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Biomedical subjects

I A Murdoch

Publications and source records attributed to I A Murdoch.

At least 19 recordsLinked to original sources
PubMed2005

Should parents accompany critically ill children during inter-hospital transport?

BACKGROUND: Parental accompaniment during inter-hospital transportation (retrieval) of critically ill children is not commonplace in the United Kingdom. METHODS: A three month pilot of parental accompaniment was undertaken in 2002 (143 retrievals), after which time the policy was adopted as standard practice. A follow up audit was performed in 2004 (136 retrievals). RESULTS: Findings were remarkably consistent between the two periods. Staff perceived little or no added stress during the majority of transfers (96% in 2002, 98% in 2004), and felt able to perform medical interventions without hindrance (98% in 2002, 100% in 2004). There was good agreement between medical and nursing staff regarding perception of stress and ability to perform interventions (phi statistic 0.57 to 1.00). Adverse events occurred during 11 (3.9%) retrievals; six of these involved a parent exclusively. Stress tended to be associated with adverse events or parental behaviour rather than disease acuity. Staff vetoed the offer of accompaniment on 11 occasions, for a variety of reasons. The majority of parents found the experience safe, beneficial, and perceived a reduction in stress as a result. These data may inform other retrieval services who are considering adopting a similar policy.

Adolescent↗
PubMed2003

Incidence of hyponatraemia and hyponatraemic seizures in severe respiratory syncytial virus bronchiolitis.

AIM: To document the incidence and early evolution of hyponatraemia (serum sodium < 136 mmol l(-1)) associated with respiratory syncytial virus (RSV) bronchiolitis in infants requiring intensive care. METHODS: In a retrospective review over two winter seasons, 130 infants were admitted with confirmed RSV infection, of whom 39 were excluded because of either pre-existing risk factors for hyponatraemia: diuretic therapy (n = 14), cardiac disease (n = 10), renal disease (n = 2) or lack of admission sodium data (n = 13). RESULTS: The incidence of admission hyponatraemia in the remaining infants (median age 6 wk) was 33% (30/91), with 11% (10/91) exhibiting a serum sodium less than 130 mmol l(-1) . Hyponatraemic and normonatraemic infants were of a similar age (median 6 vs 7 wk, p = 0.82). With fluid restriction and diuretic therapy, the incidence of hyponatraemia at 48 h had decreased to 3.3%, odds ratio 0.07 (95% confidence interval 0.02-0.24, p < 0.001). Four infants (4%) suffered hyponatraemic seizures at admission (sodium 114-123 mmol l(-1)); three had received hypotonic intravenous fluids at 100-150 ml kg(-1) d(-1) before referral to intensive care. All four were managed successfully with hypertonic (3%) saline, followed by fluid restriction, resulting in immediate termination of seizure activity and normalization of serum sodium values over 48 h. CONCLUSION: Hyponatraemia is common among infants with RSV bronchiolitis presenting to intensive care. Neurological complications may occur and fluid therapy in vulnerable infants should be tailored to reduce this risk.

Apnea↗
PubMed2003

Monitoring cardiac function in intensive care.

Systolic cardiac function results from the interaction of four interdependent factors: heart rate, preload, contractility, and afterload. Heart rate can be quantified easily at the bedside, while preload estimation has traditionally relied on invasive pressure measurements, both central venous and pulmonary artery wedge. These have significant clinical limitations; however, adult literature has highlighted the superiority of several novel preload measures. Measurement of contractility and afterload is difficult; thus in clinical practice the bedside assessment of cardiac function is represented by cardiac output. A variety of techniques are now available for cardiac output measurement in the paediatric patient. This review summarises cardiac function and cardiac output measurement in terms of methodology, interpretation, and their contribution to the concepts of oxygen delivery and consumption in the critically ill child.

Biomarkers↗
PubMed2003

Hypoalbuminaemia in critically ill children: incidence, prognosis, and influence on the anion gap.

AIMS: Hypoalbuminaemia has significance in adult critical illness as an independent predictor of mortality. In addition, the anion gap is predominantly due to the negative charge of albumin, thus hypoalbuminaemia may lead to its underestimation. We examine this phenomenon in critically ill children, documenting the incidence, early evolution, and prognosis of hypoalbuminaemia (<33 g/l), and quantify its influence on the anion gap. METHODS: Prospective descriptive study of 134 critically ill children in the paediatric intensive care unit (ICU). Paired arterial blood samples were taken at ICU admission and 24 hours later, from which blood gases, electrolytes, and albumin were measured. The anion gap (including potassium) was calculated and then corrected for albumin using Figge's formula. RESULTS: The incidence of admission hypoalbuminaemia was 57%, increasing to 76% at 24 hours. Neither admission hypoalbuminaemia, nor extreme hypoalbuminaemia (<20 g/l) predicted mortality; however, there was an association with increased median ICU stay (4.9 v 3.6 days). After correction for albumin the incidence of a raised anion gap (>18 mEq/l) increased from 28% to 44% in all samples (n = 263); this discrepancy was more pronounced in the 103 samples with metabolic acidosis (38% v 73%). Correction produced an average increase in the anion gap of 2.7 mEq/l (mean bias), with limits of agreement of +/-3.7 mEq/l. CONCLUSION: Admission hypoalbuminaemia is common in critical illness, but is not an independent predictor of mortality. However, failure to correct the anion gap for albumin may underestimate the true anion gap, producing error in the interpretation of acid-base abnormalities. This may have treatment implications.

Acid-Base Imbalance↗
PubMed2002

Soluble Fas may be a proinflammatory marker after cardiopulmonary bypass in children.

OBJECTIVES: Ischemia-reperfusion injury after cardiopulmonary bypass is known to provoke an inflammatory response, which can be attenuated with steroid pretreatment. Cardiopulmonary bypass is also known to stimulate apoptosis. Induction of the cellular apoptotic cascade occurs via interaction between two membrane receptors: Fas and Fas ligand. Both molecules also exist in soluble forms, whose significance remains undetermined; however, both may have a proinflammatory role. We aimed to document the temporal profile of soluble Fas and soluble Fas ligand after cardiopulmonary bypass and to investigate whether steroid pretreatment alters this response. METHODS: The study was of a non-randomized, non-blinded, prospective nature. Twenty-seven infants were monitored prospectively, of whom 13 received dexamethasone at induction of anesthesia. Soluble Fas, soluble Fas ligand, and interleukin 6 were measured from induction of anesthesia until 24 hours after admission to the intensive care unit. Data on clinical and laboratory variables were also collected at the same time intervals. RESULTS: As expected, dexamethasone pretreatment attenuated interleukin 6 release and the clinical systemic inflammatory response after bypass. Soluble Fas showed a remarkably similar profile to interleukin 6, in terms of temporal release and attenuation with steroids. There was also a correlation between maximum soluble Fas and markers of capillary leak (colloid requirement and drain loss). Conversely, soluble Fas ligand release was unchanged by cardiopulmonary bypass and steroid administration. However, patients with higher soluble Fas ligand levels exhibited a more dramatic drop and delayed recovery in monocyte count, consistent with the role of this molecule in apoptosis. CONCLUSIONS: Release of soluble Fas and soluble Fas ligand follows a markedly different temporal profile after cardiopulmonary bypass. The similarity between soluble Fas and interleukin 6, together with the attenuation of both with steroids, may suggest a role for soluble Fas as a proinflammatory marker.

Anti-Inflammatory Agents↗
PubMed2002

High-frequency oscillation in adolescents.

BACKGROUND: High-frequency oscillation (HFO) is a widely used lung-protective ventilatory strategy in paediatric and neonatal acute lung injury. Its safe and effective use has been hindered by inadequate recruitment of the lung during oscillation and, until recently, the lack of an adequately powered oscillator for use in adult practice. METHODS: We present data from three adolescents with severe acute respiratory distress syndrome (ARDS) who received HFO with the Sensormedics 3100B oscillator after failure of conventional mechanical ventilation. A manual recruitment manoeuvre was used in all patients prior to mechanical ventilation (conventional or HFO) and following tracheal suctioning or disconnection from the ventilator. Changes in oxygenation index were used to assess therapy. RESULTS: All patients showed at least a 25% reduction in oxygenation index within 2 h of HFO, with return to conventional ventilation after 27-65 h. CONCLUSIONS: We found HFO, in conjunction with manual recruitment and prone positioning, to be a well-tolerated mode of ventilation in adolescents with ARDS and who were unresponsive to conventional ventilation. Given this success we hope to renew interest in this method for adults with ARDS, together with concurrent use of manual recruitment.

Adolescent↗
PubMed2002

A comparison of three scoring systems for mortality risk among retrieved intensive care patients.

AIMS: To assess the impact of two paediatric intensive care unit retrieval teams on the performance of three mortality risk scoring systems: pre-ICU PRISM, PIM, and PRISM II. METHODS: A total of 928 critically ill children retrieved for intensive care from district general hospitals in the south east of England (crude mortality 7.8%) were studied. RESULTS: Risk stratification was similar between the two retrieval teams for scores utilising data primarily prior to ICU admission (pre-ICU PRISM, PIM), despite differences in case mix. The fewer variables required for calculation of PIM resulted in complete data collection in 88% of patients, compared to pre-ICU PRISM (24%) and PRISM II (60%). Overall, all scoring systems discriminated well between survival and non-survival (area under receiver operating characteristic curve 0.83-0.87), with no differences between the two hospitals. There was a tendency towards better discrimination in all scores for children compared to infants and neonates, and a poor discrimination for respiratory disease using pre-ICU PRISM and PRISM II but not PIM. All showed suboptimal calibration, primarily as a consequence of mortality over prediction among the medium (10-30%) mortality risk bands. CONCLUSIONS: PIM appears to offer advantages over the other two scores in terms of being less affected by the retrieval process and easier to collect. Recalibration of all scoring systems is needed.

Child↗
PubMed2001

Are transoesophageal Doppler parameters a reliable guide to paediatric haemodynamic status and fluid management?

OBJECTIVE: Transoesophageal Doppler (TOD) has been used in adults to optimise left ventricular filling on the basis of the waveform parameters. We wished to see if a similar relationship exists in children, specifically: (a) whether change in thermodilution stroke volume (SV) following a fluid bolus corresponded to change in Doppler stroke distance, Doppler corrected flow time (FTc), or central venous pressure (CVP); (b) whether a response to fluid challenge (defined as an increase in SV of greater than 10%) can be predicted on the basis of an absolute value for FTc or CVP prior to fluid bolus; and (c) the relationship between FTc and systemic vascular resistance index. DESIGN: Prospective, comparison study. SETTING: Sixteen-bed paediatric intensive care unit of a university hospital. PATIENTS: Ninety-four ventilated children were studied, median (range) age 25 months (4 days- 16 years). Diagnoses included: post-cardiac surgery (n = 58), sepsis/multi-organ failure (n = 29), respiratory disease (n = 5), and other (n = 2). INTERVENTIONS: A 4-MHz, 5.5-mm diameter, flexible TOD probe was placed when patients were haemodynamically stable. Five consecutive measurements of stroke distance and FTc were made and averaged, concurrently with five SV measurements by femoral artery thermodilution. SV was then augmented by administration of fluid (10 ml/kg), and haemodynamic recordings were repeated. MEASUREMENTS AND MAIN RESULTS: The median (range) SV was 17 ml (2-64 ml). The median coefficients of variation were 3.9 % for SV, 3.5 % for stroke distance, and 3.1% for FTc. Changes in SV were accurately tracked by changes in stroke distance (mean bias 1.8 %, limits of agreement +/- 17%), but not by FTc or CVP. FTc was weakly inversely correlated with systemic vascular resistance (r = -0.15, P < 0.05). Among non-cardiac patients (n = 36), the optimal FTc that predicted an improvement in SV following fluid bolus was 0.394 s (area under ROC curve 0.756), giving a sensitivity of 90 %, specificity of 62 %, positive predictive value of 47 %, and a negative predictive value of 94 %. CVP was a poor predictor for all patient groups. CONCLUSIONS: TOD stroke distance is able to follow changes in SV following fluid bolus amongst ventilated children, and can predict when further volume loading is unlikely to improve SV amongst general, but not cardiac ICU patients. CVP is a poor discriminator of volume status in this group of patients.

Adolescent↗
PubMed2001

The value of the chloride: sodium ratio in differentiating the aetiology of metabolic acidosis.

OBJECTIVE: Stewart's physicochemical approach to acid-base balance defines the aetiology of a metabolic acidosis by quantifying anions of tissue acids (TA), which consist of unmeasured anions (UMA) and/or lactate. We hypothesised that an increase in TA during metabolic acidosis would lead to a compensatory fall in the plasma chloride (Cl) relative to sodium (Cl:Na ratio) in order to preserve electro-neutrality. Thus, the Cl:Na ratio could be used as a simple alternative to the anion gap in identifying raised TA. PATIENTS: Two hundred and eighty two consecutive patients who were admitted to our Paediatric Intensive Care were enrolled in the study. INTERVENTIONS: We obtained 540 samples (admission n = 282, 24 h n = 258) for analysis of blood chemistry, lactate and quantification of TA and UMA. Samples were subgrouped into those with metabolic acidosis (standard bicarbonate < 22 mmol/l) either with or without increased UMA (> 3 mEq/l). MEASUREMENTS AND RESULTS: Metabolic acidosis occurred in 46% of samples, of which 52.3% (120/230) had increased UMA. The dominant component of TA was UMA rather than lactate, and these two components did not always rise in tandem. Our hypothesis of relative hypochloraemia was supported by a lower Cl:Na ratio (P < 0.0001) but not a lower absolute Cl (P = 0.5) in the acidotic subgroup with raised UMA, and by the inverse relationship between TA and the Cl:Na ratio. (coefficient of determination (r2) = 0.37, P < 0.0001). The best discriminator for the presence of raised TA was the albumin-corrected anion gap (AGcorr), however, this could not track changes in TA with clinical accuracy. The Cl:Na ratio discriminated reasonably well, a ratio of < 0.75 identified TA (positive predictive value (PPV) 88%) with a likelihood ratio (LR) similar to the AG (7.8 vs7.4). Conversely, a high ratio (> 0.79) excluded TA (PPV 81%, LR 4.5). Base deficit (BD) and lactate performed poorly. CONCLUSION: In metabolic acidosis due to TA, plasma Cl concentration decreases relative to sodium. The Cl:Na ratio is a simple alternative to the AG for detecting TA in this setting.

Acidosis↗
PubMed2000

Early hyperlactataemia in critically ill children.

OBJECTIVE: To examine the relationships between early hyperlactataemia, acidosis, organ failure, and mortality in children admitted to intensive care. DESIGN: Prospective observational study. Children with lactate levels > 2 mmol/l were eligible for enrolment. Post-operative patients and those with inherited metabolic disease were excluded. Seven hundred and five children admitted to intensive care were screened, and 50 children with hyperlactataemia (incidence 7%), aged 20.3 months (0.1-191) were enrolled and followed up. The Paediatric Risk of Mortality (PRISM) score, Multiorgan System Failure (MOSF) score, length of ICU stay, and outcome were recorded. Data were collected for lactate (mmol/l), pH, and base excess (BE) until 24 h after admission. Data are reported as median (range) and were analysed by the Mann-Whitney, Fisher's Exact, and Kruskal-Wallis tests, and chisquared test for trend. RESULTS: Overall mortality in the screening group was 70/705 (10%). In the study group (n = 50) median PRISM score was 19 (4-49), median MOSF score 2 (1-4), and observed mortality 32/50 (64%). Median duration of ICU stay was 6 days (2-32) in survivors, and median time until death 3 days (0-13) in nonsurvivors. Eleven nonsurvivors (34%) died within 24 h. In the screening group, hyperlactataemia on admission identified mortality with likelihood ratio = 15. In the study group, neither the admission lactate (3.8 vs 4.6 mmol/l, P = 0.27), pH (7.32 vs 7.30, P = 0.6), nor BE (-7.5 vs -8, P = 0.45) differed significantly between survivors and nonsurvivors. Neither the admission nor peak lactate increased with increasing MOSF score (P = 0.5 and 0.54). The median peak lactate level was 5 mmol/l (2-9.3) in survivors compared to 6.8 mmol/l (2.3-22) in nonsurvivors (P = 0.02), and the cumulative average lactate level was 2.4 mmol/l (1-4.9) in survivors, compared to 4.5 mmol/l (1.6-21) in nonsurvivors (P = 0.0003). Persistent hyperlactataemia 24 h after admission identified mortality with likelihood ratio = 7. CONCLUSION: Hyperlactataemia on admission to intensive care is associated with a high mortality in children. Nonsurvivors within this group may be distinguished by the peak lactate level, or by persistent hyperlactataemia after 24 h of treatment.

Acidosis, Lactic↗
PubMed2000

Evaluation of the 5-French saline paediatric gastric tonometer.

OBJECTIVE: To evaluate the paediatric 5-French (Fr) saline-filled gastric tonometer. DESIGN: (a) In vitro comparison of saline bath reference pCO2 with tonometric pCO2 measured by normal saline-filled and phosphate-buffered saline-filled 5-Fr tonometers, and by a recirculating gas tonometer. ( b) In vivo comparison of gastric intramucosal pCO2i, measured by normal saline-filled 5-Fr tonometer (NST) and simultaneously by recirculating gas tonometer (RGT) in ten paediatric intensive care patients. (c) In vivo comparison of pCO2i measured simultaneously by 2 NST 5-Fr tonometers, before and after enteral feeding, in ten paediatric intensive care patients. MEASUREMENTS AND MAIN RESULTS: (a) Twenty consecutive measurements of pCO2 were made at constant reference pCO2 of 19, 38, 56, and 75 mmHg (2.5, 5.0, 7.5, and 10.0 kPa), respectively. The NST tonometer underestimated reference pCO2 by mean bias (limits of agreement) of 58% (20%), and the phosphate-buffered saline-filled tonometer by 6% (26%). The RGT showed mean bias 5.7% with narrow limits of agreement (1.5%). (b) In 50 paired (NST vs. RGT) in vivo measurements over pCO2i range 23-73 mmHg (3.0-9.7 kPa), the NST underestimated RGT pCO2i by a mean bias of 10 mmHg (1.3 kPa), with limits of agreement +/-10 mmHg (1.5 kPa). This resulted in NST consistently overestimating pHi and underestimating pCO2 gap (both P < 0.001). (c) One hundred simultaneous paired NST measurements were assessed (50 without, and 50 with enteral feeding). The mean biases (limits of agreement) were identical in the fasted and fed states 0.4+/-6 mmHg, with no difference between the fed and fasting states (P = 0.7). CONCLUSIONS: There are inherent problems in the methodology of saline tonometry, which adversely affect the accuracy and reliability of the 5-Fr paediatric gastric tonometer in comparison to recirculating gas tonometry.

Analysis of Variance↗
PubMed2000

Cardiac output measured by lithium dilution and transpulmonary thermodilution in patients in a paediatric intensive care unit.

OBJECTIVE: To compare the results of cardiac output measurements obtained by lithium dilution and transpulmonary thermodilution in paediatric patients. DESIGN: A prospective study. SETTING: Paediatric intensive care unit in a university teaching hospital. PATIENTS: Twenty patients (age 5 days-9 years; weight 2.6-28.2 kg) were studied. INTERVENTIONS: Between two and four comparisons of lithium dilution cardiac output (LiDCO) and transpulmonary thermodilution (TPCO) were made in each patient. MEASUREMENTS AND RESULTS: Results from three patients were excluded: in one patient there was an unsuspected right-to-left shunt, in two patients there was a problem with blood sampling through the lithium sensor. There were 48 comparisons of LiDCO and TPCO in the remaining 17 patients over a range of 0.4-6 l/min. The mean of the differences (LiDCO-TPCO) was -0.1 +/- 0.3 (SD) l/min. Linear regression analysis gave LiDCO = 0.11 + 0.90 x TPCO l/min (r2 = 0.96). There were no adverse effects in any patient. CONCLUSIONS: These results suggest that the LiDCO method can be used to provide safe and accurate measurement of cardiac output in paediatric patients. The method is simple and quick to perform, requiring only arterial and venous catheters, which will already have been inserted for other reasons in these patients.

Age Factors↗
PubMed2000

Procalcitonin may help differentiate disseminated herpes simplex viral infection from bacterial sepsis in neonates.

UNLABELLED: Disseminated herpes simplex virus infection is a potentially fatal condition which may be difficult to differentiate from bacterial sepsis. We report the case of a neonate with overwhelming herpes simplex (type 2) viraemia who presented with 'septic shock'. CONCLUSION: A low procalcitonin level (1.6 ng/ml), inconsistent with bacteraemia, suggests an alternative aetiology and may strengthen the case for antiviral therapy.

Biomarkers↗