Renal and Coagulation Flashcards
What are some basic renal questions you ask?
Have you ever had any kidney problem?
Have you ever had kidney failure, dialysis, or more than two kidney infections?
Have you ever had kidney stones?
Are you undergoing dialysis for kidney problems?
Have you had changes in bowel or bladder function in the last year?
Has your appetite for food changed in the last year? (Voluntary avoidance of foods having a high protein content is a subtle sign of renal disease.)
Dialysis will be required in the following situations:
Oliguria Fluid overload Hyperkalemia Severe acidosis Metabolic encephalopathy Pericarditis Coagulopathy Refractory GI symptoms Drug toxicity
When should dialysis occur, and what should you note?
Optimization, optimization, optimization!
Dialysis should occur day of surgery or day before surgery
Review dialysis flowsheet if available
Amount of fluid “taken off”
Pre and post dialysis weights compare with day of surgery weight
Note POST dialysis chemistry! Serum K < 5.5 mEq/L
What meds get cleared by dialysis and whens should drugs be given?
General rule: scheduled doses of drugs are administered after dialysis
Low-molecular weight, water soluble, non protein bound drugs are readily cleared by dialysis
What are neurological s/s of renal failure?
Uremic Encephalopathy Asterixis Myoclonus Lethargy Confusion Seizures Coma Autonomic Neuropathy Peripheral Neuropathy
What should you look for s/p dialysis?
Disequilibrium syndrome (dialysis related) transient CNS disturbance after rapid decrease in ECF osmolality compared with ICF osmolality Dementia
Hematological assessment?
Anemia typical Hgb = 6-8 g/dL
Decreased erythropoietin production
Decreased RBC production & cell life span
GI blood loss, hemodilution, bone marrow suppression
Excess PTH replaces bone marrow with fibrous tissue
Most patients tolerate the anemia well (exception CAD)
Increased 2,3- DPG (diphosphoglycerate)
Metabolic acidosis also favors rightward shift
What happens with platelets, WBC, dialysis?
Impaired platelets (qualitative) – prolonged bleeding time
Decreased plt factor III activity
Decreased adhesiveness & aggregation
Impaired WBC function – infections
Release of defective von Willebrand factor
Dialysis = Residual anticoagulation VS promotion of hypercoagulable state
Hypocomplementemia with dialysis
Cardiovascular effects?
↑ Cardiac output
compensation for ↓ O2 carrying capacity
HTN – Na retention, renin-angiotensin activation
Left ventricular hypertrophy common
CHF with pulmonary edema after limits of compensation reached
Deposition of calcium - in the conduction system & on the heart valves
Arrhythmias – electrolyte imbalances
Uremic pericarditis – can be asymptomatic, chest pain, tamponade, usually secondary to inadequate dialysis
Accelerated CAD, PVD
Fluid balance effects
Fluid overload VS intravascular depletion status post dialysis/ aggressive diuretic therapy
Body weight
VS (orthostatic hypotension & tachycardia)
Atrial filling pressures
Pulmonary effects?
Minute ventilation increased to compensate for metabolic acidosis
Increased pulmonary extravascular water= interstitial edema = widened alveolar/arterial O2 gradient
“Butterfly wings” on CXR secondary to increased permeability of alveolar capillary membrane (edema even with nml pulmonary capillary pressures)
Endocrine effects?
Peripheral resistance to insulin = poor glucose tolerance
Hyperparathyroidism = prone to fractures
Abnormal lipid metabolism = accelerated atherosclerosis
Kidneys do not degrade hormones and proteins normally = increased circulating PTH, insulin, glucagon, GH, LH, PL
Gi/Liver effects?
10-30% of patients will develop GI Hemorrhage
Anorexia
Nausea and Vomiting
Hypersecretion of gastric acid + delayed gastric emptying (autonomic neuropathy)
High incidence of Hep B and C in these pts (multiple transfusions, etc.)
Ascites with dialysis
IMPACT ON DRUGS, and what drugs are contraindicated?
Effects altered due to: Anemia Decreased serum protein Electrolyte abnormalities Fluid retention Abnormal cell membrane activity Drugs ELIMINATED BY KIDNEYS UNCHANGED are CONTRAINDICATED Gallamine, phenobarbital, LMWH
What renal function tests reflect GFR?
Blood Urea Nitrogen (10-20 mg/dl) Plasma Creatinine (0.7-1.5 mg/dl) Creatinine Clearance (110-150 ml/min)
What renal function tests reflect renal tubular function?
Renal Tubular Function
Urine Specific Gravity (1.003-1.030)
Urine Osmolarity (38-140 mOsm/L)
What is normal BUN and what are high levels indicative of?
BUN normal = 10-20 mg/dL
Varies inversely w/GFR & directly w/protein catabolism
>50mg/dl is indicative of a ↓ GFR (in patients with nml diets)
BUN is not a sensitive index b/c urea clearance also depends on the production of urea
BUN can be abnormal despite a normal GFR due to:
High protein diet
GI bleed
Febrile illness
The most common cause of BUN is CHF secondary to the reabsorption of BUN
What is normal creatinine and what are high levels indicative of?
Plasma Cr is a specific indicator of GFR
8 -17 hr lag time after a change in GFR before the ↑ Cr levels are seen.
Suggestive [but not indicative] of Acute Renal Failure.
Usually a 50% ↑ in plasma Cr reflects a corresponding ↓ in GFR.
Skeletal muscle = source of Cr
Elderly patient- Cr levels stay nml constant due to:
↓ muscle mass and GFR
If CR ↑ in the elderly, this may be indicative of renal failure.
Creatinine clearance?
24 hour collection most accurate although 2 hour tests also helpful Creatinine Clearance approximates GFR Normal 100-120ml/min ↓ Renal Reserve 60-100 ml/min Mild Renal Impairment 40-60 ml/min Moderate Insufficiency 25-40 ml/min Renal Failure <10 ml/min
What are common abnormalities regarding lab values?
Assess the adequacy of dialysis Hyponatremia (hypernatremia rare) Hyperkalemia (hypokalemia with dialysis) Metabolic acidois with high anion gap Hypermagnesemia Hypocalcemia (unclear etiology) Hypoalbuminemia (esp. with dialysis) Hyperglycemia (if insulin resistant)
When do you transfuse blood?
Transfuse only when absolutely indicated <6-7g/dL or significant intra-operative blood loss
What is the dose for desmopressin and cryoprecipitate for bleeding times that are prolonged?
Desmopressin (0.3-0.4 mg/kg over 30 min), cryoprecipitate 10 units IV over 30 minutes
What are the labs and tests for cardiac?
EKG: Hyper or hypokalemia Hypocalcemia Ischemia Conduction blocks LVH Echocardiography : Ventricular EF Hypertrophy Wall motion abnormalities Pericardial fluid
What are basic hematologic questions to ask?
Have you ever had a blood problem such as anemia or leukemia
Have you ever had a problem with blood clotting or a serious bleeding problem?
Have you received a blood transfusion since 1979?
Do you use any medications such as aspirin or vitamins such as vitamin E or supplements such as ginseng or garlic known to affect blood clotting? How much? How often? When did you last use such?
Has a family member or blood relative ever had a serious bleeding problem?
Have you ever had prolonged or unusual bleeding from cuts, nosebleeds, minor bruises, tooth extractions, or surgery?
Have you ever had excessive bleeding that required blood transfusion?
What is the CAO2 formula?
CaO2=(Hgb x 1.39)SaO2 + PaO2(0.003) 1.39 = O2 bound to hemoglobin SaO2= saturation of hemoglobin with O2 PaO2= arterial partial pressure of oxygen 0.003 = dissolved oxygen ml/mmHg/dl
What compensations occur for the patient with chronic anemia?
↓ SVR
↑ 2,3-DPG- major compensatory mechanism till 7 g/dl (Alters O2 binding- Right shift->↓Hgb affinity for O2)
↑ CO
↑ plasma Volume
Redistribution of blood flow to organs with higher extraction ratio
↑Extraction ratio in vascular beds
What is the definition of anemia?
Anemia according to WHO= Hemoglobin <12 g/dl (female) 13g/dl (males)
Hgb and Hct are relative measurements
What factors are considered in developing a minimum acceptable Hb and Hct?
Duration Acute vs. chronic anemia Etiology Intravascular fluid volume Urgency of surgery Anticipated blood loss during surgery Co-existing disease Cardiovascular, cerebrovascular, and lung disease, PVD
What is the threshold for transfusion?
Prior to 1980s-10/30 rule…AIDS
Clinical decision to transfuse is based on the risk:benefit
Minimum acceptable H & H individualized
American College of Surgeons- transfuse only if symptomatic
Always focus on the cause!
American Assoc of Blood Banks- Hgb of 8 g/dl threshold in healthy individuals
NIH Consensus Conference on Perioperative transfusions- 7g/dl
ASA Task Force on Blood Component Therapy – transfuse based on risks from complications of inadequate O2 delivery
What are concerns with hemolytic anemia?
Perioperative risks and concerns
↑ risk of tissue hypoxia
Previous splenectomy may ↑ risk of perioperative infection
Erythopoietin is often prescribed for 3 days preoperatively
Acute drops in Hb below < 8 g/dl and chronic reductions to below 6 g/ dl should be considered for transfusion
What are sickle cell traits vs. disease?
Trait: 8% African Americans are Heterozygous carriers (hgb genotype AS- 40% of their Hgb is S)
Do not have anemia and do not need Rx
5% at some time have hematuria & difficulty concentrating urine-not significant clinically
Do not require pre-op transfusions
Disease: RBCs homozygous for Hgb S contain 70-98% Hgb type S
Anemia well tolerated
O2 delivery to tissues due to right shift of oxyhemoglobin dissociation curve with Hgb S
Sickle cell complications?
Patients have a 30% overall complication rate *
Stroke
Heart failure and Pulmonary HTN
MI
Hepatic or splenic sequestration
Renal failure
* So what are your pre-operative assessment priorities?
Preoperative preparations for sickle cell disease?
Procedures intermediate to high risk conservative transfusions preoperatively to Hgb10 g/dl = Hct of 30%
Low risk procedures- no benefit
Emergency surgery- High risk for postop complications-optimal transfusion support
Venous access may be difficult to obtain
Preoperative hydration for 12 hours prior to surgery
Premed-Avoid respiratory depression = acidosis
Avoid all situations leading to _____? in sickle cell.
Hypoxemia
Hypovolemia
Stasis
What do you do to avoid sickle cell crisis?
Maintain normothermia = cold patient vasoconstricts = sickling
Hydration- avoid dehydration hemoconcentration = ↑ sickling
Maintain oxygenation
Acidosis promotes sickling
Positioning prevent stasis
What are preoperative risks for thalassemia?
High-output CHF common with severe anemia
Compensatory RBC production = craniofacial deformity and overgrowth of the maxillae increase challenge of DVL
Complications of iron loading from chronic transfusions
Diabetes (Blood glucose monitoring)
Adrenal insufficiency (↓ response to vasopressors)
Liver dysfunction & Coagulation abnormalities
Hypothyroidism & hypoparathyroidism
Arrhythmias (cardiac hemochromatosis) (ECG)
Heart failure (cardiac hemochromatosis) (ECHO)
Hypersplenism can result in thrombocytopenia and ↑ risk of infection
Potential difficult airway 2° to maxillary deformities
Cardiac arrhythmias of HF
Coagulopathy
Preoperative considerations for aplastic anemia?
CBC results important – neutrophil, RBC and platelet counts can be extremely low! May need pre-op transfusion
Know pre-op medications (many are on steroids) which means????
Airway hemorrhage possible with DVL? What does this mean to you?
Other perioperative risks and concerns
Infection
Hemorrhage (GI & Intracranial)
LV dysfunction 2° high output state and fluid overload
Sepsis
Co-existing congenital abnormalities
Fanconi anemia
Difficulty cross-matching blood products after multiple transfusions
Reverse isolation
Neutropenia & severe co-existing congenital heart disease prophylactic ABX
Steroid “stress” dose
Avoid nasal intubation
What is porphyria?
Porphyrias are a group of inborn errors of metabolism = overproduction of porphyrins
Porphyrins are essential for many vital processes including O2 transport and storage (heme is a porphyrin)
A feedback loop is involved in the enzymatic pathway producing prophyrins
Any increase in heme requirements results in an accumulation of pathway intermediates preceding the enzyme block
What activates porphyria and what are the attack symptoms?
Activation of the disease via drugs, diet, and steroid hormones
Drugs trigger an attack by inducing ALA synthetase or interfering with negative feedback control in final common pathway
Attack Symptoms: severe abd pain/GI disturbance ANS instability electrolyte disturbances CNS disturbances life threatening muscle weakness
What drugs are unsafe for porphyria?
Barbiturates Sulfonamide antibiotic Alcohol Diazepam Phenytoin Etomidate ?????? Nifedipine (probably avoid) Ketorolac (probably avoid)
What drugs are safe for porphyria?
Opioid analgesics Propofol Ketamine (probably safe) Aspirin Acetaminophen PCN Glucocorticoids Insulin Atropine
What factors are absent in Hemophilia A
Factor VIII = abnl PTT
Treatment: Factor VIII infusion; Desmopressin
What factors are absent in Hemophilia B
Factor IX = abnl PTT
Treatment: Factor IX
What factors are absent in Von Willebrand’s?
vWF & VIII= prolonged bleeding time
Treatment: Cryo and Desmopressin
