual spike "sorting" is studied and its implications for neural prostheses discussed. Waveforms were recorded using a micro-electrode array and were used to construct a statistically similar synthetic dataset. Results showed wide variability in the number of neurons and spikes detected in real data. Additionally, average error rates of 23% false positive and 30% false negative were found for synthetic data.

Action Potentials↗

PubMed2002

Improved survival in resected biliary malignancies.

BACKGROUND: For many years the prognosis for patients with biliary malignancies has been poor. However, recent advances in radiology and laparoscopy have improved staging, and active biliary stent management may improve outcome in these patients. In the past the goal with surgery was to excise all gross tumor. Now, the surgical goal is to achieve negative microscopic margins even if a major hepatic resection is required. Similarly, chemotherapy or radiation was frequently given in isolation, but chemoradiation has become the standard. Therefore, the aim of this analysis was to determine whether survival has improved with better staging, active stent management, more aggressive surgery, and chemoradiation. METHODS: From 1990 through 2001, 140 patients with biliary malignancies were treated at the Medical College of Wisconsin. One hundred eleven malignancies were cholangiocarcinomas (intrahepatic, 22%; perihilar, 65%; and distal, 13%), and 29 were gallbladder (GB) cancers. Eighty-six of the 140 patients (61%) underwent exploration (intrahepatic, 58%; perihilar, 57%; distal, 67%, and GB, 72%). Forty-four of these 86 patients (51%) underwent resection (intrahepatic, 64%; perihilar, 41%; distal, 70%; and GB, 52%). Chemoradiation with confocal radiation, 5-fluorouracil, and gemcitabine was used more frequently in the patients resected since 1998. RESULTS: Thirty-day operative mortality was 4%. In the resected patients (n = 44) the 5-year actuarial survival was 31% and the median survival was 27.8 months. Patients resected between 1998 and 2001 (n = 25) had a median survival longer than 44 months with a 3-year actuarial survival of 70% as compared to patients resected between 1990 and 1997 (n = 19), who had a median survival of 13 months and a 3-year actuarial survival of 21% (P <.01). CONCLUSIONS: These data suggest that (1) approximately one third of patients with biliary malignancies have resectable disease and (2) surgery in carefully selected patients with adjuvant chemoradiation has improved survival in resected patients. We suspect that a combination of improved staging, active biliary stenting, safe but extensive surgery to obtain negative margins, and newer techniques for chemoradiation have resulted in improved outcomes for patients with biliary malignancies.

Aged↗