PVB Versus TAP in Hepatic Patients Undergoing Laparoscopic Cholecystectomy

Study design:

Prospective randomized clinical study, sixty patients will be randomly allocated to one of two groups according to a computer-generated random number table of 30 patients each to receive ultrasound-guided either TAP block (Group T) or PVB (Group P).

Study setting and location Theodor Bilharz research institute.

Study population:

60 patients (ASA II or III ) undergoing laparoscopic cholecystectomy under general anesthesia will be recruited and will be randomly allocated using a computer-generated random number table of 30 patients each to receive either:

1. Paravertebral block group or
2. Transverse abdominis muscle block group.

Study Procedures

Methodology in details :

Anesthesia technique:

Preoperative :

• During the pre-operative period visual analog scale (VAS) for pain assessment from 0 to 10, with 0 meaning no pain and 10 meaning the worst pain imaginable will be explained to patients.
• Midazolam 0.05 mg/kg will be given as pre-medication upon arrival to the operating room then 500 ml lactated Ringer's solution will be administered slowly iv as a pre-load

Monitoring :

ECG, pulse oximetry, noninvasive blood pressure, gas analyzer, bispectral index (BIS), and TOF-Guard module for neuromuscular monitoring (Dragger Infinity Kappa version VF-5W, Germany) are connected to the participants.

Induction and maintenance

• During mask pre-oxygenation, patients' baseline hemo-dynamic parameters will be recorded regarding blood pressure and heart rate.
• General anesthesia will be standardized for all patients with :

1.5- 2 µg / kg fentanyl, 2-2.5 mg/kg 2% propofol then 0.5 mg/kg atracuriam will be administered for muscle relaxation.

• Patients will be intubated and lungs mechanically ventilated to maintain end-tidal CO2 between 30 to 35 mmHg. Fresh gas flow oxygen in air 30-40% at a rate of 3 L/min for 10 minutes will be administered then decreased to 1L/min using a closed system (Fabius GS, Dräger, Lübeck, Germany).
• The patients will receive 1 MAC desflurane which is defined as an expired fraction of 6.0 vol. %. Then the dial-up percentage will be adjusted to establish a BIS value between 40- 50.
• Top- up doses of 0.15 mg/kg atracurium will be given to maintain intra-operative muscle relaxation according to TOF-guard.
• All surgical procedures will be done in the range between 10 am and 2 pm and by the same surgical team.
• Patients will be randomly allocated to one of the 2 groups :

1. In group P, USG-TPVB will be performed with the patient is in sitting position, a linear transducer (6-15 MHz) placed just lateral to the spinous process, the depth of field will be set about 3 cm to start scanning. The transverse processes and ribs will be visualized as hyper echoic structures with acoustic shadowing below them. Once the transverse processes and ribs are identified, the transducer is moved slightly cauded into the intercostal space between adjacent ribs to identify the thoracic para-vertebral space (PVS) and the adjoining intercostal space. The PVS appears as a wedge-shaped hypo echoic layer demarcated by the hyper echoic reflections of the pleura below and the internal intercostal membrane above. It is important to visualize the pleura very clearly at all times. The hyper echoic line of the pleura and underlying hyper echoic air artifacts move with respiration. The needle stimuplex needle (BRAUN Stimuplec D Plus 0,71*50- 80 mm 22 G* 2'', 15°) will be inserted and 0.5 - 1 ml local anesthetic injection administered to show the displacement of pleura downward followed by 15 cc bupivacaine 0.25% Marcaine® flacon, Astra Zeneca, Sweden) into each side the PVS. Visualization of the needle and its tip and controlling its path at all times are essential to avoid inadvertent pleural puncture or entry into the intervertebral foramen. A pop often is felt as the needle penetrates the internal intercostal membrane. Intra-vascular injection will be eliminated by negative aspiration before injection. Local anesthetic (15- 20 ml) is slowly injected in small increments, avoiding forceful high-pressure injection to reduce the risk of bilateral epidural spread.

II. In group T, USG-TAP Subcostal blockage will be done in plane technique with 22 G needle (BRAUN Stimuplex D Plus 0,71 50- 80 mm 22 G). The puncture area and the ultrasound probe will be prepared in an aseptic manner. The ultrasound probe is placed in a transverse plane to the lateral abdominal wall in the midaxillary line, between the lower costal margin and iliac crest. On each side, The rectus abdominis and underlying transverses abdominis muscles near the costal margin and xiphoid process will be identified. In-plane image will be obtained and the needle will be inserted through the rectus muscle 2-3 cm medial to the probe. Once the tip of the needle is visualized to be in the plane, 0.25% bupivacaine will be administered incrementally. The drug will be injected along the oblique subcostal line, extending inferolaterally from the xiphoid towards the anterior part of the iliac crest by multiple punctures; a total of 15 ml will be given on each side.

• When heart rate and blood pressure exceeds 20% of baseline in spite of adequate level of anesthesia guided by BIS, boluses of 0.5 µg/kg fentanyl will be given \& the total fentanyl dose will be recorded.
• Atropine 0.5 mg increments will be used to control bradycardia (<50 beat min-1) while hypotension (less than 20% of preanesthetic level) will be managed by increasing fluid infusion rate, decreasing inhalational anesthetic concentration and ephedrine 5 mg.
• Reversal of neuromuscular blockade will be achieved by IV administration of neostigmine 0.05 mg kg-1 and atropine 0.02 mg kg-1.
• Patients will be extubated and transferred to post- anesthetic care unit.

Collected parameters:

Before the operation:

• Age, weight, height, sex, ASA, medical history as well as physical examination will be documented.
• Viral hepatitis markers and liver ultrasonography will be done to verify liver affection.
• The Child-Turcotte-Pugh (CTP) classification including preoperative serum albumin, serum bilirubin, ascites, prothrombin time (PT), or INR (modified CTP score), and grade of encephalopathy will be reported.
• Liver functions AST, ALT and ALP will be taken preoperatively, immediately postoperatively and 24 hours later to rule out any change in liver functions.
• Regarding hemodynamic parameters blood pressure and heart rate will be monitored in each group prior and following the block, induction of general anesthesia as well as endotracheal intubation, then every 10 min till end of the operation.
• The total amount of fentanyl consumption throughout operation will be taken.
• Total anesthetic consumption will also be calculated according to the following formula (18):

Total liquid (ml) = from t=0 to t=end dt The time from the start of end-tidal control (t=0) until the time when the vaporizer will be switched off at the end (t=end).

A conversion factor is detected from the amount of vapor given from each ml of volatile liquid: conversion factor of desflurane is 209 ml calculated from the following formula:

Conversion factor = [density of volatile liquid (g/ml) ×volume at room temperature and pressure (24000 ml)] /molecular weight (g).

Total volatile values used will be calculated by summing the product of usage rate by the duration of each time epoch.

Average volatile usage (ml/h) =

Postoperatively:

• Pain intensity will be estimated by a numeric rating scale (NRS) (0 = no pain, 10 = worst imaginable pain) at rest and on coughing at 2, 4, 6 and 24 hours following the end of surgery. When VAS is exceeding four, boluses of 5 mg intravenous pethidine were given till VAS declined to be less than 4.
• Time to first analgesic demand as well as total analgesic requirements will be recorded.
• Any complications regarding the procedure or the block will be noted as intraperitoneal injection, bowel hematoma and transient nerve palsy as well as Local anesthetic toxicity.
• Length of hospital stay.
• Total amount of analgesia (paracetamol).