Are anesthetics safe? The National Halothane Study was a major investigation of the safety of anesthetics used in surgery. Records of over 850,000 operations performed in 34 major hospitals showed the following death rates for four common anesthetics:
Anesthetic A B C D
Death 1.7% 1.7% 3.4% 1.9%
There seems to be a dear association between the anesthetic used and the death rate of patients. Anesthetic C appears to be dangerous.
A) Select the best explanation for why we call the National Halothane Study an observational study rather than an experiment, even though it compared the results of using different anesthetics in actual surgery.
B) When the study looked at other variables that are confounded with a doctor's choice of anesthetic, it found that Anesthetic C was not causing extra deaths. Suggest several variables that are mixed up with what anesthetic a patient receives.

a) We call the National Halothane Study an observational study rather than an experiment, because the anesthetics were not randomly chosen. They were prescribed by the doctors.

An experiment is conducted based on random observations not on certain selected observations.

b) There are factors such as age, sex, intensity , limit, tolerance and reactivity of the patient with the particular anesthetics chosen. If these are not carefully studied the results may not be as rewarding as desired.

If an anesthetics is chosen wihtou knowing the age or blood type for tolerance it may result in dangerous situations.

Some patients are highly tolerant with certain medications but others may die.