Search PubMed⌕ Search

Biomedical subjects

D J Hatch

Publications and source records attributed to D J Hatch.

At least 55 records · Page 3Linked to original sources
PubMed1991

The effect of triclofos sodium sedation on respiratory rate, oxygen saturation, and heart rate in infants and young children.

Chloral hydrate is frequently used to sedate infants for lung function testing. While no effect on respiratory function has been demonstrated, a recent study has reported a fall in oxygen saturation (SaO2) following sedation in wheezy infants. This study was designed to assess the effects of the closely related but less gastrically irritant drug triclofos sodium on respiratory rate (RR), heart rate (HR), and SaO2 in infants without cardiopulmonary disease. Paired measurements using respiratory inductance plethysmography and pulse oximetry were obtained in 10 infants (4-19 months of age) during natural and sedated sleep. Following sedation with triclofos, mean RR rose by 1.9 breaths min-1 (95% confidence intervals [Cl] of the mean difference: 0.13-3.7 min-1). Mean heart rate rose by 5.5 beats min-1 (95% Cl: -0.9-11.9 min-1). Mean SaO2 fell by 0.68% (95% Cl -1.8-0.45%). None of these changes are considered to be of clinical importance, and only the change in RR reached statistical significance at the 5% level.

Procedural Sedation↗
PubMed1991

Assessment of a hygroscopic heat and moisture exchanger for paediatric use.

A laboratory study of a widely available heat and moisture exchanger marketed for paediatric use was undertaken. The deadspace, measured by volume displacement, was 12 ml, similar to that of a standard catheter mount for paediatric use. Pressure drop across the device was measured at several different flows in five samples of the device in both the dry and wet state. Calculated resistance proved to be markedly lower when compared with that of other anaesthetic equipment such as tracheal tubes, and with similar humidification devices for paediatric use.

Anesthesiology↗
PubMed1991

Respiratory compliance during sedation, anesthesia, and paralysis in infants and young children.

Although total respiratory compliance (Crs) has been shown to fall in adults on induction of halothane anesthesia, no successful paired studies have been reported in children. The multiple occlusion technique was used to measure Crs in 17 infants and young children during sedated sleep (CrsS) and shortly after, following induction of halothane anesthesia (CrsA). Crs fell in all but one infant after induction of anesthesia, with a mean fall of 34.7% (range 0-58%). This was accompanied by a reduction in tidal volume and increase in frequency in every case. In 7 of the 17 children, who were to be paralyzed for surgical purposes, Crs was also measured in this anesthetized-paralyzed state. When tidal volume administered during manual ventilation was similar to that observed during measurement of CrsA, Crs during this low-volume ventilation was similar to CrsA. When tidal volume was increased and Crs remeasured, there was a significant increase in every case, with the high-volume Crs within 10% of CrsS in all but one child, in whom there was a 31.4% increase with respect to CrsS. Changes in tidal volume accounted for approximately 50% of the variability in each state. These results demonstrate a highly significant fall in Crs in infants and young children after induction of halothane anesthesia. In addition it appears that this reduction in Crs can be reversed by paralyzing the child and manually ventilating with tidal volumes approximating those seen during sedation.

Anesthesia↗
PubMed1990

Total respiratory compliance in infants and young children with congenital heart disease.

The multiple occlusion technique was used to measure total respiratory system compliance (Crs) in 62 infants and young children with congenital heart disease (age range, 2 days to 2 years). Measurements were found to be reproducible in nine infants in whom repeat measurements were possible (maximum deviation between measurements less than 10%). The incidence of failure to obtain accurate results was no greater than when studying infants without cardiopulmonary disease. However, in the presence of severe growth retardation or alinearity of volume-pressure data, results may be difficult to interpret in individuals. Results of Crs were related to non-invasive assessments of cardiac disease severity using chest radiography and echocardiography. After the effects of growth had been taken into account, a significant negative relationship was found between Crs and the right pulmonary artery to aortic ratio, which reflects pulmonary vascular engorgement (P = 0.003, R2 = -0.40). However, no significant relationship was found between Crs and chest X-ray score (P = 0.27).

Aorta↗
PubMed1990

Measurements of ammonia emission from grazed grassland.

Some of the factors influencing NH(3) emission from grazed grassland were examined. The large day-to-day variation in rates of loss were only partially explained by variation in the measured environmental factors (wind speed, soil and air temperature, soil moisture status, relative humidity, rainfall and potential evapotranspiration). Of the measured variables, wind speed had the largest effect but the best multiple linear regression model of daily NH(3) loss had an adjusted R(2) value of only 0.406. The mechanisms controlling NH(3) flux were therefore unclear. There were marked diurnal rhythms in NH(3) loss and the concentration gradients above the sward were strongest during the period which included the 3 h each side of midday. This pattern of NH(3) release has important implications in relation to atmospheric mixing processes and chemical reactions. A comparison of two means of determining NH(3) concentrations, i.e. a bubbler collection system or denuder tubes, indicated that different forms were collected which could be related to the environmental conditions. Such differences and effects should be considered when models are developed to describe the behaviour of nitrogenous and other species in the atmosphere.

Journal Article↗
PubMed1990

Comparison of candidates who passed or failed the final (Part Three) examination for the F.F.A.R.C.S. (Eng.) in 1988.

All 484 candidates for the 1988 Fellowship in Anaesthesia (Part Three) were surveyed to investigate any differences between successful and unsuccessful candidates in study techniques, work and domestic factors, and examination history that might lead to better guidance to those preparing for the examination and an improvement in the current success rate of less than 30%. Candidates' views were sought also on the examination process. The response rate was 67%. Forty-two percent of respondents passed the examination. Forty-seven percent of successful and 55% of unsuccessful candidates considered their clinical workload was excessive. Successful candidates reported better departmental support, more systematic and adequate preparation, and a better knowledge of the scope of the examination. Unsuccessful candidates were more likely to have had a personal or family crisis or change in job which impeded their preparation for the examination. Almost 50% of all respondents were unhappy with the method of announcing results.

Achievement↗
PubMed1990

Comparison of two ventilators used with the T-piece in paediatric anaesthesia.

The Nuffield 200 ventilator was compared with a new valveless ventilator (CW 200) in 20 children undergoing general anaesthesia for paediatric surgery. The new ventilator incorporates design features which overcome the main disadvantages of the Nuffield 200 and make it an inherently safer machine. At identical ventilator settings it produced a significantly greater tidal volume with a reduction in end-tidal carbon dioxide partial pressure. This may have advantages in avoiding pulmonary barotrauma in children.

Anesthesia, General↗
PubMed1990

Complications of nasotracheal intubation in neonates, infants and children: a review of 4 years' experience in a children's hospital.

A computerized database was set up to study the incidence and outcome of complications of nasotracheal intubation in a paediatric hospital. We studied 2953 intensive care admissions over a 4-yr period. The overall complication rate was 8%. Accidental extubation and tube blockage were the most frequent events, accounting for a mean of 3.5% and 2.6% of the complications per year, respectively. Complications were more common in smaller children and there were differences between fields of intensive care. None of the complications was fatal or resulted in serious sequelae. None of the children in the study showed clinical symptoms of acquired subglottic stenosis before discharge from hospital, and none has been readmitted for this condition subsequently.

Child↗
PubMed1990

Influence of tidal volume on respiratory compliance in anesthetized infants and young children.

Recent studies have suggested a close association between total respiratory compliance (Crs) and tidal volume in anesthetized paralyzed infants who are being artificially ventilated. To investigate this further, the multiple occlusion technique was used to measure Crs in 20 anesthetized infants and young children (aged 1-25 mo) before elective surgery. Measurements were made after intubation 1) during spontaneous breathing (SB), 2) after administration of a non-depolarizing muscle relaxant with tidal volume and frequency mimicking that during SB, and 3) with the child still paralyzed but tidal volume approximately double that during SB. Compared with values obtained during SB, there was no significant change in Crs after paralysis when ventilation matched the child's own pattern (P greater than 0.2). When ventilated with the larger tidal volumes, the infants showed a highly significant increase in Crs (mean 62%, range 14-158%, P less than 0.0001). These results may have implications not only for studies performed during anesthesia but also when infants were monitored in the intensive care setting. Values of Crs obtained in ventilated infants may reflect both the mechanical behavior of the respiratory system and the pattern of ventilation at the time of measurement.

Anesthesia↗
PubMed1989

Carbon dioxide elimination in anaesthetized children.

Carbon dioxide elimination (VCO2) was measured in 186 anaesthetized, spontaneously breathing infants and children with body weights ranging from 2.8 to 26.5 kg. They all underwent minor paediatric surgical procedures. The influence on VCO2 of age, operation, premedication, caudal anaesthesia, and different volatile anaesthetic agents was investigated. The volume of exhaled gas, during three- to five-minute collection periods, was measured and the fraction of exhaled CO2 was determined by a CO2 meter. Under basal anaesthetic conditions, the average output before operation followed the equation: VCO2 (ml.min-1) = -1.25X + 13.0X2, in which X = lne (body weight, kg). Expressed on a weight basis, the youngest infants (weighing less than 5 kg) had the lowest VCO2. Higher values were measured up to a body weight of 10 kg above which a negative correlation occurred between VCO2 (ml.min-1.kg-1) and body weight. The use of premedication resulted in a more variable VCO2 during operations than when opioid premedication was not used. The combination of a general anaesthetic and caudal anaesthesia stabilized VCO2. Also, children anaesthetized with halothane had a higher VCO2 than those who were anaesthetized with enflurane or isoflurane (P less than 0.05). The variable VCO2 emphasizes the need for increased monitoring of VCO2 during routine anaesthesia and operation in infants and children.

Anesthesia↗
PubMed1989

Total respiratory compliance during anaesthesia in infants and young children.

The multiple occlusion technique was used to study the effects of paralysis on ventilatory mechanics during anaesthesia. Total respiratory compliance (Crs) was measured during spontaneous breathing and following neuromuscular block with controlled ventilation in 23 infants. There was marked variation in response to paralysis: some infants demonstrated no change in Crs between the two states; others had values of Crs which were significantly higher during paralysis with controlled ventilation than during spontaneous breathing. A possible cause of these differences may be the type of controlled ventilation given during paralysis, with tidal volume directly influencing values of Crs obtained. The results of this study suggest that values of Crs obtained during spontaneous breathing and paralysis should not be used interchangeably until further studies have been performed to assess factors influencing Crs during controlled ventilation.

Anesthesia, General↗
PubMed1988

Post-tetanic count and profound neuromuscular blockade with atracurium infusion in paediatric patients.

In 38 paediatric surgical patients given atracurium by infusion, the degree of neuromuscular blockade was monitored using the post-tetanic twitch response. This was assessed by counting the number of visible responses when single twitch stimulation was applied at 1 Hz for 30 s after a 5-s tetanic stimulation at 50 Hz. A post-tetanic count of less than 10 correlated with a single twitch height of less than 5% of control, and ensured adequate paralysis. Once the count was greater than 15, the blockade could be antagonized readily.

Adolescent↗
PubMed1988

The Haloscale "Infanta" Wright respirometer. An in vitro and in vivo assessment.

The performance of the Haloscale "Infanta" respirometer has been assessed in vitro using ISO test compliances and resistances, and in vivo by comparison with pneumotachograph volumes in 13 spontaneously breathing children and 13 children during intermittent positive pressure ventilation. The Infanta was shown to be capable of registering volumes between 15 and 200 ml with an accuracy of +/- 5%. The registered volume decreased rapidly below 15 ml, whilst above 200 ml over-registration developed.

Equipment Design↗
PubMed1987

Flow requirements and rebreathing during mechanically controlled ventilation in a T-piece (Mapleson E) system.

The influence of fresh gas flow (FGF) setting on rebreathing was investigated in 15 infants and children (weight 3.5-21.8 kg) during balanced anaesthesia with mechanically controlled ventilation using a T-piece (Mapleson E) system and a Nuffield ventilator 200. Tidal volume (VT), minute volume (VE), maximal inspired (PICO2) and end-tidal (PE'CO2) carbon dioxide tensions and airway pressure were measured. VE, set to produce a PE'CO2 of about 4.5 kPa and measured at a high FGF (minimal rebreathing), was unchanged throughout the study and the regression equation for VE and weight was: VE (ml min-1) = 146 x kg + 482, r = 0.92. Measurements were then repeated at FGF:VE ratios reduced to 1.5 and 1.0. To achieve minimal rebreathing (PICO2 less than 0.5 kPa), FGF:VE ratios greater than 1.8 (range 1.8-4.9) had to be used. At FGF:VE ratios of 1.5, some alveolar rebreathing occurred, indicated by increased inspired (P less than 0.001) and end-tidal (P less than 0.001) carbon dioxide tensions. At FGF:VE ratios equal to 1.0, alveolar rebreathing was more pronounced and hypercapnoea occurred with a PE'CO2 (mean +/- 1 SD) of 5.89 +/- 0.53 kPa. At this FGF setting, change in I:E ratio from 1:2 to 1:1 did not influence the level of alveolar rebreathing. A minimal FGF (ml min-1) setting of 1.5 x VE (that is, 1.5 (146 x kg + 482), approximated to the expression (200 x kg + 1000) is recommended for controlled ventilation to avoid hypercapnoea when using the T-piece system in children weighing less than 20 kg.

Anesthesia, Inhalation↗
PubMed1987

Pulmonary ventilation and gas exchange before and after correction of congenital cardiac malformations.

Sixteen children with congenital cardiac malformations were divided into cyanotic (n = 9) and acyanotic (n = 7) groups, and pulmonary ventilation and gas exchange were assessed before surgery, after sternotomy, just after the completion of cardiopulmonary bypass (CPB), 30 min after CPB and after closure of sternostomy before transfer to ICU. Most patients in the cyanotic group had oligaemic, while all in the acyanotic group had overperfused, lungs before surgery. Total compliance was similar in the two groups. Alveolar ventilation was higher and the physiological deadspace to tidal volume ratio (VD/VT) lower in the acyanotic group compared with the cyanotic group (P less than 0.05) before surgery. In the cyanotic group the preoperative large difference between arterial (PaCO2) and end-tidal (PE' CO2) carbon dioxide tension was smaller immediately after CPB and remained so after closure of the sternum. In the acyanotic children the small arterial to end-tidal carbon dioxide difference before CPB had increased just after and 30 min after CPB, and VD/VT was significantly increased (P less than 0.05) just after CPB. After closure of the sternum the arterial to end-tidal carbon dioxide difference and the VD/VT ratio had returned to baseline. The arterial to end-tidal carbon dioxide difference is a good indicator of ventilatory efficiency after open heart surgery.

Cardiopulmonary Bypass↗