2 Location-The kidneys are a pair of organs located in the back of the abdomen.- Each kidney is about 4 or 5 inches long -- about the size of a fist.
3 -more specifically in the paravertebral gutter and lie in a retroperitoneal position at a slightly oblique angle. There are two, one on each side of the spine -The left kidney is approximately at the vertebral level T12 to L3 and the right slightly lower.-The right kidney sits just below the diaphragm and posterior to the liver, the left below the diaphragm and posterior to thespleen.
4 The asymmetry within the abdominal cavity caused by the liver typically results in the right kidney being slightly lower than the left, and left kidney being located slightly more medial than the right
6 :Functions- The kidney participates in the excretion of the body wastes-regulating acid-base balance,-regulating electrolyte concentrations . -regulating extracellular fluid volume .- regulation of blood pressure.-Hormone secretion (including- erythropoietin( It stimulates (production of red blood cells) in the bone marrow),-the enzyme renin (Part of the renin-angiotensin-aldosterone system , renin is an enzyme involved in the regulation of aldosterone levels. Calcitriol, the activated form of vitamin D, promotes intestinal absorption of calcium and the renal reabsorption of phosphate.
7 Structure and Function of the Kidney The functional unit of the kidney is the nephronThe major functions of the kidney are to maintain extracellular fluids, to eliminate wastes resulting from normal metabolism, and to excrete xenobiotics and their metabolitesMammalian kidneys have 10,000-1,000,000 nephrons per kidney
9 Structure and Function of the Kidney (cont) The glomerulus yields an ultrafiltrate of plasma that represents 20% of the renal blood flow, ie. 2-3% of cardiac outputEndothelial surface is negatively charged and contains fenestraeThe glomerular basement membrane is sandwiched between the epithelial cells and contains anionic sialoglycoproteins, glycoproteins and collagen IVThe mesangium provides supportThe outer capsule is Bowman’s capsule
10 Structure and Function of the Kidney (cont) The tubule resorbs greater than 99% of the glomerular filtrateThe proximal tubule has extensive resorption and selective secretion (convoluted - S1 and S2, straight - S3). S2 is primary site for low MW protein resorption and S3 is primary site for P450.Thin loop of Henle - resorption of fluidsDistal tubule - resorption of fluids and acid-base balanceCollecting duct - resorption of fluids, antidiuretic hormone and acid-base balance
12 Structure and Function of the Kidney (cont) Produces erythropoietin, which regulates RBC productionHydroxylates 25-OH-cholecalciferol (vitamin D metabolite), to promote bone resorption and calcium and phosphorus absorption from the gutReleases renin to regulate the peripheral renin-angiotensin-aldosterone system (juctaglomerular apparatus)
13 Assessment of Kidney Function: Morphologic Evaluation UrinalysisGross evaluation of the kidney at necropsyHistopathology of the kidneyElectron microscopy of the kidney
14 Assessment of Kidney Function: Urinalysis Proteinuria - indicates glomerular damageGlycosuria - indicates tubular damageUrine volume and osmolaritypHEnzymes - indicates tubular damageMicroscopic examination - casts, crystals, bacteria, etc.
15 Assessment of Kidney Function: Blood Chemistries Blood urea nitrogen (BUN)CreatinineElectrolytes - Ca, Mg, K, PGlomerular filtration rate - determines the clearance of inulin, creatinine and BUNRenal clearance - measures the clearance of p-aminohippuric acid by filtration and secretion
16 Glomerular Disease: Toxicities due to Alteration of Anionic Charge Hexadimethrine - polycationic molecule reduces anionic charge, which permits escape of anionic molecules such as albumin and IgGPolynucleoside of puromycin - damages epithelial foot processes
17 Glomerular Disease: Immune Complex Disease Anti-GBM mediated glomerulonephritis is induced by heterologous antibodiesAntibodies due to exogenous antigens - cationized molecules such as lysozyme, IgG and BSA bind to anionized surfaces; Concanavalin A binds to sugars in the GBM
18 Glomerular Disease: Immune Complex Disease (cont) Deposition of circulating immune complexesDrug or toxin-induced T-cell dependent polyclonal B-cell activation - mercury in Brown Norway ratsUnknown mechanism - gold salts, D-penicillamine, hydralazineAntibodies to heterologous proteins - safety evaluations of recombinant proteins in laboratory animals
20 Haloalkane NephrosisChloroform is metabolized by P450 to an electrophile, phosgene, which is a potent cytotoxicant.Carbon tetrachloride is metabolized to free radicals and phosgene.P450 is localized in the proximal tubule.This results in nephrosis with necrosis, enzyme, glucose and protein excretion in urine, and increased BUN and creatinine concentrations in serum.
21 Haloalkene Nephrotoxicity 1,1-Dichloroethylene, trichloroethylene and tetrachloroethylene are metabolized by P450 to electrophilic metabolites and or free radicals.These metabolites can be cytotoxic and/or genotoxic.Nephrotoxicity is exacerbated when glutathione is depleted.
22 Glutathione-mediated Nephrosis Glutathione conjugates of haloalkanes can form episulfonium ions.Primary route for 1,2-dichloroethane, 1,2-dibromoethane and 1,2-dibromo-3-chloro-propane.These can alkylate macromolecules and cause cytotoxicity and genotoxicity.
23 Cystine Conjugate -lyase Activation Stable cystine conjugates from glutathione can be formed in the liver from trichloro-ethylene, tetrafluoroethylene and hexa-chlorobutadiene and transported to the kidney.They are further metabolized by -lyase in the kidney to generate reactive thiols.
24 Dialysis unit Indications of dialysis in acute renal failure (ARF) is a process for removing waste and excess water from the blood, and is used primarily to provide an artificial replacement for lost kidney function in people with renal failureIndications of dialysis in acute renal failure (ARF)-Severe fluid overload-Refractory hypertension-Uncontrollable hyperkalemia-Nausea, vomiting, poor appetite, gastritis with hemorrhageLethargy, malaise, somnolence, stupor, coma, delirium, asterixis, tremor, seizures,
25 -Pericarditis (risk of hemorrhage or tamponade) -bleeding diathesis (epistaxis, gastrointestinal (GI) bleeding and etc.)-Severe metabolic acidosis- Intoxication, that is, acute poisoning with a dialysable drug, such as lithium, or aspirin.-Blood urea nitrogen (BUN) > 70 – 100 mg/dl
26 Indications of dialysis in chronic renal failure (CRF) -Pericarditis- Fluid overload or pulmonary edema refractory to diuretics-Accelerated hypertension poorly responsive to antihypertensives-Progressive uremic encephalopathy or neuropathy such as confusion, asterixis,-myoclonus, wrist or foot drop, seizures-Bleeding diathesis attributable to uremia
29 the patient's blood is pumped through the blood compartment of a dialyzer, exposing it to a partially permeable membraneBlood flows through the dialyzer, dialysis solution flows around the outside of the fibers, and water and wastes move between these two solutions by applying negative pressure ,The cleansed blood is then returned via the circuit back to the body
30 Advantages Disadvantage four dialysis-free days a week. If you travel to another country, you will have to pre-arrange access to dialysis facilitiesFacilities are widely available.Trained professionals are with you at all times.You can get to know other patients.You don’t have to have a partner or keep equipment in your home. your diet and the amount of fluid that you drink needs to be restrictedYou are advised not to drink more than a couple of cups of fluid a dayYou have to avoid foods that are high in potassium
32 In peritoneal dialysis, a sterile solution containing glucose is run through a tube into the peritoneal cavity, the abdominal body cavity around theintestine, where the peritoneal membrane acts as a partially permeable membrane The dialysate is left there for a period of time to absorb waste products, and then it is drained out through the tube and discarded.This cycle or "exchange" is normally repeated 4-5 times during the day, (sometimes more often overnight with an automated system)
33 Advantages Disadvantage - regular visits to a dialysis unit are not required and, in the case of home haemodialysis, there is no need to have a bulky machine installed in your houseyou need to perform it every day, whereas haemodialysis is usually only performed three days a week.major disadvantage of peritoneal dialysis is that your risk of developing peritonitis (infection of the peritoneum) is increased. more freedom to travel compared with haemodialysis patients.Peritonitis causes symptoms that include:abdominal painvomitingchills (episodes of shivering and cold)fewer restrictions on diet and fluid intake compared with haemodialys reduction in protein levels, which can lead to a lack of energy and in some cases malnutrition.
34 HemofiltrationHemofiltration is a similar treatment to hemodialysis, but it makes use of a different principle.The blood is pumped through a dialyzer or "hemofilter" as in dialysis, but no dialysate is used.- A pressure gradient is applied; as a result, water moves across the very permeable membrane rapidly, "dragging" along with it many dissolved substances, including ones with large molecular weights, which are not cleared as well by hemodialysis.Salts and water lost from the blood during this process are replaced with a "substitution fluid" that is infused into the extracorporeal circuit during the treatment.
35 HemodiafiltrationHemodiafiltration is a term used to describe several methods of combining hemodialysis and hemofiltration in one process.
36 Intestinal dialysisIn intestinal dialysis, the diet is supplemented with soluble fibres such as acacia fibre, which is digested by bacteria in the colon.This bacterial growth increases the amount of nitrogen that is eliminated in fecal wasteAn alternative approach utilizes the ingestion of 1 to 1.5 liters of non-absorbable solutions of polyethylene glycol or mannitol every fourth hour.
37 Electric cardioversion a medical procedure by which an abnormally fast heart rate or cardiac arrhythmia is converted to a normal rhythm, using electricity
38 The purpose of the cardioversion is to interrupt the abnormal electrical circuit(s) in the heart and to restore a normal heartbeat.The delivered shock causes all the heart cells to contract simultaneously, thereby interrupting and terminating the abnormal electrical rhythm (typically fibrillation of the atria) without damaging the heart.
39 Indications: two electrode pads are used These are connected by cables to a machine which has the combined functions of an ECG display screen and the electrical function of a defibrillatorIndications:- Synchronized electrical cardioversion is used to treat hemodynamically significant supraventricular tachycardias, including atrial fibrillation and atrial flutter. It is also used in the emergent treatment including ventricular tachycardia, when a pulse is present.-Pulseless ventricular tachycardia and ventricular fibrillation are treated with unsynchronized shocks referred to as defibrillation.
41 Ventialtora machine designed to mechanically move breatheable air into and out of the lungs, to provide the mechanism of breathing for a patient who is physically unable to breathe, or breathing insufficiently.
42 Indications : -Acute lung injury (including ARDS, trauma) - Apnea with respiratory arrest, including cases from intoxication-Chronic obstructive pulmonary disease (COPD)-Acute respiratory acidosis with partial pressure of carbon dioxide (pCO2) > 50 mmHg and pH < 7.25, which may be due to paralysis of the diaphragm due to Guillain-Barré syndrome,Myasthenia Gravis, spinal cord injury, or the effect of anaesthetic and muscle relaxant drugs-Increased work of breathing as evidenced by significant tachypnea, retractions, and other physical signs of respiratory distressLateral Sclerosis
43 -Hypoxemia with arterial partial pressure of oxygen (PaO2) < 55 mm Hg with supplemental fraction of inspired oxygen (FiO2) = 1.0-Hypotension including sepsis, shock, congestive heart failureNeurological diseases such as Muscular Dystrophy and Amyotrophic
44 Disadvantages:It carries many potential complications including pneumothorax, airway injury, alveolar damage, and ventilator-associated pneumonia.It is used to support a single failing organ system (the lungs) and cannot reverse any underlying disease process (such as terminal cancer)
45 Cardiac Assist Devices Wayne E. Ellis, Ph.D., CRNA
47 History First pacemaker implanted in 1958 First ICD implanted in 1980 Greater than 500,000 patients in the US population have pacemakers115,000 implanted each year
48 Pacemakers Today Single or dual chamber Multiple programmable features Adaptive rate pacingProgrammable lead configuration
49 Internal Cardiac Defibrillators (ICD) Transvenous leadsMultiprogrammableIncorporate all capabilities of contemporary pacemakersStorage capacityHave multiple Tachycardia zones with appropriate therapyRecords adverse events and treatment
50 Temporary Pacing Indications Routes = Transvenous, transcutaneous, esophagealUnstable bradydysrhythmiasAtrioventricular heart blockUnstable tachydysrhythmias*Endpoint reached after resolution of the problem or permanent pacemaker implantationTransvenous optimal. With transcutaneous AV capture happens simultaneously. With esophageal, possibly only atrial capture .
51 Permanent Pacing Indications Chronic AVHBChronic Bifascicular and Trifascicular BlockAVHB after Acute MISinus Node DysfunctionHypersensitive Carotid Sinus and Neurally Mediated SyndromesMiscellaneous Pacing Indications
52 Chronic AVHB Especially if symptomatic Pacemaker most commonly indicated for:Type 2 2ºBlock occurs within or below the Bundle of His3º Heart BlockNo communication between atria and ventricles
53 Chronic Bifascicular and Trifascicular Block Differentiation between uni, bi, and trifascicular blockSyncope common in patients with bifascicular blockIntermittent 3º heart block commonBlock in the conduction systems below the Bundle of His ( in the bundle branches)Right bundle branch, and anterior and posterior fascicles of left bundle branch
54 AVHB after Acute MI Incidence of high grade AVHB higher Indications for pacemaker related to intraventricular conduction defects rather than symptomsPrognosis related to extent of heart damage
55 Sinus Node Dysfunction Sinus bradycardia, sinus pause or arrest, or sinoatrial block, chronotropic incompetenceOften associated with paroxysmal SVTs (bradycardia-tachycardia syndrome)May result from drug therapySymptomatic?Often the primary indication for a pacemakerChronotropic incompetence is known as a deficient rate response or stress or exerciseSymptomology determined with ambulatory monitoringPacemaker does not necessarily improve survival. Dual chamber pacing improves survival greater than ventricular pacing alone.
56 Hypersensitive Carotid Sinus Syndrome • Syncope or presyncope due to an exaggerated response to carotid sinus stimulation• Defined as asystole greater than 3 sec due to sinus arrest or AVHB, an abrupt reduction of BP, or bothDecreased blood pressure due to vasodilationPure cardioinhibitory response, pacing helpsMost people have a mixed response and attention must be given to both components.
57 Neurally Mediated Syncope 10-40% of patients with syncopeTriggering of a neural reflexUse of pacemakers is controversial since often bradycardia occurs after hypotensionIn a recent study, a 85% reduction in risk of recurrent syncope in patients randomized to dual chamber pacing
58 Miscellaneous Hypertrophic Obstructive Cardiomyopathy Dilated cardiomyopathyCardiac transplantationTermination and prevention of tachydysrhythmiasPacing in children and adolescentsDual chamber pacemaker with a short atrioventricular delay reduces the magnitude of left ventricular outflow tract obstructionPacemakers may help by changing the contraction pattern of the ventriclealleviates symptomsImprove hemodynamics using a dual-chamber pacemaker with short atrioventricular delay2) Timing of atrial contractions, decreases mitral regurgitationHigh incidence of bradydysrhythmias 8-23% after transplant due to SNDA flutter, PSVT, and VT.Pacing in kids for Sinus node dysfunction with symptomatic bradycardia, advanced 2nd or 3rd degree AVHB either congenital or acquired, especially if symptomatic. Consider if rate appropriate for child’s age and consider presence of ventricular dysfunction r/t congenital anomalies. No real rate criteria.
59 Indications for ICDsCardiac arrest due to VT/VF not due to a transient or reversible causeSpontaneous sustained VTSyncope with hemodynamically significant sustained VT or VFNSVT with CAD, previous MI, LV dysfunction and inducible VF or VT not suppressed by a class 1 antidysrhythmic
60 Device Selection Temporary pacing (invasive vs. noninvasive) Permanent pacemakerICDInvasive= epicardial and endocardial or transvenous. Non-invasive= transcutaneous or transesophageal. Temporary a good option to buy time until a permanent pacemaker can be implanted.
61 Pacemaker Characteristics • Adaptive-rate pacemakers•Single-pass lead Systems• Programmable lead configuration• Automatic Mode-Switching• Unipolar vs. Bipolar electrode configuration
62 ICD selection Antibradycardia pacing Antitachycardia pacing Synchronized or nonsynchronized shocks for dysrhythmiasMany of the other options incorporated into pacemakers
63 Approaches to Insertion a. IV approach (endocardial lead)b. Subcostal approach (epicardial or myocardial lead)c. Noninvasive transcutaneous pacingAlternative to emergency transvenous pacing
64 Mechanics Provide the rhythm heart cannot produce Either temporary or permanent Consists of external or internal powersource and a lead to carry the current tothe heart muscle Batteries provide the power source Pacing lead is a coiled wire spring encased in silicone to insulate it from body fluids
65 Unipolar PacemakerLead has only one electrode that contacts the heart at its tip (+) poleThe power source is the (-) polePatient serves as the grounding sourcePatient’s body fluids provide the return pathway for the electrical signalElectromagnetic interference occurs more often in unipolar leads
67 Bipolar PacemakerIf bipolar, there are two wires to the heart or one wire with two electrodes at its tipProvides a built-in ground leadCircuit is completed within the heartProvides more contact with the endocardium; needs lower current to paceLess chance for cautery interference
73 Asynchronous/Fixed Rate Does not synchronize with intrinsic HR Used safely in pts with no intrinsicventricular activityIf pt has vent. activity, it may competewith pt’s own conduction systemVT may result (R-on-T phenomenon)EX: VOO, AOO, DOO
74 Synchronous/Demand Contains two circuits * One forms impulses * One acts as a sensorWhen activated by an R wave, sensing circuit either triggers or inhibits the pacing circuitCalled “Triggered” or “Inhibited” pacersMost frequently used pacerEliminates competition;Energy sparing
75 Examples of Demand Pacemakers DDIVVI/VVTAAI/AATDisadvantage: Pacemaker may be fooled by interference and may not fire
76 Dual Chamber: A-V Sequential Facilitates a normal sequence between atrial and ventricular contractionProvides atrial kick + ventricular pacingAtrial contraction assures more complete ventricular filling than the ventricular demand pacing unitIncrease CO 25-35% over ventricular pacing alone
77 A-V Sequential Disadvantage: More difficult to place More expensive Contraindication: Atrial fibrillation, SVTDeveloped due to inadequacy of “pure atrial pacing”
79 “Pure Atrial Pacing”Used when SA node is diseased or damaged but AV conduction system remains intactProvides atrial kickAtrial kick can add 15-30% to CO over a ventricular pacemakerElectrode in atrium: stimulus produces a P wave
80 Problems with Atrial Pacing Electrode difficult to secure in atriumTends to floatInability to achieve consistent atrial “demand” function
81 Ventricular Pacemakers If electrode is placed in right ventricle, stimulus produces a left BBB patternIf electrode is placed in left ventricle, stimulus produces a right BBB pattern
82 ProgrammabilityCapacity to noninvasively alter one of several aspects of the function of a pacerDesirable since pacer requirements for a person change over timeMost common programmed areasRateOutputAV delay in dual chamber pacersR wave sensitivityAdvantage: can overcome interferencecaused by electrocautery
83 3-Letter or 5-Letter Code Devised to simplify the naming ofpacemaker generators
84 First letter Indicates the chamber being paced A: Atrium V: Ventricle D: Dual (Both A and V)O: None
85 Second Letter Indicates the chamber being sensed A: Atrium V: VentricleD: Dual (Both A and V)O: Asynchronous or does not apply
86 Indicates the generator’s response to a sensed signal/R wave Third LetterIndicates the generator’s response to a sensed signal/R waveI: InhibitedT: TriggeredD: Dual (T & I)O: Asynchronous/ does not apply
87 Fourth Letter Indicates programming information O: No programming P: Programming only for output and/or rateM: MultiprogrammableC: CommunicatingR: Rate modulation
88 Fifth Letter This letter indicates tachyarrhythmia functions B: Bursts N: Normal rate competitionS: ScanningE: ExternalO: None
91 Examples AOO A: Atrium is paced O: No chamber is sensed O: Asynchronous/does not applyVOOV: Ventricle is paced
92 Examples VVI V: Ventricle is the paced chamber V: Ventricle is the sensed chamberI: Inhibited response to a sensed signalThus, a synchronous generator that paces and senses in the ventricleInhibited if a sinus or escape beat occursCalled a “demand” pacer
93 Examples DVI D: Both atrium and ventricle are paced V: Ventricle is sensedI: Response is inhibited to a sensedventricular signalFor A-V sequential pacing in which atria and ventricles are paced. If a ventricular signal, generator won’t fireOverridden by intrinsic HR if faster
94 Examples DDD DOO VAT Greatest flexibility in programming Best approximates normal cardiac response to exerciseDOOMost apparent potential for serious ventricular arrhythmiasVATVentricular paced, atrial sensedShould have an atrial refractory period programmed in to prevent risk of arrhythmias induced by PACs from ectopic or retrograde conductionAV interval is usually milliseconds
95 Other InformationDemand pacer can be momentarily converted to asynchronous mode by placing magnet externally over pulse generator in some pacersDual chamber pacers preferable for almost all patients except those with chronic atrial fibrillation (need a working conduction system)Asynchronous pacer modes not generally used outside the OROR has multiple potential sources of electrical interference which may prevent normal function of demand pacers
96 Other Information VVI: Standard ventricular demand pacemaker DVI: AV pacemaker with two pacing electrodesDemand pacer may be overridden by intrinsic HR if more rapidDemand pacer can be momentarily converted to asynchronous mode by placing magnet externally over pulse generator
97 Sensing Ability of device to detect intrinsic cardiac activity Undersensing: failure to senseOversensing: too sensitive to activity
98 Undersensing: Failure to sense Pacer fails to detect an intrinsic rhythmPaces unnecessarilyPatient may feel “extra beats”If an unneeded pacer spike falls in the latter portion of T wave, dangerous tachyarrhythmias or V fib may occur (R on T)TX: Increase sensitivity of pacer
99 OversensingPacer interprets noncardiac electrical signals as originating in the heartDetects extraneous signals such as those produced by electrical equipment or the activity of skeletal muscles (tensing, flexing of chest muscles, SUX)Inhibits itself from pacing as it would a true heart beat
100 OversensingOn ECG: pauses longer than the normal pacing interval are presentOften, electrical artifact is seenDeprived of pacing, the patient suffers CO, feels dizzy/light-headedMost often due to sensitivity being programmed too highTX: Reduce sensitivity
101 CaptureDepolarization of atria and/or ventricles in response to a pacing stimulus
102 Noncapture/Failure to Capture Pacer’s electrical stimulus (pacing) fails to depolarize (capture) the heartThere is no “failure to pace”Pacing is simply unsuccessful at stimulating a contractionECG shows pacer spikes but no cardiac response CO occursTX: threshold/output strength or duration
103 Pacer Failure A. Early B. Failure > 6 months electrode displacement/breakageB. Failure > 6 monthsPremature battery depletionFaulty pulse generator
104 Pacer Malfunctions per ECG Failure to capture Failure to sense Runaway pacemaker
106 EKG Evaluation Capture: Should be 1:1 (spike:EKG complex/pulse) *Not helpful if patient’s HR is >pacer rate if synchronous type
107 EKG Evaluation Proper function of demand pacer Confirmed by seeing captured beats on EKG when pacer is converted to asynchronous modePlace external converter magnet over generatorDo not use magnet unless recommended
108 CAPTURE Output: amt of current (mAmps) needed to get an impulse Sensitivity: (millivolts); the lower the setting, the more sensitive
109 Anesthesia for Insertion MACTo provide comfortTo control dysrhythmiasTo check for proper function/captureHave external pacer/Isuprel/Atropine readyContinuous ECG and peripheral pulsePulse ox with plethysmography to see perfusion of each complex(EKG may become unreadable)
111 Interference Things which may modify pacer function: Sympathomimetic amines may increase myocardial irritabilityQuinidine/Procainamide toxicity may cause failure of cardiac capture K+, advanced ht disease, or fibrosis around electrode may cause failure of cardiac capture
112 Anesthesia for Pt with Pacemaker a. Continuous ECG and peripheral pulseb. Pulse ox with plethysmography tosee perfusion of each complex(EKG may become unreadable)c. Defibrillator/crash cart availabled. External pacer availablee. External converter magnet available
113 Anesthesia for Pt with Pacemaker If using Succinylcholine, consider defasciculating dose of MRFasciculations may inhibit firing due to the skeletal muscle contractions picked up by generator as intrinsic R wavesPlace ground pad far from generator but close to cautery tipCover pad well with conductive gelMinimizes detection of cautery current by pulse generatorIf patient has a transvenous pacemaker, increased risk of V. fib from microshock levels of electrical current
114 Anesthesia for Pt with Pacemaker Cautery may interfere with pacer:May inhibit triggering (pacer may sense electrical activity and not fire)May inadvertently reprogramMay induce arrhythmias secondary to currentMay cause fixed-rate pacing
123 Settings Gives a shock at 0.1-30 joules Usually 25 joules Takes 5-20 seconds to sense VT/VFTakes 5-15 seconds more to chargesecond delay before next shock is administeredTotal of 5 shocks, then pausesIf patient is touched, may feel a buzz or tingleIf CPR is needed, wear rubber gloves for insulation
124 Tiered TherapyAbility of an implanted cardioverter defibrillator to deliver different types of therapies in an attempt to terminate ventricular tachyarrhythmiasEX of therapies:Anticardiac pacingCardioversionDefibrillationAntibradycardia pacing
125 Anesthesia MAC vs General Lead is placed in heart Usually general due to induction of VT/VF so AICD can be checked for performanceLead is placed in heartGenerator is placed in hip area or in upper chest
126 VADs Ventricular assist devices Implantable pumps used for circulatory support in pts with CHFBlood fills device through a cannulation site in V or ADiaphragm pumps blood into aorta or PASet at predetermined rate (fixed) or automatic (rate changes in response to venous return)
127 Electromagnetic Interference on Pacers and AICDs ElectrocauteryMay inhibit or trigger outputMay revert it to asynchronous modeMay reprogram inappropriatelyMay induce Afib or VfibMay burn at lead-tissue interface
128 Electromagnetic Interference on Pacers and AICDs DefibrillationMay cause permanent damage to pulse generatorMay burn at lead-tissue interfaceRadiation TherapyMay damage metal oxide silicon circuitryMay reprogram inappropriately
129 Electromagnetic Interference on Pacers and AICDs PET/CT (Contraindicated)May damage metal oxide silicon circuitryMay reprogram inappropriatelyMRI (Contraindicated)May physically move pulse generatorMay give inappropriate shock to pt with AICDPNSsMay cause inappropriate shock or inhibitionTest at highest output setting
130 Deactivating a Pacemaker Deactivate to prevent inappropriate firing or inhibitionCan be deactivated by a special programmer/wand or by a magnet placed over generator for 30 secondsPut in asynchronous mode or place external pacer on patient
131 If Pt has a Pacemaker/AICD Not all models from a certain company behave the same way with magnet placement !For all generators, call manufacturerMost reliable method for determining magnet response ! !
132 Coding Patient If patient codes, do not wait for AICD to work Start CPR & defibrillate immediatelyPerson giving CPR may feel slight buzzA 30-joule shock is < 2 j on pt’s skinExternal defibrillation will not harm AICDChange paddle placement if unsuccessful attemptTry A-P paddle placement if A-Lat unsuccessful
133 Pts with Pacemakers/AICDs/VADs Obtain information from patient regarding deviceAsk how often patient is shocked/dayHigh or low K+ may render endothelial cells more or less refractory to pacingA properly capturing pacemaker should also be confirmed by watching the EKG and palpating the patient’s pulse
134 Anesthetic Considerations Avoid SuccinylcholineKeep PNS as far from generator as possibleHave backup plan for device failureHave method other than EKG for assessing circulationHave magnet available in OR
135 Electrocautery UsePlace grounding pad as far from generator as possiblePlace grounding pad as near to surgical field as possibleUse bipolar electrocautery if possibleHave surgeon use short bursts of electrocautery(<1 sec, 5-10 seconds apart)Maintain lowest possible current
136 Electrocautery UseIf cautery causes asystole, place magnet over control unit & change from inhibited to fixed modeChange back afterwardsBe alert for R on T phenomenon
137 Postoperative Considerations Avoid shiveringHave device checked and reprogrammed if questions arise about its function
138 Examples of Rhythms Sensing Patient’s own beat is sensed by pacemaker so does not fire
139 Examples of Rhythms Undersensing Pacemaker doesn’t sense patient’s own beat and fires (second last beat)
140 Examples of Rhythms Oversensing Pacemaker senses heart beat even though it isn’t beating. Note the long pauses.
141 Examples of Rhythms Capture Pacemaker output (spike) is followed by ventricular polarization (wide QRS).
142 Examples of Rhythms Noncapture Pacer stimulus fails to cause myocardial depolarizationPacer spike is present but no ECG waveformOversensing-Fails to fireUndersensing-Fails to senseECGFires but fails to capturePacer spikes after theQRS
143 Examples of Rhythms100 % Atrial Paced Rhythm with 100% Capture
144 Examples of Rhythms100% Ventricular Paced Rhythm with 100% Capture
145 Examples of Rhythms100% Atrial and 100% Ventricular Paced Rhythm with 100% Capture
146 Examples of Rhythms50% Ventricular Paced Rhythm with 100% Capture
147 Examples of Rhythms25% Ventricular Paced Rhythm with 100% Capture (Note the sensing that occurs. Pacer senses intrinsic HR and doesn’t fire).
148 Examples of RhythmsAICD Shock of VTConverted to NSR
152 References Moser SA, Crawford D, Thomas A. AICDs. CC Nurse. 1993;62-73.Nagelhaut JJ, Zaglaniczny KL. NurseAnesthesia. Philadelphia: Saunders.1997.Ouellette, S. (2000). Anesthetic considerations in patients with cardiac assist devices. CNRA, 23(2), 9-20.Roth, J. (1994). Programmable and dual chamber pacemakers: An update. Progress in anes thesiology, 8, chapter 17. WB Saunders.
153 Pacemaker a medical device that uses electrical impulses, delivered by electrodes contacting the heart muscles, to regulate the beating of the heart , and maintain an adequate heart rate, either because of the heart's native pacemaker is not fast enough, or there is a block in the heart's electrical conduction system