HIPEC is hyperthermic intraperitoneal chemotherapy, a process in which heated chemotherapy is pumped into abdominal cavity after cytoreductive/ debulking surgery. Common tumours treated by HIPEC are:

*colorectal cancers
*appendix tumours
*mesotheliomas
*adrenal tumours
*ovarian tumours
*liver cancers
*pancreatic tumours

Cytoreductive Surgery – HIPEC:

Surgeon removes all visible tumours from the abdomen, followed by pumping heated chemotherapy drugs through the abdominal cavity. The surgeon rocks the patient back and forth on an operating table for 2 hours to ensure direct contact with all of the remaining cancer cells.

Alterations During HIPEC Phase:

It’s a complex surgical procedure, with the patient facing major alterations in hemodynamics, respiratory, metabolic, coagulation and thermal balance, and so perioperative management is challenging for the anaesthesiologist.

Anaesthetic Considerations During HIPEC Phase:

*Hemodynamics:

Anaesthesia is induced with general anaesthesia, with thoracic epidural analgesia and invasive lines needed for organ function monitoring. Vasodilatation caused by G/A & hyperthermia reduces cardiac preload and afterload, which is further aggravated by sympathetic blockade caused by central neuraxial blockade. HIPEC-induced hypermetabolic state causes increase in HR, CVP, cardiac index and decreases SVR & MAP.

*Respiration:

HIPEC causes increase in ETCO2, O2 consumption, and O2 extraction. Increased intra-abdominal pressure causes upward migration of diaphragm , contributing to decreased venous return and IVC collapse. Increased intrathoracic pressure further makes CVP & PCWP unreliable.

*Metabolic Changes, Blood and Fluid Loss:

Massive blood and substantial fluid loss happen during debulking surgery, coupled with ascitic drainage and continuous evaporative loss from open abdomen. Further, HIPEC causes peritoneal inflammation that can cause periop third-space loss. Fluid requirements far exceed recommended 6-8ml/kg/hr. Across reports, 12-20 ml/kg/hr are frequently observed, guided by end-organ perfusion targets. Fluid therapy was guided by hematocrit and lactate levels in ABG. Significant protein loss from raw peritoneal surface is managed by giving 20% albumin. Ensure U/O 1ml/kg/hr during cytoreductive surgery and 2ml/kg/hr during heated chemotherapy administration. Many patients need blood transfusion based on hematocrit values in ABG and component transfusions of fresh frozen plasma or platelets.

*Thermal Balance:

Thermoregulation plays a major role in maintaining metabolic homeostasis, coagulation, anti- inflammatory cascade, and intact neurological status. During the initial debulking phase, patients are at high risk of hypothermia due to large area of surgical exposure, long duration of resection, and ascitic fluid loss. Temperature is maintained using a heated water-driven underbody mattress, warm fluid infusions, and forced air warming blankets. During HIPEC, the hyperthermic instillation causes an increase in core temperature up to 40 degree C. To combat all untoward responses, normothermia has to be maintained by passive cooling by using cooled intravenous fluids, icepacks, and setting off the warming device and cooled water through an underbody mattress. If the core temperature rises to 39 degree C despite all these measures, then perfusionist is advised to reduce the instilled temperature. Upon completion of HIPEC and evacuation of hyperthermic instillatIon, the body temperature begins to normalise with time, though still remaining above baseline.

*Coagulopathy:

Patients are at high thrombotic risk due to malignancy per se and the prolonged nature of surgery. Further, ascitic fluid loss, rich in protein, primarily albumin, causes changes in oncotic pressure, thereby impairing coagulation. Intraoperative sequencial compression devices and postop DVT prophylaxis are highly recommended.

*Checklist Done 15 Minutes Prior to Initiation of HIPEC:
1. All fluid warmers switched off
2. Body warmers set to ambient temperature
3. Laboratory studies of serum electrolytes, blood gas analysis, haemoglobin, and blood sugar are done
4. Increased intravenous fluid infusion rate (1800ml/hr)
5. Antibiotics repeated
6. Ensure availability of albumin, blood, and blood products
7. Continuous temperature evaluation and urine output monitoring

*Pain Management:

Generous use of opioids intraop ( as elective postop ventilation is planned) supplemented with local anaesthetics via thoracic epidural and postop continous local anaesthetic infusions through epidural would be the ideal choice.

Conclusion:

The aneasthesiologist has to deal with relevant fluid, blood, and protein losses, raised intra abdominal pressure, thermal imbalances, and raised metabolic rate. The onus remains on maintaining and restoring integrity of milieu interior by volume infusions, component transfusions, supplementary thoracic analgesia, and patient monitoring.