Anaesthesia and Hypertension

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Anaesthesia and Hypertension

Introduction

· Pre-operative assessment

· Leading cause of death

· Commonest co-morbidity encountered

· Frequent pre-op abnormnality

· Prevalence : 20- 25 %

· White coat hypertension: elevated blood pressure taken in hospital setting despite normal blood pressure in a normal ambulatory setting

Definition

· Disorder , basal level of arterial pressure, higher than expected for age and gender

· Normal systolic : approximate normal BP' age + 100

· Take two or more reading taken on separate occasions

Complication of hypertension

· Myocardial infarction

· Stroke

· Renal failure

· Peripheral vascular disease

· Aortic dissection

Pre-operative assessment

Asessment of blood pressure control

· History of hypertension: Age of onset , Presenting symptoms, Investigation for secondary causes

· Medication history :nature of antihypertensive medication, past & present treatment, compliance in taking medication, other medication

· Physical examination : erect & supine BP , presence of postural hypotension, 4 hourly Bp observation in the ward.

Assessment of target organ damage

· Cardiovascular system

· Renal system

· Central nervous system

· Other concomitant disease

Acceptability for surgery

· More concern on the extent of target organ damage instead of diagnosis of hypertension

· Deffered elective surgery if Bp persistently high, diastolic BP > 110 or systolic BP > 180

· If presence of target organ damage & elevated BP, need great attention

· Delay surgery for optimization of antihypertensive therapy

· If need to delay , consider the benefit of delaying the operation for optimization of BP outweigh the risk of delaying the surgery.

· Consider measures for rapid reduction of BP for emergency surgery with anticipated risk of rapid BP reductions.

Anesthetic management

Pre-medication

· Reduced anxiety with adequate sedation & anxiolysis to prevent anxiety induced tachycardia & hypertension

· Drugs: midazolam.

· Continue antihypertensive on the morning of surgery

· Serve with sip of clear water

· Some clinician: withhold ACE inhibitors & angiotensin 11 receptors because it may cause intraoperative hypotension

· Central a-adrenergic agonist : good for premed of hypertensive ptn ex Clonidine ( 0.2 mg )

-augment sedation

-decreased intraoperative hyperetension

-but: a/w profound intraoperative hypotension & bradycardia

Objectives intraoperatively

· maintain stable BP appropriate f that ptn

· borderline hypertension rx as normotensive ptn

· long standing / poorly regulated hptn ~~~> altered autoregulation of cerebral blood flow>>> therefore need higher than normal BP ~~~> matain adequate cerebral blood flow

· avoid excessive blood pressure elevation esp: ptn w coronary artery & cardiac hypertrophy

Objective intraoperatively

· hypertension plus tachycardia ~~~> precipatete myocardial ischemia/ ventricular dysfunction

· aim for art BP within 10-20 % pre-operative

· if pre-operative BP is > 180/120 , >>>> maintain BP on high -normal range ( 150-140/90-80)

·  

Monitoring

· most ptn >>> no need invasive special monitor

· invasive BP monitoring indicated :

· wide swing of BP

· major surgery with marked changes in preload & afterload

· ECG monitoring: detect ishemia

Monitoring

· Urinary catheter for urine output monitoring

· f surgery > 2 hrs

· f renal impairement ptn

· invasive hemodynamic monitoring ex swanz-gans, CVP monitor ~~~> apparent & good monitoring of left -end diastolic volume & cardiac output

Problem during induction

· period of hemodynamic instability

· usally ptn display marked hypotensive rxn to induction agent then exaggerated hypertensive response to intubation

· hypotensive rxbn d/t anethstic agent w vasodilator effect , cardiac depressant effect & antihypertensive effect

Induction

· hyepertensive ptn is volume depleted ptn

· symphatholytic agent ~~~> attenuate normal protective circulatory reflex, reduce symphathetic tone, enhance vagal activity

·  up >>> 25% ptn : severe hypertension post-intubation

· so need short time for laryngoscope

· performed laryngoscope when fully deep

Technique to obtund the hypertensvie response

· deepening of anesthesia w volatile f 5-10 mins

· give bolus of opiod :

· fentanyl 2.5-5 ug/kg

· alfentanil  15-25 ug/kg

· sulphentanil 0.25-0.5 ug/kg

· remifentanil 0.5-1 ug/kg

Technique to obtund the hypertensvie response

· give bolus lidocaine 1.5 mg/kg IV or intratracheally

· give beta-blockade :

· esmolol  0.3 -1.5 mg/kg

· propranolol 1-3 mg

· labetalol 5- 20 mg

· give IV nitroprusside or nitroglycerin 0.5 -1.0 ug/kg

· use topical airway anesthesia

Choices of anesthetic agent

· induction agent

· no clinical evidence supporting superiority of difference drugs

· choice: barbiturates, benzodiazepines, propofol, etomidate

· contraindicated : ketamine f elective procedure

Ketamine for induction

· contraindicated in elective ptn

· precipiateted severe hypertension

· use concxomitantly w midazolam/ propofol

Maintenance agent

· safely use with volatile agent ( alone / with nitrous)

· a balance technique ( opid + nitrous + muscle relaxant)

· total intravenous anethseisa

· addition of volatile/ IV vasodilatpor agent ~~~> good intraoperative BP control

Ventilation

· Maintain normocarbia andd

Advantages

· allow titration of their effect according to blood pressure

· sulfentanil ~~~> greatest autonomic suppression & control over blood pressure

Muscle relaxant

· any of muscle relaxant except large bolus of pancuronium

· pancuronium ~~~> induced vagal blokade & increased cathecholamine neural release ~~~> exacerbate hypertension

· if pancuronium given slowly ~~~~> less likely

Benefit of pancuronium

· Can offsetting the  excessive vagal tone induced by opiod & induction agnets

Vasopressors

· Hyepertensive : has exaggerated responses to endogenous cathecholamines d/t intubation or surgical stimulation or exogenously administered symphathetic agonist.

 If vasopressor needed, uses:

· Phenyephrine : 25-50 ug

· Ephedrine : 5-10 mg

· Cautious : if patient on symphatolytic pre-operatively ~~~> decresed resposnsed to vasopressor

Intraoperative hypertension

· Treated with incrased anethetic depth

· Use pareteral IV antihypertensive

· Identify reversibole causes & treat accordingly : ex: inadequate anesthetic depth , hypoxia, hypercapnia

· Exclude the causes first

Choice of IV anti-hypertensive

· Depend on : 
· Severity

· Acuteness

· Causes of hypertension,

· Baseline ventricular function

· Heart rate

· Presence of bronchospastic pulmonary disease

Beta-blokade

· Ie for ptn with good ventricular fx & elevated heart rate

· Contraindicated in brochspasm ptn

·  

Nicardipine

· Good for hypertensive ptn

· Ptn with bronchospasm

·  

Sublingual nifidepine

· A/w myocardial ischemia

Nitroprusside

· Most rapid

· Effective agent for moderate to severe hypertension

  

Nitroglycerin

· less effective

· useful f treating/preneting myocardial ischemia

Fenoldopam

· useful agent

· may improve/ maintain renal function

·  

Hydralazine

· sustained blood pressure contol

· delayed onset

· a/w reflex tachycardia

Labetalol

· combined a- & b adrenergic blokade

·  

Post-operative management

· post-operative hypertension: common

· anticipated inptn with poorly controlled hypertension

· close BP monitoring in recovery & early post-operative period

Complication of post-operateive hypertension

· myocardial ishemia

· congestive heart failure

· marked sustained elavation of BP~~~> wound hematomas & disruption of sutures

Hypertension in recovery period

· Multifactorial may be cause by:

· Respiratory abnormality

· Pain

· Volume overlaod

· Bladder distension

Management of hypertension in recovery period

· Treat the cause

· Administer IV anti-hypertensive ex : nicardipine

· If ptn resume oral intake~~~> start on oral medication