Biomedical subjects
A B Sanders
Publications and source records attributed to A B Sanders.
Prehospital care telemetry--how essential?
The telemeterized ECG, once a necessary and important part of prehospital care, may now be an unnecessary, expensive luxury. Paramedic training now produces a professional capable of diagnosing ECG rhythms as accurately as emergency physicians. ECG telemetry may, however, have utility for esprit de corps, training, evaluation, and supervision of new or less trained paramedics. Recommendations for establishing or renewing community telemetry systems are made.
Preeclampsia.
The case of a 32-year-old primigravida, 32 weeks gestation, with nausea, vomiting, thrombocytopenia, and abnormal liver function tests is presented. A diagnosis of severe preeclampsia was made and the patient underwent emergency cesarean section. Improvement of clinical symptoms and laboratory studies followed over the succeeding days. These less common manifestations of preeclampsia indicate severe disease necessitating aggressive management, even in the setting of a normal blood pressure. Thrombocytopenia, microangiopathic hemolytic anemia, or abnormal liver functions in a patient presenting in the latter half of pregnancy may be manifestations of severe preeclampsia.
The roles of methoxamine and norepinephrine in electromechanical dissociation.
Electromechanical dissociation (EMD) in patients in cardiac arrest is associated with a poor prognosis. Pressor agents, particularly alpha-agonists, have proven to be useful in resuscitation from asphyxial and fibrillatory arrest in the animal model. Beta-agonists, such as isoproterenol, have not been shown to improve the resuscitation rate. The standard pressor used in all forms of cardiac arrest is epinephrine. The key question that must be considered is whether methoxamine or norepinephrine is superior to epinephrine in resuscitating patients in cardiac arrest. Methoxamine is a pure alpha 1 agonist causing vasoconstriction and increased peripheral vascular resistance. Norepinephrine and epinephrine demonstrate activity at alpha 1, alpha 2, beta 1, and beta 2 receptor sites. Does alpha 2 and beta activity help or hinder resuscitation? Beta activity on the myocardium will increase oxygen consumption (inotropic and chronotropic effects), may predispose to arrhythmias, and will shunt blood from the endocardium to the epicardium. On the other hand, there is evidence that beta agonists increase coronary and cerebral blood flow. Outcome studies have shown methoxamine to be comparable to epinephrine in resuscitation from asphyxial arrest. One study demonstrated methoxamine's superiority in raising the aortic diastolic pressure and resuscitating animals from ventricular fibrillation. No significant advantage of norepinephrine use is evident in the literature. Controlled experiments in the animal model and in human patients must be done to determine whether methoxamine or epinephrine is superior in resuscitation from EMD and other forms of cardiac arrest.
Improved resuscitation from cardiac arrest with open-chest massage.
A study was done to assess the effect of open-chest massage on resuscitation from cardiac arrest. Ten mongrel dogs weighing 20.3 +/- 3.2 kg were fibrillated electrically. Cardiopulmonary resuscitation (CPR) was initiated and continued for 15 minutes. Half the dogs with coronary perfusion pressures less than 30 mm Hg underwent thoracotomy and internal cardiac massage for three minutes. Closed-chest massage was continued with the other dogs. All dogs were defibrillated at 19 minutes, and resuscitation was determined at 20 minutes after defibrillation. None of the dogs in the closed-chest massage group was resuscitated successfully. Four of the five dogs that underwent open cardiac massage were resuscitated. Significant differences in aortic pressures and coronary perfusion pressures were noted for the first two minutes of open-chest massage (P less than .05). The results of this study indicate that resuscitation may be improved using open-chest massage when closed-chest massage fails to produce an adequate coronary perfusion pressure.
Resuscitation and arterial blood gas abnormalities during prolonged cardiopulmonary resuscitation.
A study was undertaken to determine the pattern of arterial blood gas (ABG) concentration in the canine model undergoing prolonged cardiopulmonary resuscitation (CPR) from fibrillatory arrest, and to determine the importance of acid base abnormalities in predicting resuscitation. Ventricular fibrillation was induced electrically in 12 dogs. CPR was begun at 3 minutes and continued for 27 minutes, at which time the dogs were defibrillated. ABG samples were taken at 0, 8, 18, and 28 minutes of ventricular fibrillation. Seven of the 12 dogs were resuscitated successfully. There was no difference in pH, PCO2, or PO2 between the survivors and nonsurvivors at any of the points measured. A pattern of pH and PCO2 abnormalities was noted in each dog over 30 minutes. Each developed a respiratory alkalosis that peaked at 8 minutes. During the next 22 minutes the pH gradually declined. This combination of respiratory alkalosis and metabolic acidosis resulted in normalization of the pH at about 18 minutes of fibrillation. We concluded that when adequate ventilation is provided in the canine model undergoing CPR, significant arterial acidemia does not occur for at least 18 minutes. Further, acid base abnormalities did not correlate with successful resuscitation.
Reliability of femoral artery sampling during cardiopulmonary resuscitation.
A study was undertaken to determine whether femoral arterial blood gas (ABG) content adequately reflects central oxygenation and acid base status during cardiopulmonary resuscitation (CPR) from fibrillatory arrest in the canine model. Six dogs were fibrillated electrically. After 3 minutes, CPR was begun. ABG samples were taken simultaneously from femoral and thoracic aortic catheters at 0, 3, 8, 13, 23, and 28 minutes of ventricular fibrillation. Pair analysis revealed a statistically significant difference between aortic and femoral PO2 values throughout the duration of external chest compression and assisted ventilation (P less than .05). The aortic PO2 was 12% more than the femoral PO2. There was no difference in pH and PCO2 between the femoral and aortic blood gas samples. The lower femoral PO2 observed may be the result of poorer blood flow to the lower half of the body. It was concluded that femoral PO2 underestimates aortic PO2 during external chest compression and assisted ventilation in the canine model.
Curriculum for undergraduate education in emergency medicine.
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Prognostic and therapeutic importance of the aortic diastolic pressure in resuscitation from cardiac arrest.
A study was done to determine if 12 dogs could be resuscitated from 30 min of ventricular fibrillation if aortic diastolic blood pressure was maintained above 30 mm Hg by administration of epinephrine and, in 6 cases, saline solution during cardiopulmonary resuscitation (CPR). Of the 12 dogs seven were resuscitated successfully. The survivors received 3.4 +/- 1.7 mg of epinephrine, whereas the nonsurvivors received 11.1 +/- 2.1 mg of epinephrine. The aortic diastolic blood pressure was significantly higher (p less than .05) in the survivors at 12, 18, 24, and 30 min of ventricular fibrillation. In all nonsurvivors, it was impossible to maintain diastolic pressure above 30 mm Hg even with large doses of epinephrine and saline. Maintenance of an adequate diastolic blood pressure during CPR appears important for survival.
Educating internists in emergency medicine.
The education of internists in emergency medicine needs to be thoughtfully planned by those involved in their education. Objectives for their emergency medicine rotation include the recognition and initial treatment of true medical and surgical emergencies, clinical experience with and knowledge of common acute primary care problems, the ability to handle several patients with problems having different degrees of urgency, effective use of consultants in the follow-up and management of difficult patients and a knowledge of and clinical experience with the prehospital care system. A curriculum should be designed to give the resident a core of didactic material in addition to supervised clinical experience. The rotation should be evaluated by both residents and faculty from internal medicine and emergency medicine to determine if it is accomplishing the objectives set forth.
Alterations in MAST suit pressure with changes in ambient temperature.
A study was undertaken to test the hypothesis that change in ambient air temperature has an effect on MAST suit pressure according to the ideal gas law. Two different MAST suits were tested on Resusci-Annie dummies. The MAST suits were applied in a cold room at 4.4 degrees C and warmed to 44 degrees C. Positive linear correlations were found in nine trials, but the two suits differed in their rate of increase in pressure. Three trials using humans were conducted showing increased pressure with temperature but at a lesser rate than with dummies. A correlation of 0.5 to 1.0 mm Hg increase in MAST suit pressure for each 1.0 degrees C increase in ambient temperature was found. Implications are discussed for the use of the MAST suit in environmental conditions where the temperature changes.
Effect of altitude change on MAST suit pressure.
Transport of patients involving changes in altitude has become commonplace in the treatment of trauma patients. Often these patients are treated with medical antishock trouser (MAST) suits initially and during transport. The effects of altitude changes on the pressures generated in MAST suits were systematically investigated. Jobst Standard Antishock Air Pants were applied to the lower half of a Resusci-Anne dummy and inflated to 30 mm Hg of pressure. In a simulation of patient transport, the inflated MAST suit and dummy were placed in a helicopter and ascended from 2,500 feet to 9,500 feet. Pressures increased to 84, 87, and 87 mm Hg in three separate trials. Intermittent MAST suit pressure readings at 1,000-foot increments in altitude showed a positive linear relationship. Three descending trials, in which the MAST suit was inflated to 60 mm Hg at 9,500 feet and the helicopter descended to 2,500 feet, were also done. Pressures dropped to 7, 8.5, and 8 mm Hg in the three trials. A positive second order relationship between MAST suit pressure and altitude was noted for the descending trials. It was concluded that MAST suit pressure is a function of altitude. Emergency medicine personnel should be aware of this, and should monitor patients accordingly when transporting through changes in altitude.
Airway trauma.
The mechanism of injury, diagnosis, and treatment of maxillofacial, laryngeal, tracheal, and bronchial trauma are considered. Also discussed is pulmonary barotrauma.
Botulism.
Clostridium botulinum is ubiquitous in the environment, yet symptoms of botulism occur in humans only if toxin A, B, or E is ingested, absorbed in the intestine, and bound and eventually internalized in the neuronal receptors, producing neuromuscular blockade. Clinically, botulism is divided into four types: food borne, infantile, wound, and unclassified. Systemic neurological symptoms occur within 72 hours of gastrointestinal symptoms and can progress rapidly to respiratory paralysis. Diagnosis depends on a high index of suspicion, but cultures and special tests may be helpful. Treatment remains mostly supportive with good respiratory care emphasized. Use of botulism antitoxin and guanidine may be helpful in some cases.
Failure of one method of simultaneous chest compression, ventilation, and abdominal binding during CPR.
Some modified methods of CPR improve carotid blood flow, but there are no studies to show that these modified techniques improve survival, Accordingly, an experimental CPR technique using simultaneous chest compression, ventilation (SCV-CPR), and abdominal binding was compared to standard CPR in beagle dogs. The modified technique utilized a broad-based bellows device that was mechanically compressed, producing chest compression, delivering a volume of air to the endotracheal tube, and pressurizing an abdominal binder. The duration of ventricular fibrillation and CPR was 5 min. Five of the 6 dogs could be resuscitated with standard CPR. None of 6 dogs could be resuscitated using this modified method of SCV-CPR and abdominal binding. The aortic diastolic pressure and the diastolic gradient between the aorta and right atrium was significantly different between the 2 groups. Because these pressures relate to the coronary perfusion pressure, they may explain the discrepancy in the survival rate. This study suggests increasing carotid blood flow during CPR will not necessarily improve survival.
Pneumatic counterpressure.
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Allocation of time in three academic specialties.
A survey was done to: 1) characterize the allocation and distribution of time by tenure track emergency physicians, and 2) compare the time distribution of emergency physicians to two other academic disciplines. All emergency medicine residency programs were surveyed by telephone to determine if faculty were eligible for tenure and if tenure was available, how many hours per week were spent on clinical duties, research, and administrative tasks. Similar information was compiled from cardiology and orthopedic surgery faculty at the same universities. Data from the survey revealed that a tenure track assistant professor spends 23 hours (46%) working clinical shifts in the emergency department; 11 hours (20%) doing research and 18 hours (34%) in administrative tasks. In contrast, cardiologists spend significantly more time in clinical duties (32 hours) and research (18 hours). However, cardiologists spend significantly less time in administrative duties (10 hours). Data for orthopedic surgeons show a similar pattern. Distributions within each academic discipline were also analyzed and a significant difference in research time was found between four tenure track emergency medicine programs and the other eighteen. Data from this survey may help academic emergency physicians evaluate how they are allocating their time in comparison to other busy clinical specialties.