Pressure-Immobilization Delays Mortality and Increases Intra-compartmental Pressure after Artificial Intramuscular Rattlesnake Envenomation in a Porcine Model

The California Journal of Emergency Medicine III:3, Jul-Sep 2002 page 48 Does the Addition of Parenteral Opiate Pre-Medication Increase Risk of Complications when combined with Methohexital for Procedural Moderate Sedation in the ED? Austin T, Vilke GM, Nyheim E, Kelly D, Chan TC Objectives: The goal of this study was to determine if the addition of parenteral opiate medications in combina- tion with methohexital for moderate/procedural sedation in the ED increases the risk of respiratory or cardiovascu- lar complications. Methods: We conducted a review of an existing single ED database of all patients who underwent moderate and procedural sedation in which methohexital was adminis- tered over a 2-year period. This database included data on patient demographics, procedure, sedation medications, pre-, intra-, and post-procedure vitals signs and monitor- ing changes, procedural success, complications and man- agement. Patients were stratified into 2 groups: those who were pre-medicated with parenteral opiates and those who were not. Significant respiratory and cardiovascular ab- normalities and complications were defined aprior to data collection and analysis. Power analysis determined that 108 cases were needed to detect a 25% increase in com- plication rates. Statistical analysis was performed using Fisher’s exact with p<0.05 considered significant (STATA Results: During the study period, there were 114 pa- tients who received methohexital, of whom 65 received parenteral opiate pre-medication (primarily morphine and fentanyl) and 49 did not. Overall rate of respiratory or cardiovascular complications was 15.9% with no signifi- cant difference between those who received opiate pre- medication and those who did not (18.7% vs. 11.0% re- spectively, p=.20). All complications were transient and managed without any long-term sequelae. Overall proce- dural success was 81% with no difference between the 2 groups (p=.50). Conclusions: In this study, the addition of parenteral opiate pre-medication with methohexital for moderate pro- cedural sedation in the ED did not result in any increase in respiratory or cardiovascular complications nor decrease in procedural success. These findings need further valida- tion with a larger, randomized study. Pressure-Immobilization Delays Mortality and Increases Intra-compartmental Pressure after Artificial Intramuscular Rattlesnake Envenomation in a Porcine Model Bush SP, Green SM, Laack TA, Hayes WK, Cardwell MD, Tanen DA Objectives: To determine if pressure-immobilization (PI) delays mortality and/or elevates intracompartmental pressure after artificial, intramus- cular Crotalus atrox envenomation in a porcine model. Methods: We prospectively studied 20 pigs using a randomized, controlled design. After the pigs were anesthetized, Crotalus atrox venom (20 mg/kg) was injected with a 22-gauge needle 10 mm deep into the tibialis anterior muscle of the hind leg. Pigs were ran- domized to receive either PI (applied one minute fol- lowing envenomation and left in place for the duration of the experiment) or no PI. We measured time to mortality; intracompartmental pressure prior to venom injection and at 2 hours following injection; and leg circumference at a standardized ocation prior to in- jection and immediately after mortality. We compared the increase in intracompartmental pressures and leg circumference using the unpaired Student t test. Du- ration of survival was compared using Kaplan-Meier survival analysis techniques. Results: The dose of venom resulted in 100% mor- tality. The mean survival times (minutes + SD) were 189 + 33 with PI and 155 + 23 without. The effect size (the difference between the 2 groups) was 34 minutes (95% CI = 6 to 62, P = 0.021). The mean intracompartmental pressures (mmHg + SD) were 67 + 13 with PI and 24 + 5 without (effect size: 43 mmHg, 95% CI = 32 to 53, P < 0.0005). The mean circum- ferences (cm + SD) were 14.3 + 0.8 with PI and 19.1 + 1.0 without (effect size: –4.8 cm, 95% CI = -5.7 to –3.9, P < 0.0005). Conclusions: PI resulted in significantly longer sur- vival, less swelling, and higher intracompartmental pressures.