Book contents
- Frontmatter
- Contents
- List of contributors
- Foreword by Professor Lord Ara Darzi KBE
- Preface
- Section 1 Perioperative care
- Consent and medico-legal considerations
- Elective surgery
- Special situations in surgery: the diabetic patient
- Special situations in surgery: the jaundiced patient
- Special situations in surgery: patients with thyroid disease
- Special situations in surgery: steroids and surgery
- Special situations in surgery: surgical considerations in the pregnant woman
- Haematological considerations: thrombosis in surgery
- Haematological considerations: bleeding
- Haematological considerations: haemorrhage (massive-bleeding protocol)
- Haematological considerations: blood products and transfusion
- Shock
- Fluid management
- Electrolyte management
- Pain control
- Nutrition
- Antibiotic prescribing in surgery
- Critical care: the critically-ill patient, decision making and judgement
- Critical care: cardiovascular physiology and support
- Critical care: respiratory pathophysiology and support
- Critical care: renal support
- Critical care: other considerations
- Postoperative complications
- Surgical drains
- Abdominal stoma care
- Section 2 Surgical emergencies
- Section 3 Surgical disease
- Section 4 Surgical oncology
- Section 5 Practical procedures, investigations and operations
- Section 6 Radiology
- Section 7 Clinical examination
- Appendices
- Index
Critical care: cardiovascular physiology and support
Published online by Cambridge University Press: 06 July 2010
- Frontmatter
- Contents
- List of contributors
- Foreword by Professor Lord Ara Darzi KBE
- Preface
- Section 1 Perioperative care
- Consent and medico-legal considerations
- Elective surgery
- Special situations in surgery: the diabetic patient
- Special situations in surgery: the jaundiced patient
- Special situations in surgery: patients with thyroid disease
- Special situations in surgery: steroids and surgery
- Special situations in surgery: surgical considerations in the pregnant woman
- Haematological considerations: thrombosis in surgery
- Haematological considerations: bleeding
- Haematological considerations: haemorrhage (massive-bleeding protocol)
- Haematological considerations: blood products and transfusion
- Shock
- Fluid management
- Electrolyte management
- Pain control
- Nutrition
- Antibiotic prescribing in surgery
- Critical care: the critically-ill patient, decision making and judgement
- Critical care: cardiovascular physiology and support
- Critical care: respiratory pathophysiology and support
- Critical care: renal support
- Critical care: other considerations
- Postoperative complications
- Surgical drains
- Abdominal stoma care
- Section 2 Surgical emergencies
- Section 3 Surgical disease
- Section 4 Surgical oncology
- Section 5 Practical procedures, investigations and operations
- Section 6 Radiology
- Section 7 Clinical examination
- Appendices
- Index
Summary
Cardiovascular pathophysiology
The function of the circulation is to transport oxygen and nutrients to the tissues and to remove metabolic waste products. For this to happen, there must be:
▪ Enough oxygen in the blood
▪ Enough blood flowing (cardiac output)
▪ Enough blood pressure to let tissues regulate their own perfusion.
The oxygen content of the blood is determined by haemoglobin concentration and saturation.
Blood pressure
This is determined by the equation BP = CO × TPR.
(BP = blood pressure, CO = cardiac output, TPR = total peripheral resistance.)
Thus hypotension can be due either to low cardiac output or to inappropriate vasodilation. Treatment usually requires correction of theabnormal variable.
Cardiac output
Cardiac output is determined by the following:
Rate: too high a heart rate prevents adequate filling of the ventricle and reduces preload and cardiac output. Bradycardia reduces cardiac output as ejection simply does not happen often enough.
Rhythm: loss of atrial contraction in junctional rhythms or atrial fibrillation also reduces preload and hence cardiac output by up to 30%.
Preload: Starling's law states that the force of contraction of a cardiac muscle fibre is proportional to its initial length. The fibre length is determined by the ventricular volume. However volumes are difficult to measure clinically, and the simplest substitute is the central venous pressure (CVP). […]
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- Hospital SurgeryFoundations in Surgical Practice, pp. 108 - 112Publisher: Cambridge University PressPrint publication year: 2009