Biomedical subjects

Stephan M Jakob

Publications and source records attributed to Stephan M Jakob.

31 records · Page 2Linked to original sources

PubMed2004

Changes in splanchnic circulation during an alveolar recruitment maneuver in healthy porcine lungs.

UNLABELLED: Recruitment maneuvers (RM) are advocated as a complement to mechanical ventilation during anesthesia and in acute lung injury. However, they produce high intrathoracic pressures and volumes that may compromise hemodynamics. Our aim was to analyze the effect of a RM on hemodynamics in 10 anesthetized pigs. We assessed carotid, pulmonary, femoral, and hepatic arterial pressures, hepatic and portal venous pressures, total splanchnic (celiac trunk + superior mesenteric artery), hepatic, splenic, renal, and carotid arterial flows, and portal venous flow. We recorded hemodynamics, respiratory mechanics and blood gases before and at 8 min after RM (sustained inflation to 40 cm H(2)O of airway pressure lasting 20 s). Hemodynamics were also measured during RM, and at 1, 3, and 5 min after RM. All flows (P = 0.030) and arterial pressures (P < or = 0.048) decreased during RM, whereas venous pressures increased (P = 0.030). Flows and pressures returned to 75%-109% of baseline immediately after RM. Total splanchnic, renal and portal flows remained decreased at 8 min after RM (P < or = 0.042). Oxygenation did not change, and respiratory mechanics improved after the RM. RM produced a marked, though transitory, impairment of blood flow in all studied vessels. Despite prompt partial recovery, total splanchnic circulation remained reduced at 8 min after RM. This residual decrease may present a risk in conditions with markedly compromised circulatory reserves. IMPLICATIONS: Recruitment maneuvers (RM) produce high intrathoracic pressures and volumes that may compromise hemodynamics. We found a marked transient impairment of hemodynamics during a RM in 10 anesthetized pigs. At 8 min after RM, blood flow remained reduced in the celiac trunk, superior mesenteric, and renal arteries, as well as in the portal vein. This residual decrease may present a risk in conditions with markedly compromised circulatory reserves.

Animals↗

PubMed2004

Measuring depth of sedation with auditory evoked potentials during controlled infusion of propofol and remifentanil in healthy volunteers.

Avoiding excessively deep levels of sedation is a major problem in intensive care patients. We studied whether clinically relevant levels of sedation can be objectively assessed using long latency auditory evoked potentials. We measured the auditory evoked potentials at 100 ms after the stimulus (N100) in 10 healthy volunteers during stepwise increasing, clinically relevant levels of sedation (Ramsay score [RS] 2-4). The volunteers were studied on three separate occasions and received an infusion of either propofol or a combination of propofol and remifentanil. Effects of remifentanil infusion alone were tested during target controlled infusion (target plasma concentrations: 1, 2, and 3 ng/mL). Remifentanil did not affect evoked potential amplitudes and latencies. During both propofol-induced and propofol/remifentanil-induced sedation, the N100 amplitude decreased similarly without an effect on the latencies as the level of sedation increased from Ramsay score 2 to Ramsay score 4 (P < 0.01). At the same clinical level of sedation, propofol plasma concentrations were larger when sedation was achieved by propofol alone (propofol versus propofol/remifentanil, RS 3: 2.12 mug/mL +/- 0.51 versus 1.32 +/- 0.43, P < 0.01; RS 4: 3.37 +/- 0.47 versus 1.86 +/- 0.34, P < 0.01). Our results suggest that long latency auditory evoked potentials provide an objective electrophysiological analog to the clinical assessment of sedation independent of the sedation regime used.

Adult↗

PubMed2003

Changes in regional blood flow and pCO(2) gradients during isolated abdominal aortic blood flow reduction.

OBJECTIVE: pCO(2) gradients are used for the assessment of splanchnic regional and local mucosal blood flow changes in experimental and clinical research. pCO(2) gradients may not parallel blood flow changes because of concomitant changes in metabolism, hemoglobin, temperature, and the Haldane effect. DESIGN AND SETTING: A randomized, controlled animal experiment in a university experimental research laboratory. INTERVENTIONS: An extracorporeal shunt with reservoir and roller pump was inserted between the proximal and the distal abdominal aorta in 16 pigs. In animals randomized to the low-flow group ( n=8) splanchnic perfusion was reduced by running the roller pump. At baseline and after 45 min of stable shunt flow superior mesenteric artery, celiac trunk, spleen artery, and portal vein blood flows and regional venous-arterial and jejunal and gastric mucosal-arterial pCO(2) gradients were measured, and the respective regional O(2) consumption rates (VO(2)) calculated. MEASUREMENTS AND RESULTS: In the low-flow group all regional blood flows and the associated VO(2) decreased to roughly 50% of baseline values, and hemoglobin decreased from 7.3 (4.4-9.6) g/dl to 5.7 (4.1-8.9) g/dl. Decreasing regional blood flows were consistently associated with increasing regional and mucosal pCO(2) gradients. CONCLUSIONS: During isolated reduction in abdominal aortic blood flow there is no preferential distribution to any splanchnic vascular bed and changes in regional pCO(2) gradients reflect consistently the associated blood blow changes.

Animals↗

PubMed2003

Change in stroke volume in response to fluid challenge: assessment using esophageal Doppler.

OBJECTIVE: To compare two methods of assessing a change in stroke volume in response to fluid challenge: esophageal Doppler and thermodilution with the pulmonary artery catheter. DESIGN: Prospective study. SETTING: Department of Intensive Care of a university medical center. PATIENTS: 19 adult patients, intubated and sedated, with a pulmonary catheter and a clinical indication for a fluid challenge. INTERVENTIONS: Two examiners independently assessed the effect of a fluid challenge on stroke volume and cardiac output with esophageal Doppler. Thermodilution performed by an independent clinician was used as the reference. Between-method variation and interobserver variability of the Doppler method were assessed. MEASUREMENTS AND RESULTS: There were no differences in stroke volume and cardiac output before volume challenge when measured with either of the two methods or by the two examiners using the esophageal Doppler. Despite a small bias between the methods and the two examiners using the esophageal Doppler (overall bias for cardiac output 0.3 l/min), the precision was poor (1.8 l/min). CONCLUSIONS: The esophageal Doppler method is a non-invasive alternative to the pulmonary artery catheter for the assessment of stroke volume in critically ill patients. Measurement of stroke volume response to fluid challenge using esophageal Doppler shows substantial interobserver variability. Despite the poor precision between methods and investigators, similar directional changes in stroke volume can be measured.

Adult↗

PubMed2003

Diagnosis and management of electrolyte emergencies.

Electrolyte and fluid imbalances are disorders frequently observed in critical care patients. In many instances patients are asymptomatic, but they may also present with neurological alterations, severe muscle weakness, nausea and vomiting or cardiovascular emergencies. Therefore, a pathophysiological understanding of these disorders is necessary for initiating an appropriate therapy. After a precise history-including drug prescriptions-has been obtained from the patient or his/her relatives, determination of the hydration status of the patient and measurement of acid-base status, plasma and urine osmolality and electrolytes are the first steps in the assessment of the disease. Once a diagnosis has been established, great attention has to be paid to the rate at which the disorder is corrected because this-if inappropriate-may cause more severe damage to the patient than the disease itself. This chapter addresses the initial diagnostic and therapeutic steps of the most common electrolyte emergencies.

Calcium↗

PubMed2003

Splanchnic blood flow in low-flow states.

IMPLICATIONS: Insufficient splanchnic blood flow in critically ill patients is the result of a multitude of different diseases, treatment modalities and their interplay, and is associated with increased morbidity and mortality. A combination of diminished and heterogeneous mesenteric blood flow, impaired or exhausted regulatory mechanisms and adverse drug effects may coexist with normal systemic hemodynamics.

Animals↗

PubMed2003

Apparent heterogeneity of regional blood flow and metabolic changes within splanchnic tissues during experimental endotoxin shock.

UNLABELLED: We conducted a randomized, controlled experiment of prolonged lethal endotoxin shock in pigs aiming at 1) simultaneously measuring perfusion at different parts of the gut to study the potential heterogeneity of blood flow within the splanchnic region; 2) studying the association among regional blood flows, oxygen supply, and different metabolic markers of perfusion; and 3) analyzing the association between histological gut injury and markers of perfusion and metabolism. The primary response to endotoxin was a decrease in systemic and splanchnic blood flow followed by hyperdynamic systemic circulation. Redistribution of blood flows occurred within the splanchnic circulation: superior mesenteric artery blood flow was maintained, whereas celiac trunk blood flow was compromised. Mucosal to arterial PCO(2) gradients did not reflect changes in total splanchnic perfusion, but they were associated with regional blood flows during the hypodynamic phase of shock. During hyperdynamic systemic circulation, PCO(2) gradients increased heterogeneously in the gastrointestinal tract, whereas luminal lactate increased only in the colon. Histological analysis revealed mucosal epithelial injury only in the colon. We conclude that markers of perfusion and metabolism over one visceral region do not reflect perfusion and metabolism in other splanchnic vascular areas. Intestinal mucosal epithelial injury occurs in the colon during 12 h of endotoxin shock while the epithelial injury is still absent in the jejunum. Hyperdynamic and hypotensive shock induces gut luminal lactate release in the colon but not in the jejunum. The association or causality between the mucosal epithelial injury and luminal lactate release remains to be elucidated. IMPLICATIONS: Surrogate regional markers of tissue perfusion over one region do not reflect the state of perfusion over another. Therefore, regional metabolic monitoring (microdialysis) in multiple locations is needed. Although tonometry does not differentiate between macro-level regional perfusion defect and tissue injury, intestinal luminal microdialysis detects mucosal lactate release, which may be associated with epithelial injury. The degree of correlation or causality between the two remains to be evaluated.

Animals↗

PubMed2002

Clinical review: splanchnic ischaemia.

Inadequate splanchnic perfusion is associated with increased morbidity and mortality, particularly if liver dysfunction coexists. Heart failure, increased intra-abdominal pressure, haemodialysis and the presence of obstructive sleep apnoea are among the multiple clinical conditions that are associated with impaired splanchnic perfusion in critically ill patients. Total liver blood flow is believed to be relatively protected when gut blood flow decreases, because hepatic arterial flow increases when portal venous flow decreases (the hepatic arterial buffer response [HABR]). However, there is evidence that the HABR is diminished or even abolished during endotoxaemia and when gut blood flow becomes very low. Unfortunately, no drugs are yet available that increase total hepato-splanchnic blood flow selectively and to a clinically relevant extent. The present review discusses old and new concepts of splanchnic vasoregulation from both experimental and clinical viewpoints. Recently published trials in this field are discussed.

Animals↗

PubMed2002

ARDS. Monitoring tissue perfusion.

A clinically feasible method for assessing regional splanchnic perfusion is still lacking. Methods used for research purposes demonstrate that the effects of current therapies on splanchnic perfusion are not predictable in intensive care patients with and without ARDS. Tonometry, laser Doppler flowmetry, and spectrophotometry have been used to assess splanchnic perfusion. Combining the available methods in different parts of the gastrointestinal tract may help assess splanchnic perfusion more accurately in the near future.

Adult↗

PubMed2002

Acute normovolemic hemodilution improves oxygenation in ischemic flap tissue.

BACKGROUND: The flaps used in reconstructive surgery are prone to ischemia and hypoxia, which imply a considerable risk of wound-healing complications. During normovolemic hemodilution, the oxygenation may further deteriorate because of the lack of erythrocytes or improve because of increased microcirculatory blood flow. The aim of this study was to investigate the net effect of normovolemic hemodilution of various degrees on the microcirculation and oxygenation in ischemic flap tissue in adult minipigs. METHODS: A rectangular flap was raised in the middle of the epigastrium, consisting of an adequately perfused portion and a partly ischemic portion. The animals were randomly assigned to either the control group (n = 10) or the experimental group (n = 10) receiving graded normovolemic hemodilution with 6% hydroxyethyl starch 200-0.5. RESULTS: Normovolemic hemodilution caused a significant linear increase in total blood flow to the flap (measured by transit time flowmetry). In the ischemic flap tissue, both oxygen tension (measured by polarographic cells) and venous base excess were transiently improved during hemodilution (F = 4.79 and P = 0.019 for the regression of tissue oxygen tension on hemoglobin and hemoglobin squared, and F = 4.18 and P = 0.029 for base excess). The expected values reached a peak at hemoglobin concentrations of 9.1 and 8.5 g/dl, respectively. The measured values at this level of hemodilution were 17 +/- 10.7 mmHg (mean +/- SD) versus 7.6 +/- 1.9 mmHg (baseline) for oxygen tension and -1.7 +/- 3.4 versus -5.6 +/- 4.1 mM for venous base excess. CONCLUSIONS: Our results suggest that the oxygenation in ischemic and hypoxic flap tissue may be improved by normovolemic hemodilution. The maximal benefit may be expected at a hemoglobin concentration at or slightly less than 9 g/dl.

Animals↗

PubMed2002

Effect of dopamine-induced changes in splanchnic blood flow on MEGX production from lidocaine in septic and cardiac surgery patients.

The production of monoethylglycine xylidide (MEGX) from lidocaine is thought to be dependent on hepatic blood flow. We assessed the relationship between hepatosplanchnic blood flow, lidocaine uptake, and the production of MEGX from lidocaine in seven patients after cardiac surgery and in nine septic patients. Systemic (pulmonary artery catheter) and splanchnic (hepatic vein catheter and dye dilution) hemodynamics and arterial and hepatic venous lidocaine and MEGX concentrations were measured after a lidocaine bolus injection (1 mg/kg) before and 90 min after increasing cardiac output by at least 25% with dopamine. Dopamine infusion [in cardiac surgery patients 4.2 (1.4-8.5) microg x kg(-1) x min(-1) (median, range) and in septic patients 4.0 (2.1-9.0) microg x kg(-1) x min(-1)] increased splanchnic blood flow in cardiac surgery patients from 0.65 (0.12) L x min(-1) x m(-2) to 0.84 (0.14) L x min(-1) x m(-2) mean (standard deviation) P = 0.018) and in septic patients from 0.91 (0.32) L x min(-1) x m(-2) to 1.12 (0.40) L x min(-1) x m(-2) (P = 0.038). Splanchnic MEGX production for the 30 min after lidocaine injection was higher in cardiac surgery patients than in septic patients both at baseline [4130 (1100) microg x m(-2) vs. 930 (420) microg x m(-2) (P < 0.005)] and afterdopamine infusion [4480 (1000) microg x m(-2) vs. 1090 (620) microg x m(-2) (P = 0.005)]. We found no correlation between changes in MEGX production and changes in splanchnic blood flow. Patients with sepsis have severe impairment of cytochrome P450-dependent liver function, which is not influenced by acute changes in hepatosplanchnic blood flow. MEGX production cannot be used as an estimate of changes in splanchnic blood flow.

Adult↗

PubMed2002

Effects of dopamine on systemic and regional blood flow and metabolism in septic and cardiac surgery patients.

Dopamine is used in the clinical setting to support cardiac output and blood pressure and to improve diuresis. Experimental studies suggest that dopamine may reduce splanchnic perfusion and redistribute blood flow locally. To assess the effects of dopamine on splanchnic perfusion, we used dopamine to increase cardiac output by 25% in nine septic patients and 11 patients after cardiac surgery. Systemic (pulmonary artery catheter) and splanchnic (hepatic vein catheter and dye dilution) hemodynamics and oxygen transport were measured at baseline and 90 min after increasing the cardiac output. Dopamine infusion [in cardiac surgery patients 4.2 (1.4-8.5) microg x kg(-1) x min(-1) (median, range) and in septic patients 4.0 (2.1-9.0) microg x kg(-1) x min(-1)] increased splanchnic blood flow in cardiac surgery patients from 0.61 (0.13) L x min(-1) x m(-2) to 0.82 (0.13) L x min(-1) x m(-2) [mean (standard deviation; SD); P = 0.018] and in septic patients from 0.91 (0.32) L x min(-1) x m(-2) to 1.12 (0.40) L x min(-1) x m(-2) (P = 0.038). Splanchnic oxygen consumption increased in cardiac surgery patients from 39 (5) mL x min(-1) x m(-2) to 46 (6) mL x min(-1) x m(-2) (P = 0.003) but decreased in septic patients from 61 (19) mL x min(-1) x m(-2) to 51 (17) L x min(-1) x m(-2) (p = 0.021). Because of the unexpected results, we compared these data post hoc with data obtained from another group of 15 septic patients with acute lung injury, where dobutamine was used to increase cardiac output in a similar design. Dobutamine in these patients [6.4 (4.2-9.5) microg x kg(-1) x min(-1)] increased splanchnic blood flow from 1.20 (0.44) L x min(-1) x m(-2) to 1.43 (0.57) L x min(-1) x m(-2) (P = 0.008), while splanchnic oxygen consumption did not change 72 (25) mL x min(-1) x m(-2) vs. 76 (22) mL x min(-1) x m(-2) (not significant)]. The reduction of splanchnic oxygen consumption by dopamine in sepsis suggests an impairment of hepatosplanchnic metabolism despite an increase in regional perfusion. The safety and indications of dopamine use in sepsis should be re-evaluated.

Adult↗

PubMed2002

Splanchnic vasoregulation during mesenteric ischemia and reperfusion in pigs.

We evaluated the hepatic arterial buffer response (HABR) to portal vein (PV) occlusion during 2 h of reduced superior mesenteric arterial blood flow (median 2 mL min(-1) kg(-1), range of 1-3 mL min(-1) kg(-1)) and 1 h of reperfusion in seven pigs and in seven controls. In animals with reduced mesenteric blood flow, celiac trunk blood flow (Qtr) increased during mesenteric hypoperfusion from 4 +/- 1 mL min(-1) kg(-1) (mean +/- SD) to 16 +/- 3 mL min(-1) kg(-1) (P = 0.028), and hepatic arterial blood flow (Qha) increased from 2 +/- 1 to 10 +/- 4 mL min(-1) kg(-1) (P= 0.018). The extra-hepatic fraction of Qtr (Qtr-Qha) also increased (P = 0.028). In controls, Qtr and Qha also increased, but to lower levels. At baseline, acute PV occlusion increased Qha by 5.0 +/- 2.8 mL min(-1) kg(-1) (P < 0.001), whereas Qtr-Qha decreased by 1.6 +/- 1.6 mL min(-1) kg(-1) (P = 0.007). After 120 min of reduced mesenteric blood flow, the HABR was exhausted (change in Qha to PV occlusion of 0.7 +/- 1.6 mL min(-1) kg(-1) [P= 0.27]). The efficacy of the HABR was also reduced in controls animals. Despite increased cardiac output, all flows from the celiac trunk decreased during reperfusion (P = 0.028) and the HABR partially recovered. We conclude that reduced mesenteric perfusion impairs the HABR, which recovers only partially after reperfusion. The distribution of the increased celiac trunk flow secondary to PV occlusion ranges from increased HABR and decreased non-hepatic blood flow (a steal) to decreased hepatic arterial blood flow and increased non-hepatic blood flow (an inverse steal).

Adaptation, Physiological↗