Pacemaker & anesthesia

shenxiu2

Pacemaker & Anesthesia

Types of Pacemakers
1.What is the 5 –letter coding system used to describe cardiac pacemakers?
Most pacemakers are referred to by the first 3 letters of the code.
The first letter indicate the location of the pacing electrode .
The second letter signifies the location of the pacemaker’s sensor.
The third letter is indicative of the mode of activity.
The fourth letter describes programmability .
The fifth letter describes implantable cardioverter- defibrillators ( ICD),

Coding system  of pacemaker　( First 3 letters --  I, II , III,)

I     Chamber paced   O=none ; A=atrium , V=Ventricle ;D=Dual ( A+V)
II    Chamber sensed   O=none; A=Atrium  ,V=Ventricle  , D=Dual ( A+V)
III   Mode of activity    O=none , T= Trigger , I =Inhibit , D=Dual (Ｔ＆Ｉ）

Types of pacemakers
AOO-----Atrial fixed rate(Asynchronous) pacemaker: It paces the atrium regardless of intrinsic cardiac activity.
VOO -----Ventricular fixed rate pacemaker: it paces the ventricle regardless of intrinsic cardiac activity.
AAI - --Atrial demand pacemaker :it senses & paces only in the Atrium; it si inhibited from pacing by intrinsic P waves.
VVI-----Ventricular demand pacemaker: it senses & paces only in the ventricle; intrinsic R waves inhibit it from pacing.
AAT—Atrial triggered pacemaker: it senses & paces in the atrium ; it is triggered to pace by sensing intrinsic ( Nonconducted ) P waves.
VVT ---- Ventricle triggered pacemaker: it senses & paces in the ventricle; it is triggered to pace by sensing intrinsic ( Nonconducted ) R waves.
DVI---sequential pacemaker: it senses only in the ventricle ; it paces the atrium & then the ventricle & is inhibited by intrinsic ventricular depolarization..
VDD----the pacemaker senses in both the atrium & ventricle & paces in the ventricle.

2.What is a fixed rate pacemaker? Give an example.
Known as asynchronous pacemakers. Electrical impulses are delivered at regular pre-set intervals, independent of the patient’s intrinsic heart rate. These pacemakers are good for pacing during bradycardia secondary to new onset third degree AV block. Ventricular tachycardia may result when competition with a patient’s intrinsic rate leads to a
pacing spike that occurs on a T wave.

3. What is a single chamber demand pacemaker?
Demand pacemakers are also known as noncompetitive pacemakers. They stimulate the heart “ On Demand “ only when spontaneous impulses do not occur during a preselected time interval. This type of pacemaker is inhibited by intrinsic R waves when the patient’s own heart rate is greater than the preset rate.

4. Why is it occasionally necessary to convert a demand pacemaker to an asynchronous pacemaker ? How is this accomplished?
A
demand pacemaker amy malfunction because of faulty circuitry, incorrect programming, or extrinsic radiofrequency interference. So it may be  useful to convert the pacemaker to asynchronous mode , so that the myocardium is depolarizes at regular interval & cardiac output is maintained.
Mode conversion may be achieved by reprogramming the pacemaker through an external remote control radio device or by bringing a specially designed magnet in close to the pacemaker. A pacemaker magnet should always be nearby when patients with pacemakers undergo surgical procedures.

5. What is the most common type of pacemaker?
VVI demand pacemaker is the most commonly placed pacemaker today.

6. What is an implantable cardioverter-defibrillator( ICD)?
An ICD continuously monitors the patient’s cardiac rhythm. ICDs are placed in patients prone to ventricular dysrhythmias & in whom medical management has failed. When Ventricular tachycardia or fibrillation is detected, this device will deliver countershocks in an attempt to convert the heart to its baseline rhythm.

Preoperative evaluation in the patient with a pacemaker.

7. What kind of diagnostic information & data from the history & exam are particularly relevant in these patients?
Medical problems including cardiovascular disease.
Cardiac medications.Original indications for placement of the pacemaker.
Whether the patient is experiencing a return of
pre-pacemaker symptoms.
Chest Radiograph ---verify the pacemaker lead continuity, look for signs of congestive heart failure.
Recent ECG---to check the pacemaker spikes.
A recent hematocrit to assess oxygen carrying capacity in patients with cardiac disease.
Serum K+ --to identify acute changes in extracellular K+ concerntration which may affect myocardial sensitivity to pacing.

8. What kind of data should be gathered regarding the pacemaker itself?
The type of pacemaker ( Letter code).
Date of placement.
If no pacemaker identity card , a chest X-ray will reveal the letter code ( which is radiopaque) and also the location of the pacemaker.

9. Do these patients require any type of special monitoring?
The presence of pacemaker is not an indication for invasive manitoring.

Intraoperative management of the patient with a pacemaker
10. Is succinylcholine contraindicated for general anesthetics in patient with pacemaker ?
Fasciculations after the depolaring muscle relaxants may be perceived
by the pacemaker sensor as an intrinsic cardiac impulse. Depending on the type of pacemaker, it may be inhibited from firing an impulse resulting in deleterious reductions in heart rate & cardiac output, even cardiac standstill. A “ defasciculating “ dose of a non depolarizing muscle relaxant should be given 5-10 minutes before succinylcholine is administered. Additionally the pacemaker may be reprogrammed to asynchronous ( VOO ) mode, so that it stimulates the ventricle regardless of intrinsic cardiac activity.

11. How does electrocautery affect pacemaker function?
Electromagnetic interference ( EMI) from electrocautery is probably the most common cause of intraoperative pacemaker failure.
Because the EMI is interpreted as normal intrinsic cardiac activity. Electrocautery will not affect VOO pacemaker . So by applying an external magnet or by reprogramming the pacemaker to asynchronous mode , this problem can be overcomed.
But a magnet should not be used on a multiprogrammable pacemaker. This type of pacemaker can be used even with cautery.

12. What can be done to protect the pacemaker from the untoward effects of EMI ?

• Use bipolar cautery
• Electrocautery energy level should be kept as low as possible.
• 
  Short bursts are safer than continuous activation.
• Current dispersal unit or pad should be placed remote from the pacemaker.

13. Your patient with a pacemaker is found pulseless; ECG demonstrates ventricular tachycardia. The defibrillator is charged & ready to go . Do you proceed with external defibrillation?
Yes. Most pacemaker are constructed with protective circuit designed to withstand external defibrillation. The paddles, however , should not be placed directly over the pacemaker.

----Anesthesia Secrets-------

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25opple

Pacemaker & Anesthesia

Types of Pacemakers
1.What is the 5 –letter coding system used to describe cardiac pacemakers?
Most pacemakers are referred to by the first 3 letters of the code.
The first letter indicate the location of the pacing electrode .
The second letter signifies the location of the pacemaker’s sensor.
The third letter is indicative of the mode of activity.
The fourth letter describes programmability .
The fifth letter describes implantable cardioverter- defibrillators ( ICD),

Coding system  of pacemaker　( First 3 letters --  I, II , III,)

I     Chamber paced   O=none ; A=atrium , V=Ventricle ;D=Dual ( A+V)
II    Chamber sensed   O=none; A=Atrium  ,V=Ventricle  , D=Dual ( A+V)
III   Mode of activity    O=none , T= Trigger , I =Inhibit , D=Dual (Ｔ＆Ｉ）

Types of pacemakers
AOO-----Atrial fixed rate(Asynchronous) pacemaker: It paces the atrium regardless of intrinsic cardiac activity.
VOO -----Ventricular fixed rate pacemaker: it paces the ventricle regardless of intrinsic cardiac activity.
AAI - --Atrial demand pacemaker :it senses & paces only in the Atrium; it si inhibited from pacing by intrinsic P waves.
VVI-----Ventricular demand pacemaker: it senses & paces only in the ventricle; intrinsic R waves inhibit it from pacing.
AAT—Atrial triggered pacemaker: it senses & paces in the atrium ; it is triggered to pace by sensing intrinsic ( Nonconducted ) P waves.
VVT ---- Ventricle triggered pacemaker: it senses & paces in the ventricle; it is triggered to pace by sensing intrinsic ( Nonconducted ) R waves.
DVI---sequential pacemaker: it senses only in the ventricle ; it paces the atrium & then the ventricle & is inhibited by intrinsic ventricular depolarization..
VDD----the pacemaker senses in both the atrium & ventricle & paces in the ventricle.

2.What is a fixed rate pacemaker? Give an example.
Known as asynchronous pacemakers. Electrical impulses are delivered at regular pre-set intervals, independent of the patient’s intrinsic heart rate. These pacemakers are good for pacing during bradycardia secondary to new onset third degree AV block. Ventricular tachycardia may result when competition with a patient’s intrinsic rate leads to a
pacing spike that occurs on a T wave.

3. What is a single chamber demand pacemaker?
Demand pacemakers are also known as noncompetitive pacemakers. They stimulate the heart “ On Demand “ only when spontaneous impulses do not occur during a preselected time interval. This type of pacemaker is inhibited by intrinsic R waves when the patient’s own heart rate is greater than the preset rate.

4. Why is it occasionally necessary to convert a demand pacemaker to an asynchronous pacemaker ? How is this accomplished?
A
demand pacemaker amy malfunction because of faulty circuitry, incorrect programming, or extrinsic radiofrequency interference. So it may be  useful to convert the pacemaker to asynchronous mode , so that the myocardium is depolarizes at regular interval & cardiac output is maintained.
Mode conversion may be achieved by reprogramming the pacemaker through an external remote control radio device or by bringing a specially designed magnet in close to the pacemaker. A pacemaker magnet should always be nearby when patients with pacemakers undergo surgical procedures.

5. What is the most common type of pacemaker?
VVI demand pacemaker is the most commonly placed pacemaker today.

6. What is an implantable cardioverter-defibrillator( ICD)?
An ICD continuously monitors the patient’s cardiac rhythm. ICDs are placed in patients prone to ventricular dysrhythmias & in whom medical management has failed. When Ventricular tachycardia or fibrillation is detected, this device will deliver countershocks in an attempt to convert the heart to its baseline rhythm.

Preoperative evaluation in the patient with a pacemaker.

7. What kind of diagnostic information & data from the history & exam are particularly relevant in these patients?
Medical problems including cardiovascular disease.
Cardiac medications.Original indications for placement of the pacemaker.
Whether the patient is experiencing a return of
pre-pacemaker symptoms.
Chest Radiograph ---verify the pacemaker lead continuity, look for signs of congestive heart failure.
Recent ECG---to check the pacemaker spikes.
A recent hematocrit to assess oxygen carrying capacity in patients with cardiac disease.
Serum K+ --to identify acute changes in extracellular K+ concerntration which may affect myocardial sensitivity to pacing.

8. What kind of data should be gathered regarding the pacemaker itself?
The type of pacemaker ( Letter code).
Date of placement.
If no pacemaker identity card , a chest X-ray will reveal the letter code ( which is radiopaque) and also the location of the pacemaker.

9. Do these patients require any type of special monitoring?
The presence of pacemaker is not an indication for invasive manitoring.

Intraoperative management of the patient with a pacemaker
10. Is succinylcholine contraindicated for general anesthetics in patient with pacemaker ?
Fasciculations after the depolaring muscle relaxants may be perceived
by the pacemaker sensor as an intrinsic cardiac impulse. Depending on the type of pacemaker, it may be inhibited from firing an impulse resulting in deleterious reductions in heart rate & cardiac output, even cardiac standstill. A “ defasciculating “ dose of a non depolarizing muscle relaxant should be given 5-10 minutes before succinylcholine is administered. Additionally the pacemaker may be reprogrammed to asynchronous ( VOO ) mode, so that it stimulates the ventricle regardless of intrinsic cardiac activity.

11. How does electrocautery affect pacemaker function?
Electromagnetic interference ( EMI) from electrocautery is probably the most common cause of intraoperative pacemaker failure.
Because the EMI is interpreted as normal intrinsic cardiac activity. Electrocautery will not affect VOO pacemaker . So by applying an external magnet or by reprogramming the pacemaker to asynchronous mode , this problem can be overcomed.
But a magnet should not be used on a multiprogrammable pacemaker. This type of pacemaker can be used even with cautery.

12. What can be done to protect the pacemaker from the untoward effects of EMI ?



Use bipolar cautery
Electrocautery energy level should be kept as low as possible.

Short bursts are safer than continuous activation.
Current dispersal unit or pad should be placed remote from the pacemaker.

13. Your patient with a pacemaker is found pulseless; ECG demonstrates ventricular tachycardia. The defibrillator is charged & ready to go . Do you proceed with external defibrillation?
Yes. Most pacemaker are constructed with protective circuit designed to withstand external defibrillation. The paddles, however , should not be placed directly over the pacemaker.

心脏起搏器及麻醉类型的心脏起搏器
1.什么是 5 –letter 编码系统，用来描述心脏起搏器？
大多数心脏起搏器引用的代码的第 3 封信。第一封信指示起搏电极的位置。第二个字母标志着心脏起搏器的传感器的位置。第三个字母是活动的指示性模式。第四个字母描述可编程性。第五封信描述埋藏式心律转复除-去纤颤器 (ICD)编码系统的心脏起搏器 （第 3 封信 — — 第一，二，三，)我分庭踱来踱去 O = 无 ；A = 中庭，V = 心室 ； D = 双 (A + V)二分庭遥感 O = 无 ；A = 中庭，V = 心室，D = 双 (A + V)三、 模式的活动 O = 无 T = 触发器，我 = 抑制，D = 双 (T＆I）类型的心脏起搏器青生---心房固定的 rate(Asynchronous) 起搏器： 它步伐无论内在心脏活动中庭。手邬---心室固定的利率起搏器： 它步伐，无论内在心脏活动的心室。非洲工业化联盟--心房按需起搏器： 它感觉 & 步伐只在中庭 ；它 si 抑制起搏的内在 P 波。VVI---需求心室起搏器： 它感觉 & 步伐只在心室 ；内在 R 波抑制它从起搏。学能测验 — — 心房触发起搏器： 它感觉 & 步伐中庭 ；它会触发将由遥感内在 (Nonconducted) P 波的步伐。VVT---脑室触发起搏器： 它感觉 & 步伐在心室 ；它会触发将由遥感内在 （Nonconducted） R 波的步伐。DVI---顺序起搏器： 仅在心室 ； 感知它步伐中庭 & 然后心室 & 固有的心室去极化，故...VDD---在心房及心室起搏器感官及脑室的步伐。
2.什么是固定的利率起搏器？举一个例子。
称为异步心脏起搏器。电脉冲传递预设定期、 独立的病人的固有心率。这些心脏起搏器的过程中学到新发病三度 AV 块心动过缓起搏擅长。室性心动过速可能会导致在病人的内在增长率与竞争而导致发生在 T 波的起搏穗。
3.什么是单室需起搏器？
心脏起搏器的需求被称为非竞争心脏起搏器。他们刺激心脏"需"仅当自发的冲动不会发生在预选选定的时间间隔。当病人的心率大于预设率内在 R 波被抑制这种类型的心脏起搏器。
4.为什么是偶尔有必要将需起搏器转换为异步起搏器？这是如何完成的？
A艾米故障故障电路、 不正确编程或外在射频干扰而需起搏器。因此可能有用将转换为异步模式下，心脏起搏器，以使心肌 depolarizes 定期时间间隔及保持心输出量。由通过外部远程控制无线电设备编程起搏器或带来一个特别设计的磁铁靠近起搏器可能实现模式转换。心脏起搏器磁铁始终应附近时心脏起搏器患者接受外科手术。
5.什么是心脏起搏器的最常见类型？
心室起搏的需求是今天最通常放置起搏器。
6.什么是埋藏式心律转复除颤 (ICD)？
ICD 持续监视患者的心律。内陆集装箱站都放在病人易发生心室心律失常及医疗管理失败的人。当检测到心室性心动过速或颤动时，此设备将 countershocks 试图转换为其基线节奏的心。心脏起搏器患者的术前评估。
7.特别是有关在这些患者中何种诊断信息和数据从历史与考试？
包括心血管疾病的医疗问题。心脏药物。起搏器安置的最初迹象。病人是否正在经历的回报率pre-pacemaker 的症状。胸部 x 光照片---验证起搏器铅连续性、 寻找充血性心衰的迹象。最近心电图---以检查心脏起搏器的峰值。评估与心脏疾病患者的携氧能力最近红细胞压积。血清 K + 查明急性细胞外 K + concerntration 可能影响心肌敏感性对节奏的变化。
8.什么样的数据应收集到有关心脏起搏器本身？心脏起搏器 （字母代码） 的类型。安置的日期。如果没有心脏起搏器的身分证，胸部 x 光透视将揭示信代码 （这是不透 x 线），同时还起搏器的位置。
9.这些病人需要任何类型的特别监测吗？
心脏起搏器的存在不是创监测指征。心脏起搏器患者的术中管理
10.是琥珀胆碱禁忌症起搏器患者全身麻醉药吗？
Fasciculations 后可能被认为 depolaring 肌松药作为一种内在的心脏冲动的起搏器传感器。根据心脏起搏器的类型，它可抑制从射击造成有害心率及心输出量，减少冲动甚至心脏停搏。非临界的肌肉松弛剂"defasciculating"剂量应给予 5-10 分钟前琥珀胆碱的方式管理。此外起搏器可能重新为异步 （手邬） 模式，以便它刺激，无论内在心脏活动的心室。
11.电灼如何影响起搏器功能？
电磁干扰 (EMI) 从电刀可能是心脏起搏器术中失败的最常见原因。因为 EMI 被解释为正常的固有心脏活动。电灼不会影响手邬起搏器。所以通过应用外部磁铁或重新设置为异步模式起搏器，这个问题可以克服。但不是应在 multiprogrammable 的起搏器使用磁铁。这种类型的心脏起搏器甚至用烧灼。
12.什么可以做，保护心脏起搏器从 EMI 的不良反应？
使用双极性烧灼电灼能量水平应保持尽可能低的水平。短时间都比连续激活更安全。当前分散单位或垫应放远程从心脏起搏器。
13.你的心脏起搏器的病人发现无脉 ；心电图显示心室性心动过速。除颤仪是带电 & 准备去。与外部除颤进行吗？是。大多数起搏器都构造保护电路设计能够承受外部除颤。但是，不应直接通过起搏器放桨。