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Biomedical subjects

A Durward

Publications and source records attributed to A Durward.

10 recordsLinked to original sources
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

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

Resolution of mucus plugging and atelectasis after intratracheal rhDNase therapy in a mechanically ventilated child with refractory status asthmaticus.

OBJECTIVE: To report the dramatic resolution of unilateral mucus plugging and atelectasis in a mechanically ventilated child with refractory status asthmaticus after intratracheal recombinant human DNase (rhDNase) therapy. DESIGN: Case report. SETTING: Critical care unit. PATIENT: A 7-yr-old boy with status asthmaticus, severe respiratory failure and barotrauma unresponsive to conventional therapy. Fiberoptic bronchoscopy confirmed widespread mucus impaction of the subsegmental bronchi of the left lung without response to bronchoscopic lavage. INTERVENTIONS: Two 10-mg doses of intratracheal rhDNase were administered 8 hrs apart. MAIN RESULTS: The left-sided atelectasis resolved 3 hrs after the first dose of rhDNase. Improvements in gas exchange and tidal volumes were sustained and particularly noticeable after the second dose. The patient was successfully extubated 26 hrs after receiving the rhDNase treatment without any adverse effects. CONCLUSIONS: rhDNase should be considered as a potential therapy for refractory mucus plugging and atelectasis in intubated patients with status asthmaticus.

Bronchoalveolar Lavage↗
PubMed2000

Chasing the base deficit: hyperchloraemic acidosis following 0.9% saline fluid resuscitation.

Base deficit is a parameter often used to guide further treatment in acidotic children and is taken as a measure of how "sick" they are. Five children with septic shock are presented who had persisting base deficit after large volume resuscitation with 0.9% saline. Stewart's strong ion theory of acid-base balance is able to quantify the causes of metabolic acidosis and is used to show that our patients had a hyperchloraemic metabolic acidosis. We show how the chloride content of the saline loads given to our patients caused this hyperchloraemia. It is concluded that 0.9% saline and other chloride rich fluids may not be ideal resuscitation fluids; if used, clinicians must be aware of their potential to cause a persistent base deficit.

Acidosis↗
PubMed2000

Negative pressure ventilation via chest cuirass to decrease ventilator-associated complications in infants with acute respiratory failure: a case series.

Pulmonary and nonpulmonary complications of invasive positive pressure ventilation are well documented in the medical literature. Many of these complications may be minimized by the use of noninvasive ventilation. During various periods of medical history, negative pressure ventilation, a form of noninvasive ventilation, has been used successfully. We report the use of negative pressure ventilation with a chest cuirass to avoid or decrease the complications of invasive positive pressure ventilation in three critically ill infants at two institutions. In each of these cases, chest cuirass ventilation improved the patient's clinical condition and decreased the requirement for more invasive therapy. These cases illustrate the need for further clinical evaluation of the use of negative pressure ventilation utilizing a chest cuirass.

Acute Disease↗
PubMed1999

Measles inclusion-body encephalitis caused by the vaccine strain of measles virus.

We report a case of measles inclusion-body encephalitis (MIBE) occurring in an apparently healthy 21-month-old boy 8.5 months after measles-mumps-rubella vaccination. He had no prior evidence of immune deficiency and no history of measles exposure or clinical disease. During hospitalization, a primary immunodeficiency characterized by a profoundly depressed CD8 cell count and dysgammaglobulinemia was demonstrated. A brain biopsy revealed histopathologic features consistent with MIBE, and measles antigens were detected by immunohistochemical staining. Electron microscopy revealed inclusions characteristic of paramyxovirus nucleocapsids within neurons, oligodendroglia, and astrocytes. The presence of measles virus in the brain tissue was confirmed by reverse transcription polymerase chain reaction. The nucleotide sequence in the nucleoprotein and fusion gene regions was identical to that of the Moraten and Schwarz vaccine strains; the fusion gene differed from known genotype A wild-type viruses.

Encephalitis, Viral↗
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↗