NICE guidelines for central venous catheterization in children. Is the evidence base sufficient?

BACKGROUND: Recent guidelines from the National Institute for Clinical Excellence (NICE) recommend the use of ultrasound guidance for central venous catheterization in children. This study prospectively examined the use of ultrasound guidance for central venous catheterization in children undergoing heart surgery. METHODS: One hundred and twenty-four infants and children were randomized to either ultrasound-guided or traditional landmark-guided central venous catheterization. RESULTS: Success rates were significantly greater in the landmark group compared with the ultrasound group (89.3% vs 78%, P<0.002), and arterial puncture rates were significantly lower in the landmark group (6.2% vs 11.9%, P<0.03). There was no significant difference between the two groups in the time taken to perform the catheterization. CONCLUSIONS: These results are different from the published results on which the NICE guidelines were based; however, the evidence base in children is small. There is currently insufficient evidence to support the use of ultrasound guidance for central venous catheterization in children.

Heparin pretreatment does not alter heparin requirements during cardiopulmonary bypass.

Heparin infusion may cause heparin resistance and may affect monitoring by measurement of the activated coagulation time (ACT), making the assessment of anticoagulation difficult, with the risk of over- or undertreatment, especially during cardiac surgery. We studied two groups of patients undergoing cardiopulmonary bypass (CPB): patients on heparin infusions (group H) and heparin-naive controls (group C). All patients received heparin 300 IU kg(-1) before CPB and a further dose of 5000 IU if the ACT 5 min after commencing bypass was less than 400 s. Measurements of ACT, heparin concentration, antithrombin-3, thrombin-antithrombin complex, prothrombin fragment F(1+2) and D-dimers were made before and 5 and 20 min after start of CPB. A second dose of heparin was given to eight out of 18 patients in group C and 10 out of 24 in group H. Antithrombin-3 in group H was significantly less than in group C at 5 min [59 (14) vs 52 (9)%, P<0.05]. ACT was significantly lower in group H than group C at 20 min [387 (64) vs 431 (67) s, P<0.05]. Despite ACTs of less than 400 s in both groups, no coagulation was seen, suggesting that 300 IU kg(-1) heparin is a safe dose for anticoagulation in CPB even after heparin therapy.

High risk cardiac surgery in Jehovah's Witnesses.

Much routine cardiovascular surgery can be performed without blood transfusion. Complex cardiac surgical procedures, however, especially reoperations, are often associated with heavy blood loss and large transfusion requirements. Anaesthetists and surgeons caring for patients who are Jehovah's Witnesses may be unwilling to offer such high risk surgery without recourse to blood transfusion. We report six such cases which were successfully performed without the use of blood or blood products and discuss the techniques used. Three of the patients described had been refused surgery, on their terms, at other centres. We believe that no patient should be denied potentially life saving surgery on the grounds of excessive risk without blood transfusion.

Plasma D-dimer as a marker for postoperative deep venous thrombosis. A study after total hip or knee arthroplasty.

Plasma levels of D-dimer have been found useful as a marker of deep venous thrombosis in those patients in whom thrombosis is suspected, but their usefulness in postoperative screening is less clear. We have investigated the relationship of D-dimer to deep venous thrombosis in 90 patients after total hip and knee arthroplasty. From the first postoperative day the D-dimer levels were found to be highly significantly raised in patients with deep venous thrombosis. A combined result over the first six postoperative days in excess of 1200 ng/ml correlated with thrombosis with a specificity of 100%, sensitivity of 45%, positive predictive value of 60%, and negative predictive value of 100%. However, individual estimations were not discriminatory.

Anticoagulation by ancrod for carbon dioxide removal by extracorporeal membrane lung in the dog.

Ten dogs were subjected to defibrinogenation with an intravenous perfusion of ancrod (1 unit/kg) (Arvin, Knoll AG, Ludwigshafen, Federal Republic of Germany) over a 2 1/2 hour period. Six of them were subjected to extracorporeal elimination of carbon dioxide with a polypropylene membrane lung by means of veno-venous bypass. The remaining four dogs did not undergo extracorporeal circulation and served as control subjects. In both groups, ancrod administration itself resulted in a marked drop in alpha 2-antiplasmin (33% and 67%, respectively, of the baseline values) and in slight but significant decreases in factor II and plasminogen activities of 25% and 20%, respectively (p less than 0.05), in the group subjected to carbon dioxide removal. There were no significant changes in platelet number or factor V and antithrombin III activities. During the 6-hour bypass period, platelet count and antithrombin III and factor II and V levels decreased significantly. No bleeding was observed. Histologic examination of lung biopsy tissue showed no pathologic features. Analysis of the membrane of the artificial lungs revealed no fibrin deposits. In the control group, except for a drop in alpha 2-antiplasmin levels (54%), no significant changes in hemostatic parameters occurred during the corresponding 6 hours. We conclude that, despite the drop in coagulation factors and in alpha 2-antiplasmin activity during bypass, ancrod can be considered as a valuable alternative anticoagulant for extracorporeal carbon dioxide removal.

Detection of overdosage of sedation in a patient with renal failure by the absence of lower oesophageal motility.

We report an accidental overdosage of morphine and midazolam in a patient with renal failure receiving haemofiltration detected by the absence of oesophageal motility. This situation demonstrates the difficulties of assessing the level of sedation as well as the dosage requirements in this type of patient.

Alfentanil infusions on the intensive therapy unit.

We have investigated the use of alfentanil by infusion to sedate 14 patients during controlled ventilation on the intensive therapy unit (ITU). An initial rate of 24 micrograms.kg-1.h-1 was chosen and altered thereafter according to patient response. Incremental doses of midazolam (2.5-5.0 mg) were given intravenously (i.v.) if indicated. In 4 patients, the use of a muscle relaxant was necessary to allow adequate controlled ventilation of the patient. The mean duration of infusion was 27.9 h (range 10-141 h), and the mean total dose of alfentanil was 69.3 mg (12.5-240 mg). Spontaneous ventilation was rapidly achieved in 11 patients after stopping the infusion. The mean arterial carbon dioxide tension (PaCO2) was 5.38 kPa, 15-30 min after stopping the infusion. The clinical condition of 2 patients necessitated a change in sedation technique and one patient died during the alfentanil infusion. Alfentanil by infusion caused no major cardiovascular effects and did not influence the plasma cortisol response to trauma. There was no major alteration in blood biochemistry or haematology during the infusions of alfentanil. The plasma concentrations of alfentanil during infusion showed a wide variability. These probably relate to both changes in the volume of distribution of the drug and in hepatic clearance.

Comparison between a low molecular weight and standard heparin for anticoagulation during extracorporeal CO2 removal in the dog.

Anticoagulant properties towards an artificial surface of a chemically depolymerized low molecular weight heparin (LMWH) have been compared to those of a standard heparin (SH). The experimental model consisted in a seven hours extracorporeal veno-venous bypass for CO2 removal (EC-CO2R) using a membrane lung. Four animals received 150 anti-FXa U/kg followed by 40 anti-FXa U/kg/h of LMWH or 300 IU/kg followed by 100 IU/kg/h of SH. Mean Factor Xa inhibition was 49% in LMWH group and 28.5% in SH group. Mean Factor IIa inhibition was 31% and 49% respectively. After three hours of bypass fibrin deposition occurred in the reservoir in three out of four dogs receiving LMWH while none was observed under SH. No statistically significant difference between the two groups was found for any of the coagulation parameters tested (fibrinogen, factor V, antithrombin III, plasminogen, alpha 2-antiplasmin, platelet counts). At the end of bypass 5000 U protamine abolished both anti-FXa and anti-FIIa activities in the SH group but failed to neutralize more than half of the anti-FXa activity in the LMWH group. These results suggest that high anti-FIIa activities are required to prevent fibrin formation induced by artificial surfaces and that equivalent amounts of anti-FXa activities are ineffective for this purpose. In addition the use of LMWH may raise problems when emergency neutralization procedures are required.

The prevalence of serological markers for hepatitis B virus infection amongst anaesthetists in the Oxford region.

A total of 125 anaesthetists from nine hospitals within the Oxford region were surveyed to study the prevalence of serological markers for hepatitis B virus (HBV) infection. No anaesthetists were positive for Hepatitis B Surface Antigen (HBsAg) and only four (3.2%) were positive for HBsAg antibody (anti-HBsAg). This result is in marked contrast to other studies and suggests that anaesthetists in the United Kingdom do not constitute a high risk population. The reasons for this are discussed.

Ventilatory effects of nitrous oxide during continuous infusion of fentanyl or alfentanil.

Two groups of eight patients received infusions of either fentanyl at 3 micrograms kg-1 h-1 or alfentanil at 20 micrograms kg-1 h-1 as supplements to 66% N2O in oxygen anaesthesia, during and after body surface surgery. At the end of surgery, the N2O was reduced to 50% and after measurement of ventilatory frequency, minute ventilation, and the ventilatory response to carbon dioxide, N2O was discontinued. The opioid infusions were continued for a further hour and the ventilatory measurements repeated. Both sets of measurements were compared with preoperative values. Minute ventilation (P less than 0.01), frequency (P less than 0.01) and the response to carbon dioxide (P less than 0.01) were reduced during the infusion of fentanyl with N2O; with fentanyl alone, minute ventilation (P less than 0.05) and the response to carbon dioxide (P less than 0.01) were reduced but to a lesser degree. The elimination of nitrous oxide from the inspired gas mixture produced an increase in frequency (P less than 0.05) and increases in the slope (P less than 0.01) and ventilation at 7.3 kPa (P less than 0.025) of the carbon dioxide response curve. Minute ventilation (P less than 0.01) frequency (P less than 0.05) and response to carbon dioxide (P less than 0.01) were all reduced during the infusion of alfentanil with nitrous oxide; with alfentanil alone, minute ventilation (P less than 0.01), tidal volume (P less than 0.05), the slope (P less than 0.025) and the ventilation at 7.3 kPa (P less than 0.01) of the carbon-dioxide response curve were still reduced.(ABSTRACT TRUNCATED AT 250 WORDS)

Alfentanil in short procedures. A comparison with halothane using etomidate or methohexitone for induction of anaesthesia.

Ninety patients, premedicated with temazepam 20 mg, undergoing suction termination of pregnancy, were studied. Forty patients received alfentanil (500 micrograms), and thirty halothane (1.5%) as supplements to either etomidate or methohexitone-nitrous oxide-oxygen anaesthesia. A further 20 patients received alfentanil 250 micrograms at induction of anaesthesia with methohexitone, followed by a further 250 micrograms immediately prior to the onset of surgery. Recovery was assessed by the time patients took to open eyes on command, to giving their correct date of birth, and to performing the 'p' deletion test. Satisfactory operating conditions were not obtained with the combination of etomidate and halothane. Faster recovery was seen in patients with either etomidate or methohexitone and receiving alfentanil (p less than 0.01) Testing by the 'p' deletion test showed impaired psychomotor performance at 30 minutes after cessation of anaesthesia in all groups compared with the pre-operative scores. Side effects leading to unsatisfactory anaesthesia were more frequent in patients who had received etomidate (p less than 0.01).

Effect of varying methods of upper limb occlusion on fibrinolytic activity in man.

Three techniques of intermittent venous occlusion (an oscillotonometer cuff, pneumatic leggings and an automatic arterial pressure monitoring cuff (Sentinel] were applied to one upper limb of seven healthy male volunteers. Fibrinolytic activity was assessed by the measurement of the euglobulin clot lysis time during a control period followed by 1 h of intermittent venous occlusion. Although no statistically significant differences were found with any of the methods, between the control and experimental periods, there was a trend towards fibrinolytic enhancement with intermittent pneumatic compression.

Alfentanil and recovery.

Forty patients were given alfentanil 8 micrograms/kg as a supplement to either methohexitone or Althesin anaesthesia. Satisfactory anaesthesia and recovery were seen in all patients. Testing revealed very rapid recovery of psychomotor function. There were no differences between the two groups.

Glycosylated haemoglobin concentrations in newly diagnosed diabetics before and during treatment.

Concentrations of total glycosylated haemoglobins (Hb A1) were measured in 40 diabetics at diagnosis and at monthly intervals after treatment with chlorpropamide, insulin, or diet alone was begun. The mean Hb A1 concentration at presentation in 16 patients treated with chlorpropamide was significantly higher than that in 12 patients treated with insulin, and the duration of glycaemic symptoms was much longer in the chlorpropamide-treated group. In contrast, the mean plasma glucose concentration was similar in both groups. The mean concentrations of Hb A1 and plasma glucose at diagnosis in the 12 patients treated by diet alone were lower than those in the other two groups, and most of these patients were free of symptoms. Treatment quickly relieved symptoms and lowered plasma glucose in all patients. The Hb A1 concentration fell significantly with treatment such that after two months there was no significant difference between the three groups, although results remained above the normal range. These findings support the theory that the Hb A1 concentration reflects the blood glucose control over the previous one to two months and suggest that the duration of hyperglycaemia may be important in determining the Hb A1 concentration as well as the absolute blood glucose concentration.

The morphology of cilia in sponge larvae.

Sponge larvae posses cillia with unusual terminal expansions which are curled or biconcave in shape externally, as seen by scanning electron microscopy. Thin sections, passing through the point where the ciliary shaft enters the expanded area reveal the ciliary axoneme to be surrounded by many membranous folds, some of which are vesicular. The 'club footed' cilia occur in disparate groups of Demospongiae and most frequently, all larval cilia are of this type. There is no immediately obvious correlation between the type of movement displayed by the larvae and the occurrence of terminally expanded cilia.