Biomedical subjects

David B MacLeod

Publications and source records attributed to David B MacLeod.

4 recordsLinked to original sources

PubMed2005

Changes in hematocrit based on incremental blood sampling: mathematical models perform poorly.

PURPOSE: Excessive blood sampling, with its inherent risks, is of growing concern among clinicians. We performed this study to measure the changes in hematocrit (Hct) during a laboratory investigation where multiple blood samples are collected. The performance of a simple mathematical model, used in clinical practice to predict Hct changes, is evaluated. METHODS: Eight healthy male volunteers participated in this study. The equation Hct(f) = Hct(i)*(EBV-BL)/EBV is used to predict changes in Hct. Where Hct(f) and Hct(i) are, respectively, the final and initial Hct, EBV is the estimated blood volume and BL is the blood loss. RESULTS: Thirty-five pharmacokinetic samples per subject were collected totalling 314 mL of BL. The Hct decreased from 44.2% +/- 2.2% to 39.9% +/- 2.5% (P = 0.001). On average, model predictions tended to have a discrete tendency to underestimate the Hct changes (-0.5% points of bias). While the predictions of the Hct were very accurate in 50% of the subjects, the discrepancy of the Hct predictions was clinically significant in the other 50% of the subjects. CONCLUSION: Consistent with the model prediction, this study demonstrated a significant reduction in the Hct values in healthy subjects undergoing incremental phlebotomy. On average, the model successfully predicted the decrease in Hct. However, the inter- and intra-individual variabilities in the Hct changes are clinically significant. In clinical settings, which are not well controlled environments, the variability is likely to be greater and the clinical use of the model cannot replace the need to monitor the Hct.

Adult↗

PubMed2004

Dexmedetomidine infusion for sedation during fiberoptic intubation: a report of three cases.

We report three patients undergoing cervical spine surgery who required awake fiberoptic intubation, and in whom sedation was provided using a dexmedetomidine infusion. Dexmedetomidine was used to provide a moderate level of sedation without causing respiratory distress or hemodynamic instability during fiberoptic intubation. Conditions for intubation were acceptable in all three patients after co-administration of topical anesthesia. Dexmedetomidine may serve as a useful adjunct for this procedure. The anesthetic management and anesthetic implications of using dexmedetomidine infusions for awake fiberoptic intubation are discussed.

Adult↗

PubMed2003

A study of anesthetic drug utilization in different age groups.

STUDY OBJECTIVE: To determine anesthetic drug utilization in different age groups. DESIGN: Retrospective, automated, intraoperative database study. SETTING: Tertiary care medical center. MEASUREMENTS: 30,842 noncardiac general anesthesia case records between January 1991 and July 1997 were studied. We investigated the effect of age on anesthetic requirements for fentanyl (F), midazolam (M), thiopental sodium (T), propofol (P), isoflurane (I), and nitrous oxide (N). Because drugs are not given in isolation we looked at the most common drug combinations, IFNTM, IFNPM, INFT, and PFNM. Regression analyses on log-transformed drug dosages were used to test the significance of age on individual requirements. RESULTS: In each of the above anesthetic drug combinations, reduced doses of fentanyl, propofol, midazolam, thiopental, and isoflurane were used with increasing age. Fentanyl, propofol, thiopental, and isoflurane showed a 10%, 8%, 6%, and 4% reduction in dose per decade of age, respectively, from age of maximum dose to age 80 years. CONCLUSIONS: In clinical practice, increasing age results in decreased anesthetic drug administration. The mechanism of this observation needs to be determined.

Adult↗

PubMed2002

A new teaching model for resident training in regional anesthesia.

UNLABELLED: The adequacy of resident education in regional anesthesia is of national concern. A teaching model to improve resident training in regional anesthesia was instituted in the Anesthesiology Residency in 1996 at Duke University Health System. The key feature of the model was the use of a CA-3 resident in the preoperative area to perform regional anesthesia techniques. We assessed the success of the new model by comparing the data supplied by the Anesthesiology Residency to the Residency Review Committee for Anesthesiology for the training period July 1992-June 1995 (pre-model) and the training period July 1998-June 2001 (post-model). During the 3-yr training period, the pre-model CA-3 residents (n = 12) performed a cumulative total of 80 (58-105) peripheral nerve blocks (PNBs), 66 (59-74) spinal anesthetics, and 133 (127-142) epidural anesthetics. The CA-3 post-model residents (n = 10) performed 350 (237-408) PNBs, 107 (92-123) spinal anesthetics, and 233 (221-241) epidural anesthetics (P < 0.0001). All results are reported as median (interquartile range). We conclude that our new teaching model using our CA-3 residents as block residents in the preoperative area has increased their clinical exposure to PNBs. IMPLICATIONS: Inadequate exposure to peripheral nerve blocks has been a national problem. A teaching model instituted at Duke University Health System has resulted in a fourfold increase in exposure to peripheral nerve blocks compared with the national averages.

Anesthesia, Conduction↗