Modified Surgical Apgar Score for predicting the postoperative outcome following infratentorial tumour surgery– A prospective observational cohort study.

Patients undergoing posterior fossa tumour surgery are prone to blood pressure (BP) and heart rate (HR) changes (haemodynamic variation) such as hypertension, hypotension, bradycardia or tachycardia, arrhythmias due to dissection of tumour from vital structures such as the brainstem, and cranial nerves especially 5th (sympathetic response) and 10th (parasympathetic) cranial nerves. Traction on the tumour during the cerebellopontine angle tumour resection, excision of brainstem tumour and tumour excision arising from cranial nerves (5th cranial nerve) can cause haemodynamic changes due to traction on the brainstem which can later lead to brainstem oedema, contusion or haematoma. All these can worsen the neurological outcome and can cause mortality. Cranial nerve manipulation and injuries cause either transient or permanent neurological deficits, which increases postoperative morbidity and mortality.

The Surgical Apgar score (SAS) is a score derived from intraoperative BP and HR changes and blood loss that has been validated to predict early postoperative outcomes in the general surgical and vascular surgical population. We are planning to modify the Surgical Apgar score and see whether the modified score predicts the early postoperative outcome, which includes morbidity and mortality in an adult patient undergoing a posterior fossa craniotomy and excision of the infratentorial tumour. (Both SAS and Modified Surgical Apgar score (MSAS) are explained below) Intraoperatively, the haemodynamics (HR and Blood pressure) from the time of induction of anaesthesia to extubation or the time of transfer to NICU (in cases where elective ventilation is planned) will be recorded. These parameters will be taken from the anaesthesia monitors, where the data is stored automatically every minute.

The intraoperative period will be divided into 4 phases, phase 1-Pretumour resection- this is taken from the time of induction to dural opening. Phase 2- tumour resection –is the time period taken from the time of start to completion of tumour excision/beginning of achieving hemostasis, Phase 3- Hemostasis and surgical closure – which include the time from completion of hemostasis to skull pin removal (this is the phase anaesthesiologist will bring up the blood pressure to baseline using vasopressor such as phenylephrine or ephedrine or increasing the dose of noradrenaline dose), Phase 4 – extubation – after the removal of skull pin to extubation. Haemodynamic changes during Phase 2 and Phase 4 can increase perioperative morbidity and mortality. The minimum and maximum heart rate and minimum and maximum mean blood pressure (MBP) will be recorded during these four phases of surgery, and we will calculate the Modified Surgical Apgar score for each of the 4 phases, we will also calculate the Modified Surgical Apgar Score combining all the four phases. (From induction to extubation). Haemodynamics (Heart rate and blood pressure) will be recorded in the datasheet by the attending anaesthesiologist. At the end of each phase, stored data f