Compartmental analysis of lidocaine kinetics during extracorporeal circulation

The aim of this study was to measure the effects of extracorporeal circulation (ECC) on lidocaine disposition and to determine if therapeutic concentrations were achieved during ECC. Anesthesia was obtained by administration of fentanyl (50 microg/kg plus 0.3 microg/kg/min) and pancuronium bromide (0.1 mg/kg) along with controlled ventilation (10 mL/kg, PaCO2, 30 to 34 mmHg). Lidocaine was administered to ten patients in bolus doses of 2 mg/kg at the time of endotracheal intubation and during ECC at aortic declamping. Samples were collected at 20 and 40 seconds, and at 1, 3, 5, 10, 15, 20, 25, and 30 minutes after drug administration. Blood sampling was arterial during anesthesia induction and from the oxygenator during ECC. Blood levels of lidocaine were determined by the immunofluorescence method. The kinetic studies of lidocaine showed increases in plasma volume and in the volume of the peripheral compartment, along with decreased volume in the compartment of well-perfused tissues during ECC. The fraction of the dose of lidocaine administered during ECC behaved accordingly, showing a decrease in the quantity of drug in the well-perfused tissues, and an increase in the other two compartments when compared to values before ECC. The doses administered gave plasma concentrations of 1.55 microg/mL, which are considered therapeutic. Thus, it is not recommended to increase the lidocaine dosage during ECC.

Magnesium metabolism in open-heart surgery

The levels of magnesium in serum, urine and erythrocytes were studied in 22 patients undergoing cardiac surgery for valvular prosthesis. Magnesium values were correlated with serum albumin and non-esterified fatty acids (NEFA). Data were collected before anesthesia, 10 min after sternotomy, heparinization and declamping of the aorta and in the 1st postoperative day. A slight decrease in magnesemia was observed before extracorporeal circulation (ECC) and was mainly due to haemodilution. The correlation of magnesium with NEFA was significant only after heparinization. The use of the St Thomas solution as cardioplegia fully corrected the hypomagnesemia previously reported during ECC as well as in the 1st postoperative day. A moderate hypermagnesemia was observed at the end of ECC, but no patient reached dangerous levels of serum magnesium. Urinary losses increased during and after ECC. Red blood cell magnesium showed a slight increase before ECC, followed by a significant reduction at the end of ECC.

[Behavior of GH and prolactin during enflurane anesthesia and neuroleptoanesthesia in man]

The present study was designed to investigate the effects of neuraleptanesthesia (NLA) and enflurane (Ethane) anesthesia on plasma levels of growth hormone (GH) and prolactin (PRL) in man. A total of 18 patients aged between 20 and 65 years scheduled for elective open-heart surgery were divided in two groups. In the first group (9 patients) general anaesthesia was induced with sodium thiopental (TPS) (3-5 mg/kg) and was maintained with enflurane administered with an inspired concentration of 1.5% in nitrous oxide (2 litres/min) and oxygen (2 litres/min). In the second group (9 patients) anaesthesia was induced with dihydrobenzopyridol (BPS) (0.1-0.2 mg/kg), fentanyl (5-8 gamma/kg) and TPS (3-5 mg/kg) and was maintained with fentanyl (0,65 mg in average). The patients had neither hepatic, renal or endocrine disease nor did they have a history of steroid therapy. All subjects received atropine (0.01 mg/kg) and diazepam (0.2 mg/kg) i.m. 2 hours before induction of anaesthesia. Blood samples for GH and PRL was collected before induction of anaesthesia (0) and at 30, 60, 90 and 120 minutes after induction: the 90' sample was taken immediately after sternal incision. The sampling was stopped at the start of the cardiopulmonary by-pass. A significative reduction of GH at 60' and of PRL at 30' was observed in both groups. Surgical stress at 90' does not evoke a significant increase of PRL and GH levels in both groups. In conclusion NLA and enflurane induced a decrease of GH and PRL plasma levels; in both groups the anaesthetic agents, at the dosage used during anaesthesia, blocked the response of these hormones to the surgical stress likely due to a block of the hypothalamic-pituitary response.

[Anesthesia in the early surgical therapy of myelomeningocele]

Anaesthetic procedures in surgical repair of meningomyelocele in pediatric patients with particular reference to the problems concerning the specific pathology and the newborn age are reported. Authors consider that surgical repair in the first days of life assures a lesser incidence of leptomeningeal infections and a better functional improvement without an important increase of the anaesthetic risk.