عدد الرسائل : 195
العمر : 47
تاريخ التسجيل : 27/07/2008
|موضوع: Anesthesia of Heart failure patients السبت أغسطس 02, 2008 3:56 am|| |
Heart failure is associated with perioperative morbidity and mortality. Acute heart failure may present as pulmonary oedema (LVF) or hypoperfusion (cardiogenic shock). Chronic or congestive cardiac failure is typically described with peripheral oedema and an elevated JVP.
Aetiology of heart failure
Right heart failure Left heart failure
Chronic lung disease Ischaemic heart disease
Chronic pulmonary thromboembolism Dilated cardiomyopathy (idiopathic, alcohol, myocarditis, familial)
Primary pulmonary hypertension Hypertension
Right ventricular cardiomyopathy Drugs (beta-blockers, Ca-channel blockers, antiarrhythmics)
Sepsis, HOCM*, restrictive cardiomyopathy, hypo- or hyperthyroidism
* Hypertrophic obstructive cardiomyopathy.
Diuretics: reduce peripheral and pulmonary congestion.
Vasodilators: ACE inhibitors (and angiotensin-II receptor antagonists) and nitrates.
Anticoagulants: reduce the incidence of thromboembolic events.
Beta-blockers: occasionally used by cardiologists if controlling the heart rate outweighs the risks of myocardial depression.
History and examination should identify present or recent episodes of decompensated heart failure (any within 6 months adversely affects risk). Attempts should be made to identify a cause for any decompensation (recent MI, new anaemia, progression of disease, or non-compliance with drugs).
ECG: may suggest aetiology, and comparison with previous traces may explain deterioration.
Chest radiograph: if symptoms are stable and the last one is less than 12 months old it does not need repeating.
Echocardiography should be performed in poorly controlled patients and for quantification of degree of cardiac dysfunction
Perioperative mortality is high and increases with worsening left ventricular dysfunction. Non-essential surgery should be avoided. Where possible perform surgery under a local or regional block.
Postoperative admission to HDU/ICU should be arranged before starting major surgery. In some centres preoperative admission for optimization is considered.
Sedative premedication is generally well tolerated except for cor pulmonale when even a slight worsening of hypoxia or acidosis can increase pulmonary vascular resistance and exacerbate heart failure.
Patients on digoxin and nitrates should receive them preoperatively. Digoxin should be given IV postoperatively if the patient is in AF but can usually be safely omitted until a patient is eating again if they are in sinus rhythm. Nitrates can be given transdermally whilst the patient is not eating.
ACE inhibitors should generally be given preoperatively, although a degree of hypotension on induction is to be expected. Postoperatively they should be resumed as soon as the patient is absorbing. If they have been omitted for 3 or more days they should be reintroduced at a low dose to minimize the first-dose hypotensive effect.
Diuretics are often omitted preoperatively as the patient may lose an unknown intravascular volume and is to receive a vasodilating anaesthetic. Postoperative diuretic requirements vary and should be given after consideration of fluid balance and measured cardiovascular variables.
Following central neuraxial blocks it may be necessary to prescribe a dose of diuretic to compensate for the contraction of the intravascular space that occurs when the block wears off.
Anaesthetic technique should minimize negative inotropy, tachycardia, diastolic hypotension, and systolic hypertension. No technique is clearly superior but these high-risk anaesthetics should be given by an experienced anaesthetist. Measurement of CVP is valuable and this may be complemented by use of intra-arterial BP, PAOP measurement, or oesophageal Doppler/transoesophageal echo.
Renal perfusion is easily compromised in these patients-monitor hourly urine volumes. If the urine output falls, hypovolaemia should be excluded and adequate perfusion pressure ensured before diuretics are used even if a preoperative dose has been omitted. NSAIDs are a potent renal insult in these patients and their use requires care.
All patients should have supplemental oxygen for 3 to 4 days after major surgery.
Good analgesia is essential to minimize the detrimental effects of catecholamine release in re