Shock in the pediatric patient. Part II. Therapy

The management of sepsis

Management of sepsis in the pediatric patient is guideline driven. The treatment occurs in two phases, the first hour being the most crucial. Initial treatment consists of timely recognition of shock and interventions aimed at supporting cardiac output and oxygen delivery along with administration of antibiotics. The mainstay of treatment for this phase is fluid resuscitation. For patients in whom this intervention does not reverse the shock medications to support blood pressure should be started and respiratory support may be necessary. Differentiation between warm and cold shock and risk factors for adrenal insufficiency will guide further therapy. Beyond the first hour of treatment patients may require intensive care unit care where invasive monitoring may assist with further treatment options should shock not be reversed in the initial hour of care.

Hypovolemic shock complex: does the pancreatic perfusion increase or decrease at contrast-enhanced dynamic CT?

OBJECTIVE

The purpose of this study is to evaluate contrast enhancement effects of the pancreas at dynamic computed tomography (CT) to clarify whether pancreatic perfusion increases or decreases in severe trauma patients with hypovolemic shock.

METHODS

A total of 90 patients with (n=30) and without (n=60) blunt trauma and hypovolemic shock who underwent dynamic CT for abdomen was included. The measurement of CT attenuation values of the pancreas in the early phase and the late phase was performed to compare the contrast enhancement effects between patients with and without hypovolemic shock.

RESULTS

The mean CT attenuation values of the pancreas in the early phase of dynamic CT in patients with hypovolemic shock [95.4±29.1 Hounsfield units (HU)] were significantly lower (P < .001) than those in non-hypovolemic patients (136.6±17.9 HU), indicating decreased pancreatic perfusion in patients with hypovolemic shock. The mean CT attenuation values of the pancreas in the late phase of dynamic CT in patients with hypovolemic shock (95.9±17.6 HU) were significantly higher (P < .026) than those in non-hypovolemic patients (87.2±9.0 HU), indicating delayed or prolonged pancreatic enhancement in patients with hypovolemic shock.

CONCLUSIONS

Decreased pancreatic perfusion in the early phase and delayed pancreatic enhancement in the late phase of contrast-enhanced dynamic CT was a common finding in patients with hypovolemic shock.

The host response to sepsis and developmental impact

Invasion of the human by a pathogen necessitates an immune response to control and eradicate the microorganism. When this response is inadequately regulated, systemic manifestations can result in physiologic changes described as "sepsis." Recognition, diagnosis, and management of sepsis remain among the greatest challenges shared by the fields of neonatology and pediatric critical care medicine. Sepsis remains among the leading causes of death in both developed and underdeveloped countries and has an incidence that is predicted to increase each year. Despite these sobering statistics, promising therapies derived from preclinical models have universally failed to obviate the substantial mortality and morbidity associated with sepsis. Thus, there remains a need for well-designed epidemiologic and mechanistic studies of neonatal and pediatric sepsis to improve our understanding of the causes (both early and late) of deaths attributed to the syndrome. In reviewing the definitions and epidemiology, developmental influences, and regulation of the host response to sepsis, it is anticipated that an improved understanding of this host response will assist clinician-investigators in identifying improved therapeutic strategies.

Cardiovascular support in preterm infants

BACKGROUND

Despite increasing investigation in the area of cardiovascular instability in preterm infants, huge gaps in knowledge remain. None of the current treatments for hypotension, including the use of inotropic agents, have been well studied in the preterm population, and data regarding safety and efficacy are lacking. Thus, the labeling information regarding the use of inotropes as therapeutic agents in this population is inadequate.

OBJECTIVE

This article reviews the current deficiencies in knowledge with respect to measuring and achieving normal organ perfusion; summarizes the clinical, methodological, and ethical issues to consider when designing trials to evaluate medications for hemodynamic instability in the preterm neonate; and proposes 2 possible trial designs. Unanswered questions and potential obstacles for the systematic study of drugs to treat cardiovascular instability in preterm neonates are discussed.

METHODS

The neonatal Cardiology Group was established in 2003 by the US Food and Drug Administration (FDA) and the National Institute of Child Health and Human Development (NICHD) as part of the Newborn Drug Development Initiative. The Cardiology Group conducted a number of teleconferences and one meeting to develop a document addressing gaps in knowledge regarding cardiovascular drugs commonly used in low-birth-weight neonates and possible approaches to investigate these drugs. This work was presented at a workshop cosponsored by the NICHD and the FDA held in March 2004 in Baltimore, Maryland. Information for this article was gathered during this initiative.

RESULTS

To develop rational, evidence-based guidelines corroborated by robust scientific data for cardiovascular support in newborns, well-designed and adequately powered pharmacologic studies and clinical trials are needed to evaluate the safety and efficacy of inotropic agents and to determine the short- and long-term effects of these drugs. Trials investigating the currently available and novel therapies for cardiovascular instability in neonates will provide information that can be incorporated into product labeling and a scientific framework for cardiovascular management in critically ill neonates. The Cardiology Group identified and prioritized 2 conditions for investigation of therapeutic options for the management of neonatal cardiovascular instability: (1) cardiovascular instability in preterm neonates; and (2) cardiac dysfunction in neonates after cardiopulmonary bypass surgery. Key research questions in the area of cardiovascular instability in the preterm infant include determining optimal blood pressure (BP) in preterm infants; identifying better measures than BP to determine organ perfusion; optimizing hemodynamic treatments; and clarifying any associations between BP or therapy for low BP and mortality, intraventricular hemorrhage, periventricular leukomalacia, necrotizing enterocolitis, retinopathy of prematurity, and neurodevelopmental outcome. The Cardiology Group concluded that the study of inotropic agents in neonates using outcomes of importance to patients will require a complicated trial design to address the elements discussed. The group proposed 2 clinical trial designs: (1) a placebo-controlled trial with rescue therapy for symptomatic infants; and (2) a targeted BP trial.

CONCLUSION

This summary is intended to stimulate and assist future research in the area of cardiovascular support for preterm infants.

Bedside limited echocardiography by the emergency physician is accurate during evaluation of the critically ill patient

OBJECTIVE

Echocardiography can be a rapid, noninvasive, objective tool in the assessment of ventricular function and preload during resuscitation of a critically ill or injured child. We sought to determine the accuracy of bedside limited echocardiography by the emergency physician (BLEEP) in estimation of (1) left ventricular function (LVF) and (2) inferior vena cava (IVC) volume, as an indirect measure of preload.

METHODS

We conducted a prospective observational study of a convenience sample of patients who were admitted to our intensive care unit. All patients underwent BLEEP followed by an independent formal echocardiogram by an experienced pediatric echocardiography provider (PEP). IVC volume was assessed by measurement of the maximal diameter of the IVC. LVF was determined by calculating shortening fraction (SF) using M-mode measurements on the parasternal short-axis view at the level of the papillary muscle. An independent blinded pediatric cardiologist reviewed all images for accuracy and quality. Estimates of SF obtained on the BLEEP examination were compared with those obtained by the PEP.

RESULTS

Thirty-one patients were enrolled. The mean age was 5.1 years (range: 23 days-16 years); 48.4% (15 of 31) were girls; 58.1% (18 of 31) were on mechanical ventilatory support at the time of their study. There was good agreement between the emergency physician (EP) and the PEP for estimation of SF (r = 0.78). The mean difference in the estimate of SF between the providers was 4.4% (95% confidence interval: 1.6%-7.2%). This difference in estimate of SF was statistically significant. Similarly, there was good agreement between the EP and the PEP for estimation of IVC volume (r = 0.8). The mean difference in the estimate of IVC diameter by the PEP and the EP was 0.068 mm (95% confidence interval: -0.16 to 0.025 mm). This difference was not statistically significant.

CONCLUSIONS

Our study suggests that PEP sonographers are capable of obtaining images that permit accurate assessment of LVF and IVC volume. BLEEP can be performed with focused training and oversight by a pediatric cardiologist.

Posterior urethral valves presenting as abdominal distension and undifferentiated shock in a neonate: The role of screening emergency physician-directed bedside ultrasound

We present a case of shock in a 7-week-old neonate with obstructive uropathy secondary to posterior urethral valves (PUV). The antenatal ultrasound and the 2-week maintenance visit were unremarkable. A screening emergency physician directed bedside ultrasound (SEPUS) served to rapidly establish the diagnosis, initiate appropriate management, and facilitate early relief of urinary obstruction. We discuss the potential role of SEPUS in a critically ill neonate and briefly review the management of PUV.

Adrenaline for prevention of morbidity and mortality in preterm infants with cardiovascular compromise

BACKGROUND

Inotropes are widely used in preterm infants to treat cardiovascular compromise, which may result from early adaptive problems of the transitional circulation, perinatal asphyxia or sepsis. Sustained hypotension and poor organ blood flow are associated with brain injury including peri/intraventricular haemorrhage and subsequent poor neurodevelopmental outcomes. Adrenaline (epinephrine) infusions are used in preterm infants with clinical cardiovascular compromise.

OBJECTIVES

To determine the effectiveness and safety of adrenaline compared to no treatment or other inotropes in reducing mortality and morbidity in preterm infants with cardiovascular compromise.

SEARCH STRATEGY

Randomised controlled trials were identified by searching MEDLINE (1966-August 2003), The Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library, Issue 3, 2003) and EMBASE (1980 - 2003), supplemented with searches of reference lists of published trials and abstracts of conference proceedings.

SELECTION CRITERIA

Randomised controlled trials of preterm newborn infants that compared adrenaline to no treatment or other inotropic agents (including dopamine, dobutamine, noradrenaline or isoprenaline).

DATA COLLECTION AND ANALYSIS

Data were extracted and analysed independently by two reviewers. Treatment effects on the following outcomes were to be determined: mortality in the newborn period, long term neurodevelopmental outcomes, radiological evidence of brain injury, short term haemodynamic changes, adverse drug effects and short term neonatal outcomes. Study authors were contacted for additional information. Studies were analysed for methodological quality using the criteria of the Cochrane Neonatal Review Group.

MAIN RESULTS

One ongoing study (Pellicer 2003) was identified. One study comparing adrenaline with dopamine infusion was included but was published in abstract form only (Phillipos 1996). It enrolled hypotensive, predominantly preterm infants in the first 24 hours. Only infants >1750g are included in this review (report for infants <=1750g appears incomplete). The study was reported as being randomised and double blinded, but methods were not reported. Both adrenaline and dopamine significantly increased heart rate and mean BP, with no statistically significant effect on left or right ventricular outputs. No other clinical outcomes were reported. No studies were identified that compared adrenaline to other inotropes, placebo or no treatment.

REVIEWER'S CONCLUSIONS

There are insufficient data on the use of adrenaline infusions in preterm infants with cardiovascular compromise to make recommendations for practice. There is a need for larger trials to determine whether adrenaline is effective in reducing morbidity and mortality in preterm infants with cardiovascular compromise.

Blood pressure in the very low birth weight neonate

Few aspects of management of very low birth weight (VLBW; <1500 g) neonates have generated as much controversy as the assessment of blood pressure (BP) and need for treatment of perceived abnormalities of this physiologic variable. The approach to this problem may differ greatly among various institutions and even among clinicians within a given center. The purpose of this manuscript is to review available information regarding physiologic determinants and measurement of BP in VLBW neonates, normative data for BP, clinical factors that may affect BP in these at-risk neonates and studies in which presumed abnormalities of BP resulted in adverse clinical outcomes. Options for treatment of low BP in VLBW neonates also will be discussed.

Hemodynamic support in fluid-refractory pediatric septic shock

OBJECTIVE

Assess outcome in children treated with inotrope, vasopressor, and/or vasodilator therapy for reversal of fluid-refractory and persistent septic shock.

DESIGN

Survey; case series.

SETTING

Three pediatric hospitals.

PATIENTS

Fifty consecutive patients with fluid-refractory septic shock with a pulmonary artery catheter within 6 hours of resuscitation.

INTERVENTIONS

Patients were categorized according to hemodynamic state and use of inotrope, vasopressor, and/or vasodilator therapy to maintain cardiac index (CI) >3.3 L/min/m2 and systemic vascular resistance >800 dyne-sec/cm/m to reverse shock.

OUTCOME MEASURES

Hemodynamic state, response to class of cardiovascular therapy, and mortality.

RESULTS

After fluid resuscitation, 58% of the children had a low CI and responded to inotropic therapy with or without a vasodilator (group I), 20% had a high CI and low systemic vascular resistance and responded to vasopressor therapy alone (group II), and 22% had both vascular and cardiac dysfunction and responded to combined vasopressor and inotropic therapy (group III). Shock persisted in 36% of the children. Of the children in group I, 50% needed the addition of a vasodilator, and in group II, 50% of children needed the addition of an inotrope for evolving myocardial dysfunction. Four children showed a complete change in hemodynamic state and responded to a switch from inotrope to vasopressor therapy or vice versa. The overall 28-day survival rate was 80% (group I, 72%; group II, 90%; group III, 91%).

CONCLUSIONS

Unlike adults, children with fluid-refractory shock are frequently hypodynamic and respond to inotrope and vasodilator therapy. Because hemodynamic states are heterogeneous and change with time, an incorrect cardiovascular therapeutic regimen should be suspected in any child with persistent shock. Outcome can be improved compared with historical literature.

Hemodynamic effects of i.v. milrinone lactate in pediatric patients with septic shock. A prospective, double-blinded, randomized, placebo-controlled, interventional study

STUDY OBJECTIVE

To determine the hemodynamic effects of i.v. milrinone lactate in pediatric patients with nonhyperdynamic septic shock. Specifically we tested the hypothesis that i.v. milrinone would increase cardiac index by 20% and decrease systemic vascular resistance index by 20% during a 2-h study period.

DESIGN

Prospective, double-blinded, randomized, placebo-controlled, descriptive, interventional study.

SETTING

Twenty-six-bed pediatric ICU at Children's Medical Center of Dallas and a 10-bed pediatric trauma ICU at Parkland Memorial Hospital.

PATIENTS/PARTICIPANTS

Twelve patients (age range, 9 months to 15 years) with nonhyperdynamic septic shock despite administration of catecholamines (cardiac index [CI] normal [3.5 to 5.5 L/min/m2] or low [< or =3.5 L/min/m2]; systemic vascular resistance index [SVRI] normal [800 to 1,600 dyne.s.cm5/m2] or high [> or =1,600 dyne.s.cm5/m2]; and pulmonary capillary wedge pressure [PCWP] normal [8 to 12 mm Hg] or higher) with clinical signs of poor perfusion were enrolled, randomized, and treated in a blinded fashion with i.v. milrinone and placebo.

INTERVENTIONS

Patients were randomized into two groups. Group A received a loading dose of 50 micrograms/kg i.v. of milrinone followed by a continuous i.v. infusion of 0.5 microgram/kg/min while group B received an equal volume loading dose and continuous infusion of placebo. After 2 h, group A received an equal-volume loading dose followed by a continuous infusion of placebo while the milrinone infusion continued, while group B received a 50 micrograms/kg loading dose of milrinone followed by a continuous infusion of 0.5 microgram/kg/min while the placebo infusion remained. Outcome variable were measured at baseline, 0.5, 1.0, 2.0, 2.5, 3.0, and 4.0 h. Echocardiographic measurements were taken at baseline, hour 2, and hour 4 in all subjects. No changes in other inotropic or mechanical ventilatory support were allowed during the study period.

MEASUREMENTS AND MAIN RESULTS

Milrinone significantly increased CI, stroke volume index (SVI), right and left ventricular stroke work index, and oxygen delivery (Do2) at 0.5, 1.0, and 2.0 h postloading dose (p < 0.05) while significantly decreasing SVRI, pulmonary vascular resistance index, and mean pulmonary arterial pressure at 0.5, 1.0, and 2.0 h postloading dose (p < 0.05). No clinically or statistically significant changes in heart rate, systolic and diastolic BP, mean systemic arterial pressure, or PCWP were observed during milrinone treatment compared to placebo.

CONCLUSIONS

CI, SVI, and Do2 significantly increased while SVRI significantly decreased when compared to placebo after i.v. administration of milrinone to pediatric patients with nonhyperdynamic septic shock. No adverse effects were observed. In a volume-resuscitated pediatric patient with septic shock, when administered in addition to catecholamines, milrinone will improve cardiovascular function.

Randomized, blind trial of dopamine versus dobutamine for treatment of hypotension in preterm infants with respiratory distress syndrome

To compare the efficacy of dopamine and dobutamine for the treatment of hypotension (mean arterial blood pressure, < or = 30 mm Hg) in preterm (< or = 34 weeks of gestation) infants with respiratory distress syndrome in the first 24 hours of life, we enrolled 63 hypotensive preterm infants in a randomized, blind trial. Inclusion criteria required an arterial catheter for measurement of mean arterial blood pressure, treatment with exogenous surfactant, and persistent hypotension after volume expansion with 20 ml/kg (packed erythrocytes if hematocrit < 0.40, 5% albumin if > or = 0.40). Intravenous study drug infusions were initiated at 5 micrograms/kg per minute and then increased in increments of 5 micrograms/kg per minute at 20-minute intervals until a mean arterial blood pressure > 30 mm Hg was attained and sustained for > or = 30 minutes (success) or a maximum rate of 20 micrograms/kg per minute was reached without resolution of hypotension (failure). The study groups at entry were comparable for birth weight, gestational age, postnatal age, gender, birth depression, hematocrit < 0.40, heart rate, oxygenation index, delivery route, maternal chorioamnionitis, and maternal magnesium or ritodrine therapy. No infants in the dopamine group had a treatment failure (0/31; 0%); (16%) of 32 infants failed to respond to dobutamine (p = 0.028). Success was attained at < or = 10 micrograms/kg per minute in 30 (97%) of 31 infants given dopamine and in 22 (69%) of 32 infants given dobutamine (p < 0.01). Among those treated successfully, the increase in mean arterial blood pressure was significantly higher in those given dopamine (mean, 11.3 vs 6.8 mm Hg; p = 0.003). We conclude that dopamine is more effective than dobutamine for the early treatment of hypotension in preterm infants with respiratory distress syndrome.

Cardiogenic shock in the neonate

The neonate with circulatory failure and cardiogenic shock is a difficult management problem. However, the initial approach is that of resuscitation with exact diagnosis of secondary concern. Once the infant has been stabilized and septic and hypovolemic shock have been excluded, attention should be directed to the four most likely causes of cardiogenic shock: structural heart disease with left heart obstruction being the most common, cardiac muscle disorders, cardiac dysrhythmias, and cardiac metabolic disorders.

Fluid resuscitation of acute hypovolemic hypoperfusion states in pediatrics

Multiorgan hypoperfusion due to a loss of effective circulating blood volume, whether a consequence of hemorrhage or dehydration, constitutes a medical emergency. Fluid must be added rapidly to the circulatory system, in the form of blood, colloid, or crystalloid solution. The type of fluid used for volume expansion depends on the nature of the losses. The aim of treatment is to expand effective circulating blood volume and to restore nutrient delivery and gas exchange at the cellular level.

Group B streptococcal sepsis in the piglet: effects of fluid therapy on venous return, organ edema, and organ blood flow

We investigated the physiologic effects of normal saline versus 5% albuminated saline fluid resuscitation on 10-12-day-old piglets infected with group B streptococci for four hours. After intravenously receiving 1 X 10(10) bacteria/kg over 45 minutes, one group was untreated while the two fluid-treated groups received enough intravenous fluid to maintain the baseline cardiac output. An increase in the resistance to venous blood return was the major limitation to cardiac output. The resistance nearly quadrupled in the untreated piglets as shown by a 50% decrease in cardiac output with a nearly doubling of the driving pressure for venous return (mean circulatory pressure was normal and atrial pressures decreased by 70%). In both fluid-treated groups, resistance doubled as shown by an unchanged cardiac output with a doubling of the driving pressure (mean circulatory pressure increased by 50%) and atrial pressures remained at baseline). Blood volume was 9% below control in the untreated group and 13% above control in both fluid-treated groups. Much more crystalloid (155 ml/kg) than colloid (58 ml/kg) was necessary to maintain baseline cardiac output; this resulted in a 36% decrease in the plasma protein oncotic pressure of the former group and a 15% increase in the oncotic pressure of the latter group. Organ edema formation (ileum, pancreas, kidney, adrenal gland, lung) occurred only in the saline-treated animals. We conclude that increased resistance to venous return was the primary cause of shock in our model and that this can be effectively treated by giving enough intravenous fluid to elevate the mean circulatory pressure. However, if the plasma protein oncotic pressure is also lowered (saline group), organ edema results.

Trauma in infancy and childhood: initial evaluation and management

Successful management of the critically injured multiple trauma patient frequently depends on the expertise of the first physician contracted. Thus, this article outlines a systematic approach to the assessment and resuscitation of pediatric trauma victims.

Therapeutic approach to the failing heart

Currently recommended dosages for the more commonly prescribed drugs discussed above are given in Table 3. The approach to the failing heart in the pediatric patient requires an understanding of the pathophysiology of heart failure and an understanding of the mechanisms, effects and clinical pharmacology of several classes of therapeutic agents. The pediatric patient differs in many respects from his adult counterpart in the manifestations of heart failure and in his response to drug therapy to treat heart failure.

Pulmonary microthrombi syndrome in newborn infants with unresponsive persistent pulmonary hypertension

Some newborn infants with either primary or secondary persistent pulmonary hypertension (PPHN) remain hypoxemic, hypercarbic, and acidotic despite therapeutic efforts. In autopsies of 23 infants who had PPHN, diffuse platelet-fibrin thrombi were present in the pulmonary microcirculation of eight (15.2 +/- 18.1 thrombi/cm2 lung tissue) and absent in 15 (0.2 +/- 0.3 thrombi/cm2 lung tissue), (P less than 0.004). Diagnoses in group A (thrombi) were pneumonia and sepsis (four patients), meconium inhalation (3), and primary PPHN (1); and in group B (no thrombi) pneumonia and sepsis (4), meconium inhalation (4), primary PPHN (4), hyaline membrane disease (2), and diaphragmatic hernia (1). The only significant differences between the two groups were the response to tolazoline infusion as assessed by changes in partial pressure of arterial oxygen (PaO2) and the platelet counts. Group A responded less favorably to tolazoline (14.8 mm Hg vs 83.6 mm Hg; P less than 0.05) and had lower platelet counts (51,000/microliter vs 128,000/microliter) (P less than 0.01) than group B. No significant differences could be detected in Apgar scores, duration or mode of mechanical ventilation, oxygen requirements, arterial blood gas tensions or pH, systemic arterial blood pressure, coagulation profile, amount of blood product transfusions, or intravascular catheter use. Pulmonary microthrombi should be added to the list of mechanisms for PPHN and may explain why some infants do not respond well to therapeutic efforts aimed at vasodilation. Thrombocytopenia and failure to respond to pulmonary vasodilators might suggest the diagnosis.