Critical Care Update 2017 Atul Kulkarni, Subhash Todi, Kapil Zirpe
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1Hemodynamic Monitoring and Resuscitation
SECTION EDITOR: VIJAYA P PATIL2

Fluid Therapy in Resource-limited SettingsCHAPTER 1

Sameer A Jog,
Maurizio Cecconi,
Swapnil R Patharekar
 
INTRODUCTION
Intravenous fluid administration is the most common therapy used in the intensive care unit (ICU). Judicious use of intravenous fluids is essential in an ICU. The challenge is greater in limited resource settings since there is paucity of reliable parameters to guide fluid therapy. The “resource-limited setting” need not always be associated with economical as well as situational constraints like availability of appropriate ambulance or emergency room services in mass casualty situations.
Hypotension present at the hospital admission is associated with a significant mortality and studies have shown that early fluid therapy is associated with better outcomes.1,2
On the other hand, overzealous fluid therapy is also associated with many complications, e.g., pulmonary edema. Excessive fluid administration may be proinflammatory and potentially injurious.3,4 It is, thus, imperative to know how to give the right amount of fluid.
Unfortunately, there is a paucity of good quality data in the field of fluid therapy. Hence, the decision-making in an individual patient is always a difficult task. Considering this background, optimum fluid therapy in a given patient, in a given setting, always remains a challenge for a treating physician even in a well-equipped, resource-rich ICU. In a resource-limited setting, this problem is even more complex.
 
DEFINING RESOURCE-LIMITED SETTING
When we say resource-limited setting in the context of intensive care medicine or emergency medicine, at least the following resources should be available for patient care. They are:
  • Good clinical examination, especially to detect hypoperfusion
  • At least 3-lead electrocardiogram monitoring for rhythm and rate
  • Accurate noninvasive blood pressure measurement instrument
  • Instrument for measuring oxygen saturation
  • Facility for urinary catheterization and measuring half or one hourly urine output
  • Peripheral intravenous access by a large bore cannulas
  • In case of total vascular collapse—central venous access
  • Necessary intravenous fluids like crystalloids and dextrose solutions
  • Pressure bags to deliver the fluids at fast rate
  • Oxygen therapy devices like oxygen cylinders, masks, and venturi
  • Basic resuscitation drugs.
 
SHOCK5,6
It is a life-threatening, generalized form of acute circulatory failure associated with inadequate perfusion to the tissues.1 It could be hypovolemic, cardiogenic, obstructive, or distributive. The presentation of these shocks can overlap with each other, like patient presenting with shock due to hypovolemia owing to external blood loss can develop infection and lead to worsening of shock.
 
FLUID THERAPY
The most important physiological target of fluid administration is to improve tissue perfusion. Hemodynamic optimization with fluids has shown to improve patient outcome when applied in the early phases of sepsis and in the perioperative period.7,8 Fluid administration is, hence, considered as therapy.
The following points should be considered while administrating fluid therapy in ICU in resource-limited settings.
 
Baseline Patient Demographics
This is one of the most important determinants of fluid therapy.
Following patient groups barely respond to fluid and, in fact, overzealous fluid therapy in these patient groups can be detrimental:7,84
  • Chronic renal failure with anuria
  • Acute coronary syndrome
  • Acute and chronic decompensated heart failure
  • Pulmonary embolism.
 
Indications
The indications relevant to resource-limited settings are:8
  • Hypotension due to any cause
  • Increased requirement of vasopressors
  • Decreased urine output
  • Increased skin mottling.
Most common indication for fluid therapy, as suggested by the Fluid Challenges in Intensive Care (FENICE)8 study, is hypotension due to any reason.
 
Type of Fluid7
Resuscitation fluids can be divided into two broad categories—colloids and crystalloids.
  1. Colloids: The colloids are aqueous solutions that contain both large organic macromolecules and electrolytes. Colloids are subdivided into natural and synthetic colloids.
    1. Natural colloid: Albumin is the prototype of natural colloid. It was also the first colloid solution used clinically. It is harvested from human plasma and is available in different concentrations like 4, 5, 20, and 25%.
      Saline versus Albumin Fluid Evaluation (SAFE)9 and Albumin Italian Outcome Sepsis (ALBIOS)10 trials have clearly shown that use of albumin does not offer any advantage over crystalloids. In fact, use of albumin can be detrimental in patients with traumatic brain injury.11 Though there is some advantage for using albumin in early sepsis,12 the evidence is not strong enough to recommend its use in resource-limited settings. The cost of albumin is also a deterring factor to use it in these settings.
    2. Synthetic colloids:7 They are divided into three groups—starches [hydroxy ethyl starch (HES)], gelatins, and dextran. These colloids were promoted as cheaper alternative to albumin.
      1. Gelatins: These are derived from bovine gelatin, their colloid base is protein.
      2. Dextran: It is a carbohydrate based colloid. Bacteria make this polysaccharide molecule during ethanol fermentation.
      3. Hydroxy ethyl starch: Hydroxy ethyl starch are derived from the starch of potatoes or maize, and their colloid base is a large carbohydrate molecule. Solutions of molecular weight like 130, 200, and 450 kD are available.
      Based on current evidence, colloid use is not recommended in the ICU. Colloid usage has shown to increase incidence of acute kidney injury (AKI) and need for renal replacement therapy.13,14 Though there is some controversy due to emerging evidence from recent trials,15,16 the overall consensus is to avoid their usage in the ICU. Also, as colloids are costlier than crystalloids, their usage in resource-limited settings is limited.
  2. Crystalloid solutions: These fluids are the first choice for fluid resuscitation. They are well-tolerated and inexpensive.
    1. Sodium chloride (saline): This is the most commonly used crystalloid solution globally. There are few concerns about the high chloride content of normal saline, incidence of hyperchloremic metabolic acidosis, and renal replacement therapy;17,18 then again, evidence is not strong enough to discard its use routinely.
    2. Balanced or physiological solutions: These are derivatives of Hartmann's and Ringer's solutions.
    Due to their cost, regular use of these fluids in resource-limited settings is not recommended. In addition, currently there is no strong evidence to support the routine use of balanced crystalloids in the ICU.19
 
Volume and Dose
It is very difficult to generalize dose and volume of fluid. The requirements as well as response vary greatly during the course of any critical illness. Also, no single physiological or biochemical parameter is particularly useful to decide about fluid responsiveness. However, systolic hypotension and oliguria are used as triggers to administer a fluid challenge. It ranges from 200 to 1,000 mL of crystalloid for an adult patient.
Surviving Sepsis Campaign has recommended an initial fluid resuscitation of 30 mL/kg of crystalloids in septic patients with hypotension and/or lactate more than 4 mmol/L. A fluid challenge should consist of a volume large enough (no more, no less in theory) to raise the mean systemic filling pressure20 and increase venous return (cardiac output) in a preload responsive patient. Also, importantly, fluid resuscitation needs to be individualized to the patients need and clinical indication. In the perioperative period volumes between 250 and 500 mL of fluids is routinely used.21 Most studies involving nonsurgical patients have used fluid challenges of 500 mL given within 30 minutes.22
 
Initiation and Endpoints
In resource-limited settings, where advanced laboratory testing or hemodynamic monitoring are lacking, the task of identifying early stages of circulatory dysfunction mainly relies on proper clinical examination and basic laboratory testing.
 
Heart Rate
Heart rate (HR) is an easily available tool to assess fluid responsiveness in resource-limited settings. The contribution of HR to cardiac output and regulation of blood pressure is crucial. Tachycardia is an important early sign of shock.5 However, tachycardia in shock could partly be due to other factors, including pain, stress, or anemia. In addition, bradycardia could be present in severe hypovolemia. The specific value of HR to guide resuscitation has been poorly studied. It is also obvious that a decrease in HR after a fluid challenge indicate fluid responsiveness. However, the HR responses in studies testing the fluid responsiveness in ICU patients were variable. While some studies found a significant decrease in HR after fluid administration in responders,23 others reported no change in HR after fluid challenge in spite of having a significant increase in cardiac index.24 Therefore, HR alone cannot be used to predict fluid responsiveness.5
 
Blood Pressure
Components of blood pressure are25 systolic arterial pressure (SAP), diastolic arterial pressure (DAP), mean arterial pressure (MAP), and pulse pressure (PP).
 
Systolic arterial pressure
A SAP value lower than normal (e.g., 90 mmHg) may be associated either with a normal DAP (e.g., 80 mmHg) or a low DAP (e.g., 50 mmHg). If PP is not low, then no clear information on stroke volume can be drawn. Also, if pulse pressure is low as in first case, stroke volume is expected to be low, especially in cases of stiff arteries. Knowledge of the sole value of SAP is, thus, not good guide to decide about requirement of intravenous fluids.
 
Diastolic arterial pressure
The factors which determine DAP are arterial tone and HR. Therefore, a low DAP (e.g., 50 mmHg) suggests a low arterial tone, especially in the case of tachycardia. A low DAP, thus, is indication for use of vasopressor, although fluids can also be given in septic shock patients. Hence, DAP value alone also cannot indicate fluid requirement.
 
Mean arterial pressure
A low MAP may be associated with cardiogenic shock (right or left) for which fluid therapy can be detrimental. Conversely, during hypovolemia, MAP can be maintained due to compensatory mechanisms that increase vascular resistance. Thus, any particular level of MAP as trigger for fluid challenge can be misleading.
Again, MAP alone may not be sufficient to determine adequacy of fluid resuscitation. An increase in MAP after fluid challenge may indicate positive response but absence of it does not suggest that patient is not fluid responsive.
 
Pulse pressure
A low PP suggest low stroke volume and in the presence of shock, this would encourage fluid administration, unless signs of pulmonary edema are present. However, the need of fluid therapy is not absolutely certain since low stroke volume can also be due to cardiac failure. In patients with stiff arteries due to aging or comorbidities, PP may not be low in spite of low stroke volume.
In spite of this, changes in PP follow the changes in cardiac output induced by fluid infusion more reliably than MAP.
More importantly, results are more or less similar irrespective of the method of measurement of arterial blood pressure which may be arterial catheter or noninvasive oscillometric automated brachial cuff. Also, the presence of arrhythmias do not change the results.26 Hence, PP is one of better index for fluid administration in resource-limited settings.
 
Shock Index
Shock index (SI) is the ratio of HR divided by SAP (HR/SAP). Normal value for SI range is 0.5–0.7 in healthy adults. Since isolated HR or SAP may not be sufficient to detect early phases of shock or hypovolemia. An SI was originally described in trauma patients.9 Shock index has a linear inverse relationship to cardiac output and stroke volume.10 An SI ≥1.0 has been associated with a bad outcome in shock patients.27 In trauma patients, it can be used to stratify patients for increased transfusion requirements and early mortality.28 Therefore, it is considered as the most important vital sign to detect acute hypovolemia and circulatory failure in trauma patients. It has also shown relevance in septic shock patient as well and correlate well with lactate levels. In summary, SI is one of easiest, reliable, and inexpensive vital sign which can be used in patients with shock to determine volume responsiveness.
 
Capillary Refill Time
It is defined as the time taken for color to return to an external capillary bed after pressure is applied to cause blanching. It can be measured by holding a hand higher than heart level and pressing the soft pad of a finger or fingernail until it turns white, then taking note of the time needed for the color to return once pressure is released.29
Normal values for capillary refill time (CRT) are <2 seconds in young individuals and values up to 4.5 seconds are normal in the elderly.29 Capillary refill time can assist in assessment and prognostication of trauma, major abdominal surgery, and early septic shock patient.2932 Patients with abnormal peripheral perfusion presented with higher lactate levels and have a higher incidence of circulatory complications.
Capillary refill time is a rapid flow-responsive parameter that can be used in limited-resource settings as a trigger and response during fluid resuscitation.33 A recent study has demonstrated that the use of CRT as a guide for fluid therapy is associated with almost 2 L of lesser fluids in comparison to the classic approach, and also to a lesser organ dysfunction.32
Despite this, it was used as a trigger for fluid resuscitation in less than 8% of cases in the FENICE trial.8 Limitations for use of CRT can be interobserver variability, skin color, and influence of ambient temperature.29 In spite of this, ease of doing it and valuable information that it can give, this parameter needs justice in resource-limited settings. Routine use of CRT is highly recommended for trigger, guide, prognostication, and stratification during fluid resuscitation process. Normal CRT after fluid challenge denotes good prognosis while the opposite is associated with increased mortality.6
 
Mottling Index
Mottling is defined as patchy skin discoloration that usually starts around the knees. It is due to heterogeneous, small vessel vasoconstriction, and is thought to reflect abnormal skin microperfusion. Mottling is easily available sign that can be used for assessment of circulatory dysfunction.34
It has been shown to predict mortality in septic shock. Mottling is quantified according to a mottling score. Score varies between 0 and 5. A higher score correlates with increased mortality. High doses of vasopressors can also increase skin mottling and lead to purpuric changes.
 
Jugular Venous Pressure
The jugular venous pressure (JVP) is the indirectly observed pressure over the venous system via visualization of the internal jugular vein.35 The patient is positioned at 30°, and the filling level of the internal jugular vein determined. In healthy people, the filling level of the jugular vein should be <3 cm vertical height above the sternal angle. Low JVP usually indicated fluid responsiveness. With high JVP, one should be cautious about fluid resuscitation.35 There are many limitations of JVP, like assessment of JVP is technically complex, difficult to interpret, and is very subjective. The JVP also does not correlate well with CVP. More importantly, it can be used as a safety limit for fluid resuscitation. A significant increase in JVP before or during fluid resuscitation should alert clinician of fluid overload.
 
Urine Output
During early shock, multiple neurological and hormonal mechanisms get activated to maintain blood flow to vital organs including kidney. Secondary functional changes in renal blood flow, glomerular filtration, or tubular function may result in oliguria.36 However, oliguria is a nonspecific symptom and could also be present in mild dehydration without hypoperfusion and in major surgery which may or may not reflect renal or systemic hypoperfusion during early shock. Importantly, during septic shock and post major surgery, the presence of profound intrarenal microcirculatory abnormalities that are triggered by proinflammatory mediators are the main mechanisms for pathophysiology of AKI than hypoperfusion and these abnormalities do not revert with systemic flow increasing maneuvers.36
Despite these limitations, oliguria is used as a trigger and target for fluid resuscitation in 18% patients.8 On the contrary, several studies have shown that positive fluid balance is associated with morbidity and mortality in patients with AKI in different settings.37 Fluid overload in these situations may lead to cardiac dysfunction and intra-abdominal hypertension which may hasten the onset of AKI and perpetuate oliguria.
 
Blood Lactate Levels39 (Box 1)
The normal serum lactate level in resting humans is approximately 1 mmol/L (0.7–2.0). The value is the same in venous or arterial blood. Use of a tourniquet can lead to pseudoelevation of lactate level. An increase in serum lactate levels may indicate poor tissue perfusion. Large data are now available to indicate serum lactate levels as an appropriate target for fluid resuscitation, and is recommended to use as surrogate measure of tissue microperfusion. Repeated measurements of lactate concentrations over time are particularly useful for monitoring the response to therapy.
 
CONCLUSION
Appropriate fluid therapy in a resource-limited setting is really a challenging issue. On the background of paucity of evidence based guidelines, this task is more complex. Use of basic parameters and sound understanding of physiology will definitely enhance the decision-making ability of a physician. However, at the bedside in an emergency situation, one may have to use his/her own discretion to answer the million dollar question “how much fluid?”7
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