A 59-year-old woman has a history of chronic kidney disease for the past 1 year. During her recent health check-up, her blood pressure was found to be 170/100mmHg. How should the blood pressure for this patient be managed?
This is an extremely common scenario. Chronic kidney disease (CKD) is defined as having decreased kidney function (eGFR<60ml/min/1.73m2) or proteinuria for more than 3 months. Hypertension (systolic pressure > 140mmHg) is known to affect 90% patients with CKD. Hypertension is both a cause and a consequence of CKD. As both are risk factors for cardiovascular disease (CVD), co-existence of these two conditions further increase CVD morbidity and mortality.
CKD and hypertension- the connect
Functionally damaged kidneys send afferent signals which increase the sympathetic tone. Moreover, as eGFR declines, there is activation of the renin angiotensin aldosterone system(RAAS) which further leads to increase BP. CKD is also associated with endothelial dysfunction and arterial stiffness which contributes to hypertension. Studies show that lowering BP, slows down eGFR decline, delay progression to end stage renal disease (ESRD) and reduce risk of CVD.
Controlling BP in patients with CKD
Achieving BP control is quite challenging in patients with pre-existing disease like CKD. The guidelines recommend that all patients with CKD should maintain a target BP of <130/80mmHg, especially if high BP is associated with protein leak.
Non pharmacological measures to reduce BP
Studies show that reducing salt intake to less than 3 grams a day (< 1.5 teaspoon) can decrease systolic BP by nearly 10mmHg. Reduced salt intake (<6gm/day) is also associated with reduction in proteinuria by around 25%. Weight-loss can also reduce BP as well as proteinuria and slow CKD progression. In patients who are overweight, a mean weight loss of around 4 % can reduce proteinuria by almost 30%.
Pharmacological management of hypertension
Certain medications have BP lowering as well as renal and cardioprotective actions. Thus, the choice of drugs should depend on the desired outcomes. In most patients with CKD, a combination therapy may be needed to achieve blood pressure targets.
- ACE inhibitors and ARBs:
Drugs that block renin angiotensin mechanism confer cardio-protection and renoprotection too. These drugs are favored, especially in patients with proteinuria, as they reduce BP by approximately 20mmHg and also reduce proteinuria. Combination therapy with ARBs and ACE inhibitors is contraindicated owing to increased risk of adverse events and no significant reduction in progression of CKD or ESRD risk. Another concern is that, RAAS blockade can lead to complications like hyperkalemia and acute kidney injury. Plus, after initiating RAAS blocking therapy there is an initial rise in serum creatinine. But, the guidelines tell us that rise in serum creatinine for up to 30% with subsequent stabilization after initiating ACE inhibitors or ARBs is acceptable as they provide long term renoprotection. However, use of these drugs are still questionable in patients with advanced CKD (eGFR< 30mL)
Volume overload is seen in more than 50% patients with CKD. Thus, diuretics is frequently administered in CKD patients for its BP lowering and cardioprotective effects. In non-proteinuric CKD, thiazide diuretics can be first choice. Loop diuretics like furosemide is needed in higher doses for CKD with lower eGFR as the tubular mechanism of action is dependent on glomerular filtration. Diuretics should be avoided in patients with CKD due to polycystic kidney disease. Mineralo-corticoid receptor antagonist like spironolactone and eplerenone are not recommended for CKD patients as they carry a risk of exacerbating hyperkalemia.
- Calcium channel blockers(CCBs):
Dihydropyridines CCBs (amlodipine) and non- dihydropyridines (verapamil) are safe and effective in reducing BP in CKD patients; they can be given as monotherapy or along with RAAS blockers. Non dihydropyridines have been found to have better effect than dihydropyridines in controlling blood pressure.
- Beta blockers:
Beta blockers are also effective in reducing BP in CKD owing to their sympathomimetic effect which confers additional cardiovascular protection. Though these drugs can be safely used in CKD patients, there are some concerns regarding glycemic control and systemic accumulation due to decreased renal excretion. Beta blockers should be considered along with RAAS blockade especially when CVD coexists.
- Alpha blockers:
Alpha blockers like Doxazosin are usually used as combination therapy for managing BP in CKD. These drugs are not affected by reduction in eGFR and also have favorable glycemic profile. But these should not be used as first line therapy as they are not very effective in preventing CVD.
Reduction of blood pressure in patients with CKD is of utmost importance. Lifestyle and drug therapy- both play an important role in reducing blood pressure. Medications should be chosen based on the patient characteristics- like severity of CKD, coexistence of CVD etc. However, more than the choice of drug, achieving adequate blood pressure control should be the primary objective in treating patients having hypertension with CKD.