AIMS AND OBJECTIVES

Aim:

To compare the effect of intermittent pneumatic leg compression on post induction hypotension in adult patients undergoing sub axial cervical spine surgeries

Primary objective:

To compare the incidence of post induction hypotension in patients undergoing “Sub-axial cervical spine surgery” between the pneumatic and control groups

Secondary objectives:

1. To compare the following parameters among the groups

 Number of hypotensive episodes during surgery

 Use of vasopressors and, intravenous fluids etc. in first 20 minute and thereafter during surgery.

 Prone positioning related hypotensive events will be recorded and compared. 

 Arterial blood gas changes between the baseline, 20 minutes post induction and at the end of the surgery in terms of base deficit, lactate and p/f ratio.

2. To observe the incidence of complications/side effects of the use of pneumatic compression device

Statistical Analysis

In the study conducted by Prajith, et al, in which 90 term obstetric patients posted for elective caesarean section under spinal anaesthesia were included and analysed, pneumatic compression resulted in a lower incidence of post induction hypotension than the control; 26.6% vs 66.7%.

Based on the above assumption, with type I error ()= 0.05, type II error ()= 0.1 and power of the study to be 0.9 and the enrollment ratio 1:1, the sample size in each group would be 31.

Attributing 10% to attrition, the final sample size will be a total of 68 patients with 34 in each group.

Data will be described in terms of range; mean ±standard deviation (± SD), median (IQR), frequencies (number of cases) and relative frequencies (percentages) as appropriate. To determine whether the data is normally distributed, a Kolmogorov-Smirnov test will be used. Comparison of quantitative variables between the study groups will be done using Student t-test and Mann Whitney U test for independent samples for parametric and non-parametric data respectively. For comparing categorical data, Chi square (χ2) test will be performed and fisher exact test will be used when the expected frequency is less than 5. A probability value (p value) less than 0.05 will be considered statistically significant. All statistical calculations will be done using (Statistical Package for the Social Science) SPSS 21version (SPSS Inc., Chicago, IL, USA) statistical program for Microsoft Windows.

MATERIALS AND METHODS

Study place: Trauma OR & recovery wards, PGIMER

Study time: After ethical approval and CTRI registration July 2024 to July 2025

Study participants: Adult patients undergoing sub axial cervical spine surgeries under general anesthesia fulfilling the following criteria are eligible

Inclusion criteria:

Patients of 18-65 years of age

Single level sub-axial cervical spine fracture-dislocation with neural deficit

ASA I to ASA II physiological status

Patients with no contraindication to leg compression

Exclusion criteria:

Patient refusal, Inability to give informed consent

Hemodynamically unstable (requiring vasopressor in preoperative phase) and/or patients in spinal shock

Unstable angina, poor LV function (<0.40)

H/o arrhythmia requiring treatment

Uncontrolled HTN, DM, Coronary artery disease etc.

Patients with contraindication to leg compression such as history of DVT or peripheral arterial disease

 Study protocol:

Approval will be obtained from the institutional ethics committee (IEC), PGIMER, Chandigarh. CTRI registration will be obtained. A written informed consent will be taken from all the patients prior to enrolment in the trial.

Randomization:

Patients will be randomized by a computer-generated number using sealed envelope technique to following two groups with 1:1 allocation

Group PC: Pneumatic compression device will be installed and used prior to induction of anaesthesia

Group NC: Pneumatic compression device will be installed but not used

 Blinding:

Single blind study (as the investigator will be blinded to group allocation)

In a single centre, prospective, randomized, controlled trial to be conducted in the Department of Anaesthesia and Intensive care, PGIMER, Chandigarh, incidence of ‘post induction hypotension’ in the first 20 minutes after induction in the patients undergoing sub-axial cervical spine surgery will be compared in between the pneumatic and control groups.

After clearance of ethical committee and CTRI registration, all the eligible patients will undergo the following:

Pre-operative evaluation:

All patients will undergo pre-anesthetic Checkup. The standard preoperative fasting guidelines will be followed in all patients. Along with demographic data (Name, Age, Gender, BMI), diagnosis, comorbidities, ASA physical status, baseline hemodynamics, patients will be classified according to ASIA Impairment Scale. The patients then will be randomized into one of the two groups. A preliminary echocardiography will be done by the investigator to ascertain the left ventricular ejection fraction of the patient using the Mitral Valve EPSS method (Appendix I). Using the phased array probe, minimum diameter of the IVC on inspiration and maximum diameter of the IVC on expiration will be recorded and collapsibility index will be calculated to assess the fluid status of the patient. (Appendix II)

Pre-induction:

Nil per oral status will be confirmed prior to shifting the patient inside the operation theater. After shifting to the OT table, ASA standard monitors (Electrocardiography, NIBP and pulse oximetry) will be attached along with BIS and NMT monitors. A 18G/16G cannula will be secured for administering IV fluids and drugs. Local anesthetic will be infiltrated into either forearm above the radial artery and will be cannulated with a 20G arterial cannula for monitoring the invasive arterial blood pressure. The pneumatic compression device will be attached. In all patients of PC Group, the pneumatic compression device will be installed and activated before induction of anesthesia. With a continuous mode timer and a set pressure of 50 mmHg, pneumatic leg compression with progressive sequential compression will be performed, providing 36 seconds of inflation and 24 seconds of deflation throughout the surgery. While in the control group, the pneumatic compression will not be used.

 The baseline vitals of the patient will be recorded prior to induction.

 Induction:

Patient will be induced using intravenous Fentanyl 1.5mcg/kg, Propofol, titrated to a BIS value of 40-60 and 0.6 mg/kg rocuronium as muscle relaxant. Once the TOF count reaches 0, airway will be secured by an endotracheal tube of appropriate size via direct, video or fibreoptic laryngoscopy depending on the nature of the airway. An arterial blood sample will be taken for ABG analysis just after induction.

Maintenance:

After intubation patient will be maintained on total intravenous anaesthesia using Propofol and a 50:50 mixture of oxygen and air. The infusion rate of propofol will be guided by BIS value, kept at 40-60. Continuous etCO₂ monitoring will be done after intubation by capnography. Mechanical ventilation of the lungs will be performed using a tidal volume of 6–8 ml/kg (ideal body weight) and a respiratory rate of 10–16 per min to maintain an end-tidal carbon dioxide of 30–35 mmHg. A positive end-expiratory pressure of 5 cmH2O will be applied. To maintain adequate muscle relaxation, Rocuronium 0.1mg/kg IV will be administered after the TOF count reaches 2. The rate of IV fluid infusion will be determined by the Pulse Pressure Variation (PPV), Systolic Pressure Variation (SPV) and urine output. The goal will be to keep the PPV <15%, SPV<12% and urine output >0.5ml/kg/hr. Perioperative haemodynamic parameters will be maintained within 20% from their base line throughout the surgery. Esmolol will be used at a loading dose of 500mcg/kg IV over one minute if hypertension and tachycardia persist beyond 20% of their base line values. An arterial blood sample will be sent for ABG analysis after 20 mins post induction. Intraoperative maximum allowable blood loss will be calculated by the standard method and blood loss will be replaced with crystalloids, colloids or whole blood as needed, as the intraoperative blood loss crosses the maximum allowable volume. Normal body temperature will be maintained with the use of forced air warmer and warm IV fluids. All patients will receive 15 mg/kg acetaminophen and 4 mg ondansetron IV at the end of the surgery.

Rescue intervention for arterial hypotension (SBP<90mmHg) will be administration of fluid bolus (250ml) followed by use of mephentermine 3mg/ phenylephrine 50mcg IV bolus in incremental doses. Hypotension persisting for more than 5 minutes after the above interventions will be managed by infusion of Noradrenaline 0.05mcg/kg/min and tritiated according to the response.

At the end of the procedure:

After the end of the surgery, an arterial blood sample will sent for ABG analysis. All inhalational/ intravenous aesthetic agents will be discontinued. Once the TOF count reaches 4, neuromuscular blockade will be reversed by Neostigmine 50-70mcg/kg and Glycopyrrolate 10mcg/kg. Patient will be extubated after achieving a TOF ratio of ³ 0.9, adequate return of muscle power and the ability to follow commands. The pneumatic compression device will be removed and the patient will be evaluated for the signs of complications of its use. AIS score will be evaluated 30 minutes after the patient is shifted to recovery. AIS score of the patients that are not extubated on the table will be assessed one day post extubation.

Data collection:

Preoperative:

Demographic data (Name, Age, Gender, BMI), Diagnosis, Comorbidities, ASA score, Baseline hemodynamics, AIS scoring, LVEF and volume status via IVC diameter and collapsibility mesurement.

Intraoperative:

SBP <90 mmHg at any time point in first 20 mins after induction or anytime during surgery.

Any use of mephentermine/phenylephrine or vasopressors in first 20 mins or anytime during surgery.

ABG just after induction, at 20 mins and at end of surgery.

Minimum SBP (mmHg) , maximum HR , % of patients with PIH, % of patients with hypotension after 20 min of induction,  number of hypotensive events requiring vasopressor/mephentermine, number of bradycardia events requiring atropine.