RESUMEN
OBJECTIVE: To describe structural models of intermediate care units used for critically ill patients. DATA SOURCES: Three multidisciplinary units with varying structures and functions of intermediate care areas (ICAs) are described. DATA SYNTHESIS: Advantages and limitations for each of the three models are outlined. The structural models described are the conventional isolated ICA model, the parallel model, and the integrated model of ICA. CONCLUSION: Each structural model has advantages and limitations. Selection of the appropriate ICA model for an institution depends on the specific circumstances and needs of the institution. Each of the three models can facilitate improved utilization of critical care resources.
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Instituciones de Cuidados Intermedios/organización & administración , Modelos Estructurales , Enfermedad Crítica/terapia , Costos de la Atención en Salud , Humanos , Unidades de Cuidados Intensivos/organización & administración , Cuerpo Médico de Hospitales/estadística & datos numéricos , Carga de TrabajoRESUMEN
BACKGROUND: The objective of this study was to determine the individual and combined effects of pulmonary contusion and fat embolism on the hemodynamics and pulmonary pathophysiology in a canine model of acute traumatic pulmonary injury. METHODS: After a thoracotomy, twenty-one skeletally mature dogs were randomly assigned to one of three groups. Unilateral pulmonary contusion alone was produced in Group 1 (seven dogs); pulmonary contusion and fat embolism, in Group 2 (seven dogs); and fat embolism alone, in Group 3 (seven dogs). Pulmonary contusion was produced by standardized compression of the left lung with a piezoelectric force transducer. Fat embolism was produced by femoral and tibial reaming followed by pressurization of the intramedullary canals. Cardiac output, systolic blood pressure, peak airway pressure, pulmonary arterial pressure, pulmonary capillary wedge pressure, partial pressure of arterial oxygen, and partial pressure of carbon dioxide were monitored for all groups. From these data, several outcome parameters were calculated: total thoracic compliance, alveolar-arterial oxygen gradient, and ratio of partial pressure of arterial oxygen to fractional inspired oxygen concentration. All of the dogs were killed after eight hours, and tissue samples were obtained from the brain, kidneys, and lungs for histological analysis. Lung samples were assigned scores for pulmonary edema (the presence of fluid in the alveoli) and inflammation (the presence of neutrophils or hyaline membranes, or both). The percentage of the total area occupied by fat was determined. RESULTS: Pulmonary contusion alone caused a significant increase in the alveolar-arterial oxygen gradient but only after seven hours (p = 0.034). Fat embolism alone caused a significant transient decrease in systolic blood pressure (p = 0.001) and a significant transient increase in pulmonary arterial pressure (p = 0.01) and pulmonary capillary wedge pressure (p = 0.015). Fat embolism alone also caused a significant sustained decrease in the ratio of partial pressure of arterial oxygen to fractional inspired oxygen concentration (p = 0.0001) and a significant increase in the alveolar-arterial oxygen gradient (p = 0.0001). The combination of pulmonary contusion and fat embolism caused a significant transient increase in pulmonary capillary wedge pressure (p = 0.0013) as well as a significant sustained decrease in partial pressure of arterial oxygen (p = 0.0001) and a significant decrease in systolic blood pressure (p = 0.001) that lasted for an hour. Pulmonary contusion followed by fat embolism caused a significant increase in peak airway pressure (p = 0.015), alveolar-arterial oxygen gradient (p = 0.0001), and pulmonary arterial pressure (p = 0.01), and these effects persisted for five hours. Total thoracic compliance was decreased 6.4 percent by pulmonary contusion alone, 4.6 percent by fat embolism alone, and 23.5 percent by pulmonary contusion followed by fat embolism. The ratio of partial pressure of arterial oxygen to fractional inspired oxygen concentration was decreased 23.7 percent by pulmonary contusion alone, 52.3 percent by fat embolism alone, and 65.8 percent by pulmonary contusion followed by fat embolism. The mean pulmonary edema score was significantly higher with the combined injury than with either injury alone (p = 0.0001). None of the samples from the lungs demonstrated inflammation. Fat embolism combined with pulmonary contusion resulted in a significantly greater mean percentage of the area occupied by fat in the noncontused right lung than in the contused left lung (p = 0.001); however, no significant difference between the right and left lungs could be detected with fat embolism alone. The mean percentage of the glomerular and cerebral areas occupied by fat was greater with fat embolism combined with pulmonary contusion than with fat embolism alone (p = 0.0001 and p = 0.01, respectively). (ABSTRACT TRUNCATED)
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Contusiones/complicaciones , Embolia Grasa/fisiopatología , Lesión Pulmonar , Embolia Pulmonar/fisiopatología , Resistencia de las Vías Respiratorias , Animales , Presión Sanguínea , Gasto Cardíaco , Perros , Embolia Grasa/etiología , Embolia Grasa/patología , Femenino , Pulmón/patología , Rendimiento Pulmonar , Masculino , Oxígeno/sangre , Circulación Pulmonar , Embolia Pulmonar/etiología , Embolia Pulmonar/patología , Intercambio Gaseoso Pulmonar , Presión Esfenoidal PulmonarRESUMEN
PURPOSE: We examined the effect of inhaled nitric oxide (NO) on the acute pulmonary hypertension and right ventricular (RV) dilation after fat embolism. METHODS: A bilateral cemented arthroplasty (BCA), created fat embolism in 20 dogs. In Part A, 12 dogs were randomized to an NO group (n=6, inhaled NO 40 ppm before BCA and throughout the study) or a control group (n=6). In Part B, a third group of dogs (n=8) were given NO 20-40 ppm 2-3 min after BCA when pulmonary artery pressure (PAP) increased. Transesophageal echocardiography (TEE) and invasive hemodynamic monitoring evaluated the hemodynamic response to BCA. Postmortem, quantitative morphometry was used to estimate the number of fat emboli and diameter of lung vessel occluded by fat. RESULTS: Part A: The increase in PAP in the NO group (16 +/- 1 to 34 +/- 9 mmHg) within three minutes of BCA was not different from that in the control group (14 +/- 4 to 35 +/- 9 mmHg). Within three minutes of BCA, TEE demonstrated RV dilation in all groups (P < 0.05) but there was no difference in the change in RV area in the NO and control groups. When NO was given after BCA, no difference in PAP or RV dilation was noted from that in the control group. There were no differences, at post mortem, between the groups in the diameter of lung vessel occluded by fat CONCLUSION: Whether given before the embolic insult or two to three minutes after the onset of pulmonary hypertension, inhaled NO did not attenuate the acute pulmonary hypertension or RV dilation after cemented arthroplasty.
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Artroplastia , Cementos para Huesos , Embolia Grasa/complicaciones , Hipertensión Pulmonar/prevención & control , Hipertrofia Ventricular Derecha/prevención & control , Óxido Nítrico/uso terapéutico , Embolia Pulmonar/complicaciones , Vasodilatadores/uso terapéutico , Administración por Inhalación , Animales , Artroplastia/efectos adversos , Presión Sanguínea/efectos de los fármacos , Presión Sanguínea/fisiología , Cementos para Huesos/efectos adversos , Perros , Ecocardiografía Transesofágica , Embolia Grasa/patología , Hemodinámica/efectos de los fármacos , Hemodinámica/fisiología , Hipertensión Pulmonar/diagnóstico por imagen , Hipertensión Pulmonar/etiología , Hipertrofia Ventricular Derecha/diagnóstico por imagen , Hipertrofia Ventricular Derecha/etiología , Óxido Nítrico/administración & dosificación , Arteria Pulmonar , Embolia Pulmonar/patología , Distribución Aleatoria , Vasodilatadores/administración & dosificaciónRESUMEN
BACKGROUND: The potential to produce fat embolism may be important in determining the ideal method and timing of fracture treatment in patients with preexisting lung injury. METHODS: Four dogs underwent femoral and tibial canal reaming and pressurization. Blood gas samples were analyzed, and pulmonary arterial pressure was monitored at 1 and 72 hours. Animals were killed 72 hours postoperatively, and the lungs, kidneys, and brain were examined histologically and compared with equivalent specimens from four control dogs that had not undergone femoral and tibial canal reaming and pressurization. RESULTS: Postmortem, intravascular fat persisted for 72 hours after induction of pulmonary fat embolism. Mean PaO2 was unchanged from baseline at 72 hours after canal pressurization. Canal pressurization caused a sustained increase in pulmonary arterial pressure (p=0.02) for 1 hour after canal pressurization. The mean pulmonary edema score at 72 hours was 29+/-3. Only a scant polymorph infiltrate (zero to two polymorphs per high-power field) was present at any time. No hyaline membranes were seen at any time. The percentage area occupied by intravascular fat in the lungs was 0.0214+/-0.0058 at 72 hours. No signs of ischemia or inflammation were seen in either the cerebral or the renal specimens. CONCLUSION: This study is the first to show that intravascular fat persists in the lungs, kidneys, and brain for 72 hours after canal pressurization and, by itself, does not cause pathologic evidence of acute inflammation.
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Embolia Grasa/patología , Fémur/cirugía , Enfermedades Pulmonares/patología , Pulmón/patología , Tibia/cirugía , Animales , Médula Ósea , Encéfalo/patología , Perros , Embolia Grasa/fisiopatología , Hemodinámica , Riñón/patología , Enfermedades Pulmonares/fisiopatología , PresiónRESUMEN
UNLABELLED: Fat-embolism syndrome and pulmonary dysfunction may develop in multiply injured patients who have a fracture of a long bone. Although early fixation of a fracture is beneficial, intramedullary nailing may exacerbate pulmonary dysfunction by causing additional embolization of marrow fat. We examined the pulmonary effects of the timing and method of fixation of a fracture in a canine fat-embolism model. Fat embolism was induced in forty-one adult dogs by reaming the ipsilateral femur and tibia followed by pressurization of the intramedullary canal. The animals were divided into a control group of eight dogs that had induction of fat embolism alone and an experimental group of thirty-three dogs that had induction of fat embolism and internal fixation of a transverse fracture of the middle of the contralateral femoral shaft. In the control group, four dogs each were killed four hours and twenty-four hours after induction of fat embolism. In the experimental group, a femoral fracture was created and fixation was performed four hours after embolic showering in fifteen animals and twenty-four hours after embolization in eighteen animals. The two experimental groups were subdivided according to the method of fixation of the fracture: eleven dogs each had application of a plate, nailing without reaming, and nailing with reaming. The pulmonary arterial pressure and the alveolar-arterial gradient were measured preoperatively, during induction of fat embolism, and as long as one hour after fixation of the fracture but before the animal was killed. The lungs, brain, and kidneys were examined for pathological and physiological evidence of intravascular fat. The intravascular fat persisted for twenty-four hours after induction of pulmonary fat embolism. Pulmonary arterial pressure remained elevated at four hours after the embolic showering, before creation and fixation of the fracture. By twenty-four hours after the induction of fat embolism, pulmonary arterial pressure had returned to the baseline level. Neither the creation nor the fixation of the fracture affected pulmonary arterial pressure. In the animals that had fixation of a fracture four hours after embolization, both nailing with reaming and nailing without reaming produced alveolar-arterial gradients that were higher than the baseline values, whereas fixation with a plate did not change the alveolar-arterial gradient significantly from the baseline value. In addition, the alveolar-arterial gradients in the animals that had nailing with reaming and nailing without reaming four hours after embolization were, respectively, four and 3.5 times higher than that in the animals that had fixation of the femur with a plate. In the animals that had fixation twenty-four hours after embolization, none of the methods for fixation affected the alveolar-arterial gradient. The amount of embolic fat in the lungs, brain, and kidneys was not affected by fixation of the fracture when it was performed at either the four-hour or the twenty-four-hour time-interval. Scores for pulmonary edema were increased by fixation of the fracture, but there was no difference among the scores associated with the three methods of fixation. CLINICAL RELEVANCE: The findings of the present study indicated that the amount of intravascular fat persisting in the lungs, kidneys, and brain twenty-four hours after pressurization of the intramedullary canal is not affected by the method of fixation of the fracture. Fixation of a fracture is associated with minimum evidence of acute inflammation and has no effect on pulmonary artery pressure. The development of pulmonary dysfunction from fat emboli depends on other factors, not just on the presence of fat in pulmonary vessels. It appears that the method of fracture fixation has little influence on the outcome of treatment.
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Placas Óseas/efectos adversos , Embolia Grasa/etiología , Fijación Intramedular de Fracturas/efectos adversos , Fracturas Óseas/terapia , Embolia Pulmonar/etiología , Animales , Perros , Fracturas Óseas/complicaciones , Hipertensión Pulmonar/etiología , Metilmetacrilato , Metilmetacrilatos/análisis , Edema Pulmonar/etiologíaRESUMEN
PURPOSE: Pressurisation of the medullary cavity during cemented arthroplasty causes "intravasation" of marrow fat. The purpose of this study was to examine the relationship between the amount of pulmonary intravascular fat and the haemodynamic and echocardiographic changes. METHODS: Anaesthetised mongrel dogs (n = 16) underwent bilateral cemented arthroplasty (BCA) to create a large embolic load. Haemodynamic measurements included blood pressure (BP), pulmonary artery pressure (PAP), right atrial pressure and cardiac output as well as transoesophageal echocardiographic (TEE) assessment of right ventricular (RV) and left ventricular (LV) areas. Using quantitative morphometry on postmortem lung specimens, the proportion of lung tissue occluded by fat was measured. RESULTS: Mean BP decreased within one minute of BCA, coinciding with the appearance of echogenic material in the RV. The RV area increased by 56% (P < 0.05) and LV area decreased by 34% (P < 0.05) while PAP increased from 15 +/- 3 mmHg to 39 +/- 10 mmHg within one minute (P < 0.001). The PAP remained elevated throughout the study (30 min). Stroke volume decreased in 14/15 dogs, yet cardiac output was maintained by increased heart rate. There was a curvilinear relationship (r = 0.87) between the maximum increase in PAP and the proportion of lung occupied by fat. CONCLUSION: In this model, stroke volume decreased within one minute of BCA when fat embolism accompanied prosthesis insertion. The TEE detected an increased RV area and reduced LV area associated with decreased stroke volume. The maintenance of cardiac output after intraoperative fat embolism depends primarily on the ability to increase heart rate.
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Artroplastia , Ecocardiografía Transesofágica , Embolia Grasa/fisiopatología , Hemodinámica/fisiología , Animales , Presión Sanguínea/fisiología , Perros , Mediciones del Volumen Pulmonar , Arteria Pulmonar/fisiología , Circulación Pulmonar/fisiología , Volumen Sistólico/fisiología , Función VentricularAsunto(s)
Anestesiología , Evaluación de la Tecnología Biomédica , Anestesiología/instrumentación , Anestesiología/métodos , Anestesiología/tendencias , Canadá , Predicción , Humanos , Evaluación de la Tecnología Biomédica/legislación & jurisprudencia , Evaluación de la Tecnología Biomédica/métodos , Evaluación de la Tecnología Biomédica/tendenciasRESUMEN
PURPOSE: To determine which factors influence the clinician in choosing critical care admission and postoperative ventilation, we prospectively examined the incidence, timing, causes, and risk factors for admission to critical care for postoperative ventilation within 48 hr of a surgical procedure (excluding cardiac and neurosurgical). METHODS: Patients were categorized as: admission planned preoperatively; admission unplanned and identified in the OR (Operating Room) or PACU (Post Anaesthetic Care Unit); and admission unplanned, identified after PACU discharge. Rates of admission by category for those with specific preoperative and intraoperative characteristics were compared to those without the characteristics to determine risk factors for admission (P < 0.01). RESULTS: Only 329 of 15,059 cases (2.2%) had a critical care admission. Of these, 288 were planned, 31 identified in the OR or PACU, and 10 after PACU discharge. A respiratory aetiology was the reason for admission in 75% of unplanned cases. Preoperatively, age > or = 60 yr and common systemic illnesses (cardiac, renal, pulmonary) were markers for planned admission, but only positive HIV status was a risk factor for unplanned admission. The two main physiological features which identified all critical care admissions were haemoglobin oxygen saturation < 90% (preoperatively breathing room air and intraoperatively) and tachycardia during the operative period. Six of ten of the unplanned after PACU discharge patients underwent bronchoscopy with a neurolept analgesic technique. CONCLUSION: Postoperative admissions to a critical care unit, both planned and unplanned, are uncommon. This study has identified haemoglobin oxygen desaturation during the perioperative period and intraoperative tachycardia as important markers for all admissions to critical care.
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Cuidados Críticos , Complicaciones Posoperatorias , Respiración Artificial , Adulto , Anciano , Anestesia , Femenino , Humanos , Masculino , Persona de Mediana Edad , Admisión del Paciente , Estudios ProspectivosRESUMEN
Haemodynamic changes during bilateral cemented arthroplasty (BCA) were compared in dogs anaesthetized with isoflurane/N2O (ISOF) or diazepam/fentanyl (100 microg x kg(-1))N2O(FENT). Eight animals were anaesthetized with each regimen. After establishing monitoring and recording baseline values, BCA was performed. Haemodynamic measurements included aortic blood pressure (ABP), pulmonary artery pressure (PAP), right and left atrial pressures, and cardiac output. These were recorded at 30, 60, 180 and 300 sec after BCA. Lungs were removed and examined postmortem using quantitative morphometry. Groups demonstrated similar increases in PAP (ISOF 15 +/- 2 to 32 +/- 7, FENT 19 +/- 4 to 38 +/- 13; P> 0.05 between groups, P< 0.05 vs baseline). The proportion of lung vasculature occluded by fat was not different between groups (ISOF 9.63 +/- 3.38%, FENT 8.85 +/- 2.20%). Stroke volume decreased similarly in both groups (P> 0,05 between groups, P< 0.05 vs baseline). However, ABP decreased within one minute of BCA in ISOF (111 +/- 17 to 55 +/- mmHg, P< 0.05 and two of eight dogs died. All FENT dogs survived and hypotension (118 +/- 20 to 102 +/- 24 mmHg) was transient and less severe (P< 0.05 vs ISOF). Increased heart rate (HR) was noted in FENT following BCA (73 +/- 8 to 108 +/- 25 beats x min(-1); P< 0.05). Baseline HR was higher in ISOF (P< 0.05) and no increase in HR was noted. Systemic vascular resistance decreased in ISOF (P< 0.05), but not FENT (P> 0.05 vs baseline, P< 0.05 vs ISOF). To assess the role of slower baseline HR in FENT (73 +/-8) versus ISOF (131 +/- 5), six FENT dogs were paced (130 beats x min(-1)) with epicardial leads and an AV sequential pulse generator to simulate the ISOF group's baseline HR. Haemodynamic stability was maintained in this group in spite of a more rapid baseline HR. The choice of anaesthetic regimen strongly influenced acute haemodynamic changes in response to BCA.
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Anestésicos por Inhalación/farmacología , Anestésicos Intravenosos/farmacología , Artroplastia , Fentanilo/farmacología , Isoflurano/farmacología , Animales , Catecolaminas/sangre , Perros , Hemodinámica/efectos de los fármacosRESUMEN
OBJECTIVES: To evaluate the ability of the acute Physiology and Chronic Health Evaluation II (APACHE II) scoring system to predict patient outcome in two Canadian intensive care units (ICUs). To compare the severity of illness and outcome of Canadian ICU patients with existing United States data. DESIGN: Prospective data collection on 1,724 Canadian ICU patients for validation of the APACHE II system. Comparison of the outcome of Canadian ICU patients to retrospective United States data on 4,087 patients from the 1985 APACHE II multicenter study. SETTING: Canadian data from two university teaching hospital ICUs. United States data from 13 ICUs, ten of which were in university teaching hospitals. PATIENTS: Consecutive patients admitted to adult medical/surgical ICUs. Coronary care unit, neurosurgical and cardiac surgery patients were excluded. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: For each patient, demographic data, diagnosis, APACHE II score and hospital survival data were collected. The predicted risk of death was calculated for each patient using the APACHE II risk of death equation. The accuracy in outcome prediction of the APACHE II system was assessed by means of the receiver operating characteristic curve, 2 x 2 decision matrices and linear regression analysis. The severity of illness and hospital mortality for the Canadian patients was compared with that of United States patients from the 1985 APACHE II multicenter study. In 1,724 Canadian ICU patients, the mean +/- SEM APACHE II score was 16.5 +/- 0.2. The predicted death rate was 24.7% and the observed death rate was 24.8%. Using receiver operating curve analysis, good correlation was found between predicted outcome and observed outcome. The area under the curve was 0.86. From the 2 x 2 decision matrix constructed for a predicted risk of death of 0.5, 83% of patients were correctly classified. The sensitivity was 50.9% and the specificity was 93.6%. When observed death rate was plotted against predicted death rate, linear regression analysis gave an r2 of .99. Canadian patients had a higher death rate and APACHE II score than the United States patients. After controlling for severity of illness using the APACHE II score, the Canadian and United States death rates were similar. CONCLUSIONS: The ability of the APACHE II system in predicting group outcome is validated in this Canadian ICU population by receiver operating characteristic curve, 2 x 2 decision matrices and linear regression analysis. The Canadian patients had a higher overall hospital death rate than the United States patients. After controlling for severity of illness using APACHE II scores, the hospital death rate was comparable between the Canadian and United States patients.
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APACHE , Cuidados Críticos/estadística & datos numéricos , Evaluación de Resultado en la Atención de Salud/estadística & datos numéricos , Canadá , Distribución de Chi-Cuadrado , Mortalidad Hospitalaria , Hospitales Universitarios/estadística & datos numéricos , Humanos , Modelos Lineales , Persona de Mediana Edad , Pronóstico , Estudios Prospectivos , Curva ROC , Estudios Retrospectivos , Sensibilidad y Especificidad , Sobrevivientes/estadística & datos numéricos , Estados UnidosRESUMEN
Specific factors have limited the interpretation of studies regarding the efficacy, effectiveness and efficiency of technology in anaesthesia. Some of these problems are reviewed, including the lack of specific outcomes necessitating the use of intermediate measures (e.g., hypoxaemia, myocardial ischaemia), which are not necessarily related to ultimate patient outcomes. This emphasizes the need for anaesthesia investigators to define fundamental issues specifically and design studies accordingly. With respect to anaesthesia monitors, the "lead time" or early warning provided by a monitor relative to that required to alter therapy effectively needs to be defined better and compared with the "lead time" without the monitor. After defining the benefit of a monitor, investigators should analyze the cost relative to alternatives (cost-benefit and cost-effectiveness). A hierarchical model to guide technology assessment is presented that addresses in order, the scientific basis of the technology, and the influence on the patient followed by societal issues. Anaesthetists have relied on traditional methods of technology assessment adopted from other disciplines. These methodologies do not address specific issues related to anaesthesia practice (such as "lead time"). In defining problems specific to the specialty of anaesthesia, new outcome measures that focus on the human factors related to decision-making in the operating room need to be developed. Future evaluations of anaesthesia technology require innovative approaches that address specific anaesthesia-related problems. One such approach is the use of simulation-based studies of response patterns to critical incidents.
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Anestesiología/instrumentación , Monitoreo Intraoperatorio/instrumentación , Evaluación de la Tecnología Biomédica , Anestesiología/economía , Anestesiología/tendencias , Análisis Costo-Beneficio , Predicción , Humanos , Monitoreo Intraoperatorio/economía , Monitoreo Intraoperatorio/tendencias , Evaluación de Resultado en la Atención de Salud , Terminología como AsuntoRESUMEN
We investigated the source of intravascular fat in systemic organs (brain, heart, and kidney) after massive pulmonary fat embolism during cemented arthroplasty. We used a bilateral cemented arthroplasty (BCA) in anesthetized mongrel dogs that simulates a cemented total-hip replacement procedure. We hypothesized that deformable fat globules could pass through the lung vasculature under high pulmonary artery pressure (Ppa). Using quantitative morphometry, we showed that the size of pulmonary vessel occluded by fat decreased from 12.8 +/- 15.2 microns 1 min after BCA to 4.9 +/- 5.1 microns at 120 min after BCA (p < 0.01). Ultrastructural studies demonstrated no evidence of acute inflammation around fat-occluded pulmonary vessels 3 h after BCA. Intravascular fat was found in all brain, heart, and kidney specimens examined 3 h after BCA (n = 6). No anesthetized animal in the "sham" (no BCA) group (n = 3) had intravascular fat at the same time period. Radiolabeled microspheres (15 microns diameter) did not reach the systemic circulation (< 1% nonentrapment) under the high Ppa after BCA. No patent foramen ovale was found in any dog at postmortem examination. We conclude that fat globules can traverse the pulmonary circulation within 3 h of orthopedic surgery. The difference between solid microspheres and fat in transpulmonary passage suggests that the composition, perhaps the deformability, of embolic material influences the lung's filtering capacity.