Comparison of gastric intramucosal pH with measures of oxygen transport and consumption in critically ill patients

Hemodynamic and Intestinal Microcirculatory Changes in a Phenylephrine Corrected Porcine Model of Hemorrhage

BACKGROUND

Intraoperative hypotension is a common event, and a recent study suggests that maintenance of blood pressure may reduce complications. The splanchnic circulation provides a reservoir of blood that can be mobilized during hemorrhage; hence, intestinal microcirculation is sensitive to volume changes. The aim of this study was to assess the impact of hemorrhage on intestinal microcirculation and hemodynamics, and the effects of phenylephrine on these parameters.

METHODS

Eight anesthetized, mechanically ventilated Yorkshire/Landrace crossbreed pigs were studied. Graded hemorrhage was performed with the removal of 20% of blood volume in 5% increments. Hemodynamic and intestinal microcirculatory measurements were performed at each stage with side-stream dark field microscopy, following which mean arterial pressure (MAP) was corrected with phenylephrine to baseline values and measurements repeated. A repeated measurement 1-way analysis of variance (ANOVA) was used to compared changes from baseline measurements.

RESULTS

The mean baseline microcirculation score was 42 (standard deviation [SD] = 5). A 5% hemorrhage decreased the microcirculation score by a mean difference of 19 (95% confidence interval [CI], 12-27; P < .0001), and an additional 5% hemorrhage further reduced the microcirculation score by a mean difference of 12 (95% CI, 4-19; P = .0001). Subsequent hemorrhage or administration of phenylephrine did not significantly change the microcirculation scores except when phenylephrine was administered at the 15% hemorrhage stage, which increased the microcirculation score by a mean difference of 7 (95% CI, 1-13; P = .003). All hemodynamic variables were returned to baseline values following hemorrhage by the phenylephrine infusion.

CONCLUSIONS

Intestinal microcirculatory flow is reduced early in hemorrhage and is uncorrected by phenylephrine infusion. Hemodynamic changes associated with hemorrhage are corrected by phenylephrine and do not reflect microcirculatory flow status.

Intraoperative systemic vascular resistance is associated with postoperative nausea and vomiting after laparoscopic hysterectomy

BACKGROUND

The incidence of postoperative nausea and vomiting (PONV) in patients undergoing laparoscopic hysterectomy is very high compared with other surgeries, even when many prophylactic measures have been taken. However, the pathogenesis of PONV is multifactorial. Female sex, a history of motion sickness or PONV, nonsmokers, and perioperative opioid use are the most closely related factors. Among the multiple risk factors, suboptimal gastrointestinal (GI) perfusion may be attributed to some cases of PONV, and increased systemic vascular resistance (SVR) may lead to GI ischemia. The hypothesis of this research was that SVR is related to PONV.

AIM

To investigate the relationship between SVR and PONV in patients undergoing laparoscopic hysterectomy.

METHODS

A total of 228 patients who underwent elective laparoscopic hysterectomy were included in this prospective observational study. SVR was monitored using a noninvasive hemodynamic monitoring system. Four indices of SVR, the baseline, mean, area under the curve (AUC), and weighted AUC, were used for analysis. The incidence and severity of nausea and vomiting were evaluated while patients were awake and throughout the intervals from 0 to 2 h, 2 to 6 h, and 6 to 24 h starting upon arrival at the post-anesthesia care unit. The associations between various SVR indices and PONV were investigated by logistic regression. P < 0.05 was considered statistically significant.

RESULTS

The incidence of PONV in the study was 56.14% (128/228), and PONV tended to appear within 6 h after surgery. Five variables were significant in univariate analyses, however, only SVR mean [odds ratio (OR) = 1.015, 95%CI: 1.005-1.109, P = 0.047] and duration of surgery (OR = 1.316, 95%CI: 1.003-2.030, P = 0.012) were associated with PONV after logistic regression analysis. Furthermore, patients with high SVR mean were more likely to suffer from PONV after laparoscopic hysterectomy. On average, patients who developed PONV needed more time to tolerate diet and demonstrated poorer sleep quality on the first night after surgery.

CONCLUSION

In this study, PONV was a common complication after laparoscopic hysterectomy. SVR was associated with PONV, and high SVR mean was associated with a significantly increased risk of PONV.

Gastrointestinal ischemia monitoring through impedance spectroscopy as a tool for the management of the critically ill

Impedance spectroscopy (IS) has been proposed as a tool for monitoring mucosal tissue ischemia and damage in the gut of critically ill patients resulting from shock and hypoperfusion. A specific device and system have been developed and tested for this specific application over the past 12 years by our research group. This paper reviews previously published studies as well as unpublished experimental results, and puts the whole in context and perspective to help understand this technology. Results presented include summaries of gastric reactance measurement understanding, in vivo measurements in animal models, clinical significance of the measurement, and future perspectives of clinical use of this technology. All of the experimental work done to date has been designed to determine the evolving device prototypes' performance and limitations from an instrumentation point of view. Although there are still questions to be answered with regard to the IS measurement, we conclude that we have reached enough confidence in the measurement and the device's performance and safety to begin clinically oriented research to learn how this technology may be useful in the diagnosis and management of different populations of the critically ill.

Gastric tissue damage analysis generated by ischemia: bioimpedance, confocal endomicroscopy, and light microscopy

The gastric mucosa ischemic tissular damage plays an important role in critical care patients' outcome, because it is the first damaged tissue by compensatory mechanism during shock. The aim of the study is to relate bioimpedance changes with tissular damage level generated by ischemia by means of confocal endomicroscopy and light microscopy. Bioimpedance of the gastric mucosa and confocal images were obtained from Wistar male rats during basal and ischemia conditions. They were anesthetized, and stain was applied (fluorescein and/or acriflavine). The impedance spectroscopy catheter was inserted and then confocal endomicroscopy probe. After basal measurements and biopsy, hepatic and gastric arteries clamping induced ischemia. Finally, pyloric antrum tissue was preserved in buffered formaldehyde (10%) for histology processing using light microscopy. Confocal images were equalized, binarized, and boundary defined, and infiltrations were quantified. Impedance and infiltrations increased with ischemia showing significant changes between basal and ischemia conditions (P < 0.01). Light microscopy analysis allows detection of general alterations in cellular and tissular integrity, confirming gastric reactance and confocal images quantification increments obtained during ischemia.

The predictive value of gastric reactance for postoperative morbidity and mortality in cardiac surgery patients

No useful method to directly monitor the level of end organ tissue injury is currently available clinically. Gastric reactance has been proposed to measure changes in a tissue structure caused by ischemia. The purpose of this study was to assess whether gastric reactance is a reliable, clinically relevant predictor of complications and a potentially useful tool to assess hypoperfusion in cardiovascular surgery patients. The value of gastric reactance measurements, standard hemodynamic and regional perfusion variables, and scores to predict postoperative complications were compared in 55 higher risk cardiovascular surgery patients with cardiopulmonary bypass. Low frequency gastric reactance, X(L), had a significant predictive value of postoperative persistent shock requiring more than 48 h of vasopressors and associated complications, before, during and after surgery (p < 0.05). Results suggest that reactance is an earlier predictor of patients at risk than all other variables tested. Patients with a high reactance (X(L) > 26) before surgery had a significantly higher incidence of complications, higher mortality and more days in the ICU than patients with a low reactance (X(L) < 13). X(L) was found to be a reliable and clinically relevant measurement. These results justify further clinical research to explore how this information may be used to improve patient management.

1H-NMR-based metabolic signatures of clinical outcomes in trauma patients--beyond lactate and base deficit

The determination of reliable biomarkers capable to predict clinical outcome of a trauma patient remains essential toward better therapeutic management of the patient in the intensive care unit. Assessment of global metabolic profiling using quantitative nuclear magnetic resonance (NMR)-based metabolomics offers an attractive modern methodology for fast and comprehensive determination of multiple circulating metabolites and for establishing metabolic phenotype of survivors versus nonsurvivors. Multivariate data analysis on 43 quantitative metabolic parameters identified three lipid metabolites, triacylglycerol, glycerol heads of phospholipids, and monounsaturated fatty acids, as being the most discriminative markers to separate survivors versus nonsurvivors at the time of admission. Glucose and glutamate were intermediate predictors, followed by lactate and hydroxybutyrate as two low-weight predictors. Ultimately, cellular and subcellular failure in nonsurviving trauma patients results in multiple systemic biochemical effects and in changes in circulating metabolites in the blood that are characteristic for decreased lipid synthesis and urea cycle activity in the liver, and for increased hyperglycemia, lactic, and ketoacidosis.

Techniques to assess tissue oxygenation in the clinical setting

The microcirculation plays an essential role in health and disease. Microvascular perfusion can be assessed directly using laser Doppler flowmetry and various imaging techniques or indirectly using regional capnometry and measurement of indicators of mismatch between oxygen delivery and oxygen consumption or indices of disturbed cellular oxygen utilization. Assessment of microvascular oxygen availability implies measurement of oxygen pressure or measurement of hemoglobin oxygen saturation. Microvascular function is assessed using other methods, including venous plethysmography. In this paper, I review current knowledge concerning assessment of the microcirculation with special emphasis on methods that could be used at the bedside.

Central venous to mixed venous blood oxygen and lactate gradients are associated with outcome in critically ill patients

OBJECTIVE

Blood O(2) saturation and lactate concentration gradients from superior vena cava (SVC) to pulmonary artery (PA) occur in critically ill patients. These gradients (DeltaSO(2) and Delta[Lac]) may be positive or negative. We tested the hypothesis that positive DeltaSO(2) and Delta[Lac] are associated with improved survival in critically ill patients.

DESIGN AND SETTING

Multinational, prospective observational study conducted in six medical and surgical ICUs.

PATIENTS

Consecutive sample of 106 adults requiring insertion of a pulmonary artery catheter (PAC). Average age was 59.5 +/- 15.5 years, APACHE II score was 15.5 +/- 6.7 (mean +/- SD). Main outcome measure was 28-day mortality.

INTERVENTIONS

None.

MEASUREMENTS AND RESULTS

We drew blood samples from the proximal and distal ports of PACs every 6 h from the time of PAC insertion (Initial measurement) until its removal (Final measurement). Samples were analyzed for SO(2), [Lac], glucose concentration and blood gases. Hemodynamic measurements were obtained after blood samples. We monitored patients for 30.9 +/- 11.0 h. Overall mortality rate was 25.5%. More survivors had mean and final DeltaSO(2) > or = 0 and Delta[Lac] > or = 0 than decedents (p < 0.01; p < 0.05 respectively). On the average, DeltaSO(2) and Delta[Lac] were positive in survivors and negative in decedents. Survival odds ratios for final measurements of DeltaSO(2) > or = 0 and Delta[Lac] > or = 0 were 19.22 and 7.70, respectively (p < 0.05).

CONCLUSIONS

A strong association exists between positive DeltaSO(2) and Delta[Lac] and survival in critically ill patients. Whether therapy aimed at increasing DeltaSO(2) and Delta[Lac] results in improved ICU survival remains to be determined.

Hemodynamic monitoring in shock and implications for management. International Consensus Conference, Paris, France, 27-28 April 2006

OBJECTIVE

Shock is a severe syndrome resulting in multiple organ dysfunction and a high mortality rate. The goal of this consensus statement is to provide recommendations regarding the monitoring and management of the critically ill patient with shock.

METHODS

An international consensus conference was held in April 2006 to develop recommendations for hemodynamic monitoring and implications for management of patients with shock. Evidence-based recommendations were developed, after conferring with experts and reviewing the pertinent literature, by a jury of 11 persons representing five critical care societies.

DATA SYNTHESIS

A total of 17 recommendations were developed to provide guidance to intensive care physicians monitoring and caring for the patient with shock. Topics addressed were as follows: (1) What are the epidemiologic and pathophysiologic features of shock in the ICU? (2) Should we monitor preload and fluid responsiveness in shock? (3) How and when should we monitor stroke volume or cardiac output in shock? (4) What markers of the regional and micro-circulation can be monitored, and how can cellular function be assessed in shock? (5) What is the evidence for using hemodynamic monitoring to direct therapy in shock? One of the most important recommendations was that hypotension is not required to define shock, and as a result, importance is assigned to the presence of inadequate tissue perfusion on physical examination. Given the current evidence, the only bio-marker recommended for diagnosis or staging of shock is blood lactate. The jury also recommended against the routine use of (1) the pulmonary artery catheter in shock and (2) static preload measurements used alone to predict fluid responsiveness.

CONCLUSIONS

This consensus statement provides 17 different recommendations pertaining to the monitoring and caring of patients with shock. There were some important questions that could not be fully addressed using an evidence-based approach, and areas needing further research were identified.

Clinical review: New technologies -- venturing out of the intensive care unit

The delivery of critical care is no longer limited to the intensive care unit. The information gained by utilization of new technologies has proven beneficial in some populations. Research into earlier and more widespread use of these modalities may prove to be of even greater benefit to critically ill patients.

Assessment of Graded Intestinal Hypoperfusion and Reperfusion Using Continuous Saline Tonometry in a Porcine Model

OBJECTIVE

To evaluate effects of graded intestinal hypoperfusion and reperfusion on intestinal metabolic parameters as assessed by a modified continuous saline tonometry technique.

MATERIALS

Twelve barbiturate-anaesthetized female pigs.

METHODS

Measurements were performed prior to and during three predefined levels of superior mesenteric mean arterial blood pressure (P(SMA) 70, 50 and 30 mmHg, respectively, each 80 min long), obtained by an adjustable clamp around the origin of the superior mesenteric artery, and during reperfusion. We continuously measured jejunal mucosal perfusion (laser Doppler flowmetry), jejunal tissue oxygen tension (PO(2TISSUE); microoximetry) and intramucosal PCO(2) (continuous saline tonometry) and calculated net intestinal lactate production, mesenteric oxygenation, PCO(2) gap (jejunal mucosal PCO(2)-arterial PCO(2)) and pHi.

RESULTS

At P(SMA) 70 and 50 mmHg mesenteric oxygen uptake and net lactate production remained unaltered, in spite of decreased oxygen delivery. At these P(SMA) levels PCO(2) gap increased, while pHi and PO(2TISSUE) decreased. At P(SMA) 30 mmHg pronounced increases in PCO(2) gap and mesenteric net lactate production as well as marked decreases in PO(2TISSUE) and pHi were demonstrated. Data indicate absence of anaerobic conditions at an intestinal perfusion pressure (IPP)> or =41 mmHg, a pHi> or =7.22 or PCO(2) gap< or =15.8 mmHg.

CONCLUSIONS

Continuous saline tonometry detected intestinal ischemia as induced by graded reductions in IPP. A threshold could be defined above which intestinal ischemia does not occur.

Gastric tonometry and monitoring gastrointestinal perfusion: using research to support nursing practice

The principles and physiological underpinnings of gastric tonometry are reviewed. Tonometric variables, including the PtCO2, pHi and CO2 gap, are described and critiqued as measurements of gastrointestinal perfusion. Increases in gastrointestinal CO2 unrelated to gastrointestinal hypoperfusion are discussed within different clinical contexts. The technical limitations of gastric tonometry, including procedural errors and PtCO2 measurement are discussed in relation to the accuracy of tonometric measurements. Tonometric measurement using semi-continuous air tonometry is introduced as a strategy to minimize technical limitations.

Goal-oriented shock resuscitation for major torso trauma: what are we learning?

Shock resuscitation is an obligatory intervention for severely injured patients who present in shock. During the past 15 years, with widespread acceptance of "damage control" surgery and early triage to the intensive care unit (ICU) to optimize resuscitation, the lives of many major trauma victims have been saved, and much has been learned about shock resuscitation. Due largely to the work of Shoemaker et al., a resuscitation strategy based on a standardized process using O(2) delivery index (DO(2)I) as an endpoint and physiologic performance goal for interventions has been developed, studied, and refined for resuscitation of shock caused by major trauma. DO(2)I >or=600 mL O(2)/min-m2 is the only resuscitation endpoint variable that has been tested in prospective randomized trials (PRTs) of trauma patient outcome. These PRTs are limited, and their results are not conclusive. Results from other investigators, including our group, using similar process and endpoints, are indicating similar performance and outcomes. We believe that DO(2)I is a useful endpoint because it integrates three important variables, ie, hemoglobin concentration [Hb], arterial hemoglobin O(2) saturation, and cardiac output. We have found DO(2)I >or=500 mL O(2)/min-m2 to be an endpoint with more general applicability, but we believe that the standardized process is more important than the specific endpoint. To standardize our process, we have developed a computerized decision support tool for shock resuscitation. This technology has provided novel data collection and has permitted refinement of the bedside process. Our data analysis indicates that the next challenge will be to develop a similar pre ICU resuscitation process that will use less invasive monitors and different endpoints. Identification of the high-risk resuscitation nonresponders early in the resuscitation process will be needed to redirect their clinical trajectories. As an endpoint for interventions for goal-directed resuscitation in the critically injured trauma patient, systemic O(2) delivery is the current state of the art and the basis for near future development of clinical processes for resuscitation of shock due to major trauma.

Intramucosal pH monitoring during liver transplantation

PURPOSE

To apply tonometry as a quick estimation of the early liver graft function.

PATIENTS AND METHODS

Forty-five liver-transplanted patients were examined. Data were collected prospectively and analysed retrospectively. According to the early graft function, patients were classified into two groups: in group 1 (n = 28) adequate graft function, in group 2 (n = 17) deteriorated graft function was detected in the early post-operative period. Complete conventional and volumetric haemodynamic monitoring and intramucosal pH (pHi), regional CO2 tension (PrCO2) measurements were performed during surgery and until the 36 hours post-operatively.

RESULTS

In group 2 the packed blood cell, fresh frozen plasma consumption intraoperatively, and the time of hepatectomy were significantly higher; ICU treatment days, respiration time was longer and mortality rate was higher. Almost the whole examination period pHi was mostly below 7.3 and PrCO2 above 50 mmHg in group 2. There were significant differences in pHi between the groups from the preparation phase until the 24th post-operative hour. In group 2, there were significantly lower values in cardiac output in the whole examination period and in the mean arterial pressure values in the revascularization phase. In group 1, the oxygen delivery values were significantly higher in the preparation phase and oxygen consumption values after revascularization phase. With regression analysis there were no significant correlations between pHi, PrCO2 and global haemodynamic parameters.

CONCLUSION

Regional parameters were completely different from global haemodynamic parameters, therefore pHi and PrCO2 can be a good indicator of the early liver graft dysfunction.

Pharmacokinetic and pharmacodynamic considerations when treating patients with sepsis and septic shock

Sepsis and septic shock are accompanied by profound changes in the organism that may alter both the pharmacokinetics and the pharmacodynamics of drugs. This review elaborates on the mechanisms by which sepsis-induced pathophysiological changes may influence pharmacological processes. Drug absorption following intramuscular, subcutaneous, transdermal and oral administration may be reduced due to a decreased perfusion of muscles, skin and splanchnic organs. Compromised tissue perfusion may also affect drug distribution, resulting in a decrease of distribution volume. On the other hand, the increase in capillary permeability and interstitial oedema during sepsis and septic shock may enhance drug distribution. Changes in plasma protein binding, body water, tissue mass and pH may also affect drug distribution. For basic drugs that are bound to the acute phase reactant alpha(1)-acid glycoprotein, the increase in plasma concentration of this protein will result in a decreased distribution volume. The opposite may be observed for drugs that are extensively bound to albumin, as the latter protein decreases during septic conditions. For many drugs, the liver is the main organ for metabolism. The determinants of hepatic clearance of drugs are liver blood flow, drug binding in plasma and the activity of the metabolic enzymes; each of these may be influenced by sepsis and septic shock. For high extraction drugs, clearance is mainly flow-dependent, and sepsis-induced liver hypoperfusion may result in a decreased clearance. For low extraction drugs, clearance is determined by the degree of plasma binding and the activity of the metabolic enzymes. Oxidative metabolism via the cytochrome P450 enzyme system is an important clearance mechanism for many drugs, and has been shown to be markedly affected in septic conditions, resulting in decreased drug clearance. The kidneys are an important excretion pathway for many drugs. Renal failure, which often accompanies sepsis and septic shock, will result in accumulation of both parent drug and its metabolites. Changes in drug effect during septic conditions may theoretically result from changes in pharmacodynamics due to changes in the affinity of the receptor for the drug or alterations in the intrinsic activity at the receptor. The lack of valid pharmacological studies in patients with sepsis and septic shock makes drug administration in these patients a difficult challenge. The patient's underlying pathophysiological condition may guide individual dosage selection, which may be guided by measuring plasma concentration or drug effect.

Sublingual capnometry: an alternative to gastric tonometry for the management of shock resuscitation

Normal vital signs do not reflect the physiologic aberrations after blood loss. Recognition of hypoperfusion during resuscitation can avoid the development of multiple organ failure. Advances in technology enable the clinician to monitor changes, potentially identifying tissue hypoxia much earlier than previously was possible. Gastric tonometry can be quite helpful in the intensive care unit in identifying gastric hypoperfusion, but has considerable drawbacks. The ability to monitor P(SI)CO(2) via sublingual capnometers overcomes some limitations of gastric tonometry and may be a valuable aid in the prehospital phase, the emergency department, and the intensive care unit in identifying end points of resuscitation.

PCO(2) in the large intestine of mice, rats, guinea pigs, and dogs and effects of the dietary substrate

PCO(2) in the lumen and serosa of cecum and colon was measured in rats, guinea pigs, and dogs to examine the relationship between serosal PCO(2) and the incidence of intestinal necrotic lesions after administration of gas-carrier contrast agents in rodents. The effects of the dietary substrate were tested in a group of mice maintained on a diet based on glucose as the only carbohydrate source. The anesthetic used was a fentanyl-fluanison-midazolam mixture (rodents) and pentobarbital (dogs). PCO(2) was measured in vivo and postmortem, and the kinetics of the postmortem serosal PCO(2) [transmural CO(2) flux (J(CO(2)))] was calculated. PCO(2) in the cecal serosa and lumen, respectively, was 64 +/- 4 and 392 +/- 18 Torr in rats, 67 +/- 3 and 276 +/- 17 Torr in guinea pigs, and 73 +/- 6 and 137 +/- 7 Torr in mice on glucose-based diet. In the colon serosa and lumen of dogs, PCO(2) was 30 +/- 6 and 523 +/- 67 Torr, respectively. Serosal PCO(2) increased rapidly after death in rats and slower in guinea pigs and mice, and the slowest change was observed in dogs. Compared with dogs, serosal PCO(2) and J(CO(2)) of rats and guinea pigs were significantly higher. Serosal PCO(2) of guinea pigs was similar to that of rats, whereas the J(CO(2)) of guinea pigs was significantly lower. These data suggest a causal relationship between the ability of the cecal and colonic wall to act as a barrier to CO(2) diffusion and the presence of characteristic gas-carrier contrast agent-induced intestinal lesions in mice and rats and their absence in guinea pigs, dogs, and other species.

Endothelin-1 blockade corrects mesenteric hypoperfusion in a porcine low cardiac output model

OBJECTIVE

To study the importance of endothelin-1-induced vasoconstriction in a model of acute and maintained low cardiac output, by investigating regional changes within the mesenteric and particularly the intestinal mucosal circulation.

DESIGN

Prospective, controlled animal study.

SETTING

University-affiliated research laboratory.

SUBJECTS

Thirteen fasted, anesthetized, mechanically ventilated landrace pigs.

MEASUREMENTS AND MAIN RESULTS

Cardiac output, portal venous blood flow, renal arterial flow, jejunal mucosal microcirculation by laser Doppler flowmetry, jejunal capnotonometry (Pco2 gap), and jejunal mucosal oxygenation (tPo2) were monitored. Cardiac tamponade was established to reduce portal venous blood flow to a preset end point at two thirds of baseline. Measurements were made at baseline, after 90 mins of cardiac tamponade, and 90 mins after the administration of the combined endothelinA/endothelinB antagonist tezosentan at 1 mg.kg-1.hr-1 during tamponade in seven animals. Six animals served as time controls and received only the vehicle. Cardiac tamponade decreased portal venous blood flow, renal arterial flow, and laser Doppler flowmetry, whereas the Pco2 gap increased. The change in tPo2 failed to gain statistical significance (p =.08). Administration of tezosentan during tamponade restored portal venous blood flow and laser Doppler flowmetry to baseline values, increased tPo2 above baseline, and decreased Pco2 gap. No effect on renal arterial flow was observed. Investigated variables remained unchanged in control animals after induction of cardiac tamponade.

CONCLUSIONS

Endothelin-1 blockade in acute cardiac failure improves mesenteric, but not renal, perfusion, illustrating the regional importance of endothelin-1-induced vasoconstriction. Importantly, endothelin-1 blockade restored mucosal blood flow and oxygenation, which might be particularly interesting considering the implications for maintenance of mucosal barrier integrity in low output states.

Dopamine-1 receptor stimulation attenuates the vasoconstrictive response to gut ischemia

The effects of fenoldopam, a dopamine-1 (DA-1) receptor agonist, were studied in two groups of anesthetized dogs before and after induction of splanchnic ischemia by way of hemorrhage. During the first portion of the experiment, both groups received fenoldopam (1.5 microg x kg(-1) x min(-1)) for 45 min followed by a 45-min washout. During the second portion, hemorrhage (10 ml/kg) was induced, followed by no intervention in group I (controls) and restarting of the fenoldopam infusion in group II. Prehemorrhage, fenoldopam increased composite portal blood flow by 33% (P < 0.01). After hemorrhage-induced splanchnic ischemia, fenoldopam restored portal vein blood flow to near baseline, maintained the splanchnic fraction of cardiac output, and attenuated the rise in gut mucosal PCO(2). DA-1 receptor stimulation increased portal blood flow and redistributed blood flow away from the serosal layer in favor of the mucosa during basal conditions and after hemorrhage, suggesting a more concentrated distribution of splanchnic DA-1 receptors within the mucosal layer vasculature. Fenoldopam maintained splanchnic blood flow during hypoperfusion and attenuated the splanchnic vasoconstrictive response to hemorrhage.

Effect of hemodilution on tissue perfusion and blood coagulation during radical hysterectomy

OBJECTIVE

The goal of this study was to evaluate the safety of hemodilution on global and splanchnic perfusion and blood coagulation during radical hysterectomy.

METHODS

A pulmonary artery catheter and a gastric tonometry catheter were placed in 16 patients with cervical carcinoma. Global perfusion indices, splanchnic perfusion index, and coagulation tests were obtained. Blood was removed to achieve a hemoglobin measurement of 8-9 9 g/dL. Three more measurements were repeated after hemodilution, at the end of surgery, and after the retransfusion of blood. Analysis of variance was used to determine statistical significance.

RESULTS

Sixteen patients with cervical carcinoma had 1.0 +/- 0.3 L (mean +/- SD) of blood removed and had a blood loss of 0.8 +/- 0.7 L. Hemodiluted preoperative hemoglobin was 8.7 +/- 1 g/dL. All of the global perfusion indices, except for arterial pH and oxygen consumption, decreased after hemodilution and recovered with the retransfusion of blood (P < or = 0.004). Splanchnic perfusion and coagulation tests were unchanged (P > or = 0.1). Major complication was pulmonary edema in one patient.

CONCLUSION

Hemodilution during radical hysterectomy, in this select group of patients, does not appear to compromise tissue perfusion or coagulation.

Effects of olprinone, a new phosphodiesterase inhibitor, on gastric intramucosal acidosis and systemic inflammatory responses following hypothermic cardiopulmonary bypass

BACKGROUND

Phosphodiesterase (PDE) III inhibitors have both an inotropic and a peripheral vasodilatory effect, and also inhibit the activation of macrophages. Thus a newly developed PDE III inhibitor, olprinone, could modify gastric intramucosal pH (pHi), systemic oxygen consumption, and systemic inflammatory responses in patients undergoing cardiac surgery with cardiopulmonary bypass (CPB).

METHODS

We studied 23 patients. In 15 patients, olprinone (0.1 or 0.2 microg x kg(-1) x min(-1)) was administered from the commencement of CPB until their admission to the ICU. The other 8 patients received placebo. The pHi and regional CO2 tension (PrCO2) were assessed by a capnometric air tonometry. Systemic inflammatory responses were evaluated by serum interleukin-6 (IL-6), IL-10, and leucocyte counts.

RESULTS

The pHi and PCO2-gap, the difference between PrCO2 and arterial CO2 tension (PaCO2), showed a transient decrease and an increase after CPB, respectively. Although olprinone did not affect pHi, olprinone at 0.2 microg x kg(-1) x min(-1) significantly lessened post-CPB increase in PCO2-gap. Olprinone at 0.2 microg x kg(-1) x min(-1) significantly increased IL-10 and reduced the extent of leucocytosis, while it did not affect IL-6 levels. At the same dosage, olprinone also lessened the surge in systemic oxygen uptake index (VO2) and augmented the increase in mixed oxygen saturation (SvO2) both of which occurred after CPB. At 0.1 microg x kg(-1) x min(-1), however, olprinone did not show any significant effect.

CONCLUSION

Our results suggest that olprinone at 0.2 microg x kg(-1) x min(-1) suppresses gastric intramucosal acidosis and systemic inflammation following CPB.

Effect of low-dose milrinone on gastric intramucosal pH and systemic inflammation after hypothermic cardiopulmonary bypass

OBJECTIVE

To investigate the usefulness of low-dose milrinone on gastric intramucosal pH (pHi) and systemic inflammation in patients undergoing hypothermic cardiopulmonary bypass (CPB).

DESIGN

Prospective randomized study.

SETTING

University hospital.

PARTICIPANTS

Twenty patients scheduled for cardiac surgery.

INTERVENTIONS

Ten patients were administered a low dose of milrinone, 0.25 microg/kg/min, from the initiation of CPB to 1 hour after admission to the intensive care unit. The other patients were administered saline. Supplemental inotropes and intravenous fluid were given to obtain adequate mean arterial blood pressure and pulmonary artery occlusion pressure.

MEASUREMENTS AND RESULTS

Gastric pHi and carbon dioxide pressure (PCO2) were assessed by capnometric air tonometry. The difference between PCO2 and arterial carbon dioxide pressure (PaCO2), PCO2-gap, was also examined. Systemic inflammatory responses were evaluated by serum interleukin-6 and leukocyte counts. Hemodynamics, oxygen delivery index, and oxygen uptake index were monitored with catheters in the radial and pulmonary arteries (thermodilution). The hepatic venous blood flow and left ventricular flow were measured using transesophageal echocardiography. Milrinone prevented gastric intramucosal acidosis, detected as a decrease in pHi or an increase in PCO2-gap, without affecting hepatic venous blood flow. Increases in interleukin-6, leukocyte count, and oxygen uptake index, all of which developed after CPB, were significantly less in the milrinone group than in the control group.

CONCLUSION

These results suggest that in patients undergoing hypothermic CPB, supplemental low-dose milrinone prevents gastric intramucosal acidosis and increases in some markers of systemic inflammation.

Effects of continuous haemofiltration vs intermittent haemodialysis on systemic haemodynamics and splanchnic regional perfusion in septic shock patients: a prospective, randomized clinical trial

BACKGROUND

Parameters of splanchnic regional perfusion, like intramucosal pH (pHi) and pCO(2) (pCO(2)i), may predict outcome in septic shock patients. Continuous venovenous haemofiltration (CVVH) has been considered beneficial in haemodynamically unstable septic shock patients. In a prospective, randomized, clinical study, we investigated whether CVVH, in comparison to intermittent haemodialysis (IHD), is able to improve splanchnic regional perfusion in critically ill patients.

METHODS

Thirty septic shock patients with acute renal failure were randomized to either CVVH (n=20) or IHD (n=10) groups for renal replacement therapy. Patient characteristics at baseline were not different in terms of severity of illness (APACHE II scores), haemodynamics, and pHi/pCO(2)i values. Systemic haemodynamics, oxygen transport variables, and splanchnic regional perfusion parameters were measured at 0.5, 2, 4 and 24 h after initiation of renal replacement therapy. There were no major changes in vasopressor support throughout the 24-h study period.

RESULTS

In contrast to IHD, CVVH caused a decrease in heart rate (-3+/-11 vs +9+/-8/min, P<0.01) and an increase in systolic blood pressure (+12+/-1 vs -5+/-17 mmHg, P<0.05) after 2 h. After 24 h, increased systemic vascular resistance was found in the CVVH group in comparison with the IHD group (+312+/-755 vs -29+/-89 dyne/cm(5), P<0.05) and was accompanied by a decrease in cardiac output (-1.54+/-1.4 vs -0.25+/-0.9 l/min, P<0.01). However pHi values remained constant throughout the 24-h study period in both groups and were not different between the groups (CVVH 7.19+/-0.1 vs IHD 7.19+/-0.1, n.s.) as did the pCO(2)i values (CVVH +7+/-17 vs IHD 0+/-15 mmHg, n.s.) and pCO(2) gap values (CVVH +6+/-15 vs IHD +5+/-12 mmHg, n.s.).

CONCLUSIONS

Despite different changes of systemic haemodynamics between CVVH and IHD, CVVH did not improve parameters of splanchnic regional perfusion like pHi, pCO(2)i or pCO(2) gap in septic shock patients.

Gastric tonometer monitoring in infants undergoing repair of coarctation of the aorta

OBJECTIVE

To evaluate gastric tonometer monitoring for splanchnic hypoperfusion in infants during surgical intervention for aortic coarctation, especially within aortic cross-clamp periods.

DESIGN

A prospective study.

SETTING

Cardiovascular intensive care unit in a university hospital.

PARTICIPANTS

Fourteen infant patients after elective, uncomplicated repair of coarctation of the aorta.

INTERVENTIONS

After the anesthesia induction, a 7F tonometry catheter was inserted into the stomach oropharyngeally. Gastric carbon dioxide, arterial blood gases, blood pressure of upper extremities, and hematocrit values were measured in 5 different time intervals. Time periods were as follows: T1 (after the anesthesia induction), T2 (before aortic cross-clamp), T3 (immediately after aortic cross-clamp removal), T4 (40 minutes after aortic cross-clamp removal), and T5 (as the patient reached the intensive care unit). Intramucosal pH was measured by means of the Henderson-Hasselbach equation. The mean values of all parameters were calculated. According to T1 time, T2, T3, T4, and T5 times were compared with Student's t-test.

MEASUREMENTS AND MAIN RESULTS

Mean aortic cross-clamp time was 19.4 +/- 6.6 minutes. Intramucosal pH values of T3 (p < 0.001) and T4 (p < 0.01) were found to be lower than values of T1. The gastric carbon dioxide values of T3 were significantly higher than T1 (p < 0.01), and bicarbonate and arterial pH values of T3 were significantly lower (p < 0.01). There were no significant differences in other parameters over time intervals.

CONCLUSION

Splanchnic hypoperfusion exists during aortic cross-clamping in infant aortic coarctation surgery, and the tonometric catheter is considered to be a safe method for monitoring this hypoperfusion.

Comparison of the response of saline tonometry and an automated gas tonometry device to a change in CO2

OBJECTIVE

To examine the speed of response of saline tonometry and an automated gas tonometry system by using standard tonometry catheters.

DESIGN

In vitro validation study.

SETTING

Experimental research laboratory.

INTERVENTIONS

Tonometry catheters were placed in a test chamber designed to simulate the lumen of a hollow viscus and were exposed to a rapid change in CO2 from 0% to 5% or 10%. Measured CO2 over time was fit to a mathematical model to determine the response time constant (the time to reach 63% of the final value) for each system.

MEASUREMENTS AND MAIN RESULTS

Response time to a change in CO2 was significantly faster with the automated gas system than with traditional saline tonometry. The mathematical time constant for a 5% change in CO2 in a gas environment was 2.8 mins (95% confidence interval, 2.6-3.0 mins) for the gas and 6.3 mins (95% confidence interval, 5.8-7.3 mins) for the saline technique. These times were longer for the CO2 change in a liquid environment: The time constant was 4.6 mins (95% confidence interval, 4.5-4.7 mins) for the gas system and 7.8 mins (95% confidence interval, 7.15-8.6 mins) for the saline tonometry. There was a significantly lower final equilibration value for the CO2 measurement with saline tonometry. There was essentially no difference in time constants for each system for a 5% change compared with a 10% CO2 change, except for a slightly faster time constant for the gas tonometry system with a 5% change in the gas environment (5%: 2.8 mins vs. 10%: 3.3 mins).

CONCLUSIONS

The automated gas tonometry system has a significantly faster response to a change in CO2 than conventional saline tonometry.

Changes in gastric intramucosal pH and circulating blood volume following coronary artery bypass grafting

PURPOSE

To determine the changes in gastric intramucosal pH (pHi) following coronary artery bypass grafting (CABG) in comparison with systemic hemodynamic variables and circulating blood volume (BVc).

METHODS

Twenty patients who underwent CABG under mild hypothermic cardiopulmonary bypass (CPB) were included. Hemodynamic variables and the values of pHi were obtained at 3,6, 12 and 24 hr after admission to the intensive care unit (ICU). The pHi was measured by gastric tonometric catheter. The BVc was measured by carbon monoxide (CO)-labeled hemoglobin (CO-Hb) dilution method (CO method) at 6 and 24 hr after ICU admission.

RESULTS

Systemic vascular resistance index (SVRI) and pulmonary vascular resistance index (PVRI) decreased with time. Systemic oxygen delivery index (DO2I) and systemic oxygen consumption index (VO2I) showed a gradual increase during the study period. By contrast, pHi decreased to the lowest value (7.26+/-0.05) at six hours and returned to normal levels (7.34+/-0.04) at 24 hr after ICU admission. Changes in BVc between six and 24 hr ranged from -242 ml to 978 ml (mean, 334+/-338 ml). The pHi increased in patients whose BVc increased by > 300 ml. Mean fluid balance was negative in this period (-386+/-667 ml; range, -1786 - + 423 ml).

CONCLUSION

The pHi showed the lowest value at six hours and returned to normal at 24 hr after ICU admission. The pHi increased with the decrease in vascular resistance and with the increases in BVc in this period. The improvement of pHi, an indicator of splanchnic perfusion, appears to be related to systemic vasodilatation and an increase in BVc.

Systemic hemodynamics, gastric intramucosal PCO2 changes, and outcome in critically ill burn patients

OBJECTIVES

To define the hemodynamic and gastric intramucosal PCO2 (PiCO2) changes during the first 48 hrs after burn trauma and to analyze their relationship with outcome.

DESIGN

Prospective, observational study in a cohort of consecutively admitted critically ill burn patients.

SETTING

Intensive care burn unit in a university hospital.

PATIENTS

Forty-two patients with burns covering >20% of body surface area or inhalation injury.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Patients were monitored with an oximetric pulmonary arterial catheter and a gastric tonometer to measure PiCO2. The difference between arterial and gastric mucosal PCO2 (P[i-a]CO2) was considered indicative of gastric mucosal hypoxia. Hemodynamic and PiCO2 measurements were performed during the first 48 hrs after admission. Patients suffered burns covering 36.1% +/- 14.3% (mean +/- SD) and 45.3% +/- 21.9% of body surface area (survivors and nonsurvivors, respectively). All patients were successfully resuscitated by conventional standards. Nonsurvivors (n = 16) died a median of 17 days after admission. In univariate analysis, the presence of shock during the resuscitation phase, age, mixed venous pH, P[i-a]CO2, right atrial pressure, pulmonary arterial pressure, pulmonary arterial occlusion pressure, cardiac index, systemic and pulmonary vascular resistance, left ventricular stroke work index, mixed venous oxygen saturation, and systemic oxygen delivery, consumption, and extraction ratio, measured over the first 12 hrs after admission, were significantly (p < .05) different between survivors and nonsurvivors. These differences disappeared after 12 hrs after admission. Multivariate analysis identified age, percentage body surface area burned, and oxygen delivery index (6 hrs after admission) as factors independently associated with a poor outcome. P[i-a]CO2 (12 hrs after admission) was significantly greater in patients with than in those without inhalation injury (17 +/- 13 torr [2.26 +/- 1.73 kPa] vs. 6 +/- 10 torr [0.79 +/- 1.33 kPa]; p = .005). Patients with a P[i-a]CO2 difference (6 hrs after admission) > or =10 torr (1.33 kPa) had a mortality rate of 56% vs. 25% of those patients with <10 torr (p = .044).

CONCLUSIONS

Our data indicate that there are hemodynamic and biochemical changes that occur early after burn trauma that are associated with prognosis after an apparently successful resuscitation. Particularly, a hemodynamic profile characterized by systemic acidosis, low systemic blood flow, and systemic and pulmonary vasoconstriction early after trauma is associated with a poor outcome. Additionally, intestinal mucosal acidosis occurs after burn trauma, is influenced by inhalation injury, and is a variable related to outcome.

Severe sepsis and septic shock. Definitions, epidemiology, and clinical manifestations

Severe sepsis and septic shock are frequently encountered conditions in today's hospital environment. The incidence appears to be increasing despite our growing armamentarium of antibiotics and our enhanced knowledge of the pathophysiologic processes at play. The clinical presentation may take a variety of forms, especially in patients at the extremes of age and in the immunocompromised population. A high index of suspicion and prompt institution of appropriate antimicrobial treatment is mandatory for a successful outcome. It is hoped that adoption of uniform definitions will aid in research and in effective communication concerning sepsis and its adverse sequelae.

Effect of acute moderate changes in PaCO2 on global hemodynamics and gastric perfusion

OBJECTIVE

To describe global hemodynamics and splanchnic perfusion changes in response to acute modifications in Paco2 in hemodynamically stable patients.

DESIGN

Prospective, randomized crossover study.

SETTING

Medical-surgical intensive care unit at a community hospital (400,000 inhabitants).

PATIENTS

Ten critically ill patients who were sedated, paralyzed, and mechanically ventilated.

INTERVENTIONS

Hypercapnia and hypocapnia were obtained by increasing and reducing instrumental deadspace in random order. After each intervention, patients returned to the basal condition. Each period lasted 80 min: 20 min to achieve stable Paco2 and 60 min for tonometer equilibration. In each period, global hemodynamic variables and tonometric data were collected. The periods were compared using analysis of variance.

MEASUREMENTS AND MAIN RESULTS

Acute hypercapnia (Paco2 from 40+/-3 to 52+/-3 torr, p<.05) increased cardiac index (3.43+/-0.37 vs. 3.97+/-0.43 mL/min/m2, p<.05), heart rate (95+/-6 vs. 105+/-3 beats/min, p<.05), and mean pulmonary artery pressure (21+/-1 vs. 24+/-1 mm Hg, p<.05) and reduced systemic vascular resistance (992+/-98 vs. 813+/-93 dyne x sec/ cm5, p<.05) and oxygen extraction ratio (27+/-3% vs. 22+/-2%, p<.05). Standardized intramucosal Pco2 increased from 49+/-2 to 61+/-3 torr (p<.05) with an associated decrease in calculated intramucosal pH ([pHi] 7.35+/-0.03 vs. 7.25+/-0.02, p<.05), but the gastro-arterial Pco2 gradient (deltaPco2) did not change. Acute hypocapnia (Paco2 from 41+/-3 to 34+/-3 torr, p<.05; pH 7.41+/-0.01 to 7.47+/-0.02, p<.05) induced slight increments in systemic vascular resistance (995+/-117 vs. 1088 +/- 160 dyne x sec/cm5, p<.05) and oxygen extraction ratio (28+/-2% vs. 30+/-2%, p<.05). Standardized intramucosal Pco2 decreased (50+/-4 vs. 44+/-3 torr, p<.05), pHi increased (7.33+/-0.03 vs. 7.36+/-0.02; p<.05), but deltaPco2 did not change.

CONCLUSIONS

In this small group of stable patients, moderate acute variations in Paco2 had a significant effect on global hemodynamics, but splanchnic perfusion, assessed by deltaPco2, did not change. In these conditions, the use of pHi to evaluate gastric perfusion appears unreliable.

Accuracy of mucosal pH and mucosal-arterial carbon dioxide tension for detecting mesenteric hypoperfusion in acute canine endotoxemia

OBJECTIVE

To determine the level of mucosal-arterial Pco2 (Pco2 gap) that is both sensitive and specific for the detection of mesenteric hypoperfusion as defined by either a >50% reduction in portal blood flow or release of lactate by the gut.

DESIGN

Animal experiment.

SUBJECTS

Seven anesthetized, intubated, mechanically ventilated, and surgically instrumented mongrel dogs.

INTERVENTION

Escherichia coli endotoxin (1 mg/kg) given intravenously for 5 mins.

MEASUREMENTS AND MAIN RESULTS

Tonometric Pco2, arterial blood gases, arterial and portal venous lactates, and portal and systemic hemodynamic variables were measured. Mucosal pH (pHi) was calculated according to the manufacturers' instructions. From these data, receiver operating characteristics were calculated. Although animals were resuscitated to maintain a constant cardiac output, portal flow decreased from 350+/-101 to 152+/-75 mL/min (p<.01) and the gut released lactate into the portal circulation in all animals. Pco2 gap increased from 13.1+/-3.9 to 40.2+/-39.2 torr (p<.01) and was inversely correlated with portal blood flow (r2 = .20; p<.05). For detection of a >50% reduction in portal blood flow, a Pco2 gap of 20 torr yielded a maximum accuracy of 67% (sensitivity, 55%; specificity, 73%) and was less accurate than a pHi of 7.20, which yielded a maximum accuracy of 76% (sensitivity, 90%; specificity, 70%), although this difference was not significant (p = .24). There was also a correlation between pHi and portal blood flow (r2 = .31; p<.01). For detection of lactate release by the gut, a Pco2 gap of 20 torr was also 67% accurate (sensitivity, 53%; specificity, 78%), whereas a pHi of 7.10 achieved an accuracy of 64% (sensitivity, 40%; specificity, 83%), which was not significantly different.

CONCLUSION

Pco2 gap measurements are neither sensitive nor specific for mesenteric hypoperfusion with regard to total gut blood flow reductions of >50% or the release of lactate into the portal circulation.

A dobutamine test can disclose hepatosplanchnic hypoperfusion in septic patients

In 36 hemodynamically stable septic patients, we explored whether changes in gastric mucosal-arterial PCO(2) gradient (PCO(2)gap) induced by a short-term dobutamine infusion may reveal hepatosplanchnic hypoperfusion. Hepatosplanchnic blood flow (HSBF) was determined by the continuous indocyanine green infusion technique and gastric mucosal PCO(2) (Pg(CO(2))) by saline tonometry. In each patient, hemodynamic measurements, blood samples, and Pg(CO(2)) determinations were performed three times: first at baseline (DOB 0), second during a dobutamine infusion at a dose of 5 microgram/kg/min (DOB 5), and third at a dose of 10 microgram/kg/min (DOB 10). The results were analyzed by Wilcoxon's matched-pairs signed rank test and are presented as medians with ranges. The PCO(2)gap decreased preferentially in groups of patients with inadequate hepatosplanchnic perfusion, i.e., with a low fractional HSBF (HSBF/CI), defined as the ratio of the HSBF to the simultaneous cardiac index, or a high gradient between the mixed venous blood and the suprahepatic blood O(2) saturations (DSvh(O(2))). In the 11 patients with a DSvh(O(2)) above 20% at baseline, PCO(2)gap decreased from 12.1 (6.3 to 19.5) mm Hg at DOB 0 to 6.2 (2.5 to 19. 3) mm Hg at DOB 5 (p < 0.001 versus DOB 0), and to 4.2 (0.1 to 35.9) mm Hg at DOB 10 (p < 0.05 versus DOB 5), whereas in the 25 patients with a DSvh(O(2)) below 20% at baseline, PCO(2)gap did not change significantly. At no time was the PCO(2)gap correlated with HSBF/CI or DSvh(O(2)). We conclude that although the PCO(2)gap does not correlate well with global indexes of gut oxygenation, such a simple dobutamine infusion test could identify patients with inadequate hepatosplanchnic perfusion.

Comparison of skeletal muscle PO2, PCO2, and pH with gastric tonometric P(CO2) and pH in hemorrhagic shock

OBJECTIVES

To monitor PO2, PCO2, and pH in the interstitium of skeletal muscle (PmO2, PmCO2, and pHm) during hemorrhage, shock, and resuscitation using fiber-optic sensors and to compare Pco2 and pH in the interstitium of gastric mucosa (PrCO2 and pHi) obtained using gastric CO2 tonometry.

DESIGN

Prospective, controlled observational study in an acute experimental preparation.

SETTING

Physiology laboratory in a university medical school.

SUBJECTS

Nine mongrel dogs (20 to 35 kg).

INTERVENTIONS

Anesthesia was induced with pentobarbital (25 mg/kg iv) and maintained (10 mg/hr) after hemorrhagic shock. Mechanical ventilation was established to maintain baseline PaCO2 approximately 35 torr. Arterial, venous, and pulmonary artery catheters were placed. Blood flow probes were placed around the right femoral artery and vein. A probe (0.5 mm in diameter) with fiber-optic PO2, PCO2, and pH sensors was placed percutaneously in the adductor muscle of the right thigh. A gastric tonometer catheter was placed in the stomach lumen. After baseline data collection, controlled hemorrhage to mean arterial pressure (MAP) of 45 to 50 mm Hg was maintained for 1 hr. Shed blood was then reinfused. Blood gas, hemodynamic, and gastric tonometric data were collected during shock and reinfusion at 30-min intervals and hourly after reinfusion for 4 hrs. Normothermia was maintained.

MEASUREMENTS AND MAIN RESULTS

PmO2 decreased rapidly from 42 +/- 13 torr (mean +/- sD) to 13 +/- 9 torr within 15 mins and to 6 +/-4 torr within 30 mins of MAP reaching 45 mm Hg, and it recovered to baseline with reinfusion. pHm decreased gradually from 7.23 +/-0.09 to 6.89 +/- 0.25 during the 1-hr shock period and increased slowly toward baseline after reinfusion. pHi decreased from 7.43 +/- 0.14 to 6.91 +/- 0.23, and on average it returned to baseline 2 hrs after reinfusion. PmCO2 increased from 50 +/- 12 to 113 +/- 49 torr, increased further to 124 +/- 73 torr during reinfusion, and returned slowly toward baseline after reinfusion. PrCO2 increased from 35 +/- 8 to 60 +/- 19 torr and returned to baseline within 15 mins after reinfusion. During shock and reinfusion, oxygen delivery, mixed venous PO2, mixed venous oxygen saturation, and PmO2 responded with similar time courses. After reinfusion, on average, PmO2 exceeded baseline PmO2 and mixed venous PO2, and oxygen availability exceeded demand, suggesting an oxygen consumption defect. On average, PmCO2 and pHm did not return to baseline values 4 hrs after reinfusion, suggesting the persistence of anaerobic metabolic effects in skeletal muscle beyond the relatively short time that is required to reestablish baseline MAP, blood flow rates, oxygen delivery, PrCO2, and pHi.

CONCLUSIONS

PmO2, PmCO2, and pHm, monitored simultaneously using fiber-optic sensors in a single, small probe placed percutaneously, appear to indicate greater severity of shock and more prolonged resuscitation than conventional systemic or gastric tonometric variables.

Earlier prediction of anastomotic insufficiency after thoracic esophagectomy by intramucosal pH

OBJECTIVES

To assess the value of using intramucosal pH (pHi) measurements to evaluate the viability of the gastric tube after thoracic esophagectomy, and to determine whether these measurements may be used for early prediction of anastomotic insufficiency.

DESIGN

Prospective, observational study.

SETTING

University hospital in Japan.

PATIENTS

Thirty-nine patients who had undergone thoracic esophagectomy as a treatment for esophageal cancer.

INTERVENTIONS

The blood flow within the gastric tube was measured using a laser Doppler flowmeter during surgery. Periodic measurement of the pHi within the gastric tube (gastric pHi) began during surgery and continued until the second postoperative day. In 30 patients, the pHi within the rectum (rectal pHi) was measured simultaneously with the gastric pHi. The patients were divided into two groups: those patients who experienced anastomotic insufficiency constituted the leakage(+) group (n = 13); those patients who did not experience these complications were designated the leakage(-) group (n = 26).

MEASUREMENTS AND MAIN RESULTS

The gastric pHi values correlated significantly with simultaneous measurements of the blood flow at the anastomotic site (p < .01). The postoperative gastric pHi values increased gradually in the leakage(-) group but stopped increasing after surgery in the leakage(+) group. The rectal pHi values increased gradually after surgery in both groups. Furthermore, there was a significant difference between the two groups when their gastric pHi values were subtracted from their rectal pHi values from the morning of the first postoperative day until the morning of the second postoperative day (p < .05).

CONCLUSIONS

The gastric pHi values well reflected the viability of the gastric tube, especially when combined with the rectal pHi values. By measuring pHi, we can more accurately predict the risk of anastomotic insufficiency earlier after surgery and therefore give those patients who need it additional care to improve the viability of the gastric tube.

Sublingual capnometry: a new noninvasive measurement for diagnosis and quantitation of severity of circulatory shock

OBJECTIVE

To investigate the feasibility and predictive value of sublingual Pco2 (P(SL)CO2) measurements as a noninvasive and early indicator of systemic perfusion failure.

DESIGN

A prospective, criterion study.

SETTING

Emergency department and medical and surgical intensive care units of an urban community medical center.

PARTICIPANTS AND PATIENTS

Five normal human volunteers and 46 patients with acutely life-threatening illness or injuries.

INTERVENTIONS

Intra-arterial or automated cuff blood pressure and arterial blood lactate (LAC) were measured concurrently with P(SL)CO2.

RESULTS

P(SL)CO2 in five healthy volunteers was 45.2 +/- 0.7 mm Hg (mean +/- sD). Twenty-six patients with physical signs of circulatory shock and LAC >2.5 mmol/L had a P(SL)CO2 of 81 +/- 24 mm Hg. This contrasted with patients admitted without clinical signs of shock and LAC of <2.5 mmol/L who had a P(SL)CO2 of 53 +/- 8 mm Hg (p < .001). The initial P(SL)CO2 of 12 patients who died before recovery from shock was 93 +/- 27 mm Hg, and this contrasted with 58 +/- 11 mm Hg (p < .001) in hospital survivors. Increases in P(SL)CO2 were correlated with increases in LAC (r2 = .84; p < .001). When P(SL)CO2 exceeded a threshold of 70 mm Hg, its positive predictive value for the presence of physical signs of circulatory shock was 1.00. When it was <70 mm Hg, it predicted survival with a predictive value of 0.93.

CONCLUSION

P(SL)CO2 may serve as a technically simple and noninvasive clinical measurement for the diagnosis and estimation of the severity of circulatory shock states.

Gas supersaturation in the cecal wall of mice due to bacterial CO2 production

PCO2 in the lumen and serosa of cecum and jejunum was measured in mice. The anesthetic used was a fentanyl-fluanisone-midazolam mixture. PCO2 was recorded in vivo and postmortem. PCO2 was 409 +/- 32 Torr (55 +/- 4 kPa) in the cecal lumen and 199 +/- 22 Torr (27 +/- 3 kPa) on the serosa in normal mice. Irrigation of the cecum resulted in serosal and luminal PCO2 levels of 65-75 Torr. Cecal PCO2 was significantly lower in germ-free mice (65 +/- 5 Torr). Cecal PCO2 increased significantly after introduction of normal bacterial flora into germ-free mice. Introduction of bacterial monocultures into germ-free mice had no effect. After the deaths of the mice, cecal PCO2 increased rapidly in normal mice. The intestinal bacteria produced the majority of the cecal PCO2, and the use of tonometry in intestinal segments with a high bacterial activity should be interpreted with caution. We propose that serosal PCO2 levels >150-190 Torr (20-25 kPa) in the cecum of mice with a normal circulation may represent a state of gas supersaturation in the cecal wall.

Relationship between blood lactate and early hepatic dysfunction in acute circulatory failure

PURPOSE

The purpose of this study was to assess the influence of early hepatic dysfunction on lactate level in patients with acute circulatory failure in a retrospective study.

MATERIALS AND METHODS

Blood lactate was compared between patients in acute circulatory failure (systolic blood pressure < or = 80 mm Hg despite fluid challenge) with or without early hepatic dysfunction (bilirubin > 60 micromol/L or SGOT > 100 IU/L during the first 48 hours). Univariate and multivariate analysis were performed to assess the effects of early hepatic dysfunction and other clinical and biological data on serum lactate levels in patients with acute circulatory failure.

RESULTS

The study included 92 patients, mean age 64+/-15 years, mean simplified acute physiology score (SAPS) 18.4+/-4.1. Early hepatic dysfunction was identified in 29 patients (32%). Mean initial blood lactate was 5.54+/-4.78 mmol/L. Overall intensive care unit mortality was 67.3%. Although patients with and without hepatic dysfunction showed no significant difference in terms of mean SAPS, mean lowest systolic blood pressure, and mortality, serum lactate was higher in the group with hepatic dysfunction than in the group without hepatic dysfunction (8.24+/-6.49 mmol/L v4.29+/-3.09 mmol/L, P < .001). Factors independently associated with serum lactate were the existence of early hepatic dysfunction (P < .01), a nondistributive type of shock (P < .05), and the mean initial amount of epinephrine (P < .05).

CONCLUSIONS

This study suggests that early hepatic dysfunction plays an important role in serum lactate elevation in acute circulatory failure.

A randomized and controlled trial of the effect of treatment aimed at maximizing oxygen delivery in patients with severe sepsis or septic shock

OBJECTIVE

To evaluate the effects of increased oxygen delivery on mortality and morbidity.

DESIGN

Randomized, controlled trial.

SETTING

Medical-surgical ICU of a tertiary care hospital.

PATIENTS

Sixty-three patients classified according to predetermined criteria as having severe sepsis or septic shock.

INTERVENTIONS

The patients were randomly assigned to one of two groups: the control group (n = 32) received conventional therapy with a normal targeted value of oxygen delivery, and the treatment group (n = 31) received therapy with a targeted oxygen delivery index (DO2I) value of > 600 mL/min/m2. The therapeutic approach to maintain BP, arterial saturation, hemoglobin concentration, and pulmonary artery occlusion pressure was similar in both groups.

MEASUREMENTS AND MAIN RESULTS

The hemodynamic, oxygen transport, and gastric intramucosal pH measurements were recorded at the time of admission to the study and every 6 h for the next 96 h. The outcome measures were the rate of patient mortality and the number of organ dysfunctions occurring during the ICU stay. The study groups were similar with respect to demographics and admission hemodynamic variables, but the percentage of patients with positive blood cultures was significantly higher in the control group than in the treatment group, respectively: 34 vs 13% (p = 0.04). The average cardiac index was significantly higher in the treatment group than in the control group, respectively: 3.96 vs 3.05 L/min/m2 (p = 0.01). This factor did not significantly affect the DO2I. Nine of the 31 treatment group patients reached an average DO2I value of > 600 mL/min/m2. The rate of mortality in the control group patients up to the time of ICU discharge (66%) was similar to that seen in the treatment group (74%), respectively: 21 of 32 vs 23 of 31 (p = 0.46). The number of dysfunctional organs per patient was also similar in the control and treatment groups, respectively: 2.1+/-1.1 vs 2.6+/-1.2 (p = 0.12).

CONCLUSION

Treatment aimed at maximizing oxygen delivery in patients with severe sepsis or septic shock does not reduce mortality or morbidity.