Postoperative Care Practice Questions

Q: What oxygen concentration should be supplemented in all post-operative patients?

30-35%. **Explanation:** In the immediate postoperative period, patients are at high risk for **postoperative hypoxemia** due to several factors: residual effects of anesthetic agents (causing respiratory depression), splinting due to pain, and ventilation-perfusion (V/Q) mismatch caused by atelectasis. **Why 30-35% is the Correct Answer:** Standard practice in the Post-Anesthesia Care Unit (PACU) is to provide supplemental oxygen to maintain an arterial oxygen saturation ($SaO_2$) above 94%. An inspired oxygen concentration ($FiO_2$) of **30-35%** is generally sufficient to prevent hypoxemia in most healthy patients without causing complications. This is typically achieved using a simple face mask (5-6 L/min) or nasal prongs (2-4 L/min). **Analysis of Incorrect Options:** * **A & B (40-60%):** These concentrations are unnecessarily high for routine cases. High $FiO_2$ levels can lead to **absorption atelectasis** (where high oxygen replaces nitrogen in the alveoli, causing them to collapse) and can mask hypoventilation by maintaining saturation despite rising $CO_2$ levels. * **D (20-25%):** Room air is 21%. Providing only 20-25% oxygen offers little to no margin of safety against the physiological shunts and decreased Functional Residual Capacity (FRC) common after surgery. **High-Yield Clinical Pearls for NEET-PG:** * **Diffusion Hypoxia:** Specifically seen after Nitrous Oxide ($N_2O$) use; $N_2O$ rushes out of the blood into the alveoli, diluting oxygen. This is prevented by giving **100% $O_2$ for 5-10 minutes** at the end of surgery. * **Target Saturation:** In patients with COPD or chronic hypercapnia, the target $SaO_2$ is lower (88-92%) to avoid suppressing the hypoxic respiratory drive. * **Most common cause of early post-op hypoxemia:** Atelectasis and decreased FRC.

Q: Peri-operative respiratory failure is most commonly associated with which type?

Type 3. **Explanation:** Respiratory failure is classified into four types based on the underlying pathophysiology. In the peri-operative setting, **Type 3 Respiratory Failure** is the most characteristic and common form. **Why Type 3 is Correct:** Type 3 respiratory failure is specifically defined as **Peri-operative Respiratory Failure**. It is primarily caused by **atelectasis** (collapse of alveoli). During surgery, factors such as general anesthesia, use of muscle relaxants, upper abdominal incisions, and pain lead to a decrease in Functional Residual Capacity (FRC). This causes the small airways to close, especially in dependent lung zones, leading to ventilation-perfusion (V/Q) mismatch and hypoxemia. **Analysis of Incorrect Options:** * **Type 1 (Hypoxemic):** Characterized by $PaO_2 45$ mmHg. It is caused by pump failure (e.g., COPD, neuromuscular disorders, or opioid overdose). * **Type 4 (Shock):** This occurs in patients who are intubated and ventilated during the resuscitation of shock (hypovolemic, septic, or cardiogenic) to reduce the metabolic demand of breathing muscles. **High-Yield Clinical Pearls for NEET-PG:** * **Management of Type 3:** Best managed with incentive spirometry, early mobilization, adequate analgesia (to prevent splinting), and PEEP (Positive End-Expiratory Pressure). * **Risk Factors:** Upper abdominal and thoracic surgeries carry the highest risk due to diaphragmatic dysfunction. * **Key Distinction:** Remember the "Rule of 4": Type 1 (Oxygenation), Type 2 (Ventilation), Type 3 (Atelectasis/Peri-operative), Type 4 (Shock/Hypoperfusion).

Q: Post-anesthetic nausea and vomiting is uncommon with which of the following agents?

Propofol. **Explanation:** **Propofol** is the correct answer because it possesses unique **anti-emetic properties**. Unlike most anesthetic agents, propofol directly modulates the chemoreceptor trigger zone (CTZ) and decreases dopaminergic activity in the area postrema. It is considered the drug of choice for Total Intravenous Anesthesia (TIVA) specifically to reduce the incidence of Postoperative Nausea and Vomiting (PONV). **Analysis of Incorrect Options:** * **Halothane (Option B):** Inhalational agents (volatile anesthetics) are a primary risk factor for PONV. They trigger the vomiting center during the emergence phase of anesthesia. * **Fentanyl & Sufentanil (Options C & D):** These are potent opioids. Opioids are notorious for causing nausea and vomiting by increasing the sensitivity of the vestibular apparatus, delaying gastric emptying, and directly stimulating the CTZ in the medulla. **Clinical Pearls for NEET-PG:** * **Gold Standard for PONV Prophylaxis:** Propofol (TIVA) is the most effective anesthetic strategy to prevent PONV. * **Apfel Score:** A high-yield clinical tool used to predict PONV risk. Key risk factors include: Female gender, non-smoker status, history of motion sickness/PONV, and postoperative opioid use. * **Emetic Potential:** Nitrous oxide ($N_2O$) and Etomidate are also associated with a high incidence of PONV compared to Propofol. * **Management:** The first-line treatment for established PONV often includes 5-HT3 receptor antagonists (e.g., Ondansetron) or Dexamethasone.

Q: Which of the following drugs is commonly used for post-anesthetic shivering?

Meperidine. **Explanation:** **Post-anesthetic shivering (PAS)** is a common complication occurring in up to 40% of patients recovering from general anesthesia. It is primarily caused by intraoperative hypothermia and the effects of anesthetic agents on thermoregulatory control. **Why Meperidine is the Correct Choice:** **Meperidine (Pethidine)** is considered the drug of choice for treating post-anesthetic shivering. Unlike other opioids, meperidine possesses unique **anti-shivering properties** mediated through its potent agonist activity at **$\kappa$ (kappa) opioid receptors** and its inhibitory effect on the $\alpha_2$-adrenoceptor. It effectively lowers the shivering threshold (the core temperature at which the body initiates shivering) more significantly than it lowers the vasoconstriction threshold, providing rapid relief. **Analysis of Incorrect Options:** * **B. Methylmorphine (Codeine):** This is a weak opioid primarily used as an antitussive or for mild pain; it has no significant effect on the thermoregulatory center. * **C. Methadone:** A long-acting $\mu$-opioid agonist used for chronic pain and opioid withdrawal; it lacks the specific $\kappa$-receptor profile required to suppress shivering effectively. * **D. Morphine:** While morphine is a potent analgesic, it acts primarily on $\mu$-receptors. It is significantly less effective than meperidine in treating PAS and requires much higher doses to achieve a similar effect, increasing the risk of respiratory depression. **High-Yield Clinical Pearls for NEET-PG:** * **Mechanism:** Meperidine reduces the shivering threshold via $\kappa$-receptors and $\alpha_2$ agonism. * **Dose:** A low intravenous dose (12.5–25 mg) is usually sufficient for PAS. * **Other Drugs:** Alpha-2 agonists (Clonidine, Dexmedetomidine) and Tramadol are also effective alternatives. * **Gold Standard Prevention:** Forced-air warming (Bair Hugger) is the most effective non-pharmacological method to prevent PAS.

Q: Which of the following drugs is believed to be effective in the treatment of postoperative shivering?

Pethidine. **Explanation:** **Postoperative Shivering (POS)** is a common complication following general or spinal anesthesia, occurring in up to 40% of patients. It increases oxygen consumption, CO2 production, and metabolic rate, which can be detrimental in patients with limited cardiac or respiratory reserve. **Why Pethidine is the Correct Answer:** Pethidine (Meperidine) is considered the **gold standard** and the most effective drug for treating postoperative shivering. Unlike other opioids, pethidine has unique **agonist activity at the κ (kappa) opioid receptors** and also inhibits the reuptake of serotonin and norepinephrine. These actions significantly lower the shivering threshold in the hypothalamus, effectively suppressing the thermoregulatory response more efficiently than pure μ-agonists like morphine or fentanyl. **Analysis of Incorrect Options:** * **Ondansetron (A):** While some studies suggest 5-HT3 antagonists may have a prophylactic role in preventing shivering by modulating central temperature regulation, they are not the primary treatment of choice once shivering has started. * **Diclofenac Sodium (B) & Paracetamol (D):** These are Non-Steroidal Anti-Inflammatory Drugs (NSAIDs) and non-opioid analgesics. While excellent for postoperative pain management, they do not act on the central thermoregulatory mechanisms required to stop shivering. **Clinical Pearls for NEET-PG:** * **Mechanism of POS:** It is primarily caused by intraoperative core hypothermia and the "resetting" of the thermoregulatory threshold as anesthesia wears off. * **Dose of Pethidine:** A low dose (10–25 mg IV) is usually sufficient to stop shivering. * **Other Drugs:** Other agents used for prevention/treatment include **Tramadol**, **Clonidine**, and **Dexmedetomidine** (α2 agonists). * **Non-Pharmacological:** Forced-air warming (Bair Hugger) is the most effective way to prevent hypothermia intraoperatively.

Q: Postoperative shivering in the perioperative period is associated with what physiological change?

Increase in oxygen consumption. **Explanation:** Postoperative shivering (POS) is a common involuntary muscular activity occurring during recovery from general or regional anesthesia. It is primarily a thermoregulatory response to core hypothermia or the effects of anesthetic agents on the hypothalamus. **Why Option A is Correct:** Shivering involves intense, rhythmic skeletal muscle contractions. This metabolic activity significantly increases the body's demand for energy. Consequently, **oxygen consumption ($VO_2$) can increase by 200% to 500%**. This massive surge in oxygen demand can lead to hypoxemia, lactic acidosis, and increased carbon dioxide production, which is particularly dangerous in patients with limited cardiac or pulmonary reserve. **Why Other Options are Incorrect:** * **Option B:** Shivering triggers a **sympathetic nervous system surge**, leading to an *increase* in catecholamine release (norepinephrine and epinephrine), not a decrease. * **Option C:** Due to the sympathetic surge and increased metabolic demand, patients typically experience **tachycardia (increased heart rate) and hypertension (increased blood pressure)**. This increases myocardial oxygen demand and can precipitate myocardial ischemia or infarction in high-risk patients. **High-Yield Clinical Pearls for NEET-PG:** * **Mechanism:** Anesthetics cause peripheral vasodilation and inhibit the shivering threshold in the hypothalamus, leading to core-to-peripheral heat redistribution. * **Drug of Choice:** **Pethidine (Meperidine)** is the gold standard for treating postoperative shivering (dose: 10–25 mg IV). It acts on $\kappa$-opioid receptors to lower the shivering threshold. * **Other agents:** Clonidine, Tramadol, and Dexmedetomidine are also used for prevention and treatment. * **Complications:** Beyond metabolic stress, shivering increases intraocular and intracranial pressure and can cause wound dehiscence due to mechanical strain.

Question 1

What oxygen concentration should be supplemented in all post-operative patients?

Accepted Answer

30-35%

Answer

50-60%

Answer

40-45%

Answer

20-25%

Question 2

Peri-operative respiratory failure is most commonly associated with which type?

Accepted Answer

Type 3

Answer

Type 1

Answer

Type 2

Answer

Type 4

Question 3

Which of the following is consistent with return of muscle tone adequate to protect the airway from aspiration after reversal from anesthesia?

Accepted Answer

Five seconds sustained head lift

Answer

TOF ratio of 0.7

Answer

No fade detectable on Double Burst Tetanic Stimulation

Answer

Return of normal resting minute ventilation

Question 4

What is a cause of postoperative hypertension?

Accepted Answer

All of the above

Answer

Pre-operative hypertension

Answer

Inadequate analgesia

Answer

Phaeochromocytoma

Question 5

Post-anesthetic nausea and vomiting is uncommon with which of the following agents?

Accepted Answer

Propofol

Answer

Halothane

Answer

Fentanyl

Answer

Sufentanil

Question 6

Which of the following drugs is commonly used for post-anesthetic shivering?

Accepted Answer

Meperidine

Answer

Methylmorphine

Answer

Methadone

Answer

Morphine

Question 7

Which of the following drugs is believed to be effective in the treatment of postoperative shivering?

Accepted Answer

Pethidine

Answer

Ondansetron

Answer

Diclofenac sodium

Answer

Paracetamol

Question 8

Which drug worsens post-cardiothoracic surgery delirium?

Accepted Answer

Anticholinergic agents

Answer

Antipsychotics

Answer

Benzodiazepines

Answer

Antihistamines

Question 9

Postoperative shivering in the perioperative period is associated with what physiological change?

Accepted Answer

Increase in oxygen consumption

Answer

Decreased catecholamine release

Answer

Decreased heart rate and blood pressure

Answer

All of the above

Question 10

What is the most common rhythm disturbance during the early post-operative period?

Accepted Answer

Tachycardia

Answer

Bradycardia

Answer

Ventricular fibrillation

Answer

Complete heart block

Postoperative Care — MCQs

Postoperative Care — MCQs

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