Prospective Observational Investigation of Capnography and Pulse Oximetry Monitoring After Cesarean Delivery With Intrathecal Morphine

Analgesia after cesarean section - what is new?

PURPOSE OF REVIEW

Cesarean section is the most frequent surgical intervention, and pain following cesarean delivery unfortunately remains a common issue. The purpose of this article is to highlight the most effective and efficient options for postcesarean analgesia and to summarize current guidelines.

RECENT FINDINGS

The most effective form of postoperative analgesia is through neuraxial morphine. With adequate dosing, clinically relevant respiratory depression is extremely rare. It is important to identify women with increased risk of respiratory depression, as they might require more intensive postoperative monitoring. If neuraxial morphine cannot be used, abdominal wall block or surgical wound infiltration are very valuable alternatives. A multimodal regimen with intraoperative intravenous dexamethasone, fixed doses of paracetamol/acetaminophen, and nonsteroidal anti-inflammatory drugs reduce postcesarean opioid use. As the use of postoperative lumbar epidural analgesia impairs mobilization, double epidural catheters with lower thoracic epidural analgesia are a possible alternative.

SUMMARY

Adequate analgesia following cesarean delivery is still underused. Simple measures, such as multimodal analgesia regimens should be standardized according to institutional circumstances and defined as part of a treatment plan. Neuraxial morphine should be used whenever possible. If it cannot be used, abdominal wall blocks or surgical wound infiltration are good alternatives.

Nocturnal respiratory abnormalities among ward-level postoperative patients as detected by the Capnostream 20p monitor: A blinded observational study

PURPOSE

This prospective observational study aimed to establish the frequency of postoperative nocturnal respiratory abnormalities among patients undergoing major surgery who received ward-level care. These abnormalities may have implications for postoperative pulmonary complications (PPCs).

METHODS

Eligible patients underwent blinded noninvasive continuous capnography with pulse oximetry using the Capnostream™ 20p monitor over the first postoperative night. All patients received oxygen supplementation and patient-controlled opioid analgesia. The primary outcome was the number of prolonged apnea events (PAEs), defined as end-tidal carbon dioxide (EtCO2) ≤5 mmHg for 30-120 seconds or EtCO2 ≤5 mmHg for >120 seconds with oxygen saturation (SpO2) <85%. Secondary outcomes were the proportion of recorded time that physiological indices were aberrant, including the apnea index (AI), oxygen desaturation index (ODI), integrated pulmonary index (IPI), and SpO2. Exploratory analysis was conducted to assess the associations between PAEs, PPCs, and pre-defined factors.

RESULTS

Among 125 patients who had sufficient data for analysis, a total of 1800 PAEs occurred in 67 (53.4%) patients. The highest quartile accounted for 89.1% of all events. Amongst patients who experienced any PAEs, the median (IQR) number of PAE/patient was four (2-12). As proportions of recorded time (median (IQR)), AI, ODI, and IPI were aberrant for 12.4% (0-43.2%), 19.1% (2.0-57.1%), and 11.5% (3.1-33.3%) respectively. Only age, ARISCAT, and opioid consumption/kg were associated with PPCs.

CONCLUSIONS

PAE and aberrant indices were frequently detected on the first postoperative night. However, they did not correlate with PPCs. Future research should investigate the significance of detected aberrations.

Respiratory depression following cesarean section with single-shot spinal with 100 μg morphine

PURPOSE

Little evidence is available regarding bradypnea measured using continuous monitoring following cesarean section. We aimed to evaluate the rate of cumulative bradypnea time (total bradypnea time/total monitoring time) and its related factors in these parturients.

METHODS

This prospective observational study included women undergoing cesarean section under single-shot spinal anesthesia of 0.1 mg morphine. The Berlin Questionnaire was used to screen for sleep apnea syndrome preoperatively. Respiratory rate and oxygen saturation (SpO₂) were monitored continuously using an adhesive acoustic respiration sensor and pulse oximeter, respectively, at least 6 h after cesarean section. Bradypnea was defined as a respiratory rate < 8 breaths/min lasting at least 25 s (sustained bradypnea) or at least 15 s (immediate bradypnea). Hypoxemia was defined as SpO₂ < 92% lasting at least 25 s (sustained hypoxemia) or at least 15 s (immediate hypoxemia). Multiple regression analysis was applied to assess factors related to the rate of cumulative sustained bradypnea.

RESULTS

Of 159 patients, the Berlin Questionnaire was positive in 16.3%, and 77 (48.4%) experienced sustained bradypnea. The median rate of cumulative sustained bradypnea time was 0.70% (interquartile range 0.35-1.45%) without any related factors. The incidence of immediate bradypnea and sustained and immediate hypoxemia were 58.5%, 24.5%, and 37.7%, respectively. However, none of the factors were significant.

CONCLUSION

After cesarean section was performed with 0.1 mg intrathecal morphine, respiratory depression events were commonly observed. However, the rate of cumulative bradypnea time was very low and there were no related factors.

Clinical implications of opioid-induced ventilatory impairment

Opioid-induced ventilatory impairment is the primary mechanism of harm from opioid use. Opioids suppress the activity of the central respiratory centres and are sedating, leading to impairment of alveolar ventilation.Respiratory physiological changes induced with acute opioid use include depression of the hypercapnic ventilatory response and hypoxic ventilatory response. In chronic opioid use a compensatory increase in hypoxic ventilatory response maintains ventilation and contributes to the onset of sleep-disordered breathing patterns of central sleep apnoea and ataxic breathing. Supplemental oxygen use in those at risk of opioid-induced ventilatory impairment requires careful consideration by the clinician to prevent failure to detect hypoventilation, if oximetry is being relied on, and the overriding of hypoxic ventilatory drive. Obstructive sleep apnoea and opioid-induced ventilatory impairment are frequently associated, with this interrelationship being complex and often unpredictable. Monitoring the patient for opioid-induced ventilatory impairment poses challenges in the areas of reliability, avoidance of alarm fatigue, cost, and personnel demands. Many situations remain in which patients cannot be provided effective analgesia without opioids, and for these the clinician requires a comprehensive knowledge of opioid-induced ventilatory impairment.

[Neuraxial Morphine for Postoperative Analgesia after Caesarean Deliveries]

The use of neuraxial morphine, in combination with nonopioid analgesic regimens for postoperative analgesia after Caesarean deliveries is common practice, especially in the Anglo-American world. Neuraxial morphine offers a longer-lasting superior analgesia than intravenous opioids or patient-controlled analgesia. If neuraxial anaesthesia is being used for a caesarean delivery, it may be recommended to concomitantly administer neuraxial morphine for the postoperative analgesia.A low dose of neuraxial morphine in a healthy parturient bears a low morbidity and mortality risk. The optimal frequency, duration and modality of respiratory monitoring for patients at low risk for respiratory depression is dependent on the dose of morphine administered and the patient-specific and obstetric risk profile.

Sequence analysis of capnography waveform abnormalities during nurse-administered procedural sedation and analgesia in the cardiac catheterization laboratory

Identifying common patterns in capnography waveform abnormalities and the factors that influence these patterns could yield insights to optimize responses to sedation-induced respiratory depression. Respiratory state sequences for 102 patients who had a procedure in a cardiac catheterisation laboratory with procedural sedation and analgesia were developed by classifying each second of procedures into a state of normal breathing or other capnography waveform abnormalities based on pre-specified cut-offs for respiratory rate and end-tidal CO2 concentration. Hierarchical clustering identified four common patterns in respiratory state sequences, which were characterized by a predominance of the state assigned normal breathing (n = 42; 41%), hypopneic hypoventilation (n = 38; 38%), apnea (n = 15; 15%) and bradypneic hypoventilation (n = 7; 7%). A multivariable distance matrix regression model including demographic and clinical variables explained 28% of the variation in inter-individual differences in respiratory state sequences. Obstructive sleep apnea (R2 = 2.4%; p = 0.02), smoking status (R2 = 2.8%; p = 0.01), Charlson comorbidity index score (R2 = 2.5%; p = 0.021), peak transcutaneous carbon dioxide concentration (R2 = 4.1%; p = 0.002) and receiving an intervention to support respiration (R2 = 5.6%; p = 0.001) were significant covariates but each explained only small amounts of the variation in respiratory state sequences. Oxygen desaturation (SpO2 < 90%) was rare (n = 3; 3%) and not associated with respiratory state sequence trajectories.