Estimation of nasotracheal tube length in infants and children.
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Adolescent↗
Biomedical subjects
D J Hatch
Publications and source records attributed to D J Hatch.
Relationship between invasive and noninvasive measurements of gas exchange in anesthetized infants and children.
Minute ventilation (VE), tidal volume (VT), carbon dioxide elimination (VCO2), and end-tidal (PETCO2) and arterial CO2 tensions (PaCO2) were measured in 39 anesthetized infants and children with body weights ranging from 3.1 to 31 kg. Eighteen children had normal cardiopulmonary function, seven had acyanotic congenital heart disease, and 11 had cyanotic congenital heart disease. One child had left heart failure and pulmonary congestion, and two had severe parenchymal lung disease. To evaluate differences between pulmonary gas exchange calculated from PaCO2 versus PETCO2, dead space volume (VD) and alveolar ventilation (VA) based on a PaCO2 (VDa, VAa) as well as on PETCO2 (VDET, VAET) were performed, and correlations between PaCO2-PETCO2, VDa/VT-VDET/VT, and VAa-VAET were carried out. It was demonstrated that in normal children, as well as in those with acyanotic congenital heart disease, PETCO2 correlated closely with PaCO2 (r = 0.94, 0.98, respectively). In children with cyanotic congenital heart disease, however, correlation between PETCO2 and PaCO2 was relatively poor (r = 0.61). Mean values for PaCO2 were significantly higher than PETCO2 in the cyanotic children (P less than 0.01), resulting in significant underestimation of physiologic dead space (P less than 0.05) and significant overestimation of alveolar ventilation (P less than 0.01). In three patients with pulmonary disease, large differences between PaCO2 and PETCO2 were comparable with those observed in the children with cyanotic congenital heart disease.(ABSTRACT TRUNCATED AT 250 WORDS)
Anesthesia↗
Anaesthesia and intra-ocular pressure in young children. A study of three different techniques of anaesthesia.
This study compares the effects of three anaesthetic techniques on intra-ocular pressure (IOP) in infants and children: spontaneous ventilation using nitrous oxide with halothane (group 1) or isoflurane (group 2) and controlled ventilation with atracurium (group 3). The IOP remained constant in groups 1 and 2 until the administration of suxamethonium when it rose significantly; this rise was maintained during tracheal intubation. In group 3 IOP increased on administering atracurium and a further increase was seen during tracheal intubation. Diagnostic intra-ocular pressure measurements should be made during spontaneous breathing prior to tracheal intubation. The IOP was not directly affected by arterial blood pressure or by expired CO2 tension.
Anesthesia, Inhalation↗
Respiratory depression in children at different end tidal halothane concentrations.
Respiratory motor function and timing were investigated at end tidal halothane concentrations of 1.5%, 1.0% and 0.5% before and during 4% carbon dioxide stimulation in 10 spontaneously breathing children who weighed between 10.2 and 25.2 kg, during hypospadias repair under halothane anaesthesia. Their tracheas were intubated and all received a caudal block to eliminate surgical stimulation. Pneumotachography and capnography were used and in three cases movements of ribcage and abdomen were also studied by magnetometers. Respiratory drive was evaluated by occlusion tests. Ventilation was depressed at an end tidal halothane concentration of 1.5%, with smaller tidal volumes, higher respiratory rates, higher end tidal carbon dioxide tensions and a weaker respiratory drive compared with 1.0% and 0.5% halothane. Paradoxical breathing was noted at 1.5% as well as at 1.0% but not at 0.5% halothane anaesthesia; the ribcage moved inwards during inspiration. Respiratory compensation during periods of 4% carbon dioxide stimulation was inadequate at 1.5% halothane, as indicated by higher end tidal carbon dioxide tensions, less negative occlusion pressures and movements of ribcage and abdomen that were unresponsive to 4% carbon dioxide, when compared with 1.0% and 0.5% halothane. Respiratory rates were higher and duration of inspiration longer at 1.5% than at 1.0% and 0.5% halothane. Respiratory timing was unaltered by carbon dioxide stimulation. It is concluded that the ventilatory motor response to carbon dioxide is dose dependent and improves at more superficial anaesthetic levels, while respiratory timing is unresponsive to carbon dioxide stimulation irrespective of the halothane concentration used. Paradoxical breathing existed at end tidal halothane concentrations higher than 1%.
Abdomen↗
Neutrophil mobility during anaesthesia in children. A trial of ascorbate premedication.
In 20 healthy children undergoing elective surgery, mobility of neutrophils, both unstimulated and stimulated by endotoxin, was studied using a millipore filter system with microscopic determination of leading front migration. Paired samples were incubated with 10(-2) mol l-1 calcium ascorbate and ten children also received 10 mg kg-1 ascorbic acid before premedication. Stimulation of mobility was reduced after the opioid premedication (P less than 0.05) in the ascorbate group only, but not significantly during anaesthesia and surgery. A few individuals showed persisting abnormally low values. No effect of ascorbate in vivo or in vitro was demonstrated. There were no infections.
Adolescent↗
Ventilation, ventilatory carbon dioxide and hormonal response during halothane anaesthesia and surgery in children after midazolam premedication.
In 14 intubated, spontaneously breathing children with body weight (bw) ranging from 8.3 to 25.6 kg, the influence of midazolam 0.1 mg kg-1 i.m. (group M0.1, n = 7) and 0.2 mg kg-1 i.m. (group M0.2, n = 7) as premedication, on sedation, ventilation, ventilatory response to carbon dioxide and hormonal stress response was studied in connection with minor surgical procedures during halothane anaesthesia. The concentrations of catecholamines, ACTH and cortisol were measured immediately after induction, during undisturbed anaesthesia, during surgery and 15 min after the end of the surgical procedure. Sedation was better and plasma catecholamine concentrations during undisturbed anaesthesia were less in children receiving the larger dose of midazolam. During surgery and in recovery there were no differences in hormone concentrations. In recovery, the concentrations of all hormones were significantly greater compared with during undisturbed anaesthesia. During surgery, VE and respiratory rate were somewhat lower in group M0.2 while E' CO2 was similar. A dose dependent depression of the response to carbon dioxide was found. However, clinically, the ventilatory response to carbon dioxide after surgery was considered to be adequate in both groups.
Adrenocorticotropic Hormone↗
Intramuscular midazolam premedication in small children. A comparison with papaveretum and hyoscine.
Midazolam 0.2 mg/kg was compared as an intramuscular premedication in small children with papaveretum and hyoscine 0.4 and 0.008 mg/kg. Midazolam produced satisfactory sedation and anxiolysis and in the early postoperative period patients were significantly more awake (p less than 0.05).
Anesthesia Recovery Period↗
Assisted ventilation and the Servo ventilator in infants. An assessment of three systems used for CPAP/IMV.
A laboratory assessment was made of systems used for Continuous Positive Airway Pressure/Intermittent Mandatory Ventilation (CPAP/IMV) with the Servo 900B and 900C ventilators. Pressure-volume loops recorded during sine wave oscillation using an external CPAP/IMV system were similar to those found during normal respiration. Pressure-volume loops using the systems based on the ventilator's inbuilt trigger mechanism were very different, particularly for the 900B. The results were confirmed by measurements in two infants. The implications of these findings with reference to the weaning of infants from mechanical ventilation are discussed.
Humans↗
Ventilation and ventilatory CO2 response in children during halothane anaesthesia after non-opioid (midazolam) and opioid (papaveretum) premedication.
The influence of non-opioid (NO) and opioid (O) premedication on ventilation and ventilatory CO2 response was studied in 18 spontaneously breathing children during halothane anaesthesia. Eight patients in Group NO and 10 in Group O were comparable in age, body weight and type of surgery performed. The sedative effect was evaluated and measurements by pneumotachography and in-line capnography were made immediately after induction of sleep, just before the start of surgery, during surgery and after surgery both before and after 3 min of about 2% CO2 inhalation. Immediately after induction the mean value (+/- s.e. mean) of end-tidal CO2 concentration (ETCO2) was 4.86 +/- 0.21% in Group NO and 5.28 +/- 0.22% in Group O. Before and during surgery, minute ventilation (VE) was higher in Group NO (P less than 0.05) mainly due to higher respiratory rates. ETCO2 was similar in the two groups before, during and after surgery. The ratio of VE to CO2 elimination (VCO2) and of dead space (VD) to tidal volume (VT) was higher in Group NO, but ventilatory response to CO2 inhalation immediately before the postoperative period was similar in both groups. It was concluded that opioid premedication resulted in more efficient ventilation during anaesthesia and surgery, and that CO2 response at the end of surgery was maintained in both groups.
Analgesics↗
Ventilatory responses to inspiratory mechanical loads in spontaneously breathing children during halothane anaesthesia.
The effect of the addition of two different resistive loads (producing 23 and 36 cmH2O (2.26 and 3.53 kPa) 1(-1) s-1, respectively, at 71 min-1) on minute volume, tidal volume, respiratory rate, duration of inspiration and inspiratory drive was studied in six intubated children during nitrous oxide, oxygen and halothane anaesthesia. With both resistive loads, tidal volume was initially reduced in all patients except one, the reduction being greater in older children. Tidal volume returned to baseline values within 3-5 min in most cases, and a transient increase was seen on removal of the load. Changes in inspiratory drive were also most marked in older children. End-tidal carbon dioxide concentration rose by 0.5% when the higher resistance was used. Respiratory rate and duration of inspiration were unchanged, suggesting the absence of a respiratory off-switch-reflex mechanism directly mediated by stretch receptors within the airways or lungs. Ventilatory compensation occurring after 3-5 min may have resulted from chemical stimulation and/or from reflexes from joint receptors and respiratory muscle spindles.
Age Factors↗
Ventilatory responses to rebreathing and carbon dioxide inhalation during anaesthesia in children.
In 12 spontaneously breathing intubated children (9.3-25 kg), ventilatory responses to rebreathing and to the inhalation of carbon dioxide (CO2) were investigated during halothane anaesthesia for minor surgical procedures. A T-piece (Mapleson F system) was used, modified by the insertion of a pneumotachograph and a paediatric airway adaptor of an in-line capnograph in the patient limb. Exhaled gas was collected for determination of expired CO2 content. Measurements were made when the fresh gas flow (FGF) was at the borderline for rebreathing (FGFr) and during 10 min with a mean FGF 44% lower, producing a maximal inspired CO2 (ICO2 max) (%) of 1.45 +/- 0.38% (mean +/- 1 SD). Measurements were repeated 5 min after returning to a flow exceeding FGFr and then during CO2 inhalation for 10 min after the addition of 1.24 +/- 0.32% CO2 (mean +/- 1 SD) to this flow. During both rebreathing and CO2 inhalation end-tidal CO2 (E'CO2) was unchanged and VE did not increase significantly (18%), but during CO2 inhalation alveolar ventilation increased (P less than 0.05), indicating an adequate and intact response to this level of CO2 inhalation. Estimations of ICO2 max could be made from the expression: ICO2 max (%) = -0.7 X FGF/VE + 2.5 and FGF to minute ventilation (VE) ratios lower than 1 were found to produce ICO2 max of 1.8% or higher. Such low FGF are likely to result in rebreathing within the alveolar ventilation and are thus of clinical importance. We believe that to increase the margin of safety in anaesthetized spontaneously breathing children, FGF of at least 1.5 to 2 times VE should be used.
Anesthesia, Inhalation↗
Ventilatory responses of children to changes in deadspace volume. Studies using the T-piece (Mapleson F) system.
Twelve patients (4.3-25.3 kg) undergoing minor surgical procedures were investigated during halothane anaesthesia with spontaneous breathing through a modified T-piece (Mapleson F) with an apparatus deadspace that could be changed from 2 ml (VDsmall) to 16 ml (VDlarge). Immediately following the switch from VDsmall to Vlarge ETCO2 (mean +/- 1 SD) increased from 6.89 +/- 1.09% to 7.61 +/- 1.14% (ns) then gradually decreased during a 10-min period. The initial plateau of FlCO2 (mean +/- 1 SD) with VDlarge was 0.74 +/- 0.34%, but gradually decreased to 0.63 +/- 0.25% after 10 min. This was achieved by an increase in VE (P less than 0.05 by 2 min). After 10 min VE had increased by more than 40% (P less than 0.01) as a result of an increase in VT (mean +/- 1 SD) of 14.6 +/- 6.5 ml. After 10 min of VDlarge ventilation, VA and VCO2 were maintained at VDsmall values. The adequate ventilatory response to the large deadspace was seen in all patients, but the ventilatory efficiency, as judged by VD/VT and VENCO2 ratios, was reduced significantly in the children weighing less than 10 kg.
Age Factors↗
Paediatric anaesthetic equipment.
Paediatric anaesthesia is made easier and safer by use of the correct equipment. The widening range and increasing complexity of available apparatus makes it essential for the anaesthetist to judge which items are most useful in any individual case. As a general rule, the simplest pieces of equipment are the most reliable and among the most useful.
Anesthesiology↗
Endocrine response to surgery in children after premedication with midazolam or papaveretum.
The effect of two premedications on the sympatho-adrenal and endocrine stress-response to minor surgery under halothane anaesthesia was investigated in 16 children. One group (n = 9) was premedicated with midazolam, 0.1 mg kg-1, and atropine 0.2-0.4 mg i.m. The other group (n = 7) received papaveretum 0.4 mg kg-1 and hyoscine 0.008 mg kg-1 i.m. Plasma concentrations of catecholamines, ACTH and cortisol were measured during undisturbed anaesthesia, during surgery and 15 min post-operatively. There were no differences in catecholamine concentrations between the groups. Prior to surgery, plasma ACTH was significantly lower (P less than 0.05) in the papaveretum group. During surgery, plasma cortisol and plasma ACTH were significantly lower after papaveretum premedication. Post-operatively there were no differences. End-tidal CO2 concentrations were similar in the two groups. It was concluded that the endocrine stress-response immediately after induction of anaesthesia and during surgery was lower after papaveretum than after midazolam premedication.
Adrenocorticotropic Hormone↗
Ventilation and gas exchange during anaesthesia and surgery in spontaneously breathing infants and children.
Minute ventilation (VE) (ml min-1), respiratory frequency (f), mixed expired carbon dioxide fraction (FECO2) and end-tidal carbon dioxide concentration (E'CO2) (%) were measured, and alveolar ventilation (VA), deadspace (VD), deadspace/tidal volume ratio (VD/VT) and carbon dioxide output (VCO2) calculated in 58 anaesthetized, spontaneously breathing infants and children weighing 2.8-20.5 kg. Although minute volumes varied, tidal volume correlated well with weight (r = 0.83), with a mean tidal volume (+/- 1SD) of 5.2 +/- 1.2 ml kg-1. It was concluded that, by the use of mean VT + 1 SD (approximated to 6 ml kg-1) the fresh gas flow in ml min-1 should be set at 2.5 X 6 X kg X f (15 X kg X f) to avoid rebreathing in various T-piece systems in anaesthetized, intubated and spontaneously breathing infants up to a body weight of 20 kg. End-tidal carbon dioxide concentration was lower in younger patients who were premedicated with atropine alone than in the older ones who received opioid premedication also. Respiratory frequency, VD/VT and total VD per minute were higher in the younger age group, which explained the finding of a high VE in relation to VCO2 for these patients. This inefficiency of ventilation emphasizes the need to minimize apparatus deadspace in breathing systems used for small infants.
Anesthesia, Inhalation↗
Comparison of ventilation and gas exchange in anaesthetized infants and children during spontaneous and artificial ventilation.
Measurements of minute and alveolar ventilation (VE and VA), respiratory frequency, end-tidal carbon dioxide concentration (E'CO2), deadspace (VD) and carbon dioxide output (VCO2) were made in 22 anaesthetized infants and young children during spontaneous (SV) and intermittent positive pressure ventilation (IPPV). In the children who had been given an opioid premedication, E'CO2 concentrations were significantly greater during SV than the predetermined value set for IPPV. In infants premedicated with atropine alone, E'CO2 during SV was only slightly greater than during IPPV, and VA was not changed. A mean tidal volume (VT) of 9.8 +/- 2.5 ml kg-1, and a mean VE of between 225 and 250 ml min-1 kg-1, were required to produce E'CO2 4.5% during IPPV. Despite a decrease in respiratory frequency, VD/VT and VD per minute were both decreased by IPPV in infants. VCO2 was unchanged in both groups. The decrease in wasted ventilation seen during IPPV in infants supports its use in clinical practice.
Anesthesia, Inhalation↗
Caudal analgesia in children. Influence on ventilatory efficiency during halothane anaesthesia.
The influence of caudal analgesia on pulmonary ventilation and gas exchange was studied in 26 children during halothane anaesthesia with spontaneous breathing. Two groups of children were studied with 13 patients in each group. One group received caudal analgesia. The other group had no caudal blocks. All children were subjected to lower abdominal and genital surgical procedures. Minute ventilation and respiratory rates were significantly lower in the caudal group than in the non-caudal group. Wastea minute ventilation and VD/VT ratios were increased in the non-caudal group. The end tidal carbon dioxide concentration was unchanged in both groups. The lower minute ventilation in the caudal group eliminated the same amount or even greater amounts of CO2 per minute indicating an improved gas distribution at slow respiratory rates. The improved ventilation efficiency and the excellent immediate postoperative pain relief achieved by caudal analgesia justifies its frequent use for these operative surgical procedures.
Anesthesia, Caudal↗