The relation of peri-operative blood pressure changes to post-operative complications is complex and controversial. The topic can be divided into three areas:
- Pre-operative hypertension
- Intra-operative lability
- Post-operative (recovery room) hypertension
Not discussed are causes of technical problems measuring blood pressure
Although chronic anti hypertensive therapy has been shown to reduce much of the morbidity, e-S. congestive heart failure, chronic re” failure, and cerebrovascular accidents associated with hypertension, the evidence linking pre-operative hypertension to post-operative complications is weak. Although Prys-Roberts found that pre-operative hypertensive patients have more blood pressure lability peri-operatively and the treatment of the hypertension decreases this lability, Goldman found no relationship between pre-operative hypertension and post-operative complications. Hypertension is not one of the risk factors in his cardiac risk index.
Goldman’s study can be criticized because of an insufficient number of patients with severe hypertension. However, his conclusion that “. . . elective surgery in the absence of ideal anti-hypertensive therapy need not subject patients to added clinical risk provided, a) diastolic pressure is stable and not higher than 110 torr, and b) intra-operative and recovery room blood pressure values are closely monitored to prevent hypertensive and hypotensive episodes. . ” has become accepted clinical practice
Historically, the relationship between intra-operative events and post-operative outcome has been tenuous. Rao and El Etra’s paper demonstrating a marked decrease in post-operative reinfarction rate also showed a much higher incidence of reinfarction in patients having intra-operative hemodynamic abnormalities, mainly hypertension, hypotension, and tachycardia. In fact, some believe the improvement in the reinfarction rate may have been due to the prevention of these hemodynamic abnormalities rather than the use of invasive monitors.
Keats and Slogoffs study at the Tom Heart Institute showing a relationship between intraoperative ischemia and post-operative infarction also showed that “ischemia was significantly more common in patients who had hemodynamic abnormalities (hypertension, hypotension, or tachycardia) both before and during anesthesia”. Hypertension and tachycardia were much more frequent than hypotension, and tachycardia seemed to be most poorly tolerated.
Therefore, there is now a moderate amount of evidence indicating that intra-operative blood pressure changes lead to post-operative cardiac complications and that the dose control of blood pressure peri-operatively will decrease these complications.
Post-operative blood pressure abnormalities are first and foremost an indication to look for an underlying problem. If a patient is hypotensive, hypovolemia and surgical bleeding should be suspected. If a patient is hypotensive, pain, respiratory, failure, hypoxia, bladder or gastric distention, and fluid overload should be considered and the patient examined. Post-operative relative hypertension usually occurs within 30 minutes of surgery and is quite common. Up to 50% of hypertensive patients undergoing surgery -M have postoperative hypertension. Although studies have shown postoperative hypertension to be transient (lasting less than four hours) and generally well tolerated, it is prudent and accepted clinical practice to treat this hypertension in elderly, high risk patients. Labetatol has become a popular, effective and safe first line drug for recovery room hypertension.
Over-all, careful attention to blood pressure management can be an important component of maximizing anesthesia patient safety
Dr. Tully is a staff anesthesiologist at the New England Deaconess Hospital, Boston.
1. Prys-Roberts C. Hypetension and anesthesia fifty years on. Anesthesiology. 1979; 50:281-283.
2. Goldman L, Caidera DL Risk of general anesthesia and elective operation in the hypertensive patient. Anesthesiology. 1979; 50:285-292.
3. Goldman L et al. Multifactorial index of cardiac risk in non-cardiac surgical procedures. NEJM. 1977; 297:845-850.
4. Rao TLK, locobs KH, 11 Etra AM. Reinfarction following anesthesia in patients wtffi nwocanhal mmrchon. Anesthesiology. 1983; 59:499-505.
5. Slogoff W, Keats HS. Does pen-operative myocardial ischemia lead to post-operative myocardial infarction. Anesthesiology. 1985; 62:107-114.
6. Gal 11, Cooperman LH. Hypertension in the immediate post-operative period. Br 1. Anaesth. 1975;47:70.