Impact of simulated light scatter on scanning laser Doppler flowmetry.

AIM: To determine the impact of simulated light scatter on scanning laser Doppler flowmetry (SLDF) assessment of retinal capillary blood flow and retinal image quality. METHODS: One eye of 10 normal subjects (mean (SD) age 24 (1.7) years, range 22-27) was randomly selected. Varying concentrations of polystyrene microspheres were suspended in optically clear cells to simulate light scatter. The microsphere concentrations used were 0.05%, 0.03%, 0.02%, 0.01%, and a cell containing only water. LogMAR visual acuity and contrast sensitivity were measured both with and without cells. Optimal focus and alignment was established by acquiring three SLDF images each of the optic nerve head (ONH) and of the macula using the Heidelberg retina flowmeter (HRF) with no cell in place. SLDF images were subsequently acquired with each of the light scatter cells mounted in front of the HRF. The group mean retinal capillary blood flow was compared using repeated measures analysis of variance (reANOVA) as a function of microsphere concentration. RESULTS: Retinal capillary blood flow increased significantly in the ONH, nasal macula, fovea, and temporal macula with increasing microsphere concentration (p<0.0001). Using Dunnett's post hoc test, retinal capillary blood flow was found to be significantly increased relative to the no cell condition for the 0.03% and 0.05% cell concentrations. CONCLUSIONS: Simulated light scatter produces an artifactual increase in retinal capillary blood flow. The impact of cataract on SLDF measurements has yet to be determined.

Measurement of pediatric illness severity using simple pretransport variables.

OBJECTIVE: To test the hypothesis that pretransport variables can predict in-hospital mortality that will correlate with major interventions and unplanned events during interfacility transport. METHODS: A cohort of children (n = 2,253) transported by a specialized pediatric team to a children's hospital were studied. At the time of referral, data collected included age (months), heart rate, systolic blood pressure, respiratory rate, retractions, stridor or wheezing, seizures, skin perfusion, oxygen requirement, and mental status. Using univariate and stepwise logistic regression, variables predictive of in-hospital mortality were selected from a training set (n = 1,111) and assigned integers based on their computed coefficients. Probability of in-hospital mortality was calculated using the total integer score and age. The risk of mortality derived from the training set was validated in the remaining patients (n = 1,142) by comparing the observed and predicted mortalities. Major interventions performed and unplanned events were determined for each of five predetermined mortality risk groups. RESULTS: Variables (integers) predicting in-hospital mortality included systolic blood pressure (11), respiratory rate (6), oxygen requirement (11), and altered mental status (11). Observed mortality was similar to predicted mortality in all risk categories for the validation sample. As risk of mortality increased, so did the performance of major interventions and the occurrence of unplanned events. CONCLUSION: Four pretransport variables predicted in-hospital mortality. Risk of mortality correlated with the incidence of major patient interventions, and the occurrence of unplanned events increased as well. This model might be useful in comparing different transport systems using severity-adjusted assessment of children requiring interfacility transport.

NPB-75: A portable quantitative microstream capnometer.

A portable quantitative microstream capnometer (NPB-75) was tested in intubated children. The end-tidal CO(2) values measured by this device showed good agreement with concomitantly measured values of a stationary mainstream capnometer (N-6000). This lightweight device, with a 4-hour battery life, graphic capnogram display, and audiovisual alarms is well suited for the prehospital setting.

Validation of predictors of extubation success and failure in mechanically ventilated infants and children.

OBJECTIVE: To validate predictors of extubation success and failure in mechanically ventilated infants and children by using bedside measures of respiratory function. DESIGN: Prospective, descriptive study. SETTING: A university-affiliated children's hospital with a 51-bed critical care area. PATIENTS: All infants and children who were mechanically ventilated for > or =24 hrs except neonates < or =37 wks gestation and patients with neuromuscular disease. INTERVENTIONS: None. MEASUREMENTS AND METHODS: Extubation failure was defined as reintubation within 48 hrs of extubation in the absence of upper airway obstruction. Failure rates were calculated for different ranges (selected a priori of preextubation measures of breathing effort, ventilator support, respiratory mechanics, central inspiratory drive, and integrated indices useful in adults. Effort of spontaneous breathing was assessed by the respiratory rate standardized to age, the presence of retractions and paradoxic breathing, inspiratory pressure, maximal negative inspiratory pressure, ratio of inspiratory pressure to maximal negative inspiratory pressure, and tidal volume indexed to body weight of a spontaneous breath. Ventilator support was measured by F(IO2), mean airway pressure, oxygenation index, and the fraction of total minute ventilation provided by the ventilator. Respiratory mechanics was assessed by peak ventilatory inspiratory pressure and dynamic compliance. Central inspiratory drive was assessed by mean inspiratory flow. Frequency to tidal volume ratio and the CROP (compliance, rate, oxygenation, and pressure) indexed to body weight, the integrated indices useful in predicting extubation failure in adults, were also calculated. A regression test for a linear trend in proportions was performed with preselected ranges and the corresponding failure rates. The failure rates from this study (validation group) were compared to those published previously (prediction group) by the chi-square test for proportions. The distribution of categorical variables between groups was analyzed by using the chi-square test or the Fisher's exact test, and p < .05 was considered significant. MAIN RESULTS: The study involved 312 patients. There were no differences in any of the clinical characteristics between the prediction and validation groups. The reasons for reintubation were similar in both groups. Preextubation data were also similar between the two groups. There were no differences between the prediction and the validation groups in failure rates with different ranges. There were no differences in the failure rates for any of the cutoff values for peak ventilatory inspiratory pressure, mean airway pressure, F(IO2), oxygenation index, dynamic compliance, tidal volume indexed to body weight of a spontaneous breath, fraction of total minute ventilation provided by the ventilator, and mean inspiratory flow. CONCLUSIONS: Bedside measures of respiratory function can predict extubation success and failure in infants and children. Both a low risk and a high risk of failure can be determined by using these measures. Integrated indices useful in adults do not reliably predict extubation success or failure in infants and children. Our study validates our previously published study.

Air leaks from the respiratory tract in mechanically ventilated children with severe respiratory disease.

Our objectives were to evaluate the frequency of air leaks (AL) from the respiratory tract (pneumothorax, pneumomediastinum, pneumoperitoneum, subcutaneous emphysema) in critically ill children on mechanical ventilation (MV) for severe respiratory diseases, and to examine whether AL could be correlated with specific clinical events or ventilator settings. The study constitutes a retrospective cohort of 80 consecutive critically ill children receiving MV for severe respiratory diseases between 1986 and 1993. Patients (mean age 2.9 +/- 0.6 years, 49 males and 31 females), were admitted to the Pediatric Intensive Care Unit (PICU) with acute respiratory syndrome (ARDS) (27%), asthma (15%), bronchiolitis (10%), pneumonia (21%), pulmonary congenital diseases (9%), or foreign body aspiration (18%). Patients were divided into two groups; those with AL (n=22) and those without air-leaks (non-AL) (n = 58). Air leaks developed in 22 of 80 patients or in 27.5%. Survival was significantly lower in the AL group, compared to the non-AL group (41% vs. 76%, P < 0.01). The odds ratio that a patient with multiple organ system failure (MOSF) or infection would develop AL was 2.96 and 2.19, respectively. Candida and Pseudomonas species were recovered with significantly higher frequency in the AL group compared with the non-AL group (P < 0.025). There was a strong positive correlation between the incidence of AL and high ventilatory pressures (PIP 36 vs. 29.7 cm H(2)O, P < 0.001), or large tidal volumes (V(T) 12 vs. 9 mL/kg, P < 0.05), suggesting that large volumes might elicit injury to the pulmonary epithelium. Multiple logistic regression analysis showed that only V(T) was independently associated with the development of AL in children with primary severe respiratory disease (r(2) = -0.38, P = 0.01). In conclusion, MV will produce AL, particularly when high peak airway pressures (barotrauma) or large tidal volumes (volotrauma) are delivered by the ventilator. Sepsis, MOSF, and lung superinfection with Pseudomonas or Candida species may be also important factors in the development of AL in critically ill children.

Flow and volume dependence of respiratory mechanics in anesthetized children.

With the use of constant flow, end-inspiratory airway occlusion, respiratory system resistance (Rrs) can be partitioned into a flow resistive component (Rint) and an additional component (deltaR), reflecting viscoelasticity and time constant inequality. Similarly, respiratory system elastance (Edyn) can be partitioned into static elastance (Est) and elastance due to viscoelasticity and time constant inequality (deltaE). We measured Rrs and Edyn and their subdivisions (Rint and deltaR, Est and deltaE, respectively) and studied their flow and volume dependence in eight otherwise healthy children (median age 3.6 y; range 1.9-5.2 y) undergoing general anesthesia for oral rehabilitation. With a constant inspiratory flow (VI) of approximately 15 mL/s/kg and tidal volume of 12 mL/kg, the mean values of Rrs, Rint, and deltaR were: 0.20, 0.11, and 0.10 cmH2O/mL/s.kg. Under the same conditions, the mean Est and deltaE were: 1.04 and 0.12 cmH2O/mL/kg. With increasing VI and under constant VT, deltaR decreased (p < 0.001) progressively. Rint also decreased paradoxically (p < 0.001). Hence, Rrs decreased (p < 0.001) with increasing VI. Est decreased (p < 0.001) with increasing VI, whereas delta E increased (p < 0.005). With increasing VT and under constant VI, Rint decreased (p < 0.001) and deltaR tended to increase (p = 0.058); Rrs did not change. With increasing VT under constant VI, both Est and deltaE decreased (p < 0.001 and p = 0.001, respectively). Thus, in contrast to the findings in adults, Rint and Est decreased in children with increasing flow and under constant tidal volume, probably reflecting decreased functional residual capacity in anesthetized children, compared with adults. The flow and volume dependence of deltaR and deltaE were similar to those in adults, whereas Rrs did not necessarily follow the direction of changes of deltaR.

PEEP-induced pulmonary vasoconstriction in neonatal piglets: analysis by pressure-flow curves.

We analyzed the effect of two levels of positive end-expiratory pressure (PEEP: 10 and 15 cm H2O) on pulmonary hemodynamics in neonatal piglet lungs isolated in situ and perfused extracorporeally using pulmonary artery pressure-flow (Pa/Q) relationships. Pulmonary artery pressure (Pa) was measured at flow rates of 50, 75, 100, 125, and 150 mL/kg/min. Pa/Q relationship was evaluated by the slope of the Pa/Q plot and the zero-flow intercept pressure (Pi). Pa/Q relationship with PEEP was studied before and after verapamil. Both levels of PEEP increased the slope of the Pa/Q plot and Pi. PEEP of 15 cm H2O resulted in a steeper slope and a higher Pi compared to 10 cm H2O of PEEP (P < 0.05). Verapamil abolished the increase in slope of the pulmonary artery Pa/Q plot but did not affect the increase in Pi with PEEP. The increase in Pi was equal to the increase in mean airway pressure. Verapamil did not affect changes in ventilatory parameters. PEEP increased pulmonary vascular resistance (PVR) both by increasing the Pi, which reflects the weighted average of the critical closing pressure, and represents a "Starling resistor" phenomenon, and an increase in the slope of the P-Q plot, reflecting an increase in pulmonary vascular tone. This response may be unique to the neonatal pulmonary circulation.

Partitioning of respiratory system resistance in children with respiratory insufficiency.

Using end-inspiratory airway occlusion, respiratory system resistance (Rrs) can be partitioned into a flow-resistive component (Rint), and an additional component (DeltaR), reflecting viscoelasticity and time constant inequalities. We studied flow and volume dependence of Rrs and its subdivisions (Rint and DeltaR) in 13 children, seven mechanically ventilated for pulmonary insufficiency (Group 1; six with parenchymal lung disease; one with lower airway obstruction) and six without primary lung disorder (Group 2). In comparison with healthy children, Rint was increased in the patient with lower airway obstruction and five of six patients without primary lung disorder but in only one of six with parenchymal lung disease. DeltaR was increased in all seven patients in Group 1 and in four of six patients in Group 2. The directions of changes in Rint and Rrs with increasing flow (isovolume conditions) and with increasing volume (isoflow conditions) were variable. DeltaR decreased exponentially (p < 0.05) with increasing flow in 11 of 13 subjects and increased with increasing tidal volume (VT) in 12 of 13. Thus, DeltaR was increased in most children on mechanical ventilation with or without primary lung disease; its volume and flow dependence were opposite to that of airway resistance.

Occult nitric oxide inhalation improves oxygenation in mechanically ventilated children.

OBJECTIVES: Auto-inhalation of nitric oxide (NO) produced in the upper airways may have physiologic effects on lung function. For intubated patients, the upper airway source of NO is eliminated, but the hospital compressed air source from the environment is contaminated with varying levels of NO, creating an "occult" form of NO therapy. We examined the physiologic significance of occult inhaled NO in ventilator-dependent pediatric patients. We hypothesized that very low levels of NO contamination in inspired gas improve PaO2 in ventilator-dependent children. STUDY DESIGN: Inspired NO levels at the mouth were measured by chemiluminescence in 4 pediatric subjects with normal lungs and 3 with parenchymal lung disease. Subjects were sequentially ventilated with first standard hospital gas (H1), switched to pure nitrogen-oxygen at a similar FIO2 but with no NO contamination (A2), hospital gas again (H2), the nitrogen-oxygen (A2) to control for time and sequence, and finally the nitrogen-oxygen mixture with supplemental NO in an amount equal to the NO previously measured in hospital gas (A2 + NO). Inhaled NO levels and PaO2 were recorded 15 minutes into each of the 5 steps. Two patients were studied a second time, remote from their first examination. RESULTS: NO levels in inhaled hospital gas mixtures ranged from 13 to 79 ppb (mean H1 = 53.3 +/- 23.7 ppb, mean H2 = 53.2 +/- 20.7 ppb, mean A2 + NO = 45 +/- 15.3 ppb; P < .0001). Removing NO from ventilator gas decreased PaO2 in all subjects, whereas replacing NO in artificial gas restored PaO2 to baseline values (P < .0001). CONCLUSION: Concentrations of NO in hospital compressed air are variable and have physiologic effects. The long-term implications of these findings remain to be defined.

Accuracy of physiologic deadspace measurement in intubated pediatric patients using a metabolic monitor: comparison with the Douglas bag method.

OBJECTIVE: To evaluate the accuracy of physiologic deadspace (VD/VT) measurement, using a metabolic monitor. DESIGN: Prospective collection of data. SETTING: University-affiliated children's hospital with a 51-bed critical care area. PATIENTS: Infants and children who were sedated and paralyzed and were receiving mechanical ventilation through a cuffed endotracheal tube. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Mixed expired carbon dioxide tension (PECO2) was measured. With the Douglas bag method, mixed expired gas was collected over 15 mins and was analyzed. With the metabolic monitor, FECO2 was measured for 15 mins and the results were averaged. The PECO2 was calculated by multiplying FECO2 by the barometric pressure. The PaCO2 was measured simultaneously. The PECO2 was corrected for the compressible volume in the ventilator circuit. All gas volumes were corrected for body temperature, pressure, and water vapor pressure. The physiologic deadspace/tidal volume ratio (VD/VT) was calculated for both techniques using the Enghoff modification of the Bohr equation. The accuracy of the VD/VT measured, by using the metabolic monitor, was assessed by comparing this measurement against the VD/VT measured by the Douglas bag method. This comparison was done by simple linear regression and correlation and by bias analysis (Bland and Altman method). The magnitude of compressible volume expressed as a fraction of the tidal volume delivered by the ventilator was compared with the error in VD/VT expressed as the difference between the uncorrected and corrected VD/VT. Sixteen paired measurements were made in 12 children. The VD/VT measured by the metabolic monitor correlated well with the VD/VT measured by the Douglas bag method (r2 = .99; p < .0001). There was no correlation between the bias of VD/VT and the average VD/VT. As the magnitude of compressible volume increased, the error in VD/VT increased (r2 =.61; p < .001). CONCLUSIONS: The VD/VT can be measured reliably and accurately in intubated pediatric patients using a metabolic monitor. The metabolic monitor method is a convenient and simple alternative to the standard Douglas bag method.

Femoral vascular catheterization in critically ill infants and children.

The success rate and complications from femoral arterial and venous catheterization in infants and children in a university affiliate pediatric intensive care unit were determined prospectively over a 2-year period. We also performed a meta-analysis from published literature to determine the combined estimates of noninfectious and infectious complications (with 95% confidence limits) using the inverse variance-weighted method. Success rates were 94.5% and 94.4% for femoral arterial (n=110) and venous (n=89) catheterizations, respectively, and were related to operator expertise, age, and hemodynamic status. Median age was 2.4 years and 1.1 year for arterial and venous catheterizations, respectively. Immediate complications were hematoma (10.9% arterial, 16.8% venous) and minor bleeding (13.6% arterial, 13.5% venous). Decreased pulses occurred with 7.7% of arterial catheterizations, and lower limb swelling occurred in 9.5% of venous catheterizations. Vascular complications occurred only in infants and resolved within 7-14 days. Catheter-related infections occurred in 1.9% of arterial and 3.6% of venous catheterizations. The mean duration of catheterization was 5.3 days and 6.3 days with femoral arterial and venous catheterizations, respectively. Meta-analysis of published studies shows that the estimates for noninfectious complications were 5.0%, 10.1%, 1.1%, and 1.8% for femoral arterial, femoral venous, axillary arterial, and nonfemoral venous catheters, respectively. The estimates for catheter-related infection were 2.5%, 3.7%, and 3.0% for femoral arterial, femoral venous, and nonfemoral venous catheters, respectively. The meta-analytic estimates for complication rates from published literature are not significantly different from the rates observed in our study. Femoral arterial and venous catheterization in infants and children are safe with an expected high success rate and acceptably low complication rates.

Predictors of extubation success and failure in mechanically ventilated infants and children.

OBJECTIVE: To predict extubation success and failure in mechanically ventilated infants and children using bedside measures of respiratory function. DESIGN: Prospective collection of data. SETTING: A university-affiliated children's hospital with a 51-bed critical care unit. PATIENTS: All infants and children who were mechanically ventilated for at least 24 hrs, except neonates < or = 37 wks gestation and patients with neuromuscular disease. INTERVENTIONS: Bedside measurements of cardiorespiratory function were obtained immediately before extubation. MEASUREMENTS AND MAIN RESULTS: Extubation failure was defined as reintubation within 48 hrs of extubation in the absence of upper airway obstruction. Failure rates were calculated for different ranges (selected a priori) of preextubation measures of breathing effort, ventilatory support, respiratory mechanics, central inspiratory drive, and integrated indices useful in adults. Effort of spontaneous breathing was assessed by the respiratory rate standardized to age, the presence of retractions and paradoxical breathing, inspiratory pressure, maximal negative inspiratory pressure (maximal negative inspiratory pressure), inspiratory pressure/maximal negative inspiratory pressure ratio, and tidal volume indexed to body weight of a spontaneous breath. Ventilatory support was measured by the fraction of inspired oxygen (F10(2)), mean airway pressure, oxygenation index, and the fraction of total minute ventilation provided by the ventilator. Respiratory mechanics were assessed by determination of peak ventilatory inspiratory pressure and dynamic compliance. Central inspiratory drive was assessed by mean inspiratory flow. Frequency to tidal volume ratio and the compliance, rate, oxygenation, and pressure indexed to body weight, the integrated indices useful in predicting extubation failure in adults, were also calculated. Thirty-four of the 208 patients who were studied were reintubated for an overall failure rate of 16.3% (95% confidence interval 11.3% to 21.4%). The reasons for reintubation were poor effort (n = 8), excessive effort (n = 14), altered mental status or absent airway reflexes (n = 2), cardiovascular instability (n = 3), inadequate oxygenation (n = 3), respiratory acidosis (n = 3), and undocumented (n = 1). Extubation failure increased significantly with decreasing tidal volume indexed to body weight of a spontaneous breath, increasing F10(2), increasing mean airway pressure, increasing oxygenation index, increasing fraction of total minute ventilation provided by the ventilator, increasing peak ventilatory inspiratory pressure, or decreasing mean inspiratory flow (p < .05). Dynamic compliance showed a trend of increasing failure rate with decreasing dynamic compliance but did not reach statistical significance (p = .116). Respiratory rate standardized to age, inspiratory pressure, maximal negative inspiratory pressure, inspiratory pressure/maximal negative inspiratory pressure ratio, frequency to tidal volume ratio, and compliance, rate, oxygenation, and pressure did not show any trend in failure rate with increasing or decreasing values. Threshold values that defined a low risk (< or = 10%) and a high risk (> or = 25%) of extubation failure could be determined for tidal volume indexed to body weight of a spontaneous breath, F10(2), mean airway pressure, oxygenation index, fraction of total minute ventilation provided by the ventilator, peak ventilatory inspiratory pressure, dynamic compliance, and mean inspiratory flow. Neither a low nor a high risk of failure could be defined for frequency to tidal volume ratio or the compliance, rate, oxygenation, and pressure (CROP) index. CONCLUSIONS: Bedside measurements of respiratory function can predict extubation success and failure in infants and children. Both a low risk and a high risk of failure can be determined using these measures. Integrated indices useful in adults do not reliably predict extubation success or failure in

Intrahospital transport of critically ill pediatric patients.

OBJECTIVES: To determine the frequency of adverse events during intrahospital transport; to determine the requirement of therapeutic interventions during transport; to test the hypothesis that adverse events that occur during intrahospital transport are due to the transport process itself; and to determine the factors that predict the occurrence of adverse events and the requirement of major therapeutic interventions during transport. DESIGN: A two-phase study in which data were prospectively collected. In phase I, we examined the occurrence rate of adverse events, the requirement for therapeutic interventions, and the factors that predicted adverse events and the requirement of therapeutic interventions. In phase II, we tested the hypothesis that adverse events during transport were due to the transport process itself. SETTING: A 250-bed university children's hospital with a 50-bed intensive care unit (ICU). PATIENTS: Phase I of the study consisted of one hundred and eighty intrahospital transports in 139 patients. These transports included patients who were transferred: a) to the ICU from the operating room, emergency department, or the general ward; b) from the ICU to the operating room; and c) from the ICU for diagnostic or therapeutic procedures. Phase II of the study consisted of 89 transports in 85 patients. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Vital signs and oxygen saturation were measured before and during transport. In phase I, there were no adverse events in 23.9% of transports. There was a significant change in at least one physiologic variable in 71.7% of transports, and at least one equipment-related mishap in 10% of transports. At least one major intervention was performed in 13.9% of transports in response to physiologic deterioration or an equipment-related mishap. There were no arrests or deaths during transport. The requirement for a major procedure was 34.4% in mechanically ventilated patients vs. 9.5% in nonventilated patients. Logistic regression analysis showed that both pretransport Therapeutic Intervention Scoring System and the duration of transport were significantly associated with the requirement of a major intervention and physiologic deterioration, while only the duration of transport was associated with an equipment-related event. The age of the patient and the number of escorts accompanying the transport did not affect the frequency of adverse events. Before transport in phase II study patients, no patient became hypothermic, the changes in physiologic variables were always < 20%, and there was no change > or = 5% in oxygen saturation. Hypothermia occurred in 11.2% of transports. A > or = 20% change in heart rate (15.7%), blood pressure (21.3%), and respiratory rate (23.6%) was seen only during transport. A > 5% change in oxygen saturation (5.6%) was seen only during transport. CONCLUSIONS: Serious physiologic deterioration occurs during intrahospital transport of critically ill children. Severity of illness and the duration of transport are associated with the occurrence of adverse events during transport. The team composition and equipment required on transport must be commensurate with the pretransport severity of illness and the anticipated duration of transport.

Pretransport Pediatric Risk of Mortality (PRISM) score underestimates the requirement for intensive care or major interventions during interhospital transport.

OBJECTIVE: To test the hypothesis that a pretransport Pediatric Risk of Mortality (PRISM) score underestimates the requirement for both intensive care and interventions during pediatric interhospital transport. DESIGN: Prospective, descriptive study. SETTING: All children were treated in a regional hospital and then transported to a pediatric tertiary care center by a pediatric critical care specialty team. PATIENTS: Children (n = 156) with a median age of 1.3 yrs (range newborn to 18 yrs). INTERVENTIONS: None related to the study. MEASUREMENTS AND MAIN RESULTS: Two sets of Pediatric Risk of Mortality scores were calculated: one from data collected over the telephone at the time of the referral (Referral PRISM), and one from both the referring hospital's records and from data collected by the transport team on arrival at the referring hospital and before the team provided any intervention (Team PRISM). The admission area used on arrival at the tertiary care center (intensive care unit [ICU] vs. non-ICU) and the number of major clinical interventions performed by both the referring hospital staff and the transport team were recorded. The Therapeutic Intervention Scoring System was used to assess the cumulative level of medical care provided up to 8 hrs after admission to the pediatric tertiary care hospital. No patient died during transport. The overall in-hospital mortality rate was 5.1%. Median Therapeutic Intervention Scoring System scores were higher for patients admitted to the ICU (16 vs. 4, p < .001). Whereas median PRISM scores were significantly higher in those children admitted to the ICU (4 vs. 0, p < .001), 58 (75%) of 77 ICU admissions had a Team PRISM score of < or = 10. Forty-four (71%) of 62 children who required at least one major intervention at some time during the transport process and 15 (63%) of 24 children who required at least one major intervention by the transport team had a Team PRISM score of < or = 10. Referral PRISM scores underestimated Team PRISM scores. CONCLUSIONS: PRISM scores determined before interhospital transfer of pediatric patients underestimated the requirement for intensive care and the performance of major interventions in the pretransport setting. Many patients with low PRISM scores required intensive care on admission to the receiving hospital and major interventions during the transport process, and, therefore, were not at "low risk" for clinical deterioration. The PRISM score should not be used as a severity of illness measure or triage tool for pediatric interhospital transport.

Positive end-expiratory pressure-induced, calcium-channel-mediated increases in pulmonary vascular resistance in neonatal lambs.

OBJECTIVES: a) To study the dose response of the calcium-channel-mediated increases in pulmonary vascular resistance with different levels of positive end-expiratory pressure; b) to study the reversibility of the calcium-channel mediated increases in pulmonary vascular resistance after discontinuation of positive end-expiratory pressure; and c) to study the effect of cyclooxygenase and lipoxygenase inhibition on the calcium-channel mediated increases in pulmonary vascular resistance. DESIGN: A prospective, multiexperimental, dose response study. SETTING: Laboratory setting in a university hospital. SUBJECTS: Twenty-three 4- to 10-day-old neonatal lambs. INTERVENTIONS AND MEASUREMENTS: Lungs of neonatal lambs were isolated in situ, and perfused at a constant flow rate, and ventilated at a fixed tidal volume and rate. Mean pulmonary arterial pressure responses to the application and discontinuation of four levels (3.7, 7.4, 11, and 14.7 mm Hg) of positive end-expiratory pressure were studied before and after calcium-channel blockade with verapamil (5 mg) (n = 12). In addition, the mean pulmonary arterial pressure response to 11 mm Hg of positive end-expiratory pressure was studied before and after inhibition of cyclooxygenase with indomethacin (10 mg/kg) (n = 6) and lipoxygenase with diethylcarbamazine (100 mg/kg) (n = 5). RESULTS: The magnitude of the calcium-channel-dependent mean pulmonary arterial pressure response 4 mins after the application of positive end-expiratory pressure was dose related (2.1, 3.0, 4.1, and 5.5 mm Hg with 3.7, 7.4, 11.0, and 14.7 mmHg positive end-expiratory pressure, respectively) and entirely reversible on discontinuation of positive end-expiratory pressure with a time course of 2 to 4 mins. Neither indomethacin nor diethylcarbamazine affected the pulmonary arterial pressure responses to positive end-expiratory pressure. Airway pressure changes with positive end-expiratory pressure were not affected by verapamil, indomethacin, or diethylcarbamazine. CONCLUSIONS: The calcium-channel-mediated pulmonary arterial pressure responses with positive end-expiratory pressure, applied during continuous positive pressure breathing, occur even at low levels of positive end-expiratory pressure, are dose dependent, and are not abolished by treatment with indomethacin or diethylcarbamazine.

The use of drugs in emergency airway management in pediatric trauma.

Most patients who require emergency airway control receive drugs to induce rapidly sufficient anesthesia for direct laryngoscopy and endotracheal intubation, but there are no protocols that outline the use of specific drugs in general use. Drugs should safely and rapidly produce (1) unconsciousness; (2) paralysis; and (3) blunt intracranial pressure (ICP) responses to airway procedures. Consequences to be considered include increased ICP, hemorrhagic shock, and a full stomach. To refine the use of drugs used for airway procedures in pediatric trauma patients, the authors reviewed all cases of emergency endotracheal intubation over a recent 12-month period (1) to see whether medications used met the goals of producing unconsciousness and paralysis and blunting ICP responses were met safely; and (2) to identify potential drug-related complications. From July 1, 1990, to June 30, 1991, 60 of 791 children (7.6%) required endotracheal intubation at the scene of injury, at the referring hospital, or in our emergency department (15; 25%). Ten patients died (16.7%). Three fourths were younger than 9 years of age. All except one suffered blunt injuries. Nearly all (95%) suffered head injuries, isolated in 39 of 57 (68.4%) and combined with injuries in other regions in 18 (31.6%). Fifteen patients were in apnea (25%); seven were both apneic and pulseless. Three fourths (45 of 60) had diminished levels of consciousness; one fourth (15 of 60) were awake. Immediate endotracheal intubation proceeded appropriately without drugs in all seven patients in cardiopulmonary arrest. Only eight of the remaining 53 patients (15.1%) received an optimal medication regimen. Many patients with head injury were inadequately protected against increases in ICP. Thiopental, an effective anesthetic agent that effectively lowers intracranial pressure, was not used in 25 of 35 stable patients with isolated head injury (71.4%). Intravenous lidocaine was not used in 38 of 50 head-injured patients in whom it would have been an appropriate adjunct to control increases in ICP (76%). Eight patients received paralyzing agents alone, without sedatives or narcotics. Medications were thought inadequate to relieve the pain and discomfort of laryngoscopy and endotracheal intubation in 32 of the 53 patients who should have received them (60.4%). No paralyzing agents were used in 36 of the 53 instances where it would have been appropriate (67.9%). In two of 11 instances (18.3%) where succinylcholine was administered, no prior nondepolarizing agent was used. Complications of a full stomach at the time of emergency endotracheal intubation became evident in 10 patients (16.7%) who vomited during procedures to control the airway. Two patients (3.3%) aspirated.(ABSTRACT TRUNCATED AT 400 WORDS)

Interhospital transport. A pediatric perspective.

Interhospital transport of children must not be undertaken in a vacuum. Basic medical ethics and federal laws demand that there be some responsibility in providing adequate care during the transport process, and that this care meets or exceeds the level provided by the referring hospital. The care provided must also be appropriate to the severity of illness of the transported children. National guidelines and standards are needed to establish and coordinate a uniform interhospital transport process for critically ill children.

Intrahospital transport of critically ill patients.

Intrahospital transport of critically ill patients must be considered as part of the critical care continuum. The level of care provided must be commensurate with the severity of illness. These transfers are intensive in terms of utilization of personnel and resources. Advance preparation and optimal coordination of the transport process go a long way toward safer transfers of the critically ill.