Characteristics of Pain during and after Cesarean Delivery

Most women reporting pain during cesarean delivery complain of “intense pulling and tugging” along with nausea and vomiting, which can be exacerbated by uterine exteriorization¹ (which is a common practice in the United States to facilitate uterine exposure and closure) or if bilateral tubal ligation² is performed during the cesarean delivery; these unpleasant sensations reflect the intense visceral stimuli that accompany manipulation of the peritoneum. Ways to alleviate these sensations are to ensure an adequate dense surgical block up to T4, to be confirmed with pinprick testing, which can be easier to achieve with a spinal anesthetic than with an epidural anesthetic. Short-acting opioids are essential and can be given with the spinal local anesthetic or via an indwelling epidural catheter.^3–5 As an additional adjuvant, spinal or epidural clonidine may be used.⁵ Clonidine has been shown to be extremely effective in reducing intraoperative pain.

Predicting Women at Risk for Pain after Cesarean Delivery

There have been several studies trying to identify which women will be more likely to suffer acute and persistent pain after cesarean delivery. Some have used experimental pain modalities such as quantitative sensory tests (QSTs) to predict women’s risk for intense postcesarean pain.^18–24 Problems with such experimental tests is that depending on the pain modality used, these tests may not necessarily accurately predict postpartum pain because of its complex nature (including uterine cramping and postoperative pain). In addition, most of these tests are not easy to perform in a clinical setting and will not be directly useful and applicable to guide clinicians caring for women during cesarean delivery. Questions to assess women’s pain catastrophization,¹⁸ level of anxiety, and anticipated pain²⁵ have been shown to predict acute postcesarean pain. Finally, testing women undergoing a repeat cesarean delivery to assess whether some degree of scar hyperalgesia, which reflects hypersensitization, is present prior to surgery has been shown to predict acute postcesarean pain and analgesic consumption in the first 48 hours following the repeated procedure.¹¹ This confirms the concept that central sensitization preceding surgery may impair pain modulation and result in the second surgical procedure, here a repeat cesarean delivery, to cause more severe pain and potentially hyperalgesia and chronic pain. Identifying women with predisposing factors such as preexisting chronic pain, neuropathic symptoms, or other contributors such as psychological or genetic factors will ensure that antihyperalgesic/neuropathic adjuvants be targeted to the subset of women who actually need these additional medications (Figure 40.1).

Figure 40.1 Proposed model for prescreening of pain risk factors to identify women likely to benefit from adjuvant modalities for postcesarean analgesia, in addition to standard multimodal analgesia. TAP, Transversus Abdominis Plane Block; QLB, Quadratus Lumborum Block.

Anesthetic Options for a Repeat Cesarean Delivery to Reduce Acute Pain and Minimize the Risk for Persistent Postoperative Pain in Women at Risk

1. 
   

   1. A single shot spinal (SSS) with

   
   
   
   
   • 
     

     A standard spinal solution with or without clonidine

   
   
   
   
2. 
   

   2. A combined spinal-epidural (CSE) with

   
   
   
   
   • 
     

     A standard spinal solution

     
     
   • 
     

     Option to top up the epidural catheter intraoperatively if necessary

     
     
   • 
     

     Option to keep the epidural catheter for postcesarean analgesia

     
     
     
     
     • 
       

       Intermittent dosing with long-acting opioids

       
       
     • 
       

       Continuous epidural infusion with PCEA

     
     

   
   
   
   
3. 
   

   3. Intravenous ketamine intraoperatively

   
   
4. 
   

   4. Transversus abdominis plane (TAP) block or Quadratus Lumborum block (QLB) for breakthrough pain

   
   
5. 
   

   5. Prolonged oral gabapentin (see Table 40.1 for drug doses)

Neuraxial Clonidine

Clonidine is a potent α₂-adrenergic receptor agonist with antinociceptive effects acting via descending pathways to the dorsal horn of the spinal cord. It is effective for both somatic and visceral pain.²⁶ Intrathecal clonidine added to local anesthetics for surgery prolongs the surgical block time (sensory regression to L2 and duration of motor block) and the time to first analgesic request.²⁷ Multiple studies have evaluated the effect of intrathecal clonidine on intraoperative analgesia, onset and duration of surgical block, time to first analgesic request, morphine-sparing effect, shivering, and side-effect profile in women receiving varying doses of intrathecal clonidine for elective cesarean delivery.^{5, 28–35}

Taken together, all these studies suggest that adding an “intermediate” dose of clonidine (60–100 µg) prolongs the surgical block by up to 60 minutes, delays the time to first analgesic request for breakthrough pain, and has a beneficial effect on intraoperative shivering.³⁶ None of the studies reported severe hypotension with any of the studied doses, including relatively high doses (150 µg).^{33, 35} The proposed explanation is that hypotension occurs in almost 100 percent of women immediately after injection of the spinal solution; therefore, adding clonidine will not increase the incidence of hypotension and will be easily managed with the current practice of using a vasopressor infusion (typically phenylephrine) during cesarean delivery. However, because the effect of neuraxial clonidine may outlast the surgical time, maternal blood pressure may remain low in the post-anesthesia care unit (PACU), and maintaining a phenylephrine infusion for a few hours in the PACU may be required in some cases. While the sedative effect of clonidine has been evaluated, the anxiolytic effect of spinal clonidine has not been assessed. It is unclear whether spinal clonidine reduces the likelihood of suffering chronic postcesarean pain, most likely because this event is so uncommon, and much larger studies would be needed to explore this effect or studies that prescreen women to identify those most likely to benefit from the addition of an antihyperalgesic drug. Based on our vast clinical experience with spinal clonidine for cesarean deliveries, clonidine is best suited for women who either already suffer chronic pain, are opioid tolerant, have had a suboptimal experience with a previous cesarean delivery (anesthetic block not sufficiently dense, not lasting long enough, severe postcesarean pain) and/or are extremely anxious.

Intravenous Ketamine

Ketamine, an N-methyl-d-aspartate (NMDA) receptor antagonist, has been suggested as an intraoperative adjuvant to reduce acute postoperative pain, reduce opioid-related side effects, and potentially prevent chronic postoperative pain. Systematic reviews have demonstrated a morphine-sparing effect postoperatively³⁷ but insufficient evidence to support its routine use to prevent chronic pain.³⁸ In a recent systematic review and meta-analysis of the effects of ketamine during cesarean delivery under spinal or general anesthesia,³⁹ ketamine significantly delayed time to first analgesic request and reduced pain scores 2 hours after cesarean delivery under spinal anesthesia.

To our knowledge, no academic center in the United States uses IV ketamine (as a bolus or per infusion) to prevent intraoperative pain at the beginning of the procedure. Current recommendations are not for its routine use, although doses of titrated IV ketamine may be offered to women reporting significant intraoperative pain.

Oral Gabapentin

Preoperative administration of gabapentinoids (gabapentin or pregabalin) to prevent severe acute and chronic postoperative pain has been evaluated.⁴⁰ In the context of cesarean delivery, only three studies have evaluated the effect of a single preoperative dose of oral gabapentin, with mixed results.^41–43 Doses were either 300 mg^{41, 42} or 600 mg^{42, 43} taken 2 hours before cesarean delivery. It is possible that both the timing and duration were insufficient for both a morphine-sparing effect and the prevention of neuropathic pain. Starting gabapentinoids 48 hours prior to surgery and for a duration of at least 2–3 weeks to elicit a long-lasting effect has been proposed.⁴⁰ Women at low risk for severe acute postcesarean pain are unlikely to benefit from the administration of a single oral dose of gabapentin preoperatively, but for selected women at risk for neuropathic pain, prolonged gabapentin may be beneficial.

Regional Truncal Blocks

The transversus abdominis plane (TAP) block is a recently investigated regional technique that is effective and relatively simple to manage. The duration of a single-shot TAP block does not seem to exceed 15–18 hours. Multiple studies have evaluated the efficacy of TAP blocks regarding their opioid-sparing ability, and when compared with spinal morphine, studies have shown that they are not more effective than spinal morphine and that there are probably no advantages in giving them routinely to women already receiving a morphine-containing spinal anesthetic.^44–51 One study also reported the same lack of efficacy when morphine had been administered epidurally.⁵² Reasons for this are that the analgesic effect of a single-shot TAP block does not last as long as the analgesia provided by a spinal dose of morphine and that uterine cramping is not relieved by a TAP block. It has therefore been suggested that TAP blocks should only be offered to selected women who cannot, or did not, receive spinal morphine or to those experiencing severe breakthrough pain despite multimodal analgesia,^53–57 particularly if abdominal wall pain is the dominant feature of the severe pain. Other studies on TAP block have confirmed its limited role in postoperative analgesia when spinal anaesthesia with a long acting opioid such as morphine is used as well as the use of TAP block for cesarean delivery under general anesthesia.^58–60 The benefit of adding antihyperalgesic adjuvants (i.e. clonidine) to TAP solutions remains to be further studied.⁶¹ Threading bilateral catheters into the TAP for repeated boluses every 8 hours have been shown to provide successful analgesia for up to 72 hours after delivery.⁶² Of note, local anesthetic toxicity has been reported within 30 minutes of injection,^63–65 and it is therefore important to adjust the local anesthetic dosing to women’s weight, to monitor for possible signs of systemic toxicity, and to be prepared to manage seizures.

The Quadratus Lumborum block (QLB) has also been used for postoperative analgesia after cesarean delivery. The main advantage of QLB compared to the TAP block is the extension of local anesthetic agent beyond the transversus abdominis plane to the thoracic paravertebral space. Two studies on QLB for post-operative analgesia after caesarean section under spinal, have reported it significantly reduces morphine consumption in combination with a multimodal analgesic regimen. ^{66, 67}

In summary, severe acute pain after cesarean delivery despite multimodal analgesia is not uncommon and requires early identification and management of severe pain to prevent persistent pain, surgery-related symptoms with neuropathic characteristics, and the very rare case of chronic postcesarean pain. In women with risk factors for postoperative pain or with allergies precluding the use of morphine and/or NSAIDs, additional modalities should be offered. In the future, more studies to identify preoperatively who may be at risk for pain are likely to propose tailored postcesarean analgesia.⁶⁸