Protective ventilation with high versus low positive end-expiratory pressure during one-lung ventilation for thoracic surgery (PROTHOR): study protocol for a randomized controlled trial

BACKGROUND

Postoperative pulmonary complications (PPC) may result in longer duration of in-hospital stay and even mortality. Both thoracic surgery and intraoperative mechanical ventilation settings add considerably to the risk of PPC. It is unclear if one-lung ventilation (OLV) for thoracic surgery with a strategy of intraoperative high positive end-expiratory pressure (PEEP) and recruitment maneuvers (RM) reduces PPC, compared to low PEEP without RM.

METHODS

PROTHOR is an international, multicenter, randomized, controlled, assessor-blinded, two-arm trial initiated by investigators of the PROtective VEntilation NETwork. In total, 2378 patients will be randomly assigned to one of two different intraoperative mechanical ventilation strategies. Investigators screen patients aged 18 years or older, scheduled for open thoracic or video-assisted thoracoscopic surgery under general anesthesia requiring OLV, with a maximal body mass index of 35 kg/m2, and a planned duration of surgery of more than 60 min. Further, the expected duration of OLV shall be longer than two-lung ventilation, and lung separation is planned with a double lumen tube. Patients will be randomly assigned to PEEP of 10 cmH2O with lung RM, or PEEP of 5 cmH2O without RM. During two-lung ventilation tidal volume is set at 7 mL/kg predicted body weight and, during OLV, it will be decreased to 5 mL/kg. The occurrence of PPC will be recorded as a collapsed composite of single adverse pulmonary events and represents the primary endpoint.

DISCUSSION

PROTHOR is the first randomized controlled trial in patients undergoing thoracic surgery with OLV that is adequately powered to compare the effects of intraoperative high PEEP with RM versus low PEEP without RM on PPC. The results of the PROTHOR trial will support anesthesiologists in their decision to set intraoperative PEEP during protective ventilation for OLV in thoracic surgery.

TRIAL REGISTRATION

The trial was registered in clinicaltrials.gov ( NCT02963025 ) on 15 November 2016.

[Extravasation: a rare complication of central venous cannulation? Case report of an imminent erosion of the common carotid artery]

Extravasation is the non-intentional leakage of substances/solutions into the perivascular or subcutaneous space that can result in significant tissue damage. The extent of destruction depends on the properties of the substance, its concentration, and the amount applied. Substances known to cause severe tissue damage include certain chemotherapeutic agents, vasoactive substances, concentrated electrolytes, and other hyperosmolar solutions. Extravasation can be avoided by meticulous monitoring of venous access. When extravasation occurs, the infusion should be stopped immediately. Substances known to cause tissue damage should be removed from perivascular or subcutaneous space within 24 hours by local incision and irrigation. A delay in early treatment may necessitate more extensive surgical debridement and skin coverage operations. Since the extent of deep soft tissue damage is difficult to predict and is often underestimated, a magnetic resonance imaging should be performed before surgery. We report here on a 73-year-old patient, in whom extravasation of potassium-chloride from a dislocated multi-lumen central venous catheter led to a life-threatening skin and soft-tissue necrosis of the neck. This article provides an overview of common vesicants, theories of tissue destruction, potential risk factors, guidelines for prevention, and current treatment strategies.

[Diagnostic approach to sepsis - state of the art]

Early diagnosis of the different severities of septic inflammation is important for early implementation of specific therapies. Sepsis and severe sepsis are accompanied by clinical and laboratory signs of systemic inflammation. However, patients suffering from non-infectious inflammation may present with similiar signs and symptoms making it difficult to diagnose infection based on clinical findings alone. Bacteriological evidence of sepsis, though definitive and specific, may not be obtainable, is time-consuming and even may not occur concurrently with clinical signs of sepsis. It is therefore important to identify markers, which, by enabling an early diagnosis of sepsis and organ dysfunction, would allow early specific therapeutic interventions. Wheras C-reactive Protein is a more sensitive parameter for the diagnosis of non-systemic infections, Procalcitonin seems to be a useful parameter to improve the diagnosis and monitoring of therapy in patients with severe sepsis and septic shock.

The effects of increasing concentrations of isoflurane and desflurane on pulmonary perfusion and systemic oxygenation during one-lung ventilation in pigs

During one-lung ventilation (OLV), hypoxic pulmonary vasoconstriction (HPV) reduces venous admixture and attenuates the decrease in arterial oxygen tension by diverting blood from the nonventilated lung to the ventilated lung. In vitro, desflurane and isoflurane depress HPV in a dose-dependent manner. Accordingly, we studied the effects of increasing concentrations of desflurane and isoflurane on pulmonary perfusion, shunt fraction, and PaO(2) during OLV in vivo. Fourteen pigs (30-42 kg) were anesthetized, tracheally intubated, and mechanically ventilated. After placement of femoral arterial and thermodilution pulmonary artery catheters, a left-sided double-lumen tube (DLT) was placed via tracheotomy. After DLT placement, FIO(2) was adjusted at 0.8 and anesthesia was continued in random order with 3 concentrations (0.5, 1.0, and 1.5 minimal alveolar concentrations) of either desflurane or isoflurane. Differential lung perfusion was measured with colored microspheres. All measurements were made after stabilization at each concentration. Whereas mixed venous PO(2), mean arterial pressure, cardiac output, nonventilated lung perfusion, and shunt fraction decreased in a dose-dependent manner, PaO(2) remained unchanged with increasing concentrations of desflurane and isoflurane during OLV. In conclusion, increasing concentration of desflurane and isoflurane did not impair oxygenation during OLV in pigs.

IMPLICATIONS

In an animal model of one-lung ventilation, increasing concentrations of desflurane and isoflurane dose-dependently decreased shunt fraction and perfusion of the nonventilated lung and did not impair oxygenation. The decreases in shunt fraction are likely the result of anesthetic-induced marked decreases in cardiac output and mixed venous saturation.

Lung perfusion affects preload assessment and lung water calculation with the transpulmonary double indicator method

OBJECTIVES

The transpulmonary double indicator method uses intra- and extravascular indicators to calculate cardiac output, intrathoracic blood volume, global end-diastolic volume, and extravascular lung water content. Since lung perfusion may be of importance during these measurements, we studied the effects of pulmonary blood flow occlusion on measurements obtained with this method.

SETTING

Experimental animal facility of a University department.

METHODS AND INTERVENTIONS

In seven pigs, the branch of the pulmonary artery perfusing the lower and middle lobe of the right lung was occluded. Measurements before, during, and after the occlusion were made with a pulmonary artery catheter and a commonly used transpulmonary double indicator catheter and device.

MEASUREMENTS AND RESULTS

Occlusion of the right lower and middle lobe branch of the pulmonary artery increased mean pulmonary pressure (before occlusion: 24+/-1, during occlusion: 32+/-2, after reopening 25+/-1 mmHg; P<0.05), increased right ventricular end-diastolic volume (172+/-34, 209+/-21, 174+/-32 ml, respectively; P<0.05), decreased intrathoracic blood volume (998+/-39, 894+/-48, 1006+/-49 ml, respectively; P<0.05), and decreased extravascular lung water (7.2+/-0.5, 4.2+/-0.4, 6.9+/-0.4 ml/kg, respectively; P<0.05) without causing significant changes in cardiac output. All changes were reversible upon reopening the vessel.

CONCLUSIONS

These data show that the transpulmonary double indicator method may underestimate extravascular lung water and right ventricular preload when the perfusion to parts of the lung is obstructed.

Acute G-CSF therapy is not protective during lethal E. coli sepsis

We investigated whether decreases in circulating polymorphonuclear neutrophils (PMN) during lethal Escherichia coli (E. coli) sepsis in canines are related to insufficient host granulocyte colony-stimulating factor (G-CSF). Two-year-old purpose-bred beagles had intraperitoneal E. coli-infected or -noninfected fibrin clots surgically placed. By 10 to 12 h following clot, both infected survivors and nonsurvivors had marked increases (P = 0.001) in serum G-CSF levels (mean peak G-CSF ng/ml +/- SE, 1,931 +/- 364 and 2,779 +/- 681, respectively) compared with noninfected controls (134 +/- 79), which decreased at 24 to 48 h. Despite increases in G-CSF, infected clot placement caused delayed (P = 0.06) increases in PMN (mean +/- SE change from baseline in cells x 10(3)/mm(3) at 24 and 48 h) in survivors (+3.9 +/- 3.9 and +13.8 +/- 3.6) compared with noninfected controls (+13.1 +/- 2.8 and +9.1 +/- 2.5). Furthermore, infected nonsurvivors had decreases in PMN (-1.4 +/- 1.0 and -1.1 +/- 2.3, P = 0.006 compared with the other groups). We next investigated whether administration of G-CSF immediately after clot placement and continued for 96 h to produce more rapid and prolonged high levels of G-CSF after infection would alter PMN levels. Although G-CSF caused large increases in PMN compared with control protein from 2 to 48 h following clot in noninfected controls, it caused much smaller increases in infected survivors and decreases in infected nonsurvivors (P = 0.03 for the ordered effect of G-CSF comparing the three groups). Thus insufficient host G-CSF is unlikely the cause of decreased circulating PMN in this canine model of sepsis. Other factors associated with sepsis either alone or in combination with G-CSF itself may reduce increases or cause decreases in circulating PMN.

Anti-tumor necrosis factor therapy in sepsis: update on clinical trials and lessons learned

OBJECTIVE

Tumor necrosis factor (TNF) is an important mediator involved in the pathogenesis of sepsis. We review clinical studies investigating the efficacy of anti-TNF therapy in decreasing mortality rates in septic patients.

DATA SOURCES

We conducted a computerized bibliographic search of randomized, clinical, multicenter trials studying the effects of anti-TNF therapy in the treatment of sepsis. We included all primary studies, reviewed all published meta-analyses, and contacted primary investigators of multicenter trials where necessary.

DATA SYNTHESIS

Almost all randomized studies targeting TNF during sepsis show a small, albeit nonsignificant, benefit in decreasing mortality. Strategies using monoclonal antibodies are more effective than are strategies using TNF receptor proteins. Analysis of randomized multicenter trials shows a small but significant benefit with anti-TNF therapeutic strategies. Furthermore, a recent study in 2634 septic patients using a murine anti-TNF antibody shows a 3.6% significant benefit in reducing mortality.

CONCLUSIONS

Anti-TNF strategies are only partially effective in patients with sepsis. Although individual studies show small, nonsignificant benefits, analysis of all trial data as well as data from a recent trial in a large population of septic patients show that anti-TNF strategies may confer a small survival benefit. Better characterization of patients and a more multimodal approach by concomitantly targeting other mediators involved in sepsis may be helpful in enlarging the clinical benefit of anti-TNF therapy.

Oxygenation during one-lung ventilation: the effects of inhaled nitric oxide and increasing levels of inspired fraction of oxygen

We studied whether inhaled nitric oxide (NO) would improve arterial oxygen tension (PaO(2)) and reduce the occurrence of oxygen saturation of hemoglobin (O(2)Hb) < 90% during one-lung ventilation (OLV). One-hundred-fifty-two patients were ventilated either with or without NO (20 ppm) with an inspired fraction of oxygen (FIO(2)) of either 0.3, 0.5, or 1.0 during OLV. Anesthesia was induced and maintained with propofol, remifentanil, and rocuronium IV, and lung separation was achieved with a double-lumen tube. During OLV, we set positive end-expiratory pressure at 5 cm H(2)O, peak pressure at 30 cm H(2)O, and end-tidal CO(2) at 30 mm Hg. The nonventilated lung was opened to room air and collapsed. During OLV, three consecutive measurements were performed every 10 min. The operated lung was temporarily ventilated if pulse oximetric saturation (SpO(2)) decreased to < 91%. SpO(2) <9 1% occurred in 2 of the 152 patients. SpO(2) overestimated O(2)Hb by 2.9% +/- 0.1%. NO failed to improve oxygenation or alter occurrence of O(2)Hb < 90% during OLV across all time points and all levels of FIO(2). Increasing FIO(2) increased oxygenation and decreased occurrence of O(2)Hb < 90% (P: < 0.001). At FIO(2) = 1, PaO(2) was higher (P < 0.01) and O(2)Hb < 90% rate tended to be lower (P = 0.1) during right versus left lung ventilation. PaO(2) was higher in patients undergoing pneumonectomy and lobectomy than in those undergoing metastasectomy or video-assisted operations (P < 0.05).

IMPLICATIONS

Inhaled nitric oxide failed to improve oxygenation during one-lung ventilation. Oxygenation during one-lung ventilation was improved with increasing levels of FIO(2) during ventilation of the right versus the left lung and with increasing pathology of the nonventilated lung.

The effects of inhibiting leukocyte migration with fucoidin in a rat peritonitis model

OBJECTIVES

To study the effects of fucoidin on leukocyte rolling and emigration and bacterial colonization in a peritonitis sepsis model in rats.

DESIGN AND INTERVENTIONS

A controlled study in 64 male Wistar rats, anesthetized and rendered septic by cecal ligation and puncture (CLP). Immediately after CLP 32 animals received a continuous infusion of fucoidin and 32 a continuous infusion of Ringer's lactate.

MEASUREMENTS AND MAIN RESULTS

Systemic leukocyte counts were determined every 2 h after CLP. Surviving animals were anesthetized 24 h after CLP, and intravital measurements of leukocyte rolling in venules in the cremaster muscle were performed. The animals were then killed and their organs harvested for histological and microbiological examinations. The 24-h survival was comparable in the two groups. Fucoidin-treated animals had higher leukocyte counts in the systemic circulation and lower counts in the lungs, liver, abdominal cavity, and brain than control animals. The number of bacterial colony forming units in the abdominal cavity, lungs, liver, brain and blood did not differ in the two groups. Fucoidin treatment changed the type of bacteria predominantly found in the examined organs from Escherichia coli to Pseudomonas aeruginosa.

CONCLUSIONS

In an intra-abdominal model of sepsis we found that treatment with fucoidin induces leukocytosis inhibits leukocyte rolling and reduces leukocyte emigration in the abdominal cavity, lungs, and liver. Reduction in the number of emigrating leukocytes was not associated with an increase in bacterial counts found in the examined organs.

Sensitivity and specificity of various markers of inflammation for the prediction of tumor necrosis factor-alpha and interleukin-6 in patients with sepsis

OBJECTIVES

To determine correlations and predictive strength of surrogate markers (body temperature, leukocyte count, C-reactive protein [CRP], and procalcitonin [PCT]) with elevated levels of tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) in septic patients.

DESIGN

Prospective consecutive case series.

SETTING

Surgical intensive care unit (ICU) of a university hospital.

PATIENTS

A total of 175 patients experiencing intensive care unit stays >48 hrs categorized for sepsis according to ACCP/ SCCM Consensus Conference criteria.

MEASUREMENTS AND MAIN RESULTS

CRP and PCT were both significantly correlated with TNF-alpha and IL-6. Based on the area-under-the-curve of the receiver operating characteristics curves, predicting capability was highest for PCT (0.814 for TNF-alpha >40 pg/mL and 0.794 for IL-6 >500 pg/mL), moderate with CRP (0.732 and 0.716, respectively), and lowest for leukocyte count (0.493 and 0.483, respectively) and body temperature (0.587 and 0.589, respectively). Sensitivity, specificity, positive, and negative predictive values and test effectiveness all followed this same pattern of being highest for PCT followed by CRP, with leukocyte count and body temperature being lowest.

CONCLUSION

PCT may be an early and better marker of elevated cytokines than the more classic criteria of inflammation.

The effects of increasing concentrations of desflurane on systemic oxygenation during one-lung ventilation in pigs

During one-lung ventilation (OLV), hypoxic pulmonary vasoconstriction reduces venous admixture and attenuates the decrease in arterial O2 tension by diverting blood from the nonventilated to the ventilated lung. In vitro, increasing concentrations of desflurane depresses hypoxic pulmonary vasoconstriction in a dose-dependent manner. Accordingly, we investigated the effects of increasing concentrations of desflurane on oxygenation during OLV in vivo. Thirteen pigs (25-30 kg) were anesthetized (induction: propofol 2-3 mg/kg IV; maintenance: N2O/O2 50%/50%, desflurane 3%, propofol 50 microg x kg(-1) min(-1), and vecuronium 0.2 mg x kg(-1) x h(-1) IV), orotracheally intubated, and mechanically ventilated. After placement of femoral arterial and thermodilution pulmonary artery catheters, a leftsided, 28F, double-lumen tube was placed via tracheotomy. After double-lumen tube placement, N2O and desflurane were discontinued, propofol was increased to 200 microg x kg(-1) x min(-1), and the fraction of inspired oxygen was adjusted at 0.8. Anesthesia was then continued in random order with desflurane 5%, 10%, or 15% end-tidal concentrations while propofol was discontinued. Whereas mixed venous PO2, mean arterial pressure, cardiac output, and shunt fraction decreased in a dose-dependent manner, PaO2 remained unchanged with increasing concentrations of desflurane during OLV. These findings indicate that, in vivo, increasing concentrations of desflurane do not necessarily worsen oxygenation during OLV.

IMPLICATIONS

Oxygenation during one-lung ventilation depends on reflex vasoconstriction in the nonventilated lung. In vitro, desflurane inhibits this reflex dose-dependently. Our results indicate that, in vivo, this does not necessarily translate to dose-dependent decreases in oxygenation during one-lung ventilation.

G-CSF during Escherichia coli versus Staphylococcus aureus pneumonia in rats has fundamentally different and opposite effects

We investigated if bacteria type alters outcome with prophylactic granulocyte colony stimulating factor (G-CSF) therapy during pneumonia. Rats received G-CSF or placebo daily for 6 d and after the third dose were intrabronchially inoculated with either Escherichia coli or Staphylococcus aureus. Without G-CSF, E. coli and S. aureus produced similar (p = NS) mortality rates (36 versus 38%) and serial changes in mean circulating neutrophil counts (CNC), but differing mean (+/- SE) tumor necrosis factor (TNF) levels (E. coli, 259 +/- 104 versus S. aureus, 51 +/- 17 pg/ml, p = 0.01). G-CSF prior to bacteria increased mean CNC more than six times compared with placebo (p = 0.001). However, with G-CSF in the first 6 h after E. coli, there was a greater than 20-fold decrease in mean (+/- SE) CNC (x 10(3)/ mm3) to below placebo (0.5 +/- 0.1 versus 0.8 +/- 0.1), whereas with G-CSF after S. aureus, there was only a fivefold decrease in mean CNC and CNC were greater than placebo (1.8 +/- 0.2 versus 0.8 +/- 0.1) (E. coli versus S. aureus decrease in CNC with G-CSF, p = 0.001). With E. coli, G-CSF worsened oxygenation and increased bacteremia and mortality, whereas with S. aureus, G-CSF improved oxygenation and decreased bacteremia and mortality (G-CSF therapy, E. coli versus S. aureus, p = 0.03, 0.05, and 0.001, respectively). Thus, during S. aureus pneumonia with low TNF levels, G-CSF increased CNC and bacterial clearance, resulting in less pulmonary injury and decreased death. During E. coli pneumonia with high TNF levels, G-CSF paradoxically decreased CNC, resulting in impaired bacterial clearance and worsened pulmonary injury and death. Bacterial species and the associated inflammatory mediator response can alter outcome with prophylactic G-CSF therapy during pneumonia.

Changes in pulmonary mechanics after fiberoptic bronchoalveolar lavage in mechanically ventilated patients

OBJECTIVE

We prospectively assessed the impact of bronchoalveolar lavage (BAL) on respiratory mechanics in critically ill, mechanically ventilated patients.

STUDY DESIGN

Mechanically ventilated patients underwent BAL of one lung segment using 5 x 20 ml of sterile, physiologic saline with a temperature of 25-28 degrees C. The fractional inspired oxygen was increased to 1.0, but ventilator settings were otherwise left unchanged. Static pulmonary compliance, pulmonary resistance, alveolar ventilation, and serial dead space were measured 60 min and 2 min before and 8, 60, and 180 min after BAL to assess the consequences of the procedure. In addition, blood gases [partial pressure of carbon dioxide in arterial blood (PaCO2) and arterial oxygen tension (PaO2)], hemodynamic variables (heart rate, systolic and diastolic blood pressure), and body temperature were recorded at the same time points.

SETTING

Intensive care unit of a university hospital.

PATIENTS

18 consecutive critically ill, mechanically ventilated patients.

RESULTS

Pulmonary compliance decreased by 23% (p < 0.05) and pulmonary resistance increased by 22% (p < 0.05) shortly after BAL. The changes in pulmonary compliance and resistance were more than 30% in one third of the patient population. One hour after the procedure, PaO2 was significantly lower and PaCO2 significantly higher than before the procedure. Three hours after the procedure, pulmonary resistance returned to pre-BAL values but compliance remained 10% below baseline values (p < 0.05).

CONCLUSION

BAL in mechanically ventilated patients is associated with deterioration of pulmonary mechanics and function.

Effect of plasma and LPS on respiratory burst of neutrophils in septic patients

OBJECTIVE

To compare the respiratory burst of neutrophils in sepsis and control patients using lipopolysaccharide (LPS), autologous plasma, and a combination of the two.

DESIGN

Prospective, consecutive case study.

SETTING

A 16-bed intensive care unit (ICU) in a university teaching hospital.

INTERVENTIONS

None.

PATIENTS

Plasma was obtained from 23 healthy patients scheduled for minor surgery immediately prior to induction of anesthesia (controls) and from 23 ICU patients within 24 h of diagnosis of sepsis or septic shock.

MEASUREMENTS AND MAIN RESULTS

Respiratory burst was determined by lucigenin chemiluminescence expressed as mean +/- SEM of peak values of relative light units per neutrophil. There were no significant differences between neutrophils of septic patients and controls for the stimuli saline, phorbol myristate acetate, formyl-methionyl-leucyl-phenylalanine, and LPS alone. Septic patients showed a lower respiratory burst than controls (p < 0.05) under the following stimuli: plasma alone (5911 +/- 803 vs 15,397 +/- 3038) and LPS and plasma combined (13,857 +/- 1537 vs 23,026 +/- 2640). However, when stimulated with plasma after priming with LPS, septic patients elicited a higher value than control subjects (11,373 +/- 1758 vs 5987 +/- 1234, p < 0.05).

CONCLUSIONS

(1) Some components of the plasma of septic patients may have a profound effect on neutrophil response; (2) plasma as a respiratory burst stimulus differentiates between sepsis and non-sepsis samples better than other common stimuli; (3) precautions must be taken when using plasma together with LPS because of the different response depending on whether LPS-priming precedes the plasma stimulus or both are introduced simultaneously and whether septic or nonseptic plasma is used.

Oxygen consumption in hemodialysis patients undergoing cardiopulmonary bypass

OBJECTIVES

Cardiopulmonary bypass (CPB) can be successfully performed in patients on hemodialysis. However, ischemic complications occur more often in these patients. This could partly be because of shunting through the arteriovenous (AV) fistula during CPB, resulting in reduced peripheral flow and oxygen (O2) delivery. Inadequate oxygen delivery during CPB should be reflected in a lower oxygen consumption (VO2) compared with patients without an AV fistula.

DESIGN

To test the hypothesis, the authors analyzed VO2 in three groups of patients retrospectively. Group 1 included 14 patients with end-stage renal failure (creatinine level 9.1 +/- 0.3 mg/dL, urea level 126 +/- 8 mg/dL) requiring hemodialysis through an AV fistula. Group 2 included 13 patients with compensated renal insufficiency (creatinine level 3.1 +/- 0.4 mg/dL, urea level 106 +/- 10 mg/dL) without an AV fistula. Group 3 included 14 patients with normal renal function (creatinine level 1.0 +/- 0.1 mg/dL, urea level 44 +/- 4 mg/dL).

SETTING

An operating room of a university hospital.

PARTICIPANTS

Patients undergoing cardiac surgery requiring CPB.

MEASUREMENTS AND MAIN RESULTS

VO2 was calculated from the recorded hemodynamic and blood gas data using standard formulae. Data were analyzed using a two-way analysis of variance with a repeated measurement on one factor. Before undergoing CPB, VO2 was similar in all three groups. VO2 decreased in all three groups during hypothermic CPB (standard flow rate 2.2 L/min/m2, standard temperature 29 degrees C) and returned to prebypass levels during rewarming. There was no difference in VO2 among the three groups during hypothermic CPB or during rewarming. Only base excess decreased more in group 1 patients compared with the other groups (p < 0.001).

CONCLUSION

During hypothermic CPB at a flow rate of 2.2 L/min/m2, shunting through an AV fistula is unlikely to lead to decreased VO2 in dialysis patients.

Effects of desflurane and propofol on arterial oxygenation during one-lung ventilation in the pig

BACKGROUND

Desflurane depresses hypoxic pulmonary vasoconstriction (HPV) in vitro. During one-lung ventilation (OLV), HPV may reduce venous admixture and ameliorate the decrease in arterial O2 tension by diverting blood from the non-ventilated to the ventilated lung. Accordingly, this study compares the effects of desflurane with those of propofol on oxygenation during two-lung (TLV) and OLV in vivo.

METHODS

Ten pigs (25-30 kg) were premedicated (flunitrazepam 0.4 mg/kg i.m.), anaesthetized (induction: propofol 2 mg/kg i.v.; maintenance: N2O/O2 50%/50%, desflurane 3%, propofol 50 micrograms kg-1 min-1, and vecuronium 0.2 mg kg-1 h-1 i.v.), orally intubated and mechanically ventilated. Femoral arterial and thermodilution pulmonary artery catheters were placed, and the orotracheal tube was replaced by a left-sided 28-Ch double-lumen tube (DLT) via tracheotomy. After DLT placement, N2O and propofol were discontinued, FiO2 was increased to 0.85, and anaesthesia continued randomly with either desflurane (1 MAC) or propofol 200 micrograms kg-1 min-1. Using a cross-over design, in each animal the effects of a), changing from TLV to OLV (left lung) during both desflurane and propofol and b), the effects of changing between the two anaesthetics during OLV were studied.

RESULTS

When changing from TLV to OLV, PaO2 decreased more (p < 0.05) during desflurane (mean 75%) than during propofol (mean 60%). Changing between desflurane and propofol during OLV resulted in small but consistent (P < 0.05) increases in PaO2 (mean 15%) during propofol.

CONCLUSION

Consistent with in vitro results on HPV, 1 MAC desflurane impaired in vivo oxygenation during OLV more than did propofol.

[Procalcitonin. A new diagnostic parameter for severe infections and sepsis]

Procalcitonin (PCT), a glycoprotein consisting of 116 amino acids, has been proposed as a new marker of severe infection. The site of production under this condition remains unknown. The serum PCT concentration is determined by an immunoluminometric assay of 40 microliters serum or plasma requiring approximately two hours. Elevations of PCT are for instance associated with levels of lipopolysaccharide and the cytokines TNF-alpha and IL-6. Bacterial, parasitic or fungal infections developing septic complications in contrast to local infections, often show values exceeding 2 ng/ml. The specificity of the parameter in this context increases with its concentrations. Therapeutic actions that confine the infection locally are reflected by a decrease of the PCT value. PCT may be elevated within the first days after extended surgery or polytrauma, in some malignancies, heat-stroke and during treatment of some hematologic diseases without an existing sepsis or severe infection. Previous studies indicate certain benefits of PCT compared to traditional markers of inflammation or sepsis, where the ability to indicate a generalized infection is the primary advantage.

Sepsis: definitions and diagnosis

There have been many attempts to provide a uniform definition for the diagnosis of sepsis that can be used for research and clinical purposes. Several definitions are too broad and, as a result, clinicians are unable to direct appropriate therapies to patients. Disappointing immunomodulatory trials have led many researchers to the conclusion that the current diagnostic criteria of sepsis fails to identify patients who could benefit from immunomodulatory therapies. In order to restore clinical and experimental relevance, many researchers and clinicians believe that sepsis should be defined as an inflammatory response to infection with signs of remote organ dysfunction. However, because common clinical signs of systemic inflammation are neither specific nor sensitive for sepsis, other markers may be helpful. Markers of the systemic inflammatory response to infection could include cytokines such as tumour necrosis factor alpha, interleukin 1, 6 and 8 and the propeptide procalcitonin. As well as identifying patients who may benefit from pro- or anti-inflammatory therapies, these markers may gauge the extent of the inflammatory response and could be used for monitoring the immune status of the patient.

Effects of L-NMMA and fluid loading on TNF-induced cardiovascular dysfunction in dogs

We investigated the effects of N(omega)-monomethyl-L-arginine (L-NMMA) and fluid loading on tumor necrosis factor (TNF)-induced cardiovascular dysfunction in awake dogs. L-NMMA (40 mg x kg(-1) given intravenously over a period of 10 min, and followed by dosing at 40 mg x kg(-1) x h(-1) for 6 h) and TNF (20 or 45 microg x kg(-1) given intravenously for 20 min), given alone or in combination, significantly decreased stroke volume, cardiac index, oxygen delivery, and left-ventricular (LV) function plots over a period of 6 h. Of note was that the cardiac-depressant effects of TNF and L-NMMA given together were significantly less than additive. Thus, the combination was beneficial (or significantly less harmful to cardiac performance than expected), possibly because L-NMMA augmented cardiac preload as shown by significant increases in both pulmonary capillary wedge pressure (PCWP) and central venous pressure (CVP). Fluid challenges at 6 h (Ringer's solution at 80 ml x kg(-1) given over a period of 30 min) also significantly increased PCWP and CVP, and abolished the beneficial preload effect of L-NMMA on cardiac performance. Thus, after fluid loading, the cardiac-depressant effects of TNF and L-NMMA given together became equal to the sum of those produced by TNF and L-NMMA given separately. Although L-NMMA significantly decreased serum nitrite/nitrate levels, TNF did not increase these end products of nitric oxide (NO) production relative to controls. Therefore, after preload abnormalities were eliminated with fluid loading, L-NMMA had no beneficial effect on TNF-induced cardiac depression, and TNF did not increase end products of NO production. These findings are not consistent with NO being the mechanism of TNF-induced acute cardiac depression.

Total plasma antioxidant capacity is not always decreased in sepsis

OBJECTIVE

To compare total plasma antioxidant capacity and selected individual antioxidants in patients with varying degrees of severity of sepsis.

DESIGN

A prospective, observational, consecutive case study.

SETTING

A 16-bed intensive care unit (ICU) in a university teaching hospital.

INTERVENTIONS

None.

PATIENTS

Forty-six healthy controls, ten ICU patients, nine patients with systemic inflammatory response syndrome (SIRS), 11 septic patients, and 14 septic shock patients. Plasma was obtained in healthy patients scheduled for minor surgery immediately before anesthesia and in ICU patients within 24 hrs of admittance to the unit or diagnosis of SIRS, sepsis, or septic shock.

MEASUREMENTS AND MAIN RESULTS

Using the total peroxyl radical trapping method, we found plasma antioxidant capacity to be lower in septic patients but higher in septic shock patients, as compared with controls. Bilirubin was the greatest contributor to the increase with shock, followed by uric acid. Neopterin also correlated with the peroxyl radical trapping antioxidant parameter values.

CONCLUSION

Although total plasma antioxidant capacity is decreased from normal levels in septic patients, an increase in some oxidants contributes to an increased total antioxidant capacity in septic shock patients.

Role of fiberoptic bronchoscopy in conjunction with the use of double-lumen tubes for thoracic anesthesia: a prospective study

BACKGROUND

Fiberoptic bronchoscopy has been recommended to verify the position of double-lumen tubes (DLT), but this remains controversial. The authors studied the role of bronchoscopy for placing and monitoring right- and left-sided DLTs after blind intubation and after positioning the patient.

METHODS

Two hundred patients having thoracic surgery requiring DLT insertion were prospectively studied. "Blind" tracheal intubations were done with 163 left-sided and 37 right-sided disposable polyvinyl chloride Robertshaw tubes. Bronchoscopy was performed by a different anesthesiologist after intubation and conventional clinical verification of correct placement and after patient positioning for thoracotomy. A DLT was considered malpositioned when it had to be moved >0.5 cm to correct its position. Critical malpositions were those that might have affected patient safety or influenced the surgical procedure if left uncorrected.

RESULTS

After "blind" DLT intubation, clinical evidence of malpositioning was found in 28 patients. This was confirmed by fiberoptic assessment. In 172 patients in whom placement was judged correct by clinical assessment, malpositioning was detected by bronchoscopy in 79 cases, 25 of which were critical. After patient positioning, DLTs were found to be displaced in 93 patients, 48 of which were critical. Right-sided DLTs were significantly more likely to be malpositioned than were left-sided DLTs. Two complications were related to unsatisfactory lung separation in the 200 patients studied.

CONCLUSIONS

After blind intubation and patient positioning, more than one third of DLTs required repositioning. Routine bronchoscopy is therefore recommended after intubation and after patient positioning.

Cardiopulmonary effects of inhaled nitric oxide in normal dogs and during E. coli pneumonia and sepsis

We investigated the effect of inhaled nitric oxide (NO) at increasing fractional inspired O2 concentrations (FIO2) on hemodynamic and pulmonary function during Escherichia coli pneumonia. Thirty-eight conscious, spontaneously breathing, tracheotomized 2-yr-old beagles had intrabronchial inoculation with either 0.75 or 1.5 x 10(10) colony-forming units/kg of E. coli 0111:B4 (infected) or 0.9% saline (noninfected) in one or four pulmonary lobes. We found that neither the severity nor distribution (lobar vs. diffuse) of bacterial pneumonia altered the effects of NO. However, in infected animals, with increasing FIO2 (0.08, 0.21, 0.50, and 0.85), NO (80 parts/million) progressively increased arterial PO2 [-0.3 +/- 0.6, 3 +/- 1, 13 +/- 4, 10 +/- 9 (mean +/- SE) Torr, respectively] and decreased the mean arterial-alveolar O2 gradient (0.5 +/- 0.3, 4 +/- 2, -8 +/- 7, -10 +/- 9 Torr, respectively). In contrast, in noninfected animals, the effect of NO was significantly different and opposite; NO progressively decreased mean PO2 with increasing FIO2 (2 +/- 1, -5 +/- 3, -2 +/- 3, and -12 +/- 5 Torr, respectively; P < 0.05 compared with infected animals) and increased mean arterial-alveolar O2 gradient (0.3 +/- 0.04, 2 +/- 2, 1 +/- 3, 11 +/- 5 Torr; P < 0.05 compared with infected animals). In normal and infected animals alike, only at FIO2 < or = 0.21 did NO significantly lower mean pulmonary artery pressure, pulmonary artery occlusion pressure, and pulmonary vascular resistance index (all P < 0.01). However, inhaled NO had no significant effect on increases in mean pulmonary artery pressure associated with bacterial pneumonia. Thus, during bacterial pneumonia, inhaled NO had only modest effects on oxygenation dependent on high FIO2 and did not affect sepsis-induced pulmonary hypertension. These data do not support a role for inhaled NO in bacterial pneumonia. Further studies are necessary to determine whether, in combination with ventilatory support, NO may have more pronounced effects.

Rapid increase in inspired desflurane concentration does not elicit a hyperdynamic circulatory response in the pig

The effects of a rapid increase in inspired desflurane concentration on systemic haemodynamics and plasma catecholamines were studied in seven pigs (22-30 kg). Following premedication (flunitrazepam 0.4 mg/kg i.m.), anaesthesia was induced (propofol 2.5 mg/kg i.v., vecuronium 0.2 mg/kg i.v.), the trachea orally intubated, and ventilation controlled. Anaesthesia was maintained with N2O/O2 (70%/30%), propofol (50 micrograms/kg/min), desflurane (2% end-tidal concentration), and vecuronium (0.3 mg/kg/h). After cannulation of both femoral arteries for subsequent simultaneous systemic pressure measurements and blood sampling for determination of epinephrine (E) and norepinephrine (NE) plasma levels, N2O and propofol were discontinued, and FiO2 and end-tidal concentration of desflurane increased to > 0.9 and 3%, respectively. Forty minutes later, the inspired concentration of desflurane was abruptly increased to 15%. Mean arterial pressure (MAP), heart rate (HR), and plasma concentrations of E and NE were determined before and 1, 2, 4, 8, 16, and 32 min after increasing the desflurane concentration. Plasma concentrations of E and NE were determined by high performance liquid chromatography (HPLC) with electrochemical detection. Data were analysed by repeated measures ANOVA (significance level P < 0.05). The abrupt increase in inspired desflurane concentration caused an insignificant increase (11%) in HR at 1, 2 and 4 min. There was an immediate decrease in MAP. Plasma levels of E and NE remained unchanged throughout. In conclusion, in contrast to findings in humans, a rapid increase in inspired desflurane concentration does not cause a hyperdynamic circulatory response in the pig.

A controlled study of leukocyte activation in septic patients

OBJECTIVE

Qualitative and quantitative evaluation of leukocyte activation in septic patients in comparison to two control groups.

DESIGN

A prospective clinical study in which the leukocyte oxidative output of whole blood was measured in three groups of patients. Two chemiluminescence markers (luminol or lucigenin), indicative of either total oxidant output or superoxide production, and three stimuli (opsonized zymosan, formyl-methionyl-leucyl-phenylalanine (fMLP), phorbol myristate acetate) (PMA), representing different pathways of leukocyte activation, were used. Tumor necrosis factor, interleukin-6 and C-reactive protein (TNF, IL-6, and CRP) were determined to evaluate the severity of the inflammatory process.

SETTING

Intensive care and surgical units of a university hospital.

PATIENTS

Seventy-four healthy patients, ten ICU patients without signs of sepsis or systemic inflammatory response syndrome and 19 septic patients were studied.

MEASUREMENT AND MAIN RESULTS

With all three stimuli, whole blood total oxidative output and superoxide production were generally increased in septic patients. This was most likely due to the increased leukocyte numbers in these patients. When the chemiluminescence values were normalized per phagocyte (granulocytes and monocytes), the total oxidative output of septic phagocytes decreased with opsonin and fMLP but increased with PMA, while superoxide output decreased regardless of the stimuli used. TNF, IL-6 and CRP, although increased in septic patients as compared to ICU controls, correlated weakly with oxidant output.

CONCLUSIONS

The oxidative output of whole blood was increased in septic patients compared to controls because of elevated leukocyte numbers. However, oxidant output normalized for phagocyte numbers generally decreases during sepsis for most stimuli. Cytokines and CRP do not appear to be associated with the extent of oxidant output during sepsis.

Immune modulation and sepsis

The pathogenesis of sepsis involves not only microbial toxins but also activated host inflammatory mediators. Therefore, besides conventional antibiotic or surgical treatment of infection and supportive intensive therapy, modulating host inflammatory mediators as a conjunctive therapeutic option has been explored in the past decade. Although successful in animal models of sepsis, inhibiting host inflammatory response in human sepsis has failed to improve survival or otherwise show efficacy. Studies are needed which better describe the circumstances under which these therapies may ultimately prove successful.

Effects of dopamine on oxygen consumption and gastric mucosal blood flow during cardiopulmonary bypass in humans

We investigated the effects of flow rate and dopamine on systemic oxygen delivery (DO2) oxygen consumption (VO2) and gastric mucosal microcirculatory blood flow (gMCF), measured by laser Doppler flowmetry in 12 patients undergoing mild hypothermic (34 degrees C) cardiopulmonary bypass (CPB). The first intervention comprised increasing CPB flow rates from 2.4 to 3.0 litre min-1 m-2, and the second intervention administering dopamine 6 micrograms kg-1 min-1. Measurements were made before and 10 min after the start of one of the two interventions. The heart remained in cardioplegic arrest throughout the study. There were no significant differences in variables between the two baseline measurements preceding the interventions. The increase in CPB flow rate increased DO2 and gMCF without affecting VO2. At constant flow rate, dopamine also increased gMCF with no change in VO2, DO2 or mean arterial pressure. Our data suggested that dopamine had no flow-independent effect on VO2 and that it increased gMCF during constant flow hypothermic CPB.

Controlled trials of rG-CSF and CD11b-directed MAb during hyperoxia and E. coli pneumonia in rats

We studied the effects of inhibiting and augmenting neutrophil function by using an immunocompetent rat model of infectious and hyperoxic lung injury. After intrabronchial Escherichia coli challenge at all fractional inspired O2 (FIO2) values studied (FIO2 = 0.21, 0.60, and 0.95) and after lethal O2 exposure alone (FIO2 = 0.90), lung injury, as measured by histological and physiological changes, was reduced by a CD11b/CD18-directed monoclonal antibody (MAb 1B6, P < 0.05 vs. controls) but was increased by recombinant granulocyte colony-stimulating factor (rG-CSF; P < 0.05 vs. control; MAb 1B6 vs. rG-CSF, P < 0.004). Pulmonary neutrophil counts were reduced by MAb 1B6 (P < 0.04) and increased by rG-CSF (P < 0.0004) compared with control animals. However, despite antibiotics, MAb 1B6 and rG-CSF both significantly increased the relative risk of death, independent of O2 concentration, during E. coli pneumonia (1.74 [symbol: see text] 1.20 and 2.39 [symbol: see text] 1.19, respectively, each P < 0.01). During lethal hyperoxia, MAb 1B6 increased the relative risk of death (1.76 [symbol: see text] 1.28, P < 0.16), whereas rG-CSF had no effect on survival (0.97 [symbol: see text] 1.28, P = 0.89). Thus inhibition of neutrophil function attenuated and enhancement worsened lung injury in response to infectious and hyperoxic challenges, supporting a pathophysiological role of the neutrophil in these processes. However, it is problematic that MAb 1B6 therapy, despite preventing lung damage, ultimately worsened host defenses and survival. Furthermore, rG-CSF also adversely affected survival during infectious lung injury, demonstrating the inherent risks of inhibiting or augmenting neutrophil function in an immunocompetent host during infection.

Dobutamine increases oxygen consumption during constant flow cardiopulmonary bypass

We have studied the effects of flow and dobutamine on systemic haemodynamic variables, oxygen delivery (DO2) and oxygen consumption (VO2) in 20 patients during cardiopulmonary bypass (CPB) with mild hypothermia (34 degrees C). In a subgroup of seven patients, we also studied the effects on gastric microcirculatory blood flow (MCF) using laser Doppler flowmetry. During CPB, measurements were made before and after two interventions: the first consisted of increasing flow from 2.4 to 3.0 litre min-1 m-2 for 10 min; the second consisted of an infusion of dobutamine at a rate of 6 micrograms kg-1 min-1 for 10 min during constant flow CPB. There were no significant differences in DO2, VO2 or haemodynamic variables between the two baseline measurements. The increase in flow raised DO2 (27%, P < 0.001), mean arterial pressure (P < 0.01) and MCF (P < 0.01), but failed to increase VO2. In contrast, dobutamine infusion increased VO2 (11%, P < 0.001) during constant flow CPB without significant changes in DO2, systemic haemodynamic variables or MCF. These results indicate that increases in VO2 during dobutamine may be flow-independent.

Hemodynamic effects of dopamine, norepinephrine, and fluids in a dog model of sepsis

To study how sepsis affects hemodynamic responses to catecholamines and fluids, either Escherichia coli-infected (septic, n = 8) or sterile (controls, n = 6) fibrin clots were implanted intraperitoneally into 2-yr-old beagles. Hemodynamics were measured at each of four doses of dopamine (0, 5, 10, and 20 micrograms.kg-1.min-1) and norepinephrine (0, 10, 20, and 40 micrograms.min-1), before and after infusion of fluid (Ringer 40 ml.kg-1). Septic animals had lower mean arterial pressure (MAP, P = 0.04), stroke volume index (SVI, P = 0.0001), and left ventricular (LV) ejection fraction (LVEF) (P = 0.0001) than controls. During this time, increasing doses of dopamine and norepinephrine produced corresponding increases (P < 0.001) in LVEF, SVI, and MAP. However, during sepsis, the ability of dopamine to increase MAP diminished, while its ability to increase LVEF and SVI was maintained. Conversely, the ability of norepinephrine to increase LVEF and SVI diminished, but its ability to increase MAP was maintained. During sepsis, fluids alone increased (P < 0.05) MAP, LVEF, SVI, and cardiac index (CI). Fluids with catecholamines also significantly increased (P < 0.05) MAP with only minimal increases in LVEF, SVI, and CI. These data demonstrate that during sepsis without catecholamines, fluids improve cardiac performance and systemic pressures, but with catecholamines, fluids have minimal effects on cardiac performance and augment MAP. Furthermore, during sepsis dopamine is more effective than norepinephrine in increasing LV performance, but norepinephrine is more effective than dopamine in increasing systemic pressures.

The effects of beta-adrenoreceptor blockade on oxygen consumption during cardiopulmonary bypass

The effect of chronic beta-adrenoreceptor blockade (beta-blockade) on hemodynamics and oxygen consumption (VO2) during cardiopulmonary bypass (CPB) in mild hypothermia (34 degrees C) was studied in 34 patients. The study group included 17 patients who received beta-adrenergic blocking drugs for at least 1 mo prior to the study. Seventeen patients who did not receive beta-adrenergic blockers served as controls. Demographic data in the two groups were comparable. Prior to induction of anesthesia, the heart rate was slower in the beta-adrenergic blocker group as compared to the control group. During CPB, measurements were made at two pump flow rates: 2.4 L.min-1.m-2 and 3.0 L.min-1.m-2. Oxygen delivery was similar in the two groups (beta-adrenergic blocker vs control) but the oxygen consumption was significantly lower in the beta-adrenergic blocker group as compared to the control group at both flow rates (P = 0.009). Increasing the flow rate from 2.4 L.min-1.m-2 to 3.0 L.min-1.m-2 produced a similar increase (P = 0.0001) in oxygen consumption in both groups. Increasing flow rate increased mean arterial pressure (MAP) and central venous pressure (CVP) and decreased systemic vascular resistance index (SVRI) and reservoir volume similarly in both groups. Thus, compared to the control group, patients on chronic beta-adrenergic blocker medication have a lower VO2 during CPB.

[The concentration of atrial natriuretic peptides (ANP). ANP in different sections of the circulation during atrial volume load with and without anesthesia]

We studied the effect of a volume load induced by a 45 degrees Trendelenburg position on atrial natriuretic peptide (ANP) secretion in awake and anaesthetized patients with coronary artery disease undergoing aortocoronary bypass surgery. ANP was measured in different parts of the circulation before and after induction of high dose fentanyl anaesthesia at fixed times prior to and after extracorporeal circulation. METHOD. In eight patients with coronary artery disease (NYHA classification II-III), who received neither diuretic nor positive inotropic therapy, ANP was measured in the various parts of the circulation: in a peripheral vein, a radial artery, in the pulmonary artery and in the coronary sinus. The measurements were made in the supine and 45 degrees Trendelenburg position. Measurements of mean arterial pressure (MAP), central venous pressure (RAP), pulmonary arterial pressure (PAP), pulmonary capillary wedge pressure (PCWP), cardiac index (CI) and heart rate (HR) were taken simultaneously. The measurements were taken in the awake patient, during steady-state high-dose fentanyl anaesthesia with 50% O2 in N2O and after extracorporeal circulation. RESULTS. Compared to measurements in a control group, ANP levels were significantly higher in all parts of the circulation in patients with coronary artery disease, although clinical symptoms of heart failure were absent. After extracorporeal circulation, significantly higher levels of ANP were found at all measurement sites; however the concentration gradient of ANP between coronary sinus and arterial or venous blood was reduced. In awake and anaesthetized patients a change in body position, causing a significant increase in filling pressures, did not produce an increase in ANP levels at all measurement sites. The induction of high-dose fentanyl anaesthesia did not have an influence on plasmatic ANP levels. CONCLUSION. The results of this study lead to the following conclusions: 1. ANP levels in patients with CAD are increased, even if clinical heart failure symptoms are absent. 2. ANP is secreted in the coronary vessels. Following dilution in the atrial blood, it is metabolized to inactive compounds in the periphery. 3. Basic ANP levels are not changed by high-dose fentanyl anaesthesia. Marked increases of the filling pressures do not correlate with atrial ANP levels either before or after induction of anaesthesia. 4. After extracorporeal circulation ANP levels are significantly increased in all parts of the circulation. The concentration gradient between coronary sinus blood, on the one hand, and arterial and venous blood on the other hand is reduced. This phenomenon is probably caused by an alteration in the metabolism of ANP during hypothermic extracorporeal circulation.