Effects of general anaesthetics on the pH of gastric contents in man during surgery: a survey of halothane, fluoroxene and cyclopropane anesthesia.

The effect of premedication and three general anaesthetics on gastric content pH was investigated. Neither premedication with pentobarbital-atropine nor morphine-scopolamine given 1-2 h prior to anaesthesia appeared to affect the acidity of the gastric contents. Halothane invaribly increased the pH of the gastric contents; none of the seven patients studied had a gastric pH of less than 2.5 (mean 5.1) after 1 h of anesthesia. Cyclopropane uniformly maintained the acidity of the gastric contents; only one out of seven patients had a gastric content pH above 2.5 (mean 1.7) after 1 h of anaesthesia. This effect of cyclopropane in maintaining the pH of gastric contents was unaffected by the use of premedication and induction with thiopental. Fluorexene affected the pH of the gastric contents much less uniformly. Although the pH for the group as a whole gradually increased (after one hour from 1.7 plus or minus 0.2 (s.e. mean) to 3.1 plus or minus 0.7), some of the seven patients studied reacted to fluroxene with a constant low gastric content pH. The findings are discussed, and it is concluded that the risk of pulmonary complications in case of vomiting and aspiration upon emergence from anaesthesia is greater if the anaesthetic agent is cyclopropane or fluoroxene, than if it is halothane.

Effects of respiratory acidosis on the arrhythmia threshold during fluroxene and halothane anesthesia.

Hypercarbia was induced in 12 patients anesthetized with either halothane or fluroxene in an inspired concentration of approximately 1.3 MAC (1% halothane and 4-5% fluroxene). The six patients receiving halothane anesthesia responded to hypercarbia with a pronounced tachycardia, an increased arterial pressure and an electrocardiographically monitored threshold level for ventricular arrhythmias at a Paco2 level averaging 98 mmHg. The six patients receiving fluroxene anesthesia responded to hypercarbia with both tachycardia and hypertension, but in spite of an average Paco2 level of 109 mmHg, no ventricular arrhythmias could be provoked. It is therefore suggested that within the non-narcotic level of hypercarbia a threshold level for cardiac arrhythmias does not exist under fluroxene anesthesia.

The effects of etomidate on arterial pressure, pulse rate and preganglionic sympathetic activity in cats.

We have studied the effects of etomidate on preganglionic cervical sympathetic activity, arterial pressure, and pulse rate. Normal and baroreceptor-denervated animals were studied. On the basis of findings it is concluded that etomidate exerts a minimal direct depressant action on the cardiovascular system. A profound depression of sympathetic tone was observed in spite of unaffected arterial pressure. Etomidate was also shown to possess a mild vagolytic action.

The effects of althesin on arterial pressure, pulse rate preganglionic sympathetic activity and barostatic reflexes in cats.

We have studied the effects of Althesin on preganglionic cervical sympathetic nervous activity, arterial pressure, pulse rate and barostatic reflexes in cats. Normal, baroreceptor denervated and decerebrate animals were studied. On the basis of our finding it is concluded that Althesin severely depresses sympathetic nervous activity by action on the vasomotor centre. The depression of arterial pressure however was only moderate due to two compensatory mechanisms: a vagolytic action of Althesin and a peripheral vascular effect believed to be caused by an enhanced action of catecholamines caused by Althesin. Barostatic reflexes were found active under conditions where Althesin did not totally abolish sympathetic tone.

Cardiovascular effects of pancuronium in patients anaesthetized with enflurane and fluroxene.

The effects of pancuronium on the blood pressure and pulse rate were investigated in patients anaesthetized with either fluroxene or ethrane prior to the surgical procedure. At surgical levels of fluroxene anaesthesia, pancuronium increased the blood pressure and pulse rate significantly. In the patients anaesthetized with ethrane, the blood pressure did not change and the pulse rate rose only temporarily and to a less significant level. Analysis of the changes in pulse rate shows that the greater increase produced by fluroxene was due in part to the initial bradycardic effect of this anaesthetic. However the consistent elevation of blood pressure in this group can only be explained by sympathetic stimulation produced by fluroxene and unmasked by pancuronium. Previous administration of atropine suppresses the effect of pancuronium regardless of the anaesthetic in use.

The effects of propanidid on arterial pressure, pulse rate, preganglionic sympathetic activity and barostatic reflexes in the cat.

We have studied the effects of propanidid on preganglionic cervical sympathetic nervous activity, arterial pressure, pulse rate and barostatic reflexes of the cat. Normal, hypertensive, baroreceptor denervated and decerebrate animals with sectioned vagal nerves were studied. On the basis of our findings it is concluded that propanidid exerts its depressant action on the cardiovascular system directly. Central circulatory control mechanisms are essentially unaffected. The depression of arterial pressure caused by propanidid is moderated by two compensatory mechanisms: normal barostatic reflexes causing an increased sympathetic tone in response to hypotension and a vagolytic action of propanidid.

The effect of propanidid on systemic vascular resistance in man.

We have studied the peripheral vascular effect in man of propanidid 6 mg/kg, administered as a bolus injection during cardiopulmonary by-pass with the aorta cross-clamped and at constant perfusion flow. Ten measurements in eight patients were performed. A decrease was found in systemic vascular resistance: from 150.7 +/- 16.3 to 99.5 +/- 10.1 kPa x s/1. No venous pooling occurred. It is concluded that, in man, propanidid causes a vasodilation which must contribute to the hypotension it causes.

Percutaneous catheterization of the internal jugular vein.

Two techniques for catheterization of the internal jugular vein are described in detail. In a group of 108 adults and 54 children, catheterization of the internal jugular vein was attempted 168 times. Failure to achieve catheterization occurred 12 times. The success rate for the first 50 patients was 86%, but it increased with experience, and was nearly 96% for the remaining patients. Almost 90% of catherizations were achieved on the first or second attempt. The success rate was understandably lower in the children's group. Catheter malpositioning occurred infrequently (six times) and was most common in the children's group. There were few complications, although two were of a serious nature. The techniques described are straightforward, easy to master and perform, and are recommended as useful additions to the anaesthetist's clinical armamentarium.

Heart rate changes caused by enflurane and halothane anaesthesia in man.

Changes in heart rate and arterial pressure caused by enflurane and halothane anaesthesia were investigated in patients premedicated with diazepam and scopolamine. Enflurane caused a significant (12%) increase in heart rate and depression of arterial pressure (23%). Halothane depressed heart rate significantly (14%), whereas arterial pressure was unaffected. The authors conclude that enflurane possesses a positive chronotropic effect.

Increase in extracellular potassium in the brain during circulatory arrest: effects of hypothermia, lidocaine, and thiopental.

The effect of temperature (37 degrees C, 28 degrees C, and 18 degrees C), 160 mg/kg lidocaine, and 40 mg/kg thiopental on the efflux of cellular potassium in the cerebral cortex during complete global ischemia was examined. Cerebral ischemia was induced in dogs on cardiopulmonary bypass circulation by stopping the pump. Potassium concentration was measured on the brain surface by a valino-mycine-membrane electrode, which in its response corresponded well to an inserted microelectrode. Hypothermia reduced the ischemic potassium efflux rate to about 50 per cent at 28 degrees C, and about 25 per cent at 18 degrees C. At all temperature levels lidocaine caused an additional reduction in the potassium efflux rate of about 50 per cent, probably by reducing membrane ion permeability in accordance with its local anesthetic action. Thiopental had no effect on the potassium efflux during ischemia. This study opens the possibility that lidocaine, like hypothermia, may provide protection of the ischemic brain.

Moderate hypotensive anaesthesia for reduction of blood loss during total hip replacement.

Thirty-two consecutive patients scheduled for total hip replacement were randomly allocated to receive either neurolept anaesthesia or halothane anaesthesia. In the halothane group, systolic blood pressure was reduced to 10.69-13.33 kPa in normotensive patients, and to 13.33-16.0 kPa in hypertensive patients by adjusting the inspired halothane concentration and using supplementary fentanyl when necessary. In the neurolept group, no attempt was made to reduce blood pressure below the level achieved with adequate anaesthetic doses of fentanyl and droperidol. The average peroperative blood loss in the halothane group was 809 ml (range 250-1700 ml); this was significantly lower than in the neurolept anaesthesia group in which an average blood loss of 1909 ml (range 600-4900 ml) occurred. Moderate hypotensive halothane anaesthesia is recommended as an anaesthetic technique for total hip replacement.

Cardiovascular effects of etomidate used for induction and in combination with fentanyl-pancuronium for maintenance of anaesthesia in patients with valvular heart disease.

The effects of induction of anaesthesia by etomidate 3 mg kg-1 followed by continuous infusion of etomidate 2 mg min-1, fentanyl 0.01 mg.kg-1 and pancuronium 0.1 mg.kg-1 were studied in ten patients with valvular heart disease. No haemodynamic changes were seen injection of etomidate, but after fentanyl was given there was a significant decline in cardiac index (10%), in mean arterial systemic pressure (20%), in systemic vascular resistance (14%), in left ventricular minute work index (27%) and in right ventricular minute work index (21%) compared to the control values. After supplementing with pancuronium, no further significant changes were seen. There was no significant change in the pulmonary vascular resistance during the whole study. In conclusion, it appears that etomidate is a safe intravenous agent, and is worth further study, in particular in patients with minimal cardiac reserve requiring high inspired oxygen tension.

Intravenous lidocaine as a suppressant of persistent cough caused by bronchoscopy.

The effect of intravenous lidocaine in the treatment of persistent cough occurring after diagnostic bronchoscopies performed under general anaesthesia was investigated in a controlled clinical trial. The study comprised 28 adults patients, all of whom had regained consciousness after anaesthesia. Fifteen patients were treated with lidocaine (1.05 mg/kg body weight) and 13 patients with placebo (saline). In each patient the intravenously injected dose was repeated once after 5 min. In 11 of the 15 patients (73%) who received lidocaine coughing ceased, while it continued in all 13 patients in the placebo group. The difference is highly significant (P less than 0.001). None of the patients developed side effects such as hypotension, arrhythmias, central nervous system symptoms or respiratory depression after injection of lidocaine. It is therefore concluded that intravenous lidocaine in man is a safe and useful cough-suppressant.

Sympathetic nervous system response to lidocaine induced seizures in cats.

The effect on arterial pressure, EEG, preganglionic sympathetic nervous activity and pulse rate of repeated intravenous administrations of lidocaine (3 mg/kg) was investigated in cats anaesthetized with nitrous oxide. A continuous high voltage, burst-suppression EEG indicating constant seizure activity was found, whereas arterial pressure and sympathetic nervous activity did not change significantly. Although the onset of EEG seizure activity did not change the mean sympathetic activity level, the pattern of firing changed dramatically as every EEG seizure triggered a burst of sympathetic impulses. Barostatic reflexes were active after lidocaine administration unless seizure activity occurred. Thiopental 5 mg/kg given intravenously to cats during continuous lidocaine-induced EEG seizures always abolished the seizure activity without excessive depression of arterial pressure.

The incidence of cardiac arrhythmias and arterial hypotension subsequent to standardized surgical stimuli in patients undergoing thoracotomy. With reference to enflurane and halothane.

A main factor which might cause cardiac arrhythmias and arterial hypotension during thoracic operations is surgical manipulation around the pericardium and the lung hilus. Halothane and enflurane were compared as to the occurrence of arrhythmias and hypotension caused by standardized surgical stimulation. Twenty-eight patients scheduled for thoracotomy were studied. The patients were selected in randomized order, and the anaesthetic agent in use was unknown to the surgeon. ECG, intra-arterial blood pressure and central venous pressure were recorded continuously. Six patients in the halothane group (n = 14) and nine patients in the enflurane group (n = 14) developed premature atrial contractions and nodal rhythm, while nine patients in the halothane group and five in the enflurane group developed a fall in systolic blood pressure of more than 20 mmHg (2.7 kPa). No statistically significant difference in the occurrence of cardiac arrhythmias and hypotension was found between the two anaesthetic groups.

Haemodynamic effects of intravenous procaine as a supplement to general anaesthesia in patients with valvular heart disease.

The effect of intravenous procaine, 2 mg/kg/min, on the cardiovascular function of nine patients scheduled for cardiac valve replacement was studied under enflurane-pancuronium anaesthesia. Procaine infusion was started after intubation during steady-state anaesthesia, and continued until start of cardiopulmonary by-pass. Systemic vascular resistance decreased steadily from 198.2 +/- 28.7 to 133.0 +/- 17.2 kPa X s/l (P less than 0.05). A simultaneous decline in mean arterial pressure from 10.13 +/- 0.68 to 7.47 +/- 0.48 kPa was observed (P less than 0.01). Cardiac index, heart rate, central venous pressure, pulmonary arterial mean pressure and pulmonary capillary wedge pressure were all unaffected by procaine as well as by surgical stimulation. It is concluded that continuous procaine infusion as an adjuvant to general anaesthesia effectively abolishes the hypertensive and tachycardiac response to surgical stimulation. The limiting factor in the amount of infused procaine appears to be the hypotension caused by vasodilation, not myocardial depression or convulsions.

Inability to elicit vagal responses from the acid-infused esophagus of pigs.

Acid application in the esophagus and esophageal distension were undertaken in pigs. One group (n = 9) had operatively induced esophagitis. The other group (n = 7) was normal. We found no discrepancy between the groups neither in inspiratory pressure nor in expiratory PCO2 nor in plasma concentrations of pancreatic polypeptide. The results indicate inability to elicit vagal responses from the acid-infused esophagus of pigs.

Haemodynamic effects of enflurane in patients with valvular heart disease.

In eight patients undergoing cardiac surgery for aortic and/or mitral valvular disease, mean arterial blood pressure (MAP), central venous pressure (CVP), cardiac index (CI), stroke index (SI), pulmonary capillary wedge pressure (PCWP), and pulmonary arterial mean pressure (PAMP) were measured after premedications with diazepam-scopolamine (I), after breathing 100% oxygen (II), and on controlled respiration (III) after induction of anaesthesia with enflurane-O2, and endotracheal intubation facilitated by succinylcholine. All measurements were done prior to surgery. Enflurane anaesthesia was found not to affect cardiac index. The average SI decreased by 27%, but was compensated for by an average increase in heart rate (HR) of 33%. The average systemic vascular resistance (SVR) decreased by 14%. All other measured parameters were found to be unaffected by enflurane-O2 anaesthesia. It is concluded that the cardiovascular stability observed in healthy young normals during enflurane anaesthesia is preserved in patients with moderate to severe heart failure, making enflurane an anaesthetic agent well suited for patients with cardiac disease.