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Biomedical subjects

R D Stewart

Publications and source records attributed to R D Stewart.

At least 73 records · Page 4Linked to original sources
PubMed1987

Use of a lighted stylet to confirm correct endotracheal tube placement.

Despite the fact that endotracheal intubation is a skill essential for clinicians of varied specialties, the procedure is not without risk, especially when practiced in an emergency setting, particularly the field environment. Of all complications, none is more serious than unrecognized esophageal intubation. Clinical experience with a method of guided orotracheal intubation using a rigid-wire lighted stylet prompted us to develop a technique to confirm correct intratracheal placement of an endotracheal tube using a new flexible lighted stylet designed for nasotracheal intubation. Endotracheal tubes were placed under direct vision at three sites in the upper airway of five unembalmed human cadavers: esophagus (20 cm from the teeth), trachea (20 cm from the teeth) and the right or left pyriform fossa. Thirty-five volunteer intubators were asked to identify tube placement using the transilluminated glow from the flexible nasotracheal lighted stylet. A total of 168 placements were made in 40 trials. Only one of 56 intratracheal placements was misidentified as esophageal. Of 112 extratracheal placements (esophagus or pyriform fossa), one was misidentified as intratracheal. The level of experience or training bore no relationship to the ability of the intubator to identify correct placement. We conclude from the study that this technique is a rapid and reliable method of confirming correct placement of endotracheal tubes. The use of this method could reduce, if not eliminate, unrecognized esophageal intubation in the field, emergency department, the critical care unit, and the operating room.

Humans↗
PubMed1987

Medical direction in emergency medical services: the role of the physician.

The past two decades has seen the development of sophisticated systems of prehospital care. The task now is to intensify the input of well-trained physicians into all aspects of EMS systems. This article tracks the history of EMS in this country and provides some suggested answers to the difficult questions facing this new specialty.

Clinical Competence↗
PubMed1986

Metered-dose aerosolized bronchodilators in prehospital care: a feasibility study.

The prehospital use of aerosolized bronchodilators was studied in 50 adult patients with bronchospasm. The specific beta 2-agonist, albuterol, was discharged from a metered-dose inhaler (MDI) into the Inhal-aid reservoir-delivery device. No serious adverse effects were encountered, although a substantial proportion of the patients (36%) had difficulty utilizing the device. Ability to use the system properly correlated with improvement in symptoms; inability to use the device was most clearly related to severity of clinical presentation. It is concluded that the use of aerosolized bronchodilators is feasible in prehospital care and most useful in patients with mild or moderately severe symptoms.

Administration, Inhalation↗
PubMed1986

Success rates of blind orotracheal intubation using a transillumination technique with a lighted stylet.

The technique of guided orotracheal intubation using a lighted stylet depends on the transillumination of the soft tissues of the neck to direct the tube through the glottis and into the trachea. We conducted an operating room study of this technique, recording success rates and intubation times of 50 patients undergoing elective surgery. All patients were intubated successfully, 35 of 50 (70%) on the first attempt, 12 of 15 (80%) on the second attempt, and three of three (100%) on the third attempt. The average time for intubation was 37 seconds. A new design of the lighted stylet method resulted from the experience gained. Intubator training and experience influenced initial success rates, and the cadaver laboratory was of particular value in teaching the technique.

Adolescent↗
PubMed1986

Methemoglobin levels following sublingual nitroglycerin in human volunteers.

Sublingual nitroglycerin 0.8 mg every five minutes for a total of 4.8 mg was administered to 11 healthy volunteers. One volunteer had to withdraw due to a hypotensive bradycardic reaction after 2.4 mg. In the remaining subjects, methemoglobinemia over the next hour never significantly increased from baseline levels, reaching a peak of only 0.71%. We conclude that commonly used doses of sublingual nitroglycerin do not induce significant methemoglobinemia and that nitroglycerin would not be useful in the treatment of cyanide poisoning.

Adult↗
PubMed1986

Comparison of open-chest cardiac massage techniques in dogs.

Manual compression of the heart during open-chest cardiac massage (OCPR) has been shown to be superior to closed-chest compression. Our study sought to determine, in a canine model, the optimal hand position for manual compression of the heart. Twelve dogs were anesthetized with ketamine, an orotracheal tube was placed, and anesthesia was maintained with halothane and nitrous oxide. Cannulae were placed to monitor diastolic (DBP) and systolic (SBP) blood pressures, intracranial pressure (ICP), and common carotid blood flow (CCBF). Control values were obtained under light general anesthesia, and ventricular fibrillation was induced. External CPR (ECPR) was performed with a mechanical compressor before opening the chest and pericardium through the left fifth interspace. The following sequence of three hand positions was used for OCPR: technique A, one-handed technique with thumb on left ventricle, fingers over the right ventricle, and apex in palm; technique B, two-handed technique with right ventricle cupped in left hand and fingers of right hand over left ventricle; and technique C, one-handed technique with fingers of right hand over left ventricle and heart against sternum. Each was done at a rate of 60 compressions per minute with the operator blind to results during performance. All three techniques produced significantly (P less than .05) greater DBPs and CCBFs when compared with ECPR. All three also produced significantly lower (P less than .05) ICPs when compared with ECPR. DBPs, SBPs, CCBFs, and cerebral perfusion pressures were similar for techniques B and C, and all were significantly greater (P less than .05) than those achieved with technique A.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Arterial blood gases before, during, and after nitrous oxide:oxygen administration.

The use of nitrous oxide as an anesthetic or analgesic agent frequently raises concerns about the possibility of post-inhalational diffusion hypoxemia. We undertook a study in 20 healthy volunteers to determine whether hypoxemia occurs after the self-administration by face mask of a 50:50 mixture of nitrous oxide and oxygen for 15 minutes, followed by breathing room air. Blood gases were measured through an in-dwelling arterial cannula before, during, and after inhalation of the mixture, at time O, five, ten, and 15 minutes, and then 30 seconds, 45 seconds, 2 1/2 minutes, five, and ten minutes following room air breathing. Ten of the 20 subjects breathed a control gas, a mixture of 50% nitrogen: 50% oxygen. No subject demonstrated arterial hypoxemia at any time before, during, or after self-administration of the gas mixture. In the ten subjects who self-administered the control gas there were no significant differences in the PaO2 values while they breathed either gas at any corresponding sampling time. We conclude that diffusion hypoxia is not seen in normal subjects following self-administration of a mixture of 50:50 nitrous oxide and oxygen.

Adult↗
PubMed1986

Role of the physician in the prehospital setting.

Despite the initial successes achieved in early emergency medical services (EMS) systems, many prehospital care services have developed without the intense involvement of physicians whose interest fueled the first experimental medical programs of prehospital care. Among a myriad of variables affecting EMS is the important element of intense, authoritative physician involvement in education, field supervision, and research. Recognizing this problem, many states now have legislated that EMS systems be closely supervised by medical directors. Political and financial constraints often have diluted medical influence and authority, and intense, direct field supervision is the exception rather than the rule. successful EMS systems can demonstrate their influence on morbidity and mortality through appropriate data collection and quality assurance programs. Such programs appear to have in common the element of direct involvement of competent physicians in initial training, field supervision, and policy decisions. Until recently, full-time compensated physician involvement in EMS has been regarded as unnecessary or impractical. Certainly in large urban centers such full-time involvement is mandatory. While in smaller municipalities full-time commitments may be unnecessary, partial compensation for time dedicated to EMS pursuits should be part of the EMS budget. It has been the experience of major urban EMS systems that field participation by physicians has lent irrefutable credibility to the authority of medical directors. Beyond the obvious benefits of quality assurance and supervision, the in-field EMS physician provides the impetus and leadership for EMS research conducted at the street level. Because EMS is the practice of medicine through physician surrogates in a prehospital setting, it sets the stage and tone for subsequent patient care and outcome.(ABSTRACT TRUNCATED AT 250 WORDS)

Emergencies↗
PubMed1986

Prehospital management of trauma: a tale of three cities.

The controversies that have surrounded the prehospital management of trauma stem not only from a lack of appropriate evaluation data, but also from a lack of medical accountability and "street-wise," academic physician involvement within emergency medical services (EMS) systems. As a result, the approach to EMS trauma care has often been over-generalized and debated in terms of simplistic, unidimensional concepts, such as "scoop and run" versus "field stabilization," without any regard for the type and anatomic location of injury involved, the efficiency and skill of rescuers, the proximity and actual capabilities of definitive care resources, and the logistics of the prehospital setting. The failure to understand and delineate these variables has led to conflicting studies and has confused the analysis of potential therapeutic modalities and management strategies. In view of this, a survey is provided of three major cities, each with intensive, academic physician involvement in their EMS systems, and the approach and rationale for their prehospital care strategies are summarized. In all three systems, patients generally are categorized according to three major injury types (penetrating, blunt, and thermal) and then further subcategorized with regard to anatomical involvement, specifically those involving potential (or known) internal truncal injuries versus those with isolated head trauma or isolated extremity injury. For all three, high-flow O2 delivery and aggressive, advanced airway management (by endotracheal intubation whenever feasible) are keystones of management. In cases of potential or known internal truncal injury, the priority is also expeditious transport to facilities with definitive surgical care with the establishment of IV access and rapid fluid infusions en route.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1985

Triage success in disasters: dynamic victim-tracking cards.

A dynamic victim-tracking card developed for use in community or hospital disaster exercises was tested during two hospital and two airport disaster drills. Use of the card in 375 "patients" allowed testing of the ability to evaluate the decisions of triage, the early medical intervention for "victims," and the ongoing treatment of patients with a changing medical status. The card was successful in simulating realistic changes that may occur in critically ill and injured patients. Of the 126 "patients" evaluated in an actual exercise, 55 (43.6%) were placed in the proper triage category. Four patients "died" as a result of poor initial evaluation and treatment. Medical decisions during hospital and community disaster exercises can be more realistically tested and more accurately documented with the use of the dynamic victim-tracking card.

Abdominal Injuries↗
PubMed1985

Transcutaneous pacing for bradyasystolic cardiac arrests in prehospital care.

To test the efficacy of transcutaneous pacing in prehospital bradyasystolic arrest, we applied an external transcutaneous pacing device to patients with asystole, pulseless idioventricular rhythms (PIVR), and pulseless bradycardias. Pacemaker units were carried by emergency medical services (EMS) physicians and specially trained EMS personnel. Patients were followed to determine hospital course and outcome. Of the 112 patients evaluated, information to adequately document the presence or absence of electrical capture was available in 105 cases. Fifty-five (52%) of these cases demonstrated electrical capture; 9 of 112 patients (8%) recovered pulses. Of those in asystole, 26 of 50 (52%) showed electrical capture, while the rate was 60% for those with PIVR (24 of 40 patients) and complete heart block (CHB) (3 of 5 patients), and 25% for other pulseless bradycardias (2 of 8 patients). Pulses developed following capture in five of 55 patients (9%) in asystole and in four of 44 patients (9%) with PIVR. No patient with CHB or other bradycardias developed a pulse. No patients survived to be discharged from the hospital. The average time to application of the pacing device was 29 minutes after loss of pulse. Our data strongly suggest that delayed use of the transcutaneous pacing device does not improve the dismal survival rates of patients who suffer bradyasystolic cardiac arrest. Further studies should be directed toward investigating survival rates in patients paced immediately after the onset of cardiac arrest.

Aged↗
PubMed1985

Use of a lighted stylet for guided orotracheal intubation in the prehospital setting.

Management of the airway in acutely injured patients demands special skills of the emergency physician. A technique of light-guided orotracheal intubation has been described in the literature and was performed under protocol by resident physicians in an urban mobile intensive care system. The method utilizes a flexible lighted stylet to provide a guide to correct placement through transillumination of the soft tissues of the neck. During the 12-month period of the study, 24 intubations were attempted in 21 patients using this technique. Twenty-one attempts (88%) were successful. The average time for intubation was 20 seconds, with none requiring more than 45 seconds. Fourteen intubations (67%) were successful on the first attempt. Of the three unsuccessful procedures, two were attempted in bright sunlight, and all three patients had vomited prior to the attempts. Trauma to the soft tissues in one successfully intubated patient was the only complication reported with the technique. The advantages of this method, including rapidity of intubation, ability to intubate without manipulation of the head or neck, and the apparently few complications, make it particularly attractive to emergency personnel. We conclude that guided orotracheal intubation using a lighted stylet is an effective and safe method of emergency intubation, even in the adverse prehospital environment.

Critical Care↗
PubMed1985

Influence of mask design on bag-mask ventilation.

Adequate positive pressure ventilation in the field or emergency department continues to represent a major challenge. A new face mask design that recently has been introduced consists of a low-pressure "balloon" through which a Guedel airway is attached and extended proximally through the mask to allow the attachment of a ventilation bag. The mask is designed to seal the nares and mouth when pressed against the face. Ventilation is achieved through the airway which extends through the mask to just above the epiglottis. We designed a study to evaluate ventilating volumes and mask leak with this mask design, and to compare these parameters with those achieved with standard masks. Thirty volunteers with varied experience in bag-mask ventilation were chosen to ventilate a specially adapted ventilation manikin connected to a test lung that was capable of simulating varied compliances. Spirometers measured volumes delivered to the ventilating bag and lung, and mask leak could be calculated from these readings. A constant rate of 12 ventilations per minute was maintained by each volunteer for two minutes. Volunteers ventilated the test lung using three masks in random sequence: the SealEasy mask (Respironics Inc, Monroeville, PA), a Laerdal mask (old type), and a transparent Robertshaw mask with inflatable black rim. The average tidal volume delivered by the SealEasy mask was consistently higher than either of the other two. Significantly (P less than .05) higher volumes were delivered with the SealEasy mask when compared to the Laerdal, and significantly lower mask leaks were seen when the SealEasy was compared to both.(ABSTRACT TRUNCATED AT 250 WORDS)

Equipment Design↗