Peri-operative management of hypertension Speaker Dr. Tipu Sultan Co-ordinator Dr.Chavi Sethi(M.D.)
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.