BT_PO 1.9 Hypoxia

Hypoxia is a strong driver to increase respiratory rate. TRUE/FALSE.

The aortic body peripheral chemoreceptors are the most important peripheral chemoreceptors in humans. TRUE/FALSE.

The central chemoreceptors respond directly to changes in the H+ concentration in the CSF. TRUE/FALSE.

Inflation of the lungs that is detected by pulmonary stretch receptors increases respiratory rate. TRUE/FALSE.

Rapid breathing in left heart failure is potentially due to stimulation of the junta-capillary receptors. TRUE/FALSE.

BT_PO 1.79 : Acid-base chemistry

BT_PO 1.79 : Describe acid-base chemistry using the Henderson-Hasselbach equation and strong ion difference

 

The SID in NaCl is 0 mmol/L        TRUE/FALSE

Normal Se Cl is approximately 100 mmol/L        TRUE/FALSE

The normal SID in plasma is approximately 40 mmol/L        TRUE/FALSE

Large volumes of NaCl as a replacement fluid can take the Se Cl to around 120 mmol/L (not that I would know as this is not routinely reported in my hospital)…

Administering large volumes of NaCl causes a metabolic acidosis by decreasing the SID    TRUE/FALSE

Administering large volumes of NaCl causes a metabolic acidosis by impairing renal bicarbonate absorption with the chloride load        TRUE/FALSE

Hypoalbuminaemia will give a metabolic acidosis        TRUE/FALSE

 

BT_PO 1.79 : Acid-base chemistry

Third in my series on acid base physiology, see last week’s post for the suggested reading material…

BT_PO 1.79 : Describe acid-base chemistry using the Henderson-Hasselbach equation and strong ion difference (SID)

So Stewart would look at this LO and say, yes, those 2 factors are important, but you also have to consider the dissociation of water, and the amount and dissociation of the non-volatile weak acids in the system. 

The independent variables in his model are SID, and volatile (pCO2) and non-volatile acids.

pCO2 is controlled by the lungs        TRUE/FALSE

SID is controlled by the liver        TRUE/FALSE

Albumin levels are controlled by the kidney        TRUE/FALSE

Acid-base differences across a membrane are predominantly from CO2 as it crosses membranes so easily        TRUE/FALSE

Acid-base differences across a membrane are predominantly from proteins as they cross membranes so poorly        TRUE/FALSE

Pulmonary Circulation

An overall increase in vascular tone reduces blood volume within the pulmonary circulation. TRUE/FALSE

Pulmonary arterial pressure is much less then the systemic arterial pressure, although the capillary and venous pressure are not greatly different in the two circulations. TRUE/FALSE

Pulmonary vascular resistance tends to fall as flow increases. TRUE/FALSE

The arterioles are the main point providing resistance in the pulmonary vasculature. TRUE/FALSE

The greatest drive for hypoxic pulmonary vasoconstriction is the pulmonary arterial Po2. TRUE/FALSE.

BT_PO 1.79 : Acid-base chemistry

BT_PO 1.79 : Describe acid-base chemistry using the Henderson-Hasselbach equation and strong ion difference

Strong ion difference (SID) refers to the Stewart approach to acid-base analysis. Stewart’s underlying tenet is that hydrogen ions are the dependent variable in a complex system of physico-chemical interactions, not simply an entity that is shuttled across membranes. He makes the point that water is a practically inexhaustible source of hydrogen ions as it is usually so minimally dissociated. As we saw yesterday, just raising the temperature of an aqueous solution will increase the dissociation of water leading to a higher [H+] – though it’s important to realise that it will remain at a neutral pH as the [OH-] increases equally. 

Peter Stewart’s book is available free on the internet but for the majority of you I would recommend Kerry Brandis’ work on the topic – Quantitative acid-base analysis.

Strong ions in solution are fully dissociated        TRUE/FALSE

Sodium, chloride and lactate are strong ions        TRUE/FALSE

pCO2 determines [H+]        TRUE/FALSE

The SID determines [H+]        TRUE/FALSE

If the SID is non-zero then electro-neutrality requires the presence of weak electrolytes    TRUE/FALSE

These weak electrolytes are predominantly weak acids        TRUE/FALSE

Albumin is the predominant weak acid in the body        TRUE/FALSE

There will be more on this topic after a brief foray into respiratory physiology 🙂

 

 

BT_PO 1.78 : Acid Base Regulation

BT_PO 1.78 : Describe the regulation of acid/base balance

Looking at the effect of temperature…

Decreasing temperature will decrease the solubility of carbon dioxide in blood     TRUE/FALSE

Arterial pCO2 will decrease as temperature drops for a given content of carbon dioxide     TRUE/FALSE

As temperature increases the dissociation of water increases      TRUE/FALSE

The pH of neutrality of water at 37 degrees C is 6.8       TRUE/FALSE

Blood at a pH of 7.4 is at a neutral pH       TRUE/FALSE

 

 

 

 

BT_PO 1.50 CVS and obesity

BT_PO 1.50   Describe the cardiovascular changes that occur with morbid
obesity

An increased extracellular volume may be a causative factor in hypertension in the obese  TRUE/FALSE

Blood volume per kg body weight is less in the obese than in the lean      TRUE/FALSE

Hyperinsulinaemia may be a causative factor in hypertension in the obese      TRUE/FALSE

A cuff that is too small will over-read the blood pressure in the obese      TRUE/FALSE

Fat blood flow is approximately 10 ml/min/100g      TRUE/FALSE

I have taken this from Hemmings and Hopkins Chapter 71 but the material is scattered throughout the recommended texts and can also be deduced if you have a good grasp of the topic

 

 

 

Ventilation and Perfusion

Since the pulmonary circulation operates at low pressure, the distribution of blood is similar to the distribution of ventilation. TRUE/FALSE

Alveoli with no ventilation will have PO2 and PCO2 values that are the same as mixed venous blood. TRUE/FALSE.

A pulmonary embolism is a shunt. TRUE/FALSE

Pulmonary capillary blood flow + Venous admixture = Cardiac Output. TRUE/FALSE

Venous admixture increases arterial blood carbon dioxide content above that of pulmonary end-capillary blood. TRUE/FALSE

Patient of the week – 2

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Another piece for the V&A, this made entirely from cutlery (I am drawing a long bow for today’s post)

Here is another case in this sporadic series

Some months ago I looked after a young patient who had been retrieved following a machete injury near the shoulder, resulting in almost total amputation of the arm. The injury had occurred some hours previously, with the patient left at the side of the road.

He had been intubated by the retrieval team at the scene.

On arrival to the Emergency Department his potassium level was 6.5 mmol/L

BT_GS 1.38

Normal serum potassium rise following an intubating dose of suxamethonium is 1.5mmol/L TRUE/FALSE

BT_PO 1.72

ECG changes associated with hyperkalaemia include tall peaked T waves and a shortened PR interval. TRUE/FALSE

He was taken to theatre to reattach the arm. He was hypovolaemic and anuric.

I set about trying to lower his serum potassium and restore his blood volume.

BT_PO 1.40

Salbutamol may be detected as halothane when nebulised within the circle circuit TRUE/FALSE

BT_PO 1.72

Calcium gluconate is used in the  management of hyperkalaemia as it lowers serum potassium TRUE/FALSE

BT_RT 1.9

Hyperkalaemia and hypercalcaemia are potential metabolic consequences of massive transfusion    TRUE/FALSE

To be honest, nothing I tired (and I tried a lot of everything I could think of, short of starting dialysis) lowered his potassium at all. But at least it didn’t increase any further. He survived the reimplantation  and was transferred to ICU for further management, including some much needed haemodialysis.

BT_RT 1.2 Integrate knowledge of factors determining cardiac output to classify causes of shock

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To fit with today’s theme is this photo of Tippoo’s Tiger, on display at the V&A Museum, London. This wind-up piece has an organ inside and when the handle was turned it supposedly “imitated the European victim’s dying wails of agony” – delightful! It was found in the music room of Tipu Sultan after his death in 1799

Let’s knock off another LO before we get started on the core business of today –

BT_RT 1.1  Define shock

Shock is defined as a state where tissue perfusion is inadequate to meet the metabolic requirements of that tissue     TRUE/FALSE

Ok, now for the main event. This topic is covered quite well in Oh’s Intensive Care Manual  and Guyton and Hall Textbook of Medical Physiology – details here. I suspect it is well covered in lots of places actually 😉

BT_RT 1.2 Integrate knowledge of factors determining cardiac output to classify causes of shock

All causes of shock are associated with an absolute reduction in cardiac output    TRUE/FALSE

Cardiogenic shock occurs when the heart is unable to pump blood sufficiently to maintain perfusion      TRUE/FALSE

Neurogenic shock and anaphylaxis are both examples of distributive shock  TRUE/FALSE

Anaesthesia may cause neurogenic shock     TRUE/FALSE

Hypovolaemic shock can be used to describe any form of shock where there is inadequate venous return   TRUE/FALSE

 

And finally one last photo of the tiger and its hapless victim…

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