The effect of syringe size on the performance of an infusion pump.

This study investigated the effect of using three different sized syringes on the accuracy of fluid delivery when using an infusion pump at low infusion rates (1 ml.h-1). The study also measured the influence of the syringe size on the time to occlusion alarm, and on the size of the subsequent bolus dose that might be infused after relief of the occlusion which triggered the alarm. The use of a larger size syringe was found not to affect the accuracy of infusate delivery, but delayed the time to occlusion alarm and increased the size of the postocclusion bolus dose.

Assessment of pediatric patients for general anesthesia: the child with an upper respiratory infection and the ex-premature infant.

There are two types of patients that commonly lead surgeons and anesthesiologists into discussions relating to the possible cancellation or postponement of a minor pediatric surgical procedure; the child with a recent upper respiratory infection, and the patient who was born prematurely. Current opinion of the risks of anesthesia in such patients and the factors that influence perioperative course are reviewed, and a plan of management is suggested.

Microsatellite variation in the Australian dingo.

The dingo is thought to have arrived in Australia from Asia about 5,000 years ago. It is currently in danger because of interbreeding with domestic dogs. Several morphological, behavioral, and reproductive characteristics distinguish dingoes from domestic dog. Skull morphometrics are currently used to try to classify wild canids as pure dingo, dog, or hybrid. Molecular techniques based on diagnostic DNA differences between dogs and dingoes would make a much more reliable and practical test. A small number of markers (about 10) would allow detection of animals with domestic dog in their ancestry several generations back. We have typed 16 dingoes and 16 dogs of mixed breed for 14 microsatellites. The amount of variation in the Australian dingo is much less than in domestic dogs. The size distributions of microsatellites in the two groups usually overlap. The number of alleles in the dingo is much smaller in all cases. One dinucleotide repeat locus shows a size difference of 1 bp in allele classes between dog and dingo. This locus may be diagnostic for dog or dingo ancestry. The differences in distributions of alleles at other loci can also be used to classify animals using a likelihood method.

Genetic association between sensitivity to warfarin and expression of CYP2C9*3.

Cytochrome P4502C9 (CYP2C9) is largely responsible for terminating the anticoagulant effect of racemic warfarin via hydroxylation of the pharmacologically more potent S-enantiomer to inactive metabolites. Mutations in the CYP2C9 gene result in the expression of three allelic variants, CYP2C9*1, CYP2C9*2 and CYP2C9*3. Both CYP2C9*2 and CYP2C9*3 exhibit altered catalytic properties in vitro relative to the wild-type enzyme. In the present study, a patient was genotyped who had proven unusually sensitive to warfarin therapy and could tolerate no more than 0.5 mg of the racemic drug/day. PCR-amplification of exons 3 and 7 of the CYP2C9 gene, followed by restriction digest or sequence analysis, showed that this individual was homozygous for CYP2C9*3. In addition, patient plasma warfarin enantiomer ratios and urinary 7-hydroxywarfarin enantiomer ratios were determined by chiral-phase high performance liquid chromotography in order to investigate whether either parameter might be of diagnostic value in place of a genotypic test. Control patients receiving 4-8 mg warfarin/day exhibited plasma S:R ratios of 0.50 +/- 0.25:1, whereas the patient on very low-dose warfarin exhibited an S:R ratio of 3.9:1. In contrast, the urinary 7-hydroxywarfarin S:R ratio of 4:1 showed the same stereoselectivity as that reported for control patients. Therefore, expression of CYP2C9*3 is associated with diminished clearance of S-warfarin and a dangerously exacerbated therapeutic response to normal doses of the racemic drug. Analysis of the plasma S:R warfarin ratio may serve as a useful alternative test to genotyping for this genetic defect.

Severe bronchospasm during cardiopulmonary bypass.

PURPOSE: To describe the rare problem of severe bronchospasm occurring during cardiopulmonary bypass in a six-year-old-child. CLINICAL FEATURES: Severe bronchospasm became apparent on attempting to resume controlled ventilation prior to weaning from cardiopulmonary bypass. The patient had a previous history of asthma but was asymptomatic preoperatively. Aggressive therapy with multiple bronchodilating agents was necessary before cardiopulmonary bypass could be discontinued. The bronchospasm resolved over the first 24 hr after surgery. CONCLUSION: Severe bronchospasm during cardiopulmonary bypass is rare. It should only be diagnosed after ruling out other reasons for failure to ventilate. Treatment with intravenous bronchodilators is required. The cause is unknown.

Can persistent cerebral damage be caused by hyperglycaemia?

An eight-year-old girl demonstrated severe and persistent neurological damage following an uneventful anaesthetic for a planned appendicectomy. The perioperative period was remarkable only in that the patient experienced very severe hyperglycaemia and an epileptiform convulsion. A possible mechanism for neurological damage as a result of severe hyperglycaemia is described.

General anesthesia with isoflurane for diaphragmatic hernia repair during ECMO.

Isoflurane has been administered via the oxygenator of the extracorporeal membrane oxygenation (ECMO) circuit to provide anesthesia and prevent hemodynamic instability during surgical repair of congenital diaphragmatic hernia. A comparison of a series of patients treated with isoflurane demonstrates that there is less fluctuation in heart rate and blood pressure than when surgery is performed under fentanyl analgesia alone.

A multicentre randomized study of single-unit dose package of EMLA patch vs EMLA 5% cream for venepuncture in children.

Eutectic mixture of local anaesthetics (EMLA) cream with Tegaderm was compared with pre-packaged EMLA patch with regard to analgesic effect, adhesiveness and local reactions during venepuncture in 178 children from three to ten years. One EMLA patch, or half the contents of a 5 g tube of EMLA cream plus Tegaderm was applied to the dorsum of one hand or antecubital fossa for a minimum of 60 min before venepuncture. The subject and observer assessed the degree of pain on a three-point verbal rating scale. The adhesion of the patch vs Tegaderm to the skin and local reactions were recorded. There was no difference between the two groups in pain associated with venepuncture; 95% of the EMLA patch group and 94% of the EMLA cream group reported no or slight pain. There was no difference between the two treatment groups in terms of overall local reactions. The patch was less adhesive (P < 0.001), but this had no apparent influence on its effectiveness. In conclusion, EMLA patch is equivalent to 5% EMLA cream (2.5 g) in cutaneous pain relief when used for venepuncture in children.

Outpatient transesophageal echocardiography with intravenous propofol anesthesia in children and adolescents.

Outpatient transesophageal echocardiography (TEE) was performed in 10 children and adolescents (aged 3 to 19.5 years, mean 13.5 years; weight 12 to 91 kg, mean 49 kg), including two with Down's syndrome and one with autism, for diagnostic evaluation of issues unresolved by transthoracic echo examination (TTE). Issues for TEE: evaluation for atrial septal defect (two patients); anatomy of left ventricular outflow tract obstruction (one patient); aortic valve anatomy before valvuloplasty for insufficiency (one patient); evaluation for cause of cyanosis after Fontan operation (one patient); determination of source of high-velocity intracardiac turbulence after atrioventricular septal defect repair (one patient); rule out cardiac embolic source in patient with stroke (one patient); evaluate prosthetic valve function and rule out thrombus (one patient); determination of anatomic relationship of mitral valve to a ventricular septal defect before surgery for complex cyanotic heart disease (one patient); and evaluation for aortic dissection in Marfan's syndrome (one patient). Intravenous propofol anesthesia administered without endotracheal intubation by an anesthesiologist allowed successful outpatient TEE in nine patients; midazolam-conscious sedation was used in one. Outpatient TEE resolved diagnostic issues in all patients without complication, thereby avoiding cardiac catheterization in six patients and supplementing catheterization for preoperative planning in four patients. TEE can be performed safely and effectively with propofol anesthesia in the outpatient setting in carefully selected children and adolescents to provide vital diagnostic information. However, given the invasive nature of the procedure and the use of anesthesia, outpatient pediatric TEE should be used judiciously.

Postoperative analgesia: opioid infusions in infants and children.

The purpose of this review is to emphasise the ineffectiveness of traditional analgesic therapy in paediatric patients after surgery, to examine the sensation of pain in infants and children, and to describe the use of intravenous opioids for postoperative analgesia. The management of acute postoperative pain in the paediatric surgical population has been poor. This is despite the knowledge that infants and children have sufficient neurological development at birth to sense pain, and that the same hormonal and metabolic responses to nociceptive stimuli that occur in adult also occur in the neonate. Physicians frequently order analgesics in inappropriate doses, nurses are reluctant to administer opioids, and children themselves frequently compound the problem by refusing injections. The sophisticated techniques for providing postoperative analgesia which have been used so successfully in adults can also be used in paediatric patients. Two of these, continuous intravenous opioid infusion and patient-controlled analgesia, have proved to be very successful. Children older than six months can receive either modality safely with regular monitoring by qualified nursing staff. Infants younger than six months receiving continuous opioid infusions should be monitored in high-dependency units.

The accuracy and variability of bolus injections with different sized syringes.

The accuracy of bolus injections using different sized syringes was studied. A 1 ml bolus was delivered from a 1 ml, 5 ml, 10 ml, and a 20 ml syringe (n = 205). The 1 ml syringe was the most accurate (P less than 0.001) and the bolus delivered was the least variable (P less than 0.001). Variability increased as syringe size increased. A 3 ml bolus was delivered from a 3 ml, 5 ml, 10 ml, and a 20 ml syringe (n = 164). The 5 ml syringe was the most accurate (P less than 0.05) and the 3 ml and 5 ml syringes delivered a bolus with the least variability (P less than 0.001). A 5 ml bolus was delivered from a 5 ml, 10 ml, and a 20 ml syringe (n = 123); in this case there was no significant difference in the accuracy or variability of bolus among the three syringes. We conclude that for accuracy of small volume boluses (less than 5 ml), small-sized syringes should be used.