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Physiology of Pregnancy
Published in Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal, Principles of Physiology for the Anaesthetist, 2020
Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal
About 15% of pregnant women, when near term, develop hypotension, pallor, nausea and vomiting when they are supine. This is known as the supine hypotension or aortocaval compression syndrome. The ill effects of the supine hypotension syndrome may be seen as early as the 20th week of gestation. Compression of the inferior vena cava (IVC) by the gravid uterus decreases the venous return and reduces the cardiac output (Figure 72.3). Blood returns to the heart via the paravertebral epidural veins draining into the azygos vein. Uterine perfusion is diminished because of increased uterine venous pressure. Compression of the aorta may also be present and may be associated with uterine arterial hypotension and reduced uteroplacental perfusion. The supine hypotension syndrome can be prevented by positioning the mother on her left side.
Maternal and neonatal physiology
Published in Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal, Principles of Physiology for the Anaesthetist, 2015
Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal
About 15% of pregnant women, when near term, develop hypotension, pallor, nausea and vomiting when they are supine. This is known as the supine hypotension or aortocaval compression syndrome. The ill effects of the supine hypotension syndrome may be seen as early as the 20th week of gestation. Compression of the inferior vena cava (IVC) by the gravid uterus decreases the venous return and reduces the cardiac output (Figure 14.3). Blood returns to the heart via the paravertebral epidural veins draining into the azygos vein. Uterine perfusion is diminished because of increased uterine venous pressure. Compression of the aorta may also be present and may be associated with uterine arterial hypotension and reduced uteroplacental perfusion. The supine hypotension syndrome can be prevented by positioning the mother on her left side.
Analgesia nociception index as a tool to predict hypotension after spinal anaesthesia for elective caesarean section
Published in Journal of Obstetrics and Gynaecology, 2021
Ali Jendoubi, Aymen Khalloufi, Oussama Nasri, Ahmed Abbes, Salma Ghedira, Mohamed Houissa
Caesarean delivery is one of the most frequently performed surgical procedures. Spinal anaesthesia (SA) is the global standard method of anaesthesia for caesarean section (Hawkins et al. 1997). However, this anaesthetic technique has also its downsides, and the major one is hypotension which occurs in 55–90% of cases with significant maternal and foetal implications (Mercier et al. 2007). Maternal hypotension is caused by aortocaval compression syndrome and sympathetic blockade (Mercier et al. 2007). Hypotension causes many adverse effects for the mother and foetus. The mother can experience nausea and vomiting. If prolonged, this hypotension can result in bradycardia and cardiac arrest (Macario et al. 1999). As for the child, several complications can occur such as depressed Apgar scores and foetal acidemia, which have been correlated with severity and duration of hypotension (Mueller et al. 1997). Previous research studies have been undertaken in obstetric anaesthesia practice to find effective preventive and treatment strategies to deal with this important clinical problem. Prophylactic measures such as co-loading or vasoactive drugs can reduce the incidence and severity of this complication (Ngan Kee et al. 2000; Kluger 2000). A wide panel of methods have been described to identify parturients at high-risk of developing hypotension after SA such cardiovascular measurements that are not part of routine monitoring, complex processed cardiovascular indices. Some are based on different ways of analysis of heart rate variations (HRV) (Chamchad et al. 2004; Hanss et al. 2005).