Post-operative Management of HemodynamicallyUnstable Patient
Prof. Minnu M. Panditrao
Professor, Department of Anaesthesiology&Intensive Care
Adesh Institute of Medical Sciences and Research (AIMSR)
Bathinda, Punjab, India


Hemodynamic instability in post-operative period is a common phenomenon. It may be a continuation of intraoperative hemodynamic instability or may be a new occurrence in the postoperative period, in which case majority times it is transient and benign and without any serious consequences in healthy ASA I and II patients. But if it is allowed to persist for longer periods, can have serious deleterious effects on long term prognosis especially in old patients with comorbidities like CAD, hypertension, diabetes, renal diseases etc. Therefore it becomes imperative for the anaesthesiologist in charge to identify and treat this condition as soon as possible.
The shifting of the patient from operating table to the recovery room bed is the most crucial time and should be handled with utmost care and sensitivity, otherwise it defeats the whole purpose of a great surgical procedure and an excellent anaesthesia and maintaining of stable hemodynamics in the intra operative period. Equally important is the care of the patient in the post-operative period especially the early postoperative period (first 6-12 hours depending upon the type of surgical procedure and preoperative condition of the patient).
If a patient was hemodynamically unstable intra-operatively, all the intra-operative monitoring/treatment should be continued in post-operative period, during the shifting (whatever is possible) and also in the recovery bed in ICU, HDU or PACU till the patient becomesstable again. The Anaesthesiologist, Surgeon and Anaesthesia Assistant should accompany the patient during his/her shifting to these areas.
Hemodynamic instability in post-operative period can occur in the form of:
Hypertension/Hypotension
Tachycardia/Bradycardia
Cardiac dysrhythmias
Post-operative tachycardia and systemic hypertension are more predictive of adverse outcome than hypotension and bradycardia.

• Hypertension:  Usually develops within 30 minutes of end of surgery. It is seen in up to 35% of post-operative patients. The common causes are:
• Preexisting essential hypertension
• Post-operative pain
• Emergence excitement
• Hypoventilation (hypercarbia, hypoxemia)
• Residual effect of sympathomimetic/anticholinergic drugs, ketamine etc.
• Rebound hypertension after withdrawal of hypotensive agents i.e. an anesthetics, sedatives, antihypertensive infusions.
• Distension of viscera esp. urinary bladder

Other likely causes are:

• Hypervolemia
• Intracranial surgeries, raised ICP
• PONV, Shivering
•  Elderly age, h/o cigarette smoking, renal disease etc.
•  Substance withdrawal
• Hyperthyroidism, malignant hyperpyrexia etc.

Management: First and the foremost is to try to identify and treat the cause. Ensure adequate analgesia and ventilation/oxygenation. It is also important to determine the severity of hypertension taking into consideration the patient factorsi. e. age, pre-operative baseline Blood pressure, comorbidities etc. and then plan the pharmacological control of Blood pressure. Mild to moderate hypertension may be controlled with adequate analgesia and sedation. An injection of diuretic may be helpful if hypervolemia (low urine output intra-op) is suspected.
Post-operative hypertension is usually short lived so shorter acting medications should be used. Various drugs used for control of hypertension in postoperative period are:

• Labetalol: it’s a β1 adrenergic Antagonist with some α1 antagonist activity. 5 mg IV bolus is given, effect starts within 5 minutes and lasts for up to 1 hour.
• Esmolol: a β1 adrenergic Antagonist with rapid onset and short duration of action, a bolus of 500 µg/kg over 60 sec. is followed by infusion of 50—300µg/kg/min. Both Esmolol and Labetalol are contra indicated in asthmatics
• Hydralazine: adirectly acting peripheral vasodilator. Given as 5mg IV boluses, onset of action is within10-20 min., it can cause tachycardia.
• Nifedipine:sublingual 5-20 mg can be given.
• Glyceryltrinitrite: A direct acting arterial and venous dilator, given as IV infusion at a rate of 0.2-8 µg/kg/min. rapid onset and short acting. Can also be given as patchesof

5-10 mgs.

• Hypotension: common in post-operative period, usually benign and transient when it is due to residual effects of anesthetic/analgesic drugs.

Three types of hypotension are:

• Hypovolemic: (decreased preload)  due to:
• Inadequate intra operative blood/fluid replacement or ongoing losses i.e. into the drains or third space fluid shifts, bowel preparation/ G. I. losses.
• Sympathetic blockade—residual effect of spinal/epidural anaesthesia there is relative hypovolemia.

Tachycardia may not be there if patient is on B blockers or calcium channel blockers.
Management: Prompt detection and treatment of the cause is important to prevent ischemia of vital organs. Flat or head down position, oxygen supplementation, rapid boluses (250-500 mls.) of IV fluids(crystalloid/colloids) should be given. Assess the response, replace blood as soon as possible. If patient fails to respond to this, CVP monitoring/ pulmonary artery catheter monitoring may be necessary to assess the left ventricular function.
Patients with marked peripheral vasodilatation may remain hypotensive in spite of fluid replacement especially after high spinal/epidural block, here vasoconstrictors/inotropes in addition to IV fluids may be required.
Vasopressors used are:

• Ephedrine- Aα and β adrenergic receptor agonist, produces peripheral vasoconstriction, increased heart rate and increased myocardial contractility. Has a rapid onset of action. Dose: 3-6mg increments, titrated to get the desired effect.
• Phenyl ephedrine: Aα1 adrenergic agonist, given in IV bolus doses of 0.05-0.2 mg, titrated to get the desired effect.
• Mephentermine: A cardiac stimulant and vasoconstrictor, given in IV bolus doses of

3-6 mg, titrated to get the desired effect.

• Metaraminol:Aα1 adrenergic receptor agonist with some β agonist activity, rapid onset, 0.5 mg increments are given to getthe desired effect.

80% of patients with hypotension in recovery room respond to administration of IV fluids alone. Giving vasopressors alone without giving adequate IV fluids is dangerous as it may further compromise the perfusion of vital organs like liver and kidneys. Ongoing blood loss in Recovery room may require surgical intervention/use of clotting enhancing agents to control the bleeding.

• Cardiogenic: (intrinsic pump failure, decreased cardiac output) due to:
• Myocardial ischemia, myocardial infarction, CHF
• Cardiomyopathies, valvular heart disease, pericardial disease
• Cardiac dysrhythmias
• Drug induced (β blockers, calcium channel blockers )
• Electrolyte disturbances, acidosis, sepsis
• Cardiac tamponade, pulmonary embolus, tension pneumothorax

        Differential diagnosis will depend upon the patient’s pre-operative condition, surgical procedure, intra-operative and post-operative events. In the post-operative period, myocardial ischemia/infarction in a patient rarely presents with chest pain, the first sign may be hypotension or unexplained tachycardia or even bradycardia
To determine the exact cause, CVP, Surface and Trans esophageal Echocardiography or pulmonary artery catheter monitoring may be required. CXR, ABG, serum electrolytes, CPK-MB, Troponin-T will help in the diagnosis.
Management: In cases of myocardial ischemia/infarction early intervention with nitrates, opioids, β blockers and even anticoagulants may be lifesaving. In general treatment of the causative factors and supportive treatment along with optimizing the preload,inotropic and vasodilator therapy is necessary.

• Distributive: (decreased afterload) due to:
• Iatrogenic sympathectomy due to neuraxial blockade- i.e. a high block (up to T1-4) will decrease the SVR and block the cardio-accelerator fibers. If not treated promptly, severe bradycardia, hypotension and even cardiac arrest may occur even in young healthy adult patients. Prompt administration of vasopressors, atropine/glycopyrrolate along with rapid IV fluids and supportive treatment may be lifesaving.
• Allergic reactions: anaphylactic/anaphylactoid reactions can cause hypotension due to decreased afterload. Increased serum tryptase levels confirm the diagnosis. The blood sample should be taken between 30-120 minutes after the onset of allergic reaction. Drug of choice is Epinephrine. Steroids and supportive treatment as required should be given.
• Sepsis: if sepsis suspected, blood culture should be sent before starting the empirical antibiotic therapy. Biliary tract procedures and urinary tract manipulations are the common causes of sudden onset of hypotension secondary to sepsis. Fluid resuscitation is important. Noradrenaline and Phenylephrine are the 1st line of drugs. Addition of Vasopressin in low dosesof 0.01-0.05 units /minute improves mean arterial pressure and spares renal function in severe septic shock.
• Critically ill patients usually rely on exaggerated sympathetic tone to maintain systemic blood pressure and heart rate. In these patients even low doses of inhaled anesthetic agents/opioids/sedatives may decrease the sympathetic tone to produce marked hypotension. So very low titrated doses of these agents, with caution should be given in these patients.

• Tachycardia:  Pulse rate >100 BPM. Common causes are:
• Pain
• Hypovolemia
• Anemia
• Pyrexia
• Hypoxia/Hypercarbia
• Sympathomimetic drugs, ketamine
• Anticholinergic drugs
• Hypothermia/shivering
• Presence of endotracheal/other tubes/catheters

Other less common causes may be

• Cardiogenic/septic shock
• Pulmonary embolism
• Substance withdrawal
• Thyroid storm/Malignant hyperpyrexia

 Management: Treat the cause. If associated with myocardial ischemia, giveβ blockers.

• Bradycardia: Pulse rate < 60 BPM. Common causes are:
• Often iatrogenic due to use of drugs like β blockers, opioids, anticholinesterases, dexmedetomidine etc.
• Bowel distension, increased ICP/IOP
• High spinal/epidural block

Management:  Depends upon the general condition of the patient. Moderate degree of bradycardia (PR of 45-50) may be allowed if the blood pressure is in the normal/high range. Symptomatic bradycardia if associated with hypotension should be treated with anticholinergic agents. Drugs used are:

• Atropine IV 0.3mg boluses may be given, dose is titrated. Upto 3 mg may be given.
• Glycopyrrolate – 0.1 -0.4 mg IV may be given to get the desired effect.
• Inotropes like dopamine/dobutamine

d)   Aminophylline IV may be given in refractoryβ blocked patients

• Cardiac dysrhythmias: May be atrial or ventricular. Various causes are:
• Hypoxemia/Hypercarbia
• Pain/agitation
• Hypovolemia/anemia
• Volume shifts/fluid overload
• Endogenous/exogenous catechol amines
• Anticholinesterases/anticholinergics
• Hypothermia/hyperthermia
• Myocardial ischemia/infarction
• Electrolyte abnormalities/Acidosis
• Hypertension
• Digitalis intoxication
• Substance withdrawal
• Pre-operative cardiac dysrhythmias

 

• Atrial dysrhythmias: The incidence of atrial dysrhythmias may be up to 10% after non-cardiac major surgeries and incidence is even higher after cardiac and thoracic surgeries which is considered to be due to atrial irritation. The new onset atrial arrhythmias are not benign because these are often associated with longer hospital stay and increased mortality. Supraventricular tachycardia and Atrial fibrillation are the common atrial dysrhythmias

Management: control of ventricular rate is the immediate aim. After excluding/ treating the various causative factors, prompt electrical cardioversion or Adenosine 6 mg IV push plus another 12mg IV push if required orDiltiazam15-20mg IV over 2 minutes followed by 5-15mg/hour in infusion may be given for SVTs. For atrial fibrillation β blocker Esmolol is preferable due to its rapid onset and short duration of action. Amiodrone may be givenif β- blockers are contraindicated.

• Ventricular dysrhythmias: Pre-mature ventricular contractions (PVCS) and bigemini are common and areusually dueto increased sympathetic tone esp. in hypercapnic/hypoxic patients, whereas true ventricular tachycardia may indicate cardiac pathology.

Management: Try to find and treat the cause, occasional PVCs without any fall in blood pressure may be just observed, and should be treated only if there are significant numbers/runs of ectopics producing hypotension. IVLidocaine 50-100mg as a bolus followed by infusion 1-4mg/minute can be given or Amiodrone150mg over 10minutes followed by 1mg/min for 6 hours and then 0.5mg/min for 18 hours can be given.
Ventricular tachycardia is a rare post-operative complication which can progress to ventricular fibrillation, so must be treated immediatelywith IV Lidocaine if the blood pressure is stable. If patient is hypotensive, DC cardioversion should be given.

In conclusion, Hemodynamic instability is one of the most frequently encountered complication in the early post-operative period. If diagnosed early and managed promptly and decisively, significant amount of morbidity and mortality can be prevented.

 

References:
Miller’s Anesthesia, Seventh Edition 2010
Lee’s Synopsis of Anaesthesia 13th Edition 2006
Basics of Anesthesia byRobert K. Stoelting, Ronald D. Miller. 5th Edition 2007
Fundamentals of Anaesthesia by Tim Smith, Colin Pinnock, Ted Lin. 3rd Edition 2009