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Biomedical subjects

I A Murdoch

Publications and source records attributed to I A Murdoch.

At least 55 records · Page 3Linked to original sources
PubMed1997

Extracorporeal support for intractable cardiorespiratory failure due to meningococcal disease.

BACKGROUND: Meningococcal disease is still associated with considerable mortality, despite the use of early antibiotics and management in specialised intensive care units, due principally to early refractory myocardial depression and hypotension as well as severe acute respiratory distress syndrome. Extracorporeal membrane oxygenation (ECMO) is a complex technology that uses a modified "heart-lung" machine to provide temporary cardiac and respiratory support. We reviewed the UK and Australian experience of the use of ECMO in patients with refractory cardiorespiratory failure due to meningococcal disease. METHODS: The records from all 12 known patients supported with ECMO for meningococcal disease in the UK and Australia since 1989 were reviewed. FINDINGS: 12 patients (aged 4 months to 18 years, median 26 months) with meningococcal disease received ECMO over 8 years. In seven patients, ECMO was required early for cardiac support for intractable shock within 36 h of admission to intensive care. In the other five patients, ECMO was indicated for respiratory failure due to severe adult respiratory distress syndrome, which tended to occur later in the disease. The paediatric risk of mortality score ranged from 13 to 40 (median 29, median predicted risk of mortality 72%). Six of the 12 patients required cardiopulmonary resuscitation before ECMO and the other six were deteriorating despite maximal conventional therapy. Overall, eight of the 12 patients survived, with six leading functionally normal lives at a median of 1 year (range 4 months to 4 years) of follow-up. INTERPRETATION: ECMO might be considered to support patients with intractable cardiorespiratory failure due to meningococcal disease who are not responding to conventional treatment.

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↗
PubMed1996

A comparison of pulmonary and femoral artery thermodilution cardiac indices in paediatric intensive care patients.

We have assessed the agreement between pulmonary artery and femoral artery (COLD) thermodilution measurements of the cardiac index (Cl) in a group of paediatric intensive care patients. The COLD method gave consistently higher cardiac index values than the pulmonary artery catheter (PAC); however, the difference was small, with a mean value of 0.19 l/min-1 m-2 or 4.4% of the mean cardiac index. This difference is not clinically important and suggests that, under these circumstances, the COLD system provides an acceptable alternative to the pulmonary artery catheter for measurement of the cardiac index at the bedside.

Cardiac Output↗
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↗
PubMed1994

Improved arterial oxygenation in children with the adult respiratory distress syndrome: the prone position.

Seven ventilated children with the adult respiratory distress syndrome (ARDS) were studied. While supine and haemodynamically stable, baseline arterial blood-gas analyses and haemodynamic measurements, including cardiac output, were performed. Each child was then turned prone and 30 min later a repeat set of measurements were made. Following this, the children were returned to the supine position and 30 min later a final set of measurements were performed. Ventilation and inotropic support remained unchanged during these positional changes. No significant effect on heart rate, mean systemic arterial blood pressure and cardiac output occurred following these positional changes (p > 0.05; Friedman's ANOVA). Arterial oxygen saturation significantly improved, however, when nursed in the prone position (p < 0.02). Similarly, oxygen delivery significantly increased (p < 0.02). The prone position improves arterial oxygenation and oxygen delivery in children with ARDS. By adopting the prone position, in ventilated children with ARDS, we surmise that realistic gas exchange targets may be reachable with lower levels of inspired oxygen and/or peak airway pressures.

Cardiac Output↗
PubMed1994

Accuracy of central venous pressure measurements in the inferior vena cava in the ventilated child.

We compared central venous pressure measurements from three sites, superior vena cava, inferior vena cava and right atrium, in 12 children undergoing cardiac catheterization whilst on assisted ventilation. There was no significant difference between the mean pressures in the superior vena cava and the inferior vena cava. Furthermore, there was also no difference between the mean pressures in the inferior vena cava and the right atrium. Because of the greater safety of the placement of pressure monitoring lines in the inferior vena cava via the femoral vein, this approach should be the preferred route for central venous pressure monitoring in children.

Blood Pressure Determination↗
PubMed1994

Perioperative haemodynamic effects of an intravenous infusion of calcium chloride in children following cardiac surgery.

Twelve children received an infusion of 10% calcium chloride 0.1 ml/kg to a maximum dose of 5 ml, infused over 5 min, following open heart surgery. Blood ionized calcium, systemic arterial pH, cardiac index, mean systemic arterial blood pressure and systemic vascular resistance index were measured at baseline and repeated 20 and 40 min following completion of the infusion. There was considerable overlap, with no significant differences in the response to the calcium chloride infusion between children with ionized hypocalcaemia (< 1.1 mmol/l) and those with ionized normocalcaemia when its effect on percentage change in either the haemodynamic or biochemical measurements was assessed (p > 0.2 for all measurements; Mann-Whitney). For this reason they were treated as a single group. Significant changes from baseline were noted in mean systemic arterial pressure (p < 0.02), cardiac index (p < 0.01) and systemic vascular resistance index (p < 0.01) after completion of the calcium chloride infusion when analysed using Friedman's two-way analysis of variance. A significant increase in mean systemic arterial blood pressure occurs after an infusion of 10% calcium chloride as a direct result of an increase in the systemic vascular resistance index with a concomitant decrease in cardiac index.

Blood Pressure↗