Biomedical subjects

R J Lewis

Publications and source records attributed to R J Lewis.

At least 55 records · Page 3Linked to original sources

PubMed2001

Evaluation and management of children younger than two years old with apparently minor head trauma: proposed guidelines.

OBJECTIVE: In children <2 years old, minor head trauma (HT) is a common injury that can result in skull fracture and intracranial injury (ICI). These injuries can be difficult to detect in this age group; therefore, many authors recommend a low threshold for radiographic imaging. Currently, no clear guidelines exist regarding the evaluation and management of head-injured infants. We sought to develop guidelines for management based on data and expert opinion that would enable clinicians to identify children with complications of HT and reduce unnecessary imaging procedures. METHODS. EVIDENCE: References addressing pediatric HT were generated from a computerized database (Medline). The articles were reviewed and evidence tables were compiled. EXPERT PANEL: The multidisciplinary panel was comprised of nine experts in pediatric HT. CONSENSUS PROCESS: A modified Delphi technique was used to develop the guidelines. Before the one meeting, panel members reviewed the evidence and formulated answers to specific clinical questions regarding HT in young children. At the meeting, guidelines were formulated based on data and expert consensus. RESULTS: A management strategy was developed that categorizes children into 4 subgroups, based on risk of ICI. Children in the high-risk group should undergo a computed tomography (CT) scan. Those in the intermediate risk group with symptoms of possible ICI should either undergo CT scan or observation. Those in the intermediate risk group with some risk for skull fracture or ICI should undergo CT and/or skull radiographs or observation. Those in the low-risk group require no radiographic imaging. CONCLUSIONS: We have developed a guideline for the evaluation of children <2 years old with minor HT. The effect of these guidelines on clinical outcomes and resource utilization should be evaluated.

Brain Injuries↗

PubMed2001

An assessment of four solvents for the recovery of 2-chlorobenzylidenemalononitrile and capsaicins from "CS" and "Pepper" type lachrymator sprays, and an examination of their persistence on cotton fabric.

The rising incidence of assaults involving lachrymator sprays has led to an increase in items being submitted to this laboratory for the analysis of the associated chemical residues. The following work was undertaken to identify an efficient solvent with which to extract the compounds of interest from cotton fabric. The persistence and subsequent recovery of such compounds was also examined following protracted exposure to wind and rain. Ethyl acetate was established as the most efficient solvent of those examined for the extraction of 2-chlorobenzylidenemalononitrile and a range of capsaicins from "CS Gas" and '"Pepper" sprays respectively. Controlled experiments undertaken showed that capsaicins were recoverable after 72 h of exposure to the "elements" and 2-chlorobenzylidenemalononitrile was still recoverable after one week.

Journal Article↗

PubMed2001

The forensic examination of a fire-damaged vehicle.

The Lothian and Borders Police Forensic Science Laboratory was asked to assist in the investigation of a suspected fraudulent insurance claim involving a fire-damaged motor vehicle. This case demonstrates the persistence of fire accelerants when confined, and the reproducible nature of volatiles created from the accelerated burning of a synthetic material.

Journal Article↗

PubMed2000

Novel omega-conotoxins from Conus catus discriminate among neuronal calcium channel subtypes.

omega-Conotoxins selective for N-type calcium channels are useful in the management of severe pain. In an attempt to expand the therapeutic potential of this class, four new omega-conotoxins (CVIA-D) have been discovered in the venom of the piscivorous cone snail, Conus catus, using assay-guided fractionation and gene cloning. Compared with other omega-conotoxins, CVID has a novel loop 4 sequence and the highest selectivity for N-type over P/Q-type calcium channels in radioligand binding assays. CVIA-D also inhibited contractions of electrically stimulated rat vas deferens. In electrophysiological studies, omega-conotoxins CVID and MVIIA had similar potencies to inhibit current through central (alpha(1B-d)) and peripheral (alpha(1B-b)) splice variants of the rat N-type calcium channels when coexpressed with rat beta(3) in Xenopus oocytes. However, the potency of CVID and MVIIA increased when alpha(1B-d) and alpha(1B-b) were expressed in the absence of rat beta(3), an effect most pronounced for CVID at alpha(1B-d) (up to 540-fold) and least pronounced for MVIIA at alpha(1B-d) (3-fold). The novel selectivity of CVID may have therapeutic implications. (1)H NMR studies reveal that CVID possesses a combination of unique structural features, including two hydrogen bonds that stabilize loop 2 and place loop 2 proximal to loop 4, creating a globular surface that is rigid and well defined.

Alternative Splicing↗

PubMed2000

Ciguatera: recent advances but the risk remains.

Ciguatera is an important form of human poisoning caused by the consumption of seafood. The disease is characterised by gastrointestinal, neurological and cardiovascular disturbances. In cases of severe toxicity, paralysis, coma and death may occur. There is no immunity, and the toxins are cumulative. Symptoms may persist for months or years, or recur periodically. The epidemiology of ciguatera is complex and of central importance to the management and future use of marine resources. Ciguatera is an important medical entity in tropical and subtropical Pacific and Indian Ocean regions, and in the tropical Caribbean. As reef fish are increasingly exported to other areas, it has become a world health problem. The disease is under-reported and often misdiagnosed. Lipid-soluble, polyether toxins known as ciguatoxins accumulated in the muscles of certain subtropical and tropical marine finfish cause ciguatera. Ciguatoxins arise from biotransformation in the fish of less polar ciguatoxins (gambiertoxins) produced by Gambierdiscus toxicus, a marine dinoflagellate that lives on macroalgae, usually attached to dead coral. The toxins and their metabolites are concentrated in the food chain when carnivorous fish prey on smaller herbivorous fish. Humans are exposed at the end of the food chain. More than 400 species of fish can be vectors of ciguatoxins, but generally only a relatively small number of species are regularly incriminated in ciguatera. Ciguateric fish look, taste and smell normal, and detection of toxins in fish remains a problem. More than 20 precursor gambiertoxins and ciguatoxins have been identified in G. toxicus and in herbivorous and carnivorous fish. The toxins become more polar as they undergo oxidative metabolism and pass up the food chain. The main Pacific ciguatoxin (P-CTX-1) causes ciguatera at levels=0.1 microg/kg in the flesh of carnivorous fish. The main Caribbean ciguatoxin (C-CTX-1) is less polar and 10-fold less toxic than P-CTX-1. Ciguatoxins activate sodium ion (Na ) channels, causing cell membrane excitability and instability. Worldwide coral bleaching is now well documented, and there is a strong association between global warming and the bleaching and death of coral. This, together with natural environmental factors such as earthquakes and hurricanes, and man-made factors such as tourism, dock construction, sewage and eutrophication, may create more favourable environments for G. toxicus. While low levels of G. toxicus are found throughout tropical and subtropical waters, the presence of bloom numbers is unpredictable and patchy. Only certain genetic strains produce ciguatoxins, and environmental triggers for increasing toxin production are unknown.

Acute Disease↗

PubMed2000

Structure of a slow processing precursor penicillin acylase from Escherichia coli reveals the linker peptide blocking the active-site cleft.

Penicillin G acylase is a periplasmic protein, cytoplasmically expressed as a precursor polypeptide comprising a signal sequence, the A and B chains of the mature enzyme (209 and 557 residues respectively) joined by a spacer peptide of 54 amino acid residues. The wild-type AB heterodimer is produced by proteolytic removal of this spacer in the periplasm. The first step in processing is believed to be autocatalytic hydrolysis of the peptide bond between the C-terminal residue of the spacer and the active-site serine residue at the N terminus of the B chain. We have determined the crystal structure of a slowly processing precursor mutant (Thr263Gly) of penicillin G acylase from Escherichia coli, which reveals that the spacer peptide blocks the entrance to the active-site cleft consistent with an autocatalytic mechanism of maturation. In this mutant precursor there is, however, an unexpected cleavage at a site four residues from the active-site serine residue. Analyses of the stereochemistry of the 260-261 bond seen to be cleaved in this precursor structure and of the 263-264 peptide bond have suggested factors that may govern the autocatalytic mechanism.

Binding Sites↗

PubMed2000

A new mutation in spo0A with intragenic suppressors in the effector domain.

Spo0A is a two domain response regulator, a key protein in the initiation of sporulation of Bacillus subtilis. This protein controls a number of changes in gene expression that occur during the transition from stationary phase to the onset of sporulation. The phosphorylated form of Spo0A influences the transcription of a specific set of genes. In addition to others, it represses abrB and activates spoIIA and spoIIE transcription. Although the N-terminal phosphoacceptor domain is well characterised, there is limited information on the C-terminal, DNA-binding domain. Comparisons of Spo0A homologues from a number of Bacillus and Clostridium species show that the C-terminal domain contains three highly conserved regions. In this study, we have investigated the influence of spo0A mutations mapping within the C-terminal domain on transcription from the abrB, spoIIA and spoIIE promoters using lacZ fusions. Our results indicate that described mutations can be part of signalling between N- and C-terminal domains of the protein. Also, the increased expression observed from the spoIIE promoter in some Spo0A mutants might result from a stabilising function of these mutations on the transcriptional apparatus utilising sigma(A).

Amino Acid Sequence↗

PubMed2000

Domain swapping in the sporulation response regulator Spo0A.

Adaptive responses of micro-organisms, such as chemotaxis and sporulation, are governed by two-component systems consisting of sensor kinases, that interpret environmental signals, and response regulators which activate the appropriate physiological responses. Signal transduction via response regulator proteins is mediated through transient phosphorylation of aspartic acid residues. In Spo0A, the key regulator of development (sporulation) in Bacillus, phosphorylation of the N-terminal receiver domain (N-Spo0A) at aspartate-55 switches on the transcription activation functions residing in the C-terminal effector domain. Here we report the crystal structure of N-Spo0A from Bacillus stearothermophilus at 1.6 A spacing, revealing a dimer formed by an alpha-helix swap. Comparison of this structure with the recently described structure of phosphorylated N-Spo0A shows that dimer formation results from a cis-trans isomerization of the Lys106--Pro107 peptide bond. The quaternary reorganization is associated with alterations in the active site stereochemistry which may have implications for signalling. Remarkably, this 3-D domain swapped N-Spo0A dimer has an identical topology to a hypothetical CheY-like dimer, recently proposed as an intermediate in the evolution of the family of periplasmic substrate binding proteins.

Amino Acid Sequence↗

PubMed2000

Effect of out-of-hospital pediatric endotracheal intubation on survival and neurological outcome: a controlled clinical trial.

CONTEXT: Endotracheal intubation (ETI) is widely used for airway management of children in the out-of-hospital setting, despite a lack of controlled trials demonstrating a positive effect on survival or neurological outcome. OBJECTIVE: To compare the survival and neurological outcomes of pediatric patients treated with bag-valve-mask ventilation (BVM) with those of patients treated with BVM followed by ETI. DESIGN: Controlled clinical trial, in which patients were assigned to interventions by calendar day from March 15, 1994, through January 1, 1997. SETTING: Two large, urban, rapid-transport emergency medical services (EMS) systems. PARTICIPANTS: A total of 830 consecutive patients aged 12 years or younger or estimated to weigh less than 40 kg who required airway management; 820 were available for follow-up. INTERVENTIONS: Patients were assigned to receive either BVM (odd days; n = 410) or BVM followed by ETI (even days; n = 420). MAIN OUTCOME MEASURES: Survival to hospital discharge and neurological status at discharge from an acute care hospital compared by treatment group. RESULTS: There was no significant difference in survival between the BVM group (123/404 [30%]) and the ETI group (110/416 [26%]) (odds ratio [OR], 0.82; 95% confidence interval [CI], 0.61-1.11) or in the rate of achieving a good neurological outcome (BVM, 92/404 [23%] vs ETI, 85/416 [20%]) (OR, 0.87; 95% CI, 0.62-1.22). CONCLUSION: These results indicate that the addition of out-of-hospital ETI to a paramedic scope of practice that already includes BVM did not improve survival or neurological outcome of pediatric patients treated in an urban EMS system.

Allied Health Personnel↗

PubMed2000

Simplified admission criterion for predicting severe complications of gallstone pancreatitis.

HYPOTHESIS: Simple admission criteria (white blood cell count, > or =14. 5 x 10(9)/L; blood urea nitrogen level, > or =4.3 mmol/L [> or =12 mg/dL]; heart rate, > or =100 beats per minute; and serum glucose level, > or =8.3 mmol/L [> or =150 mg/dL]) are better predictors of severe complications of gallstone pancreatitis than an Acute Physiology and Chronic Health Evaluation II (APACHE II) score of 5 or greater, a modified Imrie (Glasgow) score of 3 or greater, and a biliary Ranson score of 3 or greater. DESIGN: A prospective consecutive case study. SETTING: A university-affiliated, urban, public hospital. PATIENTS: Ninety-two consecutive patients (77 women and 15 men, aged 18 to 76 years [mean age, 39 years]) with gallstone pancreatitis. Seventy-seven patients were Hispanic. MAIN OUTCOME MEASURES: Major local and systemic complications requiring intensive care unit care, and death. RESULTS: Fourteen patients (15%) had severe complications with a mortality of 2%. On univariate analysis, a white blood cell count of 14.5 x 10(9)/L or more (P =.03), a serum glucose level of 8. 3 mmol/L or more (> or =150 mg/dL) (P<.001), an APACHE II score of 5 or greater (P =.008), a modified Imrie score of 3 or greater (P<.001), and a biliary Ranson score of 3 or greater (P =.03) were statistically associated with the development of severe complications; whereas a blood urea nitrogen level of 4.3 mmol/L or more (> or =12 mg/dL) and a heart rate of 100 beats per minute or more were not. On multivariate analysis, only a serum glucose level of 8. 3 mmol/L or more (> or =150 mg/dL) was predictive of adverse events (P<. 001). CONCLUSIONS: Glucose level (> or =8.3 mmol/L [> or =150 mg/dL]) is the best single admission predictor of severe complications of gallstone pancreatitis and is superior to an APACHE II score of 5 or greater, a modified Imrie score of 3 or greater, and a biliary Ranson score of 3 or greater.

Acute Disease↗

PubMed2000

Nonoperative management of perforated appendicitis without periappendiceal mass.

BACKGROUND: Initial nonoperative treatment for patients with periappendiceal mass has been shown to be safe and effective. Our goal was to evaluate the safety and efficacy of initial nonoperative management for perforated appendicitis not accompanied by a palpable mass. METHODS: The study population consisted of 77 patients with appendicitis treated initially nonoperatively between 1992 and 1998. All had localized abdominal tenderness and computed tomography findings of abscess or phlegmon. None had a palpable abdominal mass. Outcome parameters evaluated were rate of failure, complication, and recurrence. RESULTS: There were 49 males and 28 females with a mean age of 35 years (range 16 to 75). Initial nonoperative management was successful in 95% of patients. Complications occurred in 12% of patients. Recurrent appendicitis developed in 6.5% of patients after an average follow-up of 30 weeks. CONCLUSIONS: Perforated appendicitis patients with localized abdominal tenderness and abscess or phlegmon can safely and effectively be treated in an initial nonoperative fashion.

Abdominal Abscess↗

PubMed2000

Video-assisted thoracic surgery resection of chest wall en bloc for lung carcinoma.

A video-assisted thoracic surgery approach to en bloc resection of lung cancer invading the chest wall is described. Using a minimally invasive surgical approach combined with neoadjuvant external beam radiotherapy, complete resection of an upper lobe carcinoma invading two rib segments was performed in a manner that permitted complete resection with curative intent and allowed for rapid recovery.

Carcinoma, Non-Small-Cell Lung↗

PubMed2000

Implementation of an emergency department triage procedure for the detection and isolation of patients with active pulmonary tuberculosis.

STUDY OBJECTIVES: To investigate the ability of an emergency department screening protocol to initiate respiratory isolation of patients with pulmonary tuberculosis at ED triage before chest radiography. METHODS: We conducted a prospective cohort study with retrospective medical record review of adult patients who presented for care to an urban, university-affiliated hospital in Los Angeles County over a 4-month period. Ambulatory patients were administered a triage screening protocol that used patient-reported tuberculosis risk factors and symptoms in combination with selective chest radiography to screen patients at ED triage for active pulmonary tuberculosis. RESULTS: A total of 10,674 patients were screened; 2, 218 were isolated at triage and underwent chest radiography, and 378 were kept in isolation in the ED. The respiratory isolation of pulmonary tuberculosis (RIPT) protocol detected 17 of 27 visits made by patients with unsuspected pulmonary tuberculosis, yielding a sensitivity of 63% (95% confidence interval [CI] 42% to 81%). The estimated specificity was 78%. For each patient with tuberculosis who was detected by the RIPT protocol, 624 patients were screened at triage, 130 chest radiographs were taken, and 22 patients were placed in respiratory isolation in the ED. Patients with undetected pulmonary tuberculosis more commonly had nonpulmonary chief complaints (76% versus 20%; odds ratio [OR] 13, 95% CI 2.1 to 78.3), and only 60% (95% CI 26% to 88%) were ultimately isolated in the hospital. Among RIPT screen-positive patients, radiographic findings predictive of pulmonary tuberculosis were cavitary lesions (OR 84.3, 95% CI 22.6 to 315), upper lobe infiltrates (OR 24.2, 95% CI 9.1 to 64.4), pleural effusions (OR 8.9, 95% CI 2.5 to 31.8), diffuse/interstitial infiltrates (OR 5.7, 95% CI 1.8 to 17.9), and non-upper lobe infiltrates (OR 3.1, 95% CI 1.0 to 9.5). CONCLUSION: The RIPT screening protocol was only moderately sensitive for isolating patients with pulmonary tuberculosis at ED triage. Future studies should evaluate modified and abridged screening protocols, as well as the cost-effectiveness of triage screening.

Adult↗

PubMed2000

Transthoracic monophasic and biphasic defibrillation in a swine model: a comparison of efficacy, ST segment changes, and postshock hemodynamics.

OBJECTIVE: Biphasic waveforms for transthoracic defibrillation (DF) have been tested extensively after brief (15 s) episodes of VF in animal models and in patients undergoing electrophysiologic testing. The purpose of this study was to compare the effects mono- and biphasic waveforms for DF on postdefibrillation ST segments and left ventricular pressure, markers of myocardial injury, after more extended periods of VF (30 and 90 s). METHODS: 21 anesthetized and instrumented swine were randomized to truncated exponential monophasic or biphasic waveform DF. VF was induced electrically and 30 s later, DF with the designated waveform was attempted with a shock dose of 200 J. If unsuccessful, 300 J and then 360 J were administered if necessary. Following return to control hemodynamic values and normalization of the surface ECG, VF was again induced and, after 90 s, DF was attempted as in the 30 s VF period. CPR was not performed during VF and each animal was countershocked with only one waveform for both VF episodes. Waveforms were compared for frequency of first shock defibrillation success, surface ECG indicators of myocardial injury (ST segment changes at 10, 20, and 30 s after countershock) and time to return to pre-VF hemodynamics after successful DF, an indicator of postshock ventricular function. RESULTS: Successful first shock conversion rates at 30 and 90 s were 60 and 63% for monophasic and 64 and 82% for biphasic (NS). Biphasic DF after 30 s produced ST segment changes (measured 10 s after DF) in 1/10 animals while six of eight animals in the monophasic group showed ST segment changes (P=0.013). After 90 s of VF, ST segment changes were observed in 6/8 in the monophasic group and 2/10 in the biphasic group (P=0.054). Differences in the time to hemodynamic recovery (return to control peak left ventricular pressure) were not observed between biphasic and monophasic waveforms after 30 or 90 s of VF. CONCLUSIONS: Monophasic and biphasic transthoracic defibrillation are equally effective in terminating VF of 30 and 90 s duration and restoring a perfusing rhythm. The biphasic waveform produced less ECG evidence of transient myocardial injury. However, there was no difference in the rate of return to control hemodynamics. ST segment changes following countershock of VF of brief duration are transient and of questionable significance.

Animals↗

PubMed2000

Monophasic versus biphasic transthoracic countershock after prolonged ventricular fibrillation in a swine model.

OBJECTIVE: We sought to compare the defibrillation efficacy of a low-energy biphasic truncated exponential (BTE) waveform and a conventional higher-energy monophasic truncated exponential (MTE) waveform after prolonged ventricular fibrillation (VF). BACKGROUND: Low energy biphasic countershocks have been shown to be effective after brief episodes of VF (15 to 30 s) and to produce few postshock electrocardiogram abnormalities. METHODS: Swine were randomized to MTE (n = 18) or BTE (n = 20) after 5 min of VF. The first MTE shock dose was 200 J, and first BTE dose 150 J. If required, up to two additional shocks were administered (300, 360 J MTE; 150, 150 J BTE). If VF persisted manual cardiopulmonary resuscitation (CPR) was begun, and shocks were administered until VF was terminated. Successful defibrillation was defined as termination of VF regardless of postshock rhythm. If countershock terminated VF but was followed by a nonperfusing rhythm, CPR was performed until a perfusing rhythm developed. Arterial pressure, left ventricular (LV) pressure, first derivative of LV pressure and cardiac output were measured at intervals for 60 min postresuscitation. RESULTS: The odds ratio of first-shock success with BTE versus MTE was 0.67 (p = 0.55). The rate of termination of VF with the second or third shocks was similar between groups, as was the incidence of postshock pulseless electrical activity (15/18 MTE, 18/20 BTE) and CPR time for those animals that were resuscitated. Hemodynamic variables were not significantly different between groups at 15, 30 and 60 min after resuscitation. CONCLUSIONS: Monophasic and biphasic waveforms were equally effective in terminating prolonged VF with the first shock, and there was no apparent clinical disadvantage of subsequent low-energy biphasic shocks compared with progressive energy monophasic shocks. Lower-energy shocks were not associated with less postresuscitation myocardial dysfunction.

Animals↗

PubMed2000

The trans-activation domain of the sporulation response regulator Spo0A revealed by X-ray crystallography.

Sporulation in Bacillus involves the induction of scores of genes in a temporally and spatially co-ordinated programme of cell development. Its initiation is under the control of an expanded two-component signal transduction system termed a phosphorelay. The master control element in the decision to sporulate is the response regulator, Spo0A, which comprises a receiver or phosphoacceptor domain and an effector or transcription activation domain. The receiver domain of Spo0A shares sequence similarity with numerous response regulators, and its structure has been determined in phosphorylated and unphosphorylated forms. However, the effector domain (C-Spo0A) has no detectable sequence similarity to any other protein, and this lack of structural information is an obstacle to understanding how DNA binding and transcription activation are controlled by phosphorylation in Spo0A. Here, we report the crystal structure of C-Spo0A from Bacillus stearothermophilus revealing a single alpha-helical domain comprising six alpha-helices in an unprecedented fold. The structure contains a helix-turn-helix as part of a three alpha-helical bundle reminiscent of the catabolite gene activator protein (CAP), suggesting a mechanism for DNA binding. The residues implicated in forming the sigmaA-activating region clearly cluster in a flexible segment of the polypeptide on the opposite side of the structure from that predicted to interact with DNA. The structural results are discussed in the context of the rich array of existing mutational data.

Amino Acid Sequence↗

PubMed2000

Conotoxin TVIIA, a novel peptide from the venom of Conus tulipa 1. Isolation, characterization and chemical synthesis.

A novel conotoxin belonging to the 'four-loop' structural class has been isolated from the venom of the piscivorous cone snail Conus tulipa. It was identified using a chemical-directed strategy based largely on mass spectrometric techniques. The new toxin, conotoxin TVIIA, consists of 30 amino-acid residues and contains three disulfide bonds. The amino-acid sequence was determined by Edman analysis as SCSGRDSRCOOVCCMGLMCSRGKCVSIYGE where O = 4-transL-hydroxyproline. Two under-hydroxylated analogues, [Pro10]TVIIA and [Pro10,11]TVIIA, were also identified in the venom of C. tulipa. The sequences of TVIIA and [Pro10]TVIIA were further verified by chemical synthesis and coelution studies with native material. Conotoxin TVIIA has a six cysteine/four-loop structural framework common to many peptides from Conus venoms including the omega-, delta- and kappa-conotoxins. However, TVIIA displays little sequence homology with these well-characterized pharmacological classes of peptides, but displays striking sequence homology with conotoxin GS, a peptide from Conus geographus that blocks skeletal muscle sodium channels. These new toxins and GS share several biochemical features and represent a distinct subgroup of the four-loop conotoxins.

Amino Acid Sequence↗

PubMed2000

Immediate countershock versus cardiopulmonary resuscitation before countershock in a 5-minute swine model of ventricular fibrillation arrest.

STUDY OBJECTIVE: Prior laboratory and clinical studies demonstrate that cardiopulmonary resuscitation (CPR) preceding countershock of prolonged ventricular fibrillation (VF) increases the likelihood of successful cardiac resuscitation. The lower limit of VF duration at which time preshock CPR provides no benefit has not been specifically studied. The purpose of this study was to compare countershock and cardiac resuscitation outcome between immediate countershock of VF of 5-minute duration and CPR without drug therapy before countershock in a swine model. METHODS: VF was induced in anesthetized and instrumented swine. After 5 minutes of VF, animals received 1 of 2 treatments. Animals in group 1, a "historical" control group (n=20), received immediate countershock followed by CPR and repeated shocks if needed. Group 2 animals (n=11) received CPR for 90 seconds preceding countershock, then continued CPR and repeated countershock if necessary. Drugs were not administered to either group, and resuscitation efforts were discontinued if a perfusing rhythm was not restored within 10 minutes of the first countershock. First shock success rate (defined as termination of VF), the number of shocks required to terminate VF, and the cardiac resuscitation rate were compared between groups. RESULTS: The first shock terminated VF in 13 of 20 group 1 animals and 2 of 11 group 2 animals (P =.023). All but 1 animal in group 1 developed pulseless electrical activity after countershock. All but 1 animal in group 1 were eventually successfully resuscitated with CPR and repeated shocks if necessary. Four group 2 animals could not be resuscitated (P =.042). CONCLUSION: Although effective in improving outcome of prolonged VF, CPR preceding countershock of VF of 5-minute duration does not improve the response to the first shock, decrease the incidence of postshock pulseless electrical activity, or the rate of return of circulation. In this study, CPR preceding countershock resulted in a significantly lower cardiac resuscitation rate.

Animals↗