Preoperative and Postoperative Care

Learning Objectives

By the end of this page, you should be able to:

• Perform a structured preoperative assessment, including ASA classification and cardiac/pulmonary risk stratification.
• Apply current fasting (NPO) guidelines for solids, breast milk, and clear liquids.
• List the causes of early, intermediate, and late postoperative fever using the "5 W's" mnemonic.
• Recognize and manage the common postoperative complications: atelectasis, wound infection, DVT/PE, and ileus.
• Explain the rationale behind enhanced recovery after surgery (ERAS) protocols.
• Distinguish postoperative complications by their typical time of onset.

Quick Answer

Preoperative care is the systematic process of assessing and optimizing a patient before surgery — reviewing history, examining organ systems, ordering targeted (not blanket) investigations, classifying anesthetic risk (ASA grade), obtaining informed consent, and following fasting rules to prevent aspiration. Postoperative care is the structured surveillance that follows — monitoring vitals, controlling pain, preventing wound and lung complications, mobilizing the patient early, and managing nutrition until safe discharge. Together they matter because most surgical morbidity and mortality comes not from the operation itself but from preventable perioperative complications: aspiration, atelectasis, infection, and venous thromboembolism.

Preoperative Risk Assessment

A good preoperative assessment isn't a checklist exercise — it's where you catch the problem that would otherwise surface on the operating table. The core question for every patient is: can this person tolerate the physiological stress of anesthesia and surgery, and what can I do beforehand to reduce that stress?

History and Examination

Focus on:

1. Cardiac status — angina, dyspnea, prior MI, exercise tolerance (can they climb two flights of stairs?).
2. Pulmonary status — smoking history, COPD, asthma, recent respiratory infection.
3. Bleeding tendency — anticoagulants, antiplatelets, liver disease, easy bruising.
4. Airway — Mallampati score, neck mobility, previous difficult intubation.
5. Drug history — especially anticoagulants, corticosteroids (need stress-dose coverage), and diabetic medications.

ASA Physical Status Classification

Anesthesiologists grade every patient using the ASA scale, which correlates directly with perioperative risk:

• ASA I — normal healthy patient
• ASA II — mild systemic disease (e.g., controlled hypertension)
• ASA III — severe systemic disease that limits activity (e.g., poorly controlled diabetes)
• ASA IV — severe disease that is a constant threat to life (e.g., unstable angina)
• ASA V — moribund, not expected to survive without surgery
• ASA VI — declared brain-dead, organ donor

A higher ASA class doesn't cancel surgery — it tells you how aggressively to optimize and monitor.

Investigations Should Be Targeted, Not Routine

A healthy 25-year-old undergoing an inguinal hernia repair does not need a chest X-ray and coagulation panel "just because it's surgery." Order tests based on the history, the physical exam, and the planned procedure — this is now standard teaching and reduces cost, false positives, and unnecessary delays.

Fasting (NPO) Guidelines

Fasting exists for one reason: to empty the stomach and reduce the risk of pulmonary aspiration during induction of anesthesia, when protective airway reflexes are lost. Standard ASA fasting guidelines:

Intake type	Minimum fasting time before elective surgery
Clear liquids (water, black coffee, pulp-free juice)	2 hours
Breast milk	4 hours
Infant formula / non-human milk	6 hours
Light meal (toast, clear liquids)	6 hours
Heavy/fatty meal	8 hours

Encouraging clear liquids up to 2 hours before surgery (rather than the old "nil by mouth from midnight" rule) is now standard because it improves patient comfort without increasing aspiration risk.

Optimizing Physiological Status

Where possible, correct these before the patient reaches the operating table:

• Blood pressure control
• Glycemic control (tight perioperative control reduces wound infection)
• Fluid and electrolyte correction
• Smoking cessation (even 4–8 weeks before surgery reduces pulmonary complications)
• Anemia correction

Informed Consent and Site Marking

Consent must cover the nature of the procedure, its risks and benefits, alternatives (including no treatment), and expected recovery — documented in language the patient actually understands. Surgical site marking (initialed by the surgeon before the patient enters the OR) exists specifically to prevent wrong-site surgery, one of surgery's classic "never events."

Postoperative Complications and Monitoring

The Immediate Recovery Period

In the recovery room, the priorities are airway, breathing, circulation, pain, and bleeding — in that order. Most life-threatening problems in the first hour (airway obstruction, hemorrhage, laryngospasm) show up here.

Postoperative Fever — The "5 W's"

One of the most commonly tested concepts in surgery: a patient develops fever a few days after an operation. The "5 W's" gives you a differential organized by time of onset, which is the fastest way to narrow the cause.

This timeline is a teaching tool, not a rigid rule — atelectasis can present on day 1, wound infections can appear earlier with aggressive organisms, and PE can happen at any point. But for exam purposes and initial clinical reasoning, "day of fever tells you where to look first" is exactly the right instinct.

Atelectasis

The single most common cause of fever in the first 24–48 hours. Shallow breathing due to pain and sedation causes small airway collapse. Prevention is more important than treatment: incentive spirometry, early mobilization, and adequate pain control (a patient in pain won't take deep breaths).

Wound Infection

Typically presents 5–7 days postoperatively with erythema, warmth, discharge, and fever. Risk factors include diabetes, obesity, contaminated procedures, and poor tissue perfusion. Management is wound opening, drainage, and antibiotics if cellulitis or systemic signs are present.

Venous Thromboembolism (DVT/PE)

The leading preventable cause of postoperative death in many surgical series. Risk is highest in immobile, orthopedic, and cancer surgery patients. Prophylaxis — mechanical (compression stockings, sequential compression devices) plus pharmacologic (low-molecular-weight heparin) when bleeding risk allows — is far more effective than treating an established clot.

Postoperative Ileus

Transient bowel hypomotility after abdominal surgery, presenting as distension, absent bowel sounds, and delayed flatus/stool. Managed conservatively (NPO or clear liquids, mobilization, minimizing opioids) — it's expected to resolve within a few days; if it persists beyond 3–5 days, think about a mechanical cause instead.

Pain, Nutrition, and Mobilization

Multimodal analgesia (combining opioids, NSAIDs, and regional techniques) controls pain while limiting opioid-related ileus and respiratory depression. Nutrition typically progresses from clear liquids to a regular diet as bowel function returns; early enteral feeding is preferred over parenteral nutrition whenever the gut works. Early ambulation — ideally within 24 hours — is one of the single most effective interventions against both atelectasis and DVT.

Enhanced Recovery After Surgery (ERAS)

ERAS protocols bundle these evidence-based practices — minimal fasting, multimodal non-opioid analgesia, early mobilization, and early oral intake — into a single perioperative pathway. Hospitals using ERAS protocols consistently show shorter length of stay and fewer complications compared with traditional care, which is why ERAS has become the standard of care for many elective procedures (especially colorectal surgery).

Key Terms

Term	Definition
ASA Physical Status Classification	A 6-point scale (I–VI) used by anesthesiologists to grade a patient's baseline health and predict perioperative risk.
NPO (nil per os)	"Nothing by mouth" — the fasting status required before anesthesia to reduce aspiration risk.
Atelectasis	Collapse of alveoli/small airways, usually from shallow breathing; the most common cause of early postoperative fever.
Surgical site infection (SSI)	Infection at or near the incision, typically presenting 5–7 days postoperatively.
Venous thromboembolism (VTE)	Umbrella term for DVT and PE; the major preventable cause of postoperative death.
Postoperative ileus	Temporary loss of coordinated bowel motility after abdominal surgery.
Informed consent	Patient's voluntary agreement to a procedure after understanding its nature, risks, benefits, and alternatives.
ERAS (Enhanced Recovery After Surgery)	A bundled, evidence-based perioperative care pathway that reduces complications and hospital stay.
Multimodal analgesia	Combining different classes of analgesics (opioid, NSAID, regional) to improve pain control while reducing opioid side effects.
Normothermia	Maintaining a core body temperature near 37°C intraoperatively to reduce bleeding and infection risk.

Common Mistakes

Misconception 1: "Every preoperative patient needs a full panel of blood tests, ECG, and chest X-ray." Why it's wrong: Blanket testing increases cost, delays surgery, and generates false positives that trigger unnecessary further workup without improving outcomes. Correct understanding: Investigations should be guided by the patient's history, comorbidities, and the invasiveness of the planned procedure — a healthy young patient for minor surgery needs little to no testing.

Misconception 2: "Postoperative fever on day 1 is almost always an infection, so start antibiotics immediately." Why it's wrong: Day 1–2 fever is overwhelmingly due to atelectasis (a mechanical/inflammatory process), not infection — reflexively starting antibiotics treats the wrong problem and promotes resistance. Correct understanding: Use the timing of fever to guide the differential ("Wind" on day 1 points to atelectasis); reserve antibiotics for signs pointing to an actual infectious source.

Misconception 3: "Patients must stay strictly NPO from midnight before any surgery." Why it's wrong: This traditional rule causes unnecessary dehydration, discomfort, and even hypoglycemia without reducing aspiration risk any further than modern guidelines. Correct understanding: Current ASA guidelines allow clear liquids up to 2 hours before elective surgery; only solids and non-clear liquids require the longer 6–8 hour fast.

Comparison and Connections

Complication	Typical Onset	Key Cause	Best Prevention
Atelectasis	Day 1–2	Shallow breathing, retained secretions	Incentive spirometry, early mobilization, pain control
UTI	Day 3–5	Indwelling catheter	Early catheter removal
Wound infection	Day 5–7	Bacterial contamination, poor perfusion	Sterile technique, glycemic control, prophylactic antibiotics
DVT/PE	Day 5–10+	Immobility, venous stasis, hypercoagulability	Mechanical + pharmacologic prophylaxis, early ambulation
Drug fever	Any time, often later	Hypersensitivity to a medication	Review drug chart, discontinue offending agent
Postoperative ileus	Day 1–3 (expected)	Bowel handling, opioids	Minimize opioids, early feeding, mobilization

Practice Questions

Recall

1. What are the ASA fasting requirements for clear liquids and for a heavy meal before elective surgery? Answer guidance: Clear liquids — 2 hours; heavy/fatty meal — 8 hours.

2. Name the "5 W's" of postoperative fever in order of typical onset. Answer guidance: Wind (atelectasis, day 1) → Water (UTI, day 3) → Wound (SSI, day 5) → Walking (DVT/PE, day 7) → Wonder drugs (drug fever, day 7+).

Understanding

3. Why does incentive spirometry reduce the risk of postoperative fever? Answer guidance: It encourages deep breathing, which re-expands collapsed alveoli and clears secretions, directly preventing atelectasis — the leading cause of early postoperative fever.

4. Explain why ERAS protocols emphasize early oral feeding and minimal opioid use together, rather than each in isolation. Answer guidance: Opioids slow gut motility and contribute to ileus; minimizing them allows the bowel to recover faster, which then makes early oral feeding tolerable — the two interventions reinforce each other.

Application

5. A 68-year-old diabetic patient develops fever, incisional erythema, and purulent discharge on postoperative day 6. What is the most likely diagnosis and immediate management? Answer guidance: Surgical site infection. Open and drain the wound, send discharge for culture, start antibiotics if there is cellulitis or systemic toxicity, and optimize glycemic control.

6. A patient scheduled for elective knee replacement had a light breakfast 5 hours ago. Can surgery proceed as planned? Answer guidance: No — a light meal requires 6 hours of fasting; the case should be delayed or clear liquids only should have been permitted after that point to keep aspiration risk low.

Analysis

7. Compare the timing and pathophysiology of postoperative ileus with mechanical bowel obstruction. How would you distinguish a "normal" ileus from one that should raise concern? Answer guidance: Ileus is diffuse bowel hypomotility (no true blockage) expected in the first 1–3 days after abdominal surgery, resolving as motility returns. If distension, absent flatus, or vomiting persist beyond 3–5 days, or if there are high-pitched bowel sounds and colicky pain, mechanical obstruction (e.g., from adhesions) should be suspected and imaged.

8. A surgical resident argues that because DVT prophylaxis has bleeding risks, it should only be given after a patient shows signs of a clot. Evaluate this reasoning. Answer guidance: This reasoning is flawed — VTE is a leading cause of preventable postoperative death, and prophylaxis (mechanical plus pharmacologic when appropriate) is proven to prevent clot formation, not just treat it. Waiting for clinical signs means treating after damage (or a fatal PE) has already occurred; risk-stratified prophylaxis, not reactive treatment, is the standard of care.

FAQ

Why can't patients just eat and drink normally right up until surgery? Because general anesthesia and heavy sedation suppress the airway reflexes that normally protect the lungs from stomach contents. Fasting reduces the volume and acidity of gastric contents, lowering the risk of aspiration pneumonia if vomiting occurs during induction.

Does a higher ASA class mean the surgery will be cancelled? No. ASA class describes baseline risk, not a pass/fail gate. Higher-class patients often still go to surgery, but with more aggressive optimization, closer monitoring, and sometimes a different anesthetic technique.

Is postoperative fever always something to worry about? Not necessarily. Low-grade fever in the first 24–48 hours is common and often due to atelectasis or the normal inflammatory response to surgery. Persistent, high-grade, or late fever, or fever with localizing signs, needs active investigation.

Why is early mobilization pushed so hard after surgery? Because a single intervention — getting the patient out of bed and walking — reduces two of the biggest postoperative killers at once: atelectasis (by improving lung expansion) and venous thromboembolism (by preventing venous stasis).

What's the difference between preoperative optimization and preoperative clearance? Optimization means actively improving a modifiable condition (like tightening glucose control) before surgery. Clearance is a risk assessment stating the patient's condition has been evaluated and the anesthesia/surgical team is informed of the risk — it does not mean the patient is risk-free.

Quick Revision

• ASA I–VI grades baseline health/risk; higher class means more optimization and monitoring, not automatic cancellation.
• Order preoperative investigations based on history and procedure, not as a routine panel.
• NPO guidelines: clear liquids 2 hours, breast milk 4 hours, light meal 6 hours, heavy meal 8 hours.
• Fasting exists to prevent aspiration during loss of airway reflexes under anesthesia.
• Postoperative fever "5 W's": Wind (atelectasis, day 1) → Water (UTI, day 3) → Wound (SSI, day 5) → Walking (DVT/PE, day 7) → Wonder drugs (later).
• Atelectasis is the most common cause of fever in the first 48 hours; prevent with incentive spirometry and mobilization.
• Surgical site infections typically present on postoperative day 5–7.
• VTE is a leading preventable cause of postoperative death — use mechanical plus pharmacologic prophylaxis.
• Postoperative ileus is expected for 1–3 days after abdominal surgery; beyond 3–5 days, suspect mechanical obstruction.
• Multimodal analgesia controls pain while reducing opioid-related ileus and respiratory depression.
• ERAS protocols (minimal fasting, early feeding, early mobilization, non-opioid analgesia) reduce complications and length of stay.
• Informed consent and surgical site marking are safety steps that prevent wrong-site/wrong-procedure surgery.

Related Topics

Prerequisites

• Basic physiology of respiratory and cardiovascular systems
• Principles of anesthesia and sedation
• Wound healing basics

Related Topics

• Fluid and electrolyte management in surgical patients
• Shock and hemodynamic monitoring
• Surgical site infection prevention

Next Topics

• Surgical Complications and Their Management
• Nutrition in the Surgical Patient
• Enhanced Recovery After Surgery (ERAS) Protocols in Detail