ANSWER:
A patient is admitted hypotensive with E. Coli sepsis.

The consultant asks for gentamycin and adds:

"Please don't under-dose"

Why is the initial dose of gentamycin so important?
Gentamycin, like other aminoglycosides exhibit concentration dependent killing

The initial phase of rapid bacterial killing is induced
by passive ionic binding of the drug to bacterial lipopolysaccharide.

The killing rate is directly related to
initial drug concentration
A second phase of slower bacterial killing is associated with decreased energy-dependent uptake of the aminoglycoside

This rate is independent of the initial drug level
Being exposed to aminoglycosides causes bacteria to down-regulate this uptake.

Subsequent doses are therefore not as effective as the initial dose as they rely on the second phase of action.
SO the first dose needs to be high as you are relying on the high peak of concentration to carry out the bulk of the genocide.

Thereafter, resistant survivors will respond poorly.

journals.asm.org/doi/pdf/10.112…

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More from @GUH_ICU_Anaesth

28 Sep
1/8
You are asked to preoperatively assess a patient with known primary severe mitral regurgitation for an hip replacement

Which of the following new findings might result in you postponing surgery:

Dilated LV
Impaired LV sys fxn
Pulmonary HTN
New Afib Image
2/8

Answer:

Any/all of the above

If known severe MR – these are the NEW findings that should prompt you to speak to you friendly cardiologist colleagues Image
3/8

Valvular Heart Dx (VHD) AHA guidelines : Image
Read 9 tweets
14 Sep
1/13 - GUH Echo tweetorial:

The tricuspid regurgitation jet velocity shown was used in a critical care patient to estimate RV systolic pressure:
Vol control – tvol 420ml PEEP 10cmH20
Cardiovascular: MAP 67mmHg on Noradrenaline 0.3mcg/kg/min
2/13
His TRVmax is high:
Why should I not diagnose this patient with pulmonary hypertension in my echo report?

2 are correct:
a. not steady state
b. Off axis cursor
c. Echo cannot diagnose it
d. Poor 2D view
3/13
Answer:
a, c and possibly b!

Lets start with what TR vmax means and how it is calculated
Read 14 tweets
14 Sep
GUH Images in Anaesthesia and ICU:

The tricuspid regurgitation jet velocity shown was used in a critical care patient to estimate RV systolic pressure:

Vol control – tvol 420ml PEEP 10cmH20

Cardiovascular: MAP 67mmHg on Noradrenaline 0.3mcg/kg/min
His TR Vmax suggests his RV systolic pressure is 51mmHg + RA pressure = HIGH

I am conscious that I should not diagnose this patient with pulmonary hypertension in my echo report:

Why?
Read 4 tweets
24 Jun
1/14
GUH - Echo Tweetorial - Aortic Stenosis:

How do they calculate:
1. Valve area
2. Mean AV gradient
3. Max AV gradient
2/14
Essential Principles:
1. The effective orifice area is always smaller than the anatomical orifice area
This effective orifice area is what is calculated
It is the key determinant of survival
2. Continuity equation
Conservation of mass
3/14
Continuity equation:
A2 X V2 = A1 x V1
(AVA) x (AV VTI) = (LVOT CSA) x (LVOT VTI)
AVA = [(LVOT CSA) x (LVOT VTI)]/ AV VTI
Read 15 tweets
22 Jun
GUH - images in Anaesthesia and ICU:
In anticipation of our Level 2 echo tweetorial series

This is a zoomed image of a valve during a level 2 scan

1. Name the valve
Name the valve:
For bonus points -

Name the transthoracic echo view:
Read 11 tweets
21 Mar
1/6
Answer:

LA myxoma

And for those of you who still auscultate the precordium you would have heard the elusive 'tumour plop'....of course you would.

But lets get back to the basics of M- Mode use in the PLAX view
2/6
Firstly the AV:
Here is a normal m-mode image through the AV during the cardiac cycle - note:
1. How systole and diastole are identified by ECG
2. Opening of the RCC and NCC to form the 'envelope'
3. Symmetry of the envelope
4. Closure line at end syst. Image
3/6
Compare this to m mode in severe AS where there is no identifiable opening of the cusps: Image
Read 6 tweets

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