United States Army Rangers in Somalia: an analysis of combat casualties on an urban battlefield.

BACKGROUND: This study was undertaken to determined the differences in injury patterns between soldiers equipped with modern body armor in an urban environment compared with the soldiers of the Vietnam War. METHODS: From July 1998 to March 1999, data were collected for a retrospective analysis on all combat casualties sustained by United States military forces in Mogadishu, Somalia, on October 3 and 4, 1993. This was the largest and most recent urban battle involving United States ground forces since the Vietnam War. RESULTS: There were 125 combat casualties. Casualty distribution was similar to that of Vietnam; 11% died on the battlefield, 3% died after reaching a medical facility, 47% were evacuated, and 39% returned to duty. The incidence of bullet wounds in Somalia was higher than in Vietnam (55% vs. 30%), whereas there were fewer fragment injuries (31% vs. 48%). Blunt injury (12%) and burns (2%) caused the remaining injuries in Somalia. Fatal penetrating injuries in Somalia compared with Vietnam included wounds to the head and face (36% vs. 35%), neck (7% vs. 8%), thorax (14% vs. 39%), abdomen (14% vs. 7%), thoracoabdominal (7% vs. 2%), pelvis (14% vs. 2%), and extremities (7% vs. 7%). No missiles penetrated the solid armor plate protecting the combatants' anterior chests and upper abdomens. Most fatal penetrating injuries were caused by missiles entering through areas not protected by body armor, such as the face, neck, pelvis, and groin. Three patients with penetrating abdominal wounds died from exsanguination, and two of these three died after damage-control procedures. CONCLUSION: The incidence of fatal head wounds was similar to that in Vietnam in spite of modern Kevlar helmets. Body armor reduced the number of fatal penetrating chest injuries. Penetrating wounds to the unprotected face, groin, and pelvis caused significant mortality. These data may be used to design improved body armor.

A comparison of median frequency, spectral edge frequency, a frequency band power ratio, total power, and dominance shift in the determination of depth of anesthesia.

Five numerical descriptors were derived from the electroencephalogram (EEG), recorded, and processed (Tracor Nomad) during emergence from isoflurane-nitrous oxide anesthesia. The five descriptors (median frequency, spectral edge frequency-90%, total power, a frequency band power ratio, and the ratio of frontal to occipital power) were compared for their ability to predict imminent arousal. Arousal was defined as spontaneous movement, coughing or eye opening. All of the descriptors except the frontal-occipital power ratio underwent significant (P less than 0.05) changes between the initial recordings made intraoperatively during surgical stimulus under anesthesia and later recordings in the 40 s preceding arousal. A post hoc analysis was performed to identify the threshold value for each parameter that best served to predict imminent arousal. For median frequency, spectral edge frequency-90%, total power, and the frequency band power ratio, thresholds that predicted imminent arousal with sensitivities of 90% and specificities of 82-90% could be identified. The data indicate that, even in the favorable circumstances of the present study (uniform anesthetic technique, post hoC identification of thresholds), none of several previously popularized EEG descriptors (median frequency, spectral edge frequency-90%, total power, a frequency band power ratio) can serve as a completely reliable sole predictor of imminent arousal. As presently derived, these EEG descriptors at best provide trend information to be used in concert with other clinical signs of depth of anesthesia.

Continuous spinal anesthesia with hyperbaric bupivacaine: a dose-response analysis.

Continuous spinal anesthesia (CSA) with hyperbaric bupivacaine (0.75% bupivacaine in 8.25% dextrose and water) was administered to 27 adult males for transurethral endoscopic surgery. Patients were randomized to receive either 3.75, 7.5 or 10 mg hyperbaric bupivacaine in a double-blind fashion. A 20-gauge nylon catheter was inserted at the L3-4 interspace, via an 18-gauge Tuohy-Schliff needle, extending only 2 cm into the subarachnoid space. All patients were placed in the lithotomy position prior to administration of the hyperbaric bupivacaine. Sensory block was assessed by pinprick and perception of a 50-Hz tetanic stimulus at 5, 10 and 20 minutes, then every 20 minutes thereafter. Peak sensory and motor block were obtained by 20 minutes for all dose ranges. Peak sensory levels were T7.1, T5.6 and T3.9 for 3.75, 7.5 and 10 mg hyperbaric bupivacaine, respectively. Linear regression analysis demonstrated a significant correlation (r = -0.68) between peak sensory level and dose of bupivacaine. Peak sensory level as estimated by pinprick and 50-Hz tetanic stimulus showed excellent correlation (r = 0.99). The role of the subarachnoid catheter in the dispersion and distribution of bupivacaine within the subarachnoid space was studied in a model spinal canal system and compared with the distribution of bupivacaine administered via a standard 25-gauge spinal needle. No significant differences were found in the distribution of bupivacaine with either method of injection. The distribution of hyperbaric bupivacaine within the subarachnoid space appears to be related to baricity but is unrelated to administration via needle or catheter.