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Biomedical subjects

Q H Hogan

Publications and source records attributed to Q H Hogan.

32 records · Page 2Linked to original sources
PubMed1993

Effects of epidural and systemic lidocaine on sympathetic activity and mesenteric circulation in rabbits.

BACKGROUND: The mechanisms producing hemodynamic changes during epidural anesthesia are incompletely understood. This study examines the sympathetic block and splanchnic venodilatation that result from extensive thoracolumbar epidural anesthesia in rabbits using direct measurements of sympathetic efferent nerve activity (SENA) and mesenteric vein diameter (VD). METHODS: Epidural catheters were inserted in rabbits anesthetized with alpha-chloralose, paralyzed with vecuronium, and receiving mechanical ventilation. Arterial pressure was monitored with a femoral cannula, heart rate was determined from the pressure signal, SENA was measured from a postganglionic splanchnic nerve, and VD was measured from segments of ileum externalized in situ. Epidural anesthesia was induced with 0.4 ml/kg lidocaine, using concentrations of either 0.5, 1, or 1.5%. Control animals received intramuscular lidocaine in a dose of either 6 or 15 mg/kg. After recovery from epidural anesthesia, complete sympathetic blockade was induced by systemic administration of the ganglionic blocker hexamethonium (HX). Individual groups included from five to eight animals. RESULTS: A mild decrease in arterial pressure and SENA followed the larger dose of intramuscular lidocaine, but no changes occurred in VD in the control animals exposed to systemic lidocaine at levels comparable to that in the epidural groups (0.96-3.58 micrograms/ml). Epidural injectate extended from T2 to L5. All concentrations of epidural lidocaine produced comparable degrees of hypotension (-53.5 to -61.4%), decreased SENA (-82.6 to -95.5%), and increased VD (7.5 to 10.2%). The duration of the changes was greater with more concentrated lidocaine. Hexamethonium produced changes in arterial pressure and VD comparable to those evoked by epidural anesthesia. CONCLUSIONS: Epidural anesthesia increases splanchnic venous capacitance by markedly decreasing splanchnic sympathetic nerve activity.

Anesthesia, Epidural↗
PubMed1993

CT-guided injection of the stellate ganglion: description of technique and efficacy of sympathetic blockade.

Stellate ganglion blockade, typically performed by using palpable osseous landmarks, is an accepted method in the diagnosis and treatment of sympathetically maintained pain and other conditions. The authors present the results of stellate ganglion injection performed with computed tomographic (CT) guidance. Thirteen CT-guided procedures were performed in seven patients. Lidocaine, bupivacaine, and buprenorphine were used to achieve the blockade. Successful blocks were achieved in all 13 cases as evidenced by production of Horner syndrome and ipsilateral hand temperature elevations. The average ipsilateral and contralateral hand temperature changes following the procedure were 7.5 degrees C and 0.5 degrees C. The ipsilateral hand temperature changes and the differences between the ipsilateral and contralateral hand temperature changes exceeded 1.5 degrees C in every case. Five patients preferred the CT-guided procedure over the conventional technique, and two patients noted no substantial difference between the approaches. With the CT-guided technique, a highly effective sympathetic block is achieved with a substantially reduced volume of anesthetic compared with the conventional approach.

Adult↗
PubMed1992

MR imaging of the stellate ganglion: normal appearance.

The stellate ganglion has not previously been identified by imaging techniques. MR imaging shows the stellate ganglion at the thoracic inlet adjacent to the neck of the first rib, lateral to the longus colli muscle and posterior to the vertebral artery. Although its shape varies somewhat, it can be identified consistently in normal persons.

Adult↗
PubMed1991

Lumbar epidural anatomy. A new look by cryomicrotome section.

The anatomic findings from cryomicrotome sections of 38 cadaver lumbar spines are reported. The technique produces high-resolution planar images of undisturbed epidural anatomy. Several observations differ from previous reports that used methods more prone to artifact. The epidural contents are found in circumferentially and metamerically segmented compartments, rather than in a uniform layer. Large areas of the dura are directly in contact with the spinal canal wall. The steeply arched ligamenta flava are fused in the midline to a variable degree. The space anterior to the dura is filled with veins and is isolated from the rest of the epidural space by a membranous lateral extension of the posterior longitudinal ligament. This membrane and a midline posterior fat pedicle are the only observed potential barriers to the spread of epidural solutions. These findings may be important in understanding the mechanics and pharmacokinetics of solutions injected into the epidural space and in refining techniques for needle and catheter placement.

Adolescent↗
PubMedDate not supplied

Effect of thoracic epidural anesthesia on spontaneous postinfarction ventricular dysrhythmia in awake dogs.

BACKGROUND AND OBJECTIVES: Sympathetic neural activity contributes to the genesis of ventricular ectopic activity, particularly in the setting of myocardial ischemia and infarction, so thoracic epidural anesthesia should diminish ventricular ectopy by blocking sympathetic innervation of the heart. However, the possible antidysrhythmic effect of epidural anesthesia has been studied only in the presence of general anesthesia. We therefore examined changes in spontaneous postinfarction ventricular dysrhythmia during thoracic epidural anesthesia in awake dogs. METHODS: A survivable myocardial infarction was created by two-stage ligation of the left anterior descending coronary artery. The following day, multifocal idioventricular tachycardia was the predominant cardiac rhythm. Lidocaine was administered either by thoracic epidural catheter to achieve block of at least the first five thoracic segments or intravenously as a control for direct effects, without concurrent general anesthesia or sedation. Electrocardiographic recordings were analyzed for the number of ventricular ectopic and sinoatrial depolarizations. RESULTS: Epidural and intravenous administration both produced plasma lidocaine concentrations of about 2 mg/mL. There was no change in rhythm following intravenous lidocaine. During epidural anesthesia, total ectopic beats per minute decreased from 167 +/- 8 to 135 +/- 14 (mean +/- SE, P < .05), and the dysrhythmic ratio (ventricular beats/total beats) decreased from 0.93 +/- 0.03 to 0.81 +/- 0.08 (P < .05). However, ventricular tachydysrhythmia remained the predominant rhythm. CONCLUSIONS: Epidural block modestly reduces spontaneous ventricular dysrhythmia in a perioperative setting in dogs following a large myocardial infarction. These findings do not support the choice of thoracic epidural anesthesia for the purpose of preventing or decreasing severe ventricular dysrhythmia.

Anesthesia, Epidural↗
PubMedDate not supplied

Effects of lidocaine and bupivacaine on isolated rabbit mesenteric capacitance veins.

BACKGROUND AND OBJECTIVES: The direct effects of circulating lidocaine and bupivacaine on splanchnic capacitance veins have not been examined previously. This article reports on the effects of clinically relevant concentrations of lidocaine and bupivacaine on adrenergic responsiveness of isolated rabbit mesenteric veins and examines the mechanism of changes. METHODS: Rings of ileal mesenteric capacitance veins were suspended in tissue baths for isometric tension measurements. Effects of lidocaine and bupivacaine on contractile responses to adrenergic nerve stimulation, exogenous norepinephrine (10(-6) M NE), and potassium chloride (80 mM KCl) were examined in endothelium-intact, L-NAME (10(-4) M) treated or denuded veins. RESULTS: Constriction in response to adrenergic nerve stimulation was attenuated by lidocaine and bupivacaine in a dose-dependent manner, with the potency of bupivacaine being higher than lidocaine. Unstimulated or potassium-constricted veins with and without endothelium were unaffected by lidocaine (0.25-100 microg/mL) and bupivacaine (0.1-100 microg/mL). In veins preconstricted by exogenously administered NE, a cumulative increase of both anesthetics produced no effect at low doses, an augmentation of constriction to NE at 5-20 microg/mL bupivacaine and 20-100 microg/mL lidocaine, and minimal effect at 50-100 microg/mL bupivacaine. These actions persisted in denuded or L-NAME treated veins. Nonincremental delivery of high concentrations of lidocaine or bupivacaine produced relaxation of NE and potassium-constricted rings in the absence and presence of L-NAME. CONCLUSIONS: Lidocaine and bupivacaine in concentrations typical during uncomplicated regional anesthesia inhibit adrenergic neurotransmission in rabbit mesenteric capacitance veins and produce modest venodilatation. Higher doses, resembling concentrations during accidental intravascular injection, result in substantial loss in vasomotor control of these capacitance vessels, which may contribute to hemodynamic effects.

Adrenergic alpha-Agonists↗
PubMedDate not supplied

Headache from intracranial air after a lumbar epidural injection: subarachnoid or subdural?

BACKGROUND AND METHODS: There is a growing awareness of the possibility of headache resulting from intracranial air secondary to identification of the epidural space by loss of resistance using air (LOR-A). Most reported cases have been attributed to subarachnoid air passage. A case is described of sudden headache following LOR-A. RESULTS: Various features of the case suggest that the passage of air to the head was subdural rather than subarachnoid. CONCLUSIONS: Recovery was uneventful.

Adult↗
PubMedDate not supplied

The spread of solutions during stellate ganglion block.

BACKGROUND AND OBJECTIVE: Though cervical paratracheal injections for the purpose of sympathetic block are customarily referred to as stellate ganglion blocks, there is no documentation of the actual site of local anesthetic action. The objective of this study is to test whether solution travels to the stellate ganglion during injections commonly used to anesthetize it. METHODS: In eight volunteers, magnetic resonance imaging was used to delineate the distribution of 15 ml saline injected by an anterior paratracheal technique at the sixth and seventh cervical vertebral levels. RESULTS: Injectate was not delivered to the stellate ganglion but rather passed anterior to it. CONCLUSIONS: The findings suggest that sympathetic neural block during stellate ganglion block may take place at sites other than the stellate ganglion.

Adult↗
PubMedDate not supplied

Epidural anatomy examined by cryomicrotome section. Influence of age, vertebral level, and disease.

BACKGROUND AND OBJECTIVES: Cryomicrotome section is a means of anatomic examination with minimal artifact ideally suited to delineating details of tissue relationships in the epidural space. In the past, healthy adult lumbar levels have been studied by this method. This report extends observations to other regions of the vertebral column, other age groups, and some abnormal conditions. METHODS: The bodies of 26 adults were frozen in toto soon after death, and the bodies of 2 children were frozen after embalming. Unstained anatomy was revealed by sectioning, and the exposed surface was photographed. RESULTS: As compared with the lumbar level, there are diminished epidural contents at the thoracic and cervical levels, and the ligamentum flavum is more frequently discontinuous. A large basivertebral vein with its origin in the anterior epidural space is typical of the lower thoracic and upper lumbar levels. Although the epidural contents are typically divided into compartments, there is incomplete segmentation of the posterior compartments during early childhood and often at thoracic levels in adults. In advanced age with degenerative disc and joint changes, distortion and compression of the epidural space are typical. CONCLUSIONS: Variations in epidural anatomy due to vertebral level, age, and disease may alter the ease of epidural entry and passage of catheters and injected solution.

Adult↗