Björn Biber

Signs of myocardial ischaemia after injection of oxytocin: a randomized double-blind comparison of oxytocin and methylergometrine during Caesarean section

BACKGROUND ECG changes, similar to those seen during myocardial ischaemia, together with symptoms of chest pain, are common during Caesarean section (CS). We hypothesized that oxytocin administration has cardiovascular effects leading to these symptoms and ECG changes. METHODS Forty women undergoing elective CS under spinal anaesthesia were given an i.v. bolus of either 10 IU of oxytocin (Group OXY-CS, n=20) or 0.2 mg of methylergometrine (Group MET-CS, n=20), in a double-blind, randomized fashion after delivery. Ten healthy, non-pregnant, non-anaesthetized women were used as normal controls (Group OXY-NC, n=10) and were given 10 IU of oxytocin i.v. Twelve-lead ECG, on-line, computerized vectorcardiography (VCG), and invasive arterial pressure were recorded. RESULTS Oxytocin produced a significant increase in heart rate, +28 (SD 4) and +52 (3) beats min(-1) [mean (SEM); P<0.001], decreases in mean arterial pressure, -33 (2) and -30 (3) mm Hg (P<0.001), and increases in the spatial ST-change vector magnitude (STC-VM), +77 (12) and +114 (8) microV (P<0.001), in CS patients and controls, respectively. Symptoms of chest pain and subjective discomfort were simultaneously present. Methylergometrine produced mild hypertension and no significant ECG changes. CONCLUSIONS Oxytocin administered as an i.v. bolus of 10 IU induces chest pain, transient profound tachycardia, hypotension, and concomitant signs of myocardial ischaemia according to marked ECG and STC-VM changes. The effects are related to oxytocin administration and not to pregnancy, surgical procedure, delivery, or sympathetic block from spinal anaesthesia.

Gabapentin in traumatic nerve injury pain: A randomized, double-blind, placebo-controlled, cross-over, multi-center study

&NA; A double‐blind, randomized, placebo‐controlled cross‐over multi‐center study was conducted to evaluate the efficacy and safety of gabapentin in the treatment of neuropathic pain caused by traumatic or postsurgical peripheral nerve injury, using doses up to 2400 mg/day. The study comprised a run‐in period of two weeks, two treatment periods of five weeks separated by a three weeks’ washout period. The primary efficacy variable was the change in the mean pain intensity score from baseline to the last week of treatment. Other variables included pain relief, health related quality of life (SF‐36), interference of sleep by pain, Clinician and Patient Global Impression of Change, and adverse effects. Nine centers randomized a total of 120 patients, 22 of whom withdrew. There was no statistically significant difference between the treatments for the primary outcome efficacy variable. However, gabapentin provided significantly better pain relief (p = 0.015) compared with placebo. More patients had at least a 30% pain reduction with gabapentin compared with placebo (p = 0.040) and pain interfered significantly less with sleep during gabapentin treatment compared with placebo (p = 0.0016). Both the Patient (p = 0.023) and Clinician (p = 0.037) Global Impression of Change indicated a better response with gabapentin compared with placebo. Gabapentin was well tolerated. The most common adverse effects were dizziness and tiredness.

PORTAL BLOOD FLOW IN MAN DURING GRADED POSITIVE END – EXPIRATORY PRESSURE VENTILATION

The cardiovascular response to graded PEEP ventilation (5–10 cm H2O) was studied peroperatively in patients undergoing chllecystectomy (n=8) or hepatic tumour surgery (n=3). Portal blood flow was measured by the continuous thermodilution technique and cardiac output, in a sub-group of the patients, by impedance cardiography. A parallel reduction in cardiac output and portal blood flow was demonstrated in patients undergoing cholecystectomy as the result of the application of PEEP. Thus, ventilation with 5 cm H2O of PEEP elicited a 17% decrease in cardiac output and a 26% decrease in portal blood flow. During 10 cm H2O of PEEP cardiac output decreased by 22% and portal blood flow by 32%. However, there were no significant changes in preportal tissue perfusion pressure by the application of PEEP and preportal vascular resistance increased by 22% and 30%, respectively. This indicates that a vasoconstrictor response, elicited by PEEP, in the preportal tissue is the predominating mechanism for the observed decrease in portal blood flow. Systemic oxygen transport decreased by 214 ml/min during PEEP ventilation, but preportal tissue oxygen utilization was not significantly changed due to a concurrent increase (2.9%; p<0.05) in oxygen extraction.

Continuous interscalene brachial plexus block for postoperative analgesia following shoulder surgery

Background: Severe postoperative pain is a well‐known problem following shoulder surgery. This study evaluates the clinical efficacy of continuous interscalene brachial plexus block, patient‐controlled analgesia, and morphine (i.v. and i.m.) for postoperative analgesia in this setting.

Measurement of Cardiac Stroke Volume During Cesarean Section: A Comparison Between Impedance Cardiography and the Dye Dilution Technique

Simultaneous determination of cardiac stroke volume by impedance cardiography and the dye dilution technique was compared in ten women undergoing elective cesarean section performed under general or epidural anesthesia. The influence of delivery and the anesthetic procedures used on stroke volume determination by the two methods was evaluated and compared. The correlation coefficients for measurements performed before and during anesthesia showed little variation and were largely unchanged after delivery of the child (r = 0.90‐0.97). Mean stroke volume determined by impedance cardiography was significantly (P<0.001) lower than mean stroke volume calculated from the dye dilution technique. However, there was no significant difference between the mean change in stroke volume determined by the two techniques during serial measurements. Impedance cardiography was found to be a safe, reliable, non‐invasive technique for the measurement of changes in stroke volume during cesarean section. The ability of the impedance method to determine changes in stroke volume was unaffected by the anesthetic procedures employed or by delivery of the child.

Naloxone and Ouabain in Ultralow Concentrations Restore Na+/K+-ATPase and Cytoskeleton in Lipopolysaccharide-treated Astrocytes.

Astrocytes respond to inflammatory stimuli and may be important modulators of the inflammatory response in the nervous system. This study aimed first to assess how astrocytes in primary culture behave in response to inflammatory stimuli concerning intracellular Ca2+ responses, expression of Toll-like receptor 4 (TLR4), Na+/K+-ATPase, actin filament organization, and expression of cytokines. In a cell culture model with lipopolysaccharide (LPS), astrocyte response was assessed first in the acute phase and then after incubation with LPS for 1–48 h. The concentration curve for LPS-stimulated Ca2+ responses was bell-shaped, and the astrocytes expressed TLR4, which detects LPS and evokes intracellular Ca2+ transients. After a long incubation with LPS, TLR4 was up-regulated, LPS-evoked Ca2+ transients were expressed as oscillations, Na+/K+-ATPase was down-regulated, and the actin filaments were disorganized. Interleukin-1β (IL-1β) release was increased after 24 h in LPS. A second aim was to try to restore the LPS-induced changes in astrocytes with substances that may have dose-dependent anti-inflammatory properties. Naloxone and ouabain were tested separately in ultralow or high concentrations. Both substances evoked intracellular Ca2+ transients for all of the concentrations from 10−15 up to 10−4 m. Neither substance blocked the TLR4-evoked Ca2+ responses. Naloxone and ouabain prevented the LPS-induced down-regulation of Na+/K+-ATPase and restored the actin filaments. Ouabain, in addition, reduced the IL-1β release from reactive astrocytes. Notably, ultralow concentrations (10−12 m) of naloxone and ouabain showed these qualities. Ouabain seems to be more potent in these effects of the two tested substances.

The effects of propofol, methohexitone and isoflurane on the baroreceptor reflex in the cat

The effects of propofol (P), methohexitone (M) and isoflurane (I) on the baroreceptor reflex were studied in a cat model in which the blood pressure in a bilateral isolated carotid sinus preparation was artificially varied between 50–200 mmHg. The influence from aortic and cardiopulmonary baroreceptors was excluded by vagotomy. With basal chloralose anaesthesia as control, the investigated anaesthetics were used in doses corresponding to MAC 0.5 and 1.0. The maximum change in systemic mean arterial pressure (MAP) and heart rate (HR) following a defined increase in carotid sinus pressure was used as an index of baroreceptor reflex sensitivity. Compared to control, M and I anaesthesia were associated with significant depression of baroreceptor reflex sensitivity at the high dose (corresponding to MAC 1.0), and during I anaesthesia also at the low dose (MAC 0.5). The baroreceptor reflex sensitivity was maintained during propofol anaesthesia. The carotid sinus pressure interval at which the maximum changes in MAP could be elicited, was significantly higher during M than during P. This indicates resetting of the baroreflex.

Glial cell line-derived neurotrophic factor is increased in cerebrospinal fluid but decreased in blood during long-term pain.

Glial cell line-derived neurotrophic factor (GDNF) is involved in inflammation and pain, roles which remain to be delineated clinically. We aimed to evaluate the role of central nervous and peripheral GDNF in long-term pain patients and in controls by analysing intrathecal and blood concentrations of GDNF. Simultaneous measurements of pro-inflammatory cytokines IL-1beta, TNF-alpha and IL-6, anti-inflammatory cytokine IL-10 and chemokine IL-8 served to define inflammatory responses. Generally, blood levels of GDNF were higher than corresponding intrathecal levels. Pain was associated with levels of GDNF that were increased intrathecally, but decreased in blood. IL-8 was uniformly higher in pain patients.

Intravenous Infusion of Halothane Dissolved in Fat. Haemodynamic Effects in Dogs

Eight harrier dogs received an i.v. infusion of halothane dissolved 1:9 in a fat emulsion for i.v. nutrition (Intralipidr̀, Vitrum). The rate of infusion was adjusted to maintain end‐tidal halothane concentrations of 0.7% and 1.4%. At 1.4%, mean arterial pressure decreased to 76 ± 8 mmHg (10.1 ± 1.0 kPa) (mean ± s.e.mean) from a pre‐infusion value of 122 ± 6 mmHg (16.2 ± 0.8 kPa) (P<0.01). The concomitant decrease in cardiac output was 39% and left ventricular maximum dp/dt decreased by 50% (P<0.01). Changes in systemic vascular resistance and pulmonary arterial pressure were small. The haemodynamic responses during halothane inhalation, to corresponding end‐tidal concentrations, were similar. Arterial and mixed venous halothane concentration increased in proportion to end‐tidal concentration. There were no changes in arterial Po2 during the halothane‐in‐fat infusion. Triglyceride concentrations in plasma increased 12‐fold. Haemodynamic recovery after the infusion was fast. We conclude that the halothane‐in‐fat infusion caused a dose‐dependent depression of myocardial contractility and arterial pressure, similar to that seen during inhalation, and that end‐tidal concentration could be used for control of the infusion rate.

The continuous thermodilution method for measuring high blood flows

The continuous thermodilution method for the measurement of blood flow from 300 to 1500 ml/min was evaluated in vitro and in vivo. In vitro experiments indicated that thermotransport within the catheter, causing a temperature measurement error, can occur. Flow model measurements were used for consequent modification of the original thermodilution formula for calculation of flow. In the in vivo investigations the thermodilution and electromagnetic methods were compared for measurement of pig portal blood flow. Using the modified formula for the flow calculations, good agreement was found between the two methods (r = 0.958). For the continuous thermodilution method in vivo the standard deviation of a single measurement was 19 ml/min and the coefficient of variation 1.6%.