Biomedical subjects

M Liu-Barnett

Publications and source records attributed to M Liu-Barnett.

5 recordsLinked to original sources

PubMed1989

Vasoactive actions of local anaesthetics on human isolated umbilical veins and arteries.

1. An in vitro study, using helical preparations of human umbilical arteries and veins obtained from healthy women at term pregnancy, was designed to determine: (a) whether three local anaesthetics commonly utilized in obstetric anaesthesia (bupivacaine, 2-chloroprocaine, and lignocaine) can induce contraction or relaxation of resting umbilical vessels; (b) whether these agents can induce contraction or relaxation of umbilical vessels which have been previously induced to contract by a known activator, potassium chloride (KCl); and (c) the relative potency of these agents as compared to KCl. 2. The results indicate that: (a) these local anaesthetics are vasoactive on human umbilical vascular smooth muscle; (b) bupivacaine induces contraction in over 90% of the resting vessels examined, while 2-chloroprocaine consistently causes relaxation and lignocaine causes a small degree of contraction in 40% of vessels examined; (c) bupivacaine causes further contraction (or potentiation) of KCl-contracted muscle in 50% of the vessels studied, while 2-chloroprocaine and lignocaine both induce relaxation of these contracted vessels.

Anesthetics, Local↗

PubMed1980

Neonatal thyroid function and anaesthesia.

Thyroid function in the neonate and its response to hexobarbitone anaesthesia were studied in newborn Wistar rats between 24 h and 42 days old. 14C-labelled mixed with unlabelled hexobarbitone was injected i.p. in anaesthetic concentrations. Serum T3, reverse T3 (rT3) and T4 and serum and whole brain hexobarbitone concentrations were measured on wakening. A decrease in serum T3 and rT3 and an increase in T4 concentrations were observed after hexobarbitone at 21 and 30 days. This appears to be a critical period in the neonatal rat. A significant negative correlation was found between the changes in serum thyroid hormone concentrations and whole-brain concentrations of hexobarbitone in 30-day-old male rats. It is suggested that similar effects may occur in the human fetus or neonate subjected to anaesthesia.

Anesthesia, General↗

PubMed1978

Serum thyroid hormones changes in patients undergoing Caesarean section under general or regional anaesthesia.

The effects of anaesthesia on serum thyroid hormones were studied in 32 pregnant young women undergoing Caesarean section at term. Eighteen patients received general anaesthesia and 14 lumbar extradural blockade. Maternal serum concentrations of thyrotrophin (TSH), thyroxine (T4), triiodothyronine (T3) and reverse triiodothyronine (rT3) were measured using radioimmunoassay at 0, delivery and 24 h. There were no significant changes in TSH in the two groups. T4 concentrations decreased significantly at 24 h in the general anaesthesia group but regional anaesthesia produced a significant decrease only at the time of delivery. T3 concentrations decreased with both techniques. Reverse T3 increased markedly with general anaesthesia only at 24 h.

Anesthesia, Epidural↗

PubMedDate not supplied

Umbilical vessels endothelium and vascular reactivity.

In vitro preparations of isolated umbilical vessels are ideal for the study of vasoactive substances. These vessels display vascular reactivity in response to numerous substances, although the mechanism of action of many of these agents is unknown. The present study was undertaken to study the role of the endothelium in the vasoactivity of these preparations, and to examine their cellular integrity. Umbilical artery and vein were studied using conventional isometric techniques, and using high power light microscopy. We found that umbilical vessel rings had no relaxant response to agents believed to release endothelium-derived relaxant factor (EDRF). Mechanical and chemical treatment to remove endothelium did not significantly alter vascular response to known contractile agonists. Cellular morphology is well maintained in ring preparations. Finally, mechanical rubbing of the intima of these rings is more reliable in endothelium removal, as compared to chemical removal with the detergent saponin.

Acetylcholine↗

PubMedDate not supplied

The response of umbilical vessels, with and without vascular endothelium, to local anesthesia in low PO2 and hypercarbia.

BACKGROUND AND OBJECTIVES: Human umbilical vessels are sensitive to local anesthetic agents as well as to a variety of other exogenous and endogenous substances. Changes in blood gases such as hypoxia and hypercarbia may alter these responses. This study examined the effects of local anesthetic agents under these conditions and how the effects are related to the vascular endothelium. METHODS: Veins and arteries, dissected from umbilical cords of healthy newborns, were cross-sectioned to form rings. The rings were mounted in a muscle chamber containing Krebs-Ringer bicarbonate solution that was gassed to approximate control, low PO2 or hypercarbic conditions. Changes in isometric tension were recorded in response to increasing concentrations of bupivacaine (B), lidocaine (L), or 2-chloroprocaine (2-CP). In half the experiments, intimal rubbing was used to remove the endothelium of rings for the purpose of disclosing the role of endothelial-derived factors. RESULTS: The normal contracting (increasing baseline tone) or relaxing (decreasing baseline tone) responses to local anesthesia were unchanged by hypercarbia, but low PO2 suppressed the relaxing effect of 2-CP on arteries. Removal of endothelium enhanced the relaxing effect of 2-CP on arteries, and unmasked a contracting effect of L on arteries. Rubbed vessels, while exposed to low PO2 or hypercarbia, became less responsive to 2-CP. CONCLUSIONS: Changes in the internal environment are capable of altering the response of umbilical vascular smooth muscle to local anesthesia. Additionally, the vascular endothelium appears to influence the degree of response to anesthesia.

Anesthetics, Local↗