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Hyperkalemia and hypokalemia

Potassium (K + ) is the most abundant intracellular cation and is maintained within narrow physiologic limits. Although reported values vary, the normal serum K + level in humans typically ranges from 3.5 to 5.0 mEq Alterations in electrolyte concentrations occur frequently in critically ill patients, likely the result of malnutrition, end-organ dysfunction, comorbid diseases, and polypharmacy. Early recognition and treatment of K + abnormalities are…

Metabolic acidosis and alkalosis

Acid-base disorders Acid-base disorders can be quantified by using the physiologic, base-excess, and physiochemical approaches (Stewart method). The bicarbonate [HCO 3 − ] buffer system plays a central role in the physiologic and base-excess methods. They share nearly common explanations while describing the types and mechanisms behind acid-base disturbances. However, Stewart’s more recent (1980s) acid-base approach differs significantly from the other two approaches by not attributing…

Oliguria

Oliguria is one of the most common problems faced by clinicians in the intensive care unit (ICU). The goal of this chapter is to understand the reasons for oliguria and provide an evidence-based, practical, physiology-based approach to diagnosing and treating it. Definitions and epidemiology An average person excretes 600 mOsm of solute/day, and the maximal urinary concentration that can be achieved is 1200 mOsm Hence a…

Polyuria

Pathophysiology and classification The daily urine output is determined predominantly by the daily intake of fluids, daily solute excretion, and the urine-concentrating ability of the nephrons. The average person excretes about 600–800 mOsm of solutes per day, and average urine output is about 1.5–2.5 L Polyuria happens usually because of one or more of the following mechanisms: Increased fluid intake, necessitating excretion of a large volume…

Pleural effusion in the intensive care unit

Epidemiology Pleural effusions are common in the intensive care unit (ICU). Estimated incidence depends on screening method and ranges from 8% by physical examination to 60% by ultrasound. , Transudative causes of effusion (heart failure, hypoalbuminemia) predominate in the medical ICU, whereas hemothorax and postsurgical effusions occur more frequently in trauma and cardiac ICUs. In any setting, 83% of patients with acute respiratory distress syndrome have…

Pulmonary edema

Background and epidemiology of pulmonary edema Acute pulmonary edema is a commonly occurring emergency that demands immediate medical attention. , It is broadly classified into cardiogenic (increased hydrostatic pressure) or noncardiogenic (increased microvascular permeability) causes; however, it is common for critically ill patients to present with pulmonary edema arising from a combination of cardiogenic and noncardiogenic etiologies. It is a major health problem, accounting for ∼10%…

Hyperbaric oxygen in critical care

Hyperbaric oxygen (HBO 2 ) treatment involves intermittent breathing of pure oxygen at greater than ambient pressure (>1.4 atmospheres absolute [ATA]). Over the past 20 years, HBO 2 has undergone refinement, with an increased understanding of the mechanisms of action and clinical applications. Applications HBO 2 treatment is carried out in either a monoplace (single person) or multiplace (typically two or more) chamber. Pressures applied while…

Acute respiratory failure

Acute respiratory failure (ARF) is defined by the sudden onset of severe impairment of pulmonary gas exchange and is characterized by the inability of the lungs to meet the body’s metabolic needs for the transport of oxygen (O 2 ) into the blood and/or removal of carbon dioxide (CO 2 ) from the blood. The diagnosis of ARF is based on the measurements of arterial blood…

Arterial hypoxemia

Normal cell function requires an adequate oxygen supply. Lack of oxygen at the cellular level is called hypoxia. Oxygen delivery (DO 2 ) to the tissues is determined by cardiac output and the arterial oxygen content, which in turn is determined by the hemoglobin concentration and its oxygen saturation. Hypoxemia is defined by a significantly low partial pressure of oxygen (PaO 2 ; less than about…

Tachycardia and bradycardia

The resting adult heart rate normally ranges from 60 to 100 beats per minute (bpm). Heart rate and rhythm abnormalities occur frequently in critically ill patients, and the incidence of sustained arrhythmias can approach 40% in some intensive care unit (ICU) settings. , Common arrhythmia risk factors in the critically ill include advanced age, sepsis, myocardial ischemia, respiratory failure, renal insufficiency, acute brain injury, polypharmacy, metabolic…

Low systemic arterial blood pressure

Introduction Assessment of hemodynamics is an important skill in the critical care setting. The goal of hemodynamic monitoring in a critically ill patient is to ensure adequate tissue oxygen delivery and end-organ perfusion. Low systemic arterial blood pressures are commonly encountered in the clinical setting, and a thoughtful, systematic approach should be used. You’re Reading a Preview Become a Clinical Tree membership for Full access and…

Very high systemic arterial blood pressure

Hypertensive emergency (HE) is a severe elevation in systemic blood pressure combined with new or progressive end-organ damage most frequently in the cardiac, renal, and central nervous systems. HE is an infrequent clinical presentation of acute hypertension that requires immediate, titrated blood pressure reduction. Although HE is often associated with a blood pressure elevation >180/110 mm Hg, the diagnosis of HE is based upon the patient’s…

Fever and hyperthermia

“Humanity has but three great enemies: fever, famine and war; of these by far the greatest, by far the most terrible, is fever.” William Osler, from his address to the 47th annual meeting of the American Medical Association, 1896 Fever is defined as an increase in body temperature as a result of a pathophysiologic response that increases the body’s normal thermoregulatory set point. This set point…

Management of acute pain in the intensive care unit

Introduction Pain management in the critically ill patient is complex. Each patient brings a unique set of sociodemographic, pharmacokinetic, and pharmacogenomic variables that are coupled with underlying psychosocial and medical comorbidities. These not only influence a patient’s response to painful stimuli but also to treatment. We know that critically ill patients experience pain at rest, during routine intensive care unit (ICU) care, and during procedures. ,…

Agitation and delirium

Agitation and delirium are commonly encountered in the intensive care unit (ICU). Although frequently underrecognized, delirium is present in up to 80% of critically ill adults on mechanical ventilation when routinely assessed. Delirium and agitation are more than just an inconvenience; these conditions can have deleterious effects on patient and staff safety and contribute to poor outcomes, including increased duration of mechanical ventilation, increased ICU length…

Sudden deterioration in neurologic status

Patients admitted to the intensive care unit (ICU) with critical illness or injury are at risk for neurologic complications. A sudden or unexpected change in the neurologic condition of a critically ill patient often heralds a complication that may cause direct injury to the central nervous system (CNS). Alternatively, such changes may simply be neurologic manifestations of the underlying critical illness or treatment that necessitated ICU…

Pregnancy-associated diseases

It is not entirely clear how a chapter on pregnancy fits into a book titled Anesthesia and Coexisting Disease . Pregnancy is not a disease, but a normal physiologic condition, usually associated with and dependent on relatively good health. For most so-called coexisting diseases in this book, the clinical situation being analyzed and discussed is that of a patient needing surgery, usually or often unrelated to…

Pediatric diseases

Unique considerations in pediatric patients When it comes to anesthetic care, children are not merely small adults. Many considerations come into play beyond underlying medical conditions: the child’s age, developmental stage (physically and psychologically), physiology, social circumstances, and family factors all play a significant role. Anesthesia-induced developmental neurotoxicity The topic of anesthesia-induced developmental neurotoxicity has garnered widespread attention in recent years. Mounting evidence from animal studies…

Diseases of aging

Introduction Compared to 100 years ago, people are living much longer. The US life expectancy for men in 1900 was 48 years and for women, 51 years. Currently the average life expectancy in the United States exceeds 75 years. The elderly, defined as those older than 65 years, constitute one of the fastest-growing segments of the population. In 2010, the US elderly population numbered 47 million,…

Psychiatric disease, substance use disorders, and drug overdose

The prevalence of mental illness and substance use disorders in the United States is about 30%, so these conditions are often present in patients undergoing anesthesia and surgery. Effects of and potential drug interactions with psychotropic medications are important perioperative considerations, as are potential behavioral issues. In addition, substance use and suicide represent significant occupational hazards for anesthesiologists. Mood disorders Mood is defined as a temporary…