shock

) شوک)

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نام و نام خانوادگی :مرجان میرقائد

موضوع:

shock) شوک)

پست سازمانی:سوپر وایزر بالینی

بهمن22بیمارستان 1391بهمن

شماره.........................................................عنوان4........................................................................................................................................مقدمه

شوک های 4..........................................................................................................................علت

شوک 4.................................................................................................................................انواع

: عفونی 4.............................................................................................................................شوک

قلبی 4.................................................................................................................................شوک

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آنافالکتیک 4..........................................................................................................................شوک

زا عصب 4............................................................................................................................شوک

هیپوولمیک 4.........................................................................................................................شوک

: هیپوولمیک 4........................................................................................................................شوک

رویشی خون 4......................................................................................................................شوک

گردشی 4.............................................................................................................................شوک

: ها نشانه و 4.........................................................................................................................عالئم

: قلبی شوک 4.......................................................................................................................عالئم

4....................................................................................................................................تشخیص:

مقدمه

واژه ی شوک متفاوتا با محیط پزشکی و عمومی همگانی استفاده شده است. توارد ذهنی توسط عموم یک واکنش عاطفی شدید با

وضعیت پردغدغه یا اخبار بد است. تعریف پزشکی شوک بسیار

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متفاوت است. از نظر پزشکی، شوک به عنوان وضعیتی که بافت ها در بدن نمی توانند اکسیژن و مواد مغذی کافی را دریافت کنند تا

اینکه سلول ها را قادر به فعالیت سازند، تعریف شده است. این نهایتا به مرگ سلولی، پیشرفت ناتوانی ارگان و نهایتا در صورت عدم

درمان ناتوانی کل بدن و مرگ منجر می شود

در اصطالحات پزشکی، یک شوک وضعیتی است که در آن سلول های متنوع بدن اکسیژن کافی را دریافت نمی کنند هنگامی که عرضه

ی ناکافی خون به کل بخش های بدن وجود دارد.

شوک یک وضعیت شدیدا خطرناک و تهدید برانگیز زندگی است، هنگامی که عدم اکسیژن در بافت های ارگان های متفاوت بدن می تواند سبب فلج و عملکرد بد سلول های مغز و در اکثر موارد ایست قلبی شود. یک درمان فوری بنابراین بایستی با بیمار صورت گیرد به محض اینکه بدنش دستخوش یک شوک می شود. یک شوک رخ می

دهد هنگامیکه بدن دستخوش یک رویداد غیرمنتظره می شود، که می تواند هرگونه جراحت فیزیکی، بیماری شدید یا یک ضربه ی عاطفی

باشد.

علت های شوک

دالیل بسیاری از شوک پزشکی وجود دارد. چیزی که اتفاق می افتد این است که گیرنده هایمان یک سیگنال غیرمعمولی دریافت می کند و دستخوش یک شوک می شود. آن معموال زمانی اتفاق می افتد

که بدن یک بیماری غیرمعمول، یک آسیب خارجی یا داخلی یا یک4

واقعه ی غم انگیز برای ارائه ی سیگنال برای جریان خون متحمل می شود و ارگان های بدن یک عرضه ی ناکافی از اکسیژن به دست می

آورند.

شوک موجب شده توسط یک آسیب یا یک بیماری بسیار خطرناک تر است و یک کمی متفاوت از شوک موجب شده با یک رخداد غم انگیز

یا یک رخداد وحشت انگیز است، از آنجایی که در مورد دومی بدن می تواند به آسانی در اکثر موارد بهبود یابد و تأثیر به مدت طوالنی طول

نمی کشد.

انواع شوک

شوک های عاطفی و روانی به سادگی سبب یک رویداد غیرمنتظره می شود که به جریان غیر صحیح خون منجر می شود که در عوض

سبب رساندن ناکافی اکسیژن می شود که به فلج موقتی یا طوالنی حواس منجر می شود. از سوی دیگر، شوک های موجب شده توسط

یک آسیب یا یک بیماری شدید بسیار پیچیده تر هستند و متفاوت ازهمدیگر هستند. آنها به پنج نوع مهم زیر دسته بندی شده اند:

شوک عفونی:

شوک عفونی یک نوع متعارف و معمول از شوک است که با بیماری های شدید مانند ذات الریه، مننژیت یا چند عفونت درون

شکمی همراه می شود. اساسا این شوک بعد از یک عفونت باکتریایی موجب شده است. اگر بیماری تشخیص داده شود و درمان آنتی

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بیوتیک به بیمار داده شود، سلول های باکتریایی درون مانع ازرشدشان می شود و بدن از شوک رنج نمی برد.

اما اگر بیماری طوالنی شود، سلول های باکتریایی درون بدن تکثیر می شوند. تکثیر سریع سلول های باکتریایی سموم خاصی را در بدن

آزاد می کند. این سموم با خون ترکیب می شوند. و کل شبکه ی گردش خون را منهدم می کند. آنها اکسیژن را مصرف می کنند و بدن دستخوش یک شوک شدید می شود که به فلج دائمی مغز منتهی می

شود.

شوک عفونی یک نوع خیلی خطرناک از شوک موجب شده توسط عفونت های باکتریایی است که کامال متعارف و معمول هستند.

شخص باید یک درمان صحیح برای چنان بیماری هایی داشته باشد همچنانکه سلول های باکتریایی در بدن سالم باقی می مانند که آنها به

حالت شوک منجر می شوند.

شوک قلبی

شوک قلبی نوع دیگری از شوک است که مستقیما با نارسایی قلببرای تولید مقدار ناکافی خون برای بدن موجب شده است.

هنگامیکه دریچه های قلب مسدود گرفته می شوند، آنها شروع به تولید مقدار کمی از خون از حد موردنیاز می کنند که به کمبود شدید

اکسیژن در بدن منتهی می شود.

زمانیکه قلب کامال در تولید خون ناکام می ماند، این به یک شوک شدید به دنبال یک حمله ی قلبی منتهی می شود. در اکثر موارد

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ممکن است به نارسایی قلبی انسدادی منجر می شود. بنابراین شوک قلبی همچنین می تواند به عنوان یک شوک با پیش حمله ی قلبی

نامیده شود.

شوک آنافالکتیک

شوک آنافالکتیک با یک واکنش آلرژیک شدید در بدن موجب شده است. آن می تواند هر نوع از واکنش آلرژیک باشد. اکثرا این شوک با

یک واکنش آلرژیک در بدن همراه می شود که با نیش حشرات،داروها یا هر نوع غذا موجب می شود.

علت آلرژی ممکن است در افراد مختلف، متفاوت باشد از آنجایی که آن منحصرا به حساسیت بدن فرد در جهت یک عامل بستگی دارد. در هر صورت، آلرژی که سبب عامل در آزادسازی سموم در بدنمان

می شود، اگر کنترل نشود، این سموم یک بخش از گردن بدنمان می شود و سبب یک صدمه ی شدید می شود که به یک شوک منتهی می

شود.

شوک عصب زا

شوک عصب زا احتماال خطرناک ترین نوع شوک است که به یکفلج آنی منتهی می شود که برای همیشه طول می کشد.

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این شوک با صدمه ی شدید نخاع موجب شده است. از آنجایی که نخاع، رأس بسیاری از فعالیت ها در بدنمان است، هرگونه صدمه با

نخاع می تواند سبب یک آسیب دائمی شود.

شوک هیپوولمیک

شوک هیپوولمیک نوع متعارف دیگری از شوک است که با هرگونه صدمه ی خارجی یا داخلی همراه می شود. اساسا این شوک به علت

کاهش شدید خون موجب شده توسط جراحت موجب شده است.

شوک)انواع خاص(:

شوک هیپوولمیک و شوک خون روشی:

شوک هیپوولمیک:

نیاز به آب گلبول های قرمزخون کافی در خون وجود دارد برای اینکه قلب سیاالت را درون مجرای خون حرکت دهد. هنگامیکه بدن

آب از دست می دهد، ممکن است گلبول های قرمز خون کافی وجود داشته باشد، اما حجم کامل سیال کاهش یافته است و فشار درون

سیستم کاهش می یابد. فرآورده ی قلبی، مقدار خونی است که قلب می تواند در یک دقیقه پمپاژ کند. آن به عنوان حجم حرکت در نظر

گرفته شده است)چه مقدار خون در هر تپش و زنش قلب می تواند پمپاژ شود( که با سرعت قلب تکثیر می شود)در هر دقیقه قلب چقدر

سریع می تپد(. اگر خون کمی در سیستم برای پمپاژ وجود داشته باشد، قلب سریع کار می کند برای اینکه تالش کند تا فرآوری ثابتش

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درصد از خون را تشکیل می دهد. اگر بدن90را حفظ کند. آب خشک شود به خاطر این است که آب از دست رفته است یا جذب

سیال)مایع( ناکافی است، بدن تالش می کند تا فرآورده ی قلبی را با ایجاد زنش سریعتر قلب حفظ کند. اما هنگامی که مقدار سیال

کاهش می یابد، مکانیزم های همبستگی بدن مختل می شوند و ممکناست شوک روی دهد.

شوک هیپو ولمیک مربوط به اتالف آب می تواند نقطه ی پایان بسیاری از بیماری ها باشد، اما عنصر معمول، عدم سیال درون بدن

است.

نهایتا در شوک هیپو ولمیک، بیمار نمی تواند مقدار سیالی که با نوشیدن آب کافی از دست رفته است را جایگزین کند، و بدن نمی

تواند فشار خون و فرآورده ی قلبی را حفظ کند. در تمام حالت های شوک، هنگامیکه سلول ها شروع به بد عمل کردن می کنند محصوالت

زائد تشکیل می شوند و مرگ مارپیچ پایین سلول شروع می شود، افزایش اسیدوز رخ می دهد و وخیم تر شدن محیط بدن به مرگ

بیشتر سلول- و نهایتا ناتوانی ارگان منجر می شود.

شوک خون رویشی

یک زیر مجموعه از شوک خون روشی اتفاق می افتد زمانیکه خون ریزی مهم وجود دارد که نسبتا سریع اتفاق می افتد. زخم معمول

ترین و شایع ترین نمونه ی خونریزی یا خون روشی است، اماخونریزی می تواند از شرایط پزشکی مانند زیر رخ دهد:

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خون ریزی از دستگاه معدی و روده ای معمول است؛ مثال ها شامل زخم معده یا زخم اثنی عشری، سرطان های روده ی

بزرگ یا دیورتیکول ها باشند.در زنان، خونریزی مفرط و بیش از اندازه می تواند از رحم

اتفاق بیافتد.افراد مبتال به سرطان یا سرطان خون برای خونریزی خود به

خود از منابع متنوع بالقوه هستند در صورتیکه مغز استخوانشانعوامل لخته شدگی کافی تولید نمی کند.

)بیمارانی که از رقیق کننده های خون)داروهای ضد انعقاد خون استفاده می کنند، همچنین می توانند شدیدا خونریزی کنند. کاهش خون دو تأثیر بر روی بدن دارد. اوال، کاهش حجم درون

مجراهای خون برای پمپاژ وجود دارد)شوک هیپو ولمیک را ببینید( و دوما کاهش اکسیژن به خاطر صدمه ی گلبول های قرمز خون رخ می

درصد از حجم10دهد. در غیر این صورت افراد سالم می توانند تا خونشان را بدون داشتن نشانه های بیماری با ضعف، گیجی یا کوتاهی

تنفس از دست دهند.

درمان شوک خون روشی به علت آن بستگی دارد. یافتن و کنترل منبع خونریزی حائز اهمیت واالیی است. مایعات داخل وریدی برای کمک در بهوش آوری استفاده شده اند برای اینکه حجم مایع درون

فضای مجرای خون افزایش یابد، اما تزریق خون همیشه الزامی نیست. اگر خونریزی کنترل شود و بیمار استوارتر شود، مغز

استخوان ممکن است اجازه دهد که گلبول های قرمزخون که ازدست رفته اند مجددا تکمیل شوند.

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شوک گردشی

شوک گردشی معموال به عنوان یک شوک شناخته شده است، که یک وضعیت پزشکی تهدید برانگیز زندگی است که به علت زیر الیه ی ناکافی برای تنفس سلولی هوازی رخ می دهد. در مراحل اولیه، این

معموال یک سطح بافت ناکافی از اکسیژن است.

عالئم معمولی شوک، فشار خون پایین، ضربان قلب سریع و عالوم تزریق وریدی ضعیف ارگان یا حمله ی قلبی است. زمان هایی وجود

دارد که فشار خون یک شخص ممکن است ثابت باقی بماند، اما ممکن است هنوز در شوک گردشی باشد، بنابراین آن همیشه یک

عالمت نیست.

شوک گردشی نباید با حالت عاطفی شوک مغشوش شود، از آنجایی که این دو مرتبط نیستند، شوک گردشی یک امر فوق العاده و

غیر منتظره ی پزشکی تهدید برانگیز زندگی است و یکی از معمول ترین علت های مرگ برای افرادی که به طور وخیم بیمار هستند، می

باشد. شوک می تواند تنوعی از تأثیرات، همه با پیامدهای مشابه داشته باشد، اما همه به یک مسئله با سیستم گردش خون مرتبط

هستند، برای مثال، شوک ممکن است به کم اکسیژنی)عدم اکسیژندر خون شریانی( یا ایست قلبی قلبی منجر شود.

یکی از خطرات اساسی شوک این است که آن توسط یک مکانیزم انعکاسی مثبت پیش می رود. زمانیکه شوک شروع می شود، تمایل

دارد که خودش را بدتر سازد. این است که دلیل اینکه چرا درمانفوری شوک مهم است.

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عالئم و نشانه ها:

شوک هیپوولمیک درمان واکنش کاهش خون

رده

<15(% 75/0کمیته ای حداقل، زنش سریع قلب، فشار خون طبیعی )I

( %75/0- 5/1مایعات داخل وریدی زنش سریع قلب، حداقل، فشار خون پایین )30-15 II

30-40( % 5/1-2 های بسته ای زنش خیلی سریع قلب، فشار خون پایین، گیجی )RBCمایعات و III

>40 >( % 2مداخالت فعاالنه فشار خون و زنش قلب وخیم )IV

بر روی عالئم1-4شدت شوک خون روشی می تواند در یک مقیاس فیزیکی درجه بندی شود. این به کاهش موثر حجم خون نزدیک است.

عالئم شوک قلبی:

سیاهرگ متورم زیر گلوئی به علت افزایش فشار سیاهرگی زیر گلوئی

تپش ضعیف یا غیرموجودبی نظمی در ضربان قلب، اغلب ضربان شدید قلب

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تپش های متناقض در موردtamponade

تشخیص:

اولین تغییرات دیده شده در شوک افزایش برون داد قلبی به دنبال (است، همانگونه کهSmvo2کاهش در ترکیب اشباع اکسیژن سیاهرگی)

در شریان ریوی از طریق یک کاتتر)سوند( شریان ریوی اندازه گیری ( همانگونه که از طریقScvo2شد. اشباع اکسیژن سیاهرگی مرکزی)

مرتبط می باشد وSmvo2یک خط مرکزی اندازه گیری شد به خوبی با برای به دست آوردن آسانتر است. اگر شوک متابولیسم غیرهوازی را

به پیش ببرد، شروع خواهد کرد که با افزایش اسید الکتیک خون به عنوان یک پیامد رخ دهد. در حالیکه بسیاری از تست های آزمایشگاهی

معموال انجام گرفته شده است و هیچ تستی وجود ندارد که مستنثی سینه یا اولتراسوند درپارتمان اورژانسXاز تشخیص باشد. اشعه ی

ممکن است برای تعیین حجم حالت مفید باشد.

Pade..................................................................................................numberTypes Of Shock......................................................................................................................................4

Causes Of Shock....................................................................................................................................4

Types Of Shocks.....................................................................................................................................4

Septic Shock...........................................................................................................................................4

Cardiogenic Shock.................................................................................................................................4

Anaphylactic Shock................................................................................................................................4

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Neurogenic Shock..................................................................................................................................4

Hypovolemic Shock...............................................................................................................................4

Shock - Specific Types............................................................................................................................4

Hemorrhagic Shock................................................................................................................................4

Shock (circulatory).................................................................................................................................4

Signs and symptoms..............................................................................................................................4

Hypovolemic..........................................................................................................................................4

Cardiogenic............................................................................................................................................4

Distributive............................................................................................................................................4

Pathophysiology....................................................................................................................................4

Initial......................................................................................................................................................4

Compensatory.......................................................................................................................................4

Progressive............................................................................................................................................4

Refractory..............................................................................................................................................4

Septic shock...........................................................................................................................................4

Diagnosis...............................................................................................................................................4

Differential diagnosis.............................................................................................................................4

Hypovolemic..........................................................................................................................................4

Distributive............................................................................................................................................4

Endocrine..............................................................................................................................................4

Management.........................................................................................................................................4

Fluids.....................................................................................................................................................4

Medications...........................................................................................................................................4

Treatment goals....................................................................................................................................4

Epidemiology.........................................................................................................................................4

History...................................................................................................................................................4

References.............................................................................................................................................4

introduction

The word shock is used differently by the medical community and the general public. The connotation by the public is an intense emotional reaction to a stressful situation or bad news. The medical definition of shock is much different.

Medically, shock is defined as a condition where the tissues in the body don't receive enough oxygen and nutrients to allow the cells to function.

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This ultimately leads to cellular death, progressing to organ failure, and finally, if untreated, whole body failure and death.

Types Of Shock

In medical terms a shock is a condition in which various cells of the body fail to receive enough oxygen as there is an insufficient supply of blood to the entire body parts.

Shock is an extremely dangerous and a life threatening situation as the lack of oxygen in the tissues of various organs of the body can cause a paralysis and malfunctioning of brain cells and in most cases a cardiac arrest.

An immediate treatment must be, therefore, given to the patient as soon as his body undergoes a shock. A shock occurs when a body undergoes an unexpected event. It can be any physical injury, severe illness or an emotional blow.

Causes Of Shock

There are many causes of a medical shock. What happens is that when our receptors receive an unusual signal and it undergoes goes a shock. It happens usually when the body goes through an unusual illness, an external or an internal injury or a tragic event our brain cells seize to give the signals for the blood to flow and the body organs get an insufficient supply of oxygen.

The shock caused by an injury or an illness is far more dangerous and a bit different from the shock caused by a tragic or a frightening event as in the latter case the body can easily recover on its own in most cases and the effect is not long lasting.

Types Of Shocks

Emotional and psychological shocks are simply caused by an unexpected event which leads to an improper flow of blood which in return causes an insufficient supply of oxygen which leads to either a temporary or a prolonged paralysis of senses.

On the other hand the shocks caused by an injury or severe illnesses are far more complex and are different from each other.

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They are classified into following five major types:

Septic Shock

Septic shock is a common type of shock which accompanies severe diseases such as pneumonia, meningitis or some intra abdominal infections. Basically this shock is caused after a bacterial infection. If the disease is diagnosed and the antibiotic treatment is given to the patient the bacterial cells inside inhibit their growth and the body does not suffer from the shock.

But if the disease is prolonged the bacterial cells inside the body keep on multiplying. The rapidly multiplying bacterial cells release certain toxins in the body. These toxins mix with the blood and damage the entire network of blood circulation. They take up the oxygen and the body undergoes a severe shock which results in the permanent paralysis of the brain.

Septic shock is a very dangerous kind of shock caused by bacterial infections that are quite common. One must have a proper treatment for such diseases as if the bacterial cells remain intact in the body they lead to a shocked state.

Cardiogenic Shock

Cardiogenic shock is another kind of shock which is directly caused by the failure of heart to produce sufficient amount of blood for the body.

When the valves of heart get clogged up and congested they start producing less amount of blood than required which results in a severe shortage of oxygen in the body.

There comes a time when the heart completely fails to produce blood this results in a severe shock followed by a heart attack. In most cases it may result in congestive heart failure. Hence cardiogenic shock can also be called as a pre heart attack shock.

Anaphylactic Shock

Anaphylactic shock is caused by a severe allergic reaction in the body. It can be any kind of allergic reaction. Mostly this shock accompanies an allergic reaction in the body caused insect bites, medicines or any food.

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The cause of allergy may vary in different people as it solely depends on the sensitivity of one’s body towards an agent.  Any way the allergy causing agent in the releases toxins in our, if not controlled early these toxins become a part of our circulation and cause a severe damage which results in a shock.

Neurogenic Shock

Neurogenic shock is probably the most dangerous kind of shock as it results in an instant paralysis which lasts forever.

This shock is caused by a severe injury of the spinal cord. Since spinal cord is the head of many activities in our body, any damage to the spinal cord can cause a permanent damage.

Hypovolemic Shock

Hypovolemic shock is another common type of shock which accompanies any internal or external injury. Basically this shock is caused due to severe loss of blood caused by the injury.

Shock - Specific Types

Hypovolemic and Hemorrhagic Shock

Hypovolemic Shock

There needs to be enough red blood cells and water in the blood for the heart to push the fluids around within the blood vessels. When the body becomes dehydrated, there may be enough red blood cells, but the total volume of fluid is decreased, and pressure within the system decreases. Cardiac output is the amount of blood that the heart can pump out in one minute. It is calculated as the stroke volume (how much blood each heart beat can push out) multiplied by the heart rate (how fast the heart beats each minute). If there is less blood in the system to be pumped, the heart speeds up to try to keep its output steady.

Water makes up 90% of blood. If the body becomes dehydrated because water is lost or fluid intake is inadequate, the body tries to maintain

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cardiac output by making the heart beat faster. But as the fluid losses mount, the body's compensation mechanisms fail, and shock may ensue.

Hypovolemic (hypo=low + volemic=volume) shock due to water loss can be the endpoint of many illnesses, but the common element is the lack of fluid within the body.

Gastroenteritis can cause significant water loss from vomiting and diarrhea, and is a common cause of death in third world countries. Heat exhaustion and heat stroke is caused by excessive water loss through sweating as the body tries to cool itself. Patients with infections can lose significant amounts of water from sweating. People with diabetes who have diabetic ketoacidosis lose significant water because of because of elevated blood sugar that cause excess water to be excreted in the urine.

Ultimately in hypovolemic shock, the patient cannot replace the amount of fluid that was lost by drinking enough water, and the body is unable to maintain blood pressure and cardiac output. In all shock states, when cells start to malfunction waste products build up, a downward spiral of cell death begins, increased acidosis occurs, and a worsening body environment leads to further cell death - and ultimately organ failure.

Hemorrhagic Shock

A subset of hypovolemic shock occurs when there is significant bleeding that occurs relatively quickly. Trauma is the most common example of bleeding or hemorrhage, but bleeding can occur from medical conditions such as:

•Bleeding from the gastrointestinal tract is common; examples include stomach or duodenal ulcers, colon cancers or diverticulitis.

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•In women, excessive bleeding can occur from the uterus.

•People with cancers or leukemia have the potential to bleed spontaneously from a variety of sources if their bone marrow does not make enough clotting factors.

•Patients who are taking blood thinners (anticoagulant medications) can bleed excessively as well.

Blood loss has two effects on the body. First, there is a loss of volume within blood vessels to be pumped (see hypovolemic shock) and second, a reduced oxygen carrying capacity occurs because of the loss of red blood cells. Otherwise healthy people can lose up to 10% of their blood volume (about the amount that a person donates at a blood drive) without becoming symptomatic with weakness, lightheadedness, or shortness of breath.

The treatment of hemorrhagic shock depends on the cause. Finding and controlling the source of bleeding is of paramount importance. Intravenous fluids are used to help with resuscitation to increase the fluid volume within the blood vessel space, but blood transfusion is not always mandatory. If the bleeding is controlled and the patient becomes more stable, the bone marrow may be allowed to replenish the red blood cells that were lost.

If the red blood cell count in the blood decreases gradually over time, either because of bleeding or the inability of the body to make enough new red cells, the body can adjust to the lower levels to maintain adequate cell perfusion, but the individual's exercise tolerance may decrease. This means that they may do well in normal daily activities but find that routine exercise or household activities bring on weakness or shortness of breath. The treatment depends on the underlying diagnosis, since it isn't a total fluid problem as in hypovolemic shock

Shock (circulatory)

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"Acute shock" redirects here. For the psychological condition, see Acute stress reaction.

Circulatory shock, commonly known simply as shock, is a life-threatening medical condition that occurs due to inadequate substrate for aerobic cellular respiration. In the early stages this is generally an inadequate tissue level of oxygen.

The typical signs of shock are low blood pressure, a rapid heartbeat and signs of poor end-organ perfusion or "decompensation/peripheral shut down" (such as low urine output, confusion or loss of consciousness). There are times that a person's blood pressure may remain stable, but may still be in circulatory shock, so it is not always a sign.

Circulatory shock should not be confused with the emotional state of shock, as the two are not related. Circulatory shock is a life-threatening medical emergency and one of the most common causes of death for critically ill people. Shock can have a variety of effects, all with similar outcomes, but all relate to a problem with the body's circulatory system. For example, shock may lead to hypoxemia (a lack of oxygen in arterial blood) or cardiac arrest.

One of the key dangers of shock is that it progresses by a positive feedback mechanism. Once shock begins, it tends to make itself worse. This is why immediate treatment of shock is critical.[3]

 

Signs and symptoms

The presentation of shock is variable with some people having only minimal symptoms such as confusion and weakness. While the general signs for all types of shock are low blood pressure, decreased urine output, and confusion these may not always be present. While a fast heart rate is common, those on β-blockers, those who are athletic and in 30% of cases those with shock due to intra abdominal bleeding may have a normal or slow heart rate. Specific subtypes of shock may have additional symptoms.

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Hypovolemic

Hemorrhage classes

Class Blood loss Response Treatment

I <15 %(0.75 l)min. fast heart rate, normal blood pressure

minimal

II15-30 %(0.75-1.5 l)

fast heart rate, min. low blood pressure

intravenous fluids

III 30-40 %(1.5-2 l)very fast heart rate, low blood pressure, confusion

fluids and packed RBCs

IV >40 %(>2 l)critical blood pressure and heart rate

aggressive interventions

Direct loss of effective circulating blood volume leading to:

A rapid, weak, thready pulse due to decreased blood flow combined with tachycardia

Cool, clammy skin due to vasoconstriction and stimulation of vasoconstriction

Rapid and shallow breathing due to sympathetic nervous system stimulation and acidosis

Hypothermia due to decreased perfusion and evaporation of sweat Thirst and dry mouth, due to fluid depletion and Cold and mottled skin (Livedo reticularis), especially extremities,

due to insufficient perfusion of the skin

The severity of hemorrhagic shock can be graded on a 1-4 scale on the physical signs. This approximates to the effective loss of blood volume.

Cardiogenic

Distended jugular veins due to increased jugular venous pressure Weak or absent pulse Arrhythmia, often tachycardic Pulsus paradoxus in case of tamponade

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Distributive

Systemic inflammatory response syndrome[7]

Finding Value

Temperature <36 °C (96.8 °F) or >38 °C (100.4 °F)

Heart rate >90/min

Respiratory rate

>20/min or PaCO2<32 mmHg (4.3 kPa)

WBC<4x109/L (<4000/mm³), >12x109/L (>12,000/mm³), or 10% bands

Distributive shock includes infectious, anaphylactic, and neurogenic causes. The SIRS features typically occur in early septic shock.

Anaphylaxis

Hives may present on the skin Localised edema, especially around the face Weak and rapid pulse Breathlessness and cough due to narrowing of airways and swelling

of the throat

Pathophysiology

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Effects of inadequate perfusion on cell function.

There are four stages of shock. As it is a complex and continuous condition there is no sudden transition from one stage to the next. At a cellular level shock is oxygen demand greater than oxygen supply.

Initial

During this stage, the state of hypoperfusion causes hypoxia. Due to the lack of oxygen, the cells perform lactic acid fermentation. Since oxygen, the terminal electron acceptor in the electron transport chain is not abundant, this slows down entry of pyruvate into the Krebs cycle, resulting in its accumulation. Accumulating pyruvate is converted to lactate by lactate dehydrogenase and hence lactate accumulates (causing lactic acidosis).

Compensatory

This stage is characterised by the body employing physiological mechanisms, including neural, hormonal and bio-chemical mechanisms in an attempt to reverse the condition. As a result of the acidosis, the person will begin to hyperventilate in order to rid the body of carbon dioxide (CO2). CO2 indirectly acts to acidify the blood and by removing it the body is attempting to raise the pH of the blood. The baroreceptors in the arteries

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detect the resulting hypotension, and cause the release of epinephrine and norepinephrine. Norepinephrine causes predominately vasoconstriction with a mild increase in heart rate, whereas epinephrine predominately causes an increase in heart rate with a small effect on the vascular tone; the combined effect results in an increase in blood pressure. Renin-angiotensin axis is activated and arginine vasopressin (Anti-diuretic hormone; ADH) is released to conserve fluid via the kidneys. These hormones cause the vasoconstriction of the kidneys, gastrointestinal tract, and other organs to divert blood to the heart, lungs and brain. The lack of blood to the renal system causes the characteristic low urine production. However the effects of the Renin-angiotensin axis take time and are of little importance to the immediate homeostatic mediation of shock.

Progressive

Should the cause of the crisis not be successfully treated, the shock will proceed to the progressive stage and the compensatory mechanisms begin to fail. Due to the decreased perfusion of the cells, sodium ions build up within while potassium ions leak out. As anaerobic metabolism continues, increasing the body's metabolic acidosis, the arteriolar smooth muscle and precapillary sphincters relax such that blood remains in the capillaries.[9]

Due to this, the hydrostatic pressure will increase and, combined with histamine release, this will lead to leakage of fluid and protein into the surrounding tissues. As this fluid is lost, the blood concentration and viscosity increase, causing sludging of the micro-circulation. The prolonged vasoconstriction will also cause the vital organs to be compromised due to reduced perfusion. If the bowel becomes sufficiently ischemic, bacteria may enter the blood stream, resulting in the increased complication of endotoxic shock.

Refractory

At this stage, the vital organs have failed and the shock can no longer be reversed. Brain damage and cell death are occurring, and death will occur imminently. One of the primary reasons that shock is irreversible at this point is that much cellular ATP has been degraded into adenosine in the absence of oxygen as an electron receptor in the mitochondrial matrix. Adenosine easily perfuses out of cellular membranes into extracellular fluid, furthering capillary vasodilation, and then is transformed into uric acid. Because cells can only produce adenosine at a rate of about 2% of the

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cell's total need per hour, even restoring oxygen is futile at this point because there is no adenosine to phosphorylate into ATP.

Septic shock

Systemic leukocyte adhesion to endothelial tissue Reduced contractility of the heart Activation of the coagulation pathways, resulting in disseminated

intravascular coagulation Increased levels of neutrophils

Main manifestations are produced due to massive release of histamine which causes intense vasodilatation

Diagnosis

The first changes seen in shock is an increased cardiac output followed by a decrease in mixed venous oxygen saturation (SmvO2) as measured in the pulmonary artery via a pulmonary artery catheter. Central venous oxygen saturation (ScvO2) as measured via a central line correlates well with SmvO2 and are easier to acquire. If shock progresses anaerobic metabolism will begin to occur with an increased blood lactic acid as the result. While many laboratory tests are typically performed there is no test that either makes or excludes the diagnosis. A chest X-ray or emergency department ultrasound may be useful to determine volume state.

Differential diagnosis

Shock is a common end point of many medical conditions. It has been divided into four main types based on the underlying cause: hypovolemic, distributive, cardiogenic and obstructive. A few additional classifications are occasionally used including: endocrinologic shock.

Hypovolemic

This is the most common type of shock and is caused by insufficient circulating volume.[2] Its primary cause is hemorrhage (internal and/or external), or loss of fluid from the circulation. Vomiting and diarrhea are the most common cause in children.[1] With other causes including burns, environmental exposure and excess urine loss due to diabetic ketoacidosis and diabetes insipidus.

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Cardiogenic

This type of shock is caused by the failure of the heart to pump effectively. This can be due to damage to the heart muscle, most often from a large myocardial infarction. Other causes of cardiogenic shock include dysrhythmias, cardiomyopathy/myocarditis, congestive heart failure (CHF), contusio cordis, or cardiac valve problems.

Obstructive

Obstructive shock is due to obstruction of blood flow outside of the heart. Several conditions can result in this form of shock.

Cardiac tamponade in which fluid in the pericardium prevents inflow of blood into the heart (venous return). Constrictive pericarditis, in which the pericardium shrinks and hardens, is similar in presentation.

Tension pneumothorax Through increased intrathoracic pressure, bloodflow to the heart is prevented (venous return).

Pulmonary embolism is the result of a thromboembolic incident in the blood vessels of the lungs and hinders the return of blood to the heart.

Aortic stenosis hinders circulation by obstructing the ventricular outflow tract

Distributive

Distributive shock is due to impaired utilization of oxygen and thus production of energy by the cell.[2] Examples of this form of shock are:

Septic shock is the most common cause of distributive shock. Caused by an overwhelming systemic infection resulting in vasodilation leading to hypotension. Septic shock can be caused by Gram negative bacteria such as (among others) Escherichia coli, Proteus species, Klebsiella pneumoniae which release an endotoxin which produces adverse biochemical, immunological and occasionally neurological effects which are harmful to the body, and other Gram-positive cocci, such as pneumococci and streptococci, and certain fungi as well as Gram-positive bacterial toxins. Septic shock also includes some elements of cardiogenic shock. In 1992, the ACCP/SCCM Consensus Conference Committee defined septic

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shock: ". . .sepsis-induced hypotension (systolic blood pressure <90 mm Hg or a reduction of 40 mm Hg from baseline) despite adequate fluid resuscitation along with the presence of perfusion abnormalities that may include, but are not limited to, lactic acidosis, oliguria, or an acute alteration in mental status. Patients who are receiving inotropic or vasopressor agents may have a normalized blood pressure at the time that perfusion abnormalities are identified."

Anaphylactic shock Caused by a severe anaphylactic reaction to an allergen, antigen, drug or foreign protein causing the release of histamine which causes widespread vasodilation, leading to hypotension and increased capillary permeability.

High spinal injuries may cause neurogenic shock. The classic symptoms include a slow heartrate due to loss of cardiac sympathetic tone and warm skin due to dilation of the peripheral blood vessels. (This term can be confused with spinal shock which is a recoverable loss of function of the spinal cord after injury and does not refer to the haemodynamic instability per se.)

Endocrine

Based on endocrine disturbances such as:

Hypothyroidism (Can be considered a form of Cardiogenic shock) in critically ill patients, reduces cardiac output and can lead to hypotension and respiratory insufficiency.

Thyrotoxicosis (Cardiogenic shock) o may induce a reversible cardiomyopathy.

Acute adrenal insufficiency (Distributive shock) is frequently the result of discontinuing corticosteroid treatment without tapering the dosage. However, surgery and intercurrent disease in patients on corticosteroid therapy without adjusting the dosage to accommodate for increased requirements may also result in this condition.

Relative adrenal insufficiency (Distributive shock) in critically ill patients where present hormone levels are insufficient to meet the higher demands

Management

The best evidence exists for the treatment of septic shock in adults and as the pathophysiology appears similar in children and other types of shock

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treatment this has been extrapolated to these areas. Management may include securing the airway via intubation to decrease the work of breathing, oxygen supplementation, intravenous fluids and a passive leg raise (not Trendelenburg position), and blood transfusions. It is important to keep the person warm as well as adequately manage pain and anxiety as these can increase oxygen consumption.

Fluids

Aggressive intravenous fluids are recommended in most types of shock (e.g. 1-2 liter normal saline bolus over 10 minutes or 20ml/kg in a child) which is usually instituted as the person is being further evaluated. Which intravenous fluid is superior, colloids or crystalloids, remains undetermined. Thus as crystalloids are less expensive they are recommended. If the person remains in shock after initial resuscitation packed red blood cells should be administered to keep the hemoglobin greater than 100 gms/l.

For those with hemorrhagic shock the current evidence supports limiting the use of fluids for penetrating thorax and abdominal injuries allowing mild hypotension to persist (known as permissive hypotension). Targets include a mean arterial pressure of 60 mmHg, a systolic blood pressure of 70-90 mmHg, or until their adequate mentation and peripheral pulses People can't go into shock by waking up too suddenly.

Medications

Vasopressors may be used if blood pressure does not improve with fluids. There is no evidence of superiority of one vasopressor over another. Vasopressors have not been found to improve outcomes when used for hemorrhagic shock from trauma but may be of use in neurogenic shock. Activated protein C (Xigris) while once aggressively promoted for the management of septic shock has been found to improve survival and is associated with a number of complications, thus recommended. The use of sodium bicarbonate is controversial as it has not been shown to improve outcomes. If used at all it should only be considered if the pH is less than 7.0.

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Treatment goals

The goal of treatment is to achieve a urine output of greater than 0.5 cc/kg/hr, a central venous pressure of 8-12 mmHg and a mean arterial pressure of 65-95 mmHg. In trauma the goal is to stop the bleeding which in many cases requires surgical interventions.

Epidemiology

Hemorrhagic shock occurs in about 1-2% of trauma cases.

Prognosis

The prognosis of shock depends on the underlying cause and the nature and extent of concurrent problems. Hypovolemic, anaphylactic and neurogenic shock are readily treatable and respond well to medical therapy. Septic shock however, is a grave condition with a mortality rate between 30% and 50%. The prognosis of cardiogenic shock is even worse.

History

In 1972 Hinshaw and Cox suggested the classification system for shock which is still used today.

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References

1. ^ a b c d e f g h i j Silverman, Adam (Oct 2005). "Shock: A Common Pathway For Life-Threatening Pediatric Illnesses And Injuries". Pediatric Emergency Medicine Practice 2 (10). http://www.ebmedicine.net/topics.php?paction=showTopic&topic_id=149.

2. ^ a b c d e f g h i j k l m n o p Tintinalli, Judith E. (2010). Emergency Medicine: A Comprehensive Study Guide (Emergency Medicine (Tintinalli)). New York: McGraw-Hill Companies. pp. 165–172. ISBN 0-07-148480-9.

3. ^ a b c d Guyton, Arthur; Hall, John (2006). "Chapter 24: Circulatory Shock and Physiology of Its Treatment". In Gruliow, Rebecca. Textbook of Medical Physiology (11th ed.). Philadelphia, Pennsylvania: Elsevier Inc.. pp. 278–288. ISBN 0-7216-0240-1.

4. ^ Marino, Paul L. (September 2006). The ICU Book. Lippincott Williams & Wilkins, Philadelphia & London. ISBN 0-7817-4802-X. http://www.lww.com/product/?978-0-7817-4802-5.

5. ^ a b Tintinalli, Judith E. (2010). Emergency Medicine: A Comprehensive Study Guide (Emergency Medicine (Tintinalli)). New York: McGraw-Hill Companies. pp. 174–175. ISBN 0-07-148480-9.

6. ^ Tintinalli, Judith E. (2010). Emergency Medicine: A Comprehensive Study Guide (Emergency Medicine (Tintinalli)). New York: McGraw-Hill Companies. ISBN 0-07-148480-9.

7. ^ "American College of Chest Physicians/Society of Critical Care Medicine Consensus Conference: definitions for sepsis and organ failure and guidelines for the use of innovative therapies in sepsis". Crit. Care Med. 20 (6): 864–74. 1992. doi:10.1097/00003246-199206000-00025. PMID 1597042. http://www.chestjournal.org/content/101/6/1644.full.pdf.

8. ^ Armstrong, D.J. (2004). Shock. In: Alexander, M.F., Fawcett, J.N., Runciman, P.J. Nursing Practice. Hospital and Home. The Adult.(2nd edition): Edinburgh: Churchill Livingstone.

9. ^ a b c d e f g Kumar, Vinay; Abbas, Abul K.; Fausto, Nelson; & Mitchell, Richard N. (2007). Robbins Basic Pathology (8th ed.). Saunders Elsevier. pp. 102-103 ISBN 978-1-4160-2973-1

10. ^ Tintinalli, Judith E. (2010). Emergency Medicine: A Comprehensive Study Guide (Emergency Medicine (Tintinalli)).

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New York: McGraw-Hill Companies. pp. 168. ISBN 0-07-148480-9.

11. ^ a b c Cocchi, MN; Kimlin, E, Walsh, M, Donnino, MW (2007 Aug). "Identification and resuscitation of the trauma patient in shock.". Emergency medicine clinics of North America 25 (3): 623–42, vii. doi:10.1016/j.emc.2007.06.001. PMID 17826209.

12. ^ American College of Surgeons (2008). Atls, Advanced Trauma Life Support Program for Doctors. Amer College of Surgeons. pp. 58. ISBN [[Special:BookSources/1-880696-31-6|1-880696-31-6]].

13. ^ Perel, P; Roberts, I (2007 Oct 17). "Colloids versus crystalloids for fluid resuscitation in critically ill patients.". Cochrane database of systematic reviews (Online) (4): CD000567. doi:10.1002/14651858.CD000567.pub3. PMID 17943746.

14. ^ Marx, J (2010). Rosen's emergency medicine: concepts and clinical practice 7th edition. Philadelphia, PA: Mosby/Elsevier. p. 2467. ISBN 978-0-323-05472-0.

15. ^ a b c d Cherkas, David (Nov 2011). "Traumatic Hemorrhagic Shock: Advances In Fluid Management". Emergency Medicine Practice 13 (11). http://www.ebmedicine.net/store.php?paction=showProduct&catid=8&pid=244.

16. ^ Havel, C; Arrich, J, Losert, H, Gamper, G, Müllner, M, Herkner, H (2011-05-11). "Vasopressors for hypotensive shock.". Cochrane database of systematic reviews (Online) 5: CD003709. doi:10.1002/14651858.CD003709.pub3. PMID 21563137.

17. ^ Diez, C; Varon, AJ (2009 Dec). "Airway management and initial resuscitation of the trauma patient.". Current opinion in critical care 15 (6): 542–7. doi:10.1097/MCC.0b013e328331a8a7. PMID 19713836.

www.wikipedia.com پدیا ویکی

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