Renal Obesity and GI For the Written Boards

Renal, Obesity & GI For the Written Boards Playing the role of Kyle Berry, MD today will be... Rich Serianni, MD LCDR, MC, USN Objectives  To cover as much testable material as possible based on the ABA content outline and key word phrases for the written boards  Renal  Obesity  GI What percentage of cardiac output goes to the kidneys A.  B.  C.  D.  E.  5% 10% 20% 30% 40% The nerve most likely to be injured in the lithotomy position is the A.  B.  C.  D.  E.  Obturator nerve Femoral nerve Saphenous nerve Peroneal nerve Tibial nerve A patient with CRF misses dialysis on DOS. Expected abnormalities include all of the following except A.  B.  C.  D.  E.  Metabolic acidosis Hyperkalemia Uremia Thrombocytopenia Hypervolemia During a TURP under spinal, pt. complains of nausea and inability to see. The most likely cause is A.  B.  C.  D.  E.  Hypothermia Glycine toxicity Bladder perforation Hemorrhage Bacteremia What is the sensory level required for a TURP A. T4  B. T6  C. T8  D. T10  The circulation to the kidney is A. Autoregulated over a mean arterial pressure range of about 60-150mmHg  B. Not regulated by neural factors  C. Innervated by sympathetic nerves originating in T2-T3  D. Not affected by epinephrine  E. Constricted by prostaglandin E2  Anatomy and Physiology of the Kidney The functional unit of the kidney is the nephron  There are 1-2 million nephrons in each kidney  The number of nephrons does not change after birth  Anatomy and Physiology of the Kidney  The kidney is 0.5% of body weight but receives 20% of the CO  2/3 to renal cortex & 1/3 to renal medulla  RBF and GFR is autoregulated  Between MAP 60-160  Maintained by afferent arteriolar vascular tone  Below MAP 60 and above MAP 150 is pressure dependent Anatomy and Physiology of the Kidney  The factors that affect GFR include output  Permeability  SNS  Renin  Cardiac  Renin is a proteolytic enzyme synthesized by juxtaglomerular cells of afferent arterioles Anatomy and Physiology of the Kidney Hypotension/hypovolemia and SNS stimulation stimulate renin secretion  Renin converts angiotensinogen to angiotensin I  Angiotensin I is converted to angiotensin II by ACE (in the lungs)  Angiotensin II    Stimulates adrenal cortex to release aldosterone Is a potent arterial vasoconstrictor Anatomy and Physiology of the Kidney  Aldosterone is a steroid hormone that is secreted by the adrenal cortex in response to:  Hypokalemia  Angiotensin  ACTH II  What is the ultimate result of this cascade that started with hypotension?  Increasing BP by increasing the blood volume Anatomy and Physiology of the Kidney The normal rate of glomerular filtration is 125ml/min  Approximately 90% of the filtered fluid is reabsorbed and returned to the circulation  The GFR has to decrease by 75% and more than 50% of nephrons must be nonfunctional before renal function tests become abnormal  Anatomy and Physiology of the Kidney  Creatinine clearance is the best estimate of the GFR CrCl=[(140-age)x(wt)]/(72xCr)  For woman multiply by 0.85   The normal and abnormal creatinine clearance values Normal  Renal impairment  Renal failure  ESRD  >100(ml/min) 50 <25 <10 Anatomy and Physiology of the Kidney  The principle behind calculating the fractional extretion of Sodium  During dehydration or hypovolemia renal tubules intensely reabsorb sodium. In acute renal failure the ability to reabsorb sodium is lost.  FENa is calculated by obtaining simultaneous urine and plasma samples   The interpretation of the results   FENa=(UNa/PNa)/(UCr/PCr) <1% (Dehydration or hypovolemia) - Prerenal >2% (Acute renal failure) - Renal Renal Failure  Perioperative oliguria (urine output less than 0.5ml/kg/h) can be classified as  Prerenal  Renal  Postrenal Perioperative oliguria Postrenal – mechanical problem  Prerenal – Most common cause and is secondary to decreased RBF (hypovolemia, CHF, sepsis)  Renal – ATN is the most common cause of intrinsic renal oliguria  Chronic Renal Failure  The manifestations of chronic renal failure include        Metabolic: (hyperkalemia, hyperphosphatemia, hypocalcemia, hypermagnesemia, hypoalbuminemia) Hematologic: (Anemia, coagulopathy) CV: (Increased CO, Uremic pericarditis) Pulm: (Metabolic acidosis, pulmonary edema) Endocrine: (Osteoporosis) GI: (Delayed gastric emptying, Increased gastric acid secretion) Neuro: (Uremic encephalopathy) Chronic renal failure Sepsis is the most common cause of death  Coagulopathy is due to poor platelet aggregation. PT and PTT usually remain normal   Dialysis will correct Administration of recombinant erythropoietin is effective at correcting the anemia of ESRD  Anemia is secondary to decreased erythropoietin  Chronic Renal Failure  Is it acceptable to use succinycholine in patients with chronic renal failure? as long as potassium is not elevated  Potassium release is not exaggerated in pt’s with chronic renal failure  Yes, Dialysis  The indications for dialysis include overload  Hyperkalemia  Severe acidosis  Coagulopathy  Pericarditis  Encephalopathy/seizures  Drug toxicity  Fluid TURP (Irrigating Solutions) Glycine can act as an inhibitory neurotransmitter in the retina and cause transient blindness  Sorbitol and Mannitol are sugars that provide an excellent culture medium and introduce the risk of bacterial contamination  TURP Syndrome=Water Intoxication Syndrome  Manifestations  Hypervolemia Htn  Pulmonary edema  CHF    Hyponatremia Hypoosmolality Cerebral edema  Headache, restlessness, seizures  TURP  Spinal anesthesia is often selected for TURP T10 level is required  Ability to recognize changes in mental status  Shoulder pain from perforated bladder  However no evidence of differences in morbidity or mortality when compared to GA A Which of the following respiratory system changes does NOT occur with obesity? A.  B.  C.  D.  E.  Increased 02 consumption Decreased ERV and FRC Decreased closing capacity Reduced chest wall compliance Increased C02 production All of the following CV changes may occur with obesity EXCEPT A.  B.  C.  D.  E.  Htn Increased CO Cardiomegaly Hypovolemia Pulmonary htn Difficulties in treating pt’s with obesity include all of the following except A.  B.  C.  D.  E.  Falsely low BP cuff readings Difficult venous access Difficult intubation Difficult mask ventilation Difficulty with nerve blocks Obesity BMI = wt(kg)/ht(m2)  Obese = BMI >25 or >20% above IBW  Morbidly obese = BMI >35 or 2X IBW  Obesity  Respiratory System      02 consumption and C02 production increase Alveolar ventilation – increased FRC, VC and ERV decreased Closing capacity remains unchanged Restrictive lung disease Obesity  Cardiovascular System       Increased CO (Cardiac index remains normal)  CO increases 0.1L/min for every 1kg adipose tissue Increased blood volume and plasma volume Increased preload and afterload Htn (LVH may result) Pulmonary htn (cor pulmonale) Cardiomegaly Obesity  Pickwickian syndrome    Also known as the obesity-hypoventilation syndrome Hallmarks are alveolar hypoventilation, hypersomnia and obesity Can lead to hypercapnea, respiratory acidosis hypoxemia, polycythemia, pulmonary htn, cor pulmonale, RAD on ECG and increased sensitivity to anesthetics Obesity  GI  Hiatal hernia, GERD, delayed gastric emptying and increased gastric acidity  90% of morbidly obese patients have   Gastric volume >25cc Gastric fluid ph <2.5   Endocrine  Diabetes mellitus (secondary to insulin resistance) DVT Hematologic  Obesity  Airway mask ventilation  Difficult intubation  Aspiration risk is high  Difficult Difficult venous access  Difficulty with regional anesthesia  The liver receives its blood supply from A. Hepatic artery only  B. Portal vein only  C. Both the hepatic artery and the portal vein  D. Vessels that run in the center of the lobules  E. The superior mesenteric artery  The patient with acute viral hepatitis A. Is not effected by surgical procedures  B. Is an acceptable candidate for surgery if liver enzyme elevation is mild  C. Is at high risk for perioperative mortality  D. Should never have general anesthesia  E. Should never receive pentothal  Halothane hepatitis A. Occurs 1 in every million halothane anesthetics  B. Is more common in prepubertal children  C. Is likely an autoimmune response to a neoantigen  D. Is always a mild self-limited disease  All of the following clotting factors are produced in the liver except A.  B.  C.  D.  E.  Factor V Factor VII Factor VIII Factor IX Factor X Hepatic Physiology Only major organ in the body that receives a dual afferent blood supply  2 vessels supplying (hepatic artery and portal vein)     Portal vein = 75% of HBF (55% of 02) Hepatic artery = 25% of HBF (45% of 02) Total hepatic blood flow = 25% of CO 1 vessel draining (portal vein)  Portal venous pressure is normally 7-10mmHg  Hepatic Function Metabolism – Fat, carbs and protein  Protein synthesis – Albumin and all clotting factors (except 8, 3, 4 & 6)  Drug metabolism    Phase I: P-450 oxidation/reduction/hydrolysis Phase II: Conjugation reactions Necessary for absorption of fat soluble vitamins (A,D,E,K)  Bile formation and storage  Liver Function Tests  Few SPECIFIC for liver disease 2 tests often used to assess synthetic function – half life 21 days so normal initially  PT - Measures factor VII which has the shortest half life (4-6hrs) defects will show up quicker  Albumin Halothane Hepatitis    Incidence – 1/35,000  (prepubertal children 1/100,000) Risk: Middle age, obese, female, repeat exposure Pathogenesis  Autoimmune theory  Metabolites bind to hepatic microsomal enzymes and form a neoantigen that induces an autoimmune response Hepatitis due to direct toxicity of metabolites  Direct toxicity theory   Avoid halothane if there is a previous hx of halothane hepatitis