Peri-operative management of hypertension

Speaker Dr. Tipu Sultan

Co-ordinator Dr.Chavi Sethi(M.D.)

Peri-operative HypertensionHypertension occuring in the pre-operative,

intra-operative or post-operative period.

Importance:Increased risk of cardiovascular events,e.g.

myocardial ischemiaIncreased post-operative morbidity and mortalityAssociation with end-organ damage such as renal

failure.

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Effects of Peri-operative hypertensionCVS effects:

Increased BP→ ↑ afterload & myocardial oxygen demand → myocardial oxygen supply and demand imbalance.

Chronic ↑ BP → myocardial hypertrophy → myocardial oxygen supply and demand imbalance

Hypertrophied myocardium → decreased compliance → abnormal diastolic filling

Diastolic dysfunction especially apparent during stress, important during surgery and acute recovery interval

CNS effects:Increased risk of strokeImpaired cerebral autoregulationEspecially important in neurosurgical patients

Effects on renal functionEffective control of BP prevents renal

dysfunction Intraoperative urine output monitoring for

assessment of perioperative renal function

Pre-operative concernsPreoperative evaluation important to

identify patients with hypertension and initiate appropriate therapy.

When to diagnose hypertension?

Single reading of elevated BP in patient with previous undiagnosed or untreated HTN not reliable, subsequent readings in non-stressful environment required. (White Coat Hypertension)

Stage 1 or stage 2 hypertension (systolic blood pressure < 180 mm Hg and diastolic blood pressure < 110 mm Hg) not independent risks for perioperative cardiovascular complications, hence cancellation not always justified.

On initial evaluation, hypertension mild or moderate & no associated metabolic or cardiovascular abnormalities, do not delay surgery.

Stage 3 hypertension (systolic blood pressure ≥ 180 mm Hg and diastolic blood pressure ≥ 110 mm Hg) should be controlled before surgery.

More prone to perioperative ischemia, arrhythmias and cardiovascular lability, but no clear cut difference that deferring and anesthesia decreases perioperative risk.

Patients with newly diagnosed mild hypertension, treatment may be delayed till after surgery.

Management of anaesthesia in hypertensive patients:

Preoperative evaluation-Determine adequacy of blood pressure controlReview pharmacology of drugs being

administeredEvaluate for evidence of end organ damageContinue drugs used for control of blood pressure

The incidence of hypertension and evidence of myocardial ischemia during maintenance of anesthesia is increased in patients who are hypertensive prior to induction of anesthesia.

Also the magnitude of blood pressure decreases during anesthesia is greater in hypertensive than in normotensive patients.

Preoperative history and examinationEnd-organ damageAssociated cardiovascular pathologyCurrent anti hypertensive medications

To be continued during perioperative period Special care regarding β-blockers and clonidine

Patients with preoperative HTN, more likely to develop intra-operative hypotension. (ACE inhibitors)

Preoperative β blockers:ControversialProven to be beneficial in cardiac surgeriesFor non-cardiac surgeries good results in high-

risk patients but not in low-risk patients (NEJM 1996, 2005)

Associated with lesser incidences of perioperative ischemia

Intraoperative hypotension, precipitation of asthamatic attack, major disadvantage

Preoperative ACE inhibitors & AT-1 antagonists:Controversy regarding exaggerated

hypotensionAs long as euvolumia, no hypotension

Pts. with preoperative BP elevations; exaggerated intraoperative BP fluctuations & ECG evidence of ischemia.

Preop. Control of BP; ↓tendency to perioperative ischemia.

Controversy over when to delay surgery and at what BP to accept the patient

Individualize the patientAnaesthesiologists perogativeHospital protocol

Induction and maintenance of anaesthesia:

Anticipate exaggerated blood pressure response to anesthetic drugs

Limit duration of direct laryngoscopyAdminister a balanced anesthetic to blunt

hypertensive responsesConsider placement of invasive hemodynamic

monitorsMonitor for myocardial ischemia

Intraoperative concernsTarget range for intraoperative BP control:

BP days to weeks before surgeryPresence of associated comorbidityType of surgery

Maintained within 20% of the preoperative level

Stressful intraoperative events:IntubationSurgical incisionEmergence from GA and extubation

Other causes of intra-operative hypertension:Inadequate depth of anesthesiaPainHypercarbiaHypoxemiaBladder distensionHypervolumia

Exaggerated response in hypertensive patientsIncreased sympathetic toneDecreased intravascular volume

Methods to blunt the sympathetic response:

IV Esmolol (1-2mg/kg, studies with lesser dose 0.4mg/kg)

IV Lignocaine( 1.5 mg/kg, 90 sec before intubation/extubation)

Short acting narcotics (Fentanyl 2-3µg/kg, sufentanil 0.3-0.5µg/kg)

Increased concentration of inhalational agents (MAC-ei, MAC-bar-ei)

IV NTG (1-2µg/kg, just before beginning laryngoscopy)

IV Labetalol (5-20 mg boluses)

Preoperative use of β-blockers or clonidine, smoothen intraoperative blood pressure course.

Choice of anesthetic techniques and medications on the basis of presence of comorbid disease and type of surgery. (avoid ketamine)

Hypertensive patients treated with diuretics or having LVH more susceptible to vasodilatory effects of inhaled anesthetics & neuraxial blockade

Intraoperative Hypertension The most likely intraoperative hypertension

produced by painful stimulation, i.e., light anesthesia. the incidence of perioperative hypertensive episodes is increased in patients with essential hypertension, even if the blood pressure was controlled preoperatively

Volatile anesthetics are useful in attenuating sympathetic nervous system activity responsible for pressor responses

Monitoring Monitoring in patients with essential hypertension

is influenced by the complexity of the surgery. Electrocardiography is particularly useful in

recognizing the occurrence of myocardial ischemia during periods of intense painful stimulation such as laryngoscopy and tracheal intubation.

Invasive monitoring with an intra-arterial catheter and a central venous or pulmonary artery catheter may be useful if extensive surgery is planned and there is evidence of left ventricular dysfunction or other significant end-organ damage.

Transesophageal echocardiography is an excellent monitor of left ventricular function and adequacy of intravascular volume replacement

Postoperative concernsPostoperative Hypertension: Arbitrarily

defined as SBP>190 mm Hg and/or DBP≥100 mm Hg on two consecutive readings following surgery

Implications:Risk of hemorrhageDisruption of vascular or cardiac suture linesCerebral edema↑ myocardial wall stress and oxygen

consumption→ myocardial ischemia

Causes:Preoperative hypertensionWithdrawal of antihypertensive medicationsPainEmergence deleriumHypoxiaHypercarbiaHypothermiaHypervolumiaType of surgery

Management:Aggressive pain managementCorrection of previously mentioned causesAntihypertensive medications

Parenteral Rapid onset Labetalol, hydralazine

Refractory or profound hypertension SNP or NTG

Preoperative Systemic Blood Pressure Status

Incidence of Perioperative Hypertensive Episodes (%)

Incidence of Postoperative Cardiac Complications (%)

Normotensive 8[*] 11Treated and rendered normotensive

27 24

Treated but remain hypertensive

25 7

Untreated and hypertensive

20 12

 Risk of General Anesthesia and in Hypertensive PatientsElective Surgery

In hypertensive patients who exhibit signs of target organ damage, postponement of an elective procedure is justified if that end-organ damage can be improved or if further evaluation of that damage could alter the anesthetic plan.

Isolated Systolic Hypertension (ISH)Systolic blood pressure>140 mm Hg with a

normal diastolic blood pressurePrevalent in elderly population (steady

increase in systolic pressure with age)Studies have described association

between ISH and cardiovascular complications in non-cardiac surgery (Aronson et al, Franklin et al)

No definitive studies for non-cardiac surgery

Recent clinical trial and observational study data show closer association of systolic BP with CAD and stroke Vs diastolic BP

Recommendations for aggressive treatment of ISH, especially in pts.> 65 yrs

Further studies required to assess anesthetic risk

Acute Hypertensive CrisesHypertensive emergencies, sudden increase in

systolic and diastolic blood pressure associated with end organ damage of the CNS, the heart , or the kidneys.

Hypertensive urgencies, severely elevated BP without acute end-organ damage.

Malignant hypertension, syndrome characterized by elevated BP accompanied by encephalopathy or nephropathy

SBP >169 mm Hg or DBP >109 mm Hg in a pregnant woman is considered a hypertensive emergency

Majority are previously diagnosed for HTN, on irregular treatment

The rate of rise more important than the absolute level

Pathophysiology:

Abrupt ↑ in systemic vascular resistance (humoral vasoconstrictors)

Severe elevations of BP→ endothelial injury → fibrinoid necrosis of the arterioles → deposition of platelets and fibrin → breakdown of the normal autoregulatory function.

Resulting ischemia → release of vasoactive

substances

Hypertensive crises

Hypertensive encephalopathy Acute aortic dissection Acute pulmonary edema with LVFAcute myocardial infarction/unstable angina Eclampsia Acute renal failure Pheochromocytoma crisis

Clinical features:

Those of end organ damage Hypertensive encephalopathy (headache, altered

consciousness, CNS dysfunction) Retinopathy (blurring of vision) CVS (angina, acute MI) Cardiac decompensation Renal (renal failure with oliguria and/or hematuria)

Management of Hypertensive crisesHospital Care (urgencies), ICU care (emergencies)Invasive BP monitoring for emergencies

Lower the BP + stabilize and reverse the damage to target organs

Sodium restriction and diuretics if fluid overload

Parenteral anti-hypertensives (emergencies), oral/parenteral (urgencies)

Drugs Dosage

Diazoxide IV injection of 1 to 3 mg/kg to maximum of 150 mg given over 10 to 15 min; may be repeated if inadequate response.

Enalaprilat IV injection of 1.25 mg over 5 min every 6 h, titrated by increments of 1.25 mg at 12- to 24-h intervals to a maximum of 5 mg every 6 h.

Esmolol Loading dose of 500 µg/kg over 1 min, followed by an infusion at 25 to 50 µg/kg/min, which may be increased by 25 µg/kg/min every 10 to 20 min until the desired response to a maximum of 300µg/kg/min.

Fenoldopam An initial dose of 0.1 µg/kg/min, titrated by increments of 0.05 to 0.1 µg/kg/min to a maximum of 1.6 µg/kg/min.

Labetalol Initial bolus 20 mg, followed by boluses of 20 to 80 mg or an infusion starting at 2 mg/min; maximum cumulative dose of 300 mg over 24 h.

Nicardipine 5 mg/h; titrate to effect by increasing 2.5 mg/h every 5 min to a maximum of 15 mg/h.

NTG Infusion @ 5 µg/min, increase by 5 µg/min every 3- 5 min

Nitroprusside 0.5 µg/kg/min; titrate as tolerated to maximum of 2 µg/kg/min.

Phentolamine 1- to 5-mg boluses; maximum dose, 15 mg.

Trimethaphan 0.5 to 1 mg/min; titrate by increasing by 0.5 mg/min as tolerated; maximum dose, 15 mg/min.