DOCSLIB.ORG

Acid-Base Problems in Surgery

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Acid-Base Problems in Surgery World J. Surg. 7, 590-598, 1983 World Journal ol Sd ry 1983 by the Soci~t~ lnternationale de Chirurgie Acid-Base Problems in Surgery John Clark, M.B., Ch.M., F.R.C.S., and William F. Walker, D.Sc., Ch.M., F.R.C.S. (Eng), F.R.C.S. (Ed), F.R.S. (Ed) Department of Surgery, Ninewells Hospital and Medical SchooL, Dundee, United Kingdom The identification and treatment of various clinical states of body's built-in defenses are designed to deal with acid-base imbalance assume particular significance in ma- the normal metabolic hazard of acidosis. jor surgery and in patients with multiple organ failure. There are several important acid-base pairs that Metabolic acidosis, metabolic alkalosis, respiratory acido- either liberate or receive protons depending on the sis, respiratory alkalosis, and mixed disorders of acid-base direction in which a reaction is driven according to balance are described and a management plan for each the law of mass action. Those that are soluble in entity is defined. intracellular and extracellular fluid include carbonic acid/bicarbonate, monobasic/dibasic phosphate, ammonium/ammonia, and lactic acid/lactate. The Disorders of acid-base metabolism are frequently acidic residues of many proteins are important encountered in major surgery, particularly in the buffers fixed in tissues. Because all buffer pairs very young and the elderly. This is especially so share the same hydrogen ions in a homogeneous when there is infection, shock, intestinal obstruc- system, acid-base changes may be monitored by tion, or fistula leakage and in those with cardiores- analyzing the components of one of the pairs, the piratory or renal failure. It may be difficult to dissociation constant of which is known. The com- identify the essential cause of an acid-base fault and posite effect of all these pairs is to absorb large full history-taking, clinical evaluation, and bio- quantities of hydrogen ions instantaneously by chemical investigation may be necessary. In pa- shifting the equilibrium in the direction of the acidic tients with multiple organ failure, mixed acid-base form in response to a rise in hydrogen ion concen- disorders present the clinician with a great chal- tration. The withdrawal of hydrogen ions or addi- lenge in which the stakes may be the life or death of tion of base shifts the reactions in the opposite the patient. direction. The result of adding hydrogen ions is a negligible change in hydrogen ion concentration at the expense of reducing the complement of basic Physiology components and increasing the complement of acid- ic components of the buffer system. The pH Acid-base homeostasis involves a 3-phase re- changes only when the supply of base is exhausted. sponse. Endogenous or exogenous acid or alkali is Hydrogen ions are transported harmlessly in solu- buffered immediately, then there is a respiratory ble buffer forms or on globin from the point of origin phase of rapid pH adjustment, and finally a slow to a point of hydrogen ion disposal, where the acidic renal phase of restoration of buffer systems. The form of the buffer dissociates to restore the original conditions. Hydrogen ions are secreted by the gastric mucosa and renal tubular epithelium. Buffer- m ing occurs in the urine as monobasic phosphate and Reprint requests: John Clark, Ysbyty Glan Clwyd, ammonium protect the urinary epithelium from acid Bodelwyddan, Rhyl, Clwyd LL18 5UJ, North Wales, damage. United Kingdom. The carbonic acid/bicarbonate pair contributes J. Clark and W.F. Walker: Acid-Base Problems 591 approximately 40% of the huge plasma and tissue basic groups in the globin moiety, and HCO3- buffer system and is unique in that independent diffuses back into the plasma in exchange for C1-. physiological mechanisms control the concentra- At low PO2 levels, the basic groups of globin have tion of each component. Buffering capacity can be an increased avidity for H § A lesser, but still extended by generating further acid by CO2 reten- significant, amount of CO2 forms carbamino com- tion or further base by bicarbonate reabsorption. pounds with globin and other proteins. The se- Most of the remaining plasm a and tissue buffer quence is reversed at the pulmonary alveolus and capacity lies in proteins and the phosphate pair. COz is excreted. This method of transport is in Proteins fixed in tissues buffer on site and then effect largely one of H § transport in the protein liberate hydrogen ions to soluble systems for trans- buffer system, and the capacity is greater than port. Hemoglobin provides protein buffer transport. would be possible for CO2 in solution. Changes in Plasma is readily accessible for analysis and the PCO2 are minimized. The arterial PCO2 is affected bicarbonate system is most easily assayed. Al- by the rate of CO2 production, the rate of alveolar- though interstitial fluid and plasma equilibrate rap- capillary diffusion, and the rate of pulmonary alveo- idly and hydrogen ions cross cell membranes readi- lar ventilation. The last is the dominant influence. ly, plasma pH does not necessarily reflect pH in Because the gas diffuses freely, alveolar partial cells, cellular organelles, or cerebroSpinal fluid. The pressure of carbon dioxide (PACO2) equilibrates concentration of CO2 dissolved in plasma is propor- extremely rapidly with capillary and hence the tional to the arterial partial pressure of CO2 systemic arterial partial pressure of CO2 (PaCO2). (PaCO2). Approximately 0.12% of this CO2 is con- Arterial PCO2 is easily measured. verted at once into carbonic acid by the ubiquitous Respiratory depression leads to a rise in PaCO2 carbonic anhydrase. When carbonic acid is re- and acidOsis, but the normal adaptive response moved, it is replaced at once from the carbon occurs partly from further dissociation of carbonic dioxide store in solution. Carbonic acid dissociates acid and partly from increased renal reabsorption of as a weak acid and the relationship between the bicarbonate, so that in compensated respiratory concentration of carbonic acid, hydrogen ions, and acidosis the plasma has a normal or low pH, high bicarbonate ions is expressed in the Henderson- PaCO2, and high bicarbonate. Respiratory stimula- Hasselbalch equation: tion leads to a low PaCO2 and high pH (respiratory alkalosis), and the normal adaptive response is to pH = 6.1 + log [HCO3-/(0.03 PaCO2)] decrease renal reabsorption of bicarbonate and de- Factors that affect PaCO2 and bicarbonate concen- crease plasma bicarbonate concentration. Metabol- tration have a direct bearing on the pH of tissue ic events that lead to.a reduction in plasma bicar- fluids, and pathological or physiological events that bonate cause metabolic acidosis. The respiratory alter one of these components have 4 conse- center is stimulated by cerebrospinal fluid acidosis quences. First, the change in ratio of PaCO2 to resulting in compensatory hyperventilation and a bicarbonate concentration results in an alteration of reduction in PaCO2. This tends to redress the pH. Second, the law of mass action dictates that the balance in the Henderson-Hasselbalch equation and dissociation reaction of H2CO3 proceeds in the return the pH toward normal. Metabolic alkalosis direction of the component that has become rela- results from metabolic events that lead to an accu- tively lowered. Third, immediate readjustment of mulation of plasma bicarbonate. Plasma pH rises the ratio is obtained by respiratory readjustment of but respiratory center depression results from the PaCO2 and pH is restored. Fourth, and less rapidly, low concentration of hydrogen ions in cerebroSpinal renal tubular adjustment of both H § excretion and fluid, so alveolar CO2 accumulates leading to a bicarbonate reabsorption restores the total body compensatory rise in PaCO2. The origin of the 4 complement of H § and bicarbonate buffer toward types of pH disturbance can, therefore, be deduced normal. There follows reversal of the previous shift from the arterial pH. PaCO2, and bicarbonate, in the dissociation of H2CO3 Until both the ratio and provided a single acid-base disorder is present. This the concentration of carbon dioxide and bicarbon- deduction may not be so simple if adaptive respons- ate are normal again. Renal reabs0rption of bicar- es are not normal because of the operation of 2 or bonate takes 6-12 h to be initiated and 3-5 days for more acid-base disorders, for example, metabolic a complete response. alkalosis in a patient in chronic respiratory failure. Approximately 20,000 mmol CO2 is produced As a guide as to whether an acid-base disturbance daily, depending on the metabolic rate. Carbon is of single origin, a number of formulae have been dioxide is transported by diffusion gradients in developed. In simple acute respiratory acidosis and tissues. In the bloodstream, COe enters red cells alkalosis, the appropriate deviation of pH (ApH) and carbonic anhydrase mediates conversion to from the normal 7.40 should be 0.7 times the carbonic acid which dissociates, H + attaches to observed deviation (APaCO2) of PaCO2 from the 592 World J. Surg. Vol. 7, No. 5, September 1983 normal 40 mm Hg. In chronic respiratory acidosis, sured anions that account for the gap are sulphate, adaptive mechanisms are established and a lesser phosphate, lactate, and other organic anions. Pro- pH change occurs in response to a change in PaCO2 teins contribute and have zwitterion properties, that so that A pH = 0.3 x A PaCO2. Chronic respiratory is, the charge varies with the pH. Usually, in alkalosis is the most completely compensated acid- acidosis the fall in plasma bicarbonate is replaced base disorder and A pH = 0.17 x A PaCO2. The pH by an increase in chloride and there is no change in can become normal. In metabolic acidosis, pH= the anion gap. In certain metabolic states, typified 1.3 (approximately) x total CO2 (or actual bicar- by diabetic ketoacidosis, organic anions are present bonate).
Load more

Recommended publications
  • Pathophysiology of Acid Base Balance: the Theory Practice Relationship
    Intensive and Critical Care Nursing (2008) 24, 28—40 ORIGINAL ARTICLE Pathophysiology of acid base balance: The theory practice relationship Sharon L. Edwards ∗ Buckinghamshire Chilterns University College, Chalfont Campus, Newland Park, Gorelands Lane, Chalfont St. Giles, Buckinghamshire HP8 4AD, United Kingdom Accepted 13 May 2007 KEYWORDS Summary There are many disorders/diseases that lead to changes in acid base Acid base balance; balance. These conditions are not rare or uncommon in clinical practice, but every- Arterial blood gases; day occurrences on the ward or in critical care. Conditions such as asthma, chronic Acidosis; obstructive pulmonary disease (bronchitis or emphasaemia), diabetic ketoacidosis, Alkalosis renal disease or failure, any type of shock (sepsis, anaphylaxsis, neurogenic, cardio- genic, hypovolaemia), stress or anxiety which can lead to hyperventilation, and some drugs (sedatives, opoids) leading to reduced ventilation. In addition, some symptoms of disease can cause vomiting and diarrhoea, which effects acid base balance. It is imperative that critical care nurses are aware of changes that occur in relation to altered physiology, leading to an understanding of the changes in patients’ condition that are observed, and why the administration of some immediate therapies such as oxygen is imperative. © 2007 Elsevier Ltd. All rights reserved. Introduction the essential concepts of acid base physiology is necessary so that quick and correct diagnosis can The implications for practice with regards to be determined and appropriate treatment imple- acid base physiology are separated into respi- mented. ratory acidosis and alkalosis, metabolic acidosis The homeostatic imbalances of acid base are and alkalosis, observed in patients with differing examined as the body attempts to maintain pH bal- aetiologies.
    [Show full text]
  • Guidelines for Potential Multiple Organ Donors (Adult). Part II
    ARTIGO ESPECIAL Glauco Adrieno Westphal, Milton Diretrizes para manutenção de múltiplos órgãos Caldeira Filho, Kalinca Daberkow Vieira, Viviane Renata Zaclikevis, no potencial doador adulto falecido. Parte II. Miriam Cristine Machado Bartz, Ventilação mecânica, controle endócrino metabólico Raquel Wanzuita, Álvaro Réa-Neto, Cassiano Teixeira, Cristiano Franke, e aspectos hematológicos e infecciosos Fernando Osni Machado, Joel de Andrade, Jorge Dias de Matos, Guidelines for potential multiple organ donors (adult). Part II. Alfredo Fiorelli, Delson Morilo Lamgaro, Fabiano Nagel, Felipe Mechanical ventilation, endocrine metabolic management, Dal-Pizzol, Gerson Costa, José hematological and infectious aspects Mário Teles, Luiz Henrique Melo, Maria Emília Coelho, Nazah Cherif RESUMO das alterações hematológicas é igualmente Mohamed Youssef, Péricles Duarte, importante considerando as implicações Rafael Lisboa de Souza A atuação do intensivista durante a da prática transfusional inapropriada. manutenção do potencial doador falecido Ressalta-se ainda o papel da ventilação na busca da redução de perdas de doadores protetora na modulação inflamatória e e do aumento da efetivação de transplantes conseqüente aumento do aproveitamen- não se restringe aos aspectos hemodinâmi- to de pulmões para transplante. Por fim, cos. O adequado controle endócrino-me- assinala-se a relevância da avaliação crite- tabólico é essencial para a manutenção do riosa das evidências de atividade infecciosa aporte energético aos tecidos e do controle e da antibioticoterapia na busca do maior hidro-eletrolítico, favorecendo inclusive a utilização de órgãos de potenciais doadores estabilidade hemodinâmica. A abordagem falecidos. A presente diretriz é uma iniciativa conjunta da Associação de Medicina INTRODUÇAO Intensiva Brasileira (AMIB) e da Associação Brasileira de Transplantes de Órgãos (ABTO) e teve apoio de SC Durante a evolução para a morte encefálica (ME) ocorrem diversas alterações Transplantes - Central de Notificação fisiológicas como resposta à perda das funções do tronco cerebral.
    [Show full text]
  • Acid-Base Physiology & Anesthesia
    ACID-BASE PHYSIOLOGY & ANESTHESIA Lyon Lee DVM PhD DACVA Introductions • Abnormal acid-base changes are a result of a disease process. They are not the disease. • Abnormal acid base disorder predicts the outcome of the case but often is not a direct cause of the mortality, but rather is an epiphenomenon. • Disorders of acid base balance result from disorders of primary regulating organs (lungs or kidneys etc), exogenous drugs or fluids that change the ability to maintain normal acid base balance. • An acid is a hydrogen ion or proton donor, and a substance which causes a rise in H+ concentration on being added to water. • A base is a hydrogen ion or proton acceptor, and a substance which causes a rise in OH- concentration when added to water. • Strength of acids or bases refers to their ability to donate and accept H+ ions respectively. • When hydrochloric acid is dissolved in water all or almost all of the H in the acid is released as H+. • When lactic acid is dissolved in water a considerable quantity remains as lactic acid molecules. • Lactic acid is, therefore, said to be a weaker acid than hydrochloric acid, but the lactate ion possess a stronger conjugate base than hydrochlorate. • The stronger the acid, the weaker its conjugate base, that is, the less ability of the base to accept H+, therefore termed, ‘strong acid’ • Carbonic acid ionizes less than lactic acid and so is weaker than lactic acid, therefore termed, ‘weak acid’. • Thus lactic acid might be referred to as weak when considered in relation to hydrochloric acid but strong when compared to carbonic acid.
    [Show full text]
  • Metabolic Alkalosis Is the Most Common Acid-Base Disorder in ICU
    Mæhle et al. Critical Care 2014, 18:420 http://ccforum.com/content/18/2/420 LETTER Metabolic alkalosis is the most common acid–base disorder in ICU patients Kjersti Mæhle1*, Bjørn Haug2, Hans Flaatten3,4 and Erik Waage Nielsen1,5,6 Publications give diverging information as to which alkalosis is a complication of mechanical ventilation metabolic acid–base disorder is the most common in in patients with chronic obstructive pulmonary dis- the ICU [1,2]. We explored the distribution of base ease [4]. excess (BE) values in a large number of ICU patients If the count of repetitive sampling influenced our re- and evaluated if this distribution was related to rising sults, we assume they are skewed towards acidosis, as sodium values after admission. BE values were ob- unstable and acidotic patients tend to have acid–base tained during ICU admission in selected periods samples drawn more frequently. from a first level small community hospital, a second Data from the Norwegian National Intensive Care level central hospital with university affiliations, and Registry [5] suggest that the difference in BE values be- a third level large Norwegian university/regional tween the three hospitals in our study may partly stem hospital. Sodium values were from ICU patients in from difference in patients’ lengths of stay. In our study, the second level hospital. Laboratory values were an- the second level hospital had the longest median length onymously retrieved from databases in each hospital, of stay (2.7 days). aggregated and analyzed in Qlikview or Excel and A coupling of metabolic alkalosis to rising sodium exported to GraphPad Prism for column statistics and values proposed by Lindner and colleagues [6] did not analysis of variance and for preparing graphs and seem to apply to patients in our study, as the day- frequency histograms.
    [Show full text]
  • Parenteral Nutrition Primer: Balance Acid-Base, Fluid and Electrolytes
    Parenteral Nutrition Primer: Balancing Acid-Base, Fluids and Electrolytes Phil Ayers, PharmD, BCNSP, FASHP Todd W. Canada, PharmD, BCNSP, FASHP, FTSHP Michael Kraft, PharmD, BCNSP Gordon S. Sacks, Pharm.D., BCNSP, FCCP Disclosure . The program chair and presenters for this continuing education activity have reported no relevant financial relationships, except: . Phil Ayers - ASPEN: Board Member/Advisory Panel; B Braun: Consultant; Baxter: Consultant; Fresenius Kabi: Consultant; Janssen: Consultant; Mallinckrodt: Consultant . Todd Canada - Fresenius Kabi: Board Member/Advisory Panel, Consultant, Speaker's Bureau • Michael Kraft - Rockwell Medical: Consultant; Fresenius Kabi: Advisory Board; B. Braun: Advisory Board; Takeda Pharmaceuticals: Speaker’s Bureau (spouse) . Gordon Sacks - Grant Support: Fresenius Kabi Sodium Disorders and Fluid Balance Gordon S. Sacks, Pharm.D., BCNSP Professor and Department Head Department of Pharmacy Practice Harrison School of Pharmacy Auburn University Learning Objectives Upon completion of this session, the learner will be able to: 1. Differentiate between hypovolemic, euvolemic, and hypervolemic hyponatremia 2. Recommend appropriate changes in nutrition support formulations when hyponatremia occurs 3. Identify drug-induced causes of hypo- and hypernatremia No sodium for you! Presentation Outline . Overview of sodium and water . Dehydration vs. Volume Depletion . Water requirements & Equations . Hyponatremia • Hypotonic o Hypovolemic o Euvolemic o Hypervolemic . Hypernatremia • Hypovolemic • Euvolemic • Hypervolemic Sodium and Fluid Balance . Helpful hint: total body sodium determines volume status, not sodium status . Examples of this concept • Hypervolemic – too much volume • Hypovolemic – too little volume • Euvolemic – normal volume Water Distribution . Total body water content varies from 50-70% of body weight • Dependent on lean body mass: fat ratio o Fat water content is ~10% compared to ~75% for muscle mass .
    [Show full text]
  • Residency Essentials Full Curriculum Syllabus
    RESIDENCY ESSENTIALS FULL CURRICULUM SYLLABUS Please review your topic area to ensure all required sections are included in your module. You can also use this document to review the surrounding topics/sections to ensure fluidity. Click on the topic below to jump to that page. Clinical Topics • Gastrointestinal • Genitourinary • Men’s Health • Neurological • Oncology • Pain Management • Pediatrics • Vascular Arterial • Vascular Venous • Women’s Health Requisite Knowledge • Systems • Business and Law • Physician Wellness and Development • Research and Statistics Fundamental • Clinical Medicine • Intensive Care Medicine • Image-guided Interventions • Imaging and Anatomy Last revised: November 4, 2019 Gastrointestinal 1. Portal hypertension a) Pathophysiology (1) definition and normal pressures and gradients, MELD score (2) Prehepatic (a) Portal, SMV or Splenic (i) thrombosis (ii) stenosis (b) Isolated mesenteric venous hypertension (c) Arterioportal fistula (3) Sinusoidal (intrahepatic) (a) Cirrhosis (i) ETOH (ii) Non-alcoholic fatty liver disease (iii) Autoimmune (iv) Viral Hepatitis (v) Hemochromatosis (vi) Wilson's disease (b) Primary sclerosing cholangitis (c) Primary biliary cirrhosis (d) Schistosomiasis (e) Infiltrative liver disease (f) Drug/Toxin/Chemotherapy induced chronic liver disease (4) Post hepatic (a) Budd Chiari (Primary secondary) (b) IVC or cardiac etiology (5) Ectopic perianastomotic and stomal varices (6) Splenorenal shunt (7) Congenital portosystemic shunt (Abernethy malformation) b) Measuring portal pressure (1) Direct
    [Show full text]
  • N Dullet , S Mathevosian , R Ahuja , a Anavim , D Nguyen , K Kansagra
    The Utility of an Interventional Radiology Trainee as a Member of the Intensive Care Unit Team N Dullet1, S Mathevosian2, R Ahuja3, A Anavim3, D Nguyen3, K Kansagra4, M Ferra3 1The University of Arizona, Tucson, AZ, 2UCLA David Geffen School of Medicine, Los Angeles, CA, 3Albert Einstein Medical Center, Philadelphia, PA, 4Kaiser Permanente Medical Center, Los Angeles, CA Background Mechanical Ventilation and Non-Invasive Ventilation Rounding in the ICU POCUS Definitions The role of the IR resident varies by institution and type of ICU, with some The IR resident is uniquely positioned Knowledge of critical care principles is essential as the IR Vt (Tidal Volume) The volume delivered per respiratory cycle. 6-8mL/kg for ARDS, while 8-10mL/kg may be used for other patients to provide assistance with timely service has become involved in increasingly complex residents rotating in SICU and others rotating in a MICU. In some instances, the resident acts as a senior, while the resident may act as an intern in other diagnosis and procedures with patient care. An ICU rotation is now a requirement of the PEEP (Peak End Expiratory Pressure) The pressure applied at the end of the expiratory phase, which keeps the alveoli open cases. POCUS. POCUS applications will be integrated IR residency and ESIR pathway. The ICU RR (Respiratory Rate) Number of respirations, reported per minute more thoroughly discussed in an F O Percent oxygenation of inspired air, room air is 21% rotation is an opportunity for the IR trainee to learn I 2 During pre-charting and pre-rounding, it is essential to review the accompanying poster.
    [Show full text]
  • Original Research Article Acid Based Disorders in Intensive Care Unit: a Hospital-Based Study
    International Journal of Advances in Medicine Rajendran B et al. Int J Adv Med. 2019 Feb;6(1):62-65 http://www.ijmedicine.com pISSN 2349-3925 | eISSN 2349-3933 DOI: http://dx.doi.org/10.18203/2349-3933.ijam20190086 Original Research Article Acid based disorders in intensive care unit: a hospital-based study Babu Rajendran*, Seetha Rami Reddy Mallampati, Sheju Jonathan Jha J. Department of General Medicine, Vinayaka Missions Medical College, Vinayaka Missions Research Foundation-DU, Karaikal, Puducherry, India Received: 08 January 2019 Accepted: 16 January 2019 *Correspondence: Dr. Babu Rajendran, E-mail: [email protected] Copyright: © the author(s), publisher and licensee Medip Academy. This is an open-access article distributed under the terms of the Creative Commons Attribution Non-Commercial License, which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. ABSTRACT Background: Acid base disorders are common in the ICU patients and pose a great burden in the management of the underlying condition. Methods: Identifying the type of acid-base disorders in ICU patients using arterial blood gas analysis This was a retrospective case-controlled comparative study. 46 patients in intensive care unit of a reputed institution and comparing the type of acid-base disorder amongst infectious (10) and non-infectious (36) diseases. Results: Of the study population, 70% had mixed acid base disorders and 30% had simple type of acid base disorders. It was found that sepsis is associated with mixed type of acid-base disorders with most common being metabolic acidosis with respiratory alkalosis. Non-infectious diseases were mostly associated with metabolic alkalosis with respiratory acidosis.
    [Show full text]
  • A Case-Based Approach to Acid-Base Disorders
    A Case-Based Approach to Acid-Base Disorders Justin Muir, PharmD Clinical Pharmacy Manager, Medical ICU NewYork-Presbyterian Hospital Columbia University Irving Medical Center [email protected] Disclosures None Objectives At the completion of this activity, pharmacists will be able to: 1. Describe acid-base physiology and disease states that lead to acid-base disorders. 2. Demonstrate a step-wise approach to interpretation of acid-base disorders and compensatory states. 3. Analyze contemporary literature regarding the use of sodium bicarbonate in metabolic acidosis. At the completion of this activity, pharmacy technicians will be able to: 1. Explain the importance of acid-base balance. 2. List the acid-base disorders seen in clinical practice. 3. Identify potential therapies used to treat acid-base disorders. Case A 51 year old man with history of erosive esophagitis, diabetes mellitus, chronic pancreatitis, and bipolar disorder is admitted with several days of severe nausea, vomiting, and abdominal pain. 135 87 31 pH 7.46 / pCO 29 / pO 81 861 2 2 BE -3.8 / HCO - 18 / SaO 96 5.6 20 0.9 3 2 • What additional data should be obtained? • What acid base disturbance(s) is/are present? Introduction • Acid base status is tightly regulated to maintain normal biochemical reactions and organ function • Body uses multiple mechanisms to maintain homeostasis • Abnormalities are extremely common in hospitalized patients with a higher incidence in critically ill with more complex pictures • A standard approach to analysis can help guide diagnosis and treatment Important acid-base determinants Blood gas generally includes at least: Normal range Measurement Description (arterial blood) pH -log [H+] 7.35-7.45 pCO2 partial pressure of dissolved CO2 35-45 mmHg pO2 partial pressure of dissolved O2 80-100 mmHg Base excess calculated measure of metabolic acid/base deviation from normal -3 to +3 SO2 calculated measure of Hgb O2 saturation based on pO2 95-100% - HCO3 calculated measure based on relationship of pH and pCO2 22-26 mEq/L Haber RJ.
    [Show full text]
  • Neurologic Complications of Electrolyte Disturbances and Acid–Base Balance
    Handbook of Clinical Neurology, Vol. 119 (3rd series) Neurologic Aspects of Systemic Disease Part I Jose Biller and Jose M. Ferro, Editors © 2014 Elsevier B.V. All rights reserved Chapter 23 Neurologic complications of electrolyte disturbances and acid–base balance ALBERTO J. ESPAY* James J. and Joan A. Gardner Center for Parkinson’s Disease and Movement Disorders, Department of Neurology, UC Neuroscience Institute, University of Cincinnati, Cincinnati, OH, USA INTRODUCTION hyperglycemia or mannitol intake, when plasma osmolal- ity is high (hypertonic) due to the presence of either of The complex interplay between respiratory and renal these osmotically active substances (Weisberg, 1989; function is at the center of the electrolytic and acid-based Lippi and Aloe, 2010). True or hypotonic hyponatremia environment in which the central and peripheral nervous is always due to a relative excess of water compared to systems function. Neurological manifestations are sodium, and can occur in the setting of hypovolemia, accompaniments of all electrolytic and acid–base distur- euvolemia, and hypervolemia (Table 23.2), invariably bances once certain thresholds are reached (Riggs, reflecting an abnormal relationship between water and 2002). This chapter reviews the major changes resulting sodium, whereby the former is retained at a rate faster alterations in the plasma concentration of sodium, from than the latter (Milionis et al., 2002). Homeostatic mech- potassium, calcium, magnesium, and phosphorus as well anisms protecting against changes in volume and sodium as from acidemia and alkalemia (Table 23.1). concentration include sympathetic activity, the renin– angiotensin–aldosterone system, which cause resorption HYPONATREMIA of sodium by the kidneys, and the hypothalamic arginine vasopressin, also known as antidiuretic hormone (ADH), History and terminology which prompts resorption of water (Eiskjaer et al., 1991).
    [Show full text]
  • ACS/ASE Medical Student Core Curriculum Acid-Base Balance
    ACS/ASE Medical Student Core Curriculum Acid-Base Balance ACID-BASE BALANCE Epidemiology/Pathophysiology Understanding the physiology of acid-base homeostasis is important to the surgeon. The two acid-base buffer systems in the human body are the metabolic system (kidneys) and the respiratory system (lungs). The simultaneous equilibrium reactions that take place to maintain normal acid-base balance are: H" HCO* ↔ H CO ↔ H O l CO g To classify the type of disturbance, a blood gas (preferably arterial) and basic metabolic panel must be obtained. A basic understanding of normal acid-base buffer physiology is required to understand alterations in these labs. The normal pH of human blood is 7.40 (7.35-7.45). This number is tightly regulated by the two buffer systems mentioned above. The lungs contain carbonic anhydrase which is capable of converting carbonic acid to water and CO2. The respiratory response results in an alteration to ventilation which allows acid to be retained or expelled as CO2. Therefore, bradypnea will result in respiratory acidosis while tachypnea will result in respiratory alkalosis. The respiratory buffer system is fast acting, resulting in respiratory compensation within 30 minutes and taking approximately 12 to 24 hours to reach equilibrium. The renal metabolic response results in alterations in bicarbonate excretion. This system is more time consuming and can typically takes at least three to five days to reach equilibrium. Five primary classifications of acid-base imbalance: • Metabolic acidosis • Metabolic alkalosis • Respiratory acidosis • Respiratory alkalosis • Mixed acid-base disturbance It is important to remember that more than one of the above processes can be present in a patient at any given time.
    [Show full text]
  • The ABC's of Acid-Base Balance
    JPPT REVIEW ARTICLE The ABC’s of Acid-Base Balance Gordon S. Sacks, PharmD The University of Wisconsin—Madison, Madison, Wisconsin A step-wise systematic approach can be used to determine the etiology and proper management of acid-base disorders. The objectives of this article are to: (1) discuss the physiologic processes in- volved in acid-base disturbances, (2) identify primary and secondary acid-base disturbances based upon arterial blood gas and laboratory measurements, (3) utilize the anion gap for diagnostic pur- poses, and (4) outline a stepwise approach for interpretation and treatment of acid-base disorders. Case studies are used to illustrate the application of the discussed systematic approach. KEYWORDS: acid-base J Pediatr Pharmacol Ther 2004;9:235-42 Although acid-base disorders are frequently terms of H+, but due to confusing terminology it encountered in hospital and ambulatory care set- was proposed to convert H+ terminology to pH.1 tings, they are often considered the most difficult When taking the negative logarithm of the H+ areas to understand in medicine. Misdiagnosis due to common misconceptions of acid-base ho- ABBREVIATIONS: AG, Anion gap; HCO3, Bicarbonate; CNS, meostasis often delays identification of the pri- Central nervous system; ECF, Extracellular fluid; Hgb, Hemoglobin; ICU, Intensive care unit; THAM, Tromethamine mary disorder, causing a disruption in the deliv- ery of appropriate therapy. By understanding the concentration, pH represents a measure of H+ basic principles of acid-base physiology, the inter- activity. Optimal function for tissues and organs pretation of acid-base data, and the mechanisms within the human body depends on maintaining responsible for acid-base perturbations, the clini- blood pH between 7.10 and 7.60.
    [Show full text]