RESUMO
BACKGROUND: Opioids have become an integral part of anaesthesia induction. We aimed to determine the dose of alfentanil needed to obtain perfect tracheal intubation conditions during rapid sequence induction with standard doses of thiopental and rocuronium, where laryngoscopy was initiated 55 s after commencement of drug administration. The influence of covariates (sex, body weight, age, alfentanil plasma concentration at laryngoscopy) was tested. METHODS: Eighty-four healthy individuals were randomly assigned to receive one of the seven assessor-blinded alfentanil doses (0, 10, 20, 30, 40, 50 and 60 µg/kg) in conjunction with thiopental 4 mg/kg and rocuronium 0.6 mg/kg. For drug administration, 15 s was allowed. Laryngoscopy was initiated 40 s after rocuronium and tracheal intubation concluded within 70 s after commencement of drug administration. Alfentanil doses associated with 50%, 90% and 95% probability of perfect intubation conditions were determined with logistic regression. Multiple logistic regressions were used to test the influence of covariates. The relationship between alfentanil dose and concentration at laryngoscopy was analysed with linear regression. The effects of covariates on plasma concentrations of alfentanil were tested with multiple linear regressions. RESULTS: Perfect intubation conditions of 95% probability was obtained with 56 µg/kg (confidence intervals 44-68). None of the covariates were significant predictors of perfect intubation conditions. Alfentanil plasma concentration correlated with dose and increased with increasing body weight (1.7 ng/ml/kg). CONCLUSION: Perfect intubation conditions during rapid sequence induction can be obtained with clinically relevant doses of alfentanil in most healthy patients anaesthetized with thiopental 4 mg/kg and rocuronium 0.6 mg/kg.
Assuntos
Alfentanil/administração & dosagem , Androstanóis/administração & dosagem , Intubação Intratraqueal , Tiopental/administração & dosagem , Adulto , Alfentanil/sangue , Feminino , Humanos , Modelos Logísticos , Masculino , Pessoa de Meia-Idade , RocurônioRESUMO
Pulse oximetry is a standard of care during anaesthesia in high-income countries. However, 70% of operating environments in low- and middle-income countries have no pulse oximeter. The 'Lifebox' oximetry project set out to bridge this gap with an inexpensive oximeter meeting CE (European Conformity) and ISO (International Organization for Standardization) standards. To date, there are no performance-specific accuracy data on this instrument. The aim of this study was to establish whether the Lifebox pulse oximeter provides clinically reliable haemoglobin oxygen saturation (Sp O2 ) readings meeting USA Food and Drug Administration 510(k) standards. Using healthy volunteers, inspired oxygen fraction was adjusted to produce arterial haemoglobin oxygen saturation (Sa O2 ) readings between 71% and 100% measured with a multi-wavelength oximeter. Lifebox accuracy was expressed using bias (Sp O2 - Sa O2 ), precision (SD of the bias) and the root mean square error (Arms). Simultaneous readings of Sa O2 and Sp O2 in 57 subjects showed a mean (SD) bias of -0.41% (2.28%) and Arms 2.31%. The Lifebox pulse oximeter meets current USA Food and Drug Administration standards for accuracy, thus representing an inexpensive solution for patient monitoring without compromising standards.
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Hipóxia/diagnóstico , Monitorização Fisiológica/instrumentação , Monitorização Fisiológica/normas , Oximetria/instrumentação , Oximetria/normas , Adulto , Feminino , Voluntários Saudáveis , Humanos , Hipóxia/sangue , Masculino , Monitorização Fisiológica/métodos , Oximetria/métodos , Reprodutibilidade dos TestesRESUMO
BACKGROUND: Studies in volunteers suggest that train-of-four (TOF) ratios >0.9 are needed to retain normal function of muscles involved in upper airway patency, swallowing, and vital capacity breathing. We determined if sex-related differences exist in the relationship between adductor pollicis (AP) TOF ratio and measures of neuromuscular function commonly used to assess recovery from neuromuscular block. METHODS: In 10 males and 10 females, three steady-state levels of neuromuscular block were achieved with mivacurium infusions. TOF ratio was measured with acceleromyography at the AP. Hand grip strength and the ability to clench the teeth, raise the head >5 s, swallow, protrude the tongue, and open the eyes were tested at each stable block level and reconciled to uncorrected and normalized (pre-paralysis values) TOF measures. These relationships were compared between sexes. RESULTS: The ability to clench teeth and head raise >5 s was lost at a significantly greater TOF ratio in males than females. The percentage decrease in handgrip strength with decreasing TOF ratio was proportionally greater in males than females. Forty per cent of the males were unable to clench the teeth at an uncorrected TOF ratio >0.9. When TOF ratios were normalized, clinical functions showed no decrement at TOF ratio >0.9 in any volunteer. CONCLUSIONS: Sex-related differences exist in the relationship between AP TOF ratio and clinical measures of muscle function used to assess recovery from neuromuscular block. Normalization of AP TOF ratios is recommended because a non-normalized TOF ratio of 0.9 does not guarantee adequate reversal of neuromuscular block.
Assuntos
Isoquinolinas/farmacologia , Bloqueio Neuromuscular/métodos , Junção Neuromuscular/efeitos dos fármacos , Fármacos Neuromusculares não Despolarizantes/farmacologia , Adulto , Deglutição/efeitos dos fármacos , Esquema de Medicação , Estimulação Elétrica/métodos , Eletromiografia/métodos , Feminino , Força da Mão , Movimentos da Cabeça/efeitos dos fármacos , Humanos , Isoquinolinas/administração & dosagem , Arcada Osseodentária/efeitos dos fármacos , Arcada Osseodentária/fisiologia , Masculino , Mivacúrio , Músculo Esquelético/efeitos dos fármacos , Músculo Esquelético/fisiologia , Junção Neuromuscular/fisiologia , Fármacos Neuromusculares não Despolarizantes/administração & dosagem , Caracteres Sexuais , Adulto JovemRESUMO
AIM: Multidrug regimens in HIV disease are associated with an increased incidence of insulin resistance, by as much as 50%. Not only does insulin resistance predisposes subjects to diabetes but also it is associated with the metabolic syndrome and increased risk of cardiovascular disease. Previous studies suggest that chromium picolinate can improve insulin resistance in patients with type 2 diabetes. The objective was to study the efficacy and safety of chromium picolinate as a treatment of insulin resistance in subjects infected with HIV. METHODS: The ability of chromium picolinate (1000 mug/day) to improve insulin sensitivity, determined with a hyperinsulinaemic-euglycaemic insulin clamp, was determined in eight HIV-positive subjects on highly active antiretroviral therapy. RESULTS: The mean rate of glucose disposal during the clamp was 4.41 mg glucose/kg lean body mass (LBM)/min (range 2.67-5.50), which increased to 6.51 mg/kg LBM/min (range 3.19-12.78, p = .03), an increase of 25% after 8 weeks of treatment with chromium picolinate. There were no significant changes in blood parameters, HIV viral burden or CD4+ lymphocytes with chromium picolinate treatment. Two subjects experienced abnormalities of liver function during the study. Another subject experienced an elevation in blood urea nitrogen. CONCLUSIONS: The study shows that chromium picolinate therapy improves insulin resistance in some HIV-positive subjects, but with some concerns about safety in this population.
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Resistência à Insulina/fisiologia , Quelantes de Ferro/uso terapêutico , Ácidos Picolínicos/uso terapêutico , Adulto , Terapia Antirretroviral de Alta Atividade/efeitos adversos , Feminino , Técnica Clamp de Glucose/instrumentação , Infecções por HIV/complicações , Infecções por HIV/tratamento farmacológico , Humanos , Masculino , Pessoa de Meia-Idade , Ácidos Picolínicos/administração & dosagem , Ácidos Picolínicos/efeitos adversos , Projetos Piloto , Resultado do TratamentoRESUMO
Individuals with a prior history of (susceptible to high altitude pulmonary edema (HAPE-S) have high resting pulmonary arterial pressures, but little data are available on their vascular response to exercise. We studied the pulmonary vascular response to exercise in seven HAPE-S and nine control subjects at sea level and at 3,810 m altitude. At each location, both normoxic (inspired PO2 = 148 Torr) and hypoxic (inspired PO2 = 91 Torr) studies were conducted. Pulmonary hemodynamic measurements included pulmonary arterial and pulmonary arterial occlusion pressures. A multiple regression analysis demonstrated that the pulmonary arterial pressure reactivity to exercise was significantly greater in the HAPE-S group. This reactivity was not influenced by altitude or oxygenation, implying that the response was intrinsic to the pulmonary circulation. Pulmonary arterial occlusion pressure reactivity to exercise was also greater in the HAPE-S group, increasing with altitude but independent of oxygenation. These findings suggest an augmented flow-dependent pulmonary vasoconstriction and/or a reduced vascular cross-sectional area in HAPE-S subjects.
Assuntos
Doença da Altitude/fisiopatologia , Altitude , Exercício Físico/fisiologia , Circulação Pulmonar/fisiologia , Edema Pulmonar/fisiopatologia , Adulto , Limiar Anaeróbio/fisiologia , Gasometria , Débito Cardíaco/fisiologia , Água Extravascular Pulmonar/fisiologia , Feminino , Hemodinâmica/fisiologia , Humanos , Masculino , Troca Gasosa Pulmonar/fisiologia , Pressão Propulsora Pulmonar/fisiologia , Capacidade VitalRESUMO
Ventilation-perfusion (VA/Q) mismatch has been shown to increase during exercise, especially in hypoxia. A possible explanation is subclinical interstitial edema due to high pulmonary capillary pressures. We hypothesized that this may be pathogenetically similar to high-altitude pulmonary edema (HAPE) so that HAPE-susceptible people with higher vascular pressures would develop more exercise-induced VA/Q mismatch. To examine this, seven healthy people with a history of HAPE and nine with similar altitude exposure but no HAPE history (control) were studied at rest and during exercise at 35, 65, and 85% of maximum 1) at sea level and then 2) after 2 days at altitude (3,810 m) breathing both normoxic (inspired Po2 = 148 Torr) and hypoxic (inspired Po2 = 91 Torr) gas at both locations. We measured cardiac output and respiratory and inert gas exchange. In both groups, VA/Q mismatch (assessed by log standard deviation of the perfusion distribution) increased with exercise. At sea level, log standard deviation of the perfusion distribution was slightly higher in the HAPE-susceptible group than in the control group during heavy exercise. At altitude, these differences disappeared. Because a history of HAPE was associated with greater exercise-induced VA/Q mismatch and higher pulmonary capillary pressures, our findings are consistent with the hypothesis that exercise-induced mismatch is due to a temporary extravascular fluid accumulation.
Assuntos
Doença da Altitude/fisiopatologia , Altitude , Exercício Físico/fisiologia , Edema Pulmonar/fisiopatologia , Relação Ventilação-Perfusão/fisiologia , Adulto , Envelhecimento/fisiologia , Doença da Altitude/sangue , Gasometria , Débito Cardíaco/fisiologia , Metabolismo Energético/fisiologia , Feminino , Hemodinâmica/fisiologia , Humanos , Ácido Láctico/sangue , Masculino , Gases Nobres , Circulação Pulmonar/fisiologia , Edema Pulmonar/sangue , Troca Gasosa Pulmonar/fisiologiaRESUMO
HYPOTHESIS: Acute severe isovolemic anemia (to a hemoglobin [Hb] concentration of 50 g/L) does not decrease subcutaneous wound tissue oxygen tension (PsqO(2)). SETTING: University hospital operating room and inpatient general clinical research center ward. SUBJECTS: Twenty-five healthy, paid volunteers. METHODS: Subcutaneous oxygen tension and subcutaneous temperature (Tsq) were measured continuously during isovolemic hemodilution to an Hb level of 50 g/L. In 14 volunteers (initially well-perfused), "normal" perfusion (Tsq >34.4 degrees C) was achieved by hydration and systemic warming prior to starting isovolemic hemodilution, while in 11 volunteers (perfusion not controlled [PNC]), no attempt was made to control perfusion prior to hemodilution. MAIN OUTCOME MEASURES: Measurements of PsqO(2), Tsq, and relative subcutaneous blood flow (flow index). RESULTS: While PsqO(2), Tsq, and flow index were significantly lower in PNC vs well-perfused subjects at baseline, there was no significant difference between them at the Hb of 50 g/L (nadir). Subcutaneous PO(2) did not decrease significantly in either group. Arterial PO(2) was not different between the groups, and did not change significantly over time; Tsq and flow index increased significantly from baseline to nadir Hb in both groups. CONCLUSIONS: The level of PsqO(2) was maintained at baseline levels during hemodilution to Hb 50 g/L in healthy volunteers, whether they were initially well-perfused or mildly underperfused peripherally. Given the significant increase in Tsq and flow index, this resulted from a compensatory increase in subcutaneous blood flow sufficient to maintain oxygen delivery. Wound healing depends to a large extent on tissue oxygen delivery, and these data suggest that even severe anemia by itself would not be sufficient to impair wound healing. Thus, transfusion of autologous packed red blood cells solely to improve healing in surgical patients with no other indication for transfusion is not supported by these results.
Assuntos
Hemodiluição , Oxigênio/metabolismo , Doença Aguda , Adulto , Anemia/metabolismo , Feminino , Humanos , Masculino , Perfusão , Índice de Gravidade de Doença , PeleRESUMO
Low extracellular pH decreases the activity of the N-methyl-D-aspartate (NMDA) glutamate receptor, and may thus limit neuronal calcium overload during cerebral ischemia. During induced hypothermia, alkaline pH ("alphastat regulation") is often used to preserve cardiac and enzymatic function. The purpose of this study is to measure the functional activity of cerebral cortex NMDA receptors over the range of temperatures used in profound hypothermic cardiopulmonary bypass (20-37 degrees C). Extracellular pH was varied over a broad range relevant to both alphastat and pH stat acid-base management (7.0-7.8). Change in cytosolic free calcium evoked by 50 microM NMDA in brain slices was used as an index of NMDA receptor activity. Cortical slices (300 microns thick) were loaded with fura-2 Aspartate Methyl for study in a fluorometer. At 37 degrees C, a change in extracellular pH from 7.1 to 7.8 increased the NMDA-evoked change in cytosolic calcium in brain slices by a factor of 4 (p < 0.05). In contrast, at 20 degrees C there was minimal effect of changing extracellular pH from 7.1 to 7.8 (27% increase). We conclude that hypothermia results in decreased pH sensitivity of the NMDA receptor. The results predict that different strategies of pH management during induced hypothermia may have limited impact on NMDA receptor-mediated processes, such as neuronal calcium overload.
Assuntos
Cálcio/metabolismo , Córtex Cerebral/fisiologia , N-Metilaspartato/farmacologia , Receptores de N-Metil-D-Aspartato/fisiologia , Trifosfato de Adenosina/metabolismo , Animais , Citosol/efeitos dos fármacos , Citosol/metabolismo , Concentração de Íons de Hidrogênio , Técnicas In Vitro , Cinética , Ratos , Ratos Sprague-Dawley , Receptores de N-Metil-D-Aspartato/efeitos dos fármacos , Análise de Regressão , TemperaturaRESUMO
Patients request health care for reasons that transcend the management of medical disease. Patients seek to create an "alliance" with the physician which "compensates" for conflict or deficit in the family system. This is particularly true for "problem," "difficult," or "hateful" patients who have significant psychosocial problems. When such a compensatory alliance evolves, it may become dysfunctional, limiting the physician's ability to make necessary medical interventions. By not explicitly including other family members, the traditional dyadic model of the doctor-patient relationship predisposes towards the formation of a compensatory alliance. The nature of the dysfunctional compensatory alliance may even remain obscure because the patient presents a distorted picture of the family situation. Therefore, to manage the compensatory alliance, the physician must perform a simple family assessment, including direct communication with other family members, early in the formation of the doctor-patient relationship. The physician should be alert to the formation of a dysfunctional compensatory alliance and the need to perform a family assessment whenever a patient explicitly or implicitly makes a request that engages the doctor with another family member. Recognition that a patient is "difficult" or awareness of a sense of helplessness, and frustration in caring for a patient may also indicate formation of a dysfunctional compensatory alliance and the need for family assessment. Recognizing key aspects of the doctor-patient-family relationship will enable the clinician to manage the compensatory alliance in a productive and therapeutic fashion. When family dysfunction requiring significant change is discovered, involvement of a family therapist should be offered.
Assuntos
Família , Relações Médico-Paciente , Relações Profissional-Família , Adolescente , Adulto , Idoso , Terapia Familiar , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Modelos Psicológicos , Gravidez , Transferência PsicológicaRESUMO
UNLABELLED: Faculty clinical time is an extremely valuable commodity. Most departments quantify faculty clinical time on an "availability" basis (e.g., number of days in the operating room or nights on call). We hypothesize that a productivity measure (i.e., determination of actual clinical care delivered rather than availability of such care) would produce different results than the availability system. The "billable hour" was chosen as the measurement device. It was defined as time that anesthesia was actually given, as obtained from the anesthetic record. After collecting data for a year, we found that despite parity using the availability system, the billable hour system detected significant differences between faculty within and between groups. We conclude that "availability" and "productivity" systems produce different conclusions regarding the relative contributions of an individual faculty or subspecialty group. IMPLICATIONS: Accountability of clinical activities by faculty is crucial to the financial status of any department of anesthesia. We hypothesized that methods of availability (e.g., amount of time scheduled for clinical activities) versus productivity measure (actual amount of clinical care delivered) would be quite different between faculty and differing subspecialty groups. Even though the availability system distributed clinical time on an equal basis, there was a wide difference of clinical productivity within and between specialty groups. We conclude that a productivity measure (i.e., billable hours) is a more accurate reflection of faculty productivity than an availability system and is more in line with departmental sources of financial income.
Assuntos
Anestesiologia , Eficiência , HumanosRESUMO
To understand the factors influencing breath-holding performance, we tested whether the hypoxic (HVR) and hypercapnic ventilatory responses (HCVR) were predictors of the extent of maximal breath-holds as measured by breath-hold duration, the lowest oxyhemoglobin saturation (SpO2min), lowest calculated PaO2 (PaO2min) and highest end-tidal PCO2 (PETCO2max) reached. Steady state isocapnic HVR and hyperoxic HCVR were measured in 17 human volunteers. Breath-holds were made at total lung capacity (TLC), at TLC following hyperventilation, at functional residual capacity, and at TLC with FIO2 = 0.15. SpO2 was measured continuously by pulse oximetry, and alveolar gas was measured at the end of breath-holds by mass spectrometry. PaO2min was calculated from SpO2min and PETCO2max. HVR was a significant predictor of both SpO2min and PaO2min. HVR and forced vital capacity were predictors of breath-hold duration by multiple linear regression. HCVR had no significant predictive value. We conclude that HVR, but not HCVR, is a significant predictor of breath-holding performance.
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Hipóxia/fisiopatologia , Respiração , Adulto , Dióxido de Carbono/análise , Dióxido de Carbono/fisiologia , Feminino , Capacidade Residual Funcional , Humanos , Hipercapnia/fisiopatologia , Masculino , Ventilação Voluntária Máxima , Oxigênio/análise , Oxigênio/sangue , Oxigênio/fisiologia , Oxiemoglobinas/análise , Oxiemoglobinas/fisiologia , Volume de Ventilação Pulmonar , Capacidade Pulmonar TotalRESUMO
BACKGROUND: Extracellular accumulation of the excitatory neurotransmitter L-glutamate during cerebral hypoxia or ischemia contributes to neuronal death. Anesthetics inhibit release of synaptic neurotransmitters but it is unknown if they alter net extrasynaptic glutamate release, which accounts for most of the glutamate released during hypoxia or ischemia. The purpose of this study was to determine if different types of anesthetics decrease hypoxia-induced glutamate release from rat brain slices. METHODS: Glutamate released from cortical brain slices was measured fluorometrically with the glutamate dehydrogenase catalyzed formation of the reduced form of nicotinamide adenine dinucleotide phosphate. Glutamate release was measured in oxygenated (PO2 = 400 mmHg), hypoxic ((PO2 = 20 mmHg), and anoxic ((PO2 = 20 mmHg plus 100 microM NaCN) solutions and with clinical concentrations of anesthetics (halothane 325 microM, enflurane 680 microM, propofol 200 microM, sodium thiopental 50 microM). The source of glutamate released during these stresses was defined with toxins inhibiting N and P type voltage-gated calcium channels, and with calcium-free medium. RESULTS: Glutamate released during hypoxia or anoxia was 1.5 and 5.3 times greater, respectively, than that evoked by depolarization with 30 mM KCl. Hypoxia/anoxia-induced glutamate release was not mediated by synaptic voltage-gated calcium channels, but probably by the reversal of normal uptake mechanisms. Halothane, enflurane, and sodium thiopental, but not propofol, decreased hypoxia-evoked glutamate release by 50-70% (P < 0.05). None of the anesthetics alter basal glutamate release. CONCLUSIONS: The authors conclude that halothane, enflurane, and sodium thiopental but not propofol, at clinical concentrations, decrease extrasynaptic release of L-glutamate during hypoxic stress.
Assuntos
Anestésicos Inalatórios/farmacologia , Anestésicos Intravenosos/farmacologia , Córtex Cerebral/metabolismo , Enflurano/farmacologia , Ácido Glutâmico/metabolismo , Halotano/farmacologia , Hipóxia/metabolismo , Propofol/farmacologia , Tiopental/farmacologia , Animais , Córtex Cerebral/efeitos dos fármacos , Técnicas In Vitro , Ratos , Ratos Sprague-DawleyRESUMO
In the present paper behaviors of mentally retarded children were recorded simultaneously on real time and time lapse video recorders. Behaviors on the time lapse recordings occurred at a rate 12 times faster than they actually occurred in real time resulting in a 92 percent reduction in the time required to score the tapes. Reliability estimates from real time and time lapse records were high and correspondence between the two methods was good. The limitations of time lapse and the feasibilities for the extended use of time lapse video recorders in behavioral and ecobehavioral assessment of mentally retarded individuals are discussed.
Assuntos
Deficiência Intelectual/psicologia , Gravação de Videoteipe/métodos , Transtorno Autístico/psicologia , Transtorno Autístico/reabilitação , Terapia Comportamental/métodos , Comportamento Infantil , Pré-Escolar , Transtornos da Alimentação e da Ingestão de Alimentos/terapia , Feminino , Humanos , Masculino , Fatores de TempoRESUMO
One-hundred forty-nine applicants to two residency programs in psychiatry were surveyed with the Opinion About Mental Illness (OMI) scale. Stepwise regression analyses showed that the place where the applicant was raised was the best predictor. In comparison to those raised abroad, those raised in the United States tend to be less authoritarian-restrictive inclined, tend to report less adherence toward an unsophisticated benevolent approach, and less adherence toward an interpersonal-etiology approach. All subjects, whether raised in the United States or not, showed similar adherence to the concepts of the mental hygiene movement.
RESUMO
BACKGROUND: Because of the rapid recovery of neuromuscular function after succinylcholine administration, there is a belief that patients will start breathing sufficiently rapidly to prevent significant oxygen desaturation. The authors tested whether this belief was valid. METHODS: Twelve healthy volunteers aged 18-45 yr participated in the study. After preoxygenation to an end-tidal oxygen concentration greater than 90%, each subject received 5 mg/kg thiopental and 1 mg/kg succinylcholine. Oxygen saturation (SaO2) was measured at both a finger and an ear lobe (beat to beat). During the period of apnea and as they were recovering, the volunteers received continuous verbal reassurance by the investigators. If the SaO2 decreased below 80%, the volunteers received chin lift and, if necessary, assisted ventilation. The length of time the subject was apneic and level of desaturation were related by linear regression analysis. One hour after recovery and again 1 week later, subjects were asked a series of questions regarding their emotional experience. RESULTS: In six volunteers, SaO2 decreased below 95% during apnea; in four, SaO2 decreased below 80%, necessitating chin lift and assisted ventilation in three. Apnea time was significantly longer in volunteers who reached SaO2 less than 80% than in those who did not (7.0+/-0.4 and 4.1+/-0.3 min, respectively), and there was a significant correlation between the length of time the subject was apneic and the magnitude of desaturation. CONCLUSIONS: Spontaneous recovery from succinylcholine-induced apnea may not occur sufficiently quickly to prevent hemoglobin desaturation in subjects whose ventilation is not assisted.
Assuntos
Apneia/induzido quimicamente , Hemoglobinas/metabolismo , Fármacos Neuromusculares Despolarizantes/farmacologia , Respiração/efeitos dos fármacos , Succinilcolina/farmacologia , Adolescente , Adulto , Apneia/sangue , Feminino , Humanos , Masculino , Oxigênio/sangueRESUMO
BACKGROUND: Epinephrine is commonly added to lidocaine solutions to increase the duration of spinal anesthesia. Despite this common usage, the effect of epinephrine on the neurotoxic potential of this anesthetic is not known. The current experiments investigated whether adding epinephrine increases functional impairment or histologic damage induced by spinal administration of lidocaine in the rat. METHODS: Eighty rats were divided into four groups to receive an intrathecal injection of normal saline containing either 5% lidocaine, 5% lidocaine with 0.2 mg/ml of epinephrine, 0.2 mg/ml of epinephrine, or normal saline alone. Animals were assessed for persistent sensory impairment using the tail-flick test administered 4 and 7 days after infusion. Animals were then killed, and the spinal cord and nerve roots were prepared for neuropathologic evaluation. RESULTS: Rats given 5% lidocaine developed persistent sensory impairment and histologic damage, and the addition of epinephrine resulted in a further significant increase in injury. Sensory function in animals given epinephrine without anesthetic was similar to baseline and did not differ from saline. Histologic changes in animals treated with epinephrine alone did not differ significantly from saline controls. CONCLUSIONS: The neurotoxicity of intrathecally administered lidocaine is increased by the addition of epinephrine. When making clinical recommendations for maximum safe intrathecal dose of this anesthetic, one may need to consider whether the solution contains epinephrine.
Assuntos
Anestésicos Locais/toxicidade , Epinefrina/toxicidade , Lidocaína/toxicidade , Medula Espinal/efeitos dos fármacos , Raquianestesia , Animais , Sinergismo Farmacológico , Masculino , Ratos , Ratos Sprague-Dawley , Tempo de Reação/efeitos dos fármacos , Medula Espinal/patologia , Medula Espinal/fisiologiaRESUMO
BACKGROUND: Transfusion guidelines recommend that clinicians assess patients for signs and symptoms of anemia before the transfusion of RBCs. However, studies of signs and symptoms associated with acute isovolemic anemia are limited. The objective of this study was to determine whether acute reduction of Hb concentration to 5 g per dL would result in fatigue, tachycardia, or hypotension in resting, young, healthy, isovolemic humans, and whether changes were reversible with RBC transfusion. STUDY DESIGN AND METHODS: Conscious, resting, healthy adults less than 35 years old (n = 8) underwent acute isovolemic hemodilution to Hb of 5 g per dL and self-scored their energy level at various Hb concentrations. Heart rate and blood pressure were also measured. For controls, measurements of each subject were made during a comparable period of rest without hemodilution. RESULTS: During acute isovolemic hemodilution, energy levels decreased progressively and were lower at Hb of 7, 6, and 5 g per dL than at baseline (p<0.01) or in control sessions (p<0.05). The energy level was lower at Hb 7 g per dL than at 14 ( p = 0.005), lower at Hb 6 g per dL than at 7 (p = 0.01), and lower at Hb 5 g per dL than at 6 (p =0.01). Energy levels rose and were not different from baseline or control levels after transfusion of all autologous RBCs. Similarly, median heart rate increased with hemodilution to Hb of 7, 6, and 5 g per dL and decreased with transfusion of autologous RBCs. Supine blood pressure did not decrease with isovolemic hemodilution. CONCLUSION: In resting, young, healthy humans, acute isovolemic anemia to Hb levels of 7, 6, and 5 g per dL results in decreased self-scored energy levels and in an increase in heart rate but not in hypotension. Changes in energy and heart rate are reversible with the transfusion of autologous RBCs.
Assuntos
Anemia/complicações , Fadiga/etiologia , Doença Aguda , Adulto , Pressão Sanguínea , Metabolismo Energético , Feminino , Frequência Cardíaca , Humanos , Masculino , Descanso/fisiologiaRESUMO
Six patients with aortic regurgitation secondary to flail aortic valve leaflet syndrome were studied echocardiographically, angiographically, surgically, and pathologically. The etiology of flail aortic leaflet was myxomatous degeneration in four patients and bacterial endocarditis in two. The echocardiographic manifestations of flail aortic valve leaflet are diastolic fluttering of the aortic cusp echoes, abnormal systolic aortic leaflet movement, and abnormal diastolic fluttering echoes in the left ventricular outflow tract. Diastolic fluttering of the aortic valve leaflets is specific echocardiographic evidence of aortic regurgitation due to flail aortic leaflets, and demonstration of diastolic fluttering of the aortic leaflets and diastolic fluttering echoes in the left ventricular outflow tracts is direct evidence of flail and prolapsed aortic leaflets.
Assuntos
Insuficiência da Valva Aórtica/diagnóstico , Ecocardiografia , Adulto , Idoso , Angiografia , Insuficiência da Valva Aórtica/diagnóstico por imagem , Insuficiência da Valva Aórtica/cirurgia , Feminino , Humanos , Masculino , Pessoa de Meia-IdadeRESUMO
BACKGROUND: Erythrocytes are transfused to prevent or treat inadequate oxygen delivery resulting from insufficient hemoglobin concentration. Previous studies failed to find evidence of inadequate systemic oxygen delivery at a hemoglobin concentration of 5 g/dl. However, in those studies, sensitive, specific measures of critical organ function were not used. This study tested the hypothesis that acute severe decreases of hemoglobin concentration alters human cognitive function. METHODS: Nine healthy volunteers, age 29 +/- 5 yr (mean +/- SD), were tested with verbal memory and standard, computerized neuropsychologic tests before and after acute isovolemic reduction of their hemoglobin to 7, 6, and 5 g/dl and again after transfusion of their autologous erythrocytes to return their hemoglobin concentration to 7 g/dl. To control for duration of the experiment, each volunteer also completed the same tests on a separate day, without alteration of hemoglobin, at times of the day approximately equivalent to those on the experimental day. RESULTS: No test showed any change in reaction time or error rate at hemoglobin concentration of 7 g/dl compared with the data at the baseline hemoglobin concentration of 14 g/dl. Reaction time, but not error rate, for horizontal addition and digit-symbol substitution test (DSST) increased at hemoglobin 6 g/dl (mean horizontal addition, 19%; 95% confidence interval [CI], 4-34%; mean DSST, 10%; 95% CI, 4-17%) and further at 5 g/dl (mean horizontal addition, 43%; 95% CI, 6-79%; mean DSST, 18%; 95% CI, 4-31%). Immediate and delayed memory was degraded at hemoglobin 5 g/dl but not at 6 g/dl. Return of hemoglobin to 7 g/dl returned all tests to baseline, except for the DSST, which significantly improved, and returned to baseline the following morning after transfusion of all autologous erythrocytes. CONCLUSION: Acute reduction of hemoglobin concentration to 7 g/dl does not produce detectable changes in human cognitive function. Further reduction of hemoglobin level to 6 and 5 g/dl produces subtle, reversible increases in reaction time and impaired immediate and delayed memory. These are the first prospective data to demonstrate subtle degraded human function with acute anemia of hemoglobin concentrations of 6 and 5 g/dl. This reversibility of these decrements with erythrocyte transfusion suggests that our model can be used to test the efficacy of erythrocytes, oxygen therapeutics, or other treatments for acute anemia.
Assuntos
Anemia/psicologia , Cognição/fisiologia , Hemoglobinas/metabolismo , Memória/fisiologia , Adulto , Anemia/sangue , Volume Sanguíneo/fisiologia , Feminino , Humanos , Masculino , Rememoração Mental/fisiologia , Desempenho Psicomotor/fisiologia , Tempo de Reação/fisiologiaRESUMO
BACKGROUND: The "critical" level of oxygen delivery (DO2) is the value below which DO2 fails to satisfy the metabolic need for oxygen. No prospective data in healthy, conscious humans define this value. The authors reduced DO2 in healthy volunteers in an attempt to determine the critical DO2. METHODS: With Institutional Review Board approval and informed consent, the authors studied eight healthy, conscious volunteers, aged 19-25 yr. Hemodynamic measurements were obtained at steady state before and after profound acute isovolemic hemodilution with 5% albumin and autologous plasma, and again at the reduced hemoglobin concentration after additional reduction of DO2 by an infusion of a beta-adrenergic antagonist, esmolol. RESULTS: Reduction of hemoglobin from 12.5+/-0.8 g/dl to 4.8+/-0.2 g/dl (mean +/- SD) increased heart rate, stroke volume index, and cardiac index, and reduced DO2 (14.0+/-2.9 to 9.9+/-20 ml O2 x kg(-1) x min(-1); all P<0.001). Oxygen consumption (VO2; 3.0+/-0.5 to 3.4+/-0.6 ml O2 x kg(-1) x min(-1); P<0.05) and plasma lactate concentration (0.50+/-0.10 to 0.62+/-0.16 mM; P<0.05; n = 7) increased slightly. Esmolol decreased heart rate, stroke volume index, and cardiac index, and further decreased DO2 (to 7.3+/-1.4 ml O2 x kg(-1) x min(-1); all P<0.01 vs. before esmolol). VO2 (3.2+/-0.6 ml O2 x kg(-1) x min(-1); P>0.05) and plasma lactate (0.66+/-0.14 mM; P>0.05) did not change further. No value of plasma lactate exceeded the normal range. CONCLUSIONS: A decrease in DO2 to 7.3+/-1.4 ml O2 x kg(-1) min(-1) in resting, healthy, conscious humans does not produce evidence of inadequate systemic oxygenation. The critical DO2 in healthy, resting, conscious humans appears to be less than this value.