This type of surgery with reference to the heart involves harvesting
veins taken from the periphery (especially the legs) and subsequently
utilized to bypass significant atherosclerotic plaque blockages
of coronary arteries (see figures
121a and
121b). This type of surgery of the internal mammary arteries
are also used to bypass the blockages.
The major complications after coronary artery
surgery are bleeding requiring reoperation, myocardial infarction,
stroke ,respiratory distress wound infection and renal failure.
Patients who experience one or more complications have an eight
to ten times greater probability of mortality comport with those
who sustain no complications . Length of hospital stay and costs
are affected by most of these major complications. Important
predictors of morbidity include previous cardiac surgery, emergency
operation, advanced age, peripheral vascular disease, and preoperative
elevated serum creatinine. These indicators affect myocardial
and respiratory status but do not predict bleeding or wound
infection with the same accuracy.
Bleeding
The propensity for bleeding is multifactorial,but
relates to advanced age ,use of antiplatelet type drugs preoperatively,
prolonged operating time, previous cardiac surgery , and less
frequently, preoperative coagulopathy. Aspirin taken within
a week to ten days after coronary bypass
surgery has been associated with an increased rate of
bleeding, increased use of blood and blood products, and longer
intensive care unit hospitalization. Newer products such as
fibrin glue and aprotinin are reported to decrease postoperative
bleeding. The routine use of preoperative tests in accessing
bleeding risk is not justified. Need for transfusions relates
to body surface area, preoperative anemia ,and advanced age
more than any other factors.Erythropoietin has been used to
increase red blood cell production after autologous blood donation
;however, its role in postoperative anemia is not yet defined.
Myocardial Infarction
In elective coronary bypass surgery the transmural
.myocardial infarction rate is approximately two% The rate of
preoperative myocardial infarction is less in low risk patients
and greater in high risk patients, i.e., reoperations and coronary
arterial operations combined with other cardiac surgery. The
rate of myocardial infarction has declined in each decade from
the nineteen seventies to the nineteen nineties, presumably
because of better myocardial protection. The large Q wave infarctions
seen in the early days of coronary bypass surgery are infrequent
today. Transient abnormal Q. waves may occur as a result of
alterations in ventricular depolarization or maybe unmassed
by improved function of a contiguous ventricular segment. Patients
who experience nonfatal perioperative myocardial damage have
essentially the same intermediate- term course as patients without
the myocardial infarction. The exceptions are those who require
intraaortic balloon pumping for ischemia/infarction postoperatively.
although postoperative intraaortic balloon pumping is required
and only one to two percent of the elective surgeries today,
most studies have shown that the requirement for balloon pumping
portends the lower survival rate because these patients tend
to have complicated preoperative infarctions.
Strokes
The mechanism of stroke after cardiac surgery
including embolization, hypoperfusion or inflammatory responses
stimulated byextracorporeal circulation. Ascending aortic atherosclerosis
is a major contributor to brain damage and myocardial complications.
Aortic disease is to be suspected in patients with diffuse brachiocephalic
disease, documented peripheral vascular disease, or left main
coronary artery narrowing and is demonstrated directly by palpable
plaquediscovered during cannulation or construction of aortic
anastamoses. It has been shown recently that aortic atheroemboli
more frequently in patients undergoing coronary artery surgery
than other cardiac procedures. Acorrelation between increased
incidence of atherembolism, advanced age,and peripheral vascular
disease is apparent. The surgeon should anticipate finding aortic
atherosclerosisa before entering the aorta. The problem may
be circumvented by femoral artery or distal arch cannulation.
If atherosclerosis is discovered during the construction of
bypass grafts, the ascending aorta should be open and debrided,
possibly under deep hypothermia. Obviously signs of aortic atherosclerosis
contraindicate aortic cross- clamping. In situ internal thoracic
arteries should be used if the subclavian artery is a widely
patent. Vein grafts or other arterial conduits may be anastomosed
directly to the internal thoracic arteries.
Respiratory distress
Respiratory distress has been related to lengthy
operating time; increase number of blood transfusions; increased
amount of crystalloid fluid infusion; suboptimal preoperative
nutritional status of the patient ;presence of intrinsic pulmonary
disease, neuro logical deficit o r phrenic nervedysfunction;
and cardiac failure. Congestive heart failure during the operation
is the most important risk factor for postoperative pulmonary
complications. This complication is relatively infrequent in
otherwise uncomplicated patients. Pneumonia may be at related
to prolonged intensive care unit stay, presence of chronic obstructive
pulmonary disease, administration of gastric acid inhibitor
drugs and prolonged mechanical ventilation support and may be
prevented by keeping long- term intensive care unit patients
in the head -up position to avoid aspiration, providing oral
hygiene, frequent sterile suctioning,and use of sucralfate for
the stress ulcer prophylaxis rather than antacids or H2 antagonists.
The role of selected digestive decontamination is not fully
settled.
Wound infections
Sternal wound infection with mediastinitis
occurs in approximately one% of elective coronary bypass patients
and usually detected around the seventh to ninth postoperative
day.In unusual cases this complication may arise several weeks
postoperatively.The mortality related to mediastintis is high
(14%). Wound infection increase hospital cost more than any
other nonfatal complication because of the protracted hospitalization
related to chest wall reconstruction .Wound infections are more
likely to occur in diabetic patients. Use of the internal thoracic
artery is not a risk factor for wound complications except in
bilateral usage in diabetic patients Treatment is surgical drainage
and by either primary closure or treatment with rotational muscle
flaps.
Renal failure
Renalfailure may be the result of underlying
renal disease, especially when coupled with cardiac instability
postoperatively.Vasopressor use intraaorticen balloon pumping,
excessive bleeding, history of chronic renal disease, and advanced
age are predictors of postoperative renal failure. Some studies
have supported the use of low dose dopamine to increase renal
blood flow as a protective measure.
Abdominal complications
Though rare, the most common abdominal complication
is gastrointestinal hemorrhage due to esophagitis o rgastritis.Pancreatitis
is correlated with low cardiac output and multisystem complications.
Patients who have the history oof pancreatititis and suffer
complications postoperatively may be prone to recurring pancreatitis
.
Atrial fibrillation
Atrial fibrillation may be a source of emboli
postoperatively. Advanced age is related to atrial dysrhythmias.The
incident of atrial fibrillation varies from a low of four percent
in patients less than 40 years of age to more than 50 percent
in patients more than 75 yearsold. The risk of incurring new
atrial fibrillation appears to be independent of advanced coronary
atherosclerosis or even left ventricular function .The number
of factors such as beta blocker withdrawal ,lenghty operation
and post cardiotomy syndrome have been implicated but none herald
atrial fibrillation consistently. Electrical conversion to normal
sinus rhythm may cause embolization,and prophylactic oral anticoagulation
has been advocated.
Other complications
Other infrequent complications include brachial
plexus injuries, whichmay be related to spreading the sternum
and compressing the plexus between the clavicle and the firsr
rib with resultant transient median nerve trauma Pulmonary embolism
is rareLower extremity wound complications are unusual but cellulitis
may occur in diabetic patients with poor circulation.
In the first few months after hospital discharge
the clinician should be vigilant for pericarditis/pleuritis,
wound infections, a triall arrhythmias, epatitis and recurrent
angina. Pulmonary embolism is rarel but should be suspected
in those who have a protracted hospital course or who have a
history of pulmonary embolism or phlebitis.
ANGINA
RELIEF AND LIFESTYLE
Return to work is a complicated subject.Since
the median age of coronary bypass patients is approaching 65
years and is older in many communities, return to full activity
may be a more realistic expectation. Nonetheless, factors affecting
return to work include the status of employment preoperatively,
age, income, gender, self employment, whether white collar or
blue collar, college education,relief of symptoms, and preoperative
left ventricular function. It is known that the longer the unemployment
preoperatively, the less likely the return to full employment.
Other factors that adversely affect future employment include
comorbidity, physician advice, and disability compensation.
It is advised that the patient consult with his cardiologist
and consider a stress ECG test to determine his ability to run
on the treadmill without symptoms and ischemia, and compare
the lifting of heavy boxes, stair climbing etc to the stress
on the treadmill to gain an insight as to whether the patient
can do the preoperative job safely without symptoms or ischemia.