Dead Space Ventilation

Dead space is the volume of air which is inhaled but does not take part in gas exchange either because it remains in the conducting airways or in alveoli that are poorly perfused i.e. not all the air in each breath is able to be used for the exchange of oxygen and carbon dioxide.

 The total dead space (also known as physiological dead space) is the sum of the anatomical dead space plus the alveolar dead space.

Anatomic dead space

Approx one-third tidal volume ~150mL in a healthy adult.

Alveolar dead space

• Sum of the volumes of alveoli which have little or no blood flowing through their adjacent pulmonary capillaries i.e., alveoli that are ventilated but not perfused, and where, as a result, no gas exchange can occur.
• Alveolar dead space is negligible in healthy individuals, but can increase dramatically in some lung diseases due to ventilation-perfusion mismatch.

References

• http://en.wikipedia.org/wiki/Dead_space_(physiology)
• http://www.paramedicine.com/pmc/End_Tidal_CO2.html

Plateau effect

Takes 4-5 half lifes for a medication to reach plateau effect.

Cryoprecipitate

• A frozen blood product prepared from plasma
• Each 15 mL unit typically contains 100 IU of factor VIII, 250 mg of fibrinogen, as well as von Willebrand factor (vWF) and factor XIII.
• Used commonly for DIC to keep fibrinogen levels > 1.0.
• 1 unit of cryo per 5kg patient weight will increase fibrinogen by about 100 mg/dL. Therefore number of bags = 0.2 x weight (kg) to provide about 100mg/dL fibrinogen.
• Many institutions use a standard dose of 10 units and then repeat if needed.

References

• http://en.wikipedia.org/wiki/Cryoprecipitate
• http://reference.medscape.com/drug/cryo-cryoprecipitate-999498
• http://www.transfusion.com.au/sites/default/files/iTRANSFUSE%202.2%20CRYO.pdf
• http://www.perthhaematology.com.au/cryo.ht

Anuric renal failure

Anuric renal failure

• Urea rises by 10 per day, Cr rises by 100 per day

References

• http://www.rph.wa.gov.au/nephrology/Acute_renal_failure.html
• http://www.doctorslounge.com/nephrology/diseases/acute_renal_failure.htm
• http://web.up.ac.za/sitefiles/file/45/1335/4101/Tuesday%20Academic%20Meetings/N%20Grabowski%204%20May%202011%20diagnosis%20of%20renal%20failure.pdf

Management of VF arrest

Passive rewarming

• Temperature is very important during rewarming as temperature commonly overshoots normal. Warming the patient too quickly or allowing continued shivering causes dangerous electrolyte shifts, leading to potentially lethal arrhythmias. 
• Controlled rewarming of 0.15° to 0.5° C per hour is recommended. 
• To maintain tight temperature control throughout rewarming a neuromuscular blockade is usually employed.  
• Careful fluid monitoring during rewarming is crucial because of the vasodilation that accompanies a body temperature rise. Volume replacement may be needed to prevent fluid deficit and hypotension.
• Electrolytes shift out of the cells back into the serum during rewarming, so frequent electrolyte monitoring is needed during this phase to prevent critically elevated levels. Slow, controlled rewarming allows the kidneys to excrete excess potassium, preventing hyperkalemia. 
• Hypoglycemia can occur during rewarming as the insulin resistance of earlier hypothermia phases diminishes. Glucose levels must be monitored frequently, with insulin titration and dextrose boluses used as needed to maintain the patient within ordered ranges.

References

• http://www.americannursetoday.com/article.aspx?id=8014&fid=7986
• http://ccforum.com/content/16/S2/A25/