Cardiopulmonary arrest is the sudden,unexpected cessation of respiration and functional circulation.(2)
It is frequently difficult to determine wether respiratory arrest precedes or follows circulatory arrest in any particular patients wether the initial event,however,is the cessation of circulation or respiration,tissue hypoxia occurs rapidly.(4)
Haldane remarked not only does the body machine breakdown,but the machinery is wrecked.(4)
In case circulatory arrest,the pupil dilate in 45 sec and respiratory stop within one minute due to medullry depression.(4)
In the adult the brain may be damaged within 4-6 minutes (2). If respiratory arrest occurs first the circulation continue for 5 minutes. A prompt decision to initiate effective resuscitative measure is required,since the greater the time lag between cardiac arrest and therapy,the lesser the likelihood that normal brain function will return. Hence the main objective of cardiopulmonary resuscitation is the effective delivery of oxygenated blood to the tissues.(4)
Failure to reinstitute artificially an adequate flow of oxygenated blood to the brain within 3 minutes of cardiac arrest dooms the patients to irreversible cerebral damage.(4)
DIAGNOSIS OF CARDIAC ARREST :
Absence of pulsation in mayor vessels such as a carotid or femoral or axillary artery or absence of the heart sound over the precordium.indicates loss of functional circulation.(4)
An ECG can easily detect asystole or ventricular fibrillation. Cardiac asystole there is absence of elctrical activity.The ECG tracings shows only a straight line.Ventricular fibrillation account for 75% of cardiac arrest ,especially after myocardial infarct. The ECG tracing shows wavy,irregular and chaotic activity.
Electro mechanical dissociation (EMG) or Pulseless electrical activity(PEA) regular electrical activity may be seen with a recognizable electro cardiographic complex but there is in adequate cardiac output,as evidence by absence of a palpable pulse,as in profound cardiovascular collapse where ECG appears normal in configuration but usually of low voltage.(2.4)
A systolic of about 50 mmHg is necessary for the pulse to be palpable.(4)
Agonal gasping respiration followed a respiratory apnoe is diagnosed by the chest movement or breath sounds.
Dilatated pupils that are unresponse to light are suggestive,but not necessary diagnostic of brain hypoxia.
Loss of conciousness and flaccidity,if the patient convulsies the brain not anoxic yet.(4)
The cessation of surgical bleeding and pallor of the skin.
CAUSATION OF CARDIAC ARREST :
Sudden failure of cardiac action or output may be due to asystole or ventricular fibrillation.
Aetiological factors :(3)
I.Myocardial hypoxia :
1.This may be anoxic in origin due to a reduction of oxygen
concentrations in the inspired atmosphere to :
- obstruction to the upper respiratory tract.
- failure of adequate movement of the chest.
- a diffusion block at alveolar level
2.As result from extreem hypotension and gross anemie with milder hypotension, or under ventilation.
3. Massive pulmonary embolus or air embolus produce inadequate coronary perfussion.
4.Certain poisons such as cyanide which inhibits cytochrome oxydase system and prevent cellular oxygenutilization.
II. Hypercapnia
Secondary to obesity or chronic lung disease
- Results in endogenous adrenaline release and hyperkalemia.
This more common occurence of cardiac arrest when the halothane as anesthetics.
III. Reflex stimuli :
Vagal stimulus such as occulocardiac reflex during traction on the extrinsix occular muscle.
IV. Overdosage of drugs or drug sensitivity :
- direct depression of the myocardium
- extreem hypotension
- hypoxia or hypercapnia following respiratory depression.
V. Changes of ionic environment :
- hyperkalemia in uremica or following massive transfusion or metabolic acidosis.
VI. Hypothermia :
- Slow the heart rate and depresss conduction if cooling is continued of about 15 degree Celcius asystole is produced
often preceded by ventricular fibrillation.
- The very rapid infusion of cold blood has been implicated in the causation of cardiac arrest.
VII. Mechanical stimulation
Incidental handling or retraction of the heart has resulted sudden ventricular fibrillation(VF).
VIII Electrical shock :
Death from electrocution from asystole or VF
IX. Intrinsix myocardial disease - coronary thrombosis.
INCIDENCE : (2)
Cardiac arrest more frequent :
1. In geriatric or pediatric
2. In patients with hystory of arrhythmia ,heart block myocard infarct (MI) or CHF.
3. In massive haemorrhage
4. During following heart surgery
PREVENTION :
The majority of studies that tend to promote cardiac arrest are preventable :(2)
A.Identification of high risk patient by careful attention to previous history of heart lung or kidney diseases, diabetes mellitus (DM),drug allergy or addiction and blood dyscrasia
B.Special attention should be given to following :
1. Maintainance of adequate volume.
2. Proper choice of preanesthetic medication.
3. Vagal stimulation by intubation or other maneuvers should be done during induction of anesthesia following hyperoxygenation.
4 .Blood loss during surgery must be check and replace properly.
5. Arterial blood gases,pH,and electrocytes must be monitored continously.
6. Respiratory insufficiency should be watched for and anticipated during recovery. Post operatively,respiration is frequently depressed and additional oxygen or assistance with a respirator may be necessary.
While a patient may be well ventilated during surgery,during recovery the patient may developed a progressive hypoxia and hypercapnia. Possibly leading an irritable myocardium into VF.
C.Avoid hazardous maneuvers :
Suctioning of the trachea in a hypoxic patient is often the stimulus for cardiac arrest.
D.Induction of anesthesia must always be done very carefully particularly in high risk patients with the following precautious :
1. Continuous ECG monitoring
2. Use of chest or oesophageal stethoscope
3. Availability of a DC defibrilator.
4. Ready availability of all drugs for therapy of cardiopulmonary arrest.
There are five steps in the prevention of biologic death from sudden cardiac standstill(4)
1. Rapidly recognize cradiac an respiratory arrest, singly or
combination.
2. Immediately institute artificial ventilation.
3. Quickly provide tecniques that arificially circulate blood.
4. Promptly administer appropriate drug therapy.
5. Apply post resuscitative care procedures designed to minimize the detererious effect of the arrest.
PROGNOSIS IN CARDIAC ARREST :(7)
Prognosis after cardiac arrest is influenced by time to initiate basic cardiopulnary resuscitation (CPR) and advance cardiac life support(ACLS).
In addition prognosis after CPR is influenced by the type of initial arrhythmia, Patients experiencing tachyarrhythmia (ventricular fibrillation(VF) or ventricular
tachycardia(VT), generally have a better prognosis than patients experiencing asystole or PEA unless the PEA results from mechanically correctable from obstructive shock such as a tension pneumothorax or pericardial tamponade.
Arrhythmic arrest may be prepicitated by electrolyte abnormalities in critically ill patients. Review of the most recent laboratory data should be conducted early during resuscitation. Cardio pulmonary arrest in infants and children is rarely a sudden event. More commonly it is secondary to progressive respiratory or circulatory failure that deteriorates to asystole or pulseless cardiac arrest.If respiratory failure or arrest is treated promptly the child is likely to survive intact.If respiratory arrest is allowed to progress to pulseless cardiac arrest, the outcome is poor.
Therefore early initiation of oxygenation and ventilation is the utmost importance.
0 comments:
Post a Comment