Ikram U. Haque

Analysis of the evidence for the lower limit of systolic and mean arterial pressure in children.

Objective: Systolic blood pressure (SBP) and mean arterial pressure (MAP) are essential evaluation elements in ill children, but there is wide variation among different sources defining systolic hypotension in children, and there are no normal reference values for MAP. Our goal was to calculate the 5th percentile SBP and MAP values in children from recently updated data published by the task force working group of the National High Blood Pressure Education Program and compare these values with the lowest limit of acceptable SBP and MAP defined by different sources. Design: Mathematical analysis of clinical database. Methods: The 50th and 95th percentile SBP values from task force data were used to derive the 5th percentile value for children from 1 to 17 yrs of age stratified by height percentiles. MAP values were calculated using a standard mathematical formula. Calculated SBP values were compared with systolic hypotension definitions from other sources. Linear regression analysis was applied to create simple formulas to estimate 5th percentile SBP and 5th and 50th percentile MAP for different age groups at the 50th height percentile. Results: A 9–21% range in both SBP and MAP values was noted for different height percentiles in the same age groups. The 5th percentile SBP values used to define hypotension by different sources are higher than our calculated values in children but are lower than our calculated values in adolescents. Clinical formulas for calculation of SBP and MAP (mm Hg) in normal children are as follows: SBP (5th percentile at 50th height percentile) = 2 × age in years + 65, MAP (5th percentile at 50th height percentile) = 1.5 × age in years + 40, and MAP (50th percentile at 50th height percentile) = 1.5 × age in years + 55. Conclusion: We developed new estimates for values of 5th percentile SBP and created a table of normal MAP values for reference. SBP is significantly affected by height, which has not been considered previously. Although the estimated lower limits of SBP are lower than currently used to define hypotension, these values are derived from normal healthy children and are likely not appropriate for critically ill children. Our data suggest that the current values for hypotension are not evidence-based and may need to be adjusted for patient height and, most important, for clinical condition. Specifically, we suggest that the definition of hypotension derived from normal children should not be used to define the SBP goal; a higher target SBP is likely appropriate in many critically ill and injured children. Further studies are needed to evaluate the appropriate threshold values of SBP for determining hypotension.

Effect of alternative chest compression techniques in infant and child on rescuer performance

Objective: Current chest compression (CC) guidelines for an infant recommend a two-finger (TF) technique with lone rescuer and a two- thumb (TT) technique with two rescuers, and for a child either an one hand (OH) or a two hand (TH) technique with one or two rescuers. The effect of a 30:2 compression:ventilation ratio using these techniques on CC quality and rescuer fatigue is unknown. We hypothesized that during lone rescuer CC, TT technique, in infant and TH in child achieve better compression depth (CD) without additional rescuer fatigue compared with TF and OH, respectively. Design: Randomized observational study. Setting: University-affiliated pediatric hospital. Subjects: Adult healthcare providers certified in basic life support or pediatric advanced life support. Interventions: Laerdal baby advanced life support trainer and Resusci junior manikin were modified to digitally record CD, compression pressure (CP) and compression rate. Sixteen subjects were randomized to each of the four techniques to perform 5 minutes of lone rescuer 30:2 compression:ventilation cardiopulmonary resuscitation. Rescuer heart rate (HR) and respiratory rate were recorded continuously and the recovery time interval for HR/respiratory rate to return to baseline was determined. Subjects were blinded to data recording. Groups were compared using two-sample, two-sided Student’s t tests. Measurements and Main Results: Two-thumb technique generated significantly higher CD and peak CP compared with TF (p < 0.001); there was no significant difference between OH vs. TH. TF showed decay of CD and CP over time compared with TT. Compression rate (per minute) and actual compressions delivered were not significantly different between groups. No significant differences in fatigue and recovery time were observed, except the TT group had greater increase in the rescuer’s HR (bpm) from baseline compared with TF group (p = 0.04). Conclusions: Two-thumb compression provides higher CD and CP compared with TF without any evidence of decay in quality and additional rescuer fatigue over 5 minutes. There was no significant difference in child CC quality or rescuer fatigue between OH and TH. Two-thumb technique is preferred for infant CC and our data support the current guidelines for child CC.

Chest compression quality and rescuer fatigue with increased compression to ventilation ratio during single rescuer pediatric CPR

OBJECTIVE The effects of the recommended 30:2 compression:ventilation (C:V) ratio on chest compression rate (CR), compression depth (CD), compression pressure (CP) and rescuer fatigue is unknown during pediatric CPR. We hypothesized that a 30:2 C:V ratio will decrease compression depth and compression pressure and increase rescuer fatigue compared with a 15:2 ratio. DESIGN Randomized crossover observational study. METHODS Adolescent, child and infant manikins were modified to digitally record compression rate, compression depth, compression pressure and total compression cycles (CC). BLS or PALS certified volunteers were randomized to five CPR groups: adolescent (AD), child 1-hand (OH), child 2-hand (TH), infant two-finger (TF) and infant two-thumb (TT). Each rescuer performed each ratio for 5 min with the order randomized. Rescuer heart rate (HR) and respiratory rate (RR) were recorded continuously during CPR and used to determine the recovery time (RT) for HR/RR to return to baseline. Data (mean+/-S.D.) were contrasted by paired differences for quantitative data and the sign rank test for ordinal data. RESULTS Eighty subjects (16 per group) were randomized. The peak compression pressure and compression rate were not different within any group, but total compression cycle were higher in all 30:2 groups. Compression depth (mm) was not significantly different within any group. The rescuers HR (bpm) increased significantly during 30:2 CPR in AD and OH group with no significant differences in RR and recovery time. Subjects reported that 15:2 CPR was easier to perform (P<0.001). CONCLUSION During single rescuer pediatric BLS, more compression cycles were achieved with 30:2 C:V ratio without effect on compression depth, pressure and rate. Increased HR with 30:2 C:V ratio was noted during larger manikin CPR without subjective difference of reported fatigue. Most rescuers in AD and TF group did not achieve recommended compression depth regardless of C:V ratio.

Pediatric critical care community survey of knowledge and attitudes toward therapeutic hypothermia in comatose children after cardiac arrest

Objective: Therapeutic hypothermia improves neurologic outcome and survival after adult out-of-hospital cardiac arrest. To help us design a prospective hypothermia trial in children, we developed a survey to assess current knowledge and attitude of pediatric critical care providers regarding therapeutic hypothermia and potential impediments to implementing a prospective study. Design: Anonymous survey. Setting: Internet-based survey of pediatric critical care community. Interventions: None. Results: A total of 159 responders completed the survey. Most respondents (92%) were fellowship-trained in pediatric critical care, with 9.9 ± 6.5 yrs of experience. Many (85%) worked in the United States; 89% were in large tertiary care centers with residency or fellowship training programs. Most (65%) were aware of the adult randomized trials of therapeutic hypothermia, but only 9% (always) or 38% (sometimes) utilize this therapy. The most common reason to use hypothermia was likelihood of patient recovery, absence of life-limiting disease, and presence of coma for ≥1 hr after resuscitation. The majority of responders using therapeutic hypothermia cool their patients to 33–35°C for a duration ranging from as short as 12 hrs to as long as 96 hrs; 91% do not actively rewarm the patient. A majority (81%) agree that a randomized, controlled trial of therapeutic hypothermia in children is ethical, and 95% would be willing to randomize their patients. Finally, 81% thought that therapeutic hypothermia should be studied in other ischemic insults and not just cardiac arrest. Conclusions: Despite widespread awareness of therapeutic hypothermia’s beneficial effects after arrest, it is not widely used by pediatric critical care clinicians sampled in our survey. Among those using hypothermia, there is wide variation in methodology and end points of therapy. This seems to result from a lack of evidence, difficulty with the technique, and unavailability of explicit protocols. Pediatric studies are needed to assess the safety, feasibility, and effectiveness of therapeutic hypothermia after cardiac arrest and other causes of brain injury.

Two-thumb technique is superior to two-finger technique during lone rescuer infant manikin CPR

OBJECTIVE Infant CPR guidelines recommend two-finger chest compression with a lone rescuer and two-thumb with two rescuers. Two-thumb provides better chest compression but is perceived to be associated with increased ventilation hands-off time. We hypothesized that lone rescuer two-thumb CPR is associated with increased ventilation cycle time, decreased ventilation quality and fewer chest compressions compared to two-finger CPR in an infant manikin model. DESIGN Crossover observational study randomizing 34 healthcare providers to perform 2 min CPR at a compression rate of 100 min(-1) using a 30:2 compression:ventilation ratio comparing two-thumb vs. two-finger techniques. METHODS A Laerdal Baby ALS Trainer manikin was modified to digitally record compression rate, compression depth and compression pressure and ventilation cycle time (two mouth-to-mouth breaths). Manikin chest rise with breaths was video recorded and later reviewed by two blinded CPR instructors for percent effective breaths. Data (mean+/-SD) were analyzed using a two-tailed paired t-test. Significance was defined qualitatively as p< or =0.05. RESULT Mean % effective breaths were 90+/-18.6% in two-thumb and 88.9+/-21.1% in two-finger, p=0.65. Mean time (s) to deliver two mouth-to-mouth breaths was 7.6+/-1.6 in two-thumb and 7.0+/-1.5 in two-finger, p<0.0001. Mean delivered compressions per minute were 87+/-11 in two-thumb and 92+/-12 in two-finger, p=0.0005. Two-thumb resulted in significantly higher compression depth and compression pressure compared to the two-finger technique. CONCLUSION Healthcare providers required 0.6s longer time to deliver two breaths during two-thumb lone rescuer infant CPR, but there was no significant difference in percent effective breaths delivered between the two techniques. Two-thumb CPR had 4 fewer delivered compressions per minute, which may be offset by far more effective compression depth and compression pressure compared to two-finger technique.

Intravascular infusion of acid promotes intrapulmonary inducible nitric oxide synthase activity and impairs blood oxygenation in rats.

ObjectiveTo test the hypothesis that intravascular acid infusion promotes intrapulmonary nitric oxide formation by promoting inducible nitric oxide synthase (iNOS) and inhibiting endothelial nitric oxide synthase (eNOS) expression in rats. DesignProspective, placebo controlled, randomized laboratory study. SettingUniversity laboratory. SubjectsTwelve male Sprague-Dawley rats weighing 317 ± 30 g served as study subjects. All animals were anesthetized, paralyzed, and mechanically ventilated throughout the experiment. InterventionsThe animals were randomized to receive either 0.1 N hydrochloric acid or 0.9% saline intravenously. The infusions were initially given at a rate of 11 mL/kg/hr for 15 mins and then at a rate of 0.95 mL/kg/hr for the remainder of the experiment. Exhaled nitric oxide concentrations and hemodynamic measurements were monitored throughout the experiment. Lung tissues were harvested for Western blot analysis and immunostaining 4 hrs after starting the intravascular infusion. Measurement and Main ResultsAt the end of the experiment, we found more than a four-fold higher concentration of exhaled nitric oxide in the acid-treated animals than in the saline-treated animals (p < .001). Western blot analysis revealed that the acid infusion increased intrapulmonary iNOS concentrations (p < .001), yet it decreased intrapulmonary eNOS concentrations (p = .009). Acid-related lung injury manifested as a decrease in blood oxygen tensions (p = .045) and as an increase in lung homogenate interleukin-6 concentrations (p = .003). ConclusionsOur results reveal that hydrochloric acid infusion stimulates intrapulmonary nitric oxide formation at least in part by promoting the expression of iNOS. Our findings suggest that correcting acidosis should attenuate iNOS formation. Our data also support the idea that metabolic acidosis itself can lead to impaired intrapulmonary gas exchange and increased expression of pro-inflammatory cytokines such as interleukin-6. Whether the induction of intrapulmonary nitric oxide formation mediates or simply indicates lung injury warrants further investigation.

Outcome Following Cardiopulmonary Arrest

This article summarizes the current state of outcomes and outcome predictors following pediatric cardiopulmonary arrest with special emphasis on neurologic outcome. The authors briefly describe the factors associated with outcome and review clinical signs, electrophysiology, neuroimaging, and biomarkers used to predict outcome after cardiopulmonary arrest. Although clinical signs, imaging, and somatosensory evoked potentials are best associated with outcome, there are limited data to guide clinicians. Combinations of these predictors will most likely improve outcome prediction, but large-scale outcome studies are needed to better define these predictors.

Endogenous osteopontin promotes ozone-induced neutrophil recruitment to the lungs and airway hyperresponsiveness to methacholine

Inhalation of ozone (O₃), a common environmental pollutant, causes pulmonary injury, pulmonary inflammation, and airway hyperresponsiveness (AHR) in healthy individuals and exacerbates many of these same sequelae in individuals with preexisting lung disease. However, the mechanisms underlying these phenomena are poorly understood. Consequently, we sought to determine the contribution of osteopontin (OPN), a hormone and a pleiotropic cytokine, to the development of O₃-induced pulmonary injury, pulmonary inflammation, and AHR. To that end, we examined indices of these aforementioned sequelae in mice genetically deficient in OPN and in wild-type, C57BL/6 mice 24 h following the cessation of an acute (3 h) exposure to filtered room air (air) or O₃ (2 parts/million). In wild-type mice, O₃ exposure increased bronchoalveolar lavage fluid (BALF) OPN, whereas immunohistochemical analysis demonstrated that there were no differences in the number of OPN-positive alveolar macrophages between air- and O₃-exposed wild-type mice. O₃ exposure also increased BALF epithelial cells, protein, and neutrophils in wild-type and OPN-deficient mice compared with genotype-matched, air-exposed controls. However, following O₃ exposure, BALF neutrophils were significantly reduced in OPN-deficient compared with wild-type mice. When airway responsiveness to inhaled acetyl-β-methylcholine chloride (methacholine) was assessed using the forced oscillation technique, O₃ exposure caused hyperresponsiveness to methacholine in the airways and lung parenchyma of wild-type mice, but not OPN-deficient mice. These results demonstrate that OPN is increased in the air spaces following acute exposure to O₃ and functionally contributes to the development of O₃-induced pulmonary inflammation and airway and lung parenchymal hyperresponsiveness to methacholine.

Effect of antigen sensitization and challenge on oscillatory mechanics of the lung and pulmonary inflammation in obese carboxypeptidase E-deficient mice.

Atopic, obese asthmatics exhibit airway obstruction with variable degrees of eosinophilic airway inflammation. We previously reported that mice obese as a result of a genetic deficiency in either leptin (ob/ob mice) or the long isoform of the leptin receptor (db/db mice) exhibit enhanced airway obstruction in the presence of decreased numbers of bronchoalveolar lavage fluid (BALF) eosinophils compared with lean, wild-type mice following antigen (ovalbumin; OVA) sensitization and challenge. To determine whether the genetic modality of obesity induction influences the development of OVA-induced airway obstruction and OVA-induced pulmonary inflammation, we examined indices of these sequelae in mice obese as a result of a genetic deficiency in carboxypeptidase E, an enzyme that processes prohormones and proneuropeptides involved in satiety and energy expenditure (Cpe(fat) mice). Accordingly, Cpe(fat) and lean, wild-type (C57BL/6) mice were sensitized to OVA and then challenged with either aerosolized PBS or OVA. Compared with genotype-matched, OVA-sensitized and PBS-challenged mice, OVA sensitization and challenge elicited airway obstruction and increased BALF eosinophils, macrophages, neutrophils, IL-4, IL-13, IL-18, and chemerin. However, OVA challenge enhanced airway obstruction and pulmonary inflammation in Cpe(fat) compared with wild-type mice. These results demonstrate that OVA sensitization and challenge enhance airway obstruction in obese mice regardless of the genetic basis of obesity, whereas the degree of OVA-induced pulmonary inflammation is dependent on the genetic modality of obesity induction. These results have important implications for animal models of asthma, as modeling the pulmonary phenotypes for subpopulations of atopic, obese asthmatics critically depends on selecting the appropriate mouse model.

Novel adhesive glove device (AGD) for active compression–decompression (ACD) CPR results in improved carotid blood flow and coronary perfusion pressure in piglet model of cardiac arrest

OBJECTIVE ACD-CPR improves coronary and cerebral perfusion. We developed an adhesive glove device (AGD) and hypothesized that ACD-CPR using an AGD provides better chest decompression resulting in improved carotid blood flow as compared to standard (S)-CPR. DESIGN Prospective, randomized and controlled animal study. METHODS Sixteen anesthetized and ventilated piglets were randomized after 3 min of untreated VF to receive either S-CPR or AGD-ACD-CPR by a PALS certified single rescuer with compressions of 100 min(-1) and C:V ratio of 30:2. AGD consisted of a modified leather glove exposing the fingers and thumb. A wide Velcro patch was sewn to the palmer aspect of the glove and the counter Velcro patch was adhered to the pigs chest wall. Carotid blood flow was measured using ultrasound. Data (mean±SD) was analyzed using one way ANOVA and unpaired t-test; p-value ≤ 0.05 was considered statistically significant. RESULTS Right atrial pressure (mmHg) during the decompression phase was lower during AGD-ACD-CPR (-3.32±2.0) when compared to S-CPR (0.86±1.8, p=0.0007). Mean carotid blood flow was 53.2±27.1 (% of baseline blood flow in ml/min) in AGD vs. 19.1±12.5% in S-CPR, p=0.006. Coronary perfusion pressure (CPP, mmHg) was 29.9±5.8 in AGD vs. 22.7±6.9 in S-CPR, p=0.04. There was no significant difference in time to ROSC and number of epinephrine doses. CONCLUSION Active chest decompression during CPR using this simple and inexpensive adhesive glove device resulted in significantly better carotid blood flow during the first 2 min of CPR.