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Biomedical subjects

Mark A Warner

Publications and source records attributed to Mark A Warner.

6 recordsLinked to original sources
PubMed2004

Effect of lithotomy positions on strain of the obturator and lateral femoral cutaneous nerves.

The purpose of this study was to determine if various lithotomy positions increase strain on the obturator and lateral femoral cutaneous nerves in fresh adult cadavers. A static load cell was used to record strain changes of the obturator and lateral femoral cutaneous nerves in the pelvis and anterior thigh when the lower limbs were placed in three sets of positions of varying hip abduction and flexion. The means of the strain measurements, which were measured in grams in all positioning angles were compared to the baseline 0 degrees measurements. Analysis of variance was calculated for the differences. Flexion of the hip did not increase strain on either nerve. Abduction to 30 degrees or 45 degrees increased strain by more than 30 g on the obturator nerve (P < 0.05) but not the lateral femoral cutaneous nerve. The addition of 45 degrees or more of flexion to abduction negated the strain increase on the obturator nerves seen with abduction alone. Nerve strain >30 g has been associated consistently with nerve dysfunction, disrupting axonal transmission, and causing structural neural damage. Our findings suggest that concomitant hip flexion should be used when placing anesthetized patients in a lithotomy position that includes abduction of the lower limbs to >30 degrees to decrease the risk for perioperative neuropathy of the obturator nerve.

Aged↗
PubMed2002

Chiari I malformation in parturients.

STUDY OBJECTIVE: To assess complications of regional as well as general anesthesia in parturients with Chiari I malformation. DESIGN: Retrospective chart review. SETTING: Academic medical center. PATIENTS: All parturients in our institution who had the diagnosis of Chiari I malformation and delivered in our hospitals over a 50-year period. MAIN RESULTS: 12 parturients delivered 30 babies. Three deliveries were facilitated with general anesthesia. Nine deliveries were facilitated with central axis anesthesia, six with epidural anesthesia, two with a single injection of a spinal anesthetic, and one with a continuous spinal catheter. The patient who received a continuous spinal catheter developed a postdural puncture headache that resolved with an epidural blood patch. None of the patients who received general, spinal, or epidural anesthesia for their deliveries developed symptoms or had exacerbation of preexisting symptoms of Chiari I malformation. CONCLUSIONS: General anesthesia, as well as spinal and epidural anesthesia, appeared to be safe and effective in our series of vaginal or cesarean delivery patients. The small number of patients in our series does not negate the cautious recommendations of others, but suggests that general anesthesia, as well as spinal or epidural anesthesia, can be used safely and effectively in these patients.

Academic Medical Centers↗
PubMed2002

Perioperative visual changes.

BACKGROUND: The goal of this project was to describe the frequency and natural history of perioperative changes in vision. METHODS: The authors performed a prospective evaluation of changes in visual accommodation and acuity in adult patients undergoing various surgical procedures. Patients were evaluated preoperatively and at 1 and 3 days postoperatively. For patients who had persistent blurring of vision on the third postoperative day, surveillance was extended to 1.5 yr to determine how long the visual changes persisted and if the patients required eye-care provider attention for the condition. RESULTS: Twenty-eight of 671 patients (4.2%) reported new onset of blurred vision lasting at least 3 days after surgery. Seven of these 28 patients (1% of total) required either new corrective lens or changes in eyeglass or contact prescriptions because of persistent blurry vision. Most of the remaining patients reported resolution of blurry vision within 1 to 2 months. No significant risk factors for this problem were identified. CONCLUSIONS: In this surgical population, changes in visual acuity manifest primarily by blurred vision were reported at a surprisingly high frequency. For many of these patients, the blurring resolved within 2 months without complication, but 25% of patients who had blurred vision for 3 days or longer required visits to eye-care providers and either new corrective lens or changes in existing prescriptions.

Adult↗