Sondra Vazirani, M.D., M.P.H.
Postoperative hypertension is a common entity encountered by internists and other consultants. The cause of the hypertensive episode must be determined in order to adequately treat the patient. Acute urinary retention is one of several causes of postoperative hypertension that can easily be found during the physical exam.
A 67-year-old Caucasian man with a history of hypertension and benign prostatic hyperplasia had a recurrence of head and neck cancer. He had postoperative hypertension two hours after undergoing a modified radical neck dissection and tracheostomy. Despite receiving eleven 20mg doses of IV labetalol, he continued to be hypertensive with blood pressures of 190's systolic over 100's diastolic. He was awake and alert, complaining of postoperative pain. He did not have blurry vision or chest pain. He claimed to have had good preoperative blood pressure control and to have taken all his blood pressure medications in the morning with a sip of water. The patient had post-surgical changes on neck exam, a systolic ejection murmur, and a full, palpable bladder. A foley catheter was inserted and over 600cc of urine collected. The patient's blood pressure came down rapidly to 156/89.
Postoperative hypertension is a well-described complication resulting from surgical intervention. The frequency of postoperative hypertension ranges from 3% in all comers to 34% of those undergoing coronary revascularization.1 Other authors have reported incidences as high as 75%, depending on the procedure performed. Post-operative hypertension occurs not only in those with pre-existing uncontrolled hypertension, but also in those who were normotensive or well controlled with medication.2 However, pre-existing hypertension may increase the likelihood of difficulty in hemodynamic control both intra- and postoperatively.3
Postoperative hypertension is an issue that requires attention. Hypertensive patients, as we know, can develop end organ damage with sequelae ranging from stroke to myocardial infarction to renal failure. From a surgical standpoint, hypertension can lead to wound edema and increased bleeding.
Intraoperatively, blood pressure can fluctuate from a variety of manipulations. Laryngoscopy and intubation lead to sympathetic stimulation. Upon awakening and extubation, there can be another rise in blood pressure. Hypertension can also occur from other immediate postoperative conditions such as pain and hypothermia.2
The acute increases in blood pressure in postoperative patients are largely thought to be a result of a hyper-adrenergic state caused by the multiple stressors of surgery. The sympathetic stimulation lead to elevated levels of norepinephrine.1 This results in increased systemic vascular resistance.
There are many reversible factors that contribute to postoperative hypertension. Uncontrolled pain is a common cause.3 Secondly, volume overload during surgery can lead to elevated blood pressures. It is not uncommon for patients to receive liters of fluid in the operating suite. Even later in the postoperative course, patients can once again have increased intravascular volume from mobilization of fluids from the "third space." Hypercarbia and hypoxia can also contribute to postoperative hypertension.
Another issue to consider is the patient's preoperative blood pressure status. Often, I see patients with postoperative hypertension who likely had poor blood pressure control preoperatively. The EKG may have signs of left ventricular hypertrophy and the patient may have sequelae of untreated hypertension such as renal insufficiency or history of strokes. Withdrawl from antihypertensive medications is another concern on the differential diagnosis. Patients should be asked what medications they were taking prior to the OR, to see if they happened to stop ingestion close to the perioperative period.
Other rare causes of hypertension must be considered when combined with unusual clinical responses. For example, wide swings in blood pressure may make one consider an undiagnosed pheochromocytoma. These patients have long-term catecholamine stimulation that results in intravascular hypovolemia.3 These patients require volume repletion and adrenergic blockade immediately.
History and physical exam are important in patients with postoperative hypertension. Aside from inquiring about the patient's hypertensive history and regimen, it must be determined whether the patient has a hypertensive urgency or emergency. Patients should be asked about blurry vision or chest pain. A fundoscopic exam should be performed, as well as looking for signs of end organ damage, such as congestive heart failure or evidence of stroke. The history and physical can determine whether the patient warrants oral versus intravenous medication and whether postoperative care should be given in an intensive setting.
A reversible cause of postoperative hypertension that is not as medication sensitive and can be easily diagnosed on physical exam is bladder distension. Urinary retention is thought to cause hypertension, not only through pain mechanisms, but also via elevated renin levels excreted from the kidney.4 In the clinical example above, the patient received large doses of intravenous labetalol without significant blood pressure effect. This patient was at high risk for urinary retention given his history of benign prostatic hyperplasia and the lack of an intraoperative foley catheter. In this case, a distended bladder was easily noted on exam and the intervention of foley catheter placement resulted in speedy resolution of his hypertensive urgency.