This prospective, observational study was approved by the Ethics Committee of Shanghai Sixth People's Hospital(2019-53) and was registered at www.chictr.org.cn(ChiCTR1900023763). Twenty patients from June to August 2019, scheduled for surgical reduction and fixation of unilateral isolated rib fractures in our hospital, were enrolled in this study. The informed consent was signed by all patients. Inclusion criteria: 1.ASA I and II, 2. aged 18–70 years, 3. BMI<30, 4. Preoperative PaO2> 60mmHg, 5. Preoperative PaCO2< 50mmHg. Exclusion criteria: 1. Difficult airway, 2. Esophageal reflux, 3. Myasthenia gravis, 4. Abnormal coagulation system, 5. Gastric ulcer or hemorrhage, 6. Allergy to anesthesia-related drugs, 7. Asthma or chronic obstructive emphysema, 8. Pregnant women, 9. The patients presented with major thoracic vascular injuries.
All patients fasted for at least 8 h. Noninvasive blood pressure(BP), pulse oximetry(SpO2), and electrocardiography were established when the patients were admitted to the operating room.
The ultrasound-guided TPB was performed with S-Nerve™ Ultrasound System (Fujifilm SonoSite Inc. Bothell, WA, USA). The patient was placed in a lateral decubitus position. Transversal Inferior Articular Process(IAP) approach was applied. A convex array probe (5-2 MHz; C60x; Fujifilm SonoSite Inc. Bothell, WA, USA) was used to visualize the vertebral lamina, internal intercostal membrane and parietal pleura for prescanning(Figure 1). A 22-gauge, 8-cm puncture needle (KDL medical apparatus and instruments Co. Wenzhou, China) was inserted into the thoracic paravertebral space(TPVS) from the lateral side. 20-30ml of ropivacaine 0.375% was injected with no air or blood aspiration.
The injection point of TPVS was selected according to the fracture rib segments requiring surgery (hereinafter referred to "surgical segments"). If the surgical segments were not more than 4 consecutive ribs, 20ml of ropivacaine was injected into the TPVS of the second fractured rib, which was so called single-level block. If the surgical segments were more than 4 consecutive ribs, each 15 ml of ropivacaine was injected into the TPVS of the second and fifth fractured ribs, so called double-level block. We adopt two-person mode in TPBs, one physician operated the ultra-sound probe and needle, the other person performed the injection and aspiration. Before the needle was inserted, Color Doppler ultrasound was used to confirm that there were no vessels on the way to TPVS.
In the case of posterior rib fractures, ESPB was performed to enhance the regional effect of patient’s back. Because it can produce sensory blockade over the posterior as well as anterolateral thorax, and apply more effective analgesia for posterior rib fractures.19 20ml of ropivacaine 0.375% was injected between the fifth thoracic vertebral transverse process and erector spinae muscle(ESM) on the injured side, by the transversal in-plane approach under ultrasound-guidance(Figure 1).
The effect of regional block was evaluated in 15 minutes after nerve blockade, the dermatomes of sensory loss were measured by acupuncture and rubbing with alcohol gauze. If patient felt painless while deep breathing and vigorous coughing, and the range of reduction area of cold or pinprick sensation covered the incision. We considered that regional effect was complete, and the patient could be performed with LMA anesthesia. Otherwise, the patient was adopted endotracheal intubation anesthesia directly, and was excluded from the observational objects.
Anesthesia was induced with 0.1ug/kg sufentanil, 3mg/kg propofol and 0.3mg/kg rocuronium successively. We inserted a LMA SupremeTM(Teleflex Medical Co. Westmeath, Ireland) , and make the position was correct. A 14# gastric tube was placed in the esophagus regularly to reduce the gas which might escape into the esophagus during positive pressure ventilation, at the depth of 30cm from the upper incisor. Mechanical ventilation was commenced then: pressure-controlled volumn-guaranteed ventilation(PCV-VG) at 6 ml/kg and respiratory rate(RR) of 12 breaths/min. The inspiratory to expiratory ratio was 1:2.
During the operation, the oxygen concentration was 50%, and the flow rate was 2L/min. Sevoflurane concentration was adjusted in accordance with BP and HR, and the MAC value was adjusted between 0.7 and 1.2. Spontaneous breathing was maintained when it had recovered. A supplementary dose of 0.03 ug/kg sufentanil was allowed if HR was 20% faster than the basic value or RR was more than 20 breaths/min for surgical stimulation. Phenylephrine and atropine would be injected if necessary. At 15 minutes before the end of surgery, sevoflurane inhalation was ceased and 50mg flurbiprofen was infused intravenously. All patients didn’t receive any neuromuscular junction antagonist.
The patient would be converted to ETI anesthesia as follows: 1. surgical field was difficult to be exposed on account of muscular tension, 2. LMA couldn’t be placed in the right position, 3. hemodynamic instability occurred, 4. SpO2 was less than 90% or concentration of EtCO2 was more than 70mmHg persistently.
Postoperative continous analgesia(infusion rate 2ml/h, total volume 100ml) was conducted routinely. The analgesics contained with 500mg tramadol and 16mg lornoxicam. 50mg flurbiprofen was infused intravenously Bisindie in the ward. If the patient’s NRS was more than 4, 50mg pethidine would be administered intramuscularly as a remedy.
BP, HR, SpO2 were gathered during the anesthesia, Vt, RR, EtCO2 during spontaneous breathing were recorded. Another investigator recorded the postoperative extubation time and the events of agitation or hoarseness in the PACU. The preoperative and postoperative arterial blood gas analysis and chest film were obtained regularly.
PONV within 48 hours after surgery and NRS pain score at 6(T1), 12(T2), 24(T3) hours after surgery were assessed as well. We also gathered dosages of sufentanil and vasoactive drugs administered, the degree of surgeon’s satisfaction, and the case which would be converted to ETI during the operation.
SPSS 19.0 software was used for statistical analysis. Quantitative variables were expressed as means±SD. Categorical variables were expressed as quantitative value or percentage. The results of arterial blood gas analysis which measured pre/post-operatively were compared using the chi-square test or Fisher’s exact test. P<0.05 was considered to be statistically significant.