Decreased nitric oxide products in the urine of patients undergoing cardiac surgery.

OBJECTIVE: Renal vasoconstriction has been blamed as a cause of perioperative renal dysfunction after cardiac surgery. Endothelial function is a critical determinant of vascular tonus, including vasoconstriction. The objective of this study was to establish whether the release of the endothelial vasodilator nitric oxide (NO) or NO products is altered in patients undergoing surgery with cardiopulmonary bypass in 3 different clinical conditions. DESIGN: Observational and randomized prospective study. SETTING: University hospital. PARTICIPANTS: Adults and pediatric patients undergoing elective cardiac surgery with cardiopulmonary bypass. INTERVENTIONS: Three groups of patients were studied: group 1, 10 patients undergoing elective coronary artery surgery; group 2, 20 patients undergoing elective coronary artery surgery randomized to 2 hematocrit values during cardiopulmonary bypass, high (27%) and low (23%); and group 3, 10 pediatric patients undergoing surgical repair of noncyanotic cardiac defects. MEASUREMENTS AND MAIN RESULTS: NO products (NO2 + NO3) and cyclic guanosine monophosphate (cGMP) in urine were measured before, during hypo- and normothermic cardiopulmonary bypass, and 1 hour postoperatively. Filtration fraction was calculated. The glomerular filtration rate and effective renal plasma flow were measured with inulin and (131)I-hippuran clearances, respectively. Urinary alpha glutathione s-transferase was measured pre- and postoperatively in groups 1 and 3. NO products, as well as cGMP, decreased significantly during hypo- and normothermic cardiopulmonary bypass in all groups. This was not because of urine dilution or the degree of hemodilution. Age did not appear to alter this response. Filtration fraction decreased during cardiopulmonary bypass. Alpha glutathione s-transferase was normal pre-and postoperatively. CONCLUSIONS: Cardiac surgery with cardiopulmonary bypass is associated with a significant decrease of NO products. In the absence of kidney damage, decreased NO products could represent a physiologic response to cardiopulmonary bypass; however, endothelial dysfunction cannot be excluded.

[Renal function during cardiac surgery with extracorporeal circulation]. / Función renal en cirugía cardíaca con circulación extracorpórea: Pacientes valvulares y coronarios.

BACKGROUND: Patients with valvular heart disease are at high risk of acute renal failure after surgery with extracorporeal circulation. AIM: To describe changes in renal function parameters during surgery with extracorporeal circulation in patients with valvular heart disease and compare them with those found in patients undergoing elective coronary surgery. MATERIAL AND METHODS: Two groups of patients were studied. Group 1 was composed by twelve patients undergoing elective coronary surgery and group 2 was composed by eleven patients undergoing surgery for heart valve replacement. Glomerular filtration rate and effective renal plasma now were estimated from inulin and the 131 I-hippuran clearance respectively, at five different times, during surgery and the postoperative period. Sodium filtration fraction and fractional excretion were calculated. Alpha and pi-glutathione s-transferase in urine were measured as markers of tubular damage in the pre and postoperative periods. RESULTS: Effective renal plasma flow was reduced in both groups before induction of anesthesia, did not change during surgery and decreased significantly in patients with valvular disease in the postoperative period. Glomerular filtration rates were normal during all the study period. There was a non significant reduction of filtration fraction during extracorporeal circulation. Alpha and pi glutathione s-transferases were normal and did not change. Fractional excretion of sodium increased significantly postoperatively. CONCLUSIONS: In patients with valvular disease undergoing surgery with extracorporeal circulation, renal function does not deteriorate. No significant difference was found when compared with patients undergoing coronary surgery. No evidence of functional and cellular renal disfunction or damage was found in both study groups.

Función renal en cirugía cardíaca con circulación extracorpórea: Pacientes valvulares y coronarios / Renal function during cardiac surgery with extracorporeal circulation

Background: Patients with valvular heart disease are at high risk of acute renal failure after surgery with extracorporeal circulation. Aim: To describe changes in renal function parameters during surgery with extracorporeal circulation in patients with valvular heart disease and compare them with those found in patients undergoing elective coronary surgery Material and Methods: Two groups of patients were studied. Group 1 was composed by twelve patients undergoing elective coronary surgery and group 2 was composed by eleven patients undergoing surgery for heart valve replacement. Glomerular filtration rate and effective renal plasma now were estimated from inulin and the 131 I-hippuran clearance respectively, at five different times, during surgery and the postoperative period. Sodium filtration fraction and fractional excretion were calculated. Alpha and pi-glutathione s-transferase in urine were measured as markers of tubular damage in the pre and postoperative periods. Results: Effective renal plasma flow was reduced in both groups before induction of anesthesia, did not change during surgery and decreased significantly in patients with valvular disease in the postoperative period. Glomerular filtration rates were normal during all the study period. There was a non significant reduction of filtration fraction during extracorporeal circulation. Alpha and pi glutathione s-transferases were normal and did not change. Fractional excretion of sodium increased significantly postoperatively Conclusions: In patients with valvular disease undergoing surgery with extracorporeal circulation, renal function does not deteriorate. No significant difference was found when compared with patients undergoing coronary surgery. No evidence of functional and cellular renal disfunction or damage was found in both study groups.

Renal function and cardiopulmonary bypass in pediatric cardiac surgical patients.

We studied prospectively the perioperative changes of renal function in nine children undergoing cardiac surgery with cardiopulmonary bypass (CPB). Glomerular filtration rate (GFR) and effective renal plasma flow (ERPF) were measured with inulin and (131)I-hippuran clearances before CPB, during hypo and normothermic CPB, following sternal closure and 1 h postoperatively. Urinary alpha glutathione S-transferase (alpha GS-T) was measured pre- and postoperatively as a marker for tubular cellular damage. Plasma and urine creatinine and electrolytes were measured. Free water, osmolal and creatinine clearances, as well as fractional excretion of sodium (FeNa) and potassium transtubular gradient (TTKG) were calculated. GFR was normal before and after surgery. ERPF was low before and after surgery; it increased significantly immediately after CPB. Filtration fraction (FF) was abnormally elevated before and after surgery; however, a significant decrease during normothermic CPB and sternal closure was found. Alpha GS-T presented a moderate, but nonsignificant increase postoperatively. FeNa also increased in this period, but not significantly. Creatinine, osmolal, free water clearances, as well as TTKG, were normal in all patients pre- and postoperatively. We conclude that there is no evidence of clinically significant deterioration of renal function in children undergoing repair of cardiac lesions under CPB. Minor increases of alpha GS-T in urine postoperatively did not confirm cellular tubular damage. There was no tubular dysfunction at that time.

[Abdominal aortic aneurysms in patients over 80 years of age: conventional surgical treatment in 80 consecutive cases]. / Aneurisma aórtico abdominal en pacientes mayores de 80 años: tratamiento quirúrgico convencional en 80 casos consecutivos.

BACKGROUND: Abdominal aortic aneurysms (AAA) may be lethal unless appropriately and timely treated. Since age is a surgical risk, octogenarians are usually not considered as candidates for surgical intervention. AIM: To asses surgical complications and mortality in octogenarians treated for AAA. SUBJECTS AND METHODS: Patients aged 80 years older, treated consecutively between 1984-2001 were retrospectively analyzed. RESULTS: Sixty one patients were male, and their age ranged from 80 to 95 years. All were treated with open surgery. The operation was elective in 58 and as an emergency in 22 patients (symptomatic or ruptured AAA). Aortic diameter was 6.8 +/- 1.4 cm in asymptomatic patients and 7.7 +/- 1.8 cm in emergency cases (p = 0.024). Thirty days postoperative mortality was 5.1% in elective surgery compared to 40.6% in emergency operations (p < 0.01). Five years survival rate was 44.7% in asymptomatic patients compared to 10.4% in the emergency cases (p < 0.023). CONCLUSIONS: Elective surgery for asymptomatic AAA can be performed with low operative mortality in octogenarians. However, surgery in emergency cases has an 8 fold increase in risk. Accordingly, octogenarian patients should be considered for elective AAA repair in a selective basis.

[A 36 years experience with implantable pacemakers. A historical analysis]. / Experiencia de 36 años con marcapasos implantables. Un análisis histórico.

BACKGROUND: The implantation of pacemakers improves cardiac function and quality of life, in particular with dual chamber DDD and DDDR modes. AIM: To evaluate our clinical experience and results on pacemaker implantation, from 1963 to 1998. MATERIAL AND METHODS: Computerized data collected from 2,445 consecutive paced patients was reviewed. A total of 3,554 operative procedures were performed, including 412 procedures for complications and 697 pacemaker replacement. Patient survival was determined from clinical records, inquiry to pacemaker manufacturers and death certificates from Servicio de Registro Civil e Identificación de Chile (Chilean Civil and Identification Registry). RESULTS: Use of dual chamber (DDD and DDDR) pacemakers increased progressively up to 74% from 1988 to 1998. Complication rate was 42% in the 1963-1976 study period, it decreased to 10.6% in the 1977-1987 study period, and to 5.6% by 1988-1998. Only two patients died during surgery in the study period (0.08%). In the 1977-1987 period, pacemakers lasted 10.6 years. Survival rates were 52% at ten years, 33% at 15 years, and 21% at 20 years, with a median survival of 11.7 years, and 7.24 years in patients over 80 years old. CONCLUSIONS: Transvenous permanent pacing can be accomplished today with a low complication rate, mainly due to better technology and surgical procedures.

Experiencia de 36 años con marcapasos implantables: un análisis histórico / A 36 year experience with implantable pacemakers

Background: The implantation of pacemakers improves cardiac function and quality of life, in particular with dual chamber DDD and DDDR modes. Aim: To evaluate our clinical experience and results on pacemaker implantation, from 1963 to 1998. Material and methods: Computerized data collected from 2,445 consecutive paced patients was reviewed. A total of 3,554 operative procedures were performed, including 412 procedures for complications and 697 pacemaker replacement. Patient survival was determined from clinical records, inquiry to pacemaker manufacturers and death certificates from Servicio de Registro Civil e Identificaci-n de Chile (Chilean Civil and Identification Registry). Results: Use of dual chamber (DDD and DDDR) pacemakers increased progressively up to 74 percent from 1988 to 1998. Complication rate was 42 percent in the 1963-1976 study period, it decreased to 10.6 percent in the 1977-1987 study period, and to 5.6 percent by 1988-1998. Only two patients died during surgery in the study period (0.08 percent). In the 1977-1987 period, pacemakers lasted 10.6 years. Survival rates were 52 percent at ten years, 33 percent at 15 years, and 21 percent at 20 years, with a median survival of 11.7 years, and 7.24 years in patients over 80 years old. Conclusions: Transvenous permanent pacing can be accomplished today with a low complication rate, mainly due to better technology and surgical procedures

Endarterectomía carotídea bajo anestesia regional: experiencia inicial / Carotid endarterectomy under regional anesthesia: initial experience

Background: Endarterectomy is the treatment of choice for internal carotid artery critical stenosis. Some authors have proposed that the use of regional anesthesia has advantages over general anesthesia. Aim: To report our initial experience with carotid endarterectomy under regional anesthesia. Patients and methods: Between 1998 and 1999, patients with critical carotid artery stenosis, asymptomatic or with transient and recovered symptoms, were selected. A C2, C3, C4 root deep cervical block and superficial block was performed, using a mixture of lidocaine and bupivacaine. A carotid endarterectomy with patch and without routine shunt insertion, with standard and neurological monitoring, was performed. Results: During the study period, 94 carotid endarterectomies were done, 22 under regional anesthesia in 21 patients (12 male, age range 58-90 years old). Ninety five percent had hypertension, 52 percent smoked and 38 percent had renal dysfunction. One patient was converted to general anesthesia. Seventeen patients were discharged within 48 hours of the procedure and the rest, within 72 hours. There was no mortality or complications. Conclusions: Endarterectomy under regional anesthesia is less invasive, has excellent results and is well accepted by patients

Opioides y sistema inmune / Opioids and the immune system

The immune response is partly regulated by the nervous system, that involves endogenous opioids, stimulating or depressing immune responses. Opioids modulate immune response by indirect and direct mechanisms. Indirect modulation occurs when the activation of opioid receptors within the nervous system modifies the activity of neuroendocrine axes or neurotransmission pathways. Direct modulation results from the effects of opioids on immune system cells. This requires the expression of membrane opioid receptors in these cells. Immunomodulating effects of morphine would be a result of the integration of indirect and direct effects. In animal models, morphine transiently depresses cellular and humoral immunity. In humans, morphine has similar effects; however, the real impact of morphine administration on the immune response in clinical situations in not yet known

A model of internal control may improve the response time of an automatic arterial pressure controller

A simplified model for the arterial pressure control system was implemented on a personal computer using Matlab Simulink. Model responsees to variations of systemic vascular resistance were comparable to those predicted by physiology. Computer simulation suggested that including this model of the internal pressure control system within the design of an external controller would achieve better arterial pressure control and faster response than previous systems.

Mecanismo de acción de los anestésicos generales: ¿efecto sobre proteínas de canales iónicos o sobre fosfolípidos de membrana? / Mechanism of action of general anesthetics: effects on ionic channel proteins or on membrane phospholipids?

General anesthesia is defined by reversible unconsciousness, lack of response to noxious stimuli, and amnesia, induced by chemical agents. Mechanisms underlying the anesthetic effect are not known. The most prevalent belief was that anesthetic drugs acted on the lipid cell membranes, based on the correlation between oil solubility and anesthetic potency. Later, it has been proposed that anesthetic agents act on specific proteins of the cellular membrane of neurons. Voltage-gated ionic channels are inhibited by anesthetic agents, being some subtypes more sensitive. Clinical concentration of anesthetic agents inhibit or stimulate excitatory or inhibitory neurotransmitter receptors, respectively. Specific receptor agonists and antagonists modify this effect. Intercellular channels (gap junctions) are also affected by anesthetic agents through direct interaction with some of their protein subunits. Thus, anesthesia would result from combined effects on specific proteins acting on neural cell excitability as well as transmission and propagation of nerve impulses

Efecto de hemodilución y drogas vasoactivas sobre la presión crítica de cierre / Effect of hemodilution and vasoactive agents on the critical closing pressure

La presión crítica de cierre se atribuye a colapso microvascular, debido a vasoconstricción o a presión perivascular elevada. Las características físicas no newtonianas de la sangre podrían ser también importantes. Para establecer si cambios de la viscosidad sanguínea afectan a la presión crítica, se estudió el efecto de hemodilución aguda normovolémica. Se usaron once perros anestesiados con pentobarbital y ventilados mecánicamente, a los cuales se midió presión arterial central y péríférica con catéteres Millar, y flujo mediante transductor electromagnético en aorta proximal. La presión crítica de cierre se midió por extrapolación del decaimiento exponencial de la presión atierial luego de ocluir la aorta por 3 segundos. Se realizaron mediciones control y luego de administrar fenilefrina y nitroprusiato. Luego se realizó hemodilución sustituyendo 30 a 35 ml/kg de sangre con suero fisiológico, disminuyendo el microhematocrito desde 39 ñ 11 por ciento a 26 ñ 5 por ciento. Luego se repitieron las mediciones y las drogas vasoactivas. Fenilefrina aumentó y nitroprusiato disminuyó la presión crítica de cierre, antes y después de hemodilución. La presión crítica disminuyó con la hemodilución de 44 ñ 8 a 35 ñ 7 mmhg (p<0,05). El gasto cardíaco promedío aumentó 70 por ciento, con disminución proporcional de la resistencia vascular. La disminución de la presión crítica de cierre frente a la hemodilución aguda normovolémica sugiere que ésta resulta en parte de las características físicas de la sangre. Sin, embargo, cambios de tono vascular también la afectan, por lo que su origen es probablemente multifactorial

Un sistema de alarmas inteligentes para vigilancia continua durante cirugía y postoperatorio cardiovascular / An intelligent system of alarm for continuous monitoring during cardiac surgery and postoperative intensive care

Se presenta un sistema experto capaz de integrar la información de siete variables fisiológicas de pacientes en cirugía y postoperatorio cardiovascular. El sistema está basado en lógica difusa y funciona bajo condiciones de información ruidosa o incompleta. El estado del paciente es estimado por medio de análisis simultáneo de las variables e integración de ellas. Las alarmas son reportadas en forma unificada por medio de un mensaje escrito en la pantalla. El sistema fue implementado en un computador personal para vigilancia continua y simultánea de hasta 9 pacientes. El sistema fue comparado con monitores convencionales (SpaceLabsTM PC2) en 20 cirugías cardíacas. Las alarmas reportadas por cada sistema fueron registradas por dos observadores expertos (un médico, un ingeniero) y clasificadas como verdaderas o falsas. Un 75 por ciento de las alarmas reportadas por los monitores convencionales fueron falsas, mientras que menos de un 1 por ciento de las alarmas reportadas por el sistema experto fueron falsas. La sensibilidad de los monitores convencionales fue de 79 por ciento y la del sistema experto de un 92 por ciento. El valor predictivo positivo fue un 31 por ciento con los monitores convencionales y un 97 por ciento con el sistema experto. En conclusion, la confiabilidad de las alarmas mejoró significativamente al integrar información de varias variables, reduciendo notablemente la frecuencia de alarmas falsas. La lógica difusa fue una herramienta poderosa y útil para integrar información fisiológica