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Biomedical subjects

R A Berg

Publications and source records attributed to R A Berg.

At least 37 records · Page 2Linked to original sources
PubMed1999

Simulated mouth-to-mouth ventilation and chest compressions (bystander cardiopulmonary resuscitation) improves outcome in a swine model of prehospital pediatric asphyxial cardiac arrest.

OBJECTIVE: To compare the efficacy of four methods of simulated single-rescuer bystander cardiopulmonary resuscitation (CPR) in a clinically relevant swine model of prehospital pediatric asphyxial cardiac arrest. DESIGN: Prospective, randomized study. SUBJECTS: Thirty-nine anesthetized domestic piglets. INTERVENTIONS: Asphyxial cardiac arrest was produced by clamping the endotracheal tubes of the piglets. For 8 mins of simulated bystander CPR, animals were randomly assigned to the following groups: group 1, chest compressions and simulated mouth-to-mouth ventilation (FI(O2) = 0.17, FI(CO2) = 0.04) (CC+V); group 2, chest compressions only (CC); group 3, simulated mouth-to-mouth ventilation only (V); and group 4, no CPR (control group). Standard advanced life support was then provided, simulating paramedic arrival. Animals that were successfully resuscitated received 1 hr of intensive care support and were observed for 24 hrs. MEASUREMENTS AND MAIN RESULTS: Electrocardiogram, aortic blood pressure, right atrial blood pressure, and end-tidal CO2 were monitored continuously until the intensive care period ended. Arterial and mixed venous blood gases were measured at baseline, 1 min after cardiac arrest, and 7 mins after cardiac arrest. Minute ventilation was determined during each minute of bystander CPR. Survival and neurologic outcome were determined. Twenty-four-hour survival was attained in eight of 10 group 1 (CC+V) piglets vs. three of 14 group 2 (CC) piglets (p < or = .01), one of seven group 3 (V) piglets (p < or = .05), and two of eight group 4 (control) piglets (p < or = .05). Twenty-four-hour neurologically normal survival occurred in seven of 10 group 1 (CC+V) piglets vs. one of 14 group 2 (CC) piglets (p < or = .01), one of seven group 3 (V) piglets (p < or = .05), and none of eight group 4 (control) piglets (p < or = .01). Arterial oxygenation and pH were markedly better during CPR in group 1 than in group 2. Within 5 mins of bystander CPR, six of 10 group 1 (CC+V) piglets attained sustained return of spontaneous circulation vs. only two of 14 group 2 (CC) piglets and none of the piglets in the other two groups (p < or = .05 for all groups). CONCLUSIONS: In this pediatric asphyxial model of prehospital single-rescuer bystander CPR, chest compressions plus simulated mouth-to-mouth ventilation improved systemic oxygenation, coronary perfusion pressures, early return of spontaneous circulation, and 24-hr survival compared with the other three approaches.

Analysis of Variance↗
PubMed1998

Severe ventilatory compromise due to gastric distention during pediatric cardiopulmonary resuscitation.

We describe a child in cardiac arrest with severe ventilatory compromise due to gastric distention. During cardiopulmonary resuscitation (CPR), positive pressure ventilation may lead to gastric insufflation because of decreased pulmonary compliance and decreased lower esophageal sphincter tone. Essentially, gas delivered will follow the path of least resistance, which may be to the stomach. In our patient, gastric distention precluded effective ventilation and gastric decompression relieved ventilatory compromise. The values and pitfalls of clinical evaluation and capnography are presented.

Cardiopulmonary Resuscitation↗
PubMed1998

Efficacy of chest compression-only BLS CPR in the presence of an occluded airway.

Reluctance of the lay public to perform bystander CPR is becoming an increasingly worrisome problem in the USA. Most bystanders who admit such reluctance concede that fear of contagious disease from mouth-to-mouth contact is what keeps them from performing basic life support. Animal models of prehospital cardiac arrest indicates that 24-h survival is essentially as good with chest compression-only CPR as with chest compressions and assisted ventilation. This simpler technique is an attractive alternative strategy for encouraging more bystander participation. Such experimental studies have been criticized as irrelevant however secondary to differences between human and porcine airway mechanics. This study examined the effect of chest compression-only CPR under the worst possible circumstances where the airway was totally occluded. After 6 min of either standard CPR including ventilation with a patent airway or chest compressions-only with a totally occluded airway, no difference in 24 h survival was found (10/10 vs. 9/10). As anticipated arterial blood gases were not as good, but hemodynamics produced were better with chest compression-only CPR (P < 0.05). Chest compression-only CPR, even with a totally occluded airway, is as good as standard CPR for successful outcome following 6.5 min of cardiac arrest. Such a strategy for the first minutes of cardiac arrest, particularly before professional help arrives, has several advantages including increased acceptability to the lay public.

Airway Obstruction↗
PubMed1998

Intravascular hemolysis associated with North American crotalid envenomation.

CASE REPORT: This is a case of severe intravascular hemolysis, without significant coagulopathy, following envenomation by a North American crotalid. A MEDLINE search from 1966-1997, and a review of older literature, revealed no similar cases. A 4-year-old girl was envenomated in her right foot by a 2.5 foot-long rattlesnake whose description matched that of the Hopi rattlesnake (Crotalus viridis nuntius). The snake was not captured. Her initial hematocrit was 45%. In spite of treatment with antivenin and improvement in her lower extremity pain and swelling, her hematocrit decreased to 20.4%. Laboratory tests and clinical exam showed a Coombs positive hemolytic anemia without significant signs of coagulopathy.

Anemia, Hemolytic↗
PubMed1997

Assisted ventilation during 'bystander' CPR in a swine acute myocardial infarction model does not improve outcome.

BACKGROUND: Mouth-to-mouth rescue breathing is a barrier to the performance of bystander cardiopulmonary resuscitation (CPR). We evaluated the need for assisted ventilation during simulated single-rescuer bystander CPR in a swine myocardial infarction model of prehospital cardiac arrest. METHODS AND RESULTS: Steel cylinders were placed in the mid left anterior descending coronary arteries of 43 swine. Two minutes after ventricular fibrillation, animals were randomly assigned to 10 minutes of hand-bag-valve ventilation with 17% oxygen and 4% carbon dioxide plus chest compressions (CC+V), chest compressions only (CC), or no CPR (control group). Standard advanced life support was then provided. Animals successfully resuscitated received 1 hour of intensive care support and were observed for 24 hours. Five of 14 CC animals, 3 of 15 CC+V animals, and 1 of 14 controls survived for 24 hours (CC versus controls, P=.07). Myocardial oxygen delivery and consumption were greater among surviving animals than nonsurvivors but did not differ between CC and CC+V animals. CONCLUSIONS: In this acute myocardial infarction model of prehospital single-rescuer bystander CPR, assisted ventilation did not improve outcome.

Animals↗
PubMed1997

Postresuscitation left ventricular systolic and diastolic dysfunction. Treatment with dobutamine.

BACKGROUND: Global left ventricular dysfunction after successful resuscitation is well documented and appears to be a major contributing factor in limiting long-term survival after initial recovery from out-of-hospital sudden cardiac death. Treatment of such postresuscitation myocardial dysfunction has not been examined previously. METHODS AND RESULTS: Systolic and diastolic parameters of left ventricular function were measured in 27 swine before and after successful resuscitation from prolonged ventricular fibrillation cardiac arrest. Dobutamine infusions (10 micrograms.kg-1.min-1 in 14 animals or 5 micrograms.kg-1.min-1 in 5 animals) begun 15 minutes after resuscitation were compared with controls receiving no treatment (8 animals). The marked deterioration in systolic and diastolic left ventricular function seen in the control group after resuscitation was ameliorated in the dobutamine-treated animals. Left ventricular ejection fraction fell from a prearrest 58 +/- 3% to 25 +/- 3% at 5 hours after resuscitation in the control group but remained unchanged in the dobutamine (10 micrograms.kg-1.min-1) group (52 +/- 1% prearrest and 55 +/- 3% at 5 hours after resuscitation). Measurement of the constant of isovolumic relaxation of the left ventricle (tau) demonstrated a similar benefit of the dobutamine infusion for overcoming postresuscitation diastolic dysfunction. The tau rose in the controls from 28 +/- 1 milliseconds (ms) prearrest to 41 +/- 3 ms at 5 hours after resuscitation whereas it remained constant in the dobutamine-treated animals (31 +/- 1 ms prearrest and 31 +/- 5 ms at 5 hours after resuscitation). CONCLUSIONS: Dobutamine begun within 15 minutes of successful resuscitation can successfully overcome the global systolic and diastolic left ventricular dysfunction resulting from prolonged cardiac arrest and cardiopulmonary resuscitation.

Animals↗
PubMed1997

Assisted ventilation does not improve outcome in a porcine model of single-rescuer bystander cardiopulmonary resuscitation.

BACKGROUND: Mouth-to-mouth rescue breathing is a barrier to the performance of bystander cardiopulmonary resuscitation (CPR). We evaluated the need for assisted ventilation during simulated single-rescuer bystander CPR in a swine model of prehospital cardiac arrest. METHODS AND RESULTS: Five minutes after ventricular fibrillation, swine were randomly assigned to 8 minutes of hand-bag-valve ventilation with 17% oxygen and 4% carbon dioxide plus chest compressions (CC + V), chest compressions only (CC), or no CPR (control group). Standard advanced life support was then provided. Animals successfully resuscitated received 1 hour of intensive care support and were observed for 24 hours. All 10 CC animals, 9 of the 10 CC + V animals, and 4 of the 6 control animals attained return of spontaneous circulation. Five of the 10 CC animals, 6 of the 10 CC + V animals, and none of the 6 control animals survived for 24 hours (CC versus controls, P = .058; CC + V versus controls, P < .03). All 24-hour survivors were normal or nearly normal neurologically. CONCLUSIONS: In this model of prehospital single-rescuer bystander CPR, successful initial resuscitation, 24-hour survival, and neurological outcome were similar after chest compressions only or chest compressions plus assisted ventilation. Both techniques tended to improve outcome compared with no bystander CPR.

Animals↗
PubMed1997

Sulfoconjugation and renal excretion contribute to the interpatient variation of exogenous catecholamine clearance in critically ill children.

OBJECTIVE: To delineate the contributions of sulfoconjugation, renal excretion, and patient age to the wide interpatient variability in exogenous dobutamine and dopamine plasma clearance. DESIGN: Simultaneous plasma free and sulfoconjugated dobutamine and/or dopamine, respective urine free catecholamine, and serum creatinine were determined on stable critically ill children receiving unchanged continuous infusions of dobutamine and/or dopamine for at least 1 hr. Free dobutamine and dopamine clearance rates were calculated. SETTING: Pediatric and neonatal intensive care units in university settings. PATIENTS: Forty-seven stable critically ill neonates and children. INTERVENTIONS: Continuous infusions of dobutamine and/or dopamine: nine patients received dopamine only, 27 patients received dobutamine only, and 11 patients received both simultaneously. MEASUREMENTS AND MAIN RESULTS: Fractions of plasma dobutamine and dopamine sulfoconjugated were 0.73 +/- 0.05 and 0.76 +/- 0.05, respectively. Free plasma dobutamine and dopamine clearances were 102 +/- 15 mL/kg/min and 250 +/- 38 mL/kg/min, respectively. Linear regression analyses demonstrated relationships of the fraction of plasma dobutamine and dopamine sulfoconjugated to the respective free plasma clearances (r2 = .30, p < .01, and r2 = 0.29, p < .01, respectively), and, more impressively, to the natural logarithm of the respective free plasma clearances (r2 = 0.58, p < .001, and r2 = 0.39, p < .01). Patients with serum creatinine concentrations >2 mg/dL had lower free plasma dobutamine and dopamine clearance rates than those patients with serum creatinine of <2 mg/dL (6 +/- 1 vs. 107 +/- 15 mL/kg/min for dobutamine and 40 +/- 38 vs. 270 +/- 39 mL/kg/min for dopamine, respectively, p < .05 for both by Mann-Whitney U test). No relationship was noted between free catecholamine clearance and age. CONCLUSION: Sulfoconjugation and renal excretion are important determinants of the wide interpatient variability in plasma free dobutamine and dopamine clearance rates.

Adolescent↗
PubMed1997

Evaluation of artecoll polymethylmethacrylate implant for soft-tissue augmentation: biocompatibility and chemical characterization.

Artecoll polymethylmethacrylate implant (Artecoll) is a combination of polymethylmethacrylate beads suspended in 3.5% atelocollagen and has been designed for use in soft-tissue augmentation applications. The biocompatibility and immunogenicity of Artecoll were evaluated to assess the safety of this product for use in the dermis. To characterize the collagen component, chemical analysis was performed including trypsin sensitivity, differential scanning calorimetry, and pepsin content. Particle size analysis was also performed on the polymethylmethacrylate beads. The ability of this material to elicit an immunologic response was measured in a sensitized and nonsensitized guinea pig intradermal model. In these studies, 24 guinea pigs were injected intradermally with either Artecoll or Zyderm, a bovine collagen product for soft-tissue augmentation. Six sites were evaluated for each material at 3, 7, and 28 days after injection. In the sensitized model, 60 guinea pigs were divided into five groups, and each group received a sensitizing dose (in conjunction with Freund's adjuvant) of Zyderm, Artecoll, or a nonsensitizing dose of the same materials. The fifth group served as a nontreatment control. After the animals were sensitized, they were challenged with intradermal injections of various antigens to evaluate delayed type hypersensitivity reactions. Chemical characterization indicated polymethylmethacrylate beads of varying sizes, including many less than 35 microns, and a vehicle of extensively denatured and impure collagen. In vivo evaluations indicated that Artecoll elicited an immune response in guinea pigs, including delayed type hypersensitivity and antibody reactions. Histological assessment demonstrated particle phagocytosis and transepidermal elimination. Following immunization with Artecoll, guinea pigs were also found to be sensitized to pepsin, an impurity found in the collagen carrier. The biocompatibility of this material was compared with that of bovine dermal collagen (Zyderm collagen implant), which is widely used and accepted as biocompatible. The results of this evaluation indicate that Artecoll polymethylmethacrylate implant has the potential to elicit an immune response in humans, and polymethylmethacrylate beads are susceptible to phagocytosis and elimination.

Adjuvants, Immunologic↗
PubMed1996

Development of a skin model based on insoluble fibrillar collagen.

A biocompatible, 3-dimensional, noncontracting, crosslinked collagen matrix was adapted to promote differentiation of epidermal keratinocytes. To produce the matrix, a 3% wt/wt dispersion of insoluble bovine collagen containing 5 mg polylysine/g collagen in 0.001 N HCl was blended, lyophilized, and crosslinked using a dehydrothermal technique. Matrices 4 cm2 and 3 mm thick were seeded with human dermal fibroblasts (1 x 10(5)/cm2). After 5 days in culture, the matrices were seeded with human epidermal keratinocytes (1 x 10(5)/cm2). The cultures were grown submerged for 1 week and raised to the liquid/air interface for 3 weeks to promote epidermal differentiation. Based on morphology and immunological staining with antibodies for human involucrin, keratin 1 (k1), filaggrin, and loricrin, the state of differentiation of the epidermal layer was nearly equivalent to that seen with cultures grown on contracted collagen lattices produced according to the methodology described in the literature and similar to the pattern produced in normal neonatal foreskin. These results demonstrate the usefulness of an in vitro skin model employing a crosslinked collagen matrix that permits the incorporation of additional covalently linked bioactive molecules during matrix formation.

Biocompatible Materials↗
PubMed1996

Myocardial dysfunction after resuscitation from cardiac arrest: an example of global myocardial stunning.

OBJECTIVES: This study investigated the effect of prolonged cardiac arrest and subsequent cardiopulmonary resuscitation on left ventricular systolic and diastolic function. BACKGROUND: Cardiac arrest from ventricular fibrillation results in cessation of forward blood flow, including myocardial blood flow. During cardiopulmonary resuscitation, myocardial blood flow remains suboptimal. Once the heart is defibrillated and successful resuscitation achieved, reversible myocardial dysfunction, or "stunning," may occur. The magnitude and time course of myocardial stunning from cardiac arrest is unknown. METHODS: Twenty-eight domestic swine (26 +/- 1 kg) were studied with both invasive and noninvasive measurements of ventricular function before and after 10 or 15 min of untreated cardiac arrest. Contrast left ventriculograms, ventricular pressures, cardiac output, isovolumetric relaxation time (tau) and transthoracic Doppler-echocardiographic studies were obtained. RESULTS: Twenty-three of 28 animals were successfully resuscitated and postresuscitation data obtained. Left ventricular ejection fraction showed a significant reduction 30 min after resuscitation (p < 0.05). Regional wall motion analysis revealed diffuse, global left ventricular systolic dysfunction. Left ventricular end-diastolic pressure increased significantly in the postresuscitation period (p < 0.05). Isovolumetric relaxation time (tau) was significantly increased over baseline by 2 h after resuscitation (p < 0.05). Similar findings were noted with the Doppler-echocardiographic analysis, including a reduction in fractional shortening (p < 0.05), a reduction in mitral valve deceleration time (p < 0.05) and an increase in left ventricular isovolumetric relaxation time at 5 h after resuscitation (p < 0.05> By 24 h, these invasive and noninvasive variables of systolic and diastolic left ventricular function had begun to improve. At 48 h, all measures of left ventricular function had returned to baseline levels. CONCLUSIONS: Myocardial systolic and diastolic dysfunction is severe after 10 to 15 min of untreated cardiac arrest and successful resuscitation. Full recovery of this postresuscitation myocardial stunning is seen by 48 h in this experimental model of ventricular fibrillation cardiac arrest.

Animals↗
PubMed1996

Active compression-decompression versus standard cardiopulmonary resuscitation in a porcine model: no improvement in outcome.

Active compression-decompression cardiopulmonary resuscitation (CPR) is a new innovative basic life-support technique during which the anterior chest wall is actively decompressed by a suction device. CPR techniques were studied in 36 swine to test the hypothesis that active compression-decompression CPR improves coronary perfusion pressure, myocardial blood flow during CPR, and 24-hour survival. After 30 seconds of untreated ventricular fibrillation, CPR was begun and continued for 12.5 minutes by one of the three following methods: (1) active compression-decompression CPR with a suction device modified to include a precision force transducer; (2) standard CPR performed with a force transducer device; and (3) standard manual CPR performed without a force transducer device. CPR-generated coronary perfusion pressure, myocardial blood flow, and the force of compression were measured at 3 and 10 minutes of resuscitation effort. Initial return of spontaneous circulation, 24-hour survival, and trauma scores were also evaluated. Active compression-decompression CPR produced consistently better results than did standard CPR performed with a force transducer, but not better than standard CPR performed manually without a force transducer. The use of a force-measuring device with standard CPR may compromise hemodynamic response and outcome.

Animals↗
PubMed1996

Ventricular fibrillation in a swine model of acute pediatric asphyxial cardiac arrest.

STUDY OBJECTIVE: To determine cardiac rhythms in a swine model of acute pediatric asphyxial cardiac arrest. DESIGN: Prospective electrocardiographic evaluation of 36 piglets. SETTING: University hospital laboratory. INTERVENTION: Piglets were acutely asphyxiated by endotracheal tube clamping until 10 min after loss of aortic pulsations. Resuscitative efforts were then provided. RESULTS: None of the animals had ventricular fibrillation (VF) when loss of aortic pulsations occurred (11 +/- 2 min after clamping). Fourteen of the 36 piglets exhibited VF during the asphyxial insult. VF converted to asystole in four piglets prior to resuscitation. Immediately prior to resuscitation, VF occurred in 10 piglets, asystole in 19 piglets, and bradyarrhythmias in seven piglets. CONCLUSION: VF occurs frequently in this piglet model of prolonged asphyxial cardiac arrest, consistent with recent observations in pediatric prehospital cardiac arrests. VF occurred late in the asphyxial process.

Animals↗
PubMed1996

A randomized, blinded trial of high-dose epinephrine versus standard-dose epinephrine in a swine model of pediatric asphyxial cardiac arrest.

OBJECTIVE: To determine whether high-dose epinephrine administration during cardiopulmonary resuscitation (CPR) in a swine pediatric asphyxial cardiac arrest model improves outcome (i.e., resuscitation rate, survival rate, and neurologic function) compared with standard-dose epinephrine. DESIGN: A randomized, blinded study. SETTING: A large animal cardiovascular laboratory at a university. SUBJECTS: Thirty domestic piglets (3 to 4 months of age) were randomized to receive standard-dose epinephrine (0.02 mg/kg) or high-dose epinephrine (0.2 mg/kg) during CPR after 10 mins of cardiac standstill with loss of aortic pulsation after endotracheal tube clamping. INTERVENTIONS: Two minutes of CPR were provided, followed by advanced pediatric life support. Successfully resuscitated animals were supported in an intensive care unit (ICU) setting for 2 hrs and then observed for 24 hrs. MEASUREMENTS AND MAIN RESULTS: Electrocardiogram, thoracic aortic blood pressure, and right atrial blood pressure were monitored continuously until the intensive care period ended. Survival rate and neurologic outcome were determined. Return of spontaneous circulation was obtained in 13 of 15 high-dose epinephrine piglets vs. ten of 15 standard-dose epinephrine piglets (p < .20). Four of 13 high-dose piglets died in the ICU period after initial resuscitation vs. 0 of ten standard-dose piglets (p < or = .05). Nine high-dose piglets survived 2 hrs vs. ten standard-dose piglets. Three piglets in each group survived for 24 hrs, but all were severely neurologically impaired. Two minutes after resuscitation, piglets treated with high-dose epinephrine had higher heart rates (210 +/- 24 vs. 189 +/- 40 beats/min, p < .05) and higher aortic diastolic pressures (121 +/- 39 vs. 74 +/- 40 mm Hg, p < .01). Within 10 mins of return of spontaneous circulation, severe tachycardia (> 240 beats/min) was more frequently noted in the high-dose group than in the standard-dose group (p < .05). All four high-dose piglets that died in the ICU period experienced ventricular fibrillation within 10 mins of return of spontaneous circulation. CONCLUSIONS: High-dose epinephrine did not improve 2-hr survival rate, 24-hr survival rate, or neurologic outcome. High-dose epinephrine resulted in severe tachycardia and hypertension immediately after resuscitation and in a higher mortality rate immediately after resuscitation.

Animals↗
PubMed1996

Initial end-tidal CO2 is markedly elevated during cardiopulmonary resuscitation after asphyxial cardiac arrest.

OBJECTIVES: To compare the initial end-tidal CO2 (PetCO2) during cardiopulmonary resuscitation in asphyxial versus ventricular fibrillatory cardiac arrest. DESIGN: A cohort study. SETTING: University research laboratory. SUBJECTS: Forty domestic piglets. INTERVENTIONS: Asphyxial cardiac arrest was produced by clamping the endotracheal tube in 20 piglets and was continued for 10 minutes after loss of aortic pulsations occurred. Ventricular fibrillation (VF) was induced by applying 60 Hz of alternating current via a pacing wire to the myocardium of the other 20 piglets, and continued for a 15-minute downtime. Cardiopulmonary resuscitation (CPR) was then provided to each group for two minutes, followed by standard advanced cardiac life support protocols. MEASUREMENTS AND MAIN RESULTS: All piglets were instrumented for continuous monitoring of PetCO2, electrocardiogram, central venous pressure, and aortic pressure. PetCO2 of the first breath of CPR was 91 +/- 20 mmHg in the asphyxial group versus 34 +/- 14 mmHg in the VF group (P < 0.001). The asphyxial group continued to exhibit significantly greater PetCO2 for the first five breaths of resuscitation, after which there were no differences. The coronary perfusion pressures during the first breaths of CPR did not differ between the two groups. High initial PetCO2 did not correlate with return of spontaneous circulation. CONCLUSIONS: End-tidal CO2 during the first five breaths of CPR is much higher after an asphyxial cardiac arrest than VF. In each case, the initial PetCO2 appears to reflect alveolar CO2 prior to CPR. After one minute of CPR, PetCO2 is useful in monitoring the effectiveness of CPR.

Animals↗