Evaluation of distal radial artery cross-sectional internal diameter in neonates and infants by ultrasound and adequate selection of an intra-arterial catheter size.

BACKGROUND: Radial artery catheterization in neonates, infants, and young children is a common and useful invasive procedure that brings technical placement challenges and potential complications due to the small diameter size of the radial artery in these patients. The aim of this study is to determine appropriate catheter sizes in infants up to 6 months of age. MATERIALS AND METHODS: A total of fifty infants undergoing general anesthesia or hospitalized in the neonatal intensive care unit were included. Images of the radial artery diameter were obtained from the infant's wrist using Philips EPIQ Diagnostic Ultrasound System CVX Release 4.0. All images obtained were distal in the forearm, medial to the border of the styloid process of the radius, at the point of maximal impulse of the radial artery, and with the wrist at a 45-degree angle position. We recorded postmenstrual age, chronological age, gender, weight, location, comorbidities, medications, weight, and vital signs of each individual. RESULTS: In this single cohort study of 50 children whose ages ranged from 0 to 6 months chronological age, their radial artery diameters were averaged proportionally to their weight and age. Use of a 22G catheter would result in 100% occlusion of the diameter of the artery in most study subjects. Use of a 24G catheter would result in a range of 75%-99% occlusion depending on weight, postmenstrual age, and chronological age of the infants. CONCLUSIONS: In view of these findings, we recommend using US to measure the diameter of the radial artery and choose the most appropriate catheter size before proceeding with US-guidance for radial artery cannulation in infants. This will prevent inappropriate sizing of the catheter and the thrombotic complications this can incur.

Problems Facing the Visiting Anesthesia Team in an Underdeveloped Nation and Possible Solutions.

More than 50% of the population in most developing countries is younger than 18 years, and it has been estimated that 85% of these children may require some sort of surgery before their 15th birthday. Common congenital surgical requirements are for cleft lip and palate, inguinal hernia, meningomyelocele, as well as hydrocephalus. In addition, there is a greater incidence of trauma experienced by pediatric patients. Burn and scald injuries are also common because of the proximity of domestic open fires and boiling pots of water. Infectious conditions such as osteomyelitis and skin abscesses are more frequent in developing countries than in the developed world.Given this backdrop, the visiting anesthesiology team is faced with significant logistic issues related to a large and varied set of surgeries. This requires careful planning to ensure there will be enough personnel, equipment, and drugs available for the trip. Anesthesia teams very often have to rely on their own supplies on these excursions. Careful questioning of previous visiting groups is vital in preparation. For example, it is pointless to bring cases of sevoflurane to an operating room where the anesthesia machine only has a halothane vaporizer.

Evaluation of distal radial artery cross-sectional internal diameter in pediatric patients using ultrasound.

In this study, we measure the radial artery internal diameter (RAID) in children up to 4 years of age before and after the induction of anesthesia. A B-mode portable color Doppler ultrasound was used to measure the RAID. Three sets of measurements were taken for each child before and after the induction of anesthesia and with the wrist in the neutral and dorsiflexed positions. The reliability of the mean value of the RAID in the three sets in 24 patients was established. There were discrepancies between the RAID and the proposed catheter size in some individuals, which may not only render placement difficult but also have potential for arterial injury. There are good reasons to measure the RAID in small children prior to insertion of an intra-arterial catheter.

Malignant hyperthermia.

Malignant Hyperthermia (MH) has been a recognized complication of general anesthesia after the first case reports in the 1940's. Since then a great deal has been discovered about the genetics, pathophysiology and treatment of this once fatal syndrome. MH is the only clinical entity specifically related to and caused by anesthetic agents. MH once triggered during anesthesia results in a profound hyper metabolic state with rise in the core temperature, increased carbon dioxide production and oxygen consumption. Death will ensue if specific treatment is not started. The incidence of fulminant MH ranges from 1:62,000 to 1: 84,000 of general anesthesia cases if succinylcholine and inhalation agents are used. Massseter muscle spasm on induction of anesthesia, with an incidence of between 1:16,000 and 1:4,000, may be a predromal indication of the development of MH. Anesthetic agents, which may trigger MH in susceptible individuals, are the depolarizing muscle relaxant, succinyl choline and all the volatile anesthetic gasses. Nitrous oxide, intravenous induction agents, benzodiazepines, opioids, and the non-depolarizing relaxants do not trigger MH. MH susceptibility is associated with certain disorders, such as Duchene muscular dystrophy, and triggering agent should not be used in these patients. Inheritance is an autosomal dominant trait with variable penetrance. The pathogenesis of MH involves the loss of control of intracellular calcium ions in skeletal muscle with resultant protracted spasm and hyper metabolism. Clinically this will progress to hypercarbia, hypoxia, hyperthermia, hyperkalemia and death will result if specific treatment is not started. Management involves immediate discontinuation of the triggering anesthetics, hyperventilation with 100% oxygen and most importantly the definitive treatment with intravenous dantrolene.The importance of instigating the use of dantrolene in cases of MH cannot be overemphasized. MH is now treatable when once it would be fatal before the availability of dantrolene. Unless of an emergent nature, surgery should be canceled following the acute phase of MH. The patient should be admitted to intensive care for at least 24 hours and dantrolene continued as recurrence has been described. It is imperative that the patient and their family are counseled, Medalert bracelets provided and registration with the Malignant Hyperthermia Association of the United States (MHAUS), encouraged. The caffeine/halothane testing of muscle biopsies is currently the most definitive test for malignant hyperthermia susceptibility. The routine use in suspected cases or the immediate family of known cases remains a matter of contention.