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Biomedical subjects

L Heytens

Publications and source records attributed to L Heytens.

At least 37 records · Page 2Linked to original sources
PubMed1992

In vitro diagnosis of malignant hyperthermia: influence of electrical stimulation on the contracture response to caffeine.

We have examined the influence of electrical stimulation on caffeine-induced tension generation during contracture testing used to diagnose malignant hyperthermia. The cumulative contracture response to caffeine was compared in pairs of morphologically comparable muscle bundles obtained from the same patient. Only one of the two bundles was stimulated electrically during the test. Statistically significant differences in tension were found at caffeine concentrations greater than or equal to 4 mmol litre-1, the tension developed being invariably larger in the unstimulated fascicles. These results suggest that electrical stimulation results in suppression of the dose-dependent, caffeine-induced contracture. This effect could be a result of the potentiation of twitch tension by caffeine, muscle fatigue, or both. Overall, the observed differences did not alter the in vitro diagnosis of malignant hyperthermia.

Caffeine↗
PubMed1992

Postpartum dissecting aneurysm of the basilar artery.

BACKGROUND AND PURPOSE: Dissecting aneurysms arising from the vertebrobasilar complex are rare and difficult to manage. More of their natural history needs to be known before treatment can be optimized. CASE DESCRIPTION: We report a postpartum dissecting aneurysm of the right vertebrobasilar artery in a 31-year-old woman that was confirmed by angiographic identification of a double lumen. The intracranial segment of the right vertebral artery was thrombosed proximal to the aneurysm. The patient, managed conservatively, recovered well and, when reexamined 2 months later, was found to be neurologically intact. A repeat angiographic study at that time demonstrated that the aneurysm had resolved. CONCLUSIONS: Proximal occlusion may have protected the aneurysm from rupture and further dissection, thereby making surgery unnecessary.

Adult↗
PubMed1991

The caffeine contracture test for malignant hyperthermia: caffeine citrate, caffeine benzoate or caffeine free base?

The aim of the present study was to investigate whether the three different caffeine preparations--caffeine citrate, caffeine benzoate and the free base--used for in vitro diagnosis of malignant hyperthermia susceptibility--produced the same amount of contracture in rat diaphragm. At equimolar caffeine concentrations, the pure base generated more tension in the rat diaphragm muscle than caffeine benzoate or caffeine citrate. The citrate lowers the pH and the free Ca2+ concentration of the test bath and thus suppresses the caffeine contracture. The benzoate is believed to inhibit the caffeine contracture by its carbonyl group in a way similar to the effect of benzocaine.

Animals↗
PubMed1991

Haemodynamic monitoring. Problems, pitfalls and practical solutions.

The synthesis of adenosine triphosphate (ATP) depends on the coordinated interaction of oxygen delivery and glucose breakdown in the Krebs cycle. Cellular oxygen depots are non-existent, therefore the peripheral cells are totally dependent on the circulation for sufficient oxygen delivery. Shock is the clinical manifestation of cellular oxygen craving. The commonly measured variables--blood pressure, heart rate, urinary output, cardiac output and systemic vascular resistance--are not sensitive or accurate enough to warn of impending death in acutely ill patients nor are they appropriate for monitoring therapy. Calculated oxygen transport and oxygen consumption parameters provide the best available measures of functional adequacy of both circulation and metabolism. In order to optimise oxygen delivery (DO2), 4 interacting factors must be taken into account: cardiac output, blood haemoglobin content, haemoglobin oxygen saturation and avidity of oxygen binding to haemoglobin. For viscosity reasons, the optimal haemoglobin concentration is in the vicinity of 90 to 100 g/L, but for optimising the oxygen transport 100 to 115 g/L or a haematocrit of 30 to 35% seems better. The p50 (the pO2 at which haemoglobin is 50% saturated) describes the oxygen-haemoglobin dissociation curve; normally its value is +/- 27 mm Hg. It can be influenced by attaining normal body temperature, pH, pCO2 and serum phosphorous levels. In order to obtain an arterial blood saturation (SaO2) of more than 90% with acceptable haemodynamics, the ventilation mode and inspired oxygen fraction (FiO2) must be adapted; care must be taken not to stress the labile circulation with haemodynamic compromising ventilation techniques [e.g. high positive end expiratory pressure (PEEP) levels, inverse-ratio ventilation, etc.]. The factor most amenable to manipulation is the cardiac output, with its 4 determinants--preload, afterload, contractility and heart rate. In daily clinical practice, heart rate should be between 80 and 120 beats/min; small variations are acceptable. Important deviations must be treated by chemically [isoprenaline (isoproterenol)] or electrically (pacing techniques) accelerating the heart, or with the different antiarrhythmic drugs. A wide variety of agents is available to decrease the preload: diuretics [especially furosemide (frusemide)], venodilators like nitroglycerin (glyceryl trinitrate), isosorbide dinitrate (sorbide nitrate) and sodium nitroprusside, ACE inhibitors, phlebotomy, and haemofiltration techniques (peritoneal or haemodialysis, continuous arteriovenous haemofiltration). To increase the preload, volume loading using a rigid protocol ('rule of 7 and 3'), preferably with colloids, or vasopressor agents [norepinephrine (noradrenaline), epinephrine (adrenaline), dopamine] are useful. Arterial vasopressors are needed to improve perfusion pressure of 'critical' (coronary and cerebral) arteries. Afterload can be decreased by arterial vasodilators. Predominantly arterial dilators are hydralazine and clonidine, while sodium nitroprusside, nitroglycerin and isosorbide dinitrate have combined arterial and venous dilating actions.(ABSTRACT TRUNCATED AT 400 WORDS)

Blood Glucose↗
PubMed1990

Differential diagnosis of MH.

The clinical diagnosis of Malignant Hyperthermia, especially when made early in the course of the crisis, can be difficult as the symptoms are nonspecific at this stage. Furthermore, some other conditions can mimic Malignant Hyperthermia to a certain extent. Several patients who were referred to our institution because of a clinical suspicion of Malignant Hyperthermia but proved to be non-susceptible by in-vitro contracture testing are presented. These cases illustrate the most common differential diagnostic problems that are encountered and emphasize the particular value of the in-vitro contracture test.

Adult↗
PubMed1989

Lazarus sign and extensor posturing in a brain-dead patient. Case report.

A man was declared brain dead after having sustained a gunshot wound to the head. All clinical criteria for the diagnosis of brain death were met. The electroencephalogram was isoelectric, and four-vessel angiography demonstrated the absence of cerebral blood flow. However, stereotypic spontaneous movements were observed which persisted for several hours. The possible mechanism is discussed and a short review of the literature is given.

Brain Death↗
PubMed1988

Peliosis hepatis associated with liver and retroperitoneal abscesses.

A 33-year-old woman was admitted because of coma and severe shock. CT-scan of the abdomen showed the presence of multiple liver abscesses associated with a retroperitoneal abscess which were drained percutaneously. A liver biopsy showed diffuse peliosis. After resolution of the abscesses the patient's general condition improved and she could be discharged from hospital. Peliosis hepatis is an uncommon disorder characterized by dilated sinusoids with formation of blood lakes. Many pathogenetic mechanisms and causal agents have been proposed. Liver biopsy is necessary to establish diagnosis. By withdrawing the offending drug or treatment of the underlying disorder, regression may be observed.

Abscess↗
PubMed1988

Current management of traumatic chylothorax.

The development of a traumatic chylothorax is an uncommon but serious clinical entity. Two cases of traumatic chylothorax are reported. The anatomy and physiology of the thoracic duct and the etiology, diagnosis and management of traumatic chylothorax are discussed.

Adult↗
PubMed1987

Extradural analgesia during labour using alfentanil.

Sixteen primiparous patients requesting pain relief during labour received a continuous infusion of alfentanil 30 micrograms kg-1 h-1 via an extradural catheter. Supplementary (extradural) bolus doses (30 micrograms kg-1) were administered when deemed necessary. Excellent pain relief was rapidly obtained early in labour in all patients. However, analgesia was inadequate in the latter part of stage I and during the second stage in five of the 16 patients--notwithstanding several additional doses of alfentanil, and bupivacaine had to be administered. No serious maternal side-effects, except nausea, were encountered. Although all neonatal Apgar scores were between 7 and 10, the Amiel-Tison test clearly indicated the existence of neonatal hypotonia. The continuous extradural administration of alfentanil proved to be unsatisfactory for pain relief in labour.

Adult↗
PubMed1987

Effects of etomidate on ovarian steroidogenesis.

The present study investigated the influence of two i.v. induction agents, etomidate (0.25 mg/kg) and thiopental (4 mg/kg) followed by isofluorane anaesthesia on the venous blood concentrations of prolactin (PRL), follicle-stimulating hormone (FSH), 17 beta-oestradiol (E2), progesterone (P), 17OH-progesterone (17OH-P) and testosterone (T) in 18 patients during laparoscopy for oocyte aspiration for in-vitro fertilization. A sharp decrease in the plasma concentration of E2 (P less than 0.01), P (P less than 0.01), 17OH-P (P less than 0.01) and T (P less than 0.01) was observed within 10 min after induction of anaesthesia with etomidate, followed by a gradual return to the baseline levels thereafter. No such decrease was noted after the administration of thiopental. These findings suggest that etomidate, which has previously been reported to inhibit adrenocortical steroidogenesis, can also interfere with the endocrine function of the ovary.

17-alpha-Hydroxyprogesterone↗
PubMed1986

Pharmacokinetics and placental transfer of intravenous and epidural alfentanil in parturient women.

Alfentanil was administered as a 30 micrograms/kg single intravenous injection to five healthy women scheduled for elective cesarean section (group A). In five pregnant women normal vaginal delivery was supported by epidural analgesia with a 30 micrograms/kg loading dose followed by a 30 micrograms/kg-1/hr-1 infusion of alfentanil (group B). Five healthy nonpregnant women scheduled for minor general surgery received 120 micrograms/kg alfentanil intravenously as a bolus before surgical incision (group C). In groups A and B plasma alfentanil concentrations, alfentanil plasma protein binding, and alpha 1-acid glycoprotein (alpha 1-AGP) concentrations were measured in maternal and umbilical arterial or venous blood samples at delivery. Multiple arterial sampling in groups A and C for measurement of alfentanil plasma concentration decay analysis indicated three-compartmental characteristics in most patients. In the pregnant population terminal half-life (t1/2 beta), volume of distribution at steady state (Vdss), and total plasma clearance (Clp) amounted to 103 +/- 67 min, 541 +/- 155 ml/kg and 6.48 +/- 0.85 ml/kg-1/min-1, respectively (mean +/- SD), and did not differ significantly in nonpregnant patients. In groups A and B the fetal-maternal ratios indicated a concentration gradient for the total plasma alfentanil content (ratio of total alfentanil concentrations in umbilical venous and maternal blood (Uv/M), 0.31 +/- 0.08 and 0.28 +/- 0.06 (mean +/- SD) in groups A and B respectively) with a larger protein binding capacity in maternal plasma (group A, 85 +/- 3%; group B, 90 +/- 1%) (mean +/- SD).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1986

Maternal and neonatal death associated with Eisenmenger's syndrome.

Pregnancy in patients with Eisenmenger's syndrome is known to be associated with a high incidence of maternal and perinatal death. Complications can occur before and during parturition but are most hazardous in the early postpartum period. If the exact causes of maternal death remain in most instances unknown, hypovolemia with augmented pulmonary to systemic shunt, thromboembolism and cardiac arrythmias are often mentioned as the primary causes of mortality. We report the unsuccessful management of a pregnant patient with Eisenmenger's disease despite all possible precautions as reported in the literature had been taken. We discuss these precautions and more specifically the type of anesthesia that is best given, the prophylactic methods of anticoagulation and the benefit of monitoring techniques in the management of such complex pathologies.

Adult↗
PubMed1985

Ciramadol. The therapeutic dose range during balanced anesthesia.

In this study we attempted to determine whether ciramadol, a mixed opioid agonist-antagonist, would provide a satisfactory analgesic supplementation to an anesthetic technique for major surgery. Fourteen surgical patients received a balanced anesthesia technique with nitrous oxide, oxygen and muscle relaxants following thiopental induction. Incremental doses of ciramadol were administered as indicated by the somatic, hemodynamic or other sympathetic responses to anesthetic and surgical stimulations. The mean requirements of ciramadol during surgery were inferred from each patient's time-dose curve. The mean loading dose of ciramadol needed was 2.5 +/- 0.4 mg/kg and for maintenance of the analgesic effects, ciramadol had to be administered at a rate of 0.41 +/- 0.09 mg/kg.h. The important transformation rate (50.4%/h) was suggestive of an analgetic ceiling effect. Despite the very large amounts of ciramadol given, the hemodynamic responses to noxious stimuli were not fully suppressed with hypertensive episodes occurring during surgery. Recovery of spontaneous ventilation appeared promptly after completion of surgery and no evidence of respiratory depression was seen. Minute ventilation, respiratory rate and arterial PaCO2 remained within normal limits up to two hours after the end of anesthesia. No incidence of adverse psychotomimetic effects was observed.

Adult↗
PubMed1985

Ciramadol as analgesic adjunct to anesthesia in short surgical procedures.

The present study was undertaken to assess the intensity and duration of analgesic effect of ciramadol during induction and maintenance of general anesthesia for short surgical procedures. Sixty female patients received either ciramadol 2 mg.kg-1 or saline before anesthesia induction with thiopental-succinylcholine followed by enflurane maintenance. The changes in heart rate following intubation and surgical incision were partially obtunded by ciramadol pretreatment but mean arterial pressure remained significantly elevated till 6 min. post surgical incision. No evidence of impairment of the spontaneous ventilation was observed even when enflurane anesthesia was added. Addition of enflurane also had no deleterious effects on the cardiovascular performance in the ciramadol treatment group. In the absence of pretreatment with ciramadol, the higher concentrations of enflurane needed induced a significantly lower blood pressure but the rise in heart rate observed remained notably larger than in the ciramadol group. This was accompanied by a reduction of spontaneous ventilation as evidenced by the decrease of minute volume. With both techniques end-tidal carbon dioxide tensions rose to the same extent. Maintenance of adequate anesthesia required a larger amount of enflurane in the non-pretreated group. This could indicate an anesthesia sparing effect of ciramadol.

Adult↗
PubMed1984

Pulmonary edema during cesarean section related to the use of oxytocic drugs.

We report the case of an acute pulmonary edema occurring during cesarean section under general anesthesia in a previously healthy negro parturient. This acute event was probably due to the hemodynamic effects of three oxytocic drugs, oxytocin, methylergometrine maleate and prostaglandin F2 alpha used to control severe third-stage bleeding in interaction with the hemodynamic effects of pregnancy at term and surgical and anesthetic stress. The cardiovascular effects of these drugs are reviewed. For a safer conduct of anesthesia, oxytocin for control of uterine bleeding is recommended to be administered by slow intravenous drip and ergometrin by intramuscular injection. The safety of the intramyometrial injection of PGF2 a still remains to be proven.

Adult↗