Intracranial Hypertension and Intra-abdominal Pressure. Is it Worth Measuring?

Patients with refractory intracranial hypertension who have already undergone all the measures recommended by the current guidelines can benefit from having their intraabdominal pressure monitored since its increase generates hemodynamic repercussions and secondary elevation of intracranial pressure. In this context, a bibliographic research was performed on PubMed with the terms intra-abdominal pressure, abdominal compartment syndrome, intracranial pressure, intracranial hypertension. Altogether, 146 articles were observed, 87 of which were from the year 2000, and only 15 articles were considered relevant to the topic. These studies indicate that patients with refractory intracranial hypertension can benefit fromthe measurement of intraabdominal pressure, since there is evidence that an increase in this pressure leads to organic dysfunctions with an indirect impact on cerebral venous return and, consequently, an increase in intracranial pressure. In thosewho underwent decompression laparotomy, direct effectswere observed in reducing intracranial hypertension and survival.

Suspected abdominal compartment syndrome during endoscopic diskectomy: A case report

Abdominal compartment syndrome can produce a critical situation if not diagnosed early and managed properly. We report a case of abdominal compartment syndrome that was caused by massive irrigation of surgical fluid during endoscopic lumbar diskectomy at the L4–L5 level. There was a sudden increase in peak inspiratory pressure during the operation, and the patient's tidal volume and blood pressure decreased. When the patient's position was changed from prone to supine, abdominal distension and cyanosis of both lower extremities were discovered. Ultrasonic findings showed fluid collection in both the chest and intra-abdominal cavity. Thoracentesis and abdominal decompression surgery were performed, and the patient's overall state improved. We concluded that irrigation fluid used during the endoscopic operation leaked into the retroperitoneal space and caused abdominal compartment syndrome.

The use of negative pressure wave treatment in athlete recovery

Background: Athletes need to recover fully to maximise performance in competitive sport. Athletes who replenish more quickly and more efficiently are able to train harder and more intensely. Elite athletes subjectively report positive results using lower body negative pressure (LBNP) treatment as an alternate method for rapid recovery, restoring and improving their impaired physical state. Objective data on the efficacy are lacking.Objectives: To investigate the effect of intermittent vacuum therapy on accelerating acute recovery following an athlete's normal daily training schedule of strenuous exercise. Objective measurements of biological markers of muscular fatigue were used to assess recovery.Methods: Twenty-two male cricket players in a randomised cross-over study were divided into a treatment and control group respectively. Following a one-hour high-intensity gym session, the treatment group received three 30-minute LBNP exposure sessions over three consecutive days (0, 24 and 48 hours). Blood lactate and creatine kinase biomarkers were collected to measure the recovery process. After 14 days groups were crossed over and the trial repeated.Results: Heart rate and blood pressure decreased noticeably during treatment, reverting to baseline levels after treatment. Lactate concentrations decreased in both groups after exercise termination; significantly more in the treatment (0.57±0.23 mmol/l) than control group (0.78±0.22 mmol/l), p<0.001). Creatine kinase (CK) was similar in both groups. Athletes' subjective assessments of recovery rated moderately high.Conclusion: LBNP therapy applied as treatment during routine schedule may have a systemic effect in lowering serum lactate levels, but not CK levels. Enhanced recovery of athletes is still unconfirmed

Abdominal Compartment Syndrome in Severe Acute Pancreatitis Treated with Percutaneous Catheter Drainage

Acute pancreatitis is one of the main causes of intra-abdominal hypertension (IAH). IAH contributes to multiple physiologic alterations and leads to the development of abdominal compartment syndrome (ACS) that induces multiorgan failure. We report a case of ACS in a patient with severe acute pancreatitis. A 44-year-old man who was admitted in a drunk state was found to have severe acute pancreatitis. During management with fluid resuscitation in an intensive care unit, drowsy mentality, respiratory acidosis, shock requiring inotropes, and oliguria developed in the patient, with his abdomen tensely distended. With a presumptive diagnosis of ACS, abdominal decompression through percutaneous catheter drainage was performed immediately. The intraperitoneal pressure measured with a drainage catheter was 31 mm Hg. After abdominal decompression, the multiorgan failure was reversed. We present a case of ACS managed with percutaneous catheter decompression.

Gastrostomia e jejunostomia: aspectos da evolução técnica e da ampliação das indicações / Gastrostomy and jejunostomy: aspects of the technical evolution and widening of indications

O acesso à luz do estômago e do jejuno proximal por meio de gastrostomia e jejunostomia, respectivamente, de forma temporária ou definitiva, está indicado diante da necessidade prolongada de descompressão digestiva ou de suporte alimentar. O emprego desses procedimentos expandiu-se nos últimos 25 anos com a introdução da gastrostomia endoscópica, especialmente em pacientes com afecções neurológicas de evolução progressiva e neoplasias avançadas. Este artigo aborda aspectos conceituais da gastrostomia e jejunostomia, as principais indicações, as vias de acesso preferenciais em diferentes cenários clínicos e as modalidades técnicas frequentemente empregadas. O manejo dessas estomias, os resultados e as potenciais complicações também são enfatizados. Finalmente, os fundamentos éticos e legais da ampliação da indicação da gastrostomia e da jejunostomia como procedimentos paliativos são discutidos.

A temporary or permanent access to the stomach or jejunum, through a gastrostomy or jejunostomy, is indicated whenever nutritional support or prolonged decompression of the upper alimentary tract is needed. With the introduction of endoscopic gastrostomy, the utilization of these procedures has increased in the last 25 years, specially in patients with progressive neurologic diseases and in those with advanced cancer. This article deals with the conceptual aspects of gastrostomies and jejunostomies, its primary indications, the preferential means of access in different clinical scenarios as well as the technical modalities most frequently used. The management of the stomas, the results and potential complications are also highlighted. Finally, the ethical and legal implications of greater utilization of these procedures in a palliative setting are also discussed.

Case of Abdominal Compartment Syndrome Treated by using a Bedside Open Linea Alba Fasciotomy

Abdominal compartment syndrome (ACS) is a life-threatening disorder caused by rapidly increasing intraabdominal pressure. ACS can result in multiorgan failure and carries a mortality of 60~70%. The treatment of choice in ACS is surgical decompression. There are very few reports of ACS and experience in Korea. We report 12-year-old male patient who developed an abdominal compartment syndrome due to traffic-accident-induced retroperitoneal hematomas, Which was successfully treated by performing a bedside emergency surgical decompression with open linea alba fasciotomy with intact peritoneum. When patients do not respond to medical therapy, a decompressive laparotomy is the last surgical resort. In patients with severe abdominal compartment syndrome, the use of a linea alba fasciotomy is an effective intervention to lower intra-abdominal hypertension (IAH) without the morbidity of a laparotomy. Use of a linea alba fasciotomy as a first-line intervention before committing to full abdominal decompression in patients with abdominal compartment syndrome improves physiological variables without mortality. Consideration for a linea alba fasciotomy as a bridge before full abdominal decompression needs further evaluation in patients with polytrauma abdominal compartment syndrome.

Úlceras por pressão / Pressure sores

Dentre o amplo espectro das chamadas feridas complexas a úlcera por pressãopode ser definida como uma lesão localizada, acometendo pele e/ou tecidos subjacentes, usualmente sobre uma proeminência óssea, resultante de pressão, ou pressão associada a cisalhamento e/ou fricção. Os fatores de risco para úlceras por pressão são todos aqueles que predispõem o indivíduo a períodos prolongados de isquemia induzida por pressão, e que reduzem a capacidade de recuperação tecidual da lesão isquêmica, podendo ter fatoresassociados intrínsecos ou extrínsecos. A classificação de ulceras por pressão e as medidas de prevenção são inúmeras. Contudo, para ulceras por pressão com complicações ou profundidades avançadas o tratamento determinante na sua resolução é o cirúrgico. Nos últimos anos, a introdução da pressão negativa para o tratamento de feridas complexas, como são para muitas úlceras por pressão, foi muito importante como adjuvante no tratamento cirúrgico...

Among the broad spectrum of complex wounds the pressure ulcer can be defined as a localized lesion, affecting the skin and/or underlying tissue usually over a bony prominence,resulting from pressure or pressure combined with shear and/or friction. Risk factors for pressure ulcers are those that predispose an individual to prolonged periods of ischemia induced by pressure, and reduce the ability of the tissue recovery of a ischemic injury, which can have associated factors, intrinsic or extrinsic. The classification of pressure ulcers and prevention scales are numerous. However, for pressure ulcers with complications or advanced depths the determinant treatment is surgery. In recent years, the introduction of negative pressuredressing for treatment of complex wounds, as are many pressure ulcers, was very important as an adjuvant therapy surgery...

Spectral analysis of respiratory-related hemodynamic variables in simulated hypovolemia: a study in healthy volunteers with spontaneous breathing using a paced breathing activity / 대한마취과학회지

BACKGROUND: A dynamic preload index such as stroke volume variation (SVV) is not as reliable in spontaneous breathing (SB) patients as in mechanically ventilated patients. This study examined the hypothesis that spectral analysis of hemodynamic variables during paced breathing (PB) activity may be a feasible index of volume changes and fluid responsiveness, despite insufficient respiratory changes in the preload index during SB activity. METHODS: Blood pressure and stroke volume (SV) were measured in 16 subjects undergoing PB (15 breaths/min), using a Finometer device and the Modelflow method. Respiratory systolic pressure variation (SPV) and SVV were measured and respiratory frequency (RF, 0.2-0.3 Hz) of power spectra of SPV (SPV(RF)) and SVV (SVV(RF)) were computed using fast Fourier transformation. Progressive hypovolemia was simulated with lower body negative pressure (LBNP). Volume challenges were produced by infusion of normal saline and subsequent release of LBNP to baseline. Fluid responsiveness, defined as a >20% increase in SV, was assessed by the area under the curve (AUC) of receiver operating characteristic curves. RESULTS: Graded hypovolemia caused a significant increase in SPV(RF) and a decrease in SVV(RF). During volume expansion, SPV(RF) decreased and SVV(RF) rose significantly. Fluid responsiveness was better predicted with SVV(RF) (AUC 0.75) than with SPV(RF), SPV, or SVV. SVV(RF) before volume challenge was significantly correlated with volume expansion-induced changes in SV (r = -0.64). CONCLUSIONS: These results suggest that RF spectral analysis of dynamic preload variables may enable the detection of volume change and fluid responsiveness in SB hypovolemic patients performing PB activity.

Measurement of respiratory pulse transit time variation as an intravascular volume index in simulated hemorrhage / 대한마취과학회지

BACKGROUND: We examined the usefulness of respiratory pulse transit time (PTT) variation as an intravascular volume index in young, healthy, spontaneous, paced breathing volunteers exposed to simulated central hypovolemia by lower body negative pressure (LBNP). METHODS: With paced breathing at 0.25 Hz, beat-to-beat finger blood pressure (BP), heart rate (HR), cardiac output (CO), stroke volume (SV), total peripheral resistance (TPR), and PTT were measured non-invasively in 18 healthy volunteers. Graded central hypovolemia was generated using LBNP from 0 to -20, -30, -40, and -50 mmHg. Respiratory PTT variation (PTTV) was calculated as the difference of maximal and minimal values divided by their respective means. Respiratory-frequency PTT variability (PTTRF) using power spectral analysis was also estimated. RESULTS: During LBNP, SV, CO and PTTRF decreased, but PTT, PTTV and TPR increased significantly. PTTV did not correlate with SV changes (r = -0.08, P = 0.52), but PTTRF (r = 0.58, P < 0.01) and PTT (r = 0.43, P < 0.01) did during progressive hypovolemia. CONCLUSIONS: PTTRF is more applicable to the changes in intravascular volume than PTT and PTTV, suggesting spectral analysis of PTT might be used as a dynamic preload index in patients with spontaneous and paced breathing condition, which needs further studies.

Anesthetic Management of a Patient with Abdominal Compartment Syndrome : A case report / 대한마취과학회지

Abdominal compartment syndrome (ACS) is a life-threatening emergency requiring prompt treatment. In these cases, a patient cannot ventilate effectively and oliguria can occur because of the high intra-abdominal pressure (IAP). The mortality rate is very high. Treatment is abdominal decompression and secondary closure. There are very few reports of the anesthetic management of a patient with ACS. We report a 38-year-old male patient who was diagnosed with ACS at the operating room. The IAP was measured and emergency abdominal decompression and "Bogota bag" apply were performed. The respiratory and hemodynamic parameters improved after this treatment.

Abdominal compartment syndrome an under-recognized salient killer

Abdominal compartment syndrome is an underdiagnosed surgical entity that carries serious consequences. High index of suspicion and identifying patients at risk cannot be overemphasized. to raise awareness of this syndrome with reference to diagnosis and management. Patients and 12 patients with clinical diagnosis of abdominal compartment syndrome, confirmed by measurement of intracystic pressure in 8 patients. Abdominal decompression was performed in 9 patients. Clinical parameters were recorded before and after decompression. 48.4% reduction in peak inspiratory pressure, 19.3% increase in arterial oxygen tension, 81.4% increase in urine output, 8.3% increase in Glasgow coma score of head injury, 12.7% increase in systolic blood pressure and 66.1% drop in central venous pressure. There was a 43.8% drop in the intraabdominal pressure. Abdominal compartment syndrome is potentially fatal, if diagnosis and intervention are not timely performed. Measurement of the intra-vesical pressure provides an objective clue to monitor this condition, but should not rule out the clinical diagnosis. Abdominal decompression is a proven lifesaving intervention. Closing the abdomen under severe tension in high risk patients should be abandoned. Sudden release of high intra-abdominal pressure can lead to sudden death and should be watched for. Wound complications after decompression procedure are not uncommon but saving patient's life is the priority

Pressure and time dependence of the cardiopulmonary reflex response in patients with hypertensive cardiomyopathy

The first minutes of the time course of cardiopulmonary reflex control evoked by lower body negative pressure (LBNP) in patients with hypertensive cardiomyopathy have not been investigated in detail. We studied 15 hypertensive patients with left ventricular dysfunction (LVD) and 15 matched normal controls to observe the time course response of the forearm vascular resistance (FVR) during 3 min of LBNP at -10, -15, and -40 mmHg in unloading the cardiopulmonary receptors. Analysis of the average of 3-min intervals of FVR showed a blunted response of the LVD patients at -10 mmHg (P = 0.03), but a similar response in both groups at -15 and -40 mmHg. However, using a minute-to-minute analysis of the FVR at -15 and -40 mmHg, we observed a similar response in both groups at the 1st min, but a marked decrease of FVR in the LVD group at the 3rd min of LBNP at -15 mmHg (P = 0.017), and -40 mmHg (P = 0.004). Plasma norepinephrine levels were analyzed as another neurohumoral measurement of cardiopulmonary receptor response to LBNP, and showed a blunted response in the LVD group at -10 (P = 0.013), -15 (P = 0.032) and -40 mmHg (P = 0.004). We concluded that the cardiopulmonary reflex response in patients with hypertensive cardiomyopathy is blunted at lower levels of LBNP. However, at higher levels, the cardiopulmonary reflex has a normal initial response that decreases progressively with time. As a consequence of the time-dependent response, the cardiopulmonary reflex response should be measured over small intervals of time in clinical studies.

Recent advances in the management of abdominal compartment syndrome

Abdominal compartment syndrome is a systemic syndrome involving derangement in cardiovascular hemodynamics, respiratory and renal function as a result of sustained increase in intra-abdominal pressure. This results in multi-organ failure requiring prompt action and treatment. Presentation can be acute, chronic and acute on chronic. Initial diagnosis is clinical, confirmed by measurement of urinary bladder pressure. Treatment is abdominal decompression by laparostomy and delayed abdominal closure. Awareness among the surgeons has increased because laparoscopy has resulted in determination of intra-abdominal pressure as a readily measurable quantity. They have been able to appreciate the benefit of abdominal decompression by performing repeated planned laparotomies for trauma

The changes of cardiovascular response to orthostatic stress caused by hypovolemia induced by weightlessness: a simulation study / 生物医学工程学杂志

We introduced the method of computer simulation in the studies of gravitational physiology. Based on work of Melchior (1994), we developed a mathematical model that can be used to stimulate cardiovascular responses to orthostatic stress (lower body negative pressure, LBNP). The model includes 7 sub-models: the redistribution of blood, the filling of left ventricle, left ventricle working, peripheral circulation, control of heart rate (HR), control of peripheral resistance and control of venous tone. Then we simulated the changes of blood pressure (BP) and heart rate during lower body negative pressure, and the results agreed well with the results of our human experiment. By using the developed model, we also simulated the effects of hypovolemia on the BP, HR and shock index during orthostatic stress. The simulation results indicate that the cardiovascular responses to orthostatic stress change significantly when the decrease of blood volume is more than 15% of the total blood volume. However, if the amount of the decrease of blood volume is less than 5% of the total blood volume, HR and BP could be maintained in normal range by the regulation of baroreflex during LBNP. Our simulation results suggest that hypovolemia may be the main cause of orthostatic intolerance induced by weightlessness.

The Treatment of Adhesive Small Bowel Obstruction in Children

BACKGROUND: Immediate operative management has been applied to infants and children with an attacks of adhesive small-bowel obstruction (ASBO), but this treatment has been controversial. We retrospectively reviewed 30 patients who were admitted from 1992 to 1996 because of adhesive small-bowel obstructions. METHODS: Immediate operation was reserved for the 7 patients that presented with fever and leukocytosis and /or localized abdominal tenderness or complete obstruction. The remaining 23 patients initially underwent conservative treatment. RESULTS: Although 20 episodes were cured with conservative treatment, 3 cases subsequently required surgical intervention. No adverse occurrences were observed during or after the delayed operations. Recurrence occurred in 3 cases after surgery and in 2 cases after conservative treatment. In the study, we found that the age at the recent laparotomy, the time elapsed between the recent laparotomy and the obstructive episode, and the primary condition necessitating the laparotomy correlated significantly with the success of conservative treatment. CONCLUSIONS: We conclude that in the treatment of ASBO in children, conservative treatment through the use of abdominal decompression, antibiotics, fluid-electrolytes, physical therapy, etc. has to be applied first for patients without significant evidence of strangulation and complete obstruction.

Effectiveness of a Rectal Tube for Relief of Pain after Colonoscopy / 대한소화기내시경학회지

BACKGROUND AND AIMS: Abdominal distension from the insufflation of air can create more troublesome discomfort after colonoscopy (CFS) than after upper endoscopy. Many patients report difficulty in expelling insufflated air after CFS. One previous study demonstrated that insertion of rectal tube at the conclusion of CFS significantly improves patient satisfaction with the procedure. The aim of this study was to compare the effectiveness of rectal tube placement for abdominal decompression after CFS in an effort to limit patient discomfort by carefully applying air suction during CFS. METHODS: We conducted a prospective trial in 103 consecutive patients undergoing elective CFS. Patients were randomized to receive rectal tube placement at the end of the procedure or simple air suction during the procedure. Patients were evaluated by clinical symptoms and signs 10 minutes after completion of CFS. RESULTS: All 103 patients had a complete examination of the colon to the cecum. No specific complications occurred during and a day after examination. The two groups were well matched with respect to age, sex, height, weight, chief complaints. There were no significant differences between the two groups for bowel preparation, duration of examination, abdominal pain during procedure, abdominal disten-sion 10 minutes after CFS, and abdominal pain 10 minutes after CFS (p >0.05). CONCLUSIONS: Meticulous air suction during CFS reduces abdominal discomfort and distension after CFS and is as effectively as the placement of a rectal tube at the con-clusion of CFS.

Cardiovascular responses to application of lower body negative pressure of male volunteers in seated position.

Lower body negative pressure (LBNP) has been used to evaluate orthostatic tolerance and for studying the effects of +Gz induced physiological strain and hence has great practical significance in aerospace medicine. Cardiovascular responses in man on application to LBNP (-40 mmHg) in seated (upright) position in a specially designed LBNP chamber have been studied in eight normal healthy male volunteers between the age group of 25-36 yrs. They were subjected to -40 mmHg negative pressure in steps of -10 mmHg for a duration of 5 min each. The total duration of the experiment was 20 min. Heart rate (HR), blood pressure (BP) Cardiac output (CO) were measured and mean blood pressure (MBP) and total peripheral resistance (TPR) were computed. The results indicate a significant increase in HR (P < 0.01), SV (P < 0.01). Studies on limited number of subjects on application to LBNP (40 mmHg) in supine position have also been carried out and compared with the physiological strain induced in subjects in seated position. Study of HR, SV, CO, responses of the subjects on exposure to LBNP in seated position elicit similar response in subjects exposed to +Gz stress as reported by other workers. It is concluded that LBNP technique can be used to study the effects of +Gz induced physiological strain in man.

Mejoría de las pruebas de función respiratoria por paracentesis en pacientes con ascitis a tensión / Improvement in functional respiratory tests in patients with tense ascites

La ascitis a tensión ocasiona insuficiencia respiratoria mecánica al dificultar el descenso del diafragma; la paracentesis evacuadora debe mejorar este cuadro. El objetivo del trabajo fue determinar el efecto de la paracentesis evacuadora sobre las pruebas de función respiratoria en el enfermo con ascitis a tensión. En un grupo de 15 sujetos con ascitis a tensión (secundaria a cirrosis hepática) que provocó dificultad respiratoria se realizaron gasometría arterial, medición del perímetro abdominal y pruebas de función respiratoria previa y posteriormente (dos y 24 h) a la realización de paracentesis evacuadora de tres litros de líquido de ascitis. En ninguno de los casos el paciente se encontraban en encefalopatía hepática o sangrado de tubo digestivo alto. El método estadístico empleado fue t de Student. En los 15 sujetos hubo disminución del perímetro abdominal de 3 cm en promedio, así como resolución de los síntomas respiratorios. En la gasometría arterial hubo elevación de paO2, en promedio 5 mmHg (p< 0.005), la saturación de O2 mejoró 2.61 por ciento (p< 0.05). En las pruebas de función respiratoria todos los sujetos mostraron un patrón obstuctivo. La velocidad máxima de flujo a la exhalación (VMFE) mejoró en promedio 0.2 y 0.4 l/seg a las dos y 24 h (p < 0.001), la capacidad vital forzada (CVF) disminuyó 0.36 y 0.25 l respectivamente (p < 0.5 en ambos valores), el volumen espiratorio forzado del primer segundo (VEF1) subió 0.01 y 0.4 l (p< 0.05 y < 0.005), y la relación CVE/VEF1 se elevó 8.7 y 13 por ciento (p< 0.05 y < 0.005). Característicamente los pacientes que obtuvieron un menor beneficio de la paracentesis eran fumadores. La paracentesis es un método eficaz para mejorar la función respiratoria del sujeto con ascitis a tensión

Calcium channel blockers and the CVS reflex responses during lower body suction.

Nine normal men (mean age 27.6 yr) were exposed to continuous lower-body suction pressure (LBSP) of -20 to -50 mmHg (for 5 min at each level) on four different occasions after having consumed a single oral therapeutic dose of either diltiazem, nifedipine, verapamil, or a placebo, randomly, in a single blind manner. The suction was applied at 12.30 pm in all experiments, while the medications were administered in such a manner so that their expected peak plasma levels would have been achieved at the time of suction application. The cardiovascular reflex effects commenced at a pressure of -30 mmHg, and peaked at -50 mmHg. The increases in the heart rate for all treatments at -50 mmHg was statistically similar (about 16-20 beats/min). The systolic BP fell by about 9 mmHg for the placebo experiments, and this change was not different from the changes produced by the 3 Calcium channel blocker treatments. The diastolic BP increase was about 3 mmHg. The Cardiac index did not vary significantly. Our results suggest that the commonly used Ca++ channel blockers do not adversely affect orthostatic tolerance.

Lower-body suction and cardiovascular reflexes: physiological and applied considerations.

Lower body subatmospheric pressure (LBSP) can be applied in a graded manner to a supine subject enclosed in a box upto the level of the iliac crest in order to elicit cardiovascular reflexes without a change of posture, and without a gravity induced shift of the central blood volume into the periphery. The procedure effectively produces a controlled, non-haemorrhagic hypovolaemia. The method may be used to differentiate the reflex cardiovascular effects induced by the deactivation of the low-pressure cardiovascular receptors (LBSP less than 30mmHg), and those produced by the deactivation of the arterial baroreceptors (LBSP greater than 30 mmHg). The former results in an increase in the limb vascular resistance without a change in heart rate and blood pressure, while the latter produces a tachycardia, an increase in the diastolic BP with a fall in the sytolic BP. The CVP and the cardiac output reduce with increasing suction. Cardiovascular reflex effects of -40 mmHg are similar to those produced by a change of posture from supine to standing. Vaso-vagal syncope appears with increasing frequency when LBSP exceeds -60 mmHg even in the normal subjects. The test is useful in the aeromedical assessment of apparently normal individuals with low orthostatic tolerance, in the evaluation of the effects of physiological and pharmacological interventions on cardiovascular reflexes, and in the evaluation of patients of autonomic neuropathies. LBSP is also a means of inducing safe, well controlled syncope in order to study the genesis of this phenonmenon.