The post-operative patient

Arun Radhakrishnan

Applied physiology

Needs good understanding of whole body physiology as well

Not limited to one organ system!!! What would be the major issues in such a

patient?

Major post-op issues

Pain

Delirium

Anaesthesia-related

Surgery-specific

Respiratory compromise

Cardiovascular issues

Fluid-electrolyte-metabolic

Ileus

Infection

State of inflammation/SIRS

Stress response to surgery

Systemic response to surgery

Secretion of pituitary hormones plus activation of the sympathetic nervous system

Catabolism

Breakdown of skeletal muscle and fat

Insulin resistance and hyperglycaemia

Retention of salt and water

Systemic response to surgery

Systemic response to surgery

SIRS (Systemic inflammatory response syndrome) (at least 2 of the following criteria):

Temperature > 38 0C or < 36 0C

HR > 90

RR > 20

WBC count < 4 or > 10 or > 10% immature neutrophils

SIRS may lead to organ injury or failure, often multiple

Haemodynamic response

Hypovolemia due to blood loss or fluid loss

Post-op fluid and water retention, independent of intraoperative loss

ADH

Aldosterone

Immune response: Increased Cytokine release, complement activation- may lead to SIRS

Impaired (exhausted) response may predispose to infections

Effects of anaesthetics

OpioidsRespiratory depression

Suppress hypothalamic and pituitary hormone release esp. ACTH

Suppress the hyperglycaemic response

Non-osmotic release of ADH (SIADH)

Decrease bowel motility - ileus

BenzodiazepinesInhibit cortisol production

EtomidateSuppresses cortisol and aldosterone production – increases mortality

Clonidine - Inhibits stress response

Regional anaesthesia

Epidural or paravertebral blocksBlocks both pain and efferent autonomic output in pelvic

and LL surgeries, less effective for thoracic and upper abdominal surgeries

Can cause urinary retention (esp. intrathecal morphine)

Case

Mr X, 39/M post-op in Critical care (Previously well)

Emergency laparotomy for peritonitis Previous urgent laparotomy 1 week ago for

diverticular perforation Pre-op: GCS 14, HR 112, BP 90/58 mm Hg,

SpO2 on room air 89%, Urine output 15-25 mL/hr

Post-operative physiology

Impact of derangements depend on: Type of surgery – Elective Vs Emergency General health pre-op Co-morbidities Organ dysfunction(s) present (acute and chronic) Duration of surgery Anaesthetic management Post-anaesthetic care

Surgery-specific

Operative site- e.g.; H&N or airway surgery, abdominal surgery etc.

Bleeding or discharge from drains or wound(s) 'Health' of the stoma

General Considerations

Pain management PONV Temperature management Fluid management- volume status determination Organ system support- Respiratory and Cardiovascular, Renal Nutritional considerations Preventing complications of immobility Housekeeping

Pre-existing conditions

May require specific management eg; CCF, COPD, CKD

May need careful balancing of goals eg: Fluid management in the patient with CCF

Organ systems

Neurologic Level of consciousness

Cardiovascular CR (if not hypothermic)

Respiratory Rate, FiO2, Pattern, SpO2

Renal Urine output- accept a total output of > 500 mL

over 24 hrs

Organ Systems

Metabolic pH, pCO2, HCO3, Lactate, BSL

Think about the cause for derangements!

Pain

What is the problem with pain? Complex entity made up of sensory, affective,

motivational and cognitive dimensions Unpleasant for the patient Sympathetic responses- HR, BP, increased O2

demand Site-specific: Respiratory compromise Inability to mobilise/physio

Pain

Neuroendocrine effects- the SIADH Non-osmotic signal to retain fluid Manifest as post-op Hyponatremia and/or oliguria

despite clinically normal cardiac output and volume status

Pain management

Prevention is better than cure Multimodal analgesia

IV, Regional and Local techniques Side-effect profile very important, eg;

respiratory depression with opioids

Temperature

Why is 'normal' temperature important? Causes of hypothermia in post-op patients? Problems with hypothermia:

Shivering Metabolic acidosis Cardiovascular issues- arrhythmias, increased O2

demand, cardiovascular depression etc. ↓ drug metabolism, ↓ platelet function, drowsiness

Cardiovascular issues

• Low BP• HTN• Arrhythmias• Cardiac ischaemia

• More common with pre-existing cardiac or respiratory dysfunction

Cardiovascular issues

Cardiovascular 'signs' of low volume status How reliable is BP as an index of volume in the

post-op period? What is the most important cause of HTN in this

scenario? Pain Anxiety, drug withdrawal, urinary retention

What are the causes of Hypotension?

Causes of hypotension

Intravascular volume depletion Ongoing losses eg; haemorrhage Sepsis Myocardial dysfunction (Peri-operative MI) SIRS response- capillary-leak Regional blocks Usual causes of shock!!!

Management of Hypotension

Determine the Volume status We have been struggling for over 50 yrs to do so!!!!

History and physical examination essential Previous or ongoing fluid losses and intake (I/O charts) 3rd space losses? Sluggish CR Postural hypotension Persistently poor urine output Signs of heart failure

Patients for elective surgery are unlikely to be ‘fluid-deficient’ peri-operatively

Options to manage Hypotension

What are we trying to achieve???? 'Normal' perfusion- a cardiac output that is

'sufficient' to meet body needs without incurring the risk of complications

CO = Stroke volume x HR Stroke volume depends on Preload, Afterload

and Contractility HR and rhythm important

Options to manage Hypotension

How important is it to 'normalize' the patient's vitals?

Is the 'low' BP compromising the patient, or is it likely to compromise him/her?

Options- optimise preload (CVP or JVP gives a rough idea- please do not chase numbers)

Avoid medications that could compromise contractility eg; anti-hypertensives, anti-CCF

Role of the 'Fluid Bolus'

Estimation of the volume status extremely difficult, even in intensive care

Estimate pre- and intra-op fluid losses and replacement

Duration of pre-op pathology Intake pre-op Anaesthetic charts for intra-op Mx Normal fluid requirements 30 mL/kg/day

Role of the 'Fluid Bolus'

Patient warm, CR < 2 s, no organ system derangement obvious

SBP 96, MAP 65 U/O 20 mL in last

hour Does this patient

need a fluid bolus?

Fluid bolus

Ensure fluid bolus is targeted at physiologic need, rather than to (ad)dress numbers!!!!

Low volumes of fluid (250 mL or 500 mL)- constantly re-assess for response before going on to next bolus

Have a ‘stop’ limit in your mind!

Keep the clinical situation in mind-are we actually dealing with a low CO?

Is tissue perfusion adequate?

Is the patient bleeding?

Complications of fluid overload

Pulmonary congestion

APO

Pleural effusions

Hypoxia

Worsen heart failure

Worsen bowel perfusion and impair anastomotic healing

Ascites

Worsen renal perfusion

Hyperchloremic metabolic acidosis

Dilutional throbocytopenia

Hypotension-vasoactive agents

Leaky capillaries due to SIRSMyocardial dysfunctionProblems with excessive fluid ‘resusc’Choice of agent depends on principal reason for

hypotension: Cardiac dysfunction (Inotropic agents) Vs. Vasoplegia (Vasopressors)

Arrhythmias

Common after thoracic surgeryElectrolyte disorders (K, Mg, Phosphate)

predispose

Hypoxia

SpO2 < 90% on room air (Aim > 90-92%) What are the important causes of hypoxia? Is PaO2 more important than the SpO2?

• Pain causing respiratory compromise-hypoventilation, impaired sputum clearance

• Fluid overload• Collapse (Atelectasis)• Consolidation• Aspiration• PE• Surgery-specific – Pneumothorax post-thoracic surgery or

post-CVC insertion

Management of Hypoxia

O2 Supplementation Improve V/Q mismatch SOOB, Physiotherapy Diuresis Positioning Specific cause –e.g. Antibiotics

Mx of Hypoxia

Mechanical ventilation or Non-invasive Ventilation if: ↑ WOB SpO2 < 90% on high FiO2 (> 0.5) Progressive or severe respiratory acidosis, or

inability to compensate for metabolic acidosis Severe Pain causing impairment of respiration or of

cough

Volume status and renal function

Post-op tendency to fluid retention due to SIADH (non-osmotic release of ADH)

Sympathetic response contributory

Hyponatremia very common

'Leaky' capillaries- loss of intravascular fluid into interstitial spaces

Urine output decreases not a reliable sign of hypovolemia

Do not administer fluid boluses to improve urine output if CO clinically adequate!!!

Oliguria

Pre-existing cardiovasc or renal issuesCauses:

Intravascular volume depletion

Hypotension

Low Cardiac output

Nephrotoxic agents-IV contrast

Direct injury to ureters

Obstruction at level of bladder (? blocked IDC)

Heard of the abdominal compartment syndrome???

Renal Function

Anuria always a cause for concernMost common causes for kidney compromise are- hypotension

and hypoxia

Intravascular volume depletion

Excessive use of chloride-rich IV fluids (NS, Gelofusine)

Suspect surgical issues- eg: have the ureters been ligated (Pelvic surgery)- very rare cause

Mild rhabdomyolysis due to prolonged positioning intra-op

Generally, re-establishing adequate perfusion and avoiding nephrotoxic agents resolves the issue.

Dialysis may be needed for usual indications

Don't forget the gut!!!

Bowel dysmotility- paralytic ileusType of surgeryOpioids

Nutritional issues

Refeeding syndrome

Severe hypophosphatemia (respiratory- and cardiac failure, shock, rhabdomyolysis, seizures and delirium) due to insulin release after period of fasting. Associated with hypokalemia and hypomagnesemia.

Malnourished patients, alcoholics, ongoing electrolyte losses are predisposed

Monitoring is critical

Glucose control

Insulin resistance and catabolic state with surge of counter-regulatory hormones

Very important to maintain euglycaemia (BSL 7-10) esp after major surgery

Adverse effects of Hyperglycaemia: Wound infection, osmotic diuresis, dyselectrolytemias

Anaemia and blood loss

Causes: • Surgical bleed

• 'Dilutional'

• Pre-existing anaemia

Contribution of coagulopathyWhy are we concerned?????

'Management' of anaemia

Correct the cause- surgical bleed to be corrected (surgical Vs. radiologic Vs. Endoscopic)

Correct coagulopathy- what are the post-op factors that can worsen coagulopathy???

Considerations: Site, amount, and haemodynamic significance, and patient's tolerance

We are trying to improve/maintain oxygen delivery

RBC transfusions usually not required

Role of prophylactic PPI to prevent stress ulceration

Thromboembolism

Surgery and anaesthesia foster a hypercoaguable state

High risk of DVT post-opMethods to protect and prevent

Sometimes problematic if concurrent bleeding issues

Infection and sepsis

Patient background- immunocompromised?

Nature of surgery

Post-op Fever

Does fever always mean an infection???What are the non-infectious causes of fever?

DVT/PE

Indwelling devices e.g. CVC

Medications (drug fever) or Drug withdrawal

Stroke or intracranial bleed

Seizures

SIRS

Transfusion reactions

Delirium

• Very common• Causes:

• Predisposing factors (age, dementia, sensory deprivation)• Pain • Direct neurologic insult• Organ dysfunction• Sepsis (think surgical sepsis)• Drugs eg; opiates• Urinary retention (esp. with neuraxial blocks)• Never forget hypoxia, hypercarbia or low BSLs

Delirium treatment

Prevention always bestEarly recognitionRe-orientation and reassuranceFamily presenceNocte antipsychoticsChemical – haloperidol, olanzapine etc.

Metabolic issues

• Metabolic acidosis very common• Hypothermia and peripheral vasoconstriction• Hyperchloremic acidosis

• Accentuated by lack of ability to self-correct in an anaesthetised patient

• Concern if reflects persistent low cardiac output state (Raised lactate)

Site-specific problems

Thoracic surgeryPain with respiratory

impairmentPneumothoraxHaemorrhage

Abdominal surgeryPain with respiratory

impairmentPost-op ileusAbdominal compartment

syndromeBleeding

Patient-specific problems

Cardiac diseaseCompromised cardiac

outputFluid and electrolyte

derangementsSepsis Peri-op MI

Respiratory diseaseMay be worsened by

surgeryHypoxia may worsen

outcomes

Warning signs

What are the danger signs of organ dysfunction???

Trends are more important than single 'snapshot' values

Exceptions are- airway obstruction, ↓LOC, Shock, Severe hypoxia or cyanosis, respiratory distress or anuria

Summary

State of inflammationPain and organ dysfunctionNeeds comprehensive management