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Biomedical subjects

S M Tibby

Publications and source records attributed to S M Tibby.

34 records · Page 2Linked to original sources
PubMed2000

Exogenous surfactant supplementation in infants with respiratory syncytial virus bronchiolitis.

Infants with respiratory syncytial virus (RSV) bronchiolitis are deficient in surfactant, both in quantity and ability to reduce surface tension. New evidence suggests surfactant has a role in maintaining the patency of conducting airways, which has implications for RSV bronchiolitis. A randomized, controlled pilot study was undertaken to assess the effects of exogenous surfactant supplementation to RSV-positive infants on pulmonary mechanics, indices of gas exchange, and the phospholipid composition of bronchoalveolar lavage fluid (BALF). Nineteen ventilated infants (median corrected age 4 wk) received either two doses of surfactant (Survanta, 100 mg/kg) within 24 and 48 h of mechanical ventilation (n = 9), or air placebo (n = 10). Static lung compliance and resistance of infants in the placebo but not in the surfactant-treated group became progressively worse over the first 30 h following enrollment. Although no significant acute changes in gas exchange parameters were seen following surfactant, infants in the surfactant group showed a more rapid improvement in oxygenation and ventilation indices over the first 60 h of ventilation. Surfactant status was assessed from the concentration ratio in BALF of the disaturated phospholipid species dipalmitoylphosphatidylcholine to that of the monounsaturated species palmitoyloleoylphosphatidylcholine. This ratio correlated with both lung compliance (positively) and resistance (negatively), and over time increased in the treated group and declined in placebo infants. The data from this pilot study suggest that functional surfactant has a role in maintaining small airway patency as well as lung compliance in infants infected with RSV and an outcome study is now warranted.

Bronchiolitis, Viral↗
PubMed1999

Use of permissive hypercapnia in the ventilation of infants with respiratory syncytial virus infection.

UNLABELLED: We wished to retrospectively evaluate the effects of permissive hypercapnia (PHY) on barotrauma, mortality and length of stay when applied to ventilated infants with respiratory syncytial virus (RSV) bronchiolitis. Nineteen control infants with RSV induced respiratory failure were treated with conventional ventilation (April 1991-January 1994), after which time PHY was adopted as unit policy. A further 28 infants were then treated with PHY (January 1994 April 1996). Demographic and physiological data were collected from admission, and outcome variables including length of stay, barotrauma and mortality were recorded. The PHY group showed a significantly higher mean pCO2 (7.6 vs 5.2 kPa), a lower mean pH (7.34 vs 7.40), and a reduction in maximal peak inspiratory pressures (25 vs 30 cmH2O). Mortality, barotrauma, use of neuromuscular blockade and nosocomial infection did not differ between groups. There was a trend towards increased length of ventilation in the PHY group (median 7 vs 5 days). CONCLUSION: Based on this retrospective data we can show no benefit for the use of permissive hypercapnia as a ventilatory strategy in this patient group. A prospective randomised controlled trial is warranted to accurately assess the outcome variables and cost implications of this strategy.

Barotrauma↗
PubMed1999

Adrenal insufficiency in septic shock.

BACKGROUND: Functional adrenal insufficiency has been documented in critically ill adults. OBJECTIVE: To document the incidence of adrenal insufficiency in children with septic shock, and to evaluate its effect on catecholamine requirements, duration of intensive care, and mortality. SETTING: Sixteen-bed paediatric intensive care unit in a university hospital. METHODS: Thirty three children with septic shock were enrolled. Adrenal function was assessed by the maximum cortisol response after synthetic adrenocorticotropin stimulation (short Synacthen test). Insufficiency was defined as a post-Synacthen cortisol increment < 200 nmol/l. RESULTS: Overall mortality was 33%. The incidence of adrenal insufficiency was 52% and children with adrenal insufficiency were significantly older and tended to have higher paediatric risk of mortality scores. They also required higher dose vasopressors for haemodynamic stability. In the survivor group, those with adrenal insufficiency needed a longer period of inotropic support than those with normal function (median, 3 v 2 days), but there was no significant difference in duration of ventilation (median, 4 days for each group) or length of stay (median, 5 v 4 days). Mortality was not significantly greater in children with adrenal insufficiency than in those with adequate adrenal function (6 of 17 v 5 of 16, respectively). CONCLUSION: Adrenal insufficiency is common in children with septic shock. It is associated with an increased vasopressor requirement and duration of shock.

Adolescent↗
PubMed1999

Capillary refill and core-peripheral temperature gap as indicators of haemodynamic status in paediatric intensive care patients.

OBJECTIVES: Capillary refill time is an important diagnostic adjunct in the acute resuscitation phase of the shocked child. This study assesses its relation to commonly measured haemodynamic parameters in the postresuscitation phase when the child has reached the intensive care unit, and compares this with core-peripheral temperature gap. METHODS: Ninety standardised measurements of capillary refill time were made on 55 patients, who were divided into postcardiac surgery (n = 27), and general (n = 28), most of whom had septic shock (n = 24). A normal capillary refill time was defined as < or = 2 seconds. Measured haemodynamic variables included: cardiac index, central venous pressure, systemic vascular resistance index, stroke volume index (SVI), and blood lactate. Seventy measurements were made on patients while being treated with inotropes or vasodilators. RESULTS: Capillary refill time and temperature gap both correlated poorly with all haemodynamic variables among post-cardiac surgery children. For general patients, capillary refill time was related to SVI and lactate; temperature gap correlated poorly with all variables. General patients with a prolonged capillary refill time had a lower median SVI (28 v 38 ml/m2) but not a higher lactate (1.7 v 1.1 mmol/l). A capillary refill time of > or = 6 seconds had the best predictive value for a reduced SVI. CONCLUSION: Among ventilated, general intensive care patients, capillary refill time is related weakly to blood lactate and SVI. A normal value for capillary refill time of < or = 2 seconds has little predictive value and might be too conservative for this population; septic shock.

Body Temperature Regulation↗
PubMed1999

Diagnostic markers of infection: comparison of procalcitonin with C reactive protein and leucocyte count.

BACKGROUND: Procalcitonin has been advocated as a marker of bacterial infection. OBJECTIVE: To evaluate diagnostic markers of infection in critically ill children, comparing procalcitonin with C reactive protein and leucocyte count in a paediatric intensive care unit (PICU). METHODS: Procalcitonin, C reactive protein, and leucocyte count were measured in 175 children, median age 16 months, on admission to the PICU. Patients were classified as: non-infected controls (43); viral infection (14); localised bacterial infection without shock (25); bacterial meningitis/encephalitis (10); or septic shock (77). Six children with "presumed septic shock" (without sufficient evidence of infection) were analysed separately. Optimum sensitivity, specificity, predictive values, and area under the receiver operating characteristic (ROC) curve were evaluated. RESULTS: Admission procalcitonin was significantly higher in children with septic shock (median 94.6; range 3.3-759.8 ng/ml), compared with localised bacterial infection (2.9; 0-24.3 ng/ml), viral infection (0.8; 0-4.4 ng/ml), and non-infected controls (0; 0-4.9 ng/ml). Children with bacterial meningitis had a median procalcitonin of 25.5 (7.2-118.4 ng/ml). Area under the ROC curve was 0.96 for procalcitonin, 0.83 for C reactive protein, and 0.51 for leucocyte count. Cut off concentrations for optimum prediction of septic shock were: procalcitonin > 20 ng/ml and C reactive protein > 50 mg/litre. A procalcitonin concentration > 2 ng/ml identified all patients with bacterial meningitis or septic shock. CONCLUSION: In critically ill children the admission procalcitonin concentration is a better diagnostic marker of infection than C reactive protein or leucocyte count. A procalcitonin concentration of 2 ng/ml might be useful in differentiating severe bacterial disease in infants and children.

Adolescent↗
PubMed1998

The outcome of patients with upper airway obstruction transported to a regional paediatric intensive care unit.

UNLABELLED: The diagnoses, transfer, management and outcome of patients with upper airway obstruction (UAO) admitted from district general hospitals (DGH) to a regional paediatric intensive care unit were retrospectively reviewed over a 3.5-year period. Sixty-seven patient episodes were analysed. Fifty-two cases (78%) underwent tracheal intubation prior to transport with a low morbidity for both procedures. The most common diagnosis was viral croup (n = 34, 51%) with a median duration of intubation of 5 days, with subglottic stenosis being the next most common category (n = 10, 15%), median duration of intubation 7 days. Inhaled budesonide was used prior to intubation in 12 (35%) of those with croup, and inhaled bronchodilators in 28%, possibly reflecting diagnostic uncertainty. Patients with croup treated with budesonide were significantly less likely to require intubation (P = 0.04). The re-intubation rate for patients with viral croup was uncomfortably high at 16% (4/25) despite the routine use of prednisolone throughout the intubation period. Successful extubation of patients with viral croup could not be predicted by age (P = 0.31), length of intubation (P = 0.94), endotracheal tube size, (P = 0.60) abnormalities on the chest X-ray (P = 1.0), or presence of secondary bacterial infection (P = 0.23). CONCLUSION: Although viral croup remains the most common diagnostic category presenting at the DGH level with severe UAO, a wide range of other diagnoses is seen. Despite clear evidence of benefit, steroid administration to children presenting at the DGH with viral croup has not become routine practice. Once intubated, no reliable predictors of successful extubation were found amongst this patient group.

Airway Obstruction↗
PubMed1998

Early detection of necrotizing enterocolitis by gastrointestinal tonometry.

The diagnosis of necrotizing enterocolitis (NEC) in neonates has traditionally depended on a combination of clinical signs, biochemical parameters and radiological changes. The measurement of intramucosal pH by gastrointestinal tonometry provides a simple means of long-term monitoring which may detect the development of NEC before conventional techniques. We present our experience of tonometry in two 'at risk' term neonates with Hypoplastic Left Heart Syndrome.

Enterocolitis, Pseudomembranous↗
PubMed1998

Gastric tonometry in septic shock.

OBJECTIVES: To investigate the prognostic value of intramucosal pH (pHi) and the relation among pHi, arterial pH, base excess, and lactate in children with septic shock. DESIGN: Children admitted to the paediatric intensive care unit with a diagnosis of septic shock were prospectively enrolled. A gastrointestinal tonometer (Tonometrics Division, Instrumentarium Corporation, Helsinki, Finland) was placed into the stomach and intramucosal pH, arterial pH, base deficit, and lactate were measured on admission and six hours later. Sequential data were analysed on 24 patients (17 survivors, seven non-survivors), median age 46 months (range: 2.8-168 months). RESULTS: Median pHi on admission was 7.39 (interquartile range 7.36-7.51) in survivors compared with 7.2 (interquartile range 7.18-7.35) in non-survivors (p = 0.01). There was no significant difference in arterial pH, base excess, or lactate among survivors and non-survivors. Admission pHi < 7.32 predicted mortality with sensitivity (57%), specificity (94%), and positive predictive value (80%). Patients with admission pHi < 7.32 who failed to improve > or = 7.32 within six hours (n = 3) had 100% mortality. CONCLUSION: In children with septic shock the admission pHi is significantly lower in non-survivors. pHi is a better prognostic indicator of mortality than either standard acid-base values or lactate. pHi < 7.32 that does not improve within six hours is associated with a poor prognosis.

Adolescent↗
PubMed1997

Clinical validation of cardiac output measurements using femoral artery thermodilution with direct Fick in ventilated children and infants.

OBJECTIVE: To validate clinically cardiac output (CO) measurements using femoral artery thermodilution in ventilated children and infants by comparison with CO estimated from the Fick equation via a metabolic monitor. DESIGN: Prospective, comparison study. SETTING: Paediatric intensive care unit of a university hospital. PATIENTS: 24 ventilated infants and children, aged 0.3 to 175 months (median age 19 months). INTERVENTIONS: Oxygen consumption measurements were made and averaged over a 5-min period, at the end of which arterial and mixed venous blood samples were taken and oxygen saturations measured by co-oximetry, with CO being calculated using the Fick equation. Over this 5-min period, five sets of femoral arterial thermodilution (FATD) measurements were made and averaged. One comparison of CO values was made per patient. RESULTS: Mean Fick CO was 2.55 l/min (range 0.24 to 8.71 l/min) and mean FATD CO was 2.51 l/min (range 0.28-7.96 l/min). The mean bias was 0.03 l/min (95% confidence interval -0.07 to 0.14 l/min), with limits of agreement of -0.45 to 0.52 l/min. When indexed to body surface area, the mean Fick cardiac index became 3.51 l/min per m2 (1.52-6.98 l/min per m2) and mean FATD 3.49 l/min per m2 (1.74-6.84 l/min per m2). The mean bias was 0.02 l/min per m2 (95% confidence interval -0.11 to 0.15 l/min per m2) with limits of agreement of-0.57 to 0.61 l/min per m2. The mean FATD coefficient of variation was 5.8% (SEM 0.5%). CONCLUSIONS: FATD compares favourably with Fick derived CO estimates in infants and children and may represent an advance in haemodynamic monitoring of critically ill children.

Adolescent↗
PubMed1997

Continuous intra-arterial blood-gas monitoring in infants and children with cyanotic heart disease.

We have evaluated the accuracy and reliability of the Paratrend 7 continuous blood-gas analyser in infants and small children under conditions of severe hypoxaemia admitted to the paediatric intensive care unit in the perioperative period with cyanotic congenital heart disease. PO2, PCO2 and pH (hydrogen ion concentration) were measured continuously via a femoral arterial sensor and compared with 100 simultaneous paired arterial blood-gas measurements. Data were analysed by Bland-Altman analysis for bias and precision. Sensors were placed in 10 children of median age 5.43 (range 0.03-45) months, median weight 3.74 (2.79-15.4) kg and remained in place for up to 27 h after operation. PO2 values were 2.5-8.2 kPa (median 5.3 kPa). Co-oximeter saturation ranged from 37.1% to 90.6% (median 75.8%). Bias and precision values were 0.04/0.87 kPa for PO2, -0.44/0.74 kPa for PCO2 and -2.61/6.98 nmol litre-1 for hydrogen ion concentration (i.e. 0.02/0.06 for pH). We conclude that perioperative continuous arterial gas monitoring is clinically accurate under conditions of severe hypoxaemia in small infants and children with cyanotic congenital heart disease.

Blood Gas Analysis↗
PubMed1997

Serum lactate as a predictor of mortality after paediatric cardiac surgery.

OBJECTIVE: To assess the value of sequential lactate measurement in predicting postoperative mortality after surgery for complex congenital heart disease in children. DESIGN: Prospective observational study. SETTING: Sixteen bedded paediatric intensive care unit (PICU). SUBJECTS: Ninety nine children (90 survivors, nine non-survivors). MEASUREMENTS: Serum lactate and base deficit were measured on admission and every six hours thereafter. Data were analysed by Mann-Whitney and Fisher's exact tests. RESULTS: There was considerable overlap in initial lactate values between the survivor and non-survivor groups. Initial lactate was significantly raised in non-survivors (median 8.7, range 1.9-17.6 mmol/l) compared with survivors (median 2.4, range 0.6-13.6 mmol/l) (p = 0.0002). Twenty one patients (21.1%) with initial lactate concentrations greater than 4.5 mmol/l survived to PICU discharge. Using receiver operating characteristic analysis an initial lactate of 6 mmol/l had the optimum predictive value for mortality. Initial postoperative serum lactate > 6 mmol/l predicted mortality with sensitivity 78%, specificity 83%, and positive predictive value of only 32%. CONCLUSION: Initial lactate concentrations have poor positive predictive value for mortality. The routine measurement of lactate for this purpose cannot be justified in clinical practice.

Biomarkers↗
PubMed1997

Clinicians' abilities to estimate cardiac index in ventilated children and infants.

OBJECTIVES: To evaluate the ability of clinicians involved in the provision of paediatric intensive care to estimate cardiac index in ventilated children, based on physical examination and clinical and bedside laboratory data. METHODS: Clinicians were exposed to all available haemodynamic and laboratory data for each patient, allowed to make a physical examination, and asked to first categorize cardiac index as high, high to normal, low to normal, or low, and then to quantify this further with a numerical estimate. Cardiac index was measured simultaneously by femoral artery thermodilution (coefficient of variation 5.37%). One hundred and twelve estimates were made by 27 clinicians on 36 patients (median age 34.5 months). RESULTS: Measured cardiac index ranged from 1.39 to 6.84 1/min/m2. Overall, there was poor correlation categorically (kappa statistic 0.09, weighted kappa 0.169) and numerically (r = 0.24, 95% confidence interval 0.06 to 0.41), although some variation was seen among the various levels of seniority. CONCLUSION: Assuming that objective measurement, and hence manipulation, of haemodynamic variables may improve outcome, these findings support the need for a safe, accurate, and repeatable technique for measurement of cardiac index in children who are critically ill.

Body Surface Area↗
PubMed1995

Continuous haemodynamic monitoring in children: use of transoesophageal Doppler.

A wide range of invasive and non-invasive techniques for monitoring the haemodynamic condition of critically ill patients is now available. A general reluctance on the part of paediatric intensive care specialists to use pulmonary artery thermodilution catheters and the need for constant realignment of hand-held Doppler probes has necessitated the search for a technique which is relatively non-invasive and provides continuous information on the haemodynamic condition of critically ill paediatric patients. We sought to establish if transoesophageal Doppler fulfilled these criteria. Eleven children who had recently undergone cardiac surgery were studied. Median age was 39 months and weight 14.9 kg. Five simultaneous pairs of measurements of cardiac index (CI: thermodilution) and minute distance (MD: transoesophageal Doppler) were made, as a baseline, when each child was haemodynamically stable. Following a fluid challenge, five repeat pairs of measurements were made. The mean percentage changes for CI and MD were 16.4% (range 5.3-44%) and 16.6% (3.4-47.7%), respectively. The average coefficients of variation for measurements of CI and MD were 3.5% and 2.9%, respectively. The mean difference in percentage change between CI and MD was -0.5% (95% confidence interval for the bias -4% to 3%; limits of agreement -10.7 to +9.7%). Our study indicates that transoesophageal Doppler is reproducible, easy to use and provides clinically acceptable information when following changes in CI in haemodynamically stable paediatric patients.

Adolescent↗