Piper Wall

Tourniquets and Occlusion: The Pressure of Design

UNLABELLED Nerve injuries result from tourniquet pressure. The objective was to determine arterial occlusion and completion pressures with the 3.8-cm-wide windlass Combat Application Tourniquet (CAT) and the 10.4-cm-wide Stretch, Wrap, and Tuck Tourniquet (SWAT-T). METHODS Sixteen volunteers self-applied and had tourniquets applied to their thighs and arms (CAT and SWAT-T, random order, then blood pressure cuffs). RESULTS Occlusion (Doppler signal elimination) pressures were higher than predicted (p < 0.0001), highest with the CAT (p < 0.0001), and often lower than completion pressures (completion median, range: CAT 360, 147-745 mm Hg; SWAT-T 290, 136-449 mm Hg; cuff 184, 108-281 mm Hg). Three CAT thigh and 9 CAT arm completion pressures were >500 mm Hg. Pressure decreases and occlusion losses occurred over 1 minute (pressure decrease: CAT 44 ± 33 mm Hg; SWAT-T 6 ± 8 mm Hg; cuff 14 ± 19 mm Hg; p < 0.0001; loss/initially occluded: CAT 17 of 61, SWAT-T 5 of 61, cuff 40 of 64, p < 0.01). CAT pressures before turn did not have a clear relationship with turns to occlusion. CONCLUSIONS Limb circumference/tourniquet width occlusion pressure predictions are not good substitutes for measurements. The wider SWAT-T has lower occlusion and completion pressures than the CAT. Decreases in muscle tension lead to decreases in tourniquet pressure, especially with the nonelastic CAT, which can lead to occlusion loss.

Stretch and Wrap Style Tourniquet Effectiveness With Minimal Training

UNLABELLED The objective was to determine if proper application of the Stretch, Wrap, and Tuck Tourniquet (SWAT-T) would stop arterial flow and would occur with minimal training. METHODS Fifteen undergraduates watched a 19 second video three times, practiced twice, and applied the tourniquet to volunteers at 10 locations: 3 above the elbow or knee and 2 below. RESULTS Successful occlusion (60 second Doppler signal elimination) was more frequent than proper stretch (96 versus 75), more frequent on arms than legs (59 versus 37), and achieved before completed application (16 +/- 8 versus 33 +/- 8 seconds; each p < 0.05). Proper stretch (correct alteration of shapes printed on the tourniquet) was more frequent on legs than arms (30 versus 45; p <0.05). Applications were rated Easy (101), Challenging (37), Difficult (12) with discomfort None (53), Little (62), Moderate (34), Severe (1). The 8 appliers with <70% proper stretch rates received 10 minutes additional training and then retested at mid upper arm, mid-thigh, and below knee (24 applications) for improved proper stretch and occlusion (5 versus 18 and 10 versus 20; p < 0.01). CONCLUSIONS Proper application of the SWAT-T is easy and can stop extremity arterial flow but requires some training for many appliers.

Enalaprilat improves systemic cardiovascular parameters and mesenteric blood flow during hypotensive resuscitation from hemorrhagic shock in dogs.

Resuscitative interventions that improve mesenteric perfusion without causing instability in systemic arterial pressures may be helpful for improving trauma patient outcomes. Blocking angiotensin II formation with enalaprilat may be such an intervention. Two questions were addressed in this two-part study investigating resuscitation from hemorrhagic shock in dogs: Can systemic arterial pressures be maintained while administering a constant rate infusion of enalaprilat during resuscitation, and can enalaprilat improve cardiovascular status during resuscitation? Animals were hemorrhaged to a mean arterial pressure (MAP) of 40 to 45 mmHg for 30 min and then 30 to 35 mmHg for 30 min. Group I (n = 5) was resuscitated to a MAP 60 to 65 mmHg with enalaprilat (0.02 mg/kg/h). Group II was resuscitated to a MAP 40 to 45 mmHg with (n = 5) or without (n = 5) enalaprilat. Resuscitation in both groups consisted of intermittent intravenous lactated Ringers solution (60 mL/kg/h) to reach and maintain the target MAPs. Systemic arterial pressures were unaffected by enalaprilat during resuscitation in Group I, allowing us to proceed to the second study. During severely hypotensive resuscitation (Group II), systemic arterial pressures were also stable and enalaprilat administration was associated with increases (P ≤ 0.02) in cardiac index (+1.2 L/min/m2), stroke volume index (SVI) (+14.5 mL/m2), superior mesenteric artery flow (+80 mL/min), stroke work (+561 mmHg/mL/m2), and left ventricular power output (+55.7 mmHg/L/min/m2). Corresponding increases were not observed in controls. We conclude that administration of a constant rate infusion of enalaprilat during resuscitation can be accomplished without causing a hypotensive crisis. Since enalaprilat significantly improved cardiovascular status including mesenteric perfusion even during intentional hypotension, it has potential value for improving the treatment of trauma patients.

Cadmium produces a delayed mitogenic response and modulates the EGF response in quiescent NRK cells.

Recent studies have shown that cadmium, at subtoxic levels, may induce a response characteristic of that elicited by a type of growth factor that supports the anchorage independent growth of cells that are not fully transformed. That is, Cd++ was found to replace transforming growth factor beta in supporting soft agar growth of NRK-49F cells. To tes the extent to which Cd++ further mimics transforming growth factor beta in its effects and to establish response patterns that suggest possible molecular mechnisms of action, we have determined the effects of Cd++ and/or epidermal growth factor (EGF) on DNA synthesis in quiescent NRK-49F cells. We found that subtoxic doses of Cd++ modulate EGF-induced DNA synthesis in a dose-dependent fashion. Although Cd++ effects on early (16–24 hr) EGF-induced DNA synthesis are primarily inhibitory, later effects involve stimulation as well. Subtoxic doses of Cd++ did not stimulate DNA synthesis in quiescent cells within 24 hr of addition. At later times (40 or 64 hr), however, an increase in DNA synthesis of up to threefold was induced by 0.25 μM Cd++. This pattern of mitogenic response, involving inhibition of early growth-factor induced DNA synthesis and stimulation of late DNA synthesis, is consistent with that reported to be effected in some instances by transforming growth factor beta. Because a defined pattern of gene expression also is associated with the mitogenic responses to transforming growth factor beta, future studies at the molecular level can definitively test the degree to which Cd++ and transforming growth factor beta effects are common.

Teaching undergraduate research: The one-room schoolhouse model.

Undergraduate research in the biochemistry, cell, and molecular biology program at Drake University uses apprenticeship, cooperative‐style learning, and peer mentoring in a cross‐disciplinary and cross‐community educational program. We call it the one‐room schoolhouse approach to teaching undergraduate research. This approach is cost effective, aids learning, supports the development of science and transferable management skills, is productive, and supports diversity. It allows a small set of faculty to involve large numbers of students in research and maintain a productive scholarship program. It provides students with skills in scientific research and transferable skills that they apply to a wide set of careers.

What do the people who transport trauma patients know about tourniquets

BACKGROUND The primary study objectives were to gather information concerning the tourniquet knowledge, experience, training, protocols, preferences, and equipment of civilian prehospital providers. METHODS This is a survey of 151 prehospital care providers. RESULTS Survey respondents included 27 basic, 1 intermediate, and 75 paramedic emergency medical technicians; 1 registered nurse; 4 firefighters without medical certifications; 2 respondents not yet certified; and 1 respondent not listing certifications. Respondents had 2 months to 40 years of experience and came from emergency medical services in communities of 101 to 206,688 residents located 10 minutes to 103 minutes from a Level 1 or 2 trauma center. Twenty-five had used tourniquets: 5 in military and 22 in civilian settings. Civilian tourniquets were most frequently used for motor vehicle– then farm- and manufacturing-related injuries with severe bleeding. Tourniquet knowledge was poor for all groupings (with or without tourniquet experience, military experience, all certifications, all years of experience): 91% did not understand that wider tourniquets require less pressure for arterial occlusion, 69% did not know that stopping venous flow without arterial is harmful, and 37% did not know the correct tourniquet locations for distal limb injuries. Of the 81 on a service and without military experience, 44 had received any tourniquet training; 14 of the 44 had commercial emergency tourniquet access, and 27 indicated their service had a tourniquet protocol. Of the 37 on a service with no tourniquet training, 5 had access to a commercial emergency tourniquet, and 5 indicated their service had a tourniquet protocol. CONCLUSION Civilian prehospital providers encounter situations for tourniquet use, but many do not know information important for optimal tourniquet use. Therefore, if surgeons want civilian prehospital care to include the use of effective, arterial flow occluding tourniquets at appropriate limb locations, they need to communicate with their emergency medical service providers concerning tourniquet knowledge, training, protocols, and appropriate equipment.

Enalaprilat improves systemic and mesenteric blood flow during resuscitation from hemorrhagic shock in dogs.

We investigated the systemic and mesenteric cardiovascular effects of administering enalaprilat during resuscitation from hemorrhage. Dogs were hemorrhaged (mean arterial pressure [MAP] 40–45 mmHg for 30 min, then 30–35 mmHg for 30 min) and were then resuscitated with intermittent lactated Ringers solution (200 mL/kg/h during first 40 min, and 60 mL/kg/h during the following 130 min, MAP 75–80 mmHg). A constant-rate infusion of saline with or without enalaprilat (0.02 mg/kg/h) was initiated after 40 min of resuscitation. Blood flows declined with hemorrhage, increased with resuscitation, and then declined during the initial 40 min of resuscitation. Enalaprilat administration resulted in blood flow increases not seen in the controls (ending values for cardiac index: 2.8 ± 0.4 L/min/m2 vs. 1.6 ± 0.3 L/min/m2; celiac arterial flow 314 ± 66 L/min/m2 vs. 139 ± 13 mL/min/m2; and portal venous flow 596 ± 172 L/min/m2 vs. 414 ± 81 mL/min/m2 for enalaprilat versus controls, respectively). The greater flows with enalaprilat appeared to be due to prevention of the increases in afterload noted in the controls (ending arterial elastance values 3.73 ± 0.97 mmHg/m2/mL vs. 7.74 ± 1.80 mmHg/m2/mL for enalaprilat versus controls, respectively). We conclude that administration of a constant-rate infusion of enalaprilat during resuscitation can be used to improve systemic and mesenteric blood flow.

Preliminary resuscitation for perforated necrotizing enterocolitis: 2 cases treated with initial direct peritoneal resuscitation

We used peritoneal infusions of 2.5% dextrose solution as an adjunct to resuscitation of 2 very low-birth-weight infants having perforated necrotizing enterocolitis. This was repeated every 12 hours for 7 days before and 1 day after extensive bowel resection. The designation of this research method has been termed direct peritoneal resuscitation. We discuss our observations and the evolution of this technique from studies in the animal laboratory to a recent trial in patients with abdominal trauma. We propose that the early response benefit of this preoperative resuscitation seen in our 2 cases be investigated by others. Prospective controlled trials could then be considered for those high-risk patients having diffuse disease and shock.

Airflow-based PCO2 monitoring delivers O2 and removes CO2 from the monitored environment.

Previous investigation has suggested that the use of airflow-based gastrointestinal intraluminal PCO2 (GI PiCO2) monitoring systems may affect the local tissue microenvironment, making it not representative of the organ system as a whole. Therefore, we investigated the effects of using an airflow-based PCO2 monitoring system in a sealed environment. A 250-mL Erlenmeyer flask was filled with 10% CO2/90% N2 and was sealed with probes in place. Using a fiber-optic (Neotrend®, Diametrix Medical, St. Paul, MN) system, the PCO2 and PO2 were continuously monitored with and without the airflow-based (Tonocap®, Tonometrics, Datex-Ingstrom, Helsinki, Finland) system operating. PCO2 and PO2 remained constant when the airflow-based system was not in operation. PCO2 decreased 25.3 mmHg and PO2 increased 30 mmHg from a starting value of 0 mmHg when the airflow-based system was in operation for 12 h. The use of airflow-based methods for determining GI PiCO2 may influence the values obtained. Nonsample removing techniques such as fiber-optic methods for monitoring GI PiCO2 are preferable because they neither deliver O2 to nor remove CO2 from the local microenvironment.