Showing papers in "Acta Anaesthesiologica Scandinavica in 1976"

Breathing mechanics, dead space and gas exchange in the extremely obese, breathing spontaneously and during anaesthesia with intermittent positive pressure ventilation.

Abstract: Breathing mechanics and gas exchange were studied in 10 extremely obese subjects (average weight 138 kg) prior to and during anaesthesia with mechanical ventilation. Breathing mechanics were analysed from measurements of transpulmonary pressure (during anaesthesia, trans-chest wall pressure as well) inspiratory gas flow and tidal volume. Gas exchange was studied by analysing inspired and from the Bohr equation, and the division into anatomical and alveolar dead space was arrived at by capnography. The patients were anaesthetised with neuroltpt agents and ventilated with an air-oxygen mixture. Lung compliance during spontaneous breathing was below normal and decreased further during artificial ventilation. Chest wall compliance measured during anaesthesia was within normal limits. Lung resistance was above normal during spontaneous breathing and increased further during mechanical ventilation. Total dead space was normal during spontaneous breathing and increased moderately during artificial ventilation, the increment coming mainly from alveolar dead space. A moderate hypoxaemia was recorded during spontaneous breathing, and the alveolar-arterial oxygen tension difference was slightly elevated. During anaesthesia this difference was markedly greater. It is concluded that the most probable reason for the relative hypoxaemia is right-to-left shunting.

Anesthetic Management of Posterior Fossa Surgery in the Sitting Position

Abstract: From the surgical aspect, the sitting position gives good surgical access to the operative site, improves venous drainage, gives a better view of facial area for monitoring evoked responses from cranial nerve stimulation and allows for better ventilation. Conversely, the sitting position can present complications such as air emboli, postural hypotension and serious cardiac arrhythmias due to surgical stimulation of cranial nerves and brainstem. This paper presents our clinical experience in 180 neurosurgical procedures on the posterior fossa in the sitting position. The standardized anesthetic technique consisted of narcotic, muscle relaxant, nitrous oxide and controlled ventilation. All patients were monitored with ECG, direct arterial and venous pressure, discontinuous blood gases, and expiratory CO2 and urinary output. Air embolism was detected via Doppler ultrasonic detector and evacuated through a right atrial catheter. Air was detected, visualized and aspirated in 45 cases for an incidence of 25%, with most episodes occurring early in the procedure. In 11 cases (6%) air was detected on closure. There were no deaths in this series. Fifty-eight patients (32%) had a 10-20 mmHg drop in blood pressure on reaching the sitting position, 19 became temporarily hypertensive (10.5%), and the remainder were normotensive. In 46 patients (25%), bradycardia developed during retraction-manipulation-stimulation of structures on or adjacent to brainstem as well as to cranial nerves. Surgical stress also accounted for the 13 patients (7%) having frequent premature ventricular extrasystoles. One case of profound hypotension and another case of virtual cardiac standstill were noted during the use of the bipolar electrocautery at or near the fifth nerve exit from brainstem. Additional hemodynamic data, the physiopathology, diagnosis and treatment of air embolism is discussed.

Misplacement and loop formation of central venous catheters.

Abstract: Exact placement is an essential prerequisite for long-term use of a central venous catheter Reported data show an extremely wide range of catheteral misplacements: from less than 1% to more than 60% Some approaches appear to be less advantageous than others, but the highest rates of misplacement occur in the cubital, external jugular and saphenous veins A series is presented of 378 radiographically controlled central venous catheters analysed for aberrant placement and loop formation The total occurrence of faulty positioning and coiling reached 53%, while the respective incidences were 30% for the external jugular vein, 57% for the internal jugular vein, 55% for the infraclavicular technique of subclavian venepuncture, 53% for the innominate vein and 14% for the supraclavicular approach of subclavian venepuncture The total frequency for pure loop formation was 29% The authors discuss numerous reported data on catheter malpositioning, according to the specific techniques used, and compare them with thier own results The relatively low incidence in the present series is possibly due to the high proportion of cases where the supraclavicular subclavian approach was used, the omission of the sphrenous/femoral and cubital techniques, and to pre-determining the length of the inserted catheteral segments

Airway closure and distribution of inspired gas in the extremely obese, breathing spontaneously and during anaesthesia with intermittent positive pressure ventilation.

Abstract: Airway closure (closing capacity, CC), FRC, total efficiency of ventilation (lung clearance index, LCI) and distribution of inspired gas (nitrogen washout delay percentage, NWOD) were determined by nitrogen washout techniques and arterial Po2 and Pco2 measured by standard electrodes in 10 extremely obese subjects, prior to and during anaesthesia and artificial ventilation. CC was normal, but because of small FRC, airway closure occurred within a tidal breath in 9 out of 10 subjects during spontaneous breathing, when awake. Po2 was reduced, the hypoxaemia correlating to the magnitude of airway closure. LCI was normal, but NWOD was borderline. During anaesthesia, CC was unaltered but FRC was further reduced, so that in nine subjects airway closure occurred above FRC and tidal volume together. A marked increase in relative hypoxaemia was recorded. LCI and NWOD rose, indicating less efficient and less even ventilation. It is concluded that airway closure reasonably explains the marked hypoxaemia in obese subjects during anaesthesia, and that it may also be the reason for the uneven distribution of inspired gas.

The effect of segmental epidural analgesia on maternal and foetal acid-base balance, lactate, serum potassium and creatine phosphokinase during labour.

Abstract: Maternal and foetal acid-base balance, PaO2, lactate, potassium and creatine phosphokinase (CPK) were studied during the course of 28 induced labours. Every second mother received segmental epidural analgesia during the first stage of labour (epidural group), while the remaining mothers (who were given pethidine for pain relief, if necessary) acted as a control group. In the epidural group the patients had only minimal changes in acid-base balance and lactate concentration during the first stage. During the second stage lactate concentration increased. In the control group, on the other hand, the acid-base balance showed signs of hyperventilation and lactic acid accumulation during the first stage. The potassium changes were quite minimal and were not significantly different between the groups. The CPK level did not change during labour, but 2 and 4 h after delivery it was significantly elevated in both groups. The foetal acid-base balance, potassium, lactate and PaO2 values revealed no differences between the groups at any time. The CPK level in umbilical venous blood was significantly higher in the epidural group.

The effect of nitrous oxide on oxygen consumption and blood flow in the cerebral cortex of the rat.

Abstract: The effect of 70% nitrous oxide upon cerebral oxygen consumption (CMRo2) and cerebral blood flow (CBF) was studied in artificially ventilated rats. The control groups consisted of unanaesthetized animals in which a stress-induced increase in CMRo2 and CBF was prevented by previous adrenalectomy, or by administration of a beta blocker (propranolol). There were no significant differences in CMRo2 between animals ventilated with either N2O or N2. It is concluded that if nitrous oxide depresses cerebral metabolism the depression cannot exceed 10%.

Halothane‐Induced Liver Damage: An Analysis of the Material Reported to the Swedish Adverse Drug Reaction Committee, 1966–1973

Abstract: An analysis of 94 reports to the Swedish Adverse Drug Reaction Committee of patients with liver injury after surgery and halothane anaesthesia (including 13 fatal cases) has not been able to reveal any other factors responsible for the liver injury than the halothane administration. Eighty-two per cent of the total material and 12 out of 13 fatal cases had had multiple exposures. Our results suggest that the liver injury becomes more severe after repeated exposures; maximum serum bilirubin and SGOT values are higher after an increasing number of halothane exposures.

Diazepam in Emulsion Form for Intravenous Usage

Abstract: Since aqueous solutions of diazepam were introduced into clinical practice, the problem has arisen of local vascular side effects after intravenous injection. A new preparation of diazepam as a lipid emulsion is presented. It was prepared by Vitrum and shows many similarities to Intralipid. A clinical trial was designed to study the incidence of pain in connection with the intravenous injection of diazepam and the incidence of subsequent thrombophlebitis. The preparation was used as a sedative to patients before gastroscopic investigation and as an inductor to general anaesthesia. In the material of 88 patients, thrombophlebitis was observed in 1.1%. Only 1 patient in the group of 314 patients studied complained of pain in connection with injection. The results observed were compared with previous investigations from the literature and with parallel control investigations. The new lipid emulsion form of the preparation was found to reduce significantly the incidence of local side effects involving the venous system. No significant difference in the therapeutic effect of the different preparative forms of the active substance was observed. The possible mechanisms involving the production of thrombophelbitis in connection with the injection of aqueous solutions of diazepam are discussed.

Left Ventricular Ejection and the Heather Index Measured by Non‐Invasive Methods during Postural Changes in Man

Abstract: Differences have been found, which are usually 1% or less, between the left ventricular ejection time measured from the external carotid pulse tracing, and from the rate of change of thoracic impedance (dZ/dt) waveform, using either the second heart sound or the X-point of the dZ/dt tracing as the end-point. The Heather Index obtained from the ECG and dZ/dt tracings has been correlated with other indices of cardiac performance. The changes observed in the physiological variables during head-up and head-down tilting were in the expected directions.

Effect of Ketamine Anaesthesia on the Content of Monoamines and their Metabolites in the Rat Brain

Abstract: The effects of ketamine anaesthesia (100 mg/kg i.p.) on the content of brain 5-hydroxytryptamine (5HT), 5-hydroxyindoleacetic acid (5HIAA), noradrenaline (NA), dopamine (DA) and homovanillic acid (HVA) were studied in male Wistar rats. Fifteen min after ketamine injection, when the rats were deeply anaesthetized, the 5HT content in many brain regions tended to be increased. An opposite tendency was found in the brain 5HIAA content. In rats treated with probenecid, which markedly lengthened ketamine anaesthesia, the accumulation of SHIAA was significantly reduced by ketamine. In addition to ketamine anaesthesia, probenecid was found to lengthen thiopental anaesthesia. One hour after the ketamine administration, when the rats were no longer anaesthetized but were excited, the brain NA concentration was increased by 17% (P < 0.02). The brain DA content was unchanged, but at 15 min and 1 hour after ketamine administration the striatal HVA content was increased by about 55% (P< 0.05), suggesting an increased turnover of DA. The results suggest that during recovery from ketamine anaesthesia the increased NA content and the increased DA turnover may be associated with the post-anaesthetic excitement of the rat, whereas the decrease in brain 5HIAA content may coincide with the deepening of ketamine anaesthesia.

Pressure and volume changes in tracheal tube cuffs during anaesthesia.

Abstract: Recently, it has been observed that, when a patient is breathing a nitrous oxide-oxygen mixture and the cuff of the tracheal tube is filled with air, nitrous oxide may diffuse into the cuff and thereby cause an increase in volume and pressure. In the present investigation, different gas mixtures were used to fill the cuff, and repeated measurements of pressure, and occasionally of volume, were made during anaesthesia. Both large-volume and small-volume cuffs were studied. A considerable increase in volume and pressure took place in both types of cuffs. The changes were directly proportional to time for the first few hours. If the cuff was inflated with nitrous oxide-oxygen, no pressure increase occurred, and this was also true for the air-filled cuff if halothane anaesthesia was given.

Anesthesia for Cesarean Section IV

Abstract: Epidural analgesia with bupivacaine was used for elective cesarean section, and repeated maternal and neonatal blood samples were collected over 24 h for calculation of drug concentration. A gas-chromatogrphic micro-method was used for the analysis. The aim of this investigation was to evaluate the placental transfer and the elimination rate of the drug. No signs of systemic toxicity were observed in any mother or child, despite relatively high blood concentrations. The fetal-maternal ratio of concentrations at delivery was higher than in previous studies, most probably due to the protein-binding characteristics of bupivacaine and the dosage used. The biological half-life of the rapid phase of elimination (alpha-phase) in the newborn was shorter than in the mother (P less than 0.002), indicating a more rapid distribution process. The half-life of the slow phase of elimination (beta-phase) in the newborn was of the same magnitude as in the mother, indicating that neonatal elimination processes of bupivacaine may be well developed at birth.

Thoracic epidural analgesia-II: prolongation in the early postoperative period by continuous injection of 1.0% bupivacaine.

Abstract: Sixteen patients were given thoracic epidural analgesia at the T5-T6 level with 2 ml of 1.0% bupivacaine solution plain for pain relief after upper abdominal surgery. In 13 cases the analgesia was prolonged by continuous injection of 1.0% bupivacaine for 24 or 48 h. Onset time and segmental spread of the analgesia are presented as well as segmental spread, intensity of the blockade, and peak expiratory flow rates during prolongation. Signs of tachyphylaxis were noticed, and also signs of accumulation of bupivacaine in plasma. A high incidence of urinary retention occurred. The method is not considered to be ideal for pain relief after upper abdominal surgery.

Electroencephalographic study of children during ketamine anesthesia.

Abstract: EEG was recorded on nine occasions of ketamine anesthesia in eight children. Two of the patients were neurologically normal and six were under investigation for various neurological disorders. The EEG during the catatonic phase of ketamine anesthesia is characterized by alternating high amplitude delta complexes and periods of fast activity. The two cases which in the routine EEG showed focal paroxysmal activity did not show any electroencephalographic aggravation or clinical seizure during ketamine influence. One case exhibiting a subcortical type of epileptiform activity showed a marked potentiation of this activity with ketamine. On routine neurological examination during the catatonic phase of ketamine anesthesia the pharyngeal reflex was generally weak and failed altogether in two cases and corneal reflexes were absent in three cases.

Amnesic action of and skills related to driving after intravenous flunitrazepam

Abstract: Amnesic action, skills related to driving and the ability to discriminate the fusion of flickering light were measured double-blind in 29 healthy volunteers before and after three doses of intravenous flunitrazepam. Every subject experienced amnesia for the pinching of the abdomen after being injected with flunitrazepam. Even the smallest dose of flunitrazepam (0.01 mg/kg) caused the amnesia without affecting the level of consciousness. The late effects of flunitrazepam were the most harmful to coordination. With 0.01 mg/kg eye-hand coordination was slightly impaired for as long as 6 h after the injection, and after 0.02 and 0.03 mg/kg the impairment was still significant (P less than 0.05) at the last observation period 10 h after the injection. It was concluded that, because the amnesic action of flunitrazepam is more effective than that of clinically comparable doses of diazepam, further clinical experiments with flunitrazepam are warranted. Its longer and more harmful effects on psychomotor performance than those of equipotent doses of diazepam suggest that doses of 0.02 mg/kg or more of flunitrazepam should be avoided in outpatient anaesthesia or sedation.

Oxygen Transport and Venous Admixture in the Extremely Obese. Influence of Anaesthesia and Artificial Ventilation with and without Positive End‐Expiratory Pressure

Abstract: Eight extremely obese patients (mean weight 136 kg) were studied when awake and breathing air, and during anaesthesia with controlled ventilation (oxygen fraction in inspirate (FIO2): 0.5). During anaesthesia, the atients were first studied with zero end-expiratory pressure (ZEEP) ventilation. Then two different positive end-expiratory pressures (PEEP) were applied, 10 cmH2O and 15 cmH2O, in order to study the effect of an increase in functional residual capacity (FRC). Arterial oxygenation and oxygen availability, as well as cardiac output (QT) and venous admixture (QS/QT) were studied. With the institution of anaesthesia and ZEEP, the alveolar arterial oxygen tension difference (P(A-a)O2) rose from 3.5 +/- 1.1 to 28.4 +/- 2.6 kPa, and the oxygen availability fell from 1346 +/- 222 to 1039 +/- 239 ml/min, due to the additive effect of an increase in QS/QT from 10 +/- 4 to 21 +/- 5% and a fall in QT, from 7.7 +/- 1.2 to 5.5 +/- 1.1 1/min. With increasing levels of PEEP, despite a fall in P(A-a)O2, there was a reduction in oxygen availability. This was due to simultaneous reduction in QS/QT and QT. At a PEEP of 15cmH2O, the P(A-a)O2 was 21.2 +/- 7.1 kPa, oxygen availability 862 +/- 170 ml/min, QS/QT 13 +/- 4 and QT 4.4 +/- 0.6 1. It is concluded that PEEP ventilation significantly reduces QS/QT in extremely obese patients during anaesthesia and should be used in these patients if there is arterial hypoxemia despite a high FIO2.

Suxamethonium Apnoea Terminated with Commercial Serumcholinesterase

Abstract: A case of prolonged suxamethonium apnoea successfully terminated by the infusion of a commercial preparation of serumcholinesterase is reported. The patient appeared to be homozygous for the dibucaine resistant gene, having only 15% of normal activity in his serum. His dibucaine number was 21, and the Michaelis constant was 5.5 times that of normal sera. One and a half hours after receiving 110 mg suxamethonium for oesophagoscopy, the patient was still apnoeic with no response to ulnar nerve stimulation. Intravenous administration of 90 mg commercial serumcholinesterase, the equivalent to 1000 ml fresh human plasma, restored twitch and tetanic responses and the patient could lift his head 15 min after the beginning of the enzyme injection. The serumcholinesterase activity of the patient's serum increased by 55% (from 15% to 70%) following the injection. This rise was halved over the next 8 days.

Respiration and Circulation after Total Hip Replacement Surgery

Abstract: The cardiopulmonary effects of two different types of postoperative analgesic regimens were compared in 31 cardiorespiratorily healthy patients subjected to total hip replacement surgery. The investigation was performed preoperatively on the morning of the day of surgery and during the first 3 days postoperatively. All patients received continuous lumbar epidural analgesia preoperatively, during surgery and up to the end of the first measurement period, which started 2.5 h after surgery. Ten patients were subsequently given pentazocine (Fortalgesic®) intramuscularly on demand for pain relief throughout the investigation, while 14 patients received 0.4% plain lidocaine (Xylocain®), and seven patients 0.4% lidocaine with adrenaline (1/400,000) as a continuous lumbar epidural drip for analgesia throughout the investigation. It was confirmed that the operative procedure itself did not significantly influence the postoperative arterial oxygenation, while the type of postoperative analgesic regimen was of considerable importance in this respect. Thus, patients given pentazocine showed a significant increase in pulmonary venous admixture, due both to an increase in true shunt and to an increase in ventilation/perfusion disturbances. This pattern, of poor pulmonary function still persisted on the third postoperative day, and caused a significant decrease in Pao, during days 1 to 3 postoperatively. In patients given an epidural block no significant changes in pulmonary venous admixture were noted postoperatively, and thus there was no reduction in Pao2. All patients, irrespective of the type of analgesic regimen used, had a significantly increased cardiac index and oxygen uptake postoperatively, although patients given an epidural block showed a greater increase in cardiac index, and thus a tendency towards a more hyperkinetic circulation than those given pentazocine.

The effect of halothane anaesthesia upon cerebral oxygen consumption in the rat

Abstract: The influence of halothane (0.6 and 2%) upon cerebral (cortical) blood flow (CBF) and cerebral metabolic rate for oxygen (CMRo2) was studied in artificially ventilated rats, using a modified technique of Kety & Schmidt (1948). The values obtained in halothane anaesthesia were compared to those recorded in nitrous oxide anaesthesia, or to those measured in unanesthetized animals given an analgesic drug (fentanyl citrate). Although it could be confirmed that halothane induces vasodilatation in the brain, there were relatively small differences in CBF between the groups. The results demonstrate that, in the rat, halothane depresses CMRo2 in a dose-dependent way. With 0.6% halothane, CMRo2 was reduced by 20-30% and, with 2% halothane, CMRo2 was reduced by about 50%. Thus, in the rat the effect of 2% halothane upon metabolic rate is comparable to that observed in barbiturate anaesthesia.

Halothane anaesthesia in caesarean section.

Abstract: The safety and efficacy of halothane anaesthesia were investigated in 97 caesarean sections using 0.4-0.6% halothane added to a mixture of 61 N2O/3-4 1 O2. The administration of halothane was initiated before intubation and terminated immediately prior to delivery. Only one patient reported memories from the operation. The mean Apgar score 1 min after delivery (8.5) was significantly better than that (8.2) in 100 caesarean sections in which a mixture of 71 N2O/3 1 O2 was used. In 17 caesarean sections, the halothane concentrations were examined after 0.9% halothane had been given for exactly 1 min after intubation. It was found that halothane reached and passed the placenta after only 1 min. The levels in the maternal artery and umbilical vein were comparable. The levels in the maternal artery, maternal vein and umbilical vein were markedly higher than in the umbilical artery, which indicated an accumulation of halothane in the foetal tissues. However, due to the vigour of the newborn, halothane concentrations 10 min after birth were very low. The half-life of halothane in the maternal circulation was approximately 1 min with the described method of administration. Blood gas determinations, which were made in seven newborns, proved satisfactory.

Arrhythmias during Halothane Anesthesia I: The Influence of Atropine During Induction with Intubation

Abstract: The changes in cardiac rhythm which occurred during induction of halothane-N2O/O2 anesthesia with thiopenthal and one single dose of suxamethonium for intubation were studied in two groups of patients, one (at random) of which was given atropine intravenously 0.1 mg/10 kg 2 min before induction. There was a significantly higher incidence of arrhythmias in the atropine group (P < 0.01) - including sinustachycardia ® 120 beats/min. The most common arrhythmias were supra ventricular ectopies. About half of those registered in the atropine group arose in direct connection with atropine administration. There was a relative accumulation of arrhythmias in connection with intubation in both groups. Ventricular ectopies were only observed during and immediately after intubation, and most often in the atropine group. The occurrence of arrhythmias was not age-dependent. The cardioacceleration following intubation was significantly higher in the atropine group (P<0.01). No consistent changes in blood pressure as the result of the change in cardiac rhythm were observed in connection with the single arrhythmia episode or following atropine. On the other hand, no advantage could be seen in the use of the drug, and the cardioacceleration which is inherent in its action may be injurious to patients with a limited cardiac reserve.

The haemodynamic effects of nitrous oxide anaesthesia on systemic and pulmonary circulation in dogs.

Abstract: The haemodvnamic effects of nitrous oxide in normoxia (20% oxygen) and in hyperoxia (50% oxygen) were investigated in 13 dogs. Nitrous oxide in hyperoxia caused a significant rise in total peripheral resistance and a significant decrease in cardiac output, heart rate, myocardial contractility (dP/dt max) and cardiac worl?. On the other hand, nitrous oxide in normoxia seemed to reverse these findings and did not exert any negative inotropic effects on the myocardium. The results indicate that the earlier reported sympathetic activation of the circulation may be related to hyperoxia and not to nitrous oxide as such.

Arterial and venous blood lidocaine concentrations after local anaesthesia of the respiratory tract using an ultrasonic nebulizer.

Abstract: Arterial and venous blood lidocaine concentrations were intermittently measured in 15 bronchoscopy patients in whom local anaesthesia was induced by an inhalation technique. A DeVillbiss ultrasonic nebulizer model 3574 was used. The anaesthetic was 10 ml of 4% lidocaine without adrenaline. Blood concentrations were measured 5 min after commencement of inhalation, on completion of inhalation, and then after 10, 30 and 60 min. Statistically significantly higher concentrations were found in the arterial blood at the first two sampling times (P less than 0.01 and P less than 0.05, respectively). The highest average concentration in both arterial and venous blood eas reached 10 min after completion of anaesthesia. After 30 min, there was no difference between the arterial and venous samples; and after 60 min, the concentration was higher in venous blood. The highest individual concentration was 2.8 mug/ml in arterial blood and 2.1 mug/ml in venous blood, well below that reported to cause systemic toxic symptoms. Thus, the inhalation technique may be considered a safe means of inducing anaesthesia in the respiratory tract.

Reduction of Psychotomimetic Side Effects of Ketalar® (Ketamine) by Rohypnol®(Flunitrazepam) A Randomized, Double‐Blind Trial

Abstract: A double-blind controlled trial based on 140 women undergoing abortus provocatus was employed to study whether the frequency of side effects after administration of the anaesthetic Ketalar (ketamine) could be reduced by a con-current dose of Rohypnol (flunitrazepam). The control group was given ketamine alone. The dosage of ketamine was 2 mg/kg body weight, supplemented if necessary by 1 mg/kg, in combination with either 2 mg flunitrazepam or placebo. No other anaesthetics were used. On several counts, the combination of ketamine and flunitrazepam was proved to reduce the adverse reactions seen with ketamine alone. Motor restlessness and confusion in the awakening state occurred with significantly less severity and frequency. Amnesia for dreams was significantly more frequent. Memory of dreams was often unpleasant after ketamine alone. The influence on pulse rate was significantly smaller and no significant changes in systolic blood pressure were seen, whereas a significant increase occurred with ketamine alone. Less pronounced fluctuations in diastolic blood pressure occurred with the combination ketamine-flunitrazepam. Respiratory rate increased significantly with both treatments, but respiratory minute volume was lower with the ketamine-flunitrazepam combination.

Hemodynamic Drug Interaction: Peridural Lidocaine and Intravenous Ephedrine

Abstract: Hypotension following peridural anesthesia with lidocaine was treated by intravenous injection of ephedrine. The ephedrine relieved the cardiovascular depression, but was associated with a concomitant increase in plasma lidocaine concentrations. This increase may push the plasma lidocaine concentration into the toxic region.

Effect of intermittent positive pressure ventilation on cardiac systolic time intervals.

Abstract: The measurement of systolic time intervals (STI) has been widely used as a non-invasive method of assessing the inotropic state of the heart, and normal values are available for healthy individuals breathing spontaneously. The present study was performed in order to evaluate how intermittent positive pressure ventilation (IPPV) affects STI. Ten subjects were investigated before and during halothane anaesthesia for routine surgery. Oesophageal pressure, respiratory minute volume and frequency, arterial blood-gas tensions, cardiac output and heart rate were also measured simultaneously. As expected, the institution of IPPV was associated with a reduction in cardiac output and an increase in oesophageal pressure. Paco2 was reduced. These changes were associated with a considerable lengthening of electro-mechanical systole. This was due to a lengthened pre-ejection period (PEP), whereas the left ventricular ejection time (LVET) was slightly shortened. These changes were even more marked during artifical hyperventilation. The changes in STI are attributed mainly to the reduction of venous return to the heart, subsidiary factors being intrathoracic pressure, myocardial inotropy and vascular resistance.

Anesthesia for cesarean section III: effects of epidural analgesia on the respiratory adaptation of the newborn in elective cesarean section.

Abstract: A rise in fetal Paco2 was observed after elective cesarean section in patients anesthetized both with a barbiturate and with nitrous oxide/oxygen. Epidural analgesia seemed to be a good alternative in order to attain better blood gas values in the newborn infant. Fourteen healthy mothers and their infants were studied in connection with elective cesarean section. Epidural analgesia with plain bupivacaine 0.75% was used. Doses varied between 90 and 120 mg. The time between the epidural injection and delivery was around 50 min. In six cases the fetal heart rate was registered continuously. Most of the mothers were sedated with diazepam intravenously or fully anesthetized, after delivery. The mothers were interviewed later. The respiratory adaptation of the infants was studied by blood gas and acid-base measurements in repeated arterial samples during the first 3 hours of life. A comparison was made with a group previously studied, where general anesthesia with a barbiturate, nitrous oxide/oxygen was the method used. The present material showed no differences concerning Pao2 and Paco2 but clearly indicated a tendency towards an earlier normalization of the initial metabolic acidosis. Mothers showed a respiratory alkalosis which was overcompensated by the metabolic component. Maternal blood pressure falls were observed in four cases, and fetal effects could be detected. Although epidural analgesia has a more favorable effect upon the newborn's metabolic component, both the compared methods allow good respiratory adaptation provided they are used correctly. Mothers can be given the opportunity to choose between being conscious or asleep when their child is delivered.

Halothane Anaesthesia and Suxamethonium I: The Significance of Preoperative Atropine Administration

Abstract: Preoperative administration of atropine was evaluated during induction of halothane anaesthesia with two administrations of suxamethonium 1 mg/kg body weight, 5 min apart. Sixty-eight healthy, adult patients were studied. They were divided into five groups according to dose and route of administration of atropine. EGG was continuously monitored. Serum potassium, pH, Paco2, Pao2 and standard bicarbonate were measured at appropriate intervals. It was found that neither atropine 0.01 mg/kg body weight given intramuscularly 1 h before the anaesthesia nor atropine 0.01 mg/kg body weight given intravenously 5 min prior to induction protected against serious bradycardias (defined as heart rate below 20 beats per minute) following the second dose of suxamethonium. No serious brady-arrhythmias were seen in patients given either a combination of intramuscular and intravenous atropine in the above-mentioned doses or in patients given atropine 0.015 mg/kg body weight intravenously 5 minutes prior to induction. However, a decrease in heart rate to around 40–50 beats per minute occurred in some of these patients. Furthermore, these large doses of atropine caused an increase in heart rate during induction to more than 120 beats per minute in about 50% of the patients and to more than 140 beats per minute in about 25% of the patients. Our results suggest that preoperative administration of atropine does not protect against serious brady-arrhythmias following a second dose of suxamethonium, unless doses of atropine are used which cause tachycardia of considerable degree.

The antagonist effect of naloxone hydrochloride after neuroleptanaesthesia during neurosurgery.

Abstract: The effects of naloxone were studied in 82 patients undergoing intracranial surgery under general anaesthesia with fentanyl or phenoperidine. After the operation was finished the patients' alertness, sensitivity to pain, blood pressure, pulse rate, respiratory rate, tidal and minute volume were recorded parallel with arterial blood gas analyses prior to and immediately after the administration of varying amounts of naloxone i.v. in a single dose. These parameters were also repeatedly controlled for several hours in the postoperative period. The results show that a single i.v. naloxone dose of 1 μg/kg b.w. is effective in the rapid and definite reversal of the respiratory depression caused by the analgesics. This dose was neither correlated to the total amount of analgesics given, nor to the time period which elapsed between the last dose of the analgesic drug and the administration of naloxone. No side effects or complications were encountered when the indicated doses of naloxone were given. It is concluded that, even in a small single dose, naloxone effectively antagonises the respiratory depression caused by fentanyl and phenoperidine without totally eliminating the immediate postoperative analgesic effects of these agents.