Prehospital ECG monitoring of chest pain patients

Prehospital electrocardiograms (ECGs) have been shown to decrease the time from onset of pain to onset of treatment. They are obtained prior to treatment while the patient is likely to have his/her most intense pain. With paramedics initiating care in the field, patient assessments may be clinically different by the time the patient reaches the hospital. Thus, obtaining an ECG as early as possible during treatment could aid in the access to treatment for the few patients whose ECGs improve with prehospital care. We present a case in which the prehospital presentation was indicative of an acute myocardial infarction (MI), whereas the presentation to the hospital was not as clear-cut. The patient was taken immediately to the catheterization laboratory based on the prehospital findings and was found to have an acute MI that was treated. Laboratory findings indicated that there was a significant improvement in patient outcome based on this early treatment. This case further illustrates the role of a prehospital ECG.

Role of membrane type 1-matrix metalloproteinase and gelatinase A in head and neck squamous cell carcinoma invasion in vitro

The proteolytic activity of gelatinase A, a member of the matrix metalloproteinase (MMP) family, is considered to be a critical factor in tumor cell penetration of the extracellular matrix. To express catalytic activity, however, gelatinase A requires activation by another MMP, membrane type 1-matrix metalloproteinase (MT1-MMP). The head and neck squamous cell carcinoma cell line, UM-SCC-1, forms a quiescent monolayer atop collagen unless stimulated with epidermal growth factor (EGF; 3.5 nmol/L), which induces single cell invasion within 48 hours. To determine the role of the MT1-MMP/gelatinase A protease system in an in vitro stromal invasion model, expression vectors for MT1-MMP and gelatinase A were transfected into UM-SCC-1 (SCC-1/MT and SCC-1/gelA, respectively). SCC-1/MT tumor cells were found to invade in the absence of growth factor stimulation. Additionally, these cells displayed shorter onset to invasion and penetrated deeper into the collagen gel with EGF stimulation than did control vector transfectants. SCC-1/gelA cells similarly demonstrated invasion in the absence of EGF and a heightened invasive potential under EGF-stimulated conditions. These results suggest that the MT1-MMP/gelatinase A protease system participates in squamous cell carcinoma invasion of collagenous matrices.

Warmed versus room temperature saline solution for ear irrigation: a randomized clinical trial

STUDY OBJECTIVE

To test the hypothesis that ear irrigation with warmed normal saline solution is more comfortable and results in fewer side effects than irrigation with room temperature saline solution in normal volunteers.

METHODS

The study was a randomized, single-blind, crossover trial in which each subject received 30 mL warmed normal saline solution in 1 ear and 30 mL room temperature saline solution in the opposite ear. The solutions (warmed versus room temperature) and the order of irrigation (right versus left ear) were separately randomized. Investigators obtaining scores were blinded to solution temperature. Subjects rated the discomfort of irrigation, using separate visual analog scales, from 0 (no pain) to 100 mm (worst pain ever).

RESULTS

Forty volunteers were enrolled in the study. The mean difference in visual analog scale scores favoring warmed over room temperature saline solution was 26 mm (95% confidence interval [CI], 19 to 33 mm; P <.0001). Twenty percent more patients reported dizziness with room temperature irrigation (95% CI, 6% to 34%). There was no gender effect or order effect for the 2 solutions.

CONCLUSION

Warmed normal saline solution was both clinically and statistically more comfortable than room temperature saline solution as an ear irrigant in normal volunteers. Significantly less dizziness was reported with the warmed solution.

The impact of cultural and familial context on behavioral and emotional problems of preschool Latino children

This study examined the impact of financial, cultural, and family variables on the incidence of behavioral and emotional problems in a group of two- and three-year-old Latino children. The vulnerability of these children to mental health problems stems from the many challenges faced by their families, especially those associated with acculturation and poverty. Results indicate that most problems experienced by the children were related to depression and social withdrawal. Children were at greatest risk whose parents had immigrated from Central America, whose families relied more extensively on internal coping strategies such as passive resignation, and whose parents were dissatisfied with their family's interactions.

Characterization of matrix metalloproteinases produced by rat alveolar macrophages

Evidence presented in the accompanying article (Gibbs, D. F., T. P. Shanley, R. L. Warner, H. S. Murphy, J. Varani, and K. J. Johnson. 1999. Role of matrix metalloproteinases in models of macrophage-dependent acute lung injury: evidence for alveolar macrophage as source of proteinases. Am. J. Respir. Cell Mol. Biol. 20:1145-1154) implicates alveolar macrophage matrix metalloproteinases (MMPs) in two models of acute lung inflammation in the rat. As a prerequisite to understanding which specific MMPs might be involved in the injury and how they might function, it was necessary to know the spectrum of enzymes present. To this end, alveolar macrophages were obtained from normal rat lungs by bronchoalveolar lavage, placed in culture with and without various agonists, and assessed by a variety of techniques for MMPs. The identification process involved characterization by gelatin, beta-casein, and kappa-elastin zymography, with confirmation of identity by Western blot/immunoprecipitation. Message levels of detected MMPs were assessed by Northern blot. Rat alveolar macrophages were found to produce a low constitutive level of MMP-2 (72-kD gelatinase A) that was only modestly upregulated following stimulation with phorbol myristate acetate, bacterial lipopolysaccharide, or immunoglobulin A-containing immune complexes. Although control cells were found to produce little or no MMP-9 (92-kD gelatinase B) or MMP-12 (metalloelastase), both enzymes were markedly upregulated upon stimulation. In the same stimulated macrophages there was little activity against type I collagen (associated with MMP-13 [collagenase-3] on the basis of Western blotting), no activity suggestive of stromelysin or matrilysin, and no measurable secretion of the serine proteinases, elastase and cathepsin G. These data demonstrate the ability of rat alveolar macrophages to elaborate certain MMPs under proinflammatory conditions, consistent with their possible involvement in the progression of acute inflammation.

The proposed use of a 'screening test' to assess oxygenator performance

This study aimed to assess whether the use of the physiological shunt equation could (within the first five minutes of initiating CPB) serve as a 'screen' to differentiate normal and dysfunctional oxygenator performance. If dysfunction severe enough to require replacement was necessary, the normothermic patient could be weaned from CPB and replacement would be carried out under safe, controlled conditions. This technique would require postponing the induction of hypothermia (if used), aortic cross-clamping, and arresting the heart until after this screen was completed. This study demonstrates that a strong negative correlation exists between the degree of blood shunting and the membrane's 0 2 transfer performance (r = -0.874). This relation enables us to predict 0 2 transfer performance when only the shunt fraction is known. Of the 41 oxygenators used in this study, 40 demonstrated normal, or below-normal, shunt fractions. Oxygen transfer performance at or above predicted levels would be anticipated for these oxygenators. One of the 41 oxygenators had mildly elevated shunt fractions, which we predicted would be associated with mild 0 2 transfer dysfunction. Based on the performance screen worksheet we created, replacement was not necessary since the oxygenator maintained high levels of 0 2 transfer in reserve despite its marginal performance dysfunction. Assessment of oxygenator performance dysfunction in this earliest phase of CPB would greatly reduce the incidence of emergency oxygenator replacement secondary to actual or perceived oxygenator failure later in the course of the procedure.

Impact of EMS education on emergency medicine ability and career choices of medical students

OBJECTIVE

To determine whether a course in emergency medical services (EMS) impacts on the perceived ability of medical students to render care in emergencies such as choking and cardiac arrest, and affects their choice of emergency medicine as a career.

METHODS

An eight-question pre- and postcourse survey was given to first- and second-year medical students. The elective course lasted a semester (four months) and dealt with prehospital emergency care, including ambulance rides and helicopter observation. Surveys were collected over a period of seven semesters. The eight-question survey assessed the student's experience, interest, and perceived competence. Precourse and postcourse results were compared using a chi-square with p<0.05 considered significant.

RESULTS

Two hundred ten students enrolled in the EMS course. A total of 384 surveys were completed, 190 precourse and 194 postcourse surveys. Eighty-three students (44%) had a family member in the medical profession, five students (2.6%) had experience as an EMT or EMT-P, and 67 students (35%) had worked in any capacity in an ED. There was a statistically significant positive shift in the responses to both questions relating to self-perceived competency (p<0.01). Thirty-eight students (20%) precourse and 58 students (30%) postcourse were interested in emergency medicine as a career (p = 0.03).

CONCLUSION

A course in EMS has significant impact on the perceived ability and career choice of medical students. Further study of an EMS curriculum design is needed to determine what information is critical to medical students' education and valuable in their career choice decisions.

Blocking a selective association in pigeons

Experiment 1 demonstrated for the first time a stimulus-reinforcer interaction in pigeons trained with free-operant multiple schedules of reinforcement. Pigeons that treadle pressed in the presence of a tone-light (TL) compound for food exhibited primarily visual stimulus control on a stimulus-element test, whereas pigeons that avoided shock in TL exhibited auditory control. In Experiment 2, this selective association was blocked in pigeons pretrained with the biologically contingency-disadvantage element of the compound (i.e., tone-food or light-shock) before TL training. When this pretraining preceded compound-stimulus training, control was now auditory in pigeons that treadle pressed for food and was visual in pigeons that avoided shock. Previous attempts at blocking this selective association were unsuccessful in pigeons (LoLordo, Jacobs, & Foree, 1982) but were successful in rats (Schindler & Weiss, 1985). Experiment 2 established that selective associations can be blocked in pigeons when the procedures that were effective with rats were systematically replicated. These results further demonstrate the cross-species generality of an associative attentional mechanism involving a biological constraint on learning in species with different dominant sensory systems.

Oxygen delivery during retrograde cerebral perfusion in humans

Retrograde cerebral perfusion (RCP) potentially delivers metabolic substrate to the brain during surgery using hypothermic circulatory arrest (HCA). Serial measurements of O2 extraction ratio (OER), PCO2, and pH from the RCP inflow and outflow were used to determine the time course for O2 delivery in 28 adults undergoing aortic reconstruction using HCA with RCP. HCA was instituted after systemic cooling on cardiopulmonary bypass for 3 min after the electroencephalogram became isoelectric. RCP with oxygenated blood at 10 degrees C was administered at an internal jugular venous pressure of 20-25 mm Hg. Serial analyses of blood oxygen, carbon dioxide, pH, and hemoglobin concentration were made in samples from the RCP inflow (superior vena cava) and outflow (innominate and left carotid arteries) at different times after institution of RCP. Nineteen patients had no strokes, five patients had preoperative strokes, and four patients had intraoperative strokes. In the group of patients without strokes, HCA with RCP was initiated at a mean nasopharyngeal temperature of 14.3 degrees C with mean RCP flow rate of 220 mL/min, which lasted 19-70 min. OER increased over time to a maximal detected value of 0.66 and increased to 0.5 of its maximal detected value 15 min after initiation of HCA. The RCP inflow-outflow gradient for PCO2 (slope 0.73 mm Hg/min; P < 0.001) and pH (slope 0.007 U/min; P < 0.001) changed linearly over time after initiation of HCA. In the group of patients with preoperative or intraoperative strokes, the OER and the RCP inflow-outflow gradient for PCO2 changed significantly more slowly over time after HCA compared with the group of patients without strokes. During RCP, continued CO2 production and increased O2 extraction over time across the cerebral vascular bed suggest the presence of viable, but possibly ischemic tissue. Reduced cerebral metabolism in infarcted brain regions may explain the decreased rate of O2 extraction during RCP in patients with strokes.

IMPLICATIONS

Examining the time course of oxygen extraction, carbon dioxide production, and pH changes from the retrograde cerebral perfusate provided a means to assess metabolic activity during hypothermic circulatory arrest.

Usefulness of the blood urea nitrogen/creatinine ratio in gastrointestinal bleeding

This study was conducted to evaluate the blood urea nitrogen/creatinine (BUN/Cr) ratio for distinguishing an upper versus lower source of gastrointestinal (GI) bleeding. Charts of patients who presented to the emergency department (ED) with the diagnosis of GI bleeding from August 1995 to August 1996 were retrospectively reviewed for source of bleeding, initial BUN, Cr, BUN/Cr ratio, hematocrit (Hct), and need for transfusion. A total of 124 patients were eligible for inclusion, 71 (57%) of whom were male. A total of 63 (51%) presented with blood in stool and 53 (43%) with bloody emesis; 8 (6%) had blood in both emesis and stool. A total of 31 (25%) patients had a lower GI bleed, 88 (70%) had an upper, and 5 (4%) had both upper and lower bleeding sources. The mean BUN level was 24 mg/dL, the mean Cr level 1.03 mg/dL, and the mean BUN/Cr ratio was 24. The mean hemoglobin (Hb) level was 11.3 g/dL, the mean Hct was 32 g/dL, and 51% required transfusion. Upper GI bleeding was significantly correlated with age younger than 50 (P = .01) and male gender (P = .01; odds ratio, 3.13). Taking into account age and gender, the BUN/Cr ratio correlated significantly with an upper GI source of bleeding (P = .03), with a ratio greater than 36 having a sensitivity of 90% and a specificity of 27%. The area under the receiver operating characteristic curve using age, gender, and BUN/Cr ratio was .73 (95% confidence interval, .62 to .84).

Warmed versus room temperature saline solution for ocular irrigation: a randomized clinical trial

STUDY OBJECTIVE

To test the hypothesis that ocular irrigation with warm saline solution is more comfortable than irrigation with room temperature saline solution in normal volunteers.

METHODS

The study was a randomized, single-blind crossover trial, in which each subject received 30 mL warmed and 30 mL room temperature saline solution in opposite eyes. The solutions (warmed versus room temperature) and the order of irrigation (right eye versus left) were separately randomized. Physicians were blinded to solution temperature. Subjects rated the discomfort of irrigation on separate visual analog scales (VAS). The study had 80% power to detect at least a 12-mm difference in VAS readings.

RESULTS

Thirty-five volunteers were enrolled in the study. There was no gender effect or order effect for the 2 solutions. The mean VAS score for warmed saline solution was 15 mm+/-15 mm (SD). The mean VAS score for room temperature saline was 34 mm+/-24 mm (SD), (95% confidence interval for difference of 19 mm [10 mm to 28 mm], P <.0001, Wilcoxon signed rank test).

CONCLUSION

Warmed saline solution was both clinically and statistically more comfortable than room temperature saline solution as an ocular irrigant among normal volunteers.

The physiological response to norepinephrine during hypothermia and rewarming

Our purpose was to determine if core hypothermia influences physiological responses to norepinephrine (NE); and if rewarming reverses these effects. Animals were instrumented to measure mean arterial pressure (MAP) and cardiac output (CO). Core temperature was manipulated from 37.5 degrees C (normothermia), to 30 degrees C (hypothermia) and the back to 37.5 degrees C (rewarming) using an external arterial-venous femoral shunt. At each of these temperatures, baseline CO and MAP were measured. Norepinephrine (NE) was infused at rates to deliver 0.2, 1.0, or 5 microg kg(-1) per h. At each dose CO and MAP was measured again. Systemic vascular resistance (SVR) was calculated using the formula (SVR = (MAP/CO) x 80). Eight animals underwent all three phases of the protocol. The response to NE during normothermia was a significant increase in MAP to doses of 1 microg kg(-1) per min (P < 0.01) and 5 microg kg(-1) per min (P < 0.01) and SVR to doses of 1 microg kg(-1) per min (P < 0.01) and 5 microg kg(-1) per min (P < 0.01). The response to NE during hypothermia was a significant increase in MAP only at doses of 1 microg kg(-1) per min (P = 0.03) and 5 microg kg(-1) per min (P = 0.01). The response to NE after rewarming was a significant increase in MAP only at a dose of 5 microg kg(-1) per min (P = 0.03). This study shows that core hypothermia causes a change in physiological response to NE that rewarming does not reverse.

Role of the plasminogen activator and matrix metalloproteinase systems in epidermal growth factor- and scatter factor-stimulated invasion of carcinoma cells

Normal as well as neoplastic cells traverse extracellular matrix barriers by mobilizing proteolytic enzymes in response to epidermal growth factor (EGF)-EGF receptor (EGFR) or hepatocyte growth factor/scatter factor (SF)-c-Met interactions. The plasminogen activator-plasminogen axis has been proposed to play a key role during cell invasion, but the normal development of plasminogen activator- as well as that of plasminogen-deficient mice supports the existence of alternate proteolytic systems that permit cells to traverse extracellular matrix barriers. To characterize the role that matrix-degrading proteinases play in EGF- or SF-stimulated invasion, a human squamous carcinoma cell line (UM-SCC-1) was triggered atop the matrices of type I collagen or human dermal explants in a three-dimensional culture system. During EGF- or SF-induced invasion, UM-SCC-1 cells expressed urokinase-type plasminogen activator (uPA) and uPA receptor as well as the matrix metalloproteinases (MMPs), membrane-type MMP-1, collagenase 1, stromelysin 1, and gelatinase B. Despite the presence of a positive correlation between uPA receptor-uPA expression and growth factor-stimulated invasion, UM-SCC-1 invasion was not affected by inhibitors directed against the plasminogen activator-plasminogen axis. In contrast, both recombinant and synthetic MMP inhibitors completely suppressed invasion by either EGF- or SF-stimulated cells without affecting either proteinase expression or cell motility across collagen-coated surfaces. These data demonstrate that MMPs, but not the plasminogen activator-plasmin system, can directly regulate the ability of either EGF- or SF-stimulated tumor cells to invade interstitial matrix barriers.

Matrix metalloproteinases regulate neovascularization by acting as pericellular fibrinolysins

During angiogenesis, endothelial cells penetrate fibrin barriers via undefined proteolytic mechanisms. We demonstrate that the fibrinolytic plasminogen activator (PA)-plasminogen system is not required for this process, since tissues isolated from PA- or plasminogen-deficient mice successfully neovascularize fibrin gels. By contrast, neovessel formation, in vitro and in vivo, is dependent on fibrinolytic, endothelial cell-derived matrix metalloproteinases (MMP). MMPs directly regulate this process as invasion-incompetent cells penetrate fibrin barriers when transfected with the most potent fibrinolytic metalloproteinase identified in endothelium, membrane type-1 MMP (MT1-MMP). Membrane display of MT1-MMP is required, as invasion-incompetent cells expressing a fibrinolytically active, transmembrane-deleted form of MT1-MMP remain noninvasive. These observations identify a PA-independent fibrinolytic pathway wherein tethered MMPs function as pericellular fibrinolysins during the neovascularization process.

Extraction and quantification of nicardipine in human plasma

A novel simple method of extraction, separation, identification and quantification of nicardipine in human plasma samples was completely studied. The human plasma samples were initially purified by solid-phase extraction (SPE) using a C18 cartridge. The extracted samples were separated and nicardipine present in the samples was quantified by high-performance liquid chromatography (HPLC) on a reversed-phase C18 column employing a mobile phase consisting of 60% (v/v) acetonitrile in 0.02 M NaH2PO4 with pH of 6.3 and a variable wavelength UV detector set at 254 nm. The recovery of nicardipine from plasma samples using selective SPE was 91+/-6.0% and had less interfering compounds in the HPLC analysis compared to the use of liquid-liquid (L/L) extraction. In the HPLC analysis, examining the effect of pH values of the mobile phase on the capacity factor (k') of nicardipine revealed a method for selecting a critical k' value of nicardipine to eliminate interfering peaks near the peak specific to the analyte. This method for quantification of nicardipine in human plasma samples was suitable for studying the pharmacokinetic profile of nicardipine administered as an intravenous bolus to cardiac surgical patients.

Preflight versus en route success and complications of rapid sequence intubation in an air medical service

BACKGROUND

Maintenance of an airway in the air medically transported patient is of paramount importance. The purpose of this study is to compare preflight versus en route rapid sequence intubation (RSI)-assisted intubations and to determine the value of air medical use of RSI.

METHODS

This study is a 31-month retrospective review of all patients intubated and transported by a large city air medical service. Subgroup analysis was based on whether patients were transported from a hospital or a scene and whether they were intubated preflight or en route. Information on age, Glasgow Coma Scale score, type of scene, ground time, and previous attempts at intubation was recorded. Complications included failures, multiple attempts at intubation, arrhythmias, and need for repeated paralytic agents. Comparisons were made using a confidence interval analysis. An alpha of 0.05 was considered significant; Bonferroni correction was used for multiple comparisons.

RESULTS

Three hundred twenty-five patients were intubated and transported by Lifeflight during the study period. Two hundred eighty-eight patients were intubated using RSI (89%). The success rate was 97%. Preflight intubations were performed on 100 hospital calls and 86 scene calls. En route intubations were performed on 40 hospital cases and 62 scene calls. Patients who underwent preflight intubations were significantly younger than those who underwent en route intubations for both the hospital group (34 +/- 11 vs. 44 +/- 24 years, p < 0.05) and the scene group (27 +/- 13 vs. 32 +/- 16 years,p < 0.05). Otherwise, the demographic characteristics of the four groups were similar. Trauma accounted for 60 to 70% of hospital transfers and almost 95 to 100% of scene calls. Compared with preflight intubations, there was a significant decrease in ground time for hospital patients who were intubated en route (26 +/- 10 vs. 34 +/- 11 minutes, p < 0.05) and for scene patients who were intubated en route (11 +/- 8 vs. 18 +/- 9 minutes, p < 0.05). There were no significant differences between the groups for number of failures (9 of 288), arrhythmias (18 of 288), or necessity for repeated paralysis (8 of 288). Multiple intubation attempts were performed in more scene preflight patients (30 of 86, 35%) than scene en route patients (16 of 62, 26%), but this did not reach statistical significance. Even for patients having previous attempts at intubation, the success rate using RSI was 93% (62 of 67).

CONCLUSION

Air medical intubations, both preflight and en route, for both scene calls and interhospital transports, can be done with a very high success rate. Rapid sequence intubation may improve the success rate. For scene calls, there was a significant decrease in ground time, and there was a trend toward fewer multiple intubation attempts when the patient was intubated en route instead of preflight.