The Analgesic Effect of Quadratus Lumborum Block and Its Postoperative Implication on Kidney Function
Condition: Anesthesia
Study type: Observational [Patient Registry]

Summary: 
      Regional anesthesia is frequently used in major surgery in association with general
      anesthesia to ensure adequate postoperative patient analgesia and to decrease the intra- and
      postoperative use of systemic analgesic drugs. Epidural analgesia (EP) is considered the
      standard regional analgesic technique that is widely used in abdominal surgery. Nonetheless,
      it has some limitations such as in colorectal surgery where complications in the form of
      muscular weakness, hemodynamic instability, and postural hypotension result in delayed
      patient ambulation.

      For these limitations, peripheral nerve blocks can be considered safer with less incidence of
      complications compared to the central neuraxial blocks especially with the use of ultrasound
      (US) as a guide in their techniques. Also, avoidance of the hemodynamic instability that may
      affect the postoperative kidney function can be considered an important issue in patients
      with risk for postoperative acute kidney injury (AKI).

      One of the latest techniques in the field of regional anesthesia is the quadratus lumborum
      (QL) block, which is based on US-guided injection of a local anesthetic agent into the
      thoracolumbar fascia surrounding the QL muscle. Several different approaches were described
      depending on the injection sites, for example, lateral, posterior, and anterior approaches .
      According to the ASRA-ESRA Delphi consensus, there was no consensus on naming quadratus
      lumborum block types where posterior QL had the strongest consensus in abdominal wall
      analgesia with 71%.

      After the QL block, there is evidence that the injectate spreads to the paravertebral space
      where it blocks the thoracolumbar nerves and the thoracic sympathetic trunk. Because it
      produces an extensive sensory block leading to adequate postoperative analgesia besides
      decreasing the systemic analgesic consumption, QL block is now considered an effective
      regional block that can be used in major abdominal surgery.

      40% of the cases diagnosed as having AKI occurred as a postoperative complication. Cardiac
      surgery carries the highest risk for AKI (18.7%), whereas general surgery comes second
      (13.2%). The risk factors of developing AKI may be general or causes related to the type and
      the setting of the surgery.

      Fluid depletion is one of the major factors that can occur perioperatively and leads to renal
      hypoperfusion, with subsequent renal arteriolar changes, attempting to maintain a normal
      glomerular filtration rate. The sympathetic effects of the neuroendocrine hormones may lead
      to renal vasoconstriction, aiming to redistribute the blood to the medulla; however, it may
      lead to renal ischemia.

      The renal blood flow can be assessed by a rapid bed-side noninvasive technique, using the
      renal Doppler resistive index (RI), which is one of the most fundamental parameters assessing
      renal perfusion, because it reflects the degree of the vascular resistance inside the kidney
      vascular bed and can be used to assess the modifications and the changes that occur in the
      renal blood flow.

      No previous studies so far discussed the effect of QL block on postoperative creatinine and
      blood ureal nitrogen (BUN) levels. While, regarding epidural analgesia, multiple articles are
      investigating the effect of epidural on postoperative kidney function using various indices,
      such as serum creatinine, BUN, sodium clearance, and urine output. As far as the authors
      know, this is the first study using the RI renal flow as a comparative parameter between the
      QL block and EP analgesia.

      This study aimed to assess the analgesic efficacy of QL block compared with epidural
      anesthesia as a primary outcome using the 10-point visual analog scale (VAS), time to first
      morphine requirement, and 24-hour morphine consumption. Also, to study the effect of both on
      postoperative kidney function as a secondary outcome using serum creatinine and BUN and renal
      flow assessment using renal Doppler.
    

Detailed description: 
      -  Study place: Ain Shams University Hospitals.

        -  Written informed consent will be taken from all patients.

        -  Patients with an American Society of Anesthesiologists (ASA) physical status I-III, aged
           between 35 and 65 years were included in this study and scheduled for short colorectal
           surgery (2-4 hours), such as segmental colectomies and polypectomy using either the sub
           umbilical incision or laparoscopic technique. Patients with major cardiac or cerebral
           vascular diseases, bleeding disorders (known contraindication for EP anesthesia and in
           QL which is considered a deep block), abnormal kidney functions (elevated creatinine,
           BUN level, or history of renal disease), and neurological disorders were excluded.
           Patients with known allergy to local anesthetics, puncture site infection, and body mass
           index (BMI) of >35 kg/m2 were also excluded. Also, patients with intra-operative
           complications such as hemodynamic instability and unexpected prolonged surgical duration
           were excluded. Patients who refused to consent to the study were not enrolled, without
           any discontinuation of their management.

      The selected patients were randomized using an automated computer-assisted method
      (www.randomizer.org), which divided them into 2 groups: the control group (EP) received
      epidural anesthesia, whereas the study group (QL) received a QL block. The interventions were
      done by well-experienced anesthesiologists.

      Renal Doppler. An experienced radiologist performed the renal Doppler with at least 5 years
      experience in the doppler field being blinded to the patients' data. A renal Doppler study
      was performed for both groups preoperatively and postoperatively. Patients were asked to lie
      supine or in lateral positions. The ultrasound (US) probe was applied to the anterior or
      midaxillary line with the probe in a transverse direction until the kidney was adequately
      visualized. The intrarenal and main renal arteries were assessed using color and pulse wave
      Doppler. The intrarenal arteries assessment was repeated at the upper, mid, and lower pole
      levels of each kidney. Also, the renal RI of the main renal artery was measured bilaterally.
      All measurements for each patient were collected and the average RI was calculated. The
      normal RI is considered when the value was <0.7. The renal Doppler was assessed within 24
      hours pre-operative and within 2-3 hours after surgery completion.

      Patient preparation. Patients who fasted for 8 hours, with full clinical and laboratory
      results, were examined for any exclusion criteria with specific concerns with regard to
      kidney function. 12 hours before the scheduled time for surgery, renal Doppler was performed
      to measure the renal RI of all patients, before starting to fast for surgery and after
      adequate hydration was checked, based on his ward fluid chart.

      Inside the operating room. The standard monitoring, including electrocardiogram (ECG), oxygen
      saturation, non-invasive blood pressure, and capnogram for end-tidal carbon dioxide (ETCO2),
      were applied. Infusion of Ringer's lactate solution (8 mL/kg) was started through a wide bore
      cannula. IV midazolam 0.05 mg/kg was given as a premedication before the induction of
      anesthesia by 2 μg/kg fentanyl, 2 mg/kg propofol, and 0.5 mg/kg atracurium. An endotracheal
      tube was inserted to initiate mechanical ventilation while keeping the ETCO2 in the range of
      35-45 mmHg. Anesthesia maintenance was performed with 1.5% isoflurane and oxygen and topped
      up with IV atracurium 0.5 mg/kg every 20 minutes. The urinary output was followed up using a
      urinary catheter. IV fentanyl dose of 1 μg/kg was administered, in response to an increase in
      blood pressure or heart rate of >20% of the baseline measurement. Continuous ECG, blood
      pressure, and pulse saturation were monitored. To ensure an adequate fluid balance, fluid
      input, fluid output (urine and third space loss), blood loss, and central venous pressure
      were recorded. The inhalational anesthetic isoflurane was discontinued at the end of the
      surgery, followed by the administration of IV neostigmine of 0.05 mg/kg and atropine of 0.02
      mg/kg, to reverse the residual neuromuscular block. The trachea was extubated after
      spontaneous breathing returned.

      Epidural analgesia. Epidural analgesia was performed before the induction of general
      anesthesia by a well-experienced anesthesiologist with at least 5 years experience in local
      and regional anesthesia. Patients were in a sitting position leaning forward with the legs
      supported on a chair. Complete skin asepsis with povidone-iodine (7.5%), was applied followed
      by draping. An 18-gauge Tuohy epidural needle was inserted into the intervertebral space
      T9-T10, using a vacuum catheter aspiration technique followed by the epidural catheter
      insertion. The epidural was activated at the end of the operation using 10 mL of 0.25%
      bupivacaine as a bolus followed by a continuous epidural infusion using 0.125% bupivacaine,
      at a rate of 6 mL/hour, to be continued for up to 24 hours postoperatively.

      QL block technique. A bilateral posterior approach, a US-guided QL block was applied after
      anesthesia induction by a well-experienced anesthesiologist with at least 5 years experience
      in local and regional anesthesia, using Honda electronics HS-2100 portable US machine (Honda
      Electronics CO., LTD, Japan). The patient was in a supine position with a pillow under his
      back. Povidone-iodine (7.5%) was used to sterilize the area above the iliac crest at the
      level of the anterior axillary line, followed by draping before the application of a
      high-frequency superficial probe (9-11 MHz). The probe was adjusted until visualization of
      the external oblique muscle, the internal oblique muscle, and the transversus abdominis
      muscle. Then the probe was moved posteriorly until the thoracolumbar fascia covering the QL
      muscle was visualized. The needle was inserted just above the upper edge of the probe and
      pierced the muscles until it reached the posterior aspect of the QL muscle. Aspiration was
      done to ensure that there is no blood and to ensure extravascular injection to avoid the
      undesirable systemic effect. The correct site was confirmed through saline injection (hydro
      dissection); 25 mL of 0.25% bupivacaine were injected on each side.

      Fluid balance was maintained throughout the operation, using a fluid chart to avoid any
      hemodynamic instability that might affect the objective of this study.

      Postoperative study parameters. Patients were transferred to the intermediate care unit, for
      continuous observation for 24 hours. A 10-point visual analog scale (VAS) was used to assess
      pain; with 0 being no pain and number 10 being the worst pain. The VAS score was assessed
      immediately after patients' transfer from the theater room (0 hours) then 2, 6, 8, 12, 18,
      and 24 hours postoperative. The following parameters were assessed by a blinded
      anesthesiologist to the aim of the study:

        -  The time required for the first morphine dose and the cumulative morphine consumption
           for 24 hours were recorded as a primary outcome. Morphine was given at a dose of 0.05
           mg/kg when the VAS score was >4.

        -  Postoperative kidney function was assessed using laboratory and US Doppler indices to
           compare it with the preoperative values, as a secondary outcome. Laboratory tests
           included serum creatinine and blood urea nitrogen (BUN) and were compared with
           preoperative values.
    

Intervention name(s): Quadratous lumborum block; Epidural anesthesia
Intervention type(s): Procedure; Procedure
Intervention description(s): Quadratus Lumborum (QL) block is a new technique for analgesia of the abdominal wall muscles. Its mechanism depends on the injection of the local anesthetic agent between the abdominal wall muscles into the thoracolumbar fascia surrounding the Quadratus Lumborum muscle by ultrasound (US) guided technique.; Epidural analgesia is a gold standard analgesic technique for the majority of abdominal surgeries, yet it has some limitations in some surgeries as colorectal surgeries due to delayed ambulation due to muscular weakness and postural hypotension.
Intervention MeSH terms: Anesthetics
Observational model: Case-Control
Time perspective: Prospective
Sampling method: Probability Sample
Study population: 
        Cases will undergo colorectal surgeries
      
Keywords: Quadratus Lumborum block; Renal resistive index; Renal doppler; Epidural anesthesia