Showing papers in "Acta Anaesthesiologica Scandinavica in 1977"

Peripheral nerve injury due to injection needles used for regional anesthesia. An experimental study of the acute effects of needle point trauma.

Abstract: Nerve injury can arise as a complication peripheral nerve block anesthesia. Of the various factors involved, the trauma caused by the injection needle may be of significance. In this experimental study the frequency of fascicular injury was investigated immediately after needling isolated rabbit sciatic nerve preparations, and after intraneural injection with the nerve in situ. Two different injection needles were used, one with a bevel angle of 14 degrees and the other with a 45 degrees bevel angle. Fascicular injury was indicated by a fluorescence microscopy technique, tracing locally applied Evans Blue Albumin, The results show that a 45 degrees-beveled needle less frequently produces fascicular damage and should therefore be recommended for use in clinical anesthesia. It is also concluded that paresthesiae, when necessary, should be elicited gently, and that intraneural injections should be avoided.

The blocking effect of epidural analgesia on the adrenocortical and hyperglycemic responses to surgery.

Abstract: The adrenocortical and hyperglycemic responses to hysterectomy were studied in five groups of patients receiving: general anesthesia (group I), general anesthesia + epidural analgesia extending from Th10-S5 (group II), general anesthesia + epidural analgesia extending from Th8-S4--5 (group III), general anesthesia + epidural analgesia extending from Th4--6-S5 (group IV) and epidural analgesia extending from Th4-S5 without general anesthesia (group V). The results showed that the cortisol response was abolished in group V, inhibited in group IV and normal in groups II and III. The hyperglycemic response to surgery was inhibited in groups II, III and IV, and abolished in group V. Epidural analgesia from Th4 to S5, preventing the adrenocortical and hyperglycemic responses to hysterectomy, and possibly also inhibiting other components of the endocrine-metabolic response to surgery, may have important applications in further studies of the physiologic significance of the endocrine-metabolic response to surgery.

Blood Flow in the Rabbit Tracheal Mucosa under Normal Conditions and under the Influence of Tracheal Intubation

Abstract: Isotope labelled microspheres were used to study the capillary blood perfusion of the rabbit tracheal mucosa. Under resting conditions the perfusion was about 0.3 ml/min - g (i.e. about 60% of the relative cerebral blood flow). Irritation of the tracheal mucosa by an endotracheal tube caused a steep rise in blood flow, tenfold or more. This was probably due to relaxation of the arterioles caused by a release of histamine-like substances. When an endotracheal tube is equipped with a small cuff (small resting diameter, low residual volume), the part of the mucosa in contact with the cuff, i.e. the mucosa covering the surface and edges of the cartilages, will be ischaemic at a cuff to tracheal wall pressure (C-T pressure) of greater than 30 millimeters of mercury. This abrupt ischaemia threshold contributes to the risk of deep mucosal damage with subsequent tracheal scarring, possibly proceeding to stenosis. Our present studies indicate that the ideal large cuff, with properties resembling those of an air cushion, will allow the major part of the arterial pressure to be propagated as far down as the capillaries. Under these conditions the cuff would permit some of the capillary blood perfusion of the tracheal mucosa covering the cartilages also at C-T pressures exceeding 30 mmHg. Although this investigation supports the concept that the ideal thin-walled large cuff interferes much less with the mucosal blood perfusion than the small cuff, we recommend that the cuff pressure be monitored and kept below 20 mmHg.

Catheter technique in axillary plexus block. Presentation of a new method.

Abstract: A flexible, disposable intravenous catheter can be introduced into the neuro-vascular sheath in the axilla and used for injection of local anesthetic solution to block the axillary brachial plexus. The technique is described and the results of the first 137 consecutive catheter blocks are reported and compared to a similarly evaluated series of conventional axillary blocks. The catheter method constitutes an interesting alternative to needle techniques and offers the possibility of a continuous axillary block.

Hypoxia-induced vasoconstriction in isolated perfused lungs exposed to injectable or inhalation anesthetics.

Abstract: Investigations during the last two decades have revealed a tendency to impaired pulmonary gas exchange in patients during general anesthesia. In the awake state, arterial hypoxemia is counteracted by a mechanism which tends to normalize the ventilation perfusion ratio of the lungs by way of a hypoxia-induced vasoconstriction in poorly ventilated areas. This results in a redistribution of perfusion to more adequately ventilated lung regions. Recent observations suggest, however, that this beneficial mechanism is blunted by some commonly used inhalation anesthetics. In the present study the effects of inhalation anesthetics and injectable anesthetics on the vasoconstrictor response to acute alveolar hypoxia have been compared in isolated blood-perfused rat lungs. The experiments showed that the response was unaffected by N2O and injectable anesthetics, while a reversible, dose-dependent damping effect was demonstrated for the volatile inhalation anesthetics, ether, halothane and methoxyflurane. The effect could be demonstrated at blood concentrations comparable to those used in clinical anesthesia, and it was not due to a general paralysis of the vascular smooth muscle. The findings might, at least in part, explain the occurrence of arterial hypoxemia during general inhalation anesthesia.

Review of the physiological rationale for and development of high-frequency positive-pressure ventilation--HFPPV.

Abstract: In 1967, a method of artificial positive-pressure ventilation without circulatory effects synchronous with respiration was required for experimental studies and for this purpose high-frequency positive-pressure ventilation (HFPPV) was developed. The original rationale for the HFPPV technique was (a) by means of endotracheal insufflation a reduction in dead space should make it possible, with smaller tidal volumes and higher ventilatory frequencies, to provide adequate alveolar ventilation at lower maximal and lower mean airway pressures than those required in conventional IPPV; (b) under insufflation with a high frequency and a short insufflation period the inertia characteristics of the lungs should be able to achieve critical suppression of the circulatory effects of the ventilatory pattern. In order to compensate for the increased VdVt with intermittent positive-pressure ventilation of high frequency, a ventilator system whose compressible volume and internal compliance were negligible was required. In dog experiments the HFPPV technique was found to provide the anticipated circulatory conditions. In addition it was observed that when air was intermittently supplied by endotracheal insufflation at a frequency of 60–80 per min the spontaneous breathing ceased almost instantaneously. As arterial blood gas analyses verified that this suppression occurred even at normoventilation, it was assumed that it most probably resulted from a suppression of the reflexogenic spontaneous respiratory rhythm. In comparative experimental studies the original expectations were verified, i.e. in normal dogs under general anaesthesia HFPPV gave adequate ventilation with the aid of relatively low transpulmonary pressures and with only slight circulatory or other systemic effects. This HFPPV technique was therefore investigated clinically and in all patients adequate alveolar ventilation was achieved with insufflation frequencies of 60–100 per min and with only small airway pressure variations. A ventilator system for HFPPV in which the insufflation catheter is excluded from the patient circuit was considered. This requires a modified insufflation technique which essentially gives no increase in the compressible volume or internal compliance of the ventilator system, or in the physiological dead space of the patient. A pneumatic valve principle utilizing the Coanda effect was found to fulfil these requirements. The ventilator systems designed according to these principles comprised a gas-conditioning unit and a patient circuit. The gas-conditioning unit supplied gas pressures which remained constant regardless of the ventilatory phase and provided gas mixtures (C2/N2O or O2/air) of desired temperature and relative humidity. The conditioned gas was delivered under high pressure to the side-arm of the pneumatic valve connector of the patient circuit. These new systems for HFPPV were studied in a lung model and dog experiments. They were then applied in clinical practice for bronchoscopy (broncho-scopic HFPPV) and laryngoscopy (laryngoscopy HFPPV) under general anaesthesia and for paediatric anaesthesia and neonatal respiratory care. Owing to their “open” character these ventilator systems and techniques lacked the capacity to give a volume-controlled ventilation. Further technical development was thus motivated, and is the subject of a subsequent article.

The Effects of PaCO2 Reduction on Regional Cerebral Blood Flow in the Acute Phase of Brain Injury

Abstract: In 26 unconscious patients with brain injuries, regional cerebral blood flow (rCBF) was measured with a 16-channel Cerebrograph before and after acute reduction of PaCO2. The intra-arterial 133xenon washout technique was used, and CBF was calculated regionally as initial slope index or stochastic flow. The CO2 reactivity was calculated as deltaln CBV/deltaPaCO2. In supratentorial cortical lesions, an acute fall in PaCO2 increased the homogeneity of the regional flow pattern (decrease in the standard deviation of the regional flow values), and reduced the number of focal hyperaemic regions (tissue peaks). The CO2 reactivity in tissue peak regions was generally higher than in regions without tissue peaks. In severely injured patients with a poor outcome (dementia, vegetative survival or death), inverse steal reaction was accounted for in 11% of all regions, but only in 3% of the regions in patients who survived without dementia. Inverse steal reaction was most frequently seen during the first 3 days after the trauma. In repeated CBF studies, an increase in the CO2 reactivity with time was observed after the acute trauma. In comparison with the CO2 reactivity found in normocapnic awake subjects, this increase was higher than expected in several cases.

Pulmonary Complications, Ventilation and Blood Gases after Upper Abdominal Surgery

Abstract: Forty patients who underwent elective cholecystectomy were examined preoperatively and during the first postoperative week by physical examination, measurement of FVC and FEV1, arterial pH and blood gas analyses, and chest x-ray. Postoperative pulmonary complications (p.p.c.) were detected in 30 (75%) of the patients. Simple auscultation was the most sensitive tool in discovering p.p.c., but 18 of the 30 patients with complications also had a pathological chest x-ray. Obesity, smoking, postoperative naso-gastric tube and postoperative wound infection were predisposing factors for p.p.c. Six patients with preoperative pulmonary disease all had a progress in their lung pathology. There was no definite relationship of duration of anaesthesia or drainage of the abdominal wound to development of p.p.c. The patients with p.p.c. showed a deeper and more prolonged fall in Pao2 postoperatively than the normal group. None of the normals showed an arterial Po2 below 70 mmHg in the postoperative course, while 63% of the p.p.c. group did. FVC and FEV1 showed marked reductions from preoperative values on the first postoperative day, and then gradually increased to near preoperative values after 1 week. Arterial pH and Pco2, showed no definite changes during the postoperative course.

Transplacental passage of ketamine after intravenous administration.

Abstract: This study was designed to measure how fast and at what concentrations ketamine would enter the foeto-placental circulation, when administered intravenously to 10 healthy mothers immediately before forceps delivery, which was indicated by a delayed second stage of labour. It is shown that ketamine very rapidly passes the placenta, and that ketamine levels in cord blood exceed the levels in the maternal venous blood as early as 1 min 37 s after the injection. The ketamine levels in cord blood reach a maximum in the period 1 min 37 s to 2 min 5 s after the injection. Later they show a tendency to decline. A short-lasting, marked elevation of blood pressure was produced by the ketamine anaesthesia. Two of the newborn showed low Apgar scores at 1 min. In one of them this was probably attributable to the anaesthesia.

The cerebrovascular CO2 reactivity during the acute phase of brain injury.

Abstract: Using the intra-arterial 133xenon (133Xe) method, the cerebrovascular response to acute PaCo2 reduction was studied in 26 unconscious, brain-injured patients subjected to controlled ventilation. The CO2 reactivity was calculated as δ In CBF/δ Paco2. The perfusion pressure was defined as the difference between mean arterial pressure and mean intraventricular pressure. Although the CO2 reactivities did not differ significantly from that in awake, normocapnic subjects, it was low in the acute phase of injury, especially in those patients with severe outcome in whom the brain-stem reflexes were often affected. An increase of the CO2 reactivity with time was observed, indicating normal response after 1–2 weeks. Chronic hypocapnia in six unconscious patients resulted in sustained CSF pH adaptation. The question whether a delay in CSF pH adaptation exerts an influence on the CO2 reactivity, and the influence of cerebral lactacidosis on the CO2 response are discussed.

Measurement of Rapid Changes in Cardiac Stroke Volume. An Evaluation of the Impedance Cardiography Method

Abstract: One hundred and twenty-nine simultaneous measurements were carried out on seven patients, 67 at rest and 62 during the Valsalva manoeuvre, in order to compare impedance cardiography with the thermodilution method, during rapid changes in cardiac stroke volume and pulmonary blood volume. A coefficient of correlation of 0.86 was found following linear regression analysis of the whole material. Analysis of the individual patient showed that the mean coefficient of correlation was 0.94 (range 0.91–0.97), and that the slope of the regression lines was 0.41 to 1.82, and further that the mean intercept was 0.2 ml. It is concluded that impedance cardiography can be employed for measuring the relative intraindividual changes in cardiac stroke volume during the Valsalva manoeuvre, and it is suggested that it may be of use in other situations, such as during haemorrhage or continuous positive pressure ventilation.

The different responses of the hepatic arterial bed to hypovolaemia and to halothane anaesthesia.

Abstract: Ten dogs were subjected to a period of hypovolaemia (bleeding volume: 2% of body weight) and to a period of halothane anaesthesia (end-tidal halothane concentration: 1%). Mean arterial blood pressure decreased to 79% of control value during hypovolaemia and to 58% of control value during halothane anaesthesia. Mean total peripheral and preportal vascular resistances increased during hypovolaemia and were unchanged during halothane. Mean hepatic arterial and portal venous blood flows decreased to 82% and 55% of control values, respectively, during hypovolaemia, and to 41% and 56% of control value, respectively, during exposure to halothane. Mean hepatic arterial resistance was unchanged during hypovolaemia, but increased during halothane. Mean hepatic oxygen consumption did not change significantly during hypovolaemia, but decreased during halothane anaesthesia, in spite of an increased extraction of oxygen from both the hepatic arterial and the portal venous blood. Possible mechanisms which may maintain oxygen supply to the liver by increasing the hepatic arterial fraction of total liver blood flow when portal venous blood flow is reduced are discussed. It is concluded that this mechanism is upset or inhibited during halothane anaesthesia.

Respiration, Circulation and Anaesthetic Management in Obesity. Investigation before and after Jejunoileal Bypass

Abstract: Some ventilatory and circulatory parameters were studied in 17 very obese patients before and after weight reduction following jejunoileal bypass A low vital capacity and signs of impaired lung function with intrapulmonary shunting, increased alveolar-arterial Po2 difference and low Pao2 were found Although the spirometric values improved significantly after weight reduction, the ventilatory disturbance persisted A normal response to inhalation of CO2 was seen The total blood volume was high and did not change after weight reduction However, if calculated as blood volume per kg body weight, the values were lower than normal, and they increased as a consequence of weight reduction Cardiac output was slightly lower than normal in relation to oxygen consumption Total peripheral resistance was normal Arterial blood pressure, which was in the high normal range preoperatively, decreased significantly after weight reduction Total doses of intravenous anaesthetic agents and muscle relaxants were the same as for patients of normal weight The importance of preoperative evaluation and of respiratory care of obese patients undergoing elective surgery is stressed

Bupivacaine (Marcaine®): An Evaluation of its Tissue and Systemic Toxicity in Humans

Abstract: In countries other than the U.S.A., dosages of bupivacaine have been limited to 100 mg without epinephrine and 150 mg with epinephrine. A review of 7,688 regional block procedures employing bupivacaine in concentrations of 0.25, 0.5, and 0.75%, and in dosages as high as 600 mg, indicated that such stringent restrictions: (1) are unwarranted, (2) make comparisons with other local anesthetic agents difficult, and (3) are in need of revision.

Long-term treatment of two patients with respiratory insufficiency with IPPV/PEEP and HFPPV/PEEP.

Abstract: The respiratory centre is a multi-input system and positive-pressure ventilation is known to interfere with respiratory control mechanisms. Further, in intermittent positive-pressure ventilation (IPPV) the ventilatory pattern produced by the ventilator and the lung systems is known to influence pulmonary and cardiovascular functions. High-frequency positive-pressure ventilation (HFPPV) has been shown to eliminate respiration-synchronous variations in blood pressure and blood flow, and at frequencies of 60 per min or more spontaneous breathing ceases almost instantaneously if adequate alveolar ventilation and arterial oxygenation are achieved. However, activation of other inputs to the respiratory centre, e.g. chemo-receptor inputs, can induce spontaneous respiration during HFPPV. Consequently the balance between excitatory and inhibitory afferents is decisive for the patient's spontaneous respiratory efforts (discoordination) during artificial ventilation. The balance between excitatory and inhibitory mechanisms during artificial ventilation is illustrated in two patients with pulmonary insufficiency. Both patients exhibited spontaneous respiratory efforts (discoordination) during ventilation with a “conventional” type of respirator (ventilatory frequency 20 per min) despite adequate alveolar ventilation, adequate arterial oxygenation and administration of sedatives and respiratory depressants. During HFPPV, at ventilatory frequencies of 60 per min or more, there was an inhibitory effect on spontaneous respiration, and with adequate alveolar ventilation and adequate arterial oxygenation (obtained at lower inspiratory airway pressures than with a “conventional” type of ventilation) it was possible to discontinue sedatives and respiratory depressants without discoordination occurring between the patient and the ventilator. However, in one of the patients, with decreasing pulmonary compliance and diminishing arterial oxygenation (due to increasing intrapulmonary shunting and cardiac decompensation), spontaneous respiratory efforts were present despite high ventilatory frequencies and administration of sedatives and respiratory depressants. From experimental investigations reported elsewhere, this study in two patients and similar experience in other patients, it seems that it is easier to adapt a patient to a ventilator which has a negligible compression volume and which is set at a high frequency.

Central venous cannulation: A radiological determination of catheter positions and immediate intrathoracic complications.

Abstract: The incidence of immediate complications on inserting central venous catheters into 475 patients is reported. The catheter positions were verified by X-rays. Six different insertion routes were used. Central venous cannulation via the right internal jugular vein is recommended because of the high incidence of satisfactory catheter positions and the small number of puncture complications with this route.

Comparison of the analgesic effects of intravenous nalbuphine and pentazocine in patients with postoperative pain.

Abstract: One hundred patients, who were in pain during the immediate postoperative period after upper abdominal operations, were included in this double-blind, between-patient, two-dose study. During N2O-O2-halothane-relaxant anaesthesia no analgesics were given. The patients received 0.07 mg/kg or 0.14 mg/kg of nalbuphine or 0.3 mg/kg or 0.6 mg/kg of pentazocine by intravenous injection. Pain and side effects were assessed for 4 h after administration of the test drug, or until the pain returned to the pre-injection level, when a conventional analgesic was given. The onset of pain relief was similar and the peak effect occurred about half an hour after the injection after both drugs. On a milligram basis, nalbuphine seemed to be about three times as potent as pentazocine. The duration of action seemed to be slightly longer after nalbuphine, but 2 1/2 hrs. after the injection the pain had returned to preinjection level in 2/3 of the patients, even after the higher doses of both drugs. Except for sleepiness, there were few side effects and they were similar after both drugs. No psychotomimetic effects were observed.

Diazepam and flunitrazepam as induction agents for cardiac surgical operations.

Abstract: Diazepam and flunitrazepam were compared in equipotent doses as induction agents for premedicated patients having cardiac surgery Both drugs caused a significant fall in arterial blood pressure, a rise in Paco2 and a fall in Pao2 There was no significant difference between the two drugs in onset time of anaesthesia, cardiovascular or respiratory depression, or quality of induction There was also no significant difference from induction with thiopentone in these respects Diazepam, over a 02 to 06 mg/kg range of doses showed no difference in toxicity, although induction was clinically smoother with the higher dose

Anaphylactic Shock in the Monkey: its Hemodynamics and Mediators1

Abstract: Anaphylactic shock (AS) was induced in 15 monkeys, and their hemodynamics were studied in order to identify the mechanisms initiating the low cardiac output (CO) state. Further, in 16 monkeys various substances were used with the aim of mimicking or antagonizing the changes in AS. Initial peripheral collapse was indicated by lowering of the right atrial pressure (RAP). The subsequent development of pulmonary hypertension increased RAP and, by extending venous pooling, reduced filling of the left heart. The degree of pulmonary hypertension or arterial hypotension was a poor indicator of the fall in CO. Hypoxemia and dysrythmias occurred occasionally, but early hemoconcentration was not found. Light depression of CO (—42%), due to venous pooling and reduction in left heart filling, could be corrected by fluid administration. In contrast, severe depression of CO (—81%) associated with ST-T depression and with decreased cardiac contractility responded less to the fluid load, suggesting that myocardial failure was partly responsible for the low output state. Inhibition of prostaglandin (PG) synthesis by indomethacin did not prevent the development of AS. Injections of PGE2 and PGF2α, alone or together with histamine (Hi), did not mimic AS. PGE2 induced hypotension accompanied by an increase in CO, and PGF2α induced general vasoconstriction and a somewhat diminished CO. Hi induced hypotension and pulmonary hypertension; CO increased after low doses but decreased after sublethal doses. Compound 48/80, a liberator of Hi and slow-reacting substance (SRS), imitated Hi effects initially, but later mimicked a minor state of AS. Infusion of FPL 55712, a selective antagonist of SRS, prevented AS, and general vasoconstriction occurred instead. In this model of AS, SRS is a more important mediator than Hi or PG.

Experimental and clinical evaluation of high-frequency positive-pressure ventilation (HFPPV) and the pneumatic valve principle in bronchoscopy under general anaesthesia.

Abstract: A technique for automatic ventilation in bronchoscopy under general anaesthesia was evaluated in two types of lung model and in 23 patients (29–70 y) submitted for routine bronchoscopy. The technique uses high-frequency positive-pressure ventilation (HFPPV) and functions with a pneumatic valve derived from the bronchoscope's side-arm. This technique has been given the name bronchoscopic HFPPV. Based on earlier studies, an insufflation frequency (f) of 60 per min and a relative insufflation time (1%) of 22 % was used. In the lung models, the relationship between the total gas input (Vtot) delivered to the side-arm of the bronchoscope and the pressure/gas flow pattern created at the different openings of the bronchoscope was studied. The force created by the pneumatic valve function is regulated by adjustment of Vtot and implies a great ventilatory reserve capacity. No air entrainment occurs through the proximal opening of the bronchoscope, which implies full control of the anaesthetic gas mixture delivered to the patient. Many of the patients were considered to be high anaesthetic risks and in the patient study it is shown that the alveolar ventilation can be fully controlled by adjustment of VTOT and arterial oxygenation by adjustment of the oxygen concentration of the oxygen/nitrous oxide mixture delivered to the side-arm of the bronchoscope. Experimental and clinical evaluation shows that adequate oxygenation and ventilation can be achieved: — (a) over long periods of time, (b) in anaesthetic high risk patients, (c) with the bronchoscope in the main bronchus of the diseased lung, and (d) during instrumentation through the bronchoscope. A simple ventilation-nomogram for clinical use is proposed. Adequately used, this nomogram guarantees safe ventilation during bronchoscopic HFPPV. An FIO2 of 0.3–0.4 gives adequate arterial oxygenation.

Summary of Experimental and Clinical Features of High‐Frequency Positive‐Pressure Ventilation—HFPPV

Abstract: In order to eliminate the respiration-synchronous variations in blood pressure and heart rate a new method of artificial positive-pressure ventilation was developed—high-frequency positive-pressure ventilation (HFPPV). Since 1967 this technique has been applied in various forms and under greatly differing technical and physiological conditions. The ventilatory pattern in intermittent positive-pressure ventilation (IPPV) is the result of the combined conditions created by the ventilator and the pulmonary systems and an obvious controversy between physics and physiology arises in the designing of ventilators to match the breathing patterns and pulmonary and cardiovascular physiology of patients with seriously impaired vital functions. A summary is given of the different types of techniques and the physiological parameters, morphology and functions studied in HFPPV. In order to overcome the increased VD/VT ratio and to provide satisfactory alveolar ventilation in HFPPV, certain basic technical and functional characteristics must be inherent in the ventilator system used. For example in the patient circuit of ventilator systems for HFPPV of an “open” character and for volume-controlled ventilation there is a negligible compression volume. In a ventilator system for volume-controlled ventilation, which has a negligible compression volume, inspiration has a decelerating character and the roles of volume as a primary parameter and pressure as a secondary parameter should theoretically function in a desired manner. The major characteristics of the ventilatory pattern of HFPPV are (a) a ventilatory frequency about three times as high as in conventional IPPV, (b) smaller tidal volumes and lower airway pressures than in conventional IPPV, (c) inspiratory flow (usually of a decelerating character) without an end-inspiratory plateau, (d) positive intratracheal and negative intrapleural pressures throughout the ventilatory cycle (presumably with even and efficient pulmonary gas distribution), (e) less circulatory interference than in conventional IPPV and (f) reflex suppression of spontaneous respiratory rhythmicity at normoventilation. These functional characteristics of artificial ventilation would seem to be of decisive importance for the pulmonary and cardiovascular physiology of patients with seriously impaired vital functions.

Selective lumbar epidural block in labour. A clinical analysis.

Abstract: Segmental epidural analgesia (T10-T12) was performed in 418 parturients, using a 4-6 ml dose of 0.5% bupivacaine, with or without adrenaline. Seventy per cent of parturients were primiparas and 30% had histories, or signs, of possible uteroplacental insufficiency. Our aim was to relieve pain during the long passive opening phase, so that mothers would be rested and active at the beginning of the second phase, but also to avoid abolishing the bearing-down reflex, the absence of which causes an increased frequency of instrumental delivery. The analgesia during the opening phase was of good quality in 89% of primiparas, and 84% of multiparas. The onset of analgesia was rapid (3-5 min) and the duration was on average 2 1/2 h. The incidence of foetal heart rate changes, during the 30 min after epidural, was 5%. The second phase was less than 30 min in about 90% of cases. About 90% of parturients delivered spontaneously, and the frequency of instrument delivery was only 7.4%. Caesarean section was required in 3.7%. Slight, but rapidly correctable, hypotension occurred in 16.5%, and in two cases the hypotension led to more serious complications. This stresses the importance of the availability and competence of both the anaesthetic and obstetric teams. There were no maternal or neonatal mortalities, and the Apgar scores compared well with the figures for the normal material in our obstetric unit.

Human hepatic blood flow and its relation to systemic circulation during intravenous infusion of lidocaine.

Abstract: Twelve healthy young volunteers were studied before and during intravenous administration of lidocaine at a dose rate of 2 or 4 mg/min. Five additional volunteers, who did not receive lidocaine solution but were given the same amount of physiological saline, were studied in the same manner. Heart rate, cardiac output, mean arterial blood pressure, mean right atrial blood pressure, estimated hepatic blood flow and plasma concentration of lidocaine were measured repeatedly. The results showed an increase in heart rate, cardiac output and mean arterial blood pressure, the latter two variables in relation to the plasma concentration of lidocaine. The estimated hepatic blood flow increased, partly as a result of the reduction of splanchnic vascular resistance and partly due to the stimulation of cardiac output. The decrease in splanchnic vascular resistance was proportional to the plasma concentration of lidocaine.

Parenteral Use of Diazepam in an Emulsion Formulation. A Clinical Study

Abstract: A recently described injection formulation for diazepam, consisting of an oil emulsion where the drug is dissolved in the oil phase, has been found to give a lessened degree of side reactions than commercially available preparations. This emulsion formulation was compared to Valium inj. as premedication in patients undergoing operation for hernia or varices under epidural anaesthesia. The effects, measured as the degree of drowsiness according to an arbitrary scale, were found to be equal for the two formulations. Neither was there any difference in blood concentrations in the two application groups, respectively, between the preparations used. The propylene glycol content of Valium inj. is said to cause a delayed release of the drug from the injection site after i.m. application, and this is briefly discussed, as well as the possibility of administering the diazepam emulsion continuously, diluted with Intralipid, without the risk of precipitation.

Phrenic and Vagal Nerve Activities during Spontaneous Respiration and Positive-Pressure Ventilation

Abstract: Afferent vagal nerve activity from stretch-receptors in the lung and efferent phrenic nerve activity were recorded during spontaneous respiration and during positive-pressure ventilation with three different types of ventilators. During spontaneous respiration the efferent phrenic nerve activity slightly preceded the afferent vagal nerve activity. Volume-controlled ventilation did not alter the phrenic nerve activity when the ventilation was set at a rate equal to that during spontaneous respiration, but afferent vagal volleys increased in duration. At higher frequencies of insufflation spontaneous inspiration was inhibited. An increase in afferent vagal nerve activity and a concomitant slight decrease in efferent phrenic nerve activity were obtained during animal triggered pressure-controlled ventilation. High-frequency positive-pressure ventilation (HFPPV) gave rise to basal, non-grouped activity in vagal afferents, causing inhibition of inspiration. During HFPPV, spontaneous respiration can take place on activation of other afferents to the respiratory centre. Clinical aspects of respirator treatment from a neurophysiological standpoint are discussed.

Anaphylactoid reaction to dextran---a report of 133 cases.

Abstract: From 1968 to 1975, the Swedish Adverse Drug Reaction Committee received 113 reports on anaphylactoid reaction to dextran 70, and 20 reports on the same reaction to dextran 40. For 1975, this would equal a reported incidence of anaphylactoid reaction to dextran 70 of 1:2,500. The median age of patients reacting to dextran 70 was 63 years. Median age increased with increasing severity of the anaphylactoid reaction: from 48 years in patients with skin symptoms predominantly, to 79 years in the five patients who died. Symptoms were noticed within 10 min of the start of the infusion, or before 100 ml had been infused in 96 patients (85%) with an anaphylactoid reaction to dextran 70. There was a tendency for severe reactions to be observed earlier than milder ones. Symptoms also tended to be observed earlier in conscious than in unconscious patients. Reactions reported to have occurred in unconscious patients tended to be more severe than those in conscious patients. Patients with anaphylactoid reaction to dextran 40 did not differ from those with reactions to dextran 70 with regard to age, severity of the reaction or time before onset of symptoms. There was one death in this group.

Human hepatic blood flow and its relation to systemic circulation during intravenous infusion of bupivacaine or etidocaine.

Abstract: Fifteen healthy young volunteers were studied before and during an intravenous infusion of a local anaesthetic agent. Seven received bupivacaine and eight etidocaine in a dose rate of 2 mg/min over a period of 150 min. Variables of the central systemic circulation and also the hepatic blood flow were measured repeatedly. The circulatory alterations during administration of the two drug s were compared. Comparisons with previous results concerning lidocaine and a placebo were also made. It was found that bupivacaine increased the heart rate, mean arterial blood pressure and cardiac output significantly more than did etidocaine in an equal plasma concentration. Lidocaine was intermediate between bupivacaine and etidocaine. In contrast, these three drugs had the same decreasing effect upon the splanchnic vascular resistance, which caused an almost identical increase in the estimated hepatic blood flow. The calculated vascular resistance in the systemic circulation, excluding the splanchnic, was unchanged during the infusion of etidocaine, while it decreased during the infusion of bupivacaine. Most of this discrepancy was due to the different plasma concentrations of the drugs.

The cardiovascular effects of neuroleptanaesthesia.

Abstract: Oxygen uptake, cardiac output, stroke volume and arterial and central blood pressures were measured before and after induction of neuroleptanaesthesia in 27 subjects. Nine were elderly patients operated on for obliterative arteriosclerotic disease, and the other 18—nine elderly and nine younger patients—underwent operation for varicose veins. Cardiac output, stroke volume and systolic arterial blood pressure decreased significantly with a corresponding decrease in oxygen uptake. The changes were most pronounced in the patients with arteriosclerotic disease. The arterio-venous oxygen difference was unchanged in the arteriosclerotics and decreased in the other two groups. The central pressures remained unchanged in all groups. It is concluded that the cardiovascular changes induced by neuroleptanaesthesia are due to a decrease in oxygen uptake and not to myocardial depression.

The Influence of the Ventilatory Pattern on Ventilation, Circulation and Oxygen Transport during Continuous Positive-Pressure Ventilation An Experimental Study

Abstract: In IPPV, the ventilatory pattern produced by the ventilator and the lung systems is known to influence pulmonary and cardiovascular functions. In this study on dogs the ventilatory pattern of a conventional respirator (Siemens-Elema Servo Ventilator 900=SV-900) constituted the norm for comparison with that produced by a system for volume-controlled HFPPV. The experimental conditions were kept identical (pentobarbital anaesthesia and normoventilation, i.e. arterial PCO2=40 mm Hg, pH=7.4 and constant FIO2 of the inspired air). At comparable alveolar ventilation the intratracheal peak and mean pressures were always higher during ventilation with SV-900 than during HFPPV. The calculated alveolar oxygen partial pressure (PAO2) was almost identical with the two systems. The differences in arterial PCO2 and PO2 between SV-900 and HFPPV were negligible when 30% O2 was used. The total peripheral resistance (TPR) was lower during ventilation with HFPPV, and although the cardiac output (CO) and stroke volume (SV) were greater during HFPPV, calculations of the tension-time index (TTI) revealed no differences between the two ventilator systems. With 30% O2 the alveolo-arterial PO2 difference (A-aDO2) was smaller, the oxygen flux (OF) greater and the venous admixture lower during ventilation with HFPPV. The lower TPR during ventilation with HFPPV in association with a higher cardiac output and improved tissue perfusion indicates that the ventilatory pattern in volume-controlled HFPPV interferes less with the cardiovascular functions. Thus, HFPPV appears able to give better myocardial and circulatory efficiency.

Psychological changes in children after anaesthesia: a comparison between halothane and ketamine.

Abstract: The psychological reactions to hospitalization, anaesthesia, and operation in a group of 107 children from 1 to 12 years old, anaesthetized with ketamine or halothane after randomization were investigated through questionnaires, which the parents answered 1 month postoperatively. The percentage of replies was 96.3%. Fifty-three children were anaesthetized with ketamine and 50 with halothane. Thirteen children in the ketamine group and nine in the halothane group reacted with negative personality changes; the reactions were of less than 1 month's duration and were most frequent in the youngest children. The parents' preparation of the children had no influence on the results. The number of personality changes caused by the two anaesthetic agents did not differ significantly. Furthermore, the investigation showed that nine children reacted for the better. Thirty-six per cent of the parents felt insufficiently informed of what the hospitalization implied for their child.