Prognostic value of gastric intramucosal pH in critically ill children

Functional testing in the diagnosis of chronic mesenteric ischemia

Chronic mesenteric ischemia (CMI) results from insufficient oxygen delivery or utilization to meet metabolic demand. Two main mechanisms may lead to mesenteric ischemia: occlusion in the arteries or veins of the gastrointestinal tract, or reduced blood flow from shock states or increased intra-abdominal pressure, so-called non-occlusive mesenteric ischemia. Severe stenoses in the three main mesenteric vessels as demonstrated with CT-angiography or MR-angiography are sufficient to proof mesenteric ischemia, for example in patients who present with weight loss, postprandial pain and diarrhea. Still in many clinical situations mesenteric ischemia is only one of many possible explanations. Especially in patients with a single vessel stenosis in the celiac artery or superior mesenteric artery with postprandial pain, mesenteric ischemia remains a diagnosis of probability or assumption without functional proof of actual ischemia. This review is aimed to provide an overview of all past, present and future ways to functionally proof CMI.

Physiological impact of pneumoperitoneum on gastric mucosal CO2 pressure during laparoscopic versus open appendectomy in children

INTRODUCTION

Funded knowledge about the physiological impact of laparoscopic surgery in children is sparse. Although there are data on hemodynamic compromise after creation of a pneumoperitoneum in children, little is known about microcirculatory changes at the mucosa level. Therefore, the aim of this study was to assess gastric microcirculation by continuous gastric air tonometry in the setting of laparoscopic versus open appendectomy.

PATIENTS AND METHODS

Twenty children 5-17 years old undergoing laparoscopic and 7 children undergoing open appendectomy were included in the study. Gastric intramucosal CO(2) pressure (pCO(2)i) was measured under standardized flow and intraperitoneal pressure using continuous air tonometry (TONOCAP(®), Datex Ohmeda), and ΔpCO(2) (pCO(2)i - end-expiratory CO(2) pressure [pCO(2)e]) was obtained for the time course of surgery.

RESULTS

ΔpCO(2) increased significantly from the baseline value not only in the laparoscopic group but also in the open surgery group. Even though ΔpCO(2) was higher in the laparoscopic group at all time points, the overall increase in ΔpCO(2) for both groups was uniform. The largest differences were observed during the initial 20 minutes of the operation. The changes observed were exclusively due to an increase of pCO(2)i in relation to a constant pCO(2)e.

DISCUSSION

In the setting of a standardized, simple operation in an otherwise healthy child above the age of 5 years, our data suggest that the effect of a pneumoperitoneum on splanchnic perfusion is comparable to the compromise caused by open surgery. Further research must be obtained when evaluating the full impact of laparoscopy in children.

Gastric Tonometry as a Prognostic Index of Mortality in Sepsis

BACKGROUND

Splanchnic hypoperfusion in sepsis leads to translocation of bacteria from gut and development of multi-organ dysfunction syndrome (MODS), with increased mortality in critically ill patients. Gastric tonometry can detect this hypoperfusion by measuring carbon dioxide tension (PgCO2) and intramucosal pH (pHi) from gastric mucosa. Therapeutic intervention aimed at improving gut perfusion can improve the outcome and prognosticate the mortality in sepsis patients.

METHODS

100 patients with clinical diagnosis of sepsis were included and divided into two groups of 50 each. Group A patients were managed traditionally without gastric tonometry and in Group B gastric tonometry was used for therapeutic intervention. The intramucosal PCO2, pHi, end tidal carbon dioxide tension (EtCO2) and (PgCO2-EtCO2) differences were monitored at 0, 12 and 24 hours interval.

RESULT

Overall mortality in Group A was 64 % and 54 % in Group B. In Group B 45% patients developed MODS and 54 % died with low pHi. As an index of mortality low pHi had a sensitivity of 70% and specificity of 65%.

CONCLUSION

There is a good correlation between mortality prediction on the basis of pHi and PgCO2-EtCO2 difference and actual mortality in critically ill patients. The gastric tonometer should be used to predict mortality and guide resuscitation in septicemia.

Hemodynamic, respiratory, and perfusion parameters during asphyxia, resuscitation, and post-resuscitation in a pediatric model of cardiac arrest

PURPOSE

To analyze the evolution of hemodynamic, respiratory, and tissue perfusion parameters in an infant animal model of asphyxial cardiac arrest (CA).

METHODS

This was a secondary analysis of a prospective observational study conducted at a laboratory research department of a university hospital. Seventy-one, 2-month-old piglets were studied. CA was induced by removal of mechanical ventilation. Cardiopulmonary resuscitation (CPR) was performed by means of manual external chest compressions, mechanical ventilation, epinephrine and/or terlipressin intravenous administration.

RESULTS

The evolution of hemodynamic (heart rate, blood pressure, cardiac index), respiratory (end-tidal CO(2), blood gas analysis), and tissue perfusion (intramucosal gastric pH, central, cerebral, and renal hemoglobin saturation) parameters was analyzed during three periods: asphyxia, CPR, and after return of spontaneous circulation (ROSC). During asphyxia, a severe arterial and tissue hypoxia with hypercapnia and lactic acidosis quickly developed. Bradycardia, hypotension, and increasing of systemic vascular resistances and pulmonary arterial pressure were also observed. During CPR, arterial, cerebral, and tissue oxygenation were low in spite of ventilation with oxygen 100%. After ROSC a rapid restoration of hemodynamic and respiratory parameters was observed. However, 30 min after ROSC, lactic acidosis and low intramucosal gastric pH persisted.

CONCLUSIONS

Asphyxia leads to sudden hypoxia and hypercapnia with tissue hypoxia and progressive bradycardia. Standard CPR is not able to maintain an adequate tissue oxygenation during CPR in this animal model. When ROSC is achieved, a rapid restoration of the normal values of general hemodynamic and respiratory parameters is observed, although lactic acidosis and splanchnic hypoperfusion persist in time.

The pediatric multiple organ dysfunction syndrome

OBJECTIVES

To review the epidemiology of pediatric multiple organ dysfunction syndrome (MODS) and summarize current concepts regarding the pathophysiology of shock, organ dysfunction, and nosocomial infections in this population.

DATA SOURCE

A MEDLINE-based literature search using the keywords MODS and child, without any restriction to the idiom.

MAIN RESULTS

Critically ill children may frequently develop multisystemic manifestations during the course of severe infections, multiple trauma, surgery for congenital heart defects, or transplantations. Descriptive scores to estimate the severity of pediatric MODS have been validated. Young age and chronic health conditions have also been recognized as important contributors to the development of MODS. Unbalanced inflammatory processes and activation of coagulation may lead to the development of capillary leak and acute respiratory distress syndrome. Neuroendocrine and metabolic responses may result in insufficient adaptive immune response and the development of nosocomial infections, which may further threaten host homeostasis.

CONCLUSIONS

Over the last 20 yrs, there has been an increasing knowledge on the epidemiology of pediatric MODS and on the physiologic mechanisms involved in the genesis of organ dysfunction. Nevertheless, further studies are needed to more clearly evaluate what is the long-term outcome of pediatric MODS.

Sepsis: Prognostic Role of Apoptosis Regulators in Gastrointestinal Cells

BACKGROUND

Intestinal epithelial cell apoptosis has been reported in sepsis as a mechanism of organ failure. The aim of this study was to clarify the role of apoptosis-regulating proteins (bcl-2, bax, cytochrome-c, and caspase-8) in septic rats by studying their expression in gastric and intestinal epithelial cells.

METHODS

Adult Wistar rats were subjected to the cecal ligation and puncture (CLP) model of sepsis and randomly divided into two study groups. Sixty-two animals were sacrificed 6, 12, 24, 36, 48, and 60 h post-procedure, and 50 animals served as the survival study group. Sham-operated animals (n = 40) were used as controls. Gastric and intestinal tissue was excised, and immunohistochemical detection of bcl-2, bax, cytochrome-c, and caspase-8 protein expression was performed.

RESULTS

In gastric mucosa, sepsis induced upregulation of bax and downregulation of caspase-8 expression (p = 0.053 and p = 0.05, respectively). Both bax and caspase-8 were upregulated as early as 6 h post CLP and progressively decreased (p = 0.001, p = 0.004 respectively). In contrast, the expression of the anti-apoptotic bcl-2 was upregulated progressively during the sepsis syndrome (p = 0.03). In intestine, sepsis induced a fourfold upregulation of the cytoprotective bcl-2 (p = 0.0001), accompanied by a remarkable increase in bax (p = 0.002) and caspase-8 (p = 0.0001) expression and a decrease in cytochrome-c expression (p = 0.02). The time distribution of the apoptosis regulators followed the same pattern as in gastric tissue, showing an upregulation of the proapoptotic bax and cytochrome c (p = 0.04) during the early phases and a progressively increased expression of bcl-2 during the late phases (p = 0.0001). Bax expression in gastric epithelium of subjects with septic syndrome was detrimental to survival (p = 0.0001), whereas the expression of the cytoprotective bcl-2 in intestinal epithelium appeared to favor a good prognosis (p = 0.0001).

CONCLUSIONS

Sepsis results in alterations of apoptosis regulators in gastrointestinal cells. Alterations of bax and bcl-2 expression in gastric and intestinal epithelial cells may predict the outcome in septic rats.

Arch reconstruction without circulatory arrest: scientific basis for continued use and application to patients with arch anomalies

Aortic arch hypoplasia is a common constituent of congenital heart disease. While repair of these lesions has been performed routinely during deep hypothermia and circulatory arrest, new approaches are emerging. One such approach, regional low-flow perfusion, will be described here. This technique exploits the anticipated modified Blalock-Taussig shunt as a perfusion conduit. With control of the brachiocephalic vessels and the descending thoracic aorta, circulatory support can be provided to the neonate with exposure identical to that obtained by circulatory arrest. While first applied to children undergoing the Norwood operation for hypoplastic left heart syndrome, this technique has recently been applied to children requiring complex arch surgery in the setting of biventricular repair. To date, 36 neonates requiring arch reconstruction (27 Norwood operations, 9 biventricular repairs) have been supported with regional low-flow perfusion. Thirty-day and hospital discharge survival has been 74% (20/27) for neonates undergoing Norwood operation, and 88% (8/9) for those undergoing biventricular repair. We will review the operative technique, methodologies, and clinical studies that led us to conclude that regional low-flow perfusion provides cerebral, as well as somatic, circulatory support to the neonate undergoing arch reconstruction.

Effects of feeding on gastric tonometric measurements in critically ill children

OBJECTIVE

To determine the effect of gastric feeding on the measurement of gastric intramucosal PCO2 (PiCO2) and its derived gastric intramucosal PCO2-arterial PCO2 difference (PiCO2-PaCO2 difference) and gastric intramucosal pH (pHi) in a group of critically ill children using recirculating gas tonometry.

DESIGN

Prospective clinical pilot study.

SETTING

Sixteen bed pediatric intensive care unit.

PATIENTS

Ten mechanically ventilated and hemodynamically stable children (median age, 20.1 months [interquartile range (IQR), 9.7-47.6 months] and median weight, 10.2 kg [IQR, 10-16.5 kg]).

INTERVENTIONS

A 7-French recirculating gas tonometer was placed in the stomach via the orogastric route.

MEASUREMENTS

In each patient, baseline fasted/unfed PiCO2, PiCO2-PaCO2 difference, and pHi were determined hourly over a 5-hr period. Gastric feeding was then reestablished (3 mL/kg/hr) within a median time of 3 hrs and a further 5 hourly measurements were determined. Concurrent arterial blood gas and lactate measurements were taken. Blood pressure and heart rate was monitored throughout.

MAIN RESULTS

Hemodynamic parameters remained stable throughout the study period. When compared with the unfed/fasting state, PiCO2 measurements and PiCO2-PaCO2 difference were consistently lower and pHi values higher than when the patients were fed (two-way analysis of variance for repeated measures: all p <.001 between groups). Measurements did not vary over time.

CONCLUSIONS

In our patient group, gastric feeding decreased the PiCO2 and PiCO2-PaCO2 difference and increased pHi compared with the unfed state. These findings are in contrast to those found in adult studies.

Clinical practice parameters for hemodynamic support of pediatric and neonatal patients in septic shock

BACKGROUND

The Institute of Medicine has called for the development of clinical guidelines and practice parameters to develop "best practice" and potentially improve patient outcome.

OBJECTIVE

To provide American College of Critical Care Medicine clinical guidelines for hemodynamic support of neonates and children with septic shock.

SETTING

Individual members of the Society of Critical Care Medicine with special interest in neonatal and pediatric septic shock were identified from literature review and general solicitation at Society of Critical Care Medicine Educational and Scientific Symposia (1998-2001).

METHODS

The MEDLINE literature database was searched with the following age-specific keywords: sepsis, septicemia, septic shock, endotoxemia, persistent pulmonary hypertension, nitric oxide, and extracorporeal membrane oxygenation. More than 30 experts graded literature and drafted specific recommendations by using a modified Delphi method. More than 30 more experts then reviewed the compiled recommendations. The task-force chairman modified the document until <10% of experts disagreed with the recommendations.

RESULTS

Only four randomized controlled trials in children with septic shock could be identified. None of these randomized trials led to a change in practice. Clinical practice has been based, for the most part, on physiologic experiments, case series, and cohort studies. Despite relatively low American College of Critical Care Medicine-graded evidence in the pediatric literature, outcomes in children have improved from 97% mortality in the 1960s to 60% in the 1980s and 9% mortality in 1999. U.S. hospital survival was three-fold better in children compared with adults (9% vs. 27% mortality) in 1999. Shock pathophysiology and response to therapies is age specific. For example, cardiac failure is a predominant cause of death in neonates and children, but vascular failure is a predominant cause of death in adults. Inotropes, vasodilators (children), inhaled nitric oxide (neonates), and extracorporeal membrane oxygenation can be more important contributors to survival in the pediatric populations, whereas vasopressors can be more important contributors to adult survival.

CONCLUSION

American College of Critical Care Medicine adult guidelines for hemodynamic support of septic shock have little application to the management of pediatric or neonatal septic shock. Studies are required to determine whether American College of Critical Care Medicine guidelines for hemodynamic support of pediatric and neonatal septic shock will be implemented and associated with improved outcome.

Measuring intramucosal pH in very low birth weight infants

Maintenance of adequate perfusion is essential for health of the intestinal mucosa. Methods available to assess intestinal perfusion provide information on mesenteric blood flow, which may differ from mucosal flow. Intramucosal pH (pH(i)) is influenced by tissue oxygenation and perfusion. Gastric pH(i) can be measured using the technique of tonometry. A prospective observational clinical study was performed to examine relationships between measured gastric pH(i) and mucosal CO(2) (mCO(2)), and acid-base balance, gastrointestinal complications (necrotizing enterocolitis and perforation), and death in infants <1500 g birth weight. A nasogastric tonometry catheter (size 5F) was inserted into the stomach of infants, and pH(i) was calculated from mCO(2) levels measured using saline tonometry. Measurements were performed at 3, 12, 24, and 48 h, then daily until arterial access was unavailable. Two hundred eleven sets of measurements were performed on 38 infants [birth weight (mean +/-SD), 863 +/- 241 g; gestation, 26.5 +/- 1.8 wk; and median Clinical Risk Index for Babies score, 8.0 (interquartile range, 5.0-10.75)]. Mean pH(i) was 7.27 (95% confidence interval, 7.26-7.28) and mean mCO(2) was 47.0 mm Hg (95% confidence interval, 45.7-48.3 mm Hg). pH(i) and mCO(2) correlated significantly with arterial pH (pH(a)), arterial PCO(2) (PaCO(2)), and arterial base excess. There were no significant relationships between pH(a) and pH gap (pH(a)-pH(i)) or CO(2) gap (mCO(2)-PaCO(2)). Recurrent low pH(i) (<7.2 on more than one occasion) and an mCO(2)/PaCO(2) ratio of > or =1.29 were significantly associated with an increase in gastrointestinal complications. There were no statistically significant associations with death. In conclusion, changes in pH gap and CO(2) gap can occur without alteration in pH(a). Abnormalities in pH(i) might predict gastrointestinal complications in infants <1500 g.

Noninvasive monitoring in the pediatric intensive care unit

The best ICU monitors are physicians and nurses, who integrate all of the physiologic parameters of patients with the known pathophysiology of the disease process. Over-reliance on raw electronic data, with their inherent errors, jeopardizes the safe and efficient care of patients. Data must be interpreted in the context of the history, repetitive physical examinations, response to therapy, and a background of experience. New modalities and the application of artificial intelligence may facilitate the interpretation of data, but the role of the bedside medical practitioner remains as the heart of pediatric critical care.

Septic shock

Infection is problematic because it affects many patients (adults and children), is a major cause of death in intensive care units (ICU) worldwide, and uses a large amount of hospital resources. The mortality rate among patients with septic shock varies but approximates 40% in infected patients admitted to ICUs. Because of the large number of adults dying of sepsis, many resources are expended. Children are physiologically different from adults, but nonetheless, many similarities exist with respect to the response to septic shock.

Intragastric pH in critically ill neonatal foals and the effect of ranitidine

OBJECTIVE

To characterize intragastric pH profiles in critically ill foals and determine whether administration of ranitidine altered pH profiles.

DESIGN

Prospective observational study.

ANIMALS

23 hospitalized neonatal foals < or = 4 days of age.

PROCEDURE

Intragastric pH was measured continuously for up to 24 hours by use of an indwelling electrode and continuous data recording system. In 21 foals, ranitidine was administered IV.

RESULTS

10 foals had predominantly or exclusively alkaline profiles, 10 had profiles typical of those reported for healthy foals, with periods of acidity (hourly mean pH < 5.0 at least once), and 3 had atypical profiles with periods of acidity. All 10 foals that had intragastric pH profiles typical of healthy foals survived, whereas only 2 foals with alkaline profiles survived, and none of the foals with atypical profiles survived. The effects of ranitidine administration could not be assessed in 13 foals because of a high baseline intragastric pH. In 7 of the remaining 9, ranitidine administration resulted in an alkalinizing response, but this response was often of blunted duration. Ranitidine administration did not appear to alter the intragastric pH profile in the remaining 2 foals.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggested that hospitalized critically ill foals often have intragastric pH profiles different from those reported for healthy foals and may respond differently to ranitidine administration than do healthy foals. Many critically ill foals have continuously alkaline intragastric pH profiles, questioning the need for prophylactic administration of ranitidine in all critically ill foals.

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.

Gastric tonometry in patients with cardiogenic shock and intra-aortic balloon counterpulsation

OBJECTIVE

To study the course of gastric regional PCO2 (PrCO2) in patients with cardiogenic shock requiring intra-aortic balloon (IAB) counterpulsation and the prognostic value of PrCO2 in this patient population.

DESIGN

A prospective, observational clinical study.

SETTING

Medical intensive care unit in a university hospital.

PATIENTS

Twenty-six consecutive patients with cardiogenic shock requiring mechanical support with an IAB counterpulsation undergoing mechanical ventilation

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULT

Hemodynamic variables, tonometric variables, arterial blood gases, and arterial lactate were assessed before insertion of IAB (baseline), and 1, 2, 3, 8, 16, 24, and 48 hrs thereafter. A subset of these patients (n = 14) were studied just before and 1, 8, 24, and 32 hrs after IAB removal; 12/26 patients (46.2%) died. Cardiac index increased from baseline to 1 hr after insertion of IAB (1.7 +/- 0.3 to 2.6 +/- 0.8 L/min/m2, p < .05). PrCO2 did not change between admission (47 +/- 13 torr [6.3 +/- 1.7 kPa]) and 8 hrs after placement of IAB but increased to 63 +/- 22 torr (8.4 +/- 2.9 kPa) at 16 hrs (p < .05) without any further alteration until 48 hrs. CO2 gap showed a similar pattern with 15 +/- 11 torr (2.0 +/- 1.5 kPa) at baseline and an increase to 28 +/- 22 torr (3.7 +/- 2.9 kPa) 16 hrs later. PrCO2 and CO2 gap remained at high levels (59 +/- 11 torr [7.7 +/- 1.5 kPa] and 22 +/- 10 torr [2.9 +/- 1.3 kPa], respectively), before IAB removal without further improvement or deterioration thereafter. PrCO2 values showed no difference between survivors and nonsurvivors at any time point.

CONCLUSION

Patients with cardiogenic shock developed high PrCO2 within the first 24 hrs, which reflects gastric mucosal ischemia. Persistently high levels of PrCO2 were indicative for prolonged hypoperfusion of the gut. Gastric tonometry failed to discriminate between survivors and nonsurvivors.