After Raul Ruidiaz's 40th minute opener, the visitors had taken the lead after goals from Cristian Dajome and Lucas Cavallini.
Medranda intervened with his 71st minute strike, coming after a corner was cleared into his path, lashing home from the edge of the box.
The result means Seattle remain top in the Western Conference, having conceded only seven goals in 11 games.
It also ends Vancouver's five-game losing streak, although they remain second last in the west.
Former Manchester United striker Javier 'Chicharito' Hernandez scored a double to lift LA Galaxy to a 3-1 win away to San Jose Earthquakes.
The Mexico international opened the scoring in the 11th minute when he swept home Samuel Grandsir's dangerous cross from the right.
Hernandez produced a similar finish to double their advantage in the 50th minute, tapping home from Kevin Cabral's ball.
Galaxy are third in the Western Conference, four points behind Seattle with a game in hand.
Philadelphia Union extended their unbeaten run to eight games with a 3-3 draw away to Chicago Fire.
Toronto's struggles continued with a 2-0 home defeat to Cincinnati, condemning them to five consecutive defeats.
Sporting Kansas City defeated Los Angeles FC 2-1, Real Salt Lake and Houston Dynamo drew 1-1, Minnesota United won 1-0 at Portland Timbers and Abu Danladi netted a late leveller to help Nashville claim a 1-1 home draw with Montreal.
Johnny Russell scored a goal and assisted two others as Sporting KC routed Minnesota at Children's Mercy Park on Wednesday.
Russell converted a penalty as part of a three-goal first half, with Khiry Shelton and Daniel Salloi also on target against the visitors.
Cameron Duke added a fourth goal seven minutes into the second half as Sporting KC found the back of the net in their 28th consecutive regular-season home game dating back to August 2019 – the longest active streak in MLS.
Sporting KC are a point clear in the west, though second-placed Seattle Sounders have played two games less, while Minnesota are two points outside the play-off positions.
San Jose Earthquakes star Javier Lopez scored a hat-trick, but Real Salt Lake still prevailed 4-3 in a wild clash.
Lopez opened the scoring in the 26th minute and completed his treble in the second half, however, RSL emerged victorious thanks to Rubio Rubin's brace.
The result snapped a five-match away losing streak for RSL, who ended San Jose's run of three consecutive wins over their rivals in MLS – a run that had equalled the longest streak by either team in history.
Elsewhere, former Manchester United and Real Madrid striker Javier 'Chicharito' Hernandez salvaged a 1-1 draw for LA Galaxy against Houston Dynamo.
Another ex-United star, Nani, was sent off in the first half as Orlando City were beaten 4-2 by Montreal, Ola Kamara's opening-half hat-trick lifted DC United past Chicago Fire 3-0, Atlanta United were 4-0 winners against FC Cincinnati courtesy of a Josef Martinez double, Los Angeles FC edged Austin 2-1 and 10-man Portland Timbers drew 2-2 with Colorado Rapids.
David Beckham's Inter Miami and fellow expansion club Nashville SC will enter the league, which will increase to 26 teams.
Seattle Sounders are the defending champions, record-breaking Los Angeles FC will look to go all the way this year after falling short last term, while Arsenal and Barcelona legend Thierry Henry is at the helm of Montreal Impact.
With the season set to kick off, here is a selection of the best Opta facts related to MLS.
- Only one of the last eight teams to debut in MLS have won their inaugural match, dating back to Portland Timbers in 2011 (LAFC 1-0 Seattle in 2018). Orlando City and New York City drew against each other in both teams' inaugural match in 2015, while the other five teams that joined the league in that time lost their opening match.
- Of MLS' last nine new teams, only one have failed to score in their inaugural match in the competition. Montreal lost 2-0 to Vancouver Whitecaps in 2012.
- Of the 14 teams to play their inaugural MLS match on the road, only two have managed to win; including Los Angeles in 2018 (also Chicago Fire in 1998, at Miami Fusion). Two more managed draws while 10 of the 14 teams that started on the road lost their inaugural match.
- The last six MLS expansion clubs scored in their first away match in the league dating back to 2015. Five of the teams scored one goal while Atlanta United scored six against fellow newcomers Minnesota United in 2017.
- The last three reigning MLS Cup winners lost the opening match of the following season, including Seattle's 2-1 defeat at Houston Dynamo in 2017 after reigning supreme in 2016.
- LAFC equalled the all-time record for goals scored in a single MLS season last campaign (85 – level with LA Galaxy in 1998). Their striker Carlos Vela also broke the record for single-season goals in MLS history; scoring 34 and beating Josef Martinez's record haul of 31 from 2018.
- Atlanta star Martinez has scored a goal against all 23 of the opposition teams that he has faced in regular-season MLS matches – Nashville will be the 24th different opponent he has played against in the competition.
- New York City's 177 points and 50 wins are both second-most over the past three MLS regular campaigns, both behind Atlanta (182 points and 54 wins). NYC are the only team that have won at least 16 regular-season matches in each of the past three MLS campaigns.
- Last season was the 10th straight in which New York Red Bulls qualified for the MLS postseason. The Red Bulls' 10 successive play-off appearance represent the second-longest active run (Seattle – 11) and the longest in the history of the Eastern Conference.
- New Impact manager Henry took charge of Monaco in Ligue 1 last season between October 2018 and January 2019. During his 12 league games in charge, he won just twice (17 per cent); which was the worst win ratio of every Monaco head coach to take charge of five-plus top-flight games in their history.
- Colorado Rapids have missed the play-offs in three successive MLS seasons for the first time since 2007-2009. They have collected just 106 points over the past three MLS campaigns, only Orlando City (104) have collected fewer among the teams that have been in the league for each season since 2017.
- 85 of LA Galaxy recruit Javier Hernandez's 89 goals within the big five European leagues during his career came from inside the box (96 per cent), including each of the past 30 of these strikes.
NYRB had to hold in final stages after leading by three goals at one stage, with goals from Sebastian Driussi and Ethan Finlay bringing Austin back in the contest, but Gerhard Struber's side deservedly took the win to keep up with Philadelphia Union and New York City.
First-half goals from Serge Ngoma and Dru Yearwood had the visitors up 2-1 at the interval after Driussi's first of the night, but Yearwood then set up Cameron Harper, who deftly cut inside Ruben Gabrielsen and finished to make it 3-1 after 51 minutes.
Substitute Tom Barlow made it 4-1 14 minutes later with a thumping finish on the half-volley straight from Carlos Coronel's goal-kick.
Following Union and City's wins on Saturday, NYRB restored their gap to the Eastern Conference's top two to five points with the win and joined Austin in earning the most wins on the road this season, with seven.
Los Angeles Galaxy marginally moved back into the Western Conference's playoff spots in Sunday's later game, defeating Atlanta United 2-0.
Needing the three points after losing their previous three games, the Galaxy hit the lead in only the seventh minute through Kevin Cabral.
They sought to absorb pressure in the second half with only 35.7 per cent possession, before substitute Dejan Joveljic eventually scored the sealer on the break in added time.
Greg Vanney's side moved into seventh in the Western Conference with the win, leapfrogging Portland Timbers despitte both being on 30 points, having secured two more wins.
RSL moved above Portland Timbers into the last playoffs spot in the Western Conference with their 3-1 victory, while Orlando achieved the same feat in the east after beating Columbus Crew 2-1 after a late penalty.
Pablo Mastroeni's RSL will take on two seed Austin in the first round of the MLS playoffs, navigating their way past Portland who started the day in sixth spot, but dropped to eighth, with Minnesota United also qualifying with their 2-0 win over Vancouver Whitecaps.
Jefferson Savarino settled any nerves for RSL, who had claimed only three wins from their past 17 games, by curling in a 19th-minute opener before Rubio Rubin's deflected shot doubled their lead in the 48th minute.
Bode Hidalgo sealed RSL's playoffs spot with a classy finish in the 82nd minute, with Dairon Asprilla scoring a late consolation for the Timbers.
Minnesota, who will take on Dallas in the first round of the playoffs, got their win after Franco Fragapane's low 17th-minute drive. Jonathon Gonzalez added a second with a left-foot volley in the 77th minute to seal the Loons' spot.
Hany Mukhtar was confirmed as the MLS Golden Boot winner with 23 goals, although he did not score as Nashville locked in the five seed with a 1-0 win over Supporters Shield winners LAFC.
Teal Bunbury scored the only goal in the 53rd minute, with Nashville to face LA Galaxy in the playoffs. Galaxy beat Houston Dynamo 3-1 with Riqui Puig and Javier Hernandez among the scorers.
Facundo Torres converted an 84th-minute spot kick to send Orlando into the playoffs with a 2-1 victory over the Crew. The Lions will take on Eastern Conference two seed Montreal.
Columbus came into the game one point ahead of Orlando and had gone ahead through Derick Etienne in the 38th minute.
Junior Urso leveled for Orlando in the 56th minute before Milos Degenek's handball led to Torres' decisive penalty, condemning the Crew to missing the playoffs.
Cincinnati clinched their spot in the playoffs for the first time in franchise history, leapfrogging up into the five seed slot, with their 5-2 win at struggling DC United.
Brenner hit a hat-trick for Cincy, who will take on New York Red Bulls in the playoffs. The Red Bulls won 2-0 over Charlotte after Elias Manoel's double to secure the four seed.
Inter Miami lost 3-1 at home to Montreal, meaning Phil Neville's side slipped to the six seed and will take on reigning MLS Cup champions New York City. City beat Atlanta United 2-1 to clinch the three seed.
In other games, Seattle Sounders and San Jose Earthquakes drew 2-2, Chicago Fire drew 1-1 with New England and Austin and Colorado Rapids ended 1-1 after Diego Rubio's late equalizer for the visitors.
Eastern Conference winners Philadelphia Union thrashed Toronto 4-0 with Daniel Gazdag netting a hat-trick, while Western Conference three seed Dallas got past Sporting KC 2-1.
Lewis Morgan, who scored 14 goals in the regular season, had put the Red Bulls ahead with a rifled strike from outside the box in the 48th minute at Red Bull Arena.
But Cincinnati replied with two goals in the final 15 minutes to secure their spot in the Conference Semifinals where they will face top seed Philadelphia Union. Fourth-year franchise Cincy had finished last in the Eastern Conference during its previous three campaigns.
Cincy thought they had an equalizer in the 60th minute when the Red Bulls failed to clear a long throw and Junior Moreno's strike was deflected in, but that was by an offside Jeff Cameron.
But the visitors found an avenue back when Red Bulls defender Andres Reyes clumsily brought down Alvaro Barreal, with Luciano Acosta stepping up to send Carlos Coronel the wrong way with the 74th-minute penalty.
New York were stunned when Cincy took the lead with less than five minutes of regulation time left as Vasquez sidefooted home substitute Sergio Santos' left-flank pass.
Cincy goalkeeper Roman Celentano denied Aaron Long's 88th-minute header, while Red Bulls defender Sean Nealis headed over in stoppage time.
LA Galaxy moved into the Conference Semifinals where they will face LAFC after a 1-0 home victory over Nashville at Dignity Health Sports Park.
The hosts thought they had gone ahead in the 50th minute when they raced forward in a four-on-two situation with Riqui Puig laying off for Javier Hernandez to fire home but the goal was disallowed on review after a Ronald Araujo foul in the build-up.
Pink-haired Araujo, who hit the post with a wayward 60th-minute cross, made amends when he headed in Samuel Grandsir's cross from the byline on the right side.
Galaxy could have added another but Nashville goalkeeper Joe Willis made saves from Riqui Puig and Kevin Cabral late.
Nashville had gone ahead in the 28th minute from Hany Mukhtar's penalty but Hernandez was the centre of attention once again.
The former Manchester United forward failed to convert a 97th-minute penalty attempting a Panenka last Sunday against Sporting KC, spurning a hat-trick and winner.
Hernandez stepped up again in the 55th minute after being bundled over by Shaquell Moore but had his low shot tipped around the post by goalkeeper Joel Willis.
With their season on the line, the Galaxy earned a late reprieve after a penalty was awarded for a Walker Zimmerman handball following VAR review, with the defender receiving a second yellow card.
But Riqui Puig grabbed the ball and took the responsibility instead of Hernandez, before firing just beyond Willis' fingertips for the goal.
The result means the Galaxy are winless in three games and sit eighth in the Western Conference on 40 points.
Western Conference leaders LAFC stumbled again, suffering their fourth loss in their past five games with a 2-1 defeat to Dallas.
Jesus Ferreira boosted his claims on a spot in USA's World Cup squad with a double for Dallas, while LAFC were reduced to 10 men after Ryan Hollingshead's 13th-minute red card.
Eastern Conference leaders Philadelphia Union showed why they are arguably the best team in the MLS with a 5-1 thrashing of Orlando City securing their fifth straight victory.
Lewis Morgan scored a 78th-minute penalty to help New York Red Bulls secure a 2-1 home win over New England to firm up their grip on third in the east.
New York City suffered their seventh defeat from their past nine games, going down 1-0 to Charlotte.
Brenner scored a hat-trick as Cincinnati extended their unbeaten run to nine games, winning 6-0 over San Jose Earthquakes
Thiago Almada fired in a golazo as Atlanta United defeated Toronto 4-2, while Inter Miami slumped to a third straight loss with a 3-1 defeat at Chicago Fire.
Seattle Sounders toppled Austin 3-0, Houston Dynamo and Sporting KC drew 0-0, Portland Timbers edged Minnesota United 1-0, Colorado Rapids beat Vancouver Whitecaps 3-1 and Real Salt Lake and DC United ended goalless.
LA's Oniel Fisher brought down Cristian Roldan in the penalty area in the 49th minute and Ruidiaz beat goalkeeper Jonathan Bond with a Panenka on the spot kick.
That equaliser put Seattle back on top of the Western Conference table on 59 points, one ahead of Sporting Kansas City and Colorado Rapids, while the Galaxy moved up a spot to sixth with the point.
LA had taken the lead in the 19th minute on Javier 'Chicharito' Hernandez's 15th goal of the season, the Mexican star flicking the ball past Stefan Frei with the outside of his right foot.
Jordan Morris took the pitch for Seattle for the first time since injuring his knee February 20 while on loan to Swansea City.
The United States international came on for Ruidiaz in the 60th minute to get in some match time as he looks ahead to the MLS play-offs.
Seattle travel to Vancouver Whitecaps on Sunday in the final match of the MLS regular season, while the Galaxy host Minnesota United.
