Complicated cardiac surgery

Complicated cardiac surgery

Impaired cardiac status

Impaired cardiac status may be improved by manipulating

· preload (adequate filling, elevation of legs)

· afterload (warming, correcting acidosis and filling)

· contractility (inotropic support +/- ventricular assist devices)

· heart rate (filling, correcting electrolyte imbalance, reassurance, sedation and analgesia, improving coronary perfusion by augmenting MAP and treating common dysrhythmias such as AF with digoxin amiodorone and cardioversion)

· optimizing oxygenation by correcting supply and demand imbalance)

Impaired respiratory status

Respiratory complications arise in the cardiothoracic patient as a result of a combination of the following

· prolonged CPB (microemboli)

· mitral valve surgery (pulmonary changes from long term disease)

· IMA grafts (lower lobe collapse due to internal mammary harvesting)

Treatment is aimed at

· maintaining adequate TV and Peep to reduce V/Q mismatch and recruit more alveoli

· vigorous bronchial toilet and bronchodilation

· therapeutic humidification

· therapeutic positioning

· gradual titration of oxygen therapy <> 60-80 mmHg

· gradual titration of Peep to 5 mmHg

· gradual titration of PPS

· may require PCV

· careful planning of pain medication, strict 2 hrly DB & C, earliest possible mobilisation (SOOB), high flow oxygen therapy with intermittent CPAP may be necessary

· patients who do not wean successfully progress to surgical tracheostomy day 7-10 post-operatively See chapter 4

Renal impairment

Acute renal failure may result due to CPB (if prolonged), decreased MAP (decreased renal blood flow and glomerular filtration rate)

Management is aimed at

· maintaining se K+ and se Cr within normal limits (check at least daily)

· managing oliguria with increasing cardiac output (MAP > 80 mmHg)

· managing oliguria with renal dose dopamine infusion (2.5 mcg/kg)

· managing oliguria with optimising preload

· diuretics and K+ lowering therapy as in Chapter 5.

Impaired neurological function

Neurological sequalae occur in 1-5% of patients. Strokes and coma are primary manifestations. Altered mental state occurs in 30% of patients and range from psychosis to depression. Patient’s response to a request to open eyes and wriggle toes indicate an ability to hear, process and respond to command as well as motor abilities and should be assessed ASAP on return from theatre.

Impaired gastrointestinal function

The following gastrointestinal manifestations are commonly seen in the cardiothoracic setting

· liver dysfunction (low cardiac output, hypoxaemia, haemolysis, pre-existing portal hypertension)

· gastric ulceration

· ischaemic bowel

· paralytic ileus

Management is aimed at

· early recognition and Rx

· observing and reporting N/G loss, any blood in aspirate or malaena may be indicative of active ulceration

· Ranitidine IV may be used for patients with a history of gastric ulcers, or those who may be under prolonged stress due to complicated recovery phases

· liver dysfunction usually resolves without intervention(avoid medications metabolised in and excreted by the liver)

· paralytic ileus usually resolves without intervention (light diet, N/E feeding and mobilisation encourage return of peristalsis)

· ischaemic bowel is confirmed radiologically if suspected clinically

Fluid and electrolyte imbalance

· for se K+ <> 4 uEq/L

· for se K+ >5 uEq/L, potassium should be removed from the IV fluids and levels measured 4hrly until normal

· for se K+ >6 uEq/L, 12 units actrapid in 50 mls 50% dextrose should be infused IV over 10 minutes and K+ repeated in 1 hour

· if treatment is ineffective Resonium A 20 mgm is given via the N/G tube and K+ repeated in 1 hour

Haematological system impairment

Clinical signs of haematological impairment are

· bleeding (>200mls/hr, total>2000mls post-operatively)

· tachycardia

· anaemia

· decreased tissue perfusion

· alteration in gaseous exchange

Treatment is aimed at

· correcting hypothermia (decreased platelet aggregation)

· maintaining MAP 65 mmHg

· ACT > 150 give 50 mgm Protamine Sulphate, unless contraindicated

· ACT <>

· if bleeding continues despite normal ACT and platelet transfusion, desmopressin 0.4 mcgm/kg in 100 mls Normal Saline over 1 hour may reduce the need for blood transfusion

· therapy for continued bleeding may include aminocaporic acid or aprotinin (contact haematology department at the level of registrar or above)

· extended coagulation profile may be performed in selected cases if DIC is suspected

· liver function tests should be performed to exclude liver dysfunction

Altered body temperature

Alteration below and above a narrow body temperature range activates a physiologic response in an attempt to regain core temperature. Induced hypothermia during cardiac surgery provides metabolic quiescence and myocardial preservation.

Detrimental effects of hypothermia are

· decreased platelet activation

· haemo-concentration / capillary sludging

· sinus bradycardia, conduction defects, atrial fibrillation / flutter

decreased susceptibility to cardioversion