Obstetric Anesthesia — MCQs

A 28-year-old female opts for painless labor. On administration of the epidural anesthetic, there is a sudden drop in the blood pressure. The reason for this was found to be accidental intravenous injection of the anesthetic drug. Which of the following drugs is the most likely responsible for this condition?

Q34Medium

Which regional anaesthesia technique is least likely to provide adequate analgesic benefit during the first stage of labor?

Q35Medium

A 39-year-old female is 40 weeks pregnant and has 4 cm cervical dilation. Which is the safest option for analgesia during labor?

Q36Medium

A 21-year-old lady with a history of hypersensitivity to neostigmine is scheduled for an elective cesarean section under general anesthesia. Which muscle relaxant is the most appropriate choice for this patient?

Q37Easy

Which of the following drugs must always be available for emergency use in the labor ward if a patient is on opioid analgesia?

Q38Medium

Which of the following is NOT continued prior to an elective cesarean section in a term gestation, obese female with hypertension, diabetes, and chronic aortoiliac obstruction?

Q39

In emergency caesarian section rapid induction of anaesthesia is done to –

Q40

A female presents with placenta previa with active bleeding and blood pressure of 80/50 mm Hg and pulse rate of 140 bpm. The choice of anaesthesia for emergency cesarean section in this female is?

Obstetric Anesthesia Indian Medical PG Practice Questions and MCQs

Question 31: When providing general anesthesia during pregnancy, what is the effect on the minimum alveolar concentration (MAC)?

A. Increased
B. Decreased (Correct Answer)
C. Unchanged
D. Variable

Explanation: **Explanation:** The correct answer is **Decreased (Option B)**. During pregnancy, the Minimum Alveolar Concentration (MAC) of volatile anesthetic agents decreases by approximately **25% to 40%**. This reduction begins as early as the 8th to 12th week of gestation and returns to normal within 72 hours postpartum. **Why the MAC is Decreased:** 1. **Hormonal Influence:** Elevated levels of **progesterone** act as a potent sedative and anesthetic enhancer. Progesterone increases the activity of GABA receptors, thereby reducing the requirement for volatile agents. 2. **Endogenous Opioids:** There is an increase in the levels of endogenous opioid peptides (endorphins and enkephalins) during pregnancy, which raises the pain threshold and decreases anesthetic requirements. 3. **Physiological Changes:** Increased cardiac output and minute ventilation lead to faster induction, but the primary reason for reduced MAC is the altered neurosensitivity of the CNS. **Why other options are incorrect:** * **A. Increased:** MAC is never increased in pregnancy. Increased MAC is seen in conditions like hyperthermia, hypernatremia, or chronic alcohol abuse. * **C & D. Unchanged/Variable:** These are incorrect because the physiological shift toward increased sensitivity to anesthetics is a consistent and predictable finding in all pregnant patients. **High-Yield Clinical Pearls for NEET-PG:** * **Rapid Induction:** Pregnant patients have a **decreased Functional Residual Capacity (FRC)** and **increased Minute Ventilation**, leading to a rapid rise in alveolar concentration ($F_A/F_I$ ratio). This results in faster induction and a higher risk of anesthetic overdose if not carefully titrated. * **Aspiration Risk:** Always consider a pregnant patient after the first trimester as having a "full stomach" due to displaced anatomy and progesterone-mediated relaxation of the lower esophageal sphincter. * **Local Anesthetics:** Sensitivity to local anesthetics (for spinal/epidural) is also **increased**, requiring a dose reduction of about 25-30%.

Question 32: Which inhalational agent is a good uterine relaxant?

A. Halothane (Correct Answer)
B. Isoflurane
C. Sevoflurane
D. Desflurane

Explanation: **Explanation:** Inhalational anesthetics are known to cause dose-dependent relaxation of the uterine smooth muscle. Among the options provided, **Halothane** is traditionally considered the most potent uterine relaxant. **1. Why Halothane is Correct:** Halothane significantly decreases uterine tone and inhibits contractions by interfering with calcium mobilization in the myometrium. Historically, it was the agent of choice for procedures requiring profound uterine relaxation, such as **internal podalic version**, manual removal of a retained placenta, or breech extraction. While its use has declined due to the risk of "halothane hepatitis," it remains the classic textbook answer for maximal uterine relaxation. **2. Analysis of Incorrect Options:** * **Isoflurane, Sevoflurane, and Desflurane:** These modern ethers also cause uterine relaxation in a dose-dependent manner. However, at standard clinical concentrations (0.5–1.0 MAC), their effect is less profound than Halothane. They are preferred for routine Cesarean sections because they allow the uterus to remain responsive to oxytocics (like oxytocin), thereby minimizing postpartum hemorrhage (PPH). **3. Clinical Pearls for NEET-PG:** * **The "Double-Edged Sword":** While uterine relaxation is useful for intrauterine manipulations, it is a major risk factor for **Postpartum Hemorrhage (PPH)** due to uterine atony. * **MAC Values:** To prevent PPH during a C-section, inhalational agents are usually kept below **0.5–0.75 MAC**. * **Nitrous Oxide ($N_2O$):** Unlike volatile agents, $N_2O$ does **not** affect uterine contractility, making it safe regarding the risk of atony. * **Drug of Choice for Uterine Relaxation:** While Halothane is the most potent inhalational agent, **Nitroglycerin (IV or Sublingual)** is now often preferred clinically for rapid, short-acting uterine relaxation due to its superior safety profile.

Question 33: A 28-year-old female opts for painless labor. On administration of the epidural anesthetic, there is a sudden drop in the blood pressure. The reason for this was found to be accidental intravenous injection of the anesthetic drug. Which of the following drugs is the most likely responsible for this condition?

A. Tetracaine
B. Lignocaine
C. Ropivacaine
D. Bupivacaine (Correct Answer)

Explanation: ### Explanation The clinical scenario describes **Local Anesthetic Systemic Toxicity (LAST)** following an accidental intravascular injection during epidural placement. **Why Bupivacaine is the Correct Answer:** Bupivacaine is a long-acting amide local anesthetic frequently used in obstetrics. However, it is the most **cardiotoxic** local anesthetic. It binds intensely to cardiac sodium channels during systole and dissociates very slowly during diastole (the "fast-in, slow-out" phenomenon). This leads to profound refractory bradycardia, ventricular arrhythmias, and myocardial depression (hypotension). In pregnant patients, the risk is further increased due to progesterone-induced sensitivity of the myocardium to local anesthetics. **Analysis of Incorrect Options:** * **A. Tetracaine:** An ester-type local anesthetic primarily used for spinal anesthesia. While toxic in high doses, it is not the standard choice for labor epidurals nor is it as classically associated with the rapid cardiovascular collapse seen with bupivacaine. * **B. Lignocaine:** A medium-acting anesthetic. While it can cause LAST, its cardiac toxicity occurs at much higher concentrations than bupivacaine. CNS symptoms (seizures) usually precede cardiovascular collapse with lignocaine. * **C. Ropivacaine:** An S-enantiomer developed specifically to be a safer alternative to bupivacaine. It has a lower affinity for cardiac sodium channels and a higher threshold for both CNS and CV toxicity. **Clinical Pearls for NEET-PG:** * **Antidote for LAST:** Intravenous **Lipid Emulsion (20% Intralipid)** is the specific treatment for bupivacaine-induced cardiac arrest. * **CC/CNS Ratio:** Bupivacaine has a low therapeutic index. The dose required for cardiovascular collapse (CC) is only slightly higher than the dose that causes seizures (CNS), making it highly dangerous. * **Levobupivacaine:** The S-isomer of bupivacaine, which is also less cardiotoxic than the racemic mixture.

Question 34: Which regional anaesthesia technique is least likely to provide adequate analgesic benefit during the first stage of labor?

A. Lumbar epidural
B. Pudendal nerve block (Correct Answer)
C. Lumbar sympathetic block
D. Paracervical block

Explanation: To answer this question, one must understand the **neuroanatomy of labor pain**, which occurs in two distinct stages: ### 1. Why Pudendal Nerve Block is the Correct Answer The **first stage of labor** (cervical dilation and effacement) involves visceral pain mediated by T10 to L1 nerve roots. The **pudendal nerve (S2–S4)**, however, provides sensory innervation only to the lower vagina, vulva, and perineum. Therefore, a pudendal block is highly effective for the **second stage of labor** (crowning and delivery) and episiotomies, but it provides **zero analgesic benefit** for the uterine contractions and cervical stretching characteristic of the first stage. ### 2. Analysis of Incorrect Options * **Lumbar Epidural (A):** The "gold standard" for labor analgesia. By blocking the T10–L1 dermatomes, it effectively targets the visceral pain of the first stage and can be extended to S2–S4 for the second stage. * **Lumbar Sympathetic Block (C):** This block interrupts the sympathetic pathways (T10–L1) that carry pain impulses from the uterus and cervix. It is an effective, though less commonly used, alternative for first-stage pain. * **Paracervical Block (D):** This involves injecting local anesthetic into the fornices of the vagina to block the Frankenhäuser plexus. It specifically targets the visceral afferents of the cervix and uterus, making it effective for the first stage (though it carries a risk of fetal bradycardia). ### Clinical Pearls for NEET-PG * **Pain Pathways:** First Stage = **T10–L1** (Visceral); Second Stage = **T10–S4** (Somatic + Visceral). * **Pudendal Block Landmarks:** The anesthetic is injected near the **ischial spine**, where the nerve passes through the sacrospinous ligament. * **Epidural "Walking" Analgesia:** Achieved by using low-dose local anesthetics combined with opioids (e.g., Bupivacaine + Fentanyl), preserving motor function while providing sensory relief.

Question 35: A 39-year-old female is 40 weeks pregnant and has 4 cm cervical dilation. Which is the safest option for analgesia during labor?

A. Intramuscular pentazocine
B. Epidural block (Correct Answer)
C. Pudendal block
D. Premixed nitrous oxide and oxygen

Explanation: **Explanation:** **Epidural Analgesia** is considered the "gold standard" for labor pain relief. In a 39-year-old patient at 40 weeks gestation with 4 cm dilation (active phase of labor), it provides superior pain relief compared to all other modalities without significant systemic side effects for the mother or the fetus. It allows for a "walking epidural" (using low-dose local anesthetics with opioids), preserving motor function while providing excellent sensory block. **Why other options are incorrect:** * **Intramuscular Pentazocine:** Systemic opioids cross the placenta and can cause neonatal respiratory depression and decreased fetal heart rate variability. Pentazocine specifically can cause maternal psychotomimetic effects (hallucinations). * **Pudendal Block:** This is only effective for the **second stage of labor** (perineal distension). It does not relieve the pain of uterine contractions and cervical dilation characteristic of the first stage. * **Nitrous Oxide (Entonox):** While safe and easy to administer, it provides only modest analgesia and is often insufficient for the intense pain of the active phase of labor compared to the near-complete relief provided by an epidural. **High-Yield Clinical Pearls for NEET-PG:** * **Ideal Timing:** Epidural is best initiated during the active phase of labor (3–4 cm dilation), though current guidelines state it can be given whenever the patient requests it. * **Level of Block:** For the first stage of labor, a block from **T10 to L1** is required. For the second stage, it must extend to **S2–S4**. * **Most Common Side Effect:** Maternal **hypotension** (due to sympathetic blockade). This is managed with IV fluid pre-loading/co-loading and left uterine displacement. * **Contraindications:** Patient refusal, coagulopathy, skin infection at the site, and uncorrected maternal hypovolemia.

Question 36: A 21-year-old lady with a history of hypersensitivity to neostigmine is scheduled for an elective cesarean section under general anesthesia. Which muscle relaxant is the most appropriate choice for this patient?

A. Pancuronium
B. Atracurium (Correct Answer)
C. Rocuronium
D. Vecuronium

Explanation: ### Explanation The core clinical challenge in this scenario is the patient’s **hypersensitivity to neostigmine**. Neostigmine is the standard pharmacological reversal agent for non-depolarizing neuromuscular blocking agents (NMBAs). If neostigmine is contraindicated, the clinician must choose a muscle relaxant that does not strictly require pharmacological reversal or one for which an alternative reversal agent is available. **Why Atracurium is the Correct Choice:** Atracurium (and its isomer Cisatracurium) undergoes **Hofmann elimination**—a spontaneous, non-enzymatic degradation at physiological pH and temperature. Because it does not rely on hepatic metabolism or renal excretion for its termination of action, it is "self-reversing" over time. In a patient where neostigmine cannot be used, atracurium allows the clinician to simply wait for spontaneous recovery of neuromuscular function without the need for a reversal agent. **Analysis of Incorrect Options:** * **Pancuronium (A):** A long-acting NMBA primarily excreted by the kidneys. Its long duration of action makes it unsuitable for elective C-sections, and it necessitates reversal, which is contraindicated here. * **Rocuronium (C) & Vecuronium (D):** These are intermediate-acting aminosteroids. While Rocuronium can be reversed by **Sugammadex** (a selective relaxant binding agent), Sugammadex is often expensive or unavailable in many settings. In the context of standard NEET-PG logic, if the question points toward avoiding reversal agents entirely due to neostigmine allergy, Atracurium’s unique metabolism makes it the most classic "textbook" answer. **Clinical Pearls for NEET-PG:** * **Hofmann Elimination:** Dependent on **pH and Temperature**. Rate increases with hyperthermia/alkalosis and decreases with hypothermia/acidosis. * **Laudanosine:** A metabolite of atracurium that can cross the blood-brain barrier and potentially cause seizures (though rare in clinical doses). * **Drug of Choice in Organ Failure:** Atracurium/Cisatracurium are the preferred NMBAs for patients with renal or hepatic failure.

Question 37: Which of the following drugs must always be available for emergency use in the labor ward if a patient is on opioid analgesia?

A. Fentanyl
B. Naloxone (Correct Answer)
C. Morphine
D. Bupivacaine

Explanation: ### Explanation **Correct Answer: B. Naloxone** **Medical Concept:** Opioids (such as pethidine or morphine) are frequently used for systemic analgesia during labor. However, these drugs cross the placenta via simple diffusion and can cause significant **neonatal respiratory depression** if administered close to the time of delivery. **Naloxone** is a competitive opioid antagonist that binds to mu (μ) receptors with high affinity, reversing the sedative and respiratory-depressant effects of opioids. It is mandatory to have Naloxone available in the labor ward to manage both maternal overdose and, more critically, neonatal depression at birth. **Analysis of Incorrect Options:** * **A. Fentanyl:** This is a potent synthetic opioid used for labor analgesia (often in epidurals). It would worsen respiratory depression rather than treat it. * **C. Morphine:** A long-acting opioid that can cause prolonged neonatal depression due to its active metabolite (morphine-6-glucuronide). It is an indication for having Naloxone ready, not the emergency treatment itself. * **D. Bupivacaine:** A local anesthetic used for epidural/spinal anesthesia. While it can cause toxicity (LAST), the specific antidote for bupivacaine is Intralipid (20% lipid emulsion), not Naloxone. **High-Yield Clinical Pearls for NEET-PG:** * **Mechanism of Action:** Naloxone is a pure antagonist at $\mu$, $\kappa$, and $\delta$ receptors. * **Duration of Action:** Naloxone has a shorter half-life (approx. 30–60 mins) than most opioids. **Renarcotization** (re-sedation) can occur, necessitating repeated doses or a continuous infusion. * **Neonatal Dose:** If used for neonatal resuscitation (though currently less favored than positive pressure ventilation), the dose is 0.1 mg/kg. * **Contraindication:** Avoid Naloxone in newborns of opioid-dependent mothers, as it can precipitate **acute withdrawal seizures**.

Question 38: Which of the following is NOT continued prior to an elective cesarean section in a term gestation, obese female with hypertension, diabetes, and chronic aortoiliac obstruction?

A. Labetalol
B. Statins
C. Magnesium sulfate
D. Heparin (Correct Answer)

Explanation: In obstetric anesthesia, managing medications perioperatively requires balancing maternal comorbidities against the risks of surgical bleeding and neuraxial complications. **Explanation of the Correct Answer:** **Heparin (Option D)** is the correct answer because it must be discontinued prior to elective surgery. In a patient with chronic aortoiliac obstruction, heparin is likely used for thromboprophylaxis or anticoagulation. However, to safely perform **neuraxial anesthesia** (spinal or epidural)—the gold standard for elective cesarean sections—heparin must be paused to prevent the catastrophic risk of a **spinal-epidural hematoma**. For elective cases, Unfractionated Heparin (UFH) is typically stopped 4–6 hours prior, and Low Molecular Weight Heparin (LMWH) is stopped 12–24 hours prior. **Analysis of Incorrect Options:** * **Labetalol (Option A):** Antihypertensives (except ACE inhibitors/ARBs) are generally **continued** on the morning of surgery to prevent perioperative hypertension and rebound tachycardia. * **Statins (Option B):** Statins are typically **continued** in patients with chronic vascular disease (aortoiliac obstruction) due to their pleiotropic effects, which stabilize plaques and reduce perioperative cardiovascular events. * **Magnesium Sulfate (Option C):** In obstetrics, Magnesium is continued for seizure prophylaxis (preeclampsia) or neuroprotection. It is never withheld due to surgery, though the anesthesiologist must monitor for potentiated neuromuscular blockade. **NEET-PG High-Yield Pearls:** * **Neuraxial Guidelines:** Always check the "time-interval" between the last dose of anticoagulant and needle placement (e.g., 12 hours for prophylactic LMWH, 24 hours for therapeutic). * **Diabetes Management:** Oral hypoglycemics are held on the morning of surgery; insulin doses are adjusted (usually half-dose NPH). * **Aortocaval Compression:** In obese/term patients, remember to maintain **left uterine displacement** to prevent supine hypotension syndrome.

Question 39: In emergency caesarian section rapid induction of anaesthesia is done to –

A. Prevent gastric aspiration (Correct Answer)
B. Prevent fetal depression
C. All of the above
D. To decrease awareness

Explanation: ***Prevent gastric aspiration*** - Rapid sequence induction is crucial in emergency cesarean sections to minimize the risk of **pulmonary aspiration of gastric contents**. - Pregnant women are at increased risk due to **delayed gastric emptying**, increased intra-abdominal pressure, and a less competent gastroesophageal sphincter. *Prevent fetal depression* - While anesthetic agents can cross the placenta and cause fetal depression, rapid induction is primarily aimed at maternal safety through aspiration prevention, not solely preventing fetal effects. - The choice of anesthetic agents and their dosage is carefully managed to minimize fetal exposure and depression. *All of the above* - This option is incorrect because while preventing fetal depression is a concern, the primary and most immediate reason for rapid induction in an emergency C-section is to prevent **maternal gastric aspiration**. - Rapid induction techniques expedite intubation, limiting the time for regurgitation and aspiration. *To decrease awareness* - Preventing awareness during anesthesia is a goal in any surgical procedure, but standard induction methods are also effective for this. - Rapid induction's specific advantage in this context is the prevention of **aspiration**, not primarily to reduce awareness, which can be accomplished with slower inductions as well.

Question 40: A female presents with placenta previa with active bleeding and blood pressure of 80/50 mm Hg and pulse rate of 140 bpm. The choice of anaesthesia for emergency cesarean section in this female is?

A. General anesthesia with intravenous propofol
B. Spinal anesthesia
C. General anesthesia with intravenous ketamine (Correct Answer)
D. Epidural anesthesia

Explanation: ***General anesthesia with intravenous ketamine*** - **Ketamine** maintains sympathetic tone, supporting **blood pressure** in patients with significant **hemorrhage** and **hypovolemic shock**. - Its **bronchodilatory** properties are also beneficial, making it a suitable choice for this emergency scenario where the patient is **hemodynamically unstable**. *General anesthesia with intravenous propofol* - **Propofol** can cause significant **vasodilation** and myocardial depression, which would worsen the patient's existing **hypotension** and **tachycardia**. - Its use in an actively bleeding, **hemodynamically unstable** patient is generally contraindicated due to the risk of further **cardiovascular collapse**. *Spinal anesthesia* - **Spinal anesthesia** is contraindicated in patients with significant **hypovolemia** and **active bleeding** due to the risk of severe **hypotension**. - The sympathetic blockade caused by spinal anesthesia would exacerbate the patient's already compromised **hemodynamic status**, potentially leading to **cardiac arrest**. *Epidural anesthesia* - Similar to spinal anesthesia, **epidural anesthesia** causes **sympathetic blockade** and can lead to **hypotension**, making it unsuitable for a patient with **active bleeding** and **hypovolemic shock**. - The onset of **epidural blockade** is slower than spinal, but the hemodynamic effects are still detrimental in this critically ill patient.

Practice by Chapter

Physiological Changes in Pregnancy

Practice Questions

Labor Analgesia: Epidural and Combined Spinal-Epidural

Practice Questions

Anesthesia for Cesarean Delivery

Practice Questions

Difficult Airway in Obstetrics

Practice Questions

Preeclampsia and Eclampsia Management

Practice Questions

Obstetric Hemorrhage

Practice Questions

Amniotic Fluid Embolism

Practice Questions

Maternal Comorbidities

Practice Questions

High-Risk Obstetric Anesthesia

Practice Questions

Fetal Monitoring and Fetal Distress

Practice Questions

Postpartum Tubal Ligation

Practice Questions

Postdural Puncture Headache

Practice Questions

Want unlimited practice?

Get full access to all questions, explanations, and performance tracking.

Start For Free