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Biomedical subjects

P A Dargaville

Publications and source records attributed to P A Dargaville.

At least 19 recordsLinked to original sources
PubMed2006

Hemodynamic disturbances associated with endovascular embolization in newborn infants with vein of Galen malformation.

OBJECTIVE: To examine hemodynamic changes following endovascular embolization in newborn infants with vein of Galen malformation and severe cardiac failure in the first week of life. STUDY DESIGN: Over a recent 5-year period, nine such infants were identified. In seven of these infants, changes in arterial blood pressure were analyzed in relation to the timing of embolization procedures. RESULTS: A significant increase in arterial blood pressure was noted after most embolizations. In two infants, this systemic hypertension was severe and treated using intravenous antihypertensive drugs. Both infants subsequently developed complete infarction of both cerebral hemispheres with sparing of the brainstem and cerebellum. Mortality in the nine infants was 33%, and 83% of the survivors were neurologically normal or near normal at follow-up. CONCLUSION: The systemic hypertension observed following endovascular embolizations may provide a protective mechanism to maintain cerebral blood flow after reperfusion injury. Lowering blood pressure in this situation may therefore be detrimental.

Arteriovenous Fistula↗
PubMed2006

Death in the neonatal intensive care unit: changing patterns of end of life care over two decades.

BACKGROUND: Death remains a common event in the neonatal intensive care unit, and often involves limitation or withdrawal of life sustaining treatment. OBJECTIVE: To document changes in the causes of death and its management over the last two decades. METHODS: An audit of infants dying in the neonatal intensive care unit was performed during two epochs (1985-1987 and 1999-2001). The principal diagnoses of infants who died were recorded, as well as their apparent prognoses, and any decisions to limit or withdraw medical treatment. RESULTS: In epoch 1, 132 infants died out of 1362 admissions (9.7%), and in epoch 2 there were 111 deaths out of 1776 admissions (6.2%; p<0.001). Approximately three quarters of infants died after withdrawal of life sustaining treatment in both epochs. There was a significant reduction in the proportion of deaths from chromosomal abnormalities, and from neural tube defects in epoch 2. CONCLUSIONS: There have been substantial changes in the illnesses leading to death in the neonatal intensive care unit. These may reflect the combined effects of prenatal diagnosis and changing community and medical attitudes.

Cause of Death↗
PubMed2005

Volume guarantee ventilation, interrupted expiration, and expiratory braking.

BACKGROUND: In volume guarantee ventilation with the Dräger Babylog 8000 ventilator, inspiratory and expiratory flows are monitored and the expiratory tidal volume calculated following each inflation. The pressure for the next inflation is modified to ensure the expired tidal volume is close to the set value. AIM: To investigate interrupted expiration observed during volume guarantee ventilation of spontaneously breathing, ventilated infants. METHODS: Spontaneously breathing infants, ventilated with volume guarantee, had recordings of gas flow, ventilator pressures, tidal volume waveforms, oximetry, heart rate, and transcutaneous oxygen and carbon dioxide during 10 minute recordings. RESULTS: A total of 6540 inflations were analysed from 10 infants; 62% were triggered. Two different patterns were found: (1) Normal volume guarantee pattern with 97% of triggered and 91% untriggered inflations. It had a normal expiratory curve and a mean expired tidal volume within 3% of the set volume, but a large variation due to the babies' breathing. (2) A pattern of interrupted expiratory flow after approximately 3% of inflations due to a small inspiration (approximately 1.3 ml/kg) during expiration. This led the ventilator to calculate an inappropriate total expired tidal volume for that inflation and an increase in the pressure for the next inflation. CONCLUSIONS: After about 3% of inflations, with volume guarantee ventilation, interruption of the expiration causes an increased pressure for the next inflation of approximately 4.9 cm H2O, compared with normal volume guarantee inflation. The interrupted expiration is most likely to be due to diaphragmatic braking.

Diaphragm↗
PubMed2005

Neonatal resuscitation 2: an evaluation of manual ventilation devices and face masks.

BACKGROUND: The key to successful neonatal resuscitation is effective ventilation. Little evidence exists to guide clinicians in their choice of manual ventilation device or face mask. The expiratory tidal volume measured at the mask (V(TE(mask))) is a good estimate of the tidal volume delivered during simulated neonatal resuscitation. AIM: To compare the efficacy of (a) the Laerdal infant resuscitator and the Neopuff infant resuscitator, used with (b) round and anatomically shaped masks in a model of neonatal resuscitation. METHODS: Thirty four participants gave positive pressure ventilation to a mannequin at specified pressures with each of the four device-mask combinations. Flow, inspiratory tidal volume at the face mask (V(TI(mask))), V(TE(mask)), and airway pressure were recorded. Leakage from the mask was calculated from V(TI(mask)) and V(TE(mask)). RESULTS: A total of 10,780 inflations were recorded and analysed. Peak inspiratory pressure targets were achieved equally with the Laerdal and Neopuff resuscitators. Positive end expiratory pressure was delivered with the Neopuff but not the Laerdal device. Despite similar peak pressures, V(TE(mask)) varied widely. Mask leakage was large for each combination of device and mask. There were no differences between the masks. CONCLUSION: During face mask ventilation of a neonatal resuscitation mannequin, there are large leaks around the face mask. Airway pressure is a poor proxy for volume delivered during positive pressure ventilation through a mask.

Air Pressure↗
PubMed2005

Neonatal resuscitation 3: manometer use in a model of face mask ventilation.

BACKGROUND: Adequate ventilation is the key to successful neonatal resuscitation. Positive pressure ventilation (PPV) is initiated with manual ventilation devices via face masks. These devices may be used with a manometer to measure airway pressures delivered. The expiratory tidal volume measured at the mask (V(TE(mask))) is a good estimate of the tidal volume delivered during simulated neonatal resuscitation. AIM: To assess the effect of viewing a manometer on the peak inspiratory pressures used, the volume delivered, and leakage from the face mask during PPV with two manual ventilation devices in a model of neonatal resuscitation. METHODS: Participants gave PPV to a modified resuscitation mannequin using a Laerdal infant resuscitator and a Neopuff infant resuscitator at specified pressures ensuring adequate chest wall excursion. Each participant gave PPV to the mannequin with each device twice, viewing the manometer on one occasion and unable to see the manometer on the other. Data from participants were averaged for each device used with the manometer and without the manometer separately. RESULTS: A total of 7767 inflations delivered by the 18 participants were recorded and analysed. Peak inspiratory pressures delivered were lower with the Laerdal device. There were no differences in leakage from the face mask or volumes delivered. Whether or not the manometer was visible made no difference to any measured variable. CONCLUSIONS: Viewing a manometer during PPV in this model of neonatal resuscitation does not affect the airway pressure or tidal volumes delivered or the degree of leakage from the face mask.

Air Pressure↗
PubMed2002

Clinical course and medical management of neonates with severe cardiac failure related to vein of Galen malformation.

BACKGROUND: Neonatal presentation of vein of Galen aneurysmal malformations (VGAMs) with intractable cardiac failure is considered a poor prognostic sign. Interventional neuroradiology with embolisation has been shown to control cardiac failure, but there is a perception that neurological outcome in survivors is poor. OBJECTIVE: To determine if aggressive intensive care and anaesthetic management of cardiac failure before urgent embolisation can influence morbidity and mortality. PATIENTS: Nine newborns (four boys, five girls) were diagnosed with symptomatic vein of Galen malformations in the neonatal period during the period 1996-2001. Eight developed intractable high output cardiac failure requiring initial endovascular treatment in the first week of life. RESULTS: The immediate outcome after a series of endovascular procedures was control of cardiac failure and normal neurological function in six (66%) patients, one death from intractable cardiac failure in the neonatal period, and two late deaths with severe hypoxic-ischaemic neurological injury (33% mortality). Clinical review at 6 months to 4 years of age showed five infants with no evidence of neurological abnormality or cardiac failure and one child with mild developmental delay (11%). CONCLUSIONS: Aggressive medical treatment of cardiac failure and early neurointervention combined with modern neuroanaesthetic care results in good survival rates with low morbidity even in cases of high risk VGAM presenting in the immediate perinatal period with cardiac failure. Systemic arterial vasodilators improve outcome in neonates with cardiac failure secondary to VGAM. Excessive beta adrenergic stimulation induced by conventional inotropic agents may exacerbate systemic hypoperfusion.

Cardiac Output, Low↗
PubMed2001

Left-lung-collapse bronchial deformation in giant omphalocele.

Five infants with giant omphalocele had persistent collapse of the left lung and required prolonged respiratory support. Narrowing of the left main bronchus, reversible with positive end-expiratory pressure, was identified radiographically in 3 infants, and we postulate that this relates to distortion of the bronchus within the constraints of the elongated, narrow thoracic cavity characteristic of these patients. The lung collapse may be precipitated by manipulation (reduction or attempted reduction) of the omphalocele. J Pediatr Surg 36:846-850.

Abnormalities, Multiple↗
PubMed2001

Upper cervical spinal cord injury in neonates: the use of magnetic resonance imaging.

Neonatal upper cervical spinal cord injury is associated with rotational forceps delivery and presents with quadriparesis and diaphragmatic paralysis. The underlying pathology determines neurologic outcome but is difficult to assess clinically or with simple radiographic techniques. We report 4 cases in which early magnetic resonance imaging demonstrated the extent and severity of the injury and guided management.

Cervical Vertebrae↗
PubMed2001

Surfactant and surfactant inhibitors in meconium aspiration syndrome.

Surfactant indices and inhibitors were measured in lung lavage fluid from 8 infants with meconium aspiration syndrome (MAS) who were receiving mechanical ventilation and 11 healthy control subjects. Surfactant phospholipid and surfactant protein A content in MAS was not different from that of control subjects, but concentrations of total protein, albumin, and membrane-derived phospholipid were elevated. All infants with MAS had hemorrhagic pulmonary edema. These findings reinforce the notion of MAS as a toxic pneumonitis with epithelial disruption and proteinaceous exudation.

Albumins↗
PubMed2000

Overcoming surfactant inhibition with polymers.

Inhibition of the function of pulmonary surfactant in the alveolar space is an important element of the pathophysiology of many lung diseases, including meconium aspiration syndrome, pneumonia and acute respiratory distress syndrome. The known mechanisms by which surfactant dysfunction occurs are (a) competitive inhibition of phospholipid entry into the surface monolayer (e.g. by plasma proteins), and (b) infiltration and destabilization of the surface film by extraneous lipids (e.g. meconium-derived free fatty acids). Recent data suggest that addition of non-ionic polymers such as dextran and polyethylene glycol to surfactant mixtures may significantly improve resistance to inhibition. Polymers have been found to neutralize the effects of several different inhibitors, and can produce near-complete restoration of surfactant function. The anti-inhibitory properties of polymers, and their possible role as an adjunct to surfactant therapy, deserve further exploration.

Humans↗
PubMed1999

Functional and compositional changes in pulmonary surfactant in response to exercise.

Pulmonary surfactant from bronchoalveolar lavages was obtained from 2 groups of horses. A control group consisting of 6 healthy racehorses that were paddock-rested and lavaged weekly for 6 consecutive weeks were compared with an experimental group of 10 healthy racehorses, lavaged weekly the same period, consisting of a 5 week incremental-intensity treadmill training programme and one week post training paddock rest. Phospholipid content of lavage fluid was determined indirectly by phosphorus assay, and surfactant functional activity was determined by bubble surfactometry. Total cell counts and differential cell percentages of lavage fluid were adjusted to reflect the dilution of alveolar epithelial lining fluid (ELF) using the lavage/serum urea ratio, and data were analysed per volume of ELF. There was no change in phospholipid content for either group, but some horses had consistently greater amounts than did others, ranging from 17.2-64.4 micrograms/microliter. From the exercised group ELF had both increased nucleated cell numbers due to increased macrophage numbers, and increased numbers of erythrocytes. Surface tension increased significantly over the exercise protocol, but not in controls. Functional activity of surfactant varied between horses, independent of phospholipid content, with average values for individuals ranging 10.5-29.5 mN/m. We conclude that exercise of sufficient intensity to induce intrapulmonary haemorrhage also leads to functional decrease in surfactant activity, without affecting phospholipid content. This study also indicates that functional differences in surfactant exist between horses and may be a risk factor for development of exercise-induced pulmonary haemorrhage.

Animals↗
PubMed1999

Comparison of two methods of diagnostic lung lavage in ventilated infants with lung disease.

The methods of nonbronchoscopic lung lavage used for collection of samples of epithelial lining fluid (ELF) in intubated patients are poorly standardized and incompletely validated. In infants with lung disease requiring ventilatory support, we evaluated two techniques of small volume saline lavage for the collection of a specimen suitable for pulmonary surfactant analysis. We aimed to compare apparent origin of the return fluid obtained by each method, equivalence and agreement of the estimates of measured pulmonary surfactant concentration, and the relative strength of association between surfactant indices and lung dysfunction. Fifty-three contemporaneous paired samples of lung lavage fluid suitable for surfactant analysis were collected from 31 infants using tracheal aspirate (TA, 4 x 0.5 ml saline), and then nonbronchoscopic bronchoalveolar lavage (NB-BAL, 3 x 1 ml/kg). Return fluid from TA had higher mean ELF concentration of total protein and IgA secretory component (SC), and a lower surfactant protein A (SP-A) concentration than NB-BAL, indicating that the TA lavage was sampling ELF more proximally in the tracheobronchial tree (protein: TA 7.7 versus NB-BAL 4.7 mg/ml; SC: 21 versus 1.8 microgram/ml; SP-A: 9.8 versus 19 microgram/ml; all p < 0.01). Mean concentration of surfactant indices in ELF differed only for SP-A, but for all indices, paired values showed poor agreement on Bland-Altman analysis, highlighting the potential imprecision associated with small volume lung lavage. TA return fluid yielded estimates of surfactant indices which were at least equivalent to NB-BAL in prediction of the severity of lung dysfunction. We conclude that NB-BAL return fluid has more distal origin, but analysis of TA fluid may have equal validity in the estimation of indices of pulmonary surfactant. The results of individual estimates of ELF constituents in a single sample of lavage fluid should be interpreted with caution, even when standardized sampling techniques are employed.

Bronchoalveolar Lavage↗
PubMed1999

Validity of markers of dilution in small volume lung lavage.

Definitive analysis of solute concentrations in lung lavage fluid involves the use of a marker of dilution to correct for variable recovery of epithelial lining fluid (ELF), but the question of the most appropriate dilutional marker remains unresolved. In lavage fluid collected from infants with lung disease and healthy control subjects, we examined ELF concentration of protein, albumin, sphingomyelin (SM), and IgA secretory component (SC), and critically appraised the relative validity of SC and urea as dilutional markers in the context of lung infection and lung injury. Protein, albumin, and SM were found not to be valid dilutional markers, as their ELF concentration varied significantly between the diseased, recovering, and normal lung. Differences in concentration were noted in both tracheal aspirate samples (TA, 4 x 0.5 ml) and nonbronchoscopic bronchoalveolar lavage fluid (NB-BAL, 3 x 1 ml/kg), but were not uniform (e.g., TA-disease versus control: albumin 2.8 versus 0.68 mg/ml, SM 45 versus 16 microgram/ml, both p < 0.05; NB-BAL-disease versus recovery: protein 8.1 versus 4.8 mg/ml, albumin 2.9 versus 1. 4 mg/ml, both p < 0.05). Overall, SC concentrations in ELF were not different between the diseased and normal lung, but in the NB-BAL samples, significantly higher SC concentration was noted in viral bronchiolitis and pneumonia than in noninfective lung diseases. No clear evidence of additional influx of urea into lavage fluid in association with epithelial disruption was found in the diseased lung. Comparative analysis of SC and urea revealed no difference in TA samples, but in NB-BAL specimens, urea best standardized the lavage concentration of surfactant indices to correspond to the degree of lung dysfunction as indicated by oxygenation index. We conclude that SC and urea, but not protein, albumin, or SM, are valid dilutional markers with which to estimate ELF recovery during small volume lung lavage. Urea appears a more appropriate choice in return fluid derived from the distal tracheobronchial tree, and SC should not be used in the context of lung infection.

Albumins↗
PubMed1998

Overdose of ergometrine in the newborn infant: acute symptomatology and long-term outcome.

OBJECTIVE: To document the short- and long-term effects of accidental administration of ergometrine in adult dosage to the newborn infant. METHODS: The case records of all infants admitted to the Royal Children's Hospital (RCH) since 1970 with a diagnosis of acute ergometrine overdose were reviewed, and details of the acute symptomatology, management, and the neurodevelopmental outcome at follow-up were noted. Similar information was obtained, where available, from previous case reports, and from two major drug information services. Additionally, data relating to administration of uterotonic agents and vitamin K were collected from tertiary perinatal centres around Australia. RESULTS: Seven cases of neonatal ergometrine overdose were identified at RCH. The major features of the acute toxicity syndrome were: encephalopathy (100% RCH cases, 79% combined cases); seizures (100%, 70%); peripheral vascular disturbances (100%, 83%); and oliguria (43%, 34%). Other important symptoms were hypoxaemia, hypertension and feed intolerance. 86% of RCH cases (72% overall) required ventilatory support. Virtually all symptoms resolved within 4 days, and 86% of RCH infants (86% all cases) were neurologically intact at the time of discharge. Long-term neurodevelopmental outcome was normal in 100% of RCH infants (n=6). All the perinatal centres surveyed give vitamin K in the labour ward soon after delivery, and 7 of 18 (39%) reported using Syntometrine (ergometrine 0.5 mg, Syntocinon 5 IU) routinely during the third stage of labour. Thus the circumstances in which ergometrine overdose can occur still exist in many labour wards around the country. CONCLUSIONS: Despite the catastrophic initial presentation, the long-term prognosis after neonatal ergometrine overdose appears to be favourable. To prevent further cases of this life-threatening drug error, we recommend that administration of vitamin K be deferred until just prior to, or shortly after, transfer of the newborn infant to the postnatal ward.

Drug Overdose↗
PubMed1997

Pulmonary surfactant concentration during transition from high frequency oscillation to conventional mechanical ventilation.

OBJECTIVE: To test the hypothesis that conventional mechanical ventilation (CV) provides a greater stimulus to secretion of pulmonary surfactant than high frequency oscillatory ventilation (HFO). METHODOLOGY: Sequential examination of surfactant indices in lung lavage fluid in a group of six infants with severe lung disease (group 1), ventilated with HFO and then converted back to CV as their lung disease recovered. A similar group of 10 infants (group 2) ventilated conventionally throughout the course of their illness were studied for comparison. In groups 1 and 2, two sequential tracheal aspirate samples were taken, the first once lung disease was noted to be improving, and the second 48-72 h later. Group 1 infants had converted from HFO to CV during this time. RESULTS: A marked increase in concentration of total surfactant phospholipid (PL) and disaturated phosphatidylcholine (DSPC) was seen in group 1 after transition from HFO to CV; the magnitude of this increase was significantly greater than that sequentially observed in group II (total PL: 9.4-fold increase in group 1 vs 1.8-fold in group 2, P = 0.006; DSPC: group 1 6.4-fold increase vs. group 2 1.7-fold, P = 0.02). CONCLUSION: These findings suggest that intermittent lung inflation during CV produces more secretion of surfactant phospholipid than continuous alveolar distension on HFO, and raise the possibility that conservation and additional maturation of surfactant elements may occur when the injured lung is ventilated with HFO.

Bronchoalveolar Lavage Fluid↗