Power is the probability that a study will reject the null hypothesis. difference between the null and alternative hypotheses. level of significance, and the null vs. alternative difference. a numeric example of power and sample size estimation for the one-sample case.
During the procedure the patient is unconscious and unaware of the need to urinate. After the procedure, however, it may not be safe for the patient to walk. They may be too sick to take care of their own bathroom needs or their surgeon may feel that a catheter is best for their particular recovery.
Placement or removal of a spinal catheter should be delayed for at least 12 hr after administration of prophylactic doses (eg, doses used for DVT prevention) Longer delays (24 hr) are appropriate to consider for patients receiving higher therapeutic doses (eg, enoxaparin 1 mg/kg BID or 1.5 mg/kg qDay)