It was well known that rib fractures with flail chest and multiple, severe displaced fractures could make patients apnea. Surgical treatment is conducive to the early recovery of such patients. The concerns for anesthesiologists are not only guaranteeing the oxygenation during the operation but also the successful extubation after the surgery. LMA anesthesia combined with nerve block is priority to ETI anesthesia. In 2012, Ambrogi4 had reported the successful use of LMA anesthesia for lung parenchymal resections. However, the surgery of rib fractures is different from VATS. Anesthesiologists should take account of the nerve block effect of surgical segments and the reduction of chest wall muscle twitching when the incision was separated.
The thoracic nerves are responsible for the sensation of the ribs and skin, and their distributions are consistent with the ribs. This is the theoretical basis for the application of epidural anesthesia in chest surgery. However, thoracic epidural anesthesia produces bilateral trunk block and thoracic sympathetic block, causes hypotension frequently. It’s also associated with serious complications, such as epidural hematoma and neuropathy. Furthermore, it has contraindication of abnormal coagulation. Therefore, a variety of nerve blocks are used clinically as alternatives to epidural anesthesia, such as serratus anterior plane block(SAPB), intercostal nerve block(INB), ESPB and TPB. however, there are some limitations to the above three methods. The local anesthetic of SAPB is distributed along the midaxillary line which is mostly close to the surgical incision, which would cause the muscle swelling and impact the surgical vision. INB requires multipoint injection, which makes the patient more painful and increases the risk of inadvertent intercostal vessels or pleura puncture. ESPB is a blockade of Intermuscular fascia, the incidence of complete block to achieve the disappearance of pain and temperature sensation is only 1/3.5 TPB has the advantage of certain effect which even equals to unilateral epidural anesthesia, and can be performed precisely by ultrasound-guidance. Thus we choose TPB as a part of anesthesia in our study.
The intercostal(IC) approach and the paralaminar(PL) approach are two most frequent approaches of TPB. According to our experience, A single injection of 0.375% ropivacaine 20ml via PL approach could block 4-5 segments of the sensory dermatome, which was consistent with Yasuko Take's conclusion.6 They found that the blocked dermatomes of sensory loss were wider in group PL vs group IC after 20 ml of 0.5% ropivacaine was injected, median number of blocked dermatomes was 3 in group IC and 4 in group PL. Our approach of TPB has the same transversal cross-sectional image as Taketa's PL approach, and is also consistent with the transversal IAP approach described by Krediet, et al.24 Unlike them, our puncture needle is inserted oblique to the skin from the lateral of the probe and advanced into the TPVS beyond the IAP. Based on our pilot experiment, we found that the block area toward caudal was more extensive than it toward cephalic. That’s the reason we chose the inject point of TPB at the second surgical segment from cephalic when the surgical segments were not more than 4 consecutive ribs. Besides, the PL approach was regarded as a better approach to block the dorsal ramus of thoracic nerves,7 so it was beneficial to postoperative analgesia for posterior costal fracture surgery. Finally, we think that ESPB is necessary to ensure the block effect of incision for posterior costal surgery. Because it can produce sensory blockade over the posterior as well as anterolateral thorax, and apply more effective analgesia for posterior rib fractures compared with SAPB.18
The dosage of sufentanil during the surgery in each patient ranged from 5 to 17(9.9 ±3.3) μg. It both kept BR at 15±3 breaths per minute, and achieved an acceptable effect of postoperative analgesia. In the result of our study, the 6th hour after the operation was generally the time point at which patients felt painful obviously. This was consistent with the duration of TPB postoperative analgesia(303.97±76.08 minutes) reported by Das S, et al.8 On account of the use of PCIA and intravenous infusion of lornoxicam as basic analgesia after operation, most patients had pain in an acceptable extent, except 4 patients (20%) with an NRS score of 5, occurred at 6 hours and 12 hours after operation respectively. They all received once rescue of pethidine. It indicated the multi-mode analgesia protocol was effective for rib surgery postoperatively. This result also suggests that we may achieve better postoperative analgesia by TPB catheterization in our future work, as reported by Ge Yeying.9
TPB may block the sympathetic ganglias of the corresponding segments, and lower the patients’ BP. Theoretically, the incidence of hypotension is positively related with the number of blocked segments. However, in our study, we found that the need for phenylephrine in the operation was not relative to the number of TPB inject points. It was consistent with the conclusion that a single TPB wouldn’t lower the blood pressure reported by other previous authors.19,20 But there was a significant correlation between the need for phenylephrine and ESPB combined. We could not clearly explain this event yet and will confirm and elaborate it in the future research.
We used one ED95 of rocuronium during induction to reduce muscle twitching . Since the innervating nerves of the serratus anterior muscle and latissimus dorsi muscle originate from the cervical spinal cord, TPB is ineffective in blocking these two groups of muscles. We found this dose can satisfy the surgeons when they exposed the wound. Gleen S.Murphy et al.10 pointed out that the residual effect of muscle relaxants was one of the causes of postoperative respiratory failure, critical respiratory events observed in 18.0% patients undergoing thoracic procedures. Althausen PL.11 reported the incidence of re-intubation after surgical stabilization of flail chest was 4.55%(1/22). In this study, all 20 patients recovered spontaneous breathing during the operation and could cough powerfully after extubation, no one needed for re-intubation. Obviously, this result was attributed to the selection of patients and the small sample size. We expect that LMA anesthesia can show this advantage with further research.
Most of the patients with rib fractures have apnea caused by the injury. However, the satisfactory effect of TPB can improve the oxygenation of the patients. Because respiratory amplitude was increased when the patients didn’t feel pain.12 We set oxygen concentration as 50% to reduce the risk of atelectasis caused by high oxygen concentration.13 Our results showed that SpO2 of all patients was 99.08±1.30 % during the operation, including 3 patients whose oxygen saturation was lower than 93% before the operation. The minimum value of oxygen saturation during operation was 87% which occurred transiently in one case. His preoperative chest CT showed a large amount of pleural effusion on the affected side of the chest cavity with incomplete atelectasis and consolidation of inferior lobe. The decline of SpO2 was attributable to obvious decrease of tidal volume caused by sufentanil. But it rose to 98% in a few minutes and kept at 100% till the end of surgery.
Carbon dioxide retention occurred in different degrees during spontaneous breathing in 20 patients. The EtCO2 of most of the patients was below 45mmHg at the end of the surgery, except one patient, his EtCO2 reached the highest value of 63mmHg in our research. All patients were extubated within 1-11(6±3) minutes after surgery, and remained awake without drowsiness after extubation, including the patient with the highest EtCO2 level. Their PaCO2 checked on the second day after surgery was also in the normal range. Permissive hypercapnia has been accepted early, O' Toole14 believed that hypercapnia could produce an anti-inflammatory effect by inhibiting NF-κB. And other scholars thought that hypercapnia had a protective effect on VILI.15,16 Hypercapnia can also improve pulmonary compliance through a non-surfactants mechanism, and enhance pulmonary vascular resistance by strengthening hypoxic pulmonary vasoconstriction to reduce pulmonary shunt.17 In summary, the patient's normal tidal volume and frequency during spontaneous breathing can meet the needs of intraoperative ventilation in this study. The perfect nerve block effect is the premise for the patient to breathe smoothly, because it can reduce the requirements of sufentanil which is responsible for respiratory inhibition, while sevoflurane itself does not produce obvious respiratory inhibition during the operation.
Postoperative pulmonary complications (PPCs) were always been concerned in thoracic surgery. Recruitment maneuver and suctioning airway secretion might be beneficial to the patients during ETI anesthesia. The sealing of the LMA is not as reliable as endotracheal catheter. But according to Russo’s report,21 the leak pressure of LMA supremeTM was 27.1 ± 5.2 cmH2O. So the LMA we used could meet the needs of the recruitment maneuver in general. Deserved to be mentioned, the LMA anesthesia combined with nerve block can shorten the time to extubation and apply a good analgesic effect to promote postoperative cough and sputum. In particular, the early recovery of spontaneous breath during operation reduces the interference of pulmonary function during mechanical ventilation. Because positive pressure ventilation not only changes the pressure gradient of the thoracic cavity and interferes with the distribution of intrapulmonary ventilation, but also leads to the imbalance of V/Q ratio with excessive or inadequate tidal volume. Besides, barotrauma and volume injury caused by mechanical ventilation can also cause VALI. All of the above show that spontaneous breath is beneficial to lung protection. Noda.22 concluded that patients of VATS with spontaneous breath had a significantly reduced incidence of postoperative respiratory complications including pneumonia and ARDS compared to ETI anesthesia.
In general, the deterioration of pulmonary function of thoracic surgery without lobe resection maximizes at 12 to 48 hours after surgery. It reflects in the decrease of PaO2 and increase of PaCO2. Therefore, we performed blood gas analysis on the second day after surgery. It was found that the postoperative PaO2 in 20 patients was improved compared with the preoperative PaO2 (p<0. 001). And no pneumonia was found by chest X-ray after surgery. It seemed that the LMA anesthesia wouldn’t increase the incidence of PPCs after rib fractures surgery, but it was limited by the small sample size. We will focus on it in our follow-up study.
Previous literature was retrospectively assessed for any complication of TPB, contained pleural punctures, pneumothorax, hypotension, bradycardia as well as signs and symptoms of local anesthetic toxicity. Incidence of pleural puncture was 0.6%, pneumothorax 0.26% and suspected toxicity from the local anesthetic 0.17%.23 It showed that the incidence of TPB complications was low, and ultrasound-guidance could make the procedure safer. We adopt two-person operation mode, one physician operate the ultrasound probe and needle, the other person performed the aspiration and injection. Color Doppler ultrasound was used to confirm that there were no vessels in the path of the needle. None of the above complications occurred in 20 patients.