An experimental algorithm versus standard advanced cardiac life support in a swine model of out-of-hospital cardiac arrest.

STUDY OBJECTIVE: To compare an experimental algorithm with standard advanced cardiac life support in a swine model of out-of-hospital cardiac arrest. DESIGN: Randomized, controlled experimental trial. SETTING/TYPE OF PARTICIPANT: Animal laboratory using swine. INTERVENTIONS: Eighteen swine (17.8 to 23.7 kg) were sedated, intubated, anesthetized, and instrumented for monitoring of arterial and central venous pressures and ECG. Ventricular fibrillation was induced using a bipolar pacing catheter. Animals were randomized to treatment with the experimental algorithm or standard advanced cardiac life support therapy after eight minutes of untreated ventricular fibrillation. The experimental algorithm consisted of starting CPR; giving high-dose epinephrine (0.20 mg/kg), lidocaine (1.0 mg/kg), bretylium (5.0 mg/kg), and propranolol (0.5 to 1.0 mg) by peripheral IV; hyperventilating (20 to 25 breaths per minute); and delaying countershock (5 J/kg) 60 seconds after completion of drug delivery. Data were analyzed with the Student's t-test and Fisher's exact test. MEASUREMENTS AND MAIN RESULTS: Outcome variables were arterial and central venous pressures, return of spontaneous circulation, and one-hour survival. Hemodynamics were not different between groups during CPR. Return of spontaneous circulation occurred in seven of nine swine (77%) in the experimental algorithm group versus two of nine swine (22%) in the advanced cardiac life support group (P = .057). Four of nine swine (44%) in the experimental algorithm group survived to one hour versus none of the animals in the advanced cardiac life support group (P = .041). CONCLUSION: In this swine model of out-of-hospital cardiac arrest, animals treated with an experimental algorithm had a significant improvement in one-hour survival compared with those treated with advanced cardiac life support.

Translaryngeal jet ventilation and end-tidal PCO2 monitoring during varying degrees of upper airway obstruction.

STUDY OBJECTIVES: To explore the ventilatory adequacy of translaryngeal jet ventilation (TLJV) during partial upper airway obstruction and the usefulness of monitoring end-tidal CO2 (PETCO2) during this condition. DESIGN: Prospective, nonrandomized, sequential crossover design. SETTING AND PARTICIPANTS: Apneic dog model (five dogs; mean weight, 23 kg). INTERVENTIONS: Animals were intubated with a 9.0-mm endotracheal tube with the tip positioned above the cricothyroid membrane. Upper airway obstructions of 40%, 69%, and 80% were created. TLJV was performed through the cricothyroid membrane using a 13-gauge catheter with 100% oxygen, 45 psi, 15 breaths per minute, and 30% inspiratory time for 15 minutes at each upper airway obstruction. Data collected at baseline (no upper airway obstruction) and one-minute intervals included arterial blood pressures, continuous PaCO2 measurements, and PETCO2 at the TLJV catheter tip and above the level of obstruction. Arterial blood gases were obtained at 0 and 15 minutes. Data were analyzed using Pearson's correlation, analysis of variance, and Turkey's multiple comparisons (significance, P less than .05). MEASUREMENTS AND RESULTS: Baseline values for all variables did not significantly differ at the onset of each testing phase. Mean pH increased significantly from baseline during 69% upper airway obstruction (7.36 to 7.54, P less than .05) and 80% upper airway obstruction (7.39 to 7.61, P less than .01). Mean PaCO2 decreased significantly from baseline during all upper airway obstructions: 40% upper airway obstruction (39.9 to 33.6 mm Hg, P less than .01), 69% upper airway obstruction (38.3 to 25.6 mm Hg, P less than .001), and 80% upper airway obstruction (36.2 to 18.2 mm Hg, P less than .001). PaCO2, PETCO2, and pH differed significantly between each level of upper airway obstruction (P less than .01). PETCO2 was significantly correlated with PaCO2 (r = .84, P less than .001) and did not significantly differ from PaCO2. No signs of barotrauma were observed in any animal at any degree of upper airway obstruction. CONCLUSION: TLJV during partial upper airway obstruction in our model provided safe and adequate-to-supranormal minute ventilation. In fact, marked hypocapnia and alkalemia occurred at levels of 69% and 80% upper airway obstruction, thus dispelling concepts that TLJV may cause hypercapnia during partial upper airway obstruction. PETCO2 correlates well with PaCO2 and may be valuable for monitoring ventilation when using TLJV in the nonobstructed or partially obstructed upper airway.