Keywords: anesthesia for coronary heart disease
Second, the narcotic treatment
Coronary heart disease anesthesia and perioperative hemodynamic management principles to maintain myocardial oxygen supply and demand balance, avoid the aggravation of myocardial ischemia. Myocardial oxygen uptake rate, which amounts to 60 to 65%, usually when the increase in myocardial oxygen consumption, the only way to increase coronary blood flow to provide, but in patients with coronary heart disease coronary reserve capacity is low, it is difficult to complete the increase in oxygen consumption matches the blood flow and myocardial ischemia, therefore, want to maintain myocardial oxygen supply and demand balance, as much as possible to reduce myocardial oxygen consumption. To do this you should:
1, to avoid an increase in myocardial oxygen demand (oxygen consumption] factors:
The influencing factors of myocardial oxygen consumption (1) myocardial contractility; (2) ventricular wall tension by its ventricular systolic and end-diastolic pressure; (3) heart rate. Perioperative myocardial oxygen demand increases, usually due to high blood pressure and / or increased heart rate. Faster heart rate in addition to increased myocardial oxygen consumption and myocardial blood flow regulation. Animal experiments suggest that: in the case of a normal heart rate, endocardial autoregulation pressure low limit of 38mmhg, automatically adjust the pressure when the heart rate faster times, low rose 61mmhg only. This suggests that the faster heart rate, want to maintain the same number of myocardial blood flow supply, you need a higher perfusion pressure. The other faster heart rate, left ventricular diastolic time, the decline in coronary blood flow. Perioperative heart rate remained stable, to avoid increased heart rate, control of heart rate in the preoperative the quiet state level (before CPB heart rate slower than 70bpm, of downtime and postoperative heart rate is generally not more than 90bpm) clearly favor the myocardial oxygen the supply and demand balance. Clinical data show that the probability of myocardial ischemia decreased heart rate slower than 70bpm patients. Surgery anesthesia management point of view from the Fuwai cardiovascular disease hospital cabg after the heart rate Piankuai proportion (cpb 90 years ago 87% of the cases, the heart rate of more than 90bpm) larger unstable anesthesia after surgery a higher mortality rate. 90 years to control heart rate, anesthesia after postoperative recovery more smoothly than before, the significant decline in operative mortality, mortality after 95 years has reached the international advanced level. Although cabg surgery mortality is influenced by many factors, perioperative maintain a stable heart rate, to avoid adding to myocardial ischemia, played a very important role.
Arterial blood pressure on myocardial oxygen supply and consumption balance plays a double role. Blood pressure increase in oxygen consumption, but also increase coronary perfusion pressure and increased myocardial blood supply. Intraoperative and postoperative blood pressure fluctuations of myocardial oxygen supply and consumption balance is extremely unfavorable, perioperative blood pressure should be maintained stability.
Left ventricular cardiac output and left ventricular end-diastolic volume (lvedv) is closely related to the stroke, but lvedv increase so lvedp to rise to more than 16mmhg significant increase in myocardial oxygen consumption. In addition to patients with low cardiac output should be maintained higher lvedp (14 ~ 18mmhg), in patients with coronary heart disease lvedp should not exceed 16mmhg (combined valvular disease except).
Myocardial contractility significantly to ensure that the cardiac output is essential, but no history of myocardial infarction before surgery, cardiac function is still good patient, moderate inhibition of myocardial contractility is conducive to the maintenance of myocardial oxygen supply and demand equilibrium.
2, to avoid reducing myocardial oxygen supply
Myocardial oxygen supply depends on coronary blood flow and oxygen content. Coronary blood flow depends on coronary perfusion pressure and ventricular diastolic time. Under normal circumstances, the automatic adjustment of the coronary blood flow with a pressure range (50 to 150mmhg), but patients with coronary heart disease due to coronary artery blockage, the lower limit of the range automatically adjusts the pressure rose sharply, so perioperative blood pressure should be maintained a higher level, and especially with hypertension and even more so. Coronary blood flow occurs mainly during diastole, so the the diastolic the length of time is another decisive factor in determining myocardial blood flow. Therefore, perioperative avoid increased heart rate, not only can reduce myocardial oxygen consumption, and is also essential to ensure that the myocardial blood flow perfusion.
According poisseuille formula, coronary flow q = πr4 △ p/8lη (r-radius, △ p-drive pressure, l-tube length, η-viscosity). Be seen from the formula, the most important factor to affect coronary blood flow, in addition to the driving pressure (perfusion pressure), that is, the coronary resistance. Systolic and diastolic coronary caliber, will be the fourth power of the amplitude of the r affect coronary blood flow, perioperative reduce coronary tension to avoid coronary spasm, ensure myocardial blood supply is also crucial .