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Marc Koch

Publications and source records attributed to Marc Koch.

8 recordsLinked to original sources
PubMed2006

Assessment of thoracic epidural analgesia during general anesthesia using pupillary reflex dilation: a preliminary study.

OBJECTIVE: Pupillary reflex dilation (PRD) secondary to noxious stimulation accurately predicts sensory block during combined lumbar epidural/general anesthesia. Therefore, the adequacy of PRD-guided thoracic epidural infusion during general anesthesia for thoracotomy was studied. DESIGN: Prospective study. SETTING: University hospital. PARTICIPANTS: Thirteen patients undergoing thoracotomy. INTERVENTIONS: An epidural catheter was placed at the T3-T4 level with initial infusion rate of 5 mL/h of ropivacaine 0.5%. Propofol/remifentanil target-controlled infusion was used for induction and maintenance of general anesthesia. Remifentanil effect site concentration was maintained constant at 0.5 ng/mL during surgery. By using a portable pupillometer, PRD secondary to tetanic stimulation of the C8, T2, and T4 segments were evaluated. Ropivacaine flow rate was adapted half hourly, according to PRD testing and a predefined algorithm. At the end of surgery, PRD was tested in the 3 investigated segments, and general anesthesia was stopped. After emergence, these zones were tested for their sensitivity to cold. Pain was evaluated by using the visual analog scale. RESULTS: Pain scores were <3 of 10 in 84.6% of the patients. Mean PRD was 0.9 +/- 0.6 mm in unblocked levels versus 0.2 +/- 0.5 mm in blocked segments (p = 0.02). PRD >or= 0.5 mm was predictive of incomplete block (sensitivity 76%, specificity 79%, and positive predictive value 86%). PRD >or= 1 mm was highly predictive of inadequate block (sensitivity 73%, specificity 91%, and positive predictive value 94%). CONCLUSION: PRD-guided continuous thoracic epidural analgesia under low-dose remifentanil/propofol anesthesia is feasible and ensures good postoperative analgesia.

Amides↗
PubMed2006

Sublingual capnometry tracks microcirculatory changes in septic patients.

OBJECTIVE: To test the hypothesis that microcirculatory blood flow is the main determinant of sublingual carbon dioxide pressure in patients with septic shock. DESIGN: Prospective, open-label study. SETTING: A 31-bed medico-surgical department of intensive care. PATIENTS: Eighteen consecutive mechanically ventilated patients with septic shock. INTERVENTIONS: A 5 microg/kg x min dobutamine infusion was used to increase blood flow. METHODS: Sublingual carbon dioxide pressure was monitored using a microelectrode sensor, and sublingual microcirculation was assessed using orthogonal polarization spectral imaging. The sublingual carbon dioxide pressure gap was calculated as the difference between sublingual and arterial carbon dioxide pressures. In each patient, a nasogastric tonometry catheter was inserted for gastric mucosal carbon dioxide pressure measurement. The gastric carbon dioxide pressure gap was calculated as the difference between gastric mucosal and arterial carbon dioxide pressures. MEASUREMENTS AND RESULTS: Dobutamine infusion was associated with increases cardiac index and mixed venous blood oxygen saturation. Dobutamine infusion resulted in decreases in sublingual carbon dioxide pressure gap from 40+/-15 to 17+/-8 mmHg (p<0.01). There was a significant correlation between sublingual and gastric mucosal carbon dioxide pressures (r 2=0.61, p<0.05). At baseline, sublingual carbon dioxide pressure gap correlated with the proportion of well-perfused capillaries (r 2=0.80). The decrease in sublingual carbon dioxide pressure gap paralleled the increase in the proportion of well-perfused capillaries in each patient. CONCLUSIONS: Regional microcirculatory blood flow is the main determinant of sublingual carbon dioxide pressure. Sublingual capnometry could represent a simple, non-invasive method to monitor these microcirculatory alterations in septic patients.

Aged↗
PubMed2006

The effects of dobutamine on microcirculatory alterations in patients with septic shock are independent of its systemic effects.

OBJECTIVE: To evaluate the effects of dobutamine on microcirculatory blood flow alterations in patients with septic shock. DESIGN: Prospective, open-label study. SETTING: A 31-bed, medico-surgical intensive care unit of a university hospital. PATIENTS: Twenty-two patients with septic shock. INTERVENTIONS: Intravenous administration of dobutamine (5 mug/kg.min) for 2 hrs (n = 22) followed by the addition of 10 M acetylcholine (topically applied, n = 10). MEASUREMENTS AND MAIN RESULTS: Complete hemodynamic measurements were obtained before and after dobutamine administration. In addition, the sublingual microcirculation was investigated with an orthogonal polarization spectral imaging technique before and after dobutamine administration and after topical application of acetylcholine. Dobutamine significantly improved capillary perfusion (from 48 +/- 15 to 67 +/- 11%, p = .001), but with large individual variation, whereas capillary density remained stable. The addition of topical acetylcholine completely restored capillary perfusion (98 +/- 1%, p = .001) and capillary density. The changes in capillary perfusion during dobutamine administration were not related to changes in cardiac index (p = .45) or arterial pressure (p = .29). Interestingly, the decrease in lactate levels was proportional to the improvement in capillary perfusion (y = 0.07 - 0.02x, r = .46, p = .005) but not to changes in cardiac index (p = .55). CONCLUSIONS: The administration of 5 mug/kg.min dobutamine can improve but not restore capillary perfusion in patients with septic shock. These changes are independent of changes in systemic hemodynamic variables.

Acetylcholine↗
PubMed2006

Effects of drotrecogin alfa activated on microcirculatory alterations in patients with severe sepsis.

OBJECTIVE: Microvascular alterations may play an important role in the development of sepsis-induced organ dysfunction. Drotrecogin alfa activated (DAA) improves outcome in patients with severe sepsis, but its precise mechanism of action is not entirely defined. We investigated whether DAA can influence microcirculatory alterations in patients with severe sepsis. DESIGN: Prospective, nonrandomized study. SETTING: A 31-bed, medico-surgical intensive care unit of a university hospital. PATIENTS: Forty adult patients with severe sepsis who met the EU criteria for DAA administration. INTERVENTIONS: Twenty patients received the drug (DAA) and 20 had a contraindication to DAA administration (control). MEASUREMENTS AND MAIN RESULTS: An orthogonal polarization spectral imaging technique was used to visualize the sublingual microcirculation. In all patients, measurements were obtained at baseline, 4 hrs later, and then every 24 hrs for up to 7 days. In patients receiving DAA, measurements were also obtained just before and 4 hrs after the end of DAA infusion. The two groups were well matched for severity of disease, number of failing organs, and the degree of microvascular alterations at baseline. The proportion of perfused capillaries increased in the DAA treated patients already at 4 hrs (from 64% [51-80%] to 84% [71-88%], p < .01) but not in the control group (from 67% [59-76%] to 68% [61-71%], p = not significant). Microvascular perfusion decreased transiently at the end of DAA infusion. The improvement in microvascular blood flow was associated with a more rapid resolution of hyperlactatemia. CONCLUSIONS: DAA administration rapidly improves sepsis-induced microvascular alterations, whereas its cessation is associated with a transient deterioration.

Aged↗
PubMed2005

Pulse pressure variations to predict fluid responsiveness: influence of tidal volume.

OBJECTIVE: To evaluate the influence of tidal volume on the capacity of pulse pressure variation (DeltaPP) to predict fluid responsiveness. DESIGN: Prospective interventional study. SETTING: A 31-bed university hospital medico-surgical ICU. PATIENTS AND PARTICIPANTS: Sixty mechanically ventilated critically ill patients requiring fluid challenge, separated according to their tidal volume. INTERVENTION: Fluid challenge with either 1,000 ml crystalloids or 500 ml colloids. MEASUREMENTS AND RESULTS: Complete hemodynamic measurements including DeltaPP were obtained before and after fluid challenge. Tidal volume was lower than 7 ml/kg in 26 patients, between 7-8 ml/kg in 9 patients, and greater than 8 ml/kg in 27 patients. ROC curve analysis was used to evaluate the predictive value of DeltaPP at different tidal volume thresholds, and 8 ml/kg best identified different behaviors. Overall, the cardiac index increased from 2.66 (2.00-3.47) to 3.04 (2.44-3.96) l/min m(2) ( P <0.001). It increased by more than 15% in 33 patients (fluid responders). Pulmonary artery occluded pressure was lower and DeltaPP higher in responders than in non-responders, but fluid responsiveness was better predicted with DeltaPP (ROC curve area 0.76+/-0.06) than with pulmonary artery occluded pressure (0.71+/-0.07) and right atrial (0.56+/-0.08) pressures. Despite similar response to fluid challenge in low (<8 ml/kg) and high tidal volume groups, the percent of correct classification of a 12% DeltaPP was 51% in the low tidal volume group and 88% in the high tidal volume group. CONCLUSIONS: DeltaPP is a reliable predictor of fluid responsiveness in mechanically ventilated patients only when tidal volume is at least 8 ml/kg.

Aged↗
PubMed2003

Acute barium intoxication and hemodiafiltration.

We report a case of severe hypokalemia and flaccid muscle paralysis following a suicide attempt associating the calcium channel blocker amlodipine, the antidepressant fluoxetine and barium carbonate. Despite rapid correction of severe, life-threatening hypokalemia, areflexic quadriplegia persisted, suggesting a direct effect of barium on muscle cells. Continuous veno-venous hemodiafiltration (CVVHDF) was initiated. We determined barium concentration in the urine, plasma, and hemodiafiltrate during CVVHDF. We subsequently calculated the amounts of barium eliminated both by the CVVHDF and the kidneys. CVVHDF triples the measured barium elimination, reduced serum barium half-life by a factor of three, stabilized serum potassium levels, and rapidly improved motor strength, with complete neurological recovery within 24 h. Presentation and treatment of barium intoxication are discussed.

Amlodipine↗