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LABETALOL (TRANDATE, NORMODYNE, PRESOLOL)

Description

Labetalol is an alpha-1 and beta-adrenoreceptor receptor blocker. It is used to treat hypertension, hypertensive emergencies, chronic angina and heart failure. It is also used to treat hypertension in pregnancy. It is suitable for treating hypertension due to phaeochromocytoma. See Phaeochromocytoma. It decreases blood pressure by decreasing SVR.

Dose

Adult (to treat hypertensive emergency)

IV bolus 20 mg over 2 min followed by 40 mg then 80 mg × 3 at 10–20 min intervals as needed. IV infusion dose 20 mg/h increased at 20 min intervals to a maximum of 160 mg/h. No more than 300 mg/24 h by any route.

Advantages

  1. Does not cause significant hypotension.

  2. Can be used during pregnancy, for intracranial diseases requiring BP control and after MI.

  3. Low doses can be used in patients with LV failure.

Disadvantages

  1. Contraindicated in heart block and bradycardia.

  2. Contraindicated in patients with asthma.

LACTATE

NR 0.3–1.3 mmol/L. Lactate is produced by anaerobic metabolism, hence a rise in serum lactate reflects tissue hypoperfusion. Serum lactate correlates well with the degree of hypovolaemic shock due to haemorrhage. Elevated lactate levels improve as tissue oxygenation improves and there is increased liver perfusion (where lactate is metabolised).

LAPAROSCOPIC SURGERY

Creation of the pneumoperitoneum

A pneumoperitoneum is created by insufflating gas, usually CO2, into the peritoneal cavity. The gas is insufflated at a rate of 4–6 L/min initially then at 200–400 mL/min to maintain the pneumoperitoneum. An intra-abdominal pressure (IAP) of 10–15 mmHg is sufficient for most procedures.

Physiological effects of pneumoperitoneum

Cardiovascular

  1. Creation of a pneumoperitoneum can result in severe bradycardia or asystole due to vagal reflexes. In addition to releasing the gas, treatment includes:

    1. atropine 600 mcg IV

    2. circulating the atropine with CPR if asystole or severe bradycardia.

  2. Do not give adrenaline 1 mg for this type of asystolic arrest.

  3. Increased IAP causes autotransfusion of pooled blood in the gut, increasing venous return to the heart and cardiac output (CO). However, if IAP > 20 mmHg, the IVC is compressed, decreasing venous return and CO.

  4. In the head-up reverse Trendelenburg position there may be venous pooling in the lower limbs with decreased venous return from the legs causing a reduced CO.

  5. Increased IAP increases SVR by compressing the abdominal aorta. SVR is also increased by raised blood catecholamine levels. This maintains or increases mean arterial pressure (MAP), and causes tachycardia. This can lead to ischaemia in patients with ischaemic heart disease. See Ischaemic heart disease (IHD).

  6. Diaphragmatic elevation, due to increased IAP, leads to increased intrathoracic pressure, decreasing venous ...

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