Postoperative Pain and Angiotensin II Receptor Antagonists

An angiotensin II type 2 receptor (AT2R) antagonist has been assessed for its efficacy in neuropathic pain with promising results. A considerable number of patients undergoing surgery under general anesthesia are hypertensive and receive drugs to control high blood pressure, including angiotensin II receptor antagonists. These drugs may attenuate the acute and/or chronic postoperative pain or decrease the analgesic requirements after surgery. The aim of the present study is to assess the early postoperative pain and analgesic requirements in patients treated with antagonists of the angiotensin II receptors for at least three months before surgery compared to normotensive patients.

Patients ASA I-III, aged between 35 and 79 years old, with BMI ≤ 35, scheduled for abdominal surgery, thus gynecological, urological and general surgery procedures will be recruited for the study. All patients will be scheduled in the morning list, informed for the study and will be asked to give written informed consent.

Exclusion Criteria will be patients on analgesic, antidepressive, or sedative consumption during the previous one month, mental impairment, not speaking Greek or refusing to give written informed consent, diabetics, patients receiving antihypertensive treatment other than angiotensin type II receptor (AT2R) antagonists.

Two groups of patients will be stydied: Patients hypertensive (the hypertensive group) receiving treatment for blood pressure control with angiotensin II receptor antagonists for at least three months preoperatively and a normotensive group.

Measurements

* Pain intensity (visual analogue scale: VAS) from 0 to 100 will be reported 2, 4, 8, and 24 hours postoperatively with 0 representing no pain and 100 excruciate worst pain. Pain will be recorded at rest and subsequently patients will be asked to cough for three times.
* Analgesics consumed at the same time points will be recorded.
* Patient satisfaction (VAS 0-100) 24 h postoperatively (with special reference to pain)
* Three months postoperatively patients will be contacted by phone and will be asked if they experience pain related to surgery or not. If yes pain characteristics, thus burning, pricking etc. will be recorded.
* Three months postoperatively patients will be asked whether they used analgesics after discharge from the hospital for the postoperative pain.

Statistics Primary outcome of the study: Pain intensity 24 hours postoperatively after cough in patients receiving angiotensin II receptor antagonists, or no antihypertensive therapy. Secondary outcomes of the study are pain intensity 2, 4, 8 and 24 hours postoperatively at rest, 2, 4 and 8 hours after cough, analgesic consumption , 2, 4, 8 and 24 hours postoperatively, patient satisfaction regarding pain, presence of pain three months after surgery and if present its characteristics. Also, analgesic consumption during the first three months postoperatively due to surgery.

Statistics Power analysis: A 30% difference in pain intensity after cough 24 hours postoperatively between the angiotensin II receptor antagonists treated group compared and the treated group.

Acute pain at rest and after cough all the time points as defined by the study design will be compared between patients receiving antihypertensive treatment (angiotensin II receptors antagonists) and the controls.

Cumulative analgesics consumed 2, 4, 8 and 24 hours after surgery will be compared between the two groups.

The presence of chronic postsurgical pain and the need or not of analgesic intake due to chronic pain three months after surgery will be also compared between the hypertensive treated and normotensive patients.

Parametric or non-parametric tests will be used for normal and no normal distributions respectively.

Eligibility Criteria:
Inclusion Criteria:

* Patients aged between 35 and 79 years
* ASA II or III
* BMI ≤ 35
* Elective abdominal surgery Exclusion Criteria:-
* Patients on analgesic, antidepressive, or sedative consumption during the last month
* Mental impairment
* Not speaking fluently Greek language
* Refuse to give written informed consent
* Diabetics
* Patients receiving antihypertensive treatment other than angiotensin type II receptor (AT2R) antagonists