Biomedical subjects

Mark S Wallace

Publications and source records attributed to Mark S Wallace.

23 records · Page 2Linked to original sources

PubMed2002

Tutorials in clinical research: part V: outcomes research.

OBJECTIVES: This is the fifth in a series of sequential "Tutorials in Clinical Research." The objective of the present report is to give the reader a broad overview of the field of outcomes research. This summary is intended to enable the reader to understand outcomes research methodology and to start the design of an outcomes research study. STUDY DESIGN: Tutorial. METHODS: The authors developed the report from available materials and refined it to be concise but complete for use by the practicing clinician. RESULTS: We describe the basic steps of record-based and patient-based outcomes research, including development of a staging system, identification of comorbid conditions, and creation or identification of an outcomes instrument. CONCLUSION: Outcomes research is a unique methodology that uses patient-based outcomes to assess the effectiveness of medical treatment.

Evidence-Based Medicine↗

PubMed2002

Tutorials in clinical research, part VI: descriptive statistics.

OBJECTIVES: This is the sixth in a series of Tutorials in Clinical Research. The objectives of this tutorial are to produce a brief, step-by-step, user-friendly atlas with clinical scenarios and illustrative examples to serve as ready references and, it is hoped, to open an inviting door to understanding statistics. STUDY DESIGN: Tutorial. METHODS: The authors met weekly for 6 months discussing clinical research articles and the applied statistics. Liberal use of reference texts and discussion focused on constructing a tutorial that is factual as well as easy to read and understand. RESULTS: The tutorial is organized into five sections: Overview, Key to Descriptive Summaries, Steps in Summarizing Descriptive Data, Understanding the Summaries of Specific Data Types, and Understanding Scope or Dispersion of Data. CONCLUSIONS: Assessing the validity of medical studies requires a working knowledge of statistics; however, obtaining this knowledge need not be beyond the ability of the busy surgeon. Desire is the only limiting factor. We have tried to construct an accurate, basic, easy-to-read-and-apply introduction to the task of summarizing the characteristics of a single variable. This is known as descriptive statistics.

Data Interpretation, Statistical↗

PubMed2002

Concentration-effect relationships for intravenous alfentanil and ketamine infusions in human volunteers: effects on acute thresholds and capsaicin-evoked hyperpathia.

The authors have extended preclinical studies on pain to human volunteers by examining the effects of intravenous alfentanil and ketamine on acute sensory thresholds andfacilitated processing induced by intradermal capsaicin. Eleven healthy subjects received targeted plasma concentrations of alfentanil, ketamine, and placebo followed by neurosensory testing (thermal and von Frey hair thresholds). After completing the tests at the highest plasma level, intradermal capsaicin was injected into the volar aspect of the left forearm, and the flare response and hyperalgesia to von Frey hair, stroking, and heat were assessed. Alfentanil significantly elevated cool and warm thresholds and decreased capsaicin-induced stroking hyperalgesia. Ketamine significantly decreased capsaicin-induced von Frey hair hyperalgesia. Both drugs resulted in a significant elevation of von Frey hair-induced pain thresholds and a decrease in capsaicin-induced pain. These studies suggest that experimental human pain models may be used to study analgesic pharmacology and may serve as important methods for defining the analgesic efficacy of drugs in phase I clinical trials.

Adult↗

PubMed1996

Computer-controlled lidocaine infusion for the evaluation of neuropathic pain after peripheral nerve injury.

BACKGROUND: Systemic lidocaine has been reported to be effective in treating several neuropathic pain syndromes. Few reports relate plasma lidocaine concentration to analgesia and the available studies have been complicated by labile plasma lidocaine concentrations. We used a computer-controlled infusion pump (CCIP) to target and maintain stable plasma lidocaine concentrations and study the effect of intravenous lidocaine on (1) pain scores, (2) current perception thresholds, (3) side effects, and (4) pain distribution in patients suffering from peripheral nerve injury pain. METHODS: This study used a randomized double-blind placebo-controlled design. Eleven patients suffering from neuropathic pain after peripheral nerve injury received both a lidocaine and saline infusion in separate study sessions. The order of the study sessions was randomized and separated from each other by 1 week. The CCIP was programmed to target plasma lidocaine concentrations of 0.5, 1, 1.5, 2, and 2.5 micrograms/ml, each held for 10 min. Pain scores and pain distribution were assessed in the painful area, and electrical current perception thresholds (CPT) of the ring finger were measured using a cutaneous perception threshold neurometer (Neurometer CPT, Neurotron, Baltimore, MD). Side effects were recorded at fixed intervals. Plasma lidocaine concentrations were measured at 4 and 9 min after each step increase in infusion and correlated with the observed effects. RESULTS: Saline infusion had no effect. However, with lidocaine there was a significant plasma concentration-dependent decrease in pain scores starting at 1.5 micrograms/ml. This effect typically corresponded with a decrease in the size of the receptive field to which the pain was referred. For the electrical stimulus, there was no significant effect on cutaneous perception at 2000-Hz stimulation at the highest concentration examined; however, there was a significant increase in thresholds at 250-Hz (starting at 1.5 micrograms/ml) and 5-Hz (starting at 1.0 micrograms/ml) stimulation. There were no serious side effects. In all, 54.5% of patients reported lightheadedness (average plasma lidocaine concentration: 1.5 micrograms/ml) and one patient reported nausea (2.3 micrograms/ml). DISCUSSION: The computer-controlled delivery of intravenous lidocaine results in relatively stable plasma concentrations which allows a more thorough evaluation of the relationship between plasma concentration and patient response. This administration methodology for intravenous lidocaine may prove to be a valuable clinical and research tool.

Adult↗

PubMedDate not supplied

Postdelivery of alfentanil and ketamine has no effect on intradermal capsaicin-induced pain and hyperalgesia.

OBJECTIVE: The predelivery of intravenous alfentanil (a mu opioid agonist) and ketamine (an -methyl d-aspartate antagonist) has recently been shown to decrease the secondary hyperalgesia induced by intradermal capsaicin. The focus of this study was to determine the effects of the postdelivery of intravenous alfentanil and ketamine on intradermal capsaicin-induced secondary hyperalgesia. DESIGN: Double-blind, placebo-controlled, randomized, crossover study. Five minutes after an intradermal capsaicin injection, alfentanil and ketamine infusions were administered for a target plasma concentration of 75 ng/ml for alfentanil and 150 ng/ml for ketamine or placebo equivalent using a computer-controlled infusion pump and maintained for the remainder of the study. The investigator recorded the magnitude of the pain score at the time of injection and at 5-minute intervals. Fifteen minutes after the intradermal capsaicin injection, the region of secondary hyperalgesia and flare response was determined. RESULTS: Alfentanil and ketamine plasma levels targeted after injection of intradermal capsaicin had no significant effect on pain scores, flare response, or secondary hyperalgesia. CONCLUSIONS: Consistent with animal studies on preemptive analgesia, this study demonstrates that alfentanil and ketamine have a differential effect when delivered before and after a painful stimulus. Because of the differential effect seen, future studies on the pharmacology of human experimental pain should evaluate both predrug and postdrug delivery.

Adult↗