A quality-improvement project to enhance systemic arterial contrast opacification in CT for trans-catheter aortic valve implantation

AIM

To assess improvement in arterial opacification by optimising the contrast medium dosing protocol for computed tomography (CT) prior to trans-catheter aortic valve implantation (TAVI).

MATERIALS AND METHODS

A wide variation in arterial opacification was observed in the initial CT TAVI protocol (standard protocol). The practice was optimised by considering the time required for the examination and optimising contrast medium flux. This became the optimised protocol with a 30-second contrast medium bolus of iodine flux 15-19 mg iodine/kg body weight/second (mg/kg/s). Attenuation (mean HU) in (a) the ascending aorta (gated systolic acquisition) and (b) the ascending, descending thoracic (at carina), infra-renal abdominal aorta, and right common iliac artery (non-gated acquisition) was measured. Thirty-one sequential optimised examinations were compared to 31 prior standard protocol examinations.

RESULTS

There was no difference between the standard and optimised groups regarding age, sex, weight, body mass index (BMI), or voltage. The mean bolus durations were 24.9±4.4 seconds for the standard and 30±0.3 seconds for the optimised protocols (p<0.001). Although there was no difference in the attenuation in the gated ascending aorta (p>0.99), there was improvement at all other anatomical points in the non-gated examinations of the optimised protocol (p<0.002).

CONCLUSION

Optimising contrast medium flux and matching bolus duration to the CT technology dramatically improves the vascular access component of TAVI planning and provides a reliable method to achieve objectively enhanced arterial opacification. This work highlights how to obtain good arterial contrast medium opacification in haemodynamically fragile patients without excessive contrast medium volumes.

Differences in the binding of quinine and quinidine to plasma proteins

1. Little is known about the comparative plasma protein binding of the antimalarial agents quinine (QN) and its isomer quinidine (QD). We have examined the in vitro binding of QN and QD to albumin, alpha 1-acid glycoprotein, normal human plasma, and maternal and foetal umbilical cord plasma. 2. QN was more avidly bound than QD, and binding of both drugs was substantially higher to alpha 1-acid glycoprotein than to albumin, indicating that alpha 1-acid glycoprotein is the more important binding protein. 3. Protein and drug concentration dependent binding was evident for both QN and QD. The unbound fraction of both drugs fell with increasing albumin (10 to 60 g l-1) and alpha 1-acid glycoprotein (0.5 to 2.0 g l-1) concentration, and there was a marked increase in unbound fraction of QN (6 to 19%) and QD (13 to 36%) in human plasma when drug concentrations were increased over the antimalarial therapeutic range (0.5 to 10 mg l-1). 4. In human volunteer plasma, the unbound fractions of QN and QD were 7.5 +/- 2.2% and 12.3 +/- 2.3% respectively, whilst the unbound fractions for both drugs were significantly higher in maternal plasma (QN = 13.0 +/- 5.4%, QD = 18.3 +/- 2.5%) and significantly higher still in foetal umbilical cord plasma (QN = 25.7 +/- 10%, QD = 35 +/- 5.3%).

The management of severe preeclampsia with intravenous magnesium sulphate, hydralazine and central venous catheterization

A prospective study of patients with severe preeclampsia managed by magnesium sulphate infusion for eclampsia prophylaxis, hydralazine infusion for vasodilatation and central venous catheterization for fluid monitoring is reported. In this preliminary report of 46 patients, there was no episode of eclampsia following treatment, no maternal death, and hypertension was well controlled in all patients. Of the 51 babies born, there were 7 stillbirths, and 4 neonatal deaths; 6 of the 7 stillbirths were less than 30 weeks' gestation, and 23 of the 46 patients were delivered by Caesarean section.

A prospective study of dextran-induced anaphylactoid reactions in 5745 patients

A prospective study of dextran-induced anaphylactoid reactions (DIAR) in 5745 gynaecological and obstetric patients who received dextran 70 solution intravenously while undergoing major surgery revealed 8 patients who had Grade I or II reactions and 7 patients who had Grade III or IV reactions. The incidence of severe reactions was 1:821 patients treated. The overall incidence of reactions per patient treated was 1:383. One neonatal death followed a dextran-induced cardiac arrest in a woman about to undergo caesarean section. The risks of dextran 70 treatment exceeded the risks of thromboembolism in these patients.

Selecting a computer for your needs

Realistic goals and adequate information about equipment and program capabilities are essential prerequisites when selecting a computer system. Problems of equipment selection are dealt with by discussing a range of microcomputers emphasising the need to consider expansion and compatibility with standards such as the S. 100 bus. The importance of ready availability of word processing and management programs is emphasised.

Evaluating fetomaternal hemorrhage by alphafetoprotein and Kleihauer following therapeutic abortions

In a survey of 75 patients at 6-11 weeks gestation, fetomaternal hemorrhage (FMH) was detected by significant rises (greater than 2 S.D.) in maternal alphafetoprotein (AFP) levels in 57% of patients, while increased fetal cells were detected by the Kleihauer test in 24% of patients. With increasing gestation, FMH was detected more readily by both tests; however, in evaluating FMH at less than 10 weeks gestation. AFP was found to be a more sensitive and reliable marker than the Kleihauer test. We suggest that there is a gray zone for the Kleihauer test in early gestation, when erythroblasts containing embryonic hemoglobins are gradually replaced in the fetal circulation by erythrocytes containing fetal hemoglobin.

Halothane, enflurane, methoxyflurane, and isolated human uterine muscle

The depressant effects of halothane, enflurane and methoxyflurane at 0.5, 1.0 and 1.5 MAC on isolated human gravid uterine muscle have been studied. The muscle samples were obtained from women undergoing caesarean section at between 38 and 41 weeks gestation. All three agents produced depression of uterine muscle contractility and of contraction frequency. There were no significant differences between the degree of depression of the uterine muscle at equipotent concentrations of the three volatile agents. Differing concentrations of the same agent over the range 0.5 to 1.5 MAC produced no significant change in the uterine muscle depression.

Drugs in obstetric anaesthesia

From the anaesthetist's viewpoint, pharmacokinetics of pregnancy, drugs affecting uterine muscle tension and foetal effects of anaesthetic drugs are reviewed.