Page 1485 - Hall et al (2015) Principles of Critical Care-McGraw-Hill

1024 PART 9: Gastrointestinal Disorders

without changing intracranial pressure (ICP); norepinephrine increased ACUTE LIVER FAILURE AND COAGULATION
CPP, but also showed a statistically significant, but small increase in ICP. 18
Although the majority of patients will have a hyperdynamic circula- The incidence of kidney failure is high in ALF (especially acetamino-
tion, a proportion of those with hypoxic hepatitis (cardiac and respira- phen induced due to direct tubular toxicity). Kidney failure, although a
tory in etiology) are likely to have evidence of both right- and left-sided component of prognostic scoring systems, is not a risk factor for mortal-
dysfunction with or without valvular heart disease. In this setting, ity when viewed in isolation; however, when found in association with
optimization of cardiac function will need to be individualized with high-grade encephalopathy (III/IV) and profound coagulopathy, pro-
regard to volume status and inotropic needs. As stated above, right-sided gnosis is very poor. Those with kidney failure who survive from acute
pressures should be minimized to facilitate optimal hepatic venous liver failure have been shown to have good recovery with restoration of
drainage alongside effective left ventricular output. normal GFR.
Whether there is benefit to giving physiological doses of hydrocortisone Management of prerenal failure should be as in any critically ill patient,
to those patients with vasopressor resistant shock is not clear. There are with consideration being given to intra-abdominal hypertension in those
no mortality studies addressing this, although, using a standard ACTH with ascites. Renal replacement therapy is likely to be beneficial if insti-
stimulation test, some studies have reported evidence of >50% adrenal tuted earlier in the clinical course in patients with ALF to allow optimal
dysfunction. There is one study suggesting that use of steroids decreases management of fluid balance and metabolic disarray. Utilization of early
vasopressor requirements and prolongs time to death or perhaps in this renal replacement therapy is also likely to allow modulation of ammonia
patient cohort, time to obtain a suitable liver for transplantation. 19 levels and mitigate against risk of cerebral edema.
An elevated troponin has been shown to be predictive of poor outcomes Continuous forms of renal replacement therapy are preferred to
in a study from the USA ALF group, although a subsequent study did not allow more precise modulation of the various physiological parameters.
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repeat this finding. It is thought that troponin elevations reflect myocyte Interestingly, coagulation abnormalities in patients with ALF have been
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stress in the setting of metabolic disarray and multiple organ failure. shown to have shorter filter life span when in receipt of renal replace-
If volume loading does not result in resolution of lactic acidosis, early ment therapy than a comparison group of critically ill hematology
referral to a tertiary center should be undertaken. Failure of volume to patients. ALF patients have balanced a state of coagulation with, in
resolve hypotension will require use of vasoactive drugs such as norepi- a significant proportion, a tendency to a prothrombotic state. Renal
nephrine. It should be recognized that grossly elevated levels of acetamin- replacement therapy circuits are normally anticoagulated with epopros-
ophen without evidence of acute liver failure may result in transient, but tenol or low dose heparin. Recently, there has been increased interest in
significant, lactate elevation from temporary mitochondrial standstill. the use of citrate as an anticoagulant, and in the majority of patients with
This does not carry the prognostic significance of later lactic acidosis. cirrhosis this appears safe and effective. Data in ALF are scant, although
■ RESPIRATORY MANAGEMENT some publications suggest that those with elevated lactates and pro-
thrombin times, accumulation of citrate is likely. Patients with ALF who
Encephalopathic patients are often unable to protect their airway and have reduced fibrinogen and platelets are at increased risk of bleeding.
will require endotracheal intubation to address this problem. Primary Assessment of coagulation may be facilitated by use of thromboelasto-
respiratory failure as a complication of acute liver failure is relatively rare graphic techniques, in addition to standard laboratory parameters.
endotracheal intubation for airway protection only may be managed with ■ SEPSIS
in the early phase of acute liver failure. Accordingly, patients who require
minimal pressure support/CPAP ventilator settings or even a T-piece. Patients with ALF are thought to be at increased risk of sepsis; this is
Acute hypercarbia may not be well tolerated in those patients with cerebral attributed to their functional immunosuppression, altered monocyte and
edema who are at risk of elevated ICP. Ventilatory strategies should account neutrophil function, and loss of complement. Earlier studies reported
for this and allow normocarbia during the period of risk. The incidence of that the incidence of sepsis approaches 80%, with an increased risk of
ARDS/acute lung injury is relatively rare in patients with ALF and does gram-positive organisms. More recently, the work of Karvellas et al
not appear to contribute to mortality. Those patients who develop ARDS showed that bacteremia was not observed until approximately day 10 into
should be managed with a low tidal volume lung protective strategy. the critical care course, with an equal representation of gram-positive
■ GASTROINTESTINAL MANAGEMENT and gram-negative organisms ; however, in this trial, bacteremia did not
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impact on outcome. Risk factors for bacteremia were renal failure, need
Oral nutrition should be encouraged in those with an acute liver injury for ventilation, and severity of encephalopathy. Determinants of survival
who are not encephalopathic. Progressive encephalopathy and/or anorexia were liver transplantation, severity of encephalopathy, age, and lactate.
are likely to result in decreased calorie intake. Consideration may be given Management requires assiduous attention to line care, and avoidance
to insertion of an enteral tube to facilitate feeding. Risk-benefit ratio should of nosocomial sepsis. Decision to offer antimicrobial therapy should
be assessed at an individual level to account for problems such as bleeding be based on individual risk factors and clinical features; the choice of
during placement of the enteral tube and for the risk of large nasogastric antimicrobial should be determined by local policies based on micro-
aspirates and risk of micro-aspiration if encephalopathy progresses. biological sensitivity data, starting with a broad empiric regimen and
There is a moderate risk of pancreatitis in patients with acute and narrowing as culture data return. Systemic antifungal therapy would
hyperacute etiologies of acute liver failure and axial imaging to quantify normally be considered for patients who are listed for emergent trans-
this may be required if there is clinical suspicion. Management is as per plantation with established organ failure or in those requiring ventilator
pancreatitis in other critical care settings (see Chap. 108); however, the and renal support in association with significant coagulopathy.
finding of severe pancreatitis is a relative contraindication to emergent ■
liver transplantation. ENCEPHALOPATHY AND ELEVATED INTRACRANIAL PRESSURE
Guidance with regard to nutritional needs in patients with ALF is The management of altered conscious levels in this group of patients can
largely empirical. Calorie and protein requirements are as per critically be challenging. Patients with subacute and subfulminant presentations
ill populations of other etiologies. Ammonia monitoring may be useful often do not present initially with encephalopathy. If encephalopathy
during commencement of feeding to ensure that there is no associated develops later in the course of liver failure, it is often in the face of sepsis
increase in measured levels. or some other clear precipitant. The delayed presentation or absence of
Acid suppression therapy with H -blockers or proton pump inhibitors hepatic encephalopathy in this cohort of patients can make the decision
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is normally prescribed, given that these patients will have a coagulopathy to proceed to transplantation difficult. In some situations, by the time
on the basis of their liver failure. H -blockers are preferred since they are encephalopathy occurs, there may be a very rapid subsequent deteriora-
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associated with a lower incidence of C dificile infections. tion in overall clinical status. This has led some to suggest that in those

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