Increased plasma endothelin-1 levels in patients with progressive open angle glaucoma

AIM: To compare the plasma levels of endothelin-1 (ET-1) between patients with primary open angle glaucoma with visual field progression despite normal or normalised intraocular pressure and patients with stabile visual fields in a retrospective study. METHODS: The progressive group consisted of 16 primary open angle glaucoma patients and the group with stable visual field consisted of 15 patients. After a 30 minute rest in a supine position, venous blood was obtained for ET-1 dosing. Difference in the plasma level of ET-1 between two groups was compared by means of analysis of covariance (ANCOVA), including age, sex, and mean arterial blood pressure as covariates. RESULTS: ET-1 plasma levels were found to be significantly increased in patients with deteriorating (3.47 (SD 0.75) pg/ml) glaucoma when compared to those with stable (2.59 (SD 0.54) pg/ml) visual fields (p = 0.0007). CONCLUSIONS: Glaucoma patients with visual field progression in spite of normal or normalised intraocular pressure have been found to have increased plasma endothelin-1 levels. It remains to be determined if this is a secondary phenomenon or whether it may have a role in the progression of glaucomatous damage.

Influence of inspired oxygen on glucose-lactate dynamics after subdural hematoma in the rat

The mechanisms causing brain damage after acute subdural hematoma (SDH) are poorly understood. A decrease in cerebral blood flow develops immediately after the hematoma forms, thus reducing cerebral oxygenation. This in turn may activate mitochondrial failure and tissue damage leading to ionic imbalance and possibly to cellular breakdown. The purpose of this study was to test whether a simple therapeutic measure, namely increased fraction of inspired oxygen (FiO2 100), and hence increased arterial and brain tissue oxygen tension, can influence brain glucose and lactate dynamics acutely after subdural hematoma in the rat. Twenty-five male Sprague-Dawley anesthetized rats were studied before, during and after induction of the SDH in two separate groups. The Oxygen group (n = 10) was ventilated with 100% oxygen immediately after induction of the SDH. The Air group (n = 10) was ventilated during the entire study with 21% oxygen. Brain microdialysate samples were analyzed for glucose and lactate. All rats were monitored with femoral arterial blood pressure catheters, arterial blood gas analysis, arterial glucose, lactate and end tidal CO2 (EtCO2). Five male Sprague-Dawley rats were sham operated to measure the effect of oxygen challenge on glucose-lactate dynamics without injury. Arterial oxygen tension in the Oxygen group was 371 +/- 30 mmHg and was associated with significantly greater increase in dialysate lactate in the first 30 min after induction of SDH. Dialysate glucose initially dropped in both groups, after SDH, but then reverted significantly faster to values above baseline in the Oxygen group. Changes in ventilatory parameters had no significant effect on dialysate glucose and lactate parameters in the sham group. Extracellular dialysate lactate and glucose are influenced by administration of 100% O2 after SDH. Dialysate glucose normalizes significantly quicker upon 100% oxygen ventilation. We hypothesize that increased neural tissue oxygen tension, in presence of reduced regional CBF, and possibly compromised mitochondrial function, after acute SDH results in upregulation of rate-limiting enzyme systems responsible for both glycolytic and aerobic metabolism. Similar changes have been seen in severe human head injury, and suggest that a simple therapeutic measure, such as early ventilation with 100% O2, may improve cerebral energy metabolism, early after SDH. Further studies to measure the generation of adenosine triphosphate (ATP) are needed to validate the hypothesis.

Crystalloids versus colloids for goal-directed fluid therapy in major surgery

INTRODUCTION: Perioperative hypovolemia arises frequently and contributes to intestinal hypoperfusion and subsequent postoperative complications. Goal-directed fluid therapy might reduce these complications. The aim of this study was to compare the effects of goal-directed administration of crystalloids and colloids on the distribution of systemic, hepatosplanchnic, and microcirculatory (small intestine) blood flow after major abdominal surgery in a clinically relevant pig model. METHODS: Twenty-seven pigs were anesthetized and mechanically ventilated and underwent open laparotomy. They were randomly assigned to one of three treatment groups: the restricted Ringer lactate (R-RL) group (n = 9) received 3 mL/kg per hour of RL, the goal-directed RL (GD-RL) group (n = 9) received 3 mL/kg per hour of RL and intermittent boluses of 250 mL of RL, and the goal-directed colloid (GD-C) group (n = 9) received 3 mL/kg per hour of RL and boluses of 250 mL of 6% hydroxyethyl starch (130/0.4). The latter two groups received a bolus infusion when mixed venous oxygen saturation was below 60% ('lockout' time of 30 minutes). Regional blood flow was measured in the superior mesenteric artery and the celiac trunk. In the small bowel, microcirculatory blood flow was measured using laser Doppler flowmetry. Intestinal tissue oxygen tension was measured with intramural Clark-type electrodes. RESULTS: After 4 hours of treatment, arterial blood pressure, cardiac output, mesenteric artery flow, and mixed oxygen saturation were significantly higher in the GD-C and GD-RL groups than in the R-RL group. Microcirculatory flow in the intestinal mucosa increased by 50% in the GD-C group but remained unchanged in the other two groups. Likewise, tissue oxygen tension in the intestine increased by 30% in the GD-C group but remained unchanged in the GD-RL group and decreased by 18% in the R-RL group. Mesenteric venous glucose concentrations were higher and lactate levels were lower in the GD-C group compared with the two crystalloid groups. CONCLUSIONS: Goal-directed colloid administration markedly increased microcirculatory blood flow in the small intestine and intestinal tissue oxygen tension after abdominal surgery. In contrast, goal-directed crystalloid and restricted crystalloid administrations had no such effects. Additionally, mesenteric venous glucose and lactate concentrations suggest that intestinal cellular substrate levels were higher in the colloid-treated than in the crystalloid-treated animals. These results support the notion that perioperative goal-directed therapy with colloids might be beneficial during major abdominal surgery.

Temporary hypoxic stress protects the liver from Fas-mediated apoptosis and ischemia reperfusion injury

Molecular responses to hypoxia restore oxygen homeostasis and promote cell survival, and are mainly regulated through the activation of the hypoxia-inducible transcription factor (HIF)-1 and its target genes. In this study we questioned whether surgically depleting the liver s arterial blood supply, by clamping the hepatic artery (HA), would be sufficient to mount a hypoxia-driven molecular response, the up-regulation of hepatoprotective genes and thereby protect the liver from subsequent damaging insults.;;The HA of normal male Balb/c mice was clamped with a micro vascular clip for 2 hours. The liver s saturated oxygen concentration (SO2) was measured using an O2C surface probe (LEA-Medizintechnik) and interstitial fluid was collected with microdialysis membranes to monitor tissue damage. Mice without clamping served as sham operated controls. Interstitial fluid was assessed for lactate pyruvate (L/P) and glycerol content and the mRNA of hepatoprotective genes was analyzed by real time PCR. Subsequently, mice received either a tail vein injection of anti-Fas antibody (Jo2, 0.2 mg/kg) or the liver was made ischemic (60min) followed by 6 hours reperfusion. Caspase 3-activity and cleaved lamin A were used to assess apoptosis. In separate groups, animal were monitored for survival.;;After 30min of clamping the HA the SO2 of the liver decreased and remained at a reduced level for up to 2 hours, without an increase in L/P ratio or glycerol release. We demonstrate the activation of a hypoxia-inducible signaling pathway by the stabilization of HIF-1 protein (Western blot) and by an increase of its target gene, Epo, mRNA. There was an up-regulation of the hepatoprotective genes IL-6, IGFBP-1, HO-1 and A20 mRNA. When subsequently injected with Jo2, animals preconditioned with HA clamping, had a significantly decreased caspase-3 activity (avg21044 vs. avg3637; p=0.001, T-test) and there were fewer positive cells for cleaved Lamin A. The survival probability (10.5 hours, n=12) of mice with HA clamping was significantly higher (3.2 hours, n=13; p=0.014, Logrank test). Likewise, survival after 60 minutes of partial hepatic ischemia and 6 hours of reperfusion was reduced from 86% in mice with pretreatment by HA clamping to 56% in sham treated controls.;;This study demonstrates that a localized hypoxic stress can be achieved by surgically removing the livers arterial blood supply. Furthermore it can stimulate a hepatoprotective response that protects the liver against Fas-mediated apoptosis and ischemia-reperfusion injury. Our findings offer an innovative approach to induce hepatoprotective genes to defend the liver against subsequent insults.

Effects of a low dose infusion of racemic and S-ketamine on the nociceptive withdrawal reflex in standing ponies

OBJECTIVE: To investigate the effect of plasma concentrations obtained by a low dose constant rate infusion (CRI) of racemic ketamine or S-ketamine on the nociceptive withdrawal reflex (NWR) in standing ponies. STUDY DESIGN: Prospective, blinded, cross-over study. ANIMALS: Six healthy 5-year-old Shetland ponies. METHODS: Ponies received either 0.6 mg kg(-1) racemic ketamine (group RS) or 0.3 mg kg(-1) S-ketamine (group S) intravenously (IV), followed by a CRI of 20 microg kg(-1)minute(-1) racemic ketamine (group RS) or 10 microg kg(-1)minute(-1) S-ketamine (group S) for 59 minutes. The NWR was evoked by transcutaneous electrical stimulation of a peripheral nerve before drug administration, 15 and 45 minutes after the start of the bolus injection and 15 minutes after the end of the CRI. Electromyographic responses were recorded and analysed. Arterial blood was collected before stimulation and plasma concentrations of ketamine and norketamine were measured enantioselectively using capillary electrophoresis. Ponies were video recorded and monitored to assess drug effects on behaviour, heart rate (HR), mean arterial blood pressure (MAP) and respiratory rate. RESULTS: The NWR was significantly depressed in group RS at plasma concentrations between 20 and 25 ng mL(-1) of each enantiomer. In group S, no significant NWR depression could be observed; plasma concentrations of S-ketamine (9-15 ng mL(-1)) were lower, compared to S-ketamine concentrations in group RS, although this difference was not statistically significant. Minor changes in behaviour, HR and MAP only occurred within the first 5-10 minutes after bolus drug administration in both groups. CONCLUSION: Antinociceptive activity in standing ponies, demonstrated as a depression of the NWR, could only be detected after treatment with racemic ketamine. S-ketamine may have lacked this effect as a result of lower plasma concentrations, a more rapid metabolism or a lower potency of S-ketamine in Equidae so further investigation is necessary.

The effects of aspirin and nonselective beta blockade on the acute prothrombotic response to psychosocial stress in apparently healthy subjects

We hypothesized that the 2 cardiovascular drugs aspirin and propranolol attenuate the prothrombotic response to acute psychosocial stress relative to placebo medication. We randomized 56 healthy subjects, double-blind, to 5-day treatment with an oral dose of either 100 mg of aspirin plus 80 mg of propranolol combined, single aspirin, single propranolol, or placebo medication. Thereafter, subjects underwent a 13-minute psychosocial stressor. Plasma levels of von Willebrand factor antigen (VWF:Ag), fibrinogen, coagulation factor VII (FVII:C) and XII (FXII:C) activity, and D-dimer were determined in blood samples collected immediately pre- and post-stress and 45 minutes post-stress. The stress-induced changes in prothrombotic measures were adjusted for gender, age, body mass index, mean arterial blood pressure, smoking status, and sleep quality. There was an increase in VWF:Ag levels from immediately pre-stress to 45 minutes post-stress in the placebo group relative to the 3 subject groups with verum medication (P's

Coagulation activity before and after acute psychosocial stress increases with age

OBJECTIVE: To assess whether stress further increases hypercoagulation in older individuals. We investigated whether acute stress-induced changes in coagulation parameters differ with age. It is known that hypercoagulation occurs in response to acute stress and that a shift in hemostasis toward a hypercoagulability state occurs with age. However, it is not yet known whether acute stress further increases hypercoagulation in older individuals, and thus may increase their risk for cardiovascular disease (CVD). METHODS: A total of 63 medication-free nonsmoking men, aged between 20 and 65 years (mean +/- standard error of the mean = 36.7 +/- 1.7 years), underwent an acute standardized psychosocial stress task combining public speaking and mental arithmetic in front of an audience. We measured plasma clotting factor VII activity (FVII:C), fibrinogen, and D-dimer at rest, immediately, and 20 minutes after stress. RESULTS: Increased age predicted greater increases in fibrinogen (beta = 0.26, p = 0.041; DeltaR(2) = 0.05), FVII:C (beta = 0.40, p = .006; DeltaR(2) = 0.11), and D-dimer (beta = 0.51, p < .001; DeltaR(2) = 0.18) from rest to 20 minutes after stress independent of body mass index and mean arterial blood pressure. General linear models revealed significant effects of age and stress on fibrinogen, FVII:C, and D-dimer (main effects: p < .04), and greater D-dimer stress reactivity with older age (interaction age-by-stress: F(1.5/90.4) = 4.36, p = .024; f = 0.33). CONCLUSIONS: Our results suggest that acute stress might increase vulnerability in the elderly for hypercoagulability and subsequent hemostasis-associated diseases like CVD.

Aspirin, but not propranolol, attenuates the acute stress-induced increase in circulating levels of interleukin-6: a randomized, double-blind, placebo-controlled study

Psychosocial stress might increase the risk of atherothrombotic events by setting off an elevation in circulating levels of the proinflammatory cytokine interleukin (IL)-6. We investigated the effect of aspirin and propranolol on the responsiveness of plasma IL-6 levels to acute psychosocial stress. For 5 days, 64 healthy subjects were randomized, double-blind, to daily oral aspirin 100mg plus long-acting propranolol 80 mg, aspirin 100mg plus placebo, long-acting propranolol 80 mg plus placebo, or placebo plus placebo. Thereafter, all subjects underwent the 13-min Trier Social Stress Test, which combines a preparation phase, a job interview, and a mental arithmetic task. Plasma IL-6 levels were measured in blood samples collected immediately pre- and post-stress, and 45 min and 105 min thereafter. The change in IL-6 from pre-stress to 105 min post-stress differed between subjects with aspirin medication and those without (p =0.033; eta p2=0.059). IL-6 levels increased less from pre-stress to 105 min post-stress (p <0.027) and were lower (p =0.010) at 105 min post-stress in subjects with aspirin than in subjects without aspirin. The significance of these results was maintained when controlling for gender, age, waist-to-hip ratio, mean arterial blood pressure, and smoking status. Medication with propranolol was not significantly associated with the stress-induced change in IL-6 levels. Also, aspirin and propranolol did not significantly interact in determining the IL-6 stress response. Aspirin but not propranolol attenuated the stress-induced increase in plasma IL-6 levels. This suggests one mechanism by which aspirin treatment might reduce the risk of atherothrombotic events triggered by acute mental stress.

Stereoselective pharmacokinetics of ketamine and norketamine after constant rate infusion of a subanesthetic dose of racemic ketamine or S-ketamine in Shetland ponies

OBJECTIVE: To evaluate pharmacokinetics of ketamine and norketamine enantiomers after constant rate infusion (CRI) of a subanesthetic dose of racemic ketamine or S-ketamine in ponies. ANIMALS: Five 6-year-old Shetland pony geldings that weighed between 101 and 152 kg. PROCEDURES: In a crossover study, each pony received a CRI of racemic ketamine (loading dose, 0.6 mg/kg; CRI, 0.02 mg/kg/min) and S-ketamine (loading dose, 0.3 mg/kg; CRI, 0.01 mg/kg/min), with a 1-month interval between treatments. Arterial blood samples were collected before and at 5, 15, 30, 45, and 60 minutes during drug administration and at 5, 10, 30, and 60 minutes after discontinuing the CRI. Plasma ketamine and norketamine enantiomers were quantified by use of capillary electrophoresis. Individual R-ketamine and S-ketamine concentration-versus-time curves were analyzed by use of a monocompartmental model. Plasma disposition curves for R-norketamine and S-norketamine were described by estimating the area under the concentration-versus-time curve (AUC), maximum concentration (Cmax), and time until Cmax. RESULTS: Plasma concentrations of S-ketamine decreased and biodegradation products increased more rapidly after S-ketamine CRI, compared with results after racemic ketamine CRI. The R-norketamine was eliminated faster than was the S-norketamine. Significant differences between treatments were found for the AUC of S-ketamine and within the racemic ketamine CRI for the AUC and Cmax of norketamine isomers. CONCLUSIONS AND CLINICAL RELEVANCE: CRI of S-ketamine may be preferable over CRI of racemic ketamine in standing equids because the S-enantiomer was eliminated faster when infused alone instead of as part of a racemic mixture.

Evaluation of anesthesia recovery quality after low-dose racemic or S-ketamine infusions during anesthesia with isoflurane in horses

OBJECTIVE: To compare anesthesia recovery quality after racemic (R-/S-) or S-ketamine infusions during isoflurane anesthesia in horses. ANIMALS: 10 horses undergoing arthroscopy. PROCEDURES: After administration of xylazine for sedation, horses (n = 5/group) received R-/S-ketamine (2.2 mg/kg) or S-ketamine (1.1 mg/kg), IV, for anesthesia induction. Anesthesia was maintained with isoflurane in oxygen and R-/S-ketamine (1 mg/kg/h) or S-ketamine (0.5 mg/kg/h). Heart rate, invasive mean arterial pressure, and end-tidal isoflurane concentration were recorded before and during surgical stimulation. Arterial blood gases were evaluated every 30 minutes. Arterial ketamine and norketamine enantiomer plasma concentrations were quantified at 60 and 120 minutes. After surgery, horses were kept in a padded recovery box, sedated with xylazine, and video-recorded for evaluation of recovery quality by use of a visual analogue scale (VAS) and a numeric rating scale. RESULTS: Horses in the S-ketamine group had better numeric rating scale and VAS values than those in the R-/S-ketamine group. In the R-/S-ketamine group, duration of infusion was positively correlated with VAS value. Both groups had significant increases in heart rate and mean arterial pressure during surgical stimulation; values in the R-/S-ketamine group were significantly higher than those of the S-ketamine group. Horses in the R-/S-ketamine group required slightly higher end-tidal isoflurane concentration to maintain a surgical plane of anesthesia. Moderate respiratory acidosis and reduced oxygenation were evident. The R-norketamine concentrations were significantly lower than S-norketamine concentrations in the R-/S-ketamine group. CONCLUSIONS AND CLINICAL RELEVANCE: Compared with R-/S-ketamine, anesthesia recovery was better with S-ketamine infusions in horses.

Bronchial circulation after experimental lung transplantation: the effect of direct revascularization of a bronchial artery

Direct revascularization of a bronchial artery has been proposed as a measure to alleviate the problem of bronchial ischemia after lung transplantation. To assess the effect of restoration of arterial blood flow to the transplanted bronchus, bronchial mucosal blood flow was measured in a model of modified unilateral lung transplantation in pigs. Laser Doppler velocimetry (LDV) and radioisotope studies using radio-labeled erythrocytes (RI) were used to measure blood flow at the donor main carina (DC) and upper lobe carina (DUC) after 3 h of reperfusion. The recipient carina was used as a reference point; values obtained by LDV and RI were expressed as percentage of blood flow at the recipient carina. Two groups of animals were studied. In group 1 (n = 6) standard unilateral transplantation was performed; in group 2 (n = 6) a left bronchial artery was reimplanted into the descending thoracic aorta of the recipient. No differences were observed between the two groups with respect to preoperative or postoperative gas exchange or hemodynamics. In group 1, bronchial blood flow at the DC was 37.6 +/- 2.2% (LDV) and 44.1 +/- 14.8% (RI) of reference blood flow. At the DUC, blood flow was 54.9 +/- 7.7% (LDV) and 61.6 +/- 25.7% (RI) of normal flow. In group 2, blood flow was increased at the DC as measured by LDV (55.3 +/- 17.1%; p less than 0.05) and by RI (60.8 +/- 25.3%; p less than 0.2). A similar increase was found at the DUC (LDV: 81.8 +/- 19.3%; p less than 0.05; RI: 88.6 +/- 31.0%; p less than 0.2). It is concluded that there is a significant gradient of blood flow from intra- to extrapulmonary airways after lung transplantation. Reimplantation of a bronchial artery results in significant improvement of graft bronchial blood flow. Restoration of bronchial perfusion to normal levels, however, cannot be achieved, suggesting a possible defect in the microcirculation of the donor airways.

How accurately can the acetabular rim be trimmed in hip arthroscopy for pincer-type femoral acetabular impingement: a cadaveric investigation

PURPOSE: The purpose of this study was to evaluate the precision of central hip arthroscopy in the assessment and treatment of pincer-type femoroacetabular impingement (FAI) avoiding the posterolateral portal, with its close proximity to the main arterial blood supply of the femoral head, the medial circumflex femoral artery. METHODS: Seven human cadaveric hips underwent arthroscopic trimming of the acetabular labrum and rim along a preoperatively defined 105 degrees arc of resection for treatment of a presumed pincer-type lesion. After the arthroscopic procedure, all specimens were dissected and measured for evaluation of the location, quantity, and quality of the area undergoing resection. RESULTS: The difference between the actual and planned arc of resection was 18.7 degrees +/- 4.7 degrees (range, 2 degrees to 34 degrees). This was mainly because of a lack of accuracy in the presumed posterior starting point (PSP), with a mean deviation of 19 degrees +/- 3.4 degrees (range, 10 degrees to 36 degrees). Correlation analysis showed that variance in the arc of resection was mainly dependent on the PSP (r = 0.739, P = .058). CONCLUSIONS: Central hip arthroscopy is a feasible option in treating anterosuperior pincer-type FAI by use of the anterior and anterolateral portals only. This cadaveric study showed that there is a significant risk of underestimating the actual arc of resection compared with the planned arc of resection for posterosuperior pincer-type lesions because of the modest accuracy in determining the PSP of the resection. CLINICAL RELEVANCE: Accurate preoperative planning and arthroscopic identification of anatomic landmarks at the acetabular side are crucial for the definition of the appropriate starting and ending points in the treatment of pincer-type FAI. Whereas anterosuperior pincer-type lesions can be addressed very precisely with our technique, the actual resection of posterosuperior lesions averaged 19 degrees less than the planned resection, which may have clinical implications.

Increased circulating placental growth factor during percutaneous coronary intervention is associated with applied radiocontrast agent

BACKGROUND AND AIM OF THE STUDY: Recent studies have suggested placental growth factor (PlGF) and vascular endothelial growth factor (VEGF) as promising new biomarkers for risk stratification in acute coronary syndromes (ACS). However, little is known about the influence of percutaneous coronary intervention (PCI) on circulating PlGF and VEGF levels. METHODS: Thirty-five patients with ACS, 27 patients with stable coronary artery disease (sCAD), and nine healthy controls were enrolled in the study. Although all patients with ACS and 14 patients with stable angina pectoris underwent PCI, 13 patients with coronary artery disease required no revascularization (sCAD). PlGF and VEGF plasma concentrations were measured by immunoassay during and at the end of PCI and coronary angiography. RESULTS: Plasma PlGF levels were comparable in patients with ACS and sCAD on admission. Although coronary angiography or heparin alone did not alter PlGF and VEGF levels, immediately after PCI a dramatic increase was seen in circulating PlGF and a decrease in VEGF, which was independent of the clinical presentation of the patients, heparin administration, or the angiographic procedure itself, but was associated with the extent of coronary artery disease and the amount of the injected contrast media. In-vitro experiments revealed that radiocontrast agents induced the release of PlGF from endothelial cells without altering PlGF mRNA expression. CONCLUSION: Patients undergoing PCI exhibit an increase in circulating PlGF, probably caused by posttranslational modifications of radiocontrast agents in endothelial cells. Therefore, analysis of plasma PlGF and VEGF levels may consider the timing of blood sampling with respect to PCI and contrast media exposure.

Automatic algorithm for monitoring systolic pressure variation and difference in pulse pressure

BACKGROUND: Difference in pulse pressure (dPP) reliably predicts fluid responsiveness in patients. We have developed a respiratory variation (RV) monitoring device (RV monitor), which continuously records both airway pressure and arterial blood pressure (ABP). We compared the RV monitor measurements with manual dPP measurements. METHODS: ABP and airway pressure (PAW) from 24 patients were recorded. Data were fed to the RV monitor to calculate dPP and systolic pressure variation in two different ways: (a) considering both ABP and PAW (RV algorithm) and (b) ABP only (RV(slim) algorithm). Additionally, ABP and PAW were recorded intraoperatively in 10-min intervals for later calculation of dPP by manual assessment. Interobserver variability was determined. Manual dPP assessments were used for comparison with automated measurements. To estimate the importance of the PAW signal, RV(slim) measurements were compared with RV measurements. RESULTS: For the 24 patients, 174 measurements (6-10 per patient) were recorded. Six observers assessed dPP manually in the first 8 patients (10-min interval, 53 measurements); no interobserver variability occurred using a computer-assisted method. Bland-Altman analysis showed acceptable bias and limits of agreement of the 2 automated methods compared with the manual method (RV: -0.33% +/- 8.72% and RV(slim): -1.74% +/- 7.97%). The difference between RV measurements and RV(slim) measurements is small (bias -1.05%, limits of agreement 5.67%). CONCLUSIONS: Measurements of the automated device are comparable with measurements obtained by human observers, who use a computer-assisted method. The importance of the PAW signal is questionable.

A standardized protocol for the prevention of clinically relevant venous air embolism during neurosurgical interventions in the semisitting position

OBJECTIVE: We report the results and complications associated with standardized intraoperative management designed for the prevention of hemodynamically relevant venous air embolism during surgery performed in the semisitting position. METHODS: A protocol for preoperative evaluation and intraoperative monitoring was developed and applied in 187 consecutive patients who underwent surgery in the semisitting position between 1999 and 2004. The protocol included preoperative transesophageal echocardiography examination (TEE), intraoperative TEE monitoring, catheterization of the right atrium and a combination of fluid input, positive end expiratory pressure, and standardized positioning aiming at a positive pressure in the transverse and sigmoid sinuses. Data were collected retrospectively from the charts and intraoperative anesthesiological protocols of the patients for the incidence of clinically relevant air embolism (i.e., TEE-diagnosed air embolism plus a decrease in end tidal CO2 or hemodynamic changes) and other complications related to the semisitting position. RESULTS: Three cases (1.6%) of relevant venous air embolism occurred in 187 patients. Only 1 case (0.5%) was hemodynamically relevant, with temporary arterial blood pressure decrease and heart rate increase. Pneumatocephalus leading to lethargy was a frequent postoperative finding, which resolved spontaneously in all except 1 patient with epileptic seizure and oculomotor nerve palsy attributable to space-occupying subdurally trapped air, which had to be treated surgically. There was no permanent morbidity or mortality related to the semisitting position. CONCLUSION: Fear of massive venous air embolism is one reason for dramatic decline in the use of the semisitting position in neurosurgical practice. We found that strict adherence to a standardized protocol using TEE monitoring before and during surgery; exclusion of patients with patent foramen ovale; and a combination of positive end expiratory pressure, fluid input, and a standardized position aiming a positive pressure in the transverse and sigmoid sinuses helped to greatly minimize this complication to a rate of 0.5% for hemodynamically relevant events.