BT_RT 1.30 Outline how the clinical signs of shock may be altered by age

I love this time of year ….

This quite a good LO for making you think about the differences in the cardiovascular system and associated reflexes throughout the age spectrum. If you know what happens to the CVS as we age, then you should be able to predict what may happen in times of stress.

Many of you will be familiar with the ATLS grading of haemorrhage and the associated signs. These are not great for predicting blood loss the elderly, can you think why…

All of these statements should be within your capabilities.

Miller’s Anaesthesia has a chapter on Geriatric Anaesthesia which discusses the physiological changes in the elderly.

BT_RT 1.30 Outline how the clinical signs of shock may be altered by age

Tachycardia is likely to be less pronounced in a patient of 80 compared to one of 40 with the same degree of blood loss T/F

The baroreceptor reflex becomes progressively less effective with increasing age T/F

High resting sympathetic tone in the elderly, has more of an effect on α-adrenoreptor responsiveness compared with β -adrenoceptor responsiveness T/F

Elderly patients with septic shock are more likely to present with hypothermia than younger individuals T/F

Hypotension is a sign of severe shock in children T/F (the added complication of this one is knowing what is the normal blood pressure for your paediatric patient)

SS_PA 1.23 Temperature regulation in the newborn

Photo via National Geographic

Any of you who have been at the birth of a child or involved with anaesthesia of a neonate, will probably have guessed that little humans are not fantastic at keeping themselves warm, especially when wet. Everything is done to naked babies under a warming lamp and they are wrapped up at the earliest opportunity – no that is not just to make them look even cuter! They are also not great at cooling down when in a hot environment, although this tends to a bit less of an issue as they have a high thermoneutral zone.

It seems that even baby animals, like the cubs above, adapted to living in a cold environment, are similarly vulnerable to heat loss as newborns (according to these fun facts)

As with the last two posts, my go to book for this topic would be Power and Kam.

SS_PA 1.23 Define the thermoneutral zone, describe temperature regulation in the neonate and the physiological responses to lowered and raised environmental temperature, the effects of anaesthesia on these responses and how this changes with growth and development

The body surface area/weight ratio of an newborn is a third that of an adult T/F

The main source of heat production in a neonate is non shivering thermogenesis, which can increase the basal metabolic rate of the neonate by 3x T/F

The thermoneutral zone for a term newborn is around 32-34° C T/F

Preterm newborns have a lower thermoneutral zone compared with term babies T/F

Neonatal hypothermia increases the risk of hypoxaemia  T/F

Newborns have a decreased ability to sweat compared with adults T/F

SS_PA 1.22 and SS_OB 1.3 Respiratory system changes at birth

 

Yesterday I discussed the cardiovascular changes at birth. Today we will move to the respiratory system. The CVS changes are amazing, but I think the respiratory system ones are even more so – to think that humans, and in fact all mammals, are able to establish an effective means of respiring within seconds of being born is super cool!

Again, this topic is covered in most physiology books.

SS_PA 1.2  Describe the circulatory and respiratory changes that occur at birth

SS_OB 1.3 Describe the transition from foetal to neonatal circulation and the establishment of ventilation

In the first breaths after birth both inspiration and expiration are active processes T/F

The negative inspiratory pressure generated on the first breath is around 70-100 cmH2O T/F

Before the onset of respiration a neonate’s PaO2 may approach 15mmHg T/F

Hypoxia is the sole driver for onset of respiration at birth T/F

FRC is established within 4 breaths T/F

Have a look over at aGasgal to find a diagram I find helpful when thinking about the onset of respiration.

To give yourselves a bit more a mental challenge, and to apply the physiology to a clinical situation, what are the implications on the establishment of FRC to resuscitation of a neonate?

Think about the usual safety features of a bag-valve-mask ventilator. Can the safety features be bypassed? If so, how? Do they need to be?

Does it make a difference if the baby has primary apnoea (has never taken a breath) or secondary apnoea (stops breathing some time after respiration starts)?

SS_PA 1.22 and SS_OB 1.3 Cardiovascular changes at birth

 

 

Being born is tough! No wonder newborn infants often have a wizened look to them 😉. Within seconds and minutes of being born huge changes occur to both the cardiovascular and respiratory systems. Some of these changes are irreversible, but the neonate keeps its options open and, for a few days at least, elements of  the cardiovascular system can revert to the foetal status, especially if the baby is under physiological stress.

Tomorrow I will do a post on the respiratory changes at birth, but for today we will stick with the cardiovascular. Most physiology textbooks will cover this topic, Power and Kam’s book gives quite a detailed account, and here is a link to an article in the BJA Education on the topic (be mindful that there is an erratum published – I hope that shows in the link). It is a good idea to revise the foetal circulation before tackling this topic (there is a section on that in the above article)

SS_PA 1.22 Describe the circulatory and respiratory changes that occur at birth

SS_OB 1.3 Describe the transition from foetal to neonatal circulation and the establishment of ventilation

 

Loss of the placental circulation at birth results in both an increase in the neonate’s systemic vascular resistance and a fall in pulmonary vascular resistance T/F

Neonatal pulmonary vessels have the capacity for hypoxic pulmonary vasoconstriction T/F

The ductus arteriosus closes within minutes of birth, preventing any L to R shunting of blood T/F

Cardiac output in the hours after birth is substantially lower than it is at 8 weeks of age T/F

A newborn’s cardiac output is sensitive to changes in heart rate T/F

A newborn infant will often respond to hypoxia by becoming tachycardic, to improve cardiac output  T/F

SS_PA 1.25 Describe the composition of body fluids in the neonate and explain the changes that occur with growth and development

TRUE/FALSE  Term neonates have a lower percentage of total body water compared with adults

TRUE/FALSE  Serum albumin levels are lower in neonates compared with adults

TRUE/FALSE  Gastric pH is alkalotic at birth

TRUE/FALSE  Neonatal serum glucose levels are generally higher than those of older children

TRUE/FALSE Term neonates have a lower percentage of total body fat compared with adults

SS_PA 1.24 : paediatric physiology

Not a bad textbook, Evers & Maze… But rubbish for paediatric pharmacodynamics… So I’ve swapped over to some paediatric physiology instead. I used Miller as it was handy.

SS_PA 1.24 Describe the physiology of the cardiovascular, respiratory, renal and neurological systems in the neonate and the changes that occur with growth and development and the implications of this for anaesthetic care

During the first 2 weeks of age a neonate can flip back into a foetal circulation   TRUE/FALSE

The neonate has more compliant ventricles than an adult   TRUE/FALSE

Infants have more type I muscle fibres in their diaphragm   TRUE/FALSE

Neonates have decreased intracardiac calcium stores   TRUE/FALSE

Oxygen consumption in infants is higher than in adults   TRUE/FALSE