Showing papers in "Anesthesiology in 1990"

Textbook of pain

Abstract: Introduction. SECTION ONE. . Basic Aspects. Peripheral & Central. . Peripheral Mechanisms of Nociceptors, R.A. Meyer. Inflammatory Pain (Including Cytokines) , J. Levine. Cellular Properties, S. Bevan. Neurotrophins, S.B. Mcmahon. Damaged Peripheral Nerve, M. Devor. Dorsal Horn , C.J. Woolf. Medulla to Thalamus, J. Dostrovsky. Cortex Imaging, M. Ingvar. Fetal -- Neonatal, M. Fitzgerald. Central Pharmacology, T. Yaksh. Dorsal Horn Plasticity, R. Dubner. CNS Modulation, H. Fields. Psychology. Emotions & Psychobiology, K.D. Craig. Cognition, M. Weisenberg. Measurement. Animals, R. Dubner. Children, P.J. Mcgrath. Normal People, R. Gracely. People in Pain, R. Melzack. Other Measures of Pain and Disability, A. De C.Williams, . SECTION TWO: CLINICAL STATES. Soft Tissue, Joints, And Bones. Postoperative Pain, M. Cousins. Osteoarthritis, P.Creamer. Rheumatoid Arthritis, M. Jayson. Muscle and Tendons , D. Newham. Low Back Pain, D.M. Long. Upper Extremity & Neck, A. E. Sola. Fibromyalgia , R. Bennett, . Deep and Visceral Pain. Abdominal, L. Blendis . Heart/Vascular (Including Haemopathies), Procacci. (A), Gynaecology , A.J. Rapkin. (B), Obstetrics, J.S. Mcdonald. Genitourinary, V. Wesselmann. Head. Orofacial, Y. Sharav. Trigeminal, Eye, Ear., J. Zakrzewska. Headache , J. Schoenen. Nerve and Root Damage. Amputation, T.S. Jensen. Peripheral Neuropathies , , J. Scadding. RSD, SMP. Nerve Roots and Arachnoiditis, D. Dubuisson. . Special Cases. (A) , Gender, K. Berkely. (B), Children, C. Berde. Elderly, L. Gagliese. Animals, C.E. Short. Cancer , R.K. Portenoy. (A), Psychiatry and Cancer, W. Breitbart. (B), Pain and Impending Death, C. Saunders. Central Nervous System. Central Pain, J. Boive. Spinal Cord Damage, A. Beric. Pain - Psychological Medicine, H. Merskey. SECTION THREE: THERAPEUTIC ASPECTS. Pharmacology. Methods of Therapeutic Trials, H. Mcquay, . Non-Narcotic Analgesics, K. Brune. Psychotropic Drugs, R.C. Monks. Opioids, R.G. Twycross. Local and Regional Anesthesia, H. Mcquay, . Other Drugs Including Sy

Perioperative Cardiac Morbidity

Abstract: Ischemic heart disease (IHD) can be complex in its clinical presentation. The patient with IHD usually has one of the many symptom complexes associated with varying degrees of ventricular dysfunction. As anesthesiologists, our assessment of a patient with IHD presenting for surgery is usually conducted over a very brief period of time and, therefore, requires a rather intense assessment of the patient’s cardiac status. Several other factors add to the difficulties involved in this assessment: 1) The age of the population presenting for surgery is increasing; 2) surgical procedures are becoming more complex; and 3) cost containment procedures will limit the number and type of preoperative tests used to assess risk in patients with IHD, and there will be increasing pressure on us to expedite such an assessment (e.g., come-and-go, come-and-stay surgery). Thus, more than ever, we must know what specific tests are available for assessment of these patients and what information we can obtain from these tests to determine perioperative risk, preoperative therapeutics, intraoperative monitoring, choice of anesthetic, and postoperative care.

Adverse Respiratory Events in Anesthesia: A Closed Claims Analysis

Abstract: Adverse outcomes associated with respiratory events constitute the single largest class of injury in the American Society of Anesthesiology Closed Claims Study (522 of 1541 cases; 34%). Death or brain damage occurred in 85% of cases. The median cost of settlement or jury award was +200,000. Most outcomes (72%) were considered preventable with better monitoring. Three mechanisms of injury accounted for three-fourths of the adverse respiratory events: inadequate ventilation (196; 38%), esophageal intubation (94; 18%), and difficult tracheal intubation (87; 17%). Inadequate ventilation was used to describe claims in which it was evident that insufficient gas exchange had produced the adverse outcome, but it was not possible to identify the exact cause. This group was characterized by the highest proportion of cases in which care was considered substandard (90%). The esophageal intubation group was notable for a recurring diagnostic failure: in 48% of cases where auscultation of breath sounds was performed and documented, this test led to the erroneous conclusion that the endotracheal tube was correctly located in the trachea. Claims for difficult tracheal intubation were distinguished by a comparatively small proportion of cases (36%) in which the outcome was considered preventable with better monitoring. A better understanding of respiratory risks may require investigative protocols that initiate data collection immediately upon the recognition of a critical incident or adverse outcome.

Molecular mechanisms of local anesthesia: a review.

Abstract: Impulse block by LA occurs through the inhibition of voltage-gated Na+ channels. Both protonated and neutral LAs can inhibit Na+ channels though interference with the conformational changes that underly the activation process (the sequence of events that occurs as channels progress from the closed resting state to the open conducting state). The occlusion of open channels contributes little to the overall inhibition. Local anesthetic inhibition of Na+ currents increases with repetitive depolarizations in a process called phasic block. Phasic block represents increased LA binding, either because more channels become accessible during depolarization or because the channel conformations favored by depolarization bind LA with higher affinity. The details of phasic block are dependent on LA chemistry: certain LAs bind and dissociate quite rapidly, others act more slowly; some LAs interact effectively with closed states that occur intermediately between resting and open states, others favor the open channel, and still others have a higher affinity for inactivated states. Channel activation accelerates LA binding, and LAs may bind more tightly to activated and inactivated than to resting channels. In this regard, both the modulated receptor and the guarded receptor hypotheses are valid. In binding to activated and inactivated channels, LAs prevent the conformational changes of activation and antagonize the binding of activator agents that poise channels in activated, open states. These reciprocal actions are one aspect of the concerted conformational rearrangements that occur throughout Na+ channels during gating. The LA binding site may exist in the channel's pore, at the membrane-protein interface, or within the protein subunits of the channel. Judging from its susceptibility to intracellular proteases and its accessibility to LAs with limited membrane permeability (i.e., quaternary LAs in the cytoplasm), the site lies nearer to the cytoplasmic than the external surface of the membrane. Nevertheless, protons in the external medium influence the dissociation of LA from the closed channel. Binding of LAs at the inhibitory site is weak and loose. If one accounts for the membrane-concentrating effects of LA hydrophobicity that are expressed as membrane: buffer partition coefficients equal to 10(2)-10(4), then the apparent LA affinities are low. The equilibrium dissociation constants calculated on the basis of free drug in the membrane are 1-10 mM, with a correspondingly weak binding to the inhibitory LA site. The stereospecificity of LA action is also relatively nonselective, suggesting a loose fit between ligand and binding site.(ABSTRACT TRUNCATED AT 400 WORDS)

The metabolic response to stress: an overview and update.

Abstract: Recent investigation has demonstrated that the response to stress is mediated by complex interactions between the nervous, endocrine, immune, and hematopoietic systems. Not only is the neuroendocrine system operative but monokines and lymphokines, such as IL-1, IL-6, and TNF, also play important roles. The discovery of these mediators, along with that of macrophage-derived substances that operate at the local wound level, such as platelet-derived, basic fibroblast, transforming, and epidermal growth factors, coupled with advances in molecular biology portends much for the future. The ability to alter the endocrine response with techniques such as epidural anesthesia, the ability to specifically block certain aspects of the response (e.g., with adrenergic and prostaglandin antagonists), and the ability to synthesize potential beneficial mediators with recombinant DNA techniques (e.g., GH) may allow for modulating the response to decrease debility and complications.

Frequent Hypoxemia and Apnea after Sedation with Midazolam and Fentanyl

Abstract: More than 80 deaths have occurred after the use of midazolam (Versed), often in combination with opioids, to sedate patients undergoing various medical and surgical procedures. We investigated the respiratory effects of midazolam (0.05 mg.kg-1) and fentanyl (2.0 micrograms.kg-1) in volunteers. The incidence of hypoxemia (oxyhemoglobin saturation less than 90%) and apnea (no spontaneous respiratory effort for 15 s) and the ventilatory response to carbon dioxide were evaluated. Midazolam alone produced no significant respiratory effects. Fentanyl alone produced hypoxemia in half of the subjects and significant depression of the ventilatory response to CO2, but did not produce apnea. Midazolam and fentanyl in combination significantly increased the incidence of hypoxemia (11 of 12 subjects) and apnea (6 of 12 subjects), but did not depress the ventilatory response to CO2 more than did fentanyl alone. Adverse reactions linked to midazolam and reported to the Department of Health and Human Services highlight apnea- and hypoxia-related problems as among the most frequent adverse reactions. Seventy-eight per cent of the deaths associated with midazolam were respiratory in nature, and in 57% an opioid had also been administered. All but three of the deaths associated with the use of midazolam occurred in patients unattended by anesthesia personnel. We conclude that combining midazolam with fentanyl or other opioids produces a potent drug interaction that places patients at a high risk for hypoxemia and apnea. Adequate precautions, including monitoring of patient oxygenation with pulse oximetry, the administration of supplemental oxygen, and the availability of persons skilled in airway management are recommended when benzodiazepines are administered in combination with opioids.

Skin-surface Temperature Gradients Correlate with Fingertip Blood Flow in Humans

Abstract: Skin-surface temperature gradients (forearm temperature - fingertip temperature) have been used as an index of thermoregulatory peripheral vasoconstriction. However, they have not been specifically compared with total finger blood flow, nor is it known how long it takes fingertip temperature to fully reflect an abrupt change in finger blood flow. Steady-state skin-temperature gradients were compared with total fingertip blood flow in 19 healthy volunteers. There was an excellent correlation between steady-state skin-surface temperature gradients and total fingertip blood flow measured with venous-occlusion volume plethysmography: gradient = 0.2-5.7.log(flow), r = 0.98. The half-time for fingertip cooling after complete arterial obstruction (in 8 volunteers) was 6.6 +/- 1.2 min. The authors conclude that skin-temperature gradients are an accurate measure of thermoregulatory peripheral vasoconstriction.

Nerve injury associated with anesthesia.

Abstract: The authors examined the American Society of Anesthesiologists Closed Claims Study database to define the role of nerve damage in the overall spectrum of anesthesia-related injury that leads to litigation. Of 1,541 claims reviewed, 227 (15%) were for anesthesia-related nerve injury. Ulnar neuropathy represented one-third of all nerve injuries and was the most frequent nerve injury. Less-frequent sites of nerve injury were the brachial plexus (23%) and the lumbosacral nerve roots (16%). In a large proportion of cases, the exact mechanism of injury was unclear despite evidence of intensive investigation in the claim files. Median payment for nerve damage claims involving disabling injury was $56,000, which was significantly lower than the $225,000 median payment for claims for disabling injury not involving nerve damage (P less than 0.01). The closed claims reviewers judged that the standard of care had been met significantly more often in claims involving nerve damage than in claims not involving nerve damage. The authors conclude that nerve damage is a significant source of anesthesia-related claims but that the exact mechanism of nerve injury is often unclear. In particular, ulnar nerve injuries seemed to occur without identifiable mechanism.

Hormonal-metabolic stress responses in neonates undergoing cardiac surgery.

Abstract: Hormonal and metabolic responses were measured in 15 neonates who underwent repair of complex congenital heart defects during a standardized anesthetic protocol. Four of the 15 neonates died postoperatively in the intensive care unit. Analysis of arterial plasma samples obtained before, during, and 24 h after surgery showed that plasma epinephrine, norepinephrine, cortisol, glucagon, and beta endorphin increased in all patients (P less than 0.05). Insulin levels increased only at the end of surgery but remained elevated for 24 h postoperatively (P less than 0.02). Intraoperative metabolic changes were characterized by hyperglycemia and lactic acidemia that persisted postoperatively. This pattern of neonatal stress responses is distinct from and more extreme than that seen in adult cardiac surgical patients. The four neonates who died postoperatively tended to have higher stress responses intra- and postoperatively despite having been indistinguishable from survivors by the usual clinical and hemodynamic criteria. These preliminary results suggest that neonatal hormonal and metabolic responses to cardiac surgical operations in neonates are extreme and are associated with a high hospital mortality rate.

Oral Midazolam Preanesthetic Medication in Pediatric Outpatients

Abstract: A need exists for a safe and effective oral preanesthetic medication for use in children undergoing elective surgical procedures. We evaluated the effectiveness of three different doses of oral midazolam when administered in combination with atropine prior to ambulatory surgery. In this randomized, double-blind, placebo-controlled study, 124 children, ages 1-10 yr, received midazolam, 0.25, 0.50, or 0.75 mg.kg-1 po, and atropine, 0.03 mg.kg-1 po, mixed with apple juice, or a placebo (containing the midazolam vehicle, atropine, and apple juice). A blinded observer noted the child's level of sedation, the quality of separation from parents, and the degree of cooperation with an inhalation induction of anesthesia. Picture-recall was used to assess the amnesic effect of midazolam in children over 5 yr of age. Midazolam 0.75 mg.kg-1 produced significant sedation at 30 min. After procedures lasting an average of 106-113 min, recovery was not prolonged by the oral midazolam-atropine combination. We concluded that oral midazolam 0.5-0.75 mg.kg-1 is an effective preanesthetic medication for pediatric outpatients.

Effects of thoracic epidural anesthesia on coronary arteries and arterioles in patients with coronary artery disease.

Abstract: The effect of cardiac sympathetic blockade by high thoracic epidural anesthesia (TEA) (T1-T6, bupivacaine) on the luminal diameter of normal and diseased portions of epicardial coronary arteries was determined by quantitative coronary angiography in patients (n = 27) with severe coronary artery disease (CAD). In a separate group of patients (n = 9) with severe CAD, the effects of TEA on coronary arterioles (resistance vessels) were studied, by measuring total and regional myocardial blood flow and metabolism with the retrograde coronary sinus thermodilution technique. At the stenotic segments, TEA induced an increase in luminal diameter from 1.34 +/- 0.11 to 1.56 +/- 0.13 mm (P less than 0.002), but did not change the diameter of the nonstenotic segments (3.07 +/- 0.13 to 2.99 +/- 0.13 mm). In the second group of patients, TEA induced no changes in coronary perfusion pressure, total or regional myocardial blood flow, coronary venous oxygen content, coronary blood flow distribution, regional myocardial oxygen consumption, or lactate extraction or uptake. Two patients had chest pain in the control situation and had regional myocardial lactate production that was attenuated by TEA. We conclude that TEA may increase the diameter of stenotic epicardial coronary artery segments in patients with CAD without causing a dilation of coronary arterioles. These effects may be beneficial when high TEA is used to treat severe ischemic chest pain in patients at rest.

Anesthesia with abdominal surgery leads to intense REM sleep during the first postoperative week.

Abstract: Characteristics of nocturnal sleep were investigated in six patients after anesthesia and cholecystectomy and in another six after anesthesia and gastroplasty. All night polysomnographic recordings were obtained while each patient slept in a private surgical ward room through two nights before and five or six nights after operation. Anesthesia included thiopental, N2O, isoflurane, and fentanyl. Postoperative analgesia was provided with parenteral morphine. Other aspects of care were routine. Nocturnal sleep was markedly disturbed after both surgical procedures. Throughout the operative night and subsequent one or two nights, sleep was highly fragmented with the usual recurring cycles of sleep stages completely disrupted. Slow wave sleep was suppressed and rapid eye movement (REM) sleep virtually eliminated. During the following 2-4 nights, as other aspects of sleep recovered, REM sleep reappeared and then increased to greater than the preoperative amount. This increased REM sleep was marked by a heavy density of eye movement activity along with frequent patient reports of unusually distressing dreams or vivid nightmares. It is concluded that anesthesia with upper abdominal surgery leads to a severe disruption of nocturnal sleep followed by the release of highly intense REM sleep about the middle of the first postoperative week.

Benzodiazepines and human memory: a review.

Abstract: In this article we attempt to review critically the effects of benzodiazepines on human memory and evaluate the information within the advancing boundaries of psychopharmacology and cognitive psychology

Pharmacokinetics of fentanyl administered by computer-controlled infusion pump.

Abstract: Fentanyl was administered to 21 patients using a computer-controlled infusion pump (CCIP) based on a pharmacokinetic model. Eleven of the patients were dosed according to the pharmacokinetics described by McClain and Hug, and ten of the patients were dosed according to the pharmacokinetics described by Scott and Stanski. The authors measured the difference between the measured arterial fentanyl concentrations and the concentrations predicted by the CCIP for each pharmacokinetic parameter set. The median absolute performance error (MDAPE) in patients dosed according to McClain and Hug's parameters was 61%, and the MDAPE in patients dosed according to Scott and Stanski's parameters was 33%. The population pharmacokinetics in these 21 patients were analyzed using a pooled data technique. The pharmacokinetics of fentanyl in this population showed a smaller central compartment volume and a more rapid initial distribution half-life than previously estimated for fentanyl. The derived pharmacokinetic parameters described these patients well and also predicted the observed fentanyl concentrations from four previously published fentanyl studies with reasonable accuracy. Comparison of the parameters used by the authors with those of McClain and Hug demonstrated that dosing regimens designed from pharmacokinetic models can be fairly accurate at the times sampled in the original study but may not be accurate at time points not sampled in the original research. The authors concluded that although the pharmacokinetics of fentanyl administered by CCIP are the same as the pharmacokinetics of fentanyl administered by a bolus or constant rate infusion, a pharmacokinetic study using a CCIP may be particularly effective at characterizing the most rapid distribution pharmacokinetic parameters, and thus may provide parameters appropriate for subsequent use in a CCIP.

Dexmedetomidine, an α2-adrenoceptor Agonist, Reduces Anesthetic Requirements for Patients Undergoing Minor Gynecologic Surgery

Abstract: The effects of dexmedetomidine, an alpha 2-adrenoceptor agonist, on vigilance, thiopental anesthetic requirements, and the hemodynamic, catecholamine, and hormonal responses to surgery were investigated in healthy (ASA physical status 1) women scheduled for dilatation and curettage (D & C) of the uterus. Fifteen minutes before induction they received single iv doses of either dexmedetomidine (0.5 micrograms/kg; n = 19) or saline (n = 20) in a double-blind fashion. Anesthesia was induced with thiopental and maintained with N2O/O2 (70/30%) and thiopental. Dexmedetomidine was well tolerated and no serious drug-related subjective side-effects or adverse events were observed. The most prominent subjective effects were fatigue and decreased salivation. The total amount of thiopental needed to perform D & C of the uterus was reduced approximately 30% (from 456 +/- 141 mg [mean +/- SD] after saline to 316 +/- 79 mg after dexmedetomidine). This was mostly due to a smaller induction dose in the group receiving dexmedetomidine. Dexmedetomidine appeared to improve the recovery from anesthesia as measured by visual analogue scales (VAS) on fatigue and nausea. The plasma concentration of norepinephrine was decreased by 56% after dexmedetomidine implying decreased sympathetic nervous activity. Systolic and diastolic blood pressure were moderately reduced after dexmedetomidine administration. The authors conclude that dexmedetomidine preanesthetic medication decreases thiopental anesthetic requirements and improves the recuperation from anesthesia with no serious hemodynamic or other adverse effects. Further studies in patients undergoing more stressful surgery are indicated.

Effects of sevoflurane and isoflurane on cardiac and coronary dynamics in chronically instrumented dogs.

Abstract: To assess the hemodynamic properties of the new inhalational anesthetic sevoflurane, 22 dogs were chronically instrumented for measurement of heart rate, aortic, left ventricular and left atrial pressures, cardiac output, and coronary blood flow. Dogs were randomly assigned to two groups, receiving

Superior hypogastric plexus block for pelvic cancer pain.

Abstract: Blockade of the superior hypogastric nerve plexus was performed for relief of chronic cancer related pelvic pain. The targeted sympathetic nerves lie anterior to the sacral promontory. Twenty-eight patients with neoplastic involvement of pelvic viscera secondary to cervical, prostate, and testicular cancer or radiation injury were treated with neurolytic superior hypogastric plexus block. Sympathetically mediated pain was significantly reduced or eliminated in all cases and no serious complications occurred. Superior hypogastric plexus block is recommended for diagnostic/prognostic and therapeutic purposes in patients with chronic pelvic pain, particularly when pain is of neoplastic origin.

Tolerance and dependence in neonates sedated with fentanyl during extracorporeal membrane oxygenation.

Abstract: We undertook a retrospective chart review of 37 neonates who received fentanyl by continuous infusion while undergoing extracorporeal membrane oxygenation (ECMO) between May 1986 and October 1988. We quantified the doses of all sedatives utilized, determined the incidence of neonatal abstinence syndrome (NAS), and identified risk factors associated with NAS. We determined peak fentanyl infusion rate, mean fentanyl infusion rate, total fentanyl dose, and duration of ECMO therapy. NAS was observed in 21 of 37 neonates (57%). In both the NAS and non-NAS neonates, mean infusion rate increased steadily during ECMO therapy, from a mean of 11.6 +/- 6.9 (SD) micrograms.kg-1.h-1 on day 1 to a mean of 52.5 +/- 19.4 (SD) micrograms.kg-1.h-1 by day 8. Total fentanyl dose and duration of ECMO were significantly greater in neonates with NAS. We found that neonates with a total dose greater than 1.6 mg/kg or an ECMO duration greater than 5 days had a significantly greater incidence of NAS (chi-squared test, P less than 0.01 and P less than 0.005; odds ratios = 7.0 and 13.9, respectively). With multiple logistic regression, ECMO duration was found to be the most powerful predictor of the occurrence of NAS. We also measured plasma fentanyl concentrations in a separate group of 5 neonates receiving fentanyl by continuous infusion for sedation. Fentanyl concentrations increased steadily during the period of infusion, suggesting the development of tolerance to the sedating effects. We conclude that continuous administration of fentanyl for sedation is associated with the uniform development of tolerance and a significant incidence of dependence. Alternative approaches to sedation should be investigated.

Influence of high-dose aprotinin treatment on blood loss and coagulation patterns in patients undergoing myocardial revascularization.

Abstract: Intraoperative administration of the proteinase inhibitor aprotinin causes reduction in blood loss and homologous blood requirement in patients undergoing cardiac surgery. To ascertain the blood-saving effect of aprotinin and to obtain further information about the mode of action, 40 patients undergoing primary myocardial revascularization were randomly assigned to receive either aprotinin or placebo treatment. Aprotinin was given as a bolus of 2 x 10(6) kallikrein inactivator units (KIU) before surgery followed by a continuous infusion of 5 x 10(5) KIU/h during surgery. Additionally, 2 x 10(6) KIU were added to the pump prime. Strict criteria were used to obtain a homogeneous patient selection. Total blood loss was reduced from 1,431 +/- 760 ml in the control group to 738 +/- 411 ml in the aprotinin group (P less than 0.05) and the homologous blood requirement from 838 +/- 963 ml to 163 +/- 308 ml (P less than 0.05). In the control group, 2.3 +/- 2.2 U of homologous blood or blood products were given, and in the aprotinin group, 0.63 +/- 0.96 U were given (P less than 0.05). Twenty-five percent of patients in the control group and 63% in the aprotinin group did not receive banked blood or homologous blood products. The activated clotting time as an indicator of inhibition of the contact phase of coagulation was significantly increased before heparinization in the aprotinin group (141 +/- 13 s vs. 122 +/- 25 s) and remained significantly increased until heparin was neutralized after cardiopulmonary bypass (CPB).(ABSTRACT TRUNCATED AT 250 WORDS)

Vecuronium neuromuscular blockade at the diaphragm, the orbicularis oculi,and adductor pollicis muscles

Abstract: To determine the relationship among diaphragm, orbicularis oculi, and adductor pollicis blockade, train-of-four stimulation was applied to the phrenic, facial, and ulnar nerves in 16 adult patients anesthetized with alfentanil-propofol-oxygen. Vecuronium 0.04 or 0.07 mg/kg was given. The response of the adductor pollicis was measured with a force transducer, and that of the other muscles by electromyography (EMG). No statistically significant differences were detected with either dose in the intensity of maximum blockade measured at the three muscles. With 0.04 mg/kg, the first response (T1) in the train-of-four was decreased (mean +/- SEM) 78 +/- 8, 62 +/- 11, and 84 +/- 3% for the diaphragm, orbicularis oculi, and adductor pollicis, respectively. Corresponding values after 0.07 mg/kg were 95 +/- 3, 82 +/- 11, and 95 +/- 2%, respectively. However, onset time was longer at the adductor pollicis than at the diaphragm, and the orbicularis oculi onset time approached that of the diaphragm. With 0.04 mg/kg, time to maximum diaphragmatic blockade was 2.9 +/- 0.3 min, compared with 3.7 +/- 0.6 min at the orbicularis oculi (no significant difference [NS]) and 6.6 +/- 0.4 min at the adductor pollicis (P less than 0.001). With vecuronium 0.07 mg/kg the values were 2.2 +/- 0.3, 3.4 +/- 0.5 (P = 0.024), and 6.3 +/- 0.6 (P less than 0.001), respectively. Time to 75% T1 recovery was similar at the diaphragm and the orbicularis oculi, but significantly longer at the adductor pollicis.(ABSTRACT TRUNCATED AT 250 WORDS)

Ingestion of liquids compared with preoperative fasting in pediatric outpatients.

Abstract: The preoperative fast is often an unpleasant preoperative experience that might be alleviated by allowing children to drink clear liquids. The authors compared gastric fluid volume and pH in two groups of children, one of whom was permitted clear liquids until 2 h before surgery (study group) and th

Infection during chronic epidural catheterization: diagnosis and treatment.

Abstract: A potentially serious complication of long-term epidural catheterization in cancer patients is infection. The early signs of infection were studied in 350 patients in whom long-term epidural catheters were inserted. Three areas of the catheter track were found to be involved; exit site and superficial catheter track infection, and epidural space infection. The authors identified the early signs of infection in each area and the progress of the infection from the deep track to include the epidural space in four of these patients. All 19 patients who developed deep track or epidural infections were successfully treated with antibiotics and catheter removal. None of the patients required surgery for spinal cord decompression. Catheters were replaced in 15 of the 19 treated patients who requested them after treatment with no recurrent infections. It was concluded that use of long-term epidural catheterization is associated with a definable epidural infection rate. The use of epidural opioid analgesia is an effective and safe means of obtaining pain relief for terminally ill patients when patients are monitored for possible infection and receive prompt treatment when the diagnosis is established.

Reevaluation of hemodynamic consequences of positive pressure ventilation: emphasis on cyclic right ventricular afterloading by mechanical lung inflation.

Abstract: To examine the cyclic changes in right ventricular (RV) function induced by controlled ventilation, right heart catheterization and two-dimensional echocardiography were combined in a group of 20 patients requiring respiratory support for an episode of acute respiratory failure. Simultaneous measurements of RV pressure (using a modified pulmonary artery catheter), RV stroke output (thermodilution), and RV dimensions (two-dimensional echocardiography), permitted a beat to beat evaluation of RV function throughout the mechanical respiratory cycle. When compared with expiration, lung inflation produced an increase in RV systolic pressure and volume, an increase in RV diastolic volume with an unchanged RV diastolic pressure, and a marked decrease in RV ejection fraction. It is concluded that controlled ventilation altered RV function primarily by increasing RV afterload during the lung inflation period.

Is the site of action of ketamine anesthesia the N-methyl-D-aspartate receptor?

Abstract: Synaptic mechanisms underlying ketamine anesthesia were studied using in vitro preparations of the lamprey CNS. Although lampreys are one of the most primitive vertebrates, the synaptic physiology and pharmacology are similar to those in the higher vertebrates. Axonal conduction, transmitter release from the presynaptic terminal, postsynaptic response to the putative neurotransmitters, and resting and activated membrane properties were studied in the absence and the presence of various concentrations of ketamine. Ketamine markedly reduced N-methyl-D-aspartate (NMDA)-activated responses, such as depolarizations to bath-applied NMDA and bursting rhythm during "fictive locomotion." The 50% block of the responses took place in the presence of 10-20 microM ketamine, whereas those induced by kainate and quisqualate (the other two subclasses of L-glutamate/L-aspartate agonists) were spared at concentrations higher than 600-800 microM. None of the other neuronal events tested were suppressed in the presence of still higher concentrations of ketamine. The results support the hypothesis that ketamine might exert its anesthetic effect by a pharmacologically specific interaction with the NMDA receptor.

A Single-blind Study of Combined Pulse Oximetry and Capnography in Children

Abstract: This single-blind study examined four levels of monitoring in 402 pediatric cases. Patients were randomly assigned to one of four groups: 1) oximeter and capnograph; 2) only oximeter; 3) only capnograph; or 4) neither oximeter nor capnograph data available to the anesthesia team. An anesthesiologist, not involved in patient care, observed all cases and continuously recorded hemoglobin oxygen saturation (Spo2), ECG, expired CO2, and the oximeter plethysmographic output. Mean age, weight, ASA physical status, airway management (mask or endotracheal tube), and anesthetic technique were similar in each group. Two-hundred sixty problems were documented in 153 patients. Fifty-nine events in 43 patients resulted in "major" desaturation (Spo2 less than or equal to 85% for greater than or equal to 30 s). Fifteen "major" capnograph events (esophageal intubation, disconnection, accidental extubation, or obstructed endotracheal tube) were observed in 11 patients; 8 of these also developed varying degrees of desaturation. One-hundred thirty "minor" desaturation events (Spo2 less than or equal to 95% for greater than 60 s) and 79 "minor" desaturation events (hypercarbaria or hypocarbia) were observed. A number of problems fulfilled criteria in multiple categories. Infants less than or equal to 6 months of age had the highest incidence of major desaturation events (18 of 65 [27%]) compared to toddlers 7-24 months of age or children greater than 24 months of age (P less than 0.001). Blinding the oximeter data increased the number of patients (12 vs. 31) experiencing major desaturation events (P = 0.003); blinding the capnograph data altered neither the frequency of desaturation events nor the incidence of major capnograph events.(ABSTRACT TRUNCATED AT 250 WORDS)

hemofiltration reverses left ventricular dysfunction during sepsis in dogs.

Abstract: Depressed left ventricular (LV) contractility in sepsis has been ascribed to the presence of circulating cardiodepressant substance (filterable cardiodepressant factor in sepsis [FCS]); however, this finding is controversial. The authors hypothesized that if a decrease in LV contractility indeed occurred due to a circulating depressant substance, then removal of this substance by hemofiltration would reverse by dysfunction. In this study, LV mechanics were examined before and after hemofiltration in anesthetized dogs during continuous intravenous infusion of live Escherichia coli. Left ventricular anterior-posterior and apex-base dimensions were measured by subendocardial ultrasonic crystal transducers implanted 4 weeks before the experiments. Left ventricular contractility was determined from the end-systolic pressure-dimension relationship. The slope of this relationship (Emax) is an index of contractility. After 4 h of sepsis, Emax was reduced by one half. Hemofiltration resulted in a return of Emax to control values. The FCS activity in the plasma was also assessed by the percent reduction in isometric contraction of electrically stimulated, isolated right ventricular trabeculae obtained from nonseptic dogs. The FCS activity reached a peak 4 h after sepsis and was reduced after 2 h of hemofiltration. The results show that during experimental sepsis, a circulating substance of less than 30,000 d produces a decrease in LV contractility and that this LV dysfunction may be improved by hemofiltration.

Skin-surface warming : heat flux and central temperature

Abstract: The authors determined the efficacy of four postoperative warming devices by measuring cutaneous and tympanic membrane temperatures, and heat loss/gain using 11 thermocouples and ten thermal flux transducers in five healthy, unanesthetized volunteers. Overall thermal comfort was evaluated at 5-10 min intervals using a 10-cm visual analog scale. The warming devices were: 1) a pair of 250-W infrared heating lamps mounted 71 cm above the abdomen; 2) the Thermal Ceiling MTC XI UL (500 W) set on "high" and mounted 56 cm above the volunteer; 3) a 54-by-145-cm circulating-water blanket set to 40 degrees C placed over the volunteer; and 4) the Bair Hugger forced air warmer with an adult-sized cover set on "low" (approximately 33 degrees C), "medium" (approximately 38 degrees C), and "high" (approximately 43 degrees C). Following a 10-min control period, each device was placed over the volunteer and activated for a 30-min period. All devices were started "cold" and warmed up during the study period. The Bair Hugger set on "medium" decreased heat loss more than each radiant warming device and as much as the circulating-water blanket. All methods reached maximum efficacy within 20 min. Set on "high," the Bair Hugger increased skin-surface temperature more than the circulating-water blanket. The Bair Hugger (all settings) and the water blanket raised skin temperature more than the radiant heaters. The circulating-water blanket was the most effective device for heating an optimally placed transducer on the chest (directly under and parallel to the radiant heat sources, and touching the water and Bair Hugger blankets).(ABSTRACT TRUNCATED AT 250 WORDS)

Prostacyclin for the treatment of pulmonary hypertension in the adult respiratory distress syndrome: effects on pulmonary capillary pressure and ventilation-perfusion distributions.

Abstract: Nine patients who had developed pulmonary artery hypertension during the adult respiratory distress syndrome (ARDS) were treated with an infusion of prostacyclin (PGI2) (12.5-35.0 ng.kg-1.min-1). Whether PGI2 might decrease the pulmonary capillary pressure (PCP) obtained by analysis of the pulmonary artery occlusion pressure decay curve and improve systemic oxygen delivery was examined. Gas exchange alterations induced by PGI2 were analyzed by using the multiple inert gas elimination technique. PGI2 reduced the pulmonary artery pressure from 35.6 to 28.8 mmHg (P less than 0.001) and the PCP from 22.9 to 19.7 mmHg (P less than 0.01) without changing the contribution of the pulmonary venous resistance to the total pulmonary vascular resistance. The cardiac index increased from 4.2 to 5.7 1.min-1.m-2 (P less than 0.001) due to both increased stroke volume and heart rate. Despite a marked deterioration of ventilation-perfusion (VA/Q) matching with increased true intrapulmonary shunt flow from 28.6% to 38.6% (P less than 0.01) of the cardiac output, the PaO2 was unchanged due to increased mixed venous oxygen content indicated by an augmented mixed venous PO2 (from 37.0 to 41.9 mmHg, P less than 0.01). This caused a 35% (P less than 0.001) increase of the systemic oxygen delivery rate. Thus, short-term infusions of PGI2 reduced PAP and PCP without deleterious effects on arterial oxygenation in patients with ARDS. Hence, PGI2 may be useful to lower pulmonary vascular pressures in patients with ARDS.

Clonidine-induced analgesia in postoperative patients: epidural versus intramuscular administration.

Abstract: To compare the analgesic efficacy and plasma concentration of intramuscular (IM) versus epidural (EP) clonidine, 20 patients recovering from orthopedic or perineal surgery were randomly divided into two groups of ten. Clonidine (2 micrograms/kg) was administered epidurally in group 1 and intramuscularly in group 2. Analgesia was assessed using a visual analog scale (VAS) over a period of 6 h following clonidine administration. Venous blood samples were obtained at specific intervals for radioimmunoassay determination of plasma clonidine concentrations. The maximum reduction in VAS pain score was 78.5 +/- 20.6% in the EP group and 68.1 +/- 31.5% in the IM group (NS). Onset of analgesia was similar (within 15 min of injection), but duration tended to be longer after epidural than intramuscular administration (208 +/- 87 min vs. 168 +/- 95 min, mean +/- SD, P greater than 0.05). The peak plasma clonidine concentration after EP injection was 0.82 +/- 0.22 ng/ml and 1.02 +/- 0.76 ng/ml after IM injection. Hypotension, bradycardia, and drowsiness occurred with both methods of administration. None of these effects required treatment. Thus, in postoperative patients clonidine produces similar analgesia and side effects after parenteral or EP administration.