The anatomy of the caudal (sacral extradural) space was studied in 41 children, using magnetic resonance imaging. The distance from the upper margin of the sacrococcygeal membrane to the dural sac, the length of the membrane and the maximum depth of the caudal space were each measured. Age, height, weight and body surface area were recorded and, using multiple linear regression (stepwise technique), equations predicting the length of the membrane and the distance between its upper margin and the lower limit of the dural sac were obtained. Wide variability limits the clinical usefulness of these equations. In all patients, the maximum depth of the caudal space was found to be at the upper margin of the sacrococcygeal membrane. No correlation was found between this maximum depth and the age, height, weight or body surface area of the child.

To find out whether diabetic children may inject their insulin intramuscularly rather than subcutaneously, a random sample of 32 patients aged 4-3-17*9 (median 11.3) years was studied. Distance from skin to muscle fascia was measured by ultrasonography at standard injection sites on the outer arm, anterior and lateral thigh, abdomen, buttock, and calf. Distances were greater in girls (n= 15) than in boys (n= 17). Whereas in most boys the distances were less than the length of the needle (12-5 mm) at all sites except the buttock, in most girls, the distances were greater than 12-5 mm except over the calf. Over the fascial plane just lateral to the rectus muscle the distance from skin to peritoneum was less than 12-5 mm in 14 of the 17 boys and one of the 15 girls. Twenty For many years diabetic patients were advised to inject insulin into a skinfold, inserting the needle at an angle of 45°. Since the introduction of disposable plastic insulin syringes, which have much shorter (12-5 mm) needles, the recommended injection technique was altered. Most patients were advised to insert the needle at an angle of about 90°to nearly its whole length. To obtain a painless injection they were advised to stretch the skin before injecting, although thin patients were sometimes advised to raise a skinfold. In this way it was felt that insulin would consistently be deposited into subcutaneous adipose tissue and the risk of penetrating muscle was considered to be negligible.Frid and Linden were the first to cast doubt on the latter assumption when they showed by computed tomography that the depth of subcutaneous fat over many sites in the thigh and abdomen was often less than 10 mm in lean adult patients.2 Their results were confirmed in a more recent report which showed by ultrasonography that the depth of subcutaneous fat over the deltoid muscle and the abdomen was less than 10 mm in 11 of 13 adult male volunteers.3 These results suggest that adults who use the perpendicular injection technique may sometimes deposit insulin into muscle rather than fat.Intermittent intramuscular administration of insulin could lead to variations in glycaemic control if the rate of absorption from muscle differed from that of the subcutaneous tissue. Recent studies in which modern imaging techniques were used to ensure accurate placement of insulin, have shown that insulin tends to be absorbed much faster from muscle than from subcutaneous adipose tissue.3'4To assess the risk of inadvertent intramuscular injection of insulin in children of different ages and stages of development, we measured the distance from skin to muscle fascia at recommended injection sites by high resolution real time ultrasonography.Patients and methods A random sample of 32 diabetic children was recruited from the paediatric diabetic clinic at this hospital. All the subjects were white, except one who was Afro-Caribbean. Details of the insulin injection technique, sites used, and whether parent or child gave the insulin were recorded for each child. Injection si...

SummaryOne thousand, eight hundred and fifty-seven patients underwent magnetic resonance imaging following the establishment of a structured sedation programme. Forty-eight of these patients came from the intensive care unit with a secure airway and were therefore excluded from any further analysis. Oral sedation was to be given to children aged 5 years and below. For children Ն 6 years old, oral sedation could be given only if their level of co-operation was judged to be inadequate by the referring physician. Oral sedation consisted of chloral hydrate 90 mg.kg ¹1 (maximum 2.0 g) orally with or without rectal paraldehyde 0.3 ml.kg ¹1 . All magnetic resonance imaging requests for children who failed oral sedation as well as those referred for general anaesthesia from the outset were reviewed by a consultant anaesthetist who then allocated patients to undergo the procedure with either general anaesthesia or intravenous sedation. Scans requiring intravenous sedation or general anaesthesia were performed in the presence of a consultant anaesthetist. Intravenous sedation consisted of either a propofol 0.5 mg.kg ¹1 bolus followed by an infusion (maximum 3 mg.kg ¹1 .h ¹1 ) or midazolam 0.2-0.5 mg.kg ¹1 boluses. General anaesthesia was given using spontaneous ventilation with a mixture of 66% nitrous oxide in oxygen and isoflurane following either inhalation (sevoflurane) or intravenous (propofol) induction. One thousand and thirty-nine (57.4%) of the scans were done without sedation whereas 93 scans were performed during the consultant anaesthetist supervised sessions. Oral sedation failed in 50 out of 727 patients (6.9%). Eighty-seven per cent of children aged 5 years and below needed sedation compared with 4.5% of those aged over 10 years. Two patients who had only received chloral hydrate developed significant respiratory depression. This structured sedation programme has provided a safe, effective and efficient use of limited resources.

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