Single hemorrhage: a clinically relevant canine model of hemorrhagic shock.

Clinically encountered hemorrhagic shock is usually caused by a single, rapid hemorrhage secondary to trauma. Experimental models of shock, however, have utilized anesthetic agents and hemorrhage protocols which may compromise the clinical relevance of their findings. This report characterizes the response of conscious, splenectomized dogs to a single hemorrhage of varying rates and volumes, uncomplicated by the presence of anesthetic agents. The duration of a 40 ml kg-1 hemorrhage affected the magnitude of blood pressure recovery, but did not alter the decompensating drop in blood pressure. The shortest hemorrhage duration was chosen for further study, as the blood pressure profile for this hemorrhage duration demonstrated most clearly the recovery, plateau, and decompensation phases. Increasing the hemorrhage volume to 43 ml kg-1 caused a reproducible decrease in the magnitude of the blood pressure recovery, the time to decompensation, and the time to death. Splenectomized dogs, then, demonstrate a reproducible response to a fixed-volume hemorrhage, making chronically instrumented conscious dogs a good animal model with which to study the progression of hypovolemic shock.

Serum magnesium increases following severe hemorrhage in dogs blocked by verapamil treatment.

The opening of voltage sensitive calcium channels is an important event in the progression of irreversible shock, allowing the entry of toxic amounts of calcium (Ca2+) into the cells. Because intracellular magnesium (Mg2+) can efflux through these same channels, changes in serum Mg2+ may reflect the patency of these channels. In this study, electrolytes and selected serum enzymes were monitored in chronically instrumented conscious dogs to follow the progression of shock following a fixed volume hemorrhage. Plasma enzymes indicative of liver damage were elevated only in the terminal phase of hemorrhagic decompensation. A significant increase in serum Mg2+ was evident 60 min following hemorrhage, even though arterial pressure was still recovering. Serum Mg2+ continued to rise throughout the recovery and decompensating phases of shock. Verapamil treatment, which increased survival time and survival rate, significantly attenuated the changes in serum Mg2+ which normally followed hemorrhage. These results indicate that serum Mg2+ may be a useful indicator of the severity and the progression of hemorrhagic shock.

Transcutaneous oxygen tension measurements during hemorrhagic hypoperfusion using Trendelenburg and the pneumatic antishock garment.

Transcutaneous oxygen tension (PtCO2) was observed during hemorrhagic hypoperfusion using four therapeutic modalities: pneumatic antishock garment (PASG), 20 degrees Trendelenburg positioning, combined PASG-Trendelenburg, and whole blood infusion. Anesthetized mongrel dogs were mechanically ventilated. A heated transcutaneous oxygen sensor was applied to the skin overlying the sternum. Animals were bled over 10 min of 25% of their calculated blood volume. A therapeutic intervention was applied at the onset of hemorrhage (PASG, Trendelenburg, PASG-Trendelenburg or control). All animals were observed for 20 min, then during a 10-min shed blood reinfusion period, and for 20 min thereafter. PtCO2 was measured continuously and the following were measured serially: cardiac output, mean arterial pressure (MAP), mixed venous oxygen tension (MvO2), and arterial oxygen tension (PaO2). Cardiac index (CI) and the oxygen extraction ratio were calculated. PtCO2 decreased immediately after hemorrhage in all animals. Control values remained consistently below values for active interventions during this time. All groups regained baseline levels of PtCO2 after reinfusion of shed blood volume. PaO2 remained nearly constant during all experiments. MAP and CI fell in all groups following hemorrhage but did so less precipitously in the PASG group. The PASG and PASG-Trendelenburg groups showed the greatest increase in CI during reinfusion. These results suggest that when PtCO2 is relied upon as an indicator of adequacy of resuscitation during moderate hemorrhagic shock, that cutaneous perfusion may be improved by the PASG or Trendelenburg position, and that perfusion is most effectively restored by blood infusion.

Prevention of "irreversible" hemorrhagic shock by the preservation of cellular integrity.

The clinically encountered state of hypovolemic shock results from a series of metabolic and cardiovascular responses to tissue hypoperfusion. Recent advances have increased our understanding of the consequences of tissue hypoxia, and identified at the cellular level those changes which cause the damage to be "irreversible", or refractory to treatment. To be successful, therapeutic interventions should be designed to 1) limit, if not reverse, the subcellular alterations in membrane stability and mitochondrial function which herald the transition from compensated to decompensated shock, and 2) re-hydrate the individual to restore normal circulatory dynamics and to prevent further cellular damage. It is proposed that calcium channel blocking agents and/or high energy phosphate compounds may delay the positive feedbacks which cause irreversible tissue damage, and thus may be useful initial interventions in the treatment of hypovolemic shock.

Organizational characteristics, occupational stress, and depression in rural emergency medical technicians.

A model of organizational characteristics, occupational stress and mental health in emergency medical technicians (EMTs) is developed and tested. Supervisor behavior and work group support are used as predictors of negative role perception. Negative role perception is specified as intervening between the organizational variables and occupational stress. Occupational stress is hypothesized to directly influence depression. Data collected from 250 EMTs is used in a structural equation analysis to estimate model parameters. The sample is mostly male (74%), white (94%), and married (68%). Results suggest that there is a direct relationship between perceived occupational stress and increased depression. Role perception is a critical intervening variable between supervisor behavior, work group support, and occupational stress. The findings suggest that EMTs are more satisfied when supervisory practices result in an environment which encourages open expression and group problem solving. This work environment leads to more supportive relationships among squad members, reduced role ambiguity, and decreased occupational stress and depression.

Vascular prostheses.

The quest for an ideal vascular graft began in the early 1950s and continues at a steady pace. The perfect graft has yet to be designed. As a result, patients with vascular prostheses may suffer complications that range from minor to catastrophic. The emergency physician may be faced with the initial presentation of patients with these vascular graft complications. If he or she is not familiar with these possibilities, then the resulting morbidity and mortality could be devastating. Probably the most unnerving complication involving the failure of vascular prostheses is that of the aortoenteric fistula. Instantaneous decisions and interventions must be made when a patient presents in this state of pre-exsanguination. Massive GI bleeding is at one end of the spectrum with other less-severe GI complications involving aortoenteric erosions and small bowel obstructions due to graft migration at the other end of the spectrum. Infection of a vascular prosthesis is a complication much feared by vascular surgeons. A spectrum of presentation also exists here whereby a patient may present with an obvious draining wound or with subtle complaints of fever, weakness, and a minimally elevated white blood cell count. The function of the emergency physician is critical here but only if he or she is able to suggest the possibility of graft infection to the admitting physician. Fortunately, thrombosis of a vascular graft is an infrequent complication that may occur at any time postoperatively, although the frequency decreases with time. There are many different causes of graft occlusion of which the emergency physician should be aware. If the cause of the thrombosis is known, then the secondary vascular reconstruction can be optimized. The dialysis population has grown rapidly over the past two decades and as a result so have complications of renal dialysis grafts. Because the dialysis population now includes large numbers of older subjects as well as those with systemic diseases such as diabetes and HIV, recognition and prompt aggressive management of clinical complications is of paramount importance.

Elder abuse and neglect: the emergency medicine perspective.

The diagnosis of elder abuse and neglect is difficult to accomplish, making intervention elusive, primarily because to date there is no set definition of either abuse or neglect. This paper, written primarily from the American viewpoint, addresses definitions; assessment and diagnosis; aetiology of abuse; intervention; prevention and management; ethical and legal considerations; elder abuse and the emergency physician; and future goals.

Exertional rhabdomyolysis in a body builder abusing anabolic androgenic steroids.

Rhabdomyolysis, or acute skeletal muscle destruction, may be accompanied by myoglobinaemia, myoglobinuria, and an elevated serum creatine kinase level. This disorder has many potential causes. In this article, the authors describe a case of rhabdomyolysis occurring after vigorous weight lifting by a man who was supplementing his weight-training programme with the intake of anabolic androgenic steroids dispensed to him by a colleague.

Spinal epidural haematoma as a result of warfarin/fluconazole drug interaction.

This is the first reported case in the emergency medicine literature of a drug interaction between warfarin and fluconazole. We present a case of spinal epidural haematoma and summarize four other case reports reported elsewhere from 1988 to 1996. We admonish emergency physicians to be aware of this dangerous drug combination. Warfarin and fluconazole are frequently encountered drugs in the emergency department and thus any interaction between these drugs is of considerable importance.

Thrombolytic therapy in review.

The use of thrombolytic agents for both coronary and noncoronary indications is a rapidly progressing field. There has been substantial debate over which disease processes ultimately benefit from the use of thrombolytic agents. In addition, many recent studies have focused on comparing different thrombolytic agents and dosing regimens in an attempt to gain optimal therapeutic benefit with minimal risk. This paper discusses the current status of thrombolytic therapy for coronary artery disease, pulmonary embolus, peripheral vascular thrombosis, and cerebrovascular infarction.

The use of military antishock trousers in trauma--a reevaluation.

The military antishock trousers (MAST) continue to be used widely. The physiologic mechanisms of action have been further elucidated. There are many potential complications associated with their use, some of which are serious. While most observations in the past were based on dog studies or human volunteers, clinical studies are now providing new information that questions the usefulness of the MAST.

Flexible fiberoptic sigmoidoscopy in the emergency department.

Endoscopic examination of the large bowel is an historically old procedure. It has become an important element in the initial evaluation of colorectal disorders. Recently the flexible fiberoptic sigmoidoscope (FFS) has displaced the rigid scope because of increased patient comfort and compliance and markedly improved accuracy in diagnosing left colon lesions. The FFS is a valuable adjunct to the routine investigation of acute and chronic colorectal complaints seen in the emergency department. It has been endorsed by the American Cancer Society and is an easily learned and safe procedure when taught properly.

Extortion in the emergency department.

We present the case of a 33-yr-old female patient who, along with members of her family, attempted to extort approximately $6000.00 from our institution and her insurance company. This attempted extortion was done under the guise of a missed retained foreign body. The patient initially presented to our emergency department with a laceration to her right forearm; X-ray studies obtained after the wound had been sutured revealed no foreign body. Several days later, the patient and family members approached our administrative staff demanding recompense for metal fragments discovered in the patient's wound at another facility. Comparison of radiographs revealed that the metallic fragments were placed in the wound after she was treated and released from our emergency department, and monetary compensation was denied.