The continuous, noninvasive estimation of arterial carbon dioxide tension (PaCO2) by heated skin surface electrodes has recently become available for pediatric patients. Skin surface (PsCO2) electrodes can enhance the safety of procedures such as intubation, bronchoscopy, ventilator changes, sleep studies, or measurement of the ventilatory response to CO2 or hypoxia. However, clinical situations that include rapid changes in PaCO2 demand knowledge of the in vivo response time. We compared the response of a heated PsCO2 electrode to end tidal CO2 (PetCO2) during abrupt changes in inspired CO2 from room air to 7% CO2 and back to room air. We obtained 54 curves on nine healthy subjects. There was an initial lag time with less than a 10% change in PsCO2. Then PsCO2 approached PetCO2 exponentially. For subjects at rest changing from breathing room air to 7% CO2, the initial lag time was 40 +/- 2 seconds and the 50% response time of the exponential portion was 46 +/- 3 seconds. Thus, it took 86 seconds for the electrode to record a 60% response to an abrupt increase in inspired CO2. The initial lag and 50% response time were considerably shorter during exercise (30 +/- 2 and 33 +/- 2 seconds) and even shorter when switched from breathing 7% CO2 to room air (23 +/- 2 and 21 +/- 2 seconds). Exercise did not further reduce the response time when CO2 was initially elevated, suggesting the faster response time was due to vasodilation of the skin due to elevated CO2.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMedDate not supplied

Immunoreactive trypsin on dried-blood spots as a possible neonatal test for cystic fibrosis. (I. Evaluation of the method and preliminary field trial).

A method for blood spot immunoreactive trypsin (IRT) determination suitable for neonatal mass screening, and the preliminary steps towards its large-scale application are described. The method showed a highly significant correlation between blood spot and plasma values, and a study of plasma reference values in a population of 1,050 newborn infants demonstrated a log-normal distribution with a mean IRT concentration of 238.3 ng/ml. The results and their implications for neonatal mass screening are discussed.

Clinical Trials as Topic↗

PubMedDate not supplied

Neonatal screening in Italy for congenital hypothyroidism and metabolic disorders: hyperphenylalaninemia, maple syrup urine disease and homocystinuria.

A multiple screening program to establish the frequency of congenital hypothyroidism (CH), phenylketonuria (PKU), maple syrup urine disease (MSUD), homocystinuria and hypertyrosinemia in endemic and sporadic goitrous regions of Italy is being carried out. Valine, methionine, leucine, isoleucine, tyrosine and phenylalanine, eluted from a single spot and separated by column chromatography, are measured, using whole blood adsorbed on filter paper. CH is detected by RIA assay of TSH eluted from dried blood spot. A cut-off of 100 microU/ml for TSH is used providing a recall rate of 0.38%. Out of 116,000 newborn infants screened for aminoacidopathies (since 1974), 16 PKU patients, 3 affected by MSUD, 2 homocystinuric babies have been detected. Out of 25,400 newborn infants screened for CH, 5 patients were affected by permanent CH and 29 by transient hyperthyrotropinemia. Thus PKU shows a frequency of 1:7,200 newborn infants, and permanent congenital hypothyroidism 1:5,080. The coordination of screening programs for congenital metabolic diseases in a single central unit allows:--the unification of the input of samples and output of data in a single data bank;--a minimization of the physical and psychological stress to the patients and their families;--and a more satisfactory cost/benefit ratio.

Amino Acids↗

PubMedDate not supplied

Brain distribution of carbamazepine and phenobarbital given in combination in experimental epilepsy.

This study describes the brain distribution of carbamazepine (CBZ) and phenobarbital (PB) given intraperitoneally in combination to cats rendered epileptic by parenteral penicillin and by penicillin topically applied on neocortex. A control group of normal cats was also evaluated pharmacokinetically. Levels of both drugs were extremely low in brains of controls (CBZ 0.8 +/- 0.02 micrograms/g; PB 1.49 +/- 0.7 micrograms/g of fresh tissue), but higher levels were found in brains of epileptic cats with CBZ showing the greater increase (peak concentrations five- to sixfold higher than the corresponding CSF free fraction vs. three- to fourfold higher for PB). This might have been partially due to the ability of CBZ to prevent the metabolic alterations associated with severe convulsions, and hence the binding impairment. As this event had no effect of potentiation on CBZ anticonvulsant activity, the present data confirm previous reports indicating that there is no experimental evidence that two drugs are better than one in controlling epilepsy.

Animals↗

PubMedDate not supplied

Brain interstitial fluid and intracellular distribution of phenytoin.

After intravenous (i.v.) administration (10 mg/kg), the biodisposition of phenytoin (PHT) in serum (total and free concentration), cerebrospinal fluid (CSF), brain, and the interstitial fluid (IF) of the normal brain were determined in dogs. A sufficient volume of IF was obtained through a multiperforated polypropylene ball implanted into the left parietotemporal region for 4-5 weeks. PHT brain distribution coefficient values ranged between 1.9 and 3.75, while the ratios of IF to free serum PHT concentrations ranged between 0.19 and 1.04; thus, our data indicate that most of the free unbound PHT which enters the brain parenchyma accumulates in the cellular compartment. Furthermore, at 60 and 90 min the peak CSF and IF concentrations are delayed; thus, for PHT, an apparent diffusion front from the CSF into the extracellular space of the brain seems to occur.

Animals↗