Nicholas J. Kiraly

External and internal biphasic direct current shock doses for pediatric ventricular fibrillation and pulseless ventricular tachycardia

Objective: To determine energy dose and number of biphasic direct current shocks for pediatric ventricular fibrillation (VF) and pulseless ventricular tachycardia (VT). Design: Observation of preshock and postshock rhythms, energy doses, and number of shocks. Setting: Pediatric hospital. Patients: Shockable ventricular dysrhythmias. Interventions: None. Measurements and Main Results: Forty-eight patients with VF or pulseless VT received external shock at 1.7 ± 0.8 (mean ± sd) J/kg. Return of spontaneous circulation (ROSC) occurred in 23 (48%) patients with 2.0 ± 1.0J/kg, but 25 (52%) patients remained in VF after 1.5 ± 0.7J/kg (p = .05). In 24 non-responding patients, additional 1–8 shocks (final dose, 2.8 ± 1.2 J/kg) achieved ROSC in 14 (58%) with 2.6 ± 1.1 J/kg but not in 10 (42%) with 3.2 ± 1.2 J/kg (not significant). Overall, 37 (77%) patients achieved ROSC with 2.2 ± 1.1 J/kg (range, 0.5–5.0 J/kg). Eight patients without ROSC recovered with cardiopulmonary bypass and internal direct current shock. At 13 subsequent episodes of VF or VT among eight patients, five achieved ROSC and survived. In combined first and subsequent resuscitative episodes, doses in the range of 2.5 to <3 J/kg achieved most cases of ROSC. Survival for >1 yr was seen in 28 (78%) of 36 patients with VF and seven (58%) of 11 patients with VT, with 35 (73%) overall. Lack of ROSC was associated with multiple shocks (p = .003). Repeated shocks with adhesive pads had significantly less impedance (p < .001). Pads in an anteroposterior position achieved highest ROSC rate. Internal shock for another 48 patients with VF or VT achieved ROSC in 28 (58%) patients with 0.7 ± 0.4 J/kg but not in 20 patients with 0.4 ± 0.3 J/kg (p = .01). Nineteen of the nonresponders who received additional internal 1–9 shocks at 0.6 ± 0.5 J/kg and one patient given extracorporeal membrane oxygenation all recovered, yielding 100% ROSC, but 1-yr survival tallied 43 (90%) patients. Conclusions: The initial biphasic direct current external shock dose of 2 J/kg for VF or pulseless VT is inadequate. Appropriate doses for initial and subsequent shocks seem to be in the range of 3–5 J/kg. Multiple shocks do not favor ROSC. The dose for internal shock is 0.6–0.7 J/kg.

The Effect of Suction Method, Catheter Size, and Suction Pressure on Lung Volume Changes During Endotracheal Suction in Piglets

We aimed to identify the effect of suction pressure and catheter size on change in lung volume during open and closed endotracheal suction. Anesthetized piglets (n = 12) were intubated with a 4.0-mm endotracheal tube. Lung injury was induced with saline lavage. Three suction methods (open, closed in-line, and closed with a side-port adaptor) were performed in random order using 6, 7, and 8 French gauge (FG) catheters, at vacuum pressures of 80, 140, and 200 mm Hg. Lung volume change was measured with respiratory inductive plethysmography. Overall, open suction resulted in greater lung volume loss during and at 60-s postsuction than either closed method (p < 0.001). When open and closed methods were analyzed separately, volume change was independent of catheter size and suction pressure with open suction. With closed suction, volume loss increased with larger catheter sizes and higher suction pressures (p < 0.001). With an 8-FG catheter and suction pressure of 140 or 200 mm Hg, volume loss was equivalent with open and closed suction. Lung volume changes are influenced by catheter size and suction pressure, as well as suction method. With commonly used suction pressures and catheter sizes, closed suction has no advantage in preventing loss of volume in this animal model.

Negative tracheal pressure during neonatal endotracheal suction.

Endotracheal tube (ETT) suction is the most frequently performed invasive procedure in ventilated newborn infants and is associated with adverse effects related to negative tracheal pressure. We aimed to measure suction catheter gas flow and intratracheal pressure during ETT suction of a test lung and develop a mathematical model to predict tracheal pressure from catheter and ETT dimensions and applied pressure. Tracheal pressure and catheter flow were recorded during suction of ETT sizes 2.5–4.0 mm connected to a test lung with catheters 5–8 French Gauge and applied pressures of 80–200 mm Hg. The fraction of applied pressure transmitted to the trachea was calculated for each combination, and data fitted to three nonlinear models for analysis. Tracheal pressure was directly proportional to applied pressure (r2 = 0.82–0.99), and catheter flow fitted a turbulent flow model (R2 = 0.85–0.96). With each ETT, increasing catheter size resulted in greater catheter flow (p < 0.0001) and thus lower intratracheal pressure (p < 0.0001). The fraction of applied pressure transmitted to the trachea was accurately modeled using ETT and catheter dimensions (R2 = 0.98–0.99). Negative tracheal pressure during in vitro ETT suction is directly proportional to applied pressure. This relationship is determined by ETT and catheter dimensions.

The Effects of Closed Endotracheal Suction on Ventilation During Conventional and High-Frequency Oscillatory Ventilation

In newborn infants, closed endotracheal tube (ETT) suction may reduce associated adverse effects, but it is not clear whether ventilation is maintained during the procedure. We aimed to determine the effect of ETT size, catheter size, and suction pressure on ventilation parameters measured distal to the ETT. Suction was performed on a test lung, ventilated with conventional (CMV) and high-frequency oscillatory ventilation (HFOV) using ETT sizes 2.5–4.0 mm, catheter sizes 5–8 French gauge (Fr), and suction pressures 80–200 mm Hg. Tracheal and circuit peak inspiratory pressure, positive end-expiratory pressure, and tracheal tidal volume (VT) were recorded for each suction episode. During both CMV and HFOV, tracheal pressures and VT were considerably reduced by suctioning; this reduction was dependent on the combination of ETT, catheter, and suction pressure. Loss of VT, inflation pressure (CMV), and pressure amplitude (HFOV) occurred primarily with insertion of the catheter, and loss of end-expiratory pressure (CMV) and mean tracheal pressure (HFOV) occurred with the application of suction. Circuit pressures were reduced to lesser degree. We conclude that airway pressures and VT are not maintained during closed endotracheal suction with either CMV or HFOV, and choice of equipment and settings will affect the degree of interruption to ventilation.

Timing of routine infant vaccinations and risk of food allergy and eczema at one year of age.

Epidemiological evidence suggests that routine vaccinations can have nontargeted effects on susceptibility to infections and allergic disease. Such effects may depend on age at vaccination, and a delay in pertussis vaccination has been linked to reduced risk of allergic disease. We aimed to test the hypothesis that delay in vaccines containing diphtheria–tetanus–acellular pertussis (DTaP) is associated with reduced risk of food allergy and other allergic diseases.

Volume Not Guaranteed: Closed Endotracheal Suction Compromises Ventilation in Volume-Targeted Mode

Background: Closed endotracheal suction interferes with mechanical ventilation received by infants, but the change to ventilation may be different when ventilator modes that target expired tidal volume (VTe) are used. Objective: To measure airway pressure and tidal volume distal to the endotracheal tube (ETT) during and after closed suction in a volume-targeted ventilation mode with the Dräger Babylog 8000+, and to determine the time until VTe returns to the baseline level. Methods: In this benchtop study, closed suction was performed on 2.5- to 4.0-mm ETTs connected to a test lung. 5–8 French suction catheters were used at suction pressures of 80–200 mm Hg during tidal-volume-targeted ventilation. Results: During catheter insertion and suction, circuit inflating pressure increased and tidal volume was maintained, except when a large catheter relative to the ETT was used, in which case tidal volume decreased. End-expiratory pressure distal to the ETT was reduced during suction by up to 75 cm H2O while circuit end-expiratory pressure was unchanged. Reduction in end-expiratory pressure distal to the ETT was greatest with large catheters and high suction pressures. Following suction, circuit and tracheal inflating pressures increased and tidal volume increased before returning to baseline in 8–12 s. Conclusions: Closed endotracheal suction interferes with ventilator function in volume-targeted mode, with substantially negative intratracheal pressure during suction, and the potential for high airway pressures and tidal volumes following the procedure. These effects should be considered and pressure limits set appropriately whenever using volume-targeted ventilation.

Reduced Risk of Pertussis Among Persons Ever Vaccinated With Whole-Cell Pertussis Vaccine Compared to Recipients of Acellular Pertussis Vaccines May Have Been Confounded by Age

TO THE EDITOR—The phasing out of wholecell pertussis (wP)–containing vaccines in an integrated healthcare system with complete electronic records and a centralized laboratory has provided Witt et al with a unique opportunity to compare its effectiveness against pertussis infection to the newly introduced acellular pertussis (aP)–containing vaccines [1]. This retrospective study compared a large cohort of subjects vaccinated with at least 1 dose of wP with subjects vaccinated only with aP, and found considerable protection from clinical pertussis associated with wP. However this association may have been confounded by age, and therefore further analysis of the data is required before conclusions can be drawn. Subjects were enrolled if they were between 8 and 20 years of age in May 2010, and thus were born between 1990 and 2001. They must have had received at least 5 doses of pertussis-containing vaccines to be included. They were tested for Bordetella pertussis with polymerase chain reaction on nasopharyngeal aspirates between January 2006 and November 2011 if they presented to the healthcare network with symptoms of pertussis infection. Table 3 of Witt et al’s article [1] shows that most of the pertussis cases were in younger children, but it was mostly older children who were wP vaccinated. As the older children were only eligible for testing at an older age (those aged >15 years were tested at age 12–20 years), and the youngest children were only eligible for testing at a young age (children younger than 12 years were tested at age 4–12 years), the comparison of pertussis cases in wPvs aPvaccinated subjects is really a comparison of pertussis in adolescents vaccinated with wP vs young children vaccinated with aP. Given that pertussis is much more common in younger children, the apparent association seems to have been confounded by age, but the authors have not accounted for this possibility. It will be important to investigate whether this association holds after adjusting for age at enrollment. The immunologic consequences of aP vs wP may be considerable, not just for pertussis infections but also for other immune-mediated diseases that may be affected by the altered cytokine and cellular immunity profile associated with wP priming vs aP-only vaccine schedules [2]. A randomized trial may be justified to help inform policy.

BCG for the prevention of food allergy - exploring a new use for an old vaccine.

The prevalence of allergic disease in developed countries has risen dramatically since the mid 20th century and Australia now has the highest documented prevalence of childhood food allergy in the world.1 Theories to explain this rise include changes in the timing of food introduction, epigenetic changes related to environmental factors, and alterations in micronutrient status (particularly of vitamin D). Interactions between the human microbiome, microbial exposures during infancy and the developing immune system are particularly important. According to this model, termed the “hygiene hypothesis” or, more recently, “biome depletion”,2 immune system development may be influenced not only by infections, but also by exposures to animals and antibiotics, and through birth by Caesarean section.

Biphasic DC shock cardioverting doses for paediatric atrial dysrhythmias

OBJECTIVE To determine cardioversion doses of biphasic DC shock for paediatric atrial dysrhythmias. DESIGN Prospective recording of energy, pre-shock and post-shock rhythms. SETTING Paediatric hospital. PATIENTS Shockable atrial dysrhythmias. MAIN RESULTS Forty episodes of atrial dysrhythmias among 25 children (mean age 6.8+/-7.1 years, mean weight 28.2+/-28.5 kg) were treated with external shock. The first shock converted the dysrhythmia to sinus rhythm in 25 episodes. Cardioversion occurred in 2 of 8 (25%) episodes with a dose of <0.5 J/kg, 14 of 16 (88%) with a dose of 0.5-1.0 J/kg and 9 of 16 (56%) with a dose of >1.0 J/kg (p=0.01, Fishers exact test). Ten of 15 initially non-responsive episodes were cardioverted with additional shocks at 1.1+/-0.6 J/kg (range 0.5-2.1 J/kg). Of the remaining 5 unresponsive episodes, 2 of ventricular fibrillation (induced by unsynchronized shock) were successfully defibrillated, and 3 were managed with cardiopulmonary bypass. Among 11 additional children (mean age 4.3+/-6.8 years, mean weight 18.1+/-22.0 kg), 18 episodes of atrial dysrhythmias were treated with internal shock which successfully cardioverted all episodes with one or more shocks at 0.4+/-0.2 J/kg. CONCLUSIONS In rounded doses, recommended initial external cardioversion doses are 0.5-1.0 J/kg and subsequently up to 2 J/kg, internal cardioversion doses are 0.5 J/kg.